BG2

EDI
Tropical ecosystems – biomes of global significance in transition

Tropical ecosystems are biomes of global significance due to their large biodiversity, carbon storage capacity, and their role in the hydrological cycle. Historic and recent human activities have, however, resulted in intensive transformation of the tropical ecosystems in the Amazon, Central America, Central Africa and in South East Asia impacting the cycling of nutrient, carbon, water, and energy. Understanding their current functioning at process up to biome level in its pristine and transformed state is elemental for predicting their response upon changing climate and land use, and the impact this will have on local up to global scale.
This session aims at bringing together scientists who investigate the functioning of the tropical ecosystems across spatial and temporal scales by means of remote and in-situ observational, modelling, and theoretical studies. Particularly welcome are presentations of novel, interdisciplinary approaches and techniques.

solicited authors:
Co-organized by AS2/HS10/SSS8
Convener: Jošt Valentin Lavrič | Co-conveners: Alexander Knohl, Julia Drewer, Laynara F. LugliECSECS, Carlos Alberto Quesada, Matthias Sörgel, Hans Verbeeck
vPICO presentations
| Mon, 26 Apr, 13:30–15:00 (CEST)

vPICO presentations: Mon, 26 Apr

Chairpersons: Laynara F. Lugli, Julia Drewer
The Amazon – a biome of global significance in transition
13:30–13:32
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EGU21-11283
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Highlight
Luiz A. T. Machado, Mira Pöhlker, Paulo Artaxo, Micael Cecchini, Florian Ditas, Marco A. M. Franco, Leslie Kremper, Meinrat O. Andreae, Ivan Saraiva, Ulrich Pöschl, and Christopher Pöhlker

In the last years, several studies were published evaluating aerosol-cloud-precipitation interactions. These studies improved the knowledge and reduced the uncertainties in the quantification of the aerosol aerosol-cloud interactions. However, there were only very few attempts to describe how clouds modify the aerosol properties. The main goal of this study is to evaluate the effect of weather events on the Particle Size Distribution (PSD) at the Amazon Tall Tower Observatory (ATTO). This research combines different types of datasets, all co-located at the ATTO towers. Basically, the data were obtained from the new generation of GOES satellites, GOES-16, the SIPAM S Band radar and two Scanning Mobility Particle Sizers (SMPS) installed at the heights of 60 and 325 m from 2017 to 2020. In addition, the LAP 3000 radar wind profile recently installed at the ATTO- Campina site was employed to evaluate the vertical distribution of the vertical velocity. The combination of these datasets allows to explore changes in PSD due to the different meteorological processes. The diurnal cycle shows an increase of nucleation particles and decrease in Aitken and accumulation modes during the night. The early morning is the time of minimum mass concentration. From the early morning to the middle of the afternoon, a contrary behaviour is observed, where the concentration of nucleation particles decreases and Aitken and accumulation mode increase, characterizing a typical particle growth process. In the late afternoon, when rain starts, PSD begin to have the night behaviour described above. Composite studies were computed to evaluate how the PSD evolve during rainfall events. The composite from lighting density shows a large increase in nucleation particles from around 100 minutes before the maximum lighting density, reaching maximum values nearly 200 minutes later. The nucleation particles growth rate increases exponentially with the thunderstorm intensity. Aitken and accumulation modes have a different behaviour, with decreasing number concentration from around 100 minutes before the maximum lighting activity and reaching the minimum concentration at the time of maximum lighting activity. This effect could be related to the more intense downdraft in thunderstorms that intensify the transport of ultrafine particles from the upper atmosphere as described in recent studies using GoAmazon and ACRIDICON-CHUVA data. Another possibility could be the transport of O3 and NO2 column densities during thunderstorms events, helping the oxidation of volatile organic component forming secondary organic aerosol at the surface. This is an open question and needs further studies specifically designed to understand the chemical processes occurring near-surface during intense rainfall events. The first data from the radar wind profile installed at the ATTO-Campina site was employed to compute the vertical distribution of the vertical velocity. The downdrafts are mainly located below 10km, but the layer of maximum concentration of ultrafine particles is mainly above 10km. In addition, the number concentration of nucleation particles at 60m is around twice the value at 325 m, in contrast to former studies showing an increase in ultrafine particles with height. CAFE-Brazil, scheduled for 2022, will be an opportunity to study these open questions.

How to cite: T. Machado, L. A., Pöhlker, M., Artaxo, P., Cecchini, M., Ditas, F., M. Franco, M. A., Kremper, L., Andreae, M. O., Saraiva, I., Pöschl, U., and Pöhlker, C.: How Weather Events Modify Amazonian Surface Aerosol Particle Size Distributions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11283, https://doi.org/10.5194/egusphere-egu21-11283, 2021.

13:32–13:34
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EGU21-12971
Luca Mortarini, Cléo Quaresma Dias-Júnior, Otavio Acevedo, Pablo Oliveira, Daiane Brondani, Umberto Giostra, Matthias Sörgel, Anywhere Tsokankunku, Alessandro Araújo, Luiz Augusto Toledo Machado, and Daniela Cava

This study provides a detailed analysis of the influence of atmospheric stratification on the flow dynamics above and within a dense forest for a 19-days campaign at the Amazon Tall Tower Observatory (ATTO) site. Observations taken at seven levels within and above the forest along an 81-meter and a 325-meter towers allow a unique investigation of the vertical evolution of the turbulent field in the roughness sublayer and in the surface layer above it.

Five different stability classes were defined on the basis of the behavior of turbulent heat, momentum and CO2 fluxes and variance ratio as a function of h/L stability parameter (where h is the canopy height and L is the Obukhov length). The novelty is the identification of a ‘super-stable’ (SS) regime (h/L>3) characterized by extremely low wind speeds, the almost completely suppression of turbulence and a clear dominance of submeso motions both above and within the forest.

The obtained data classification was used to study the influence of atmospheric stratification on the vertical profiles of turbulent statistics. The spectral characteristics of coherent structures and of submeso motions (that may influence the energy and mass exchange above the Amazon forest) have been analyzed by wavelet analyses. The role of the main structures in momentum, heat and CO2 transport at the different levels inside and above the forest and in different diabatic conditions was thoroughly investigated through multiresolution and quadrant analyses.

In unstable and neutral stability, the flow above the canopy appears modulated by ejections, whereas downward and intermittent sweeps dominate the transport inside the canopy. In the roughness sublayer (z £ 2h) the coherent structures dominating the transport within and above the canopy have a characteristic temporal scale of about 100 sec, whereas above this layer the transport is mainly driven by larger scale convection (temporal scale of about 15 min).

In stable conditions the height of roughness sublayer progressively decreases with increasing stability reaching the minimum value (z<1.35h) in the SS regime. Above the canopy the flow is clearly dominated by ejections but characterized by a higher intermittency mainly in SS conditions. On the other hand, the rapid shear stress absorption in the highest part of the vegetation produces a less clear dominance of sweeps and a less defined role of odd and even quadrants inside the canopy in the transport of momentum, heat and CO2. In the weakly stable regime (0.15<h/L<1) transport is dominated in the roughness sublayer by canopy coherent structures with a characteristic temporal scale of about 60 sec. As stability increases the influence of low-frequency (submeso) processes, with a temporal scale of 20-30 min, on flow dynamics progressively increases and becomes dominant in the SS regime where the buoyancy strongly dampens or completely inhibits turbulent structures whereas the large-scale oscillations propagate in the interior of the canopy modulating the heat and CO2 transport.

 

How to cite: Mortarini, L., Quaresma Dias-Júnior, C., Acevedo, O., Oliveira, P., Brondani, D., Giostra, U., Sörgel, M., Tsokankunku, A., Araújo, A., Toledo Machado, L. A., and Cava, D.: Influence of Atmospheric Stability on the flow dynamics within and above a dense Amazonian forest, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12971, https://doi.org/10.5194/egusphere-egu21-12971, 2021.

13:34–13:36
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EGU21-961
Tianning Zhao, Jianhuai Ye, Igor Ribeiro, Yongjing Ma, Hui-Ming Hung, Carla Batista, Matthew Stewart, Jessica dos Santos Silva, Ricardo Godoi, Jordi Vilà-Guerau de Arellano, Rodrigo de Souza, and Scot Martin

Local atmospheric circulation induced by wide rivers in Amazonia can strongly affect the transport of urban, industrial, fire, and forest emissions. Herein, a copter-type unmanned aerial vehicle (UAV) operated from a boat was used to collect vertical profiles of meteorological parameters and chemical concentrations during Sep-Oct 2019 of the dry season. Sensor packages mounted on the UAV measured wind speed and direction together with concentrations of carbon monoxide (CO) and total oxidants (Ox, defined as O3 + NO2). Multivariate statistical analysis identified distinguishing patterns for meteorological variables. The occurrence of river breeze circulations was linked to meteorological conditions from in-situ measurement and satellite images. Vertical profiles of chemical concentrations both from in-situ measurements and large eddy simulations confirmed that under some conditions a river breeze can facilitate pollutant mixing perpendicular to the river orientation. The results of this study advance an urgent need to quantify the occurrence and the properties of river breeze circulations in respect to microscale chemical dispersion, air quality, and human health.

How to cite: Zhao, T., Ye, J., Ribeiro, I., Ma, Y., Hung, H.-M., Batista, C., Stewart, M., dos Santos Silva, J., Godoi, R., Vilà-Guerau de Arellano, J., de Souza, R., and Martin, S.: River Breezes in the Central Amazon: Cluster Analysis of Meteorological and Chemical Data Sets Collected by an Unmanned Aerial Vehicle, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-961, https://doi.org/10.5194/egusphere-egu21-961, 2021.

13:36–13:38
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EGU21-12869
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ECS
Xabier Pedruzo-Bagazgoitia, Arnold F. Moene, Huug Ouwersloot, Tobias Gerken, Luiz A.T. Machado, Scot T. Martin, Edward G. Patton, Matthias Sörgel, Paul C. Stoy, Marcia A. Yamasoe, and Jordi Vilà-Guerau de Arellano

The vegetated canopy plays a key role in regulating the surface fluxes and, therefore, the global energy, water and carbon cycles. In particular, vulnerable ecosystems like the Amazonia basin can be very sensitive to changes in vegetation that exert subsequent shifts in the partition of the energy, water and carbon in and above the canopy. Despite this relevance, most 3D atmospheric models represent the vegetated canopy as a flat 2D layer with, at most, a rough imitation of its effect in the atmospheric boundary layer through a modified roughness length. Thus, the representations often describe quite crudely the surface fluxes. In this work, particular emphasis is placed in the biophysical processes that take place within the canopy and its impact above. Our approach is to represent the coupling of the flow between the canopy and the atmosphere including the following processes: radiative transfer, photosynthesis, soil evaporation and CO2 respiration, combined with the mostly explicit atmospheric turbulence within and above the canopy. To this end, we implemented in LES a detailed multi-layer canopy model that solves the leaf energy balance for sunlit and shaded leaves independently, regulating the exchange of heat, moisture and carbon between the leaves and the air around. This allows us to connect the mechanistically represented processes occurring at the leaf level and strongly regulated by the transfer of diffuse and direct radiation within the canopy to the turbulent mixing explicitly resolved at the meter scale.

We test and validate this combined photosynthesis-turbulence-canopy model by simulating a representative clear day transitioning to shallow cumulus. We based our evaluation on observations by the GoAmazon2014/5 campaign in Brazil in 2014. More specifically, we systematically validate the in-canopy radiation profiles; sources, sinks and turbulent fluxes of moisture, heat and CO2, and main state variables within the canopy, and also study the effects of these in the air above. Preliminary results show an encouraging satisfactory match to the observed evolution of the profiles. As a first exploration and demonstration of the capabilities of the model, we test the effects of a coarser in-canopy resolution, a different radiation scheme and the use of a more simple 2D canopy representation.

How to cite: Pedruzo-Bagazgoitia, X., Moene, A. F., Ouwersloot, H., Gerken, T., Machado, L. A. T., Martin, S. T., Patton, E. G., Sörgel, M., Stoy, P. C., Yamasoe, M. A., and Vilà-Guerau de Arellano, J.: Understanding in and above canopy-atmosphere interactions by combining large-eddy simulations with a comprehensive observational set, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12869, https://doi.org/10.5194/egusphere-egu21-12869, 2021.

13:38–13:40
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EGU21-15847
Stefan Wolff, David Walter, Anywhere Tsokankunku, Daiane Brondani, Fernando Rossato, Sam Jones, Sebastian Brill, Eva Pfannerstill, Achim Edtbauer, Rodrigo Souza, Marta de Oliveira Sá, Alessandro C. de Araújo, Cléo Q. Dias-Júnior, Christopher Pöhlker, and Matthias Sörgel

The pristine Amazon rainforest is a unique place to study ozone (O3) deposition rates and tropospheric transport, due to the absence of nearby sources of anthropogenic pollution. Parts of the low background O3 are considered to be transported from the stratosphere into the troposphere. This occurs due to general entrainment of stratospheric air at the tropopause. Within the troposphere, downdrafts provide effective vertical mixing and are known to increase surface O3 values. Low-level jets can also enhance O3 concentrations due to long range transport and locally induced mixing in the nocturnal boundary layer. Therefore, we study these phenomena based on long term datasets from 2012 to present from tall measurements towers (80 m and 325 m).

Ozone mixing ratios were measured at the ATTO site (Amazon Tall Tower Observatory) in the Central Amazon (02°08’38.8’’S, 58°59’59.5’’W) since 2012 at 8 different heights between 5 cm and 80 meters and additional measurements from 80 m up to 325 meters are running since 2017. From 2015 to 2017, 3-dimensional wind measurements have been performed in 150 meters height in 10 Hz sampling rate, showing evidences for the formation of a nocturnal low-level jet (LLJ), which leads to higher turbulent mixing inside the residual layer/ stable nocturnal layer. We were comparing the nocturnal LLJ with downdrafts of air due to strong thunderstorms which led to increases of O3 as well. We are analyzing these events regarding their in-canopy air exchange, their frequency and seasonality and comparing them with the effects of the nocturnal LLJ. As the data series comprises more than eight years of data we are also analyzing the interannual variability.

How to cite: Wolff, S., Walter, D., Tsokankunku, A., Brondani, D., Rossato, F., Jones, S., Brill, S., Pfannerstill, E., Edtbauer, A., Souza, R., de Oliveira Sá, M., de Araújo, A. C., Dias-Júnior, C. Q., Pöhlker, C., and Sörgel, M.: The Amazonian Low-Level Jet and its effect on Ozone concentrations above the rain forest, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15847, https://doi.org/10.5194/egusphere-egu21-15847, 2021.

13:40–13:42
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EGU21-13468
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ECS
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Highlight
Hella van Asperen, Thorsten Warneke, Alessandro C De Araújo, Bruce Forsberg, Leonardo Ramos de Oliveira, Thiago de Lima Xavier, Marta Sá, Paulo Teixeira, Robson Azevedo de Oliveira, Leila Leal, Veber Moura, João Rafael Alves-Oliveira, Santiago Botia, Jost Lavrič, Shujiro Komiya, Arnoud Frumau, Arjan Hensen, Danielle van Dinther, Pim van den Bulk, and Justus Notholt

Methane (CH4) is one of the most important anthropogenic greenhouse gases.  Despite its importance, natural sources of methane, such as tropical wetlands and termites, are still not well understood and a large source of uncertainty in the tropical CH4 budget. The Amazon rainforest is a key region for the (global) CH4 budget but, due to its remote location, continous CH4 concentration and flux measurements are still rare.

The 50 m high K34 tower (field site ZF2) is located in a pristine ‘Terra Firme’ tropical forest region 60 km northwest of Manaus (Brazil), and is located next to a waterlogged valley, a possible location for anaerobic CH4 production. In October 2018, in addition to the existing EC CO2 system, an in-situ FTIR-analyzer (measuring CO2, CO, CH4, N2O and δ13CO2) was set up to measure tower profile concentrations, above and below the canopy, continuously. By analyses of vertical and temporal nighttime concentrations patterns, an emission estimate for all gases could be made, and an ecosystem emission of ~1 nmol CH4 m-2 s-1  was estimated. In addition, by use of different types of flux chambers, possible  CH4 sinks and sources such as soils, trees, water and termite mounds were measured.

By combining tower and flux chamber measurements, the role and magnitude of different ecosystem sources could be assessed. In this presentation, an overview of the measured CH4 forest concentrations and fluxes will be given.

How to cite: van Asperen, H., Warneke, T., C De Araújo, A., Forsberg, B., Ramos de Oliveira, L., de Lima Xavier, T., Sá, M., Teixeira, P., Azevedo de Oliveira, R., Leal, L., Moura, V., Rafael Alves-Oliveira, J., Botia, S., Lavrič, J., Komiya, S., Frumau, A., Hensen, A., van Dinther, D., van den Bulk, P., and Notholt, J.: Tropical forest CH4: from termite mounds to tower  measurements, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13468, https://doi.org/10.5194/egusphere-egu21-13468, 2021.

13:42–13:44
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EGU21-831
Kristell Hergoualc’h, Nelda Dezzeo, Louis Verchot, Christopher Martius, Jeffrey van Lent, Jhon Del Aguila Pasquel, and Mariela Lopez

Mauritia flexuosa palm swamp, the prevailing Peruvian Amazon peatland ecosystem, is

extensively threatened by degradation. The unsustainable practice of cutting whole

palms for fruit extraction modifies forest's structure and composition and eventually

alters peat-derived greenhouse gas (GHG) emissions. We evaluated the spatio-temporal

variability of soil N2O and CH4 fluxes and environmental controls along a palm swamp

degradation gradient formed by one undegraded site (Intact), one moderately degraded

site (mDeg) and one heavily degraded site (hDeg). Microscale variability differentiated

hummocks supporting live or cut palms from surrounding hollows. Macroscale analysis

considered structural changes in vegetation and soil microtopography as impacted

by degradation. Variables were monitored monthly over 3 years to evaluate intra- and

inter-annual variability. Degradation induced microscale changes in N2O and CH4 emission

trends and controls. Site-scale average annual CH4 emissions were similar along the

degradation gradient (225.6 ± 50.7, 160.5 ± 65.9 and 169.4 ± 20.7 kg C ha−1 year−1 at

the Intact, mDeg and hDeg sites, respectively). Site-scale average annual N2O emissions

(kg N ha−1 year−1) were lower at the mDeg site (0.5 ± 0.1) than at the Intact (1.3 ± 0.6) and

hDeg sites (1.1 ± 0.4), but the difference seemed linked to heterogeneous fluctuations

in soil water-filled pore space (WFPS) along the forest complex rather than to degradation.

Monthly and annual emissions were mainly controlled by variations in WFPS, water

table level (WT) and net nitrification for N2O; WT, air temperature and net nitrification

for CH4. Site-scale N2O emissions remained steady over years, whereas CH4 emissions

rose exponentially with increased precipitation. While the minor impact of degradation

on palm swamp peatland N2O and CH4 fluxes should be tested elsewhere, the evidenced

large and variable CH4 emissions and significant N2O emissions call for improved modeling

of GHG dynamics in tropical peatlands to test their response to climate changes.

How to cite: Hergoualc’h, K., Dezzeo, N., Verchot, L., Martius, C., van Lent, J., Del Aguila Pasquel, J., and Lopez, M.: Spatial and temporal variability of soil N2O and CH4 fluxes along a degradation gradient in a palm swamp peat forest in the Peruvian Amazon, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-831, https://doi.org/10.5194/egusphere-egu21-831, 2021.

13:44–13:46
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EGU21-13194
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ECS
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Highlight
Laura Vedovato, Lidiany Carvalho, Luiz Aragão, and Ted Feldpausch

During extreme drought events, aboveground biomass (AGB) dynamics in Amazonian forests are altered through reduced productivity and increased tree mortality and carbon loss. Tree adaptations developed in response to historical drought may reduce the severity of carbon loss. Past droughts were likely associated with fire, which produced Pyrogenic Carbon (PyC), a form of carbon formed by the incomplete combustion of biomass burn and fossil fuel. PyC has specific properties that improve soil fertility and water holding capacity and decrease aluminium toxicity, among others. PyC can be found in different concentrations across the Amazon Basin, since it can be produced by local fires and aerosol deposition. It is unknown whether PyC could explain tree adaptations or contributes to Amazon forest dynamics, especially for extreme drought events. We hypothesize that PyC in soil can serve as a proxy of fire history and fire/drought adaptations and also support the forest during drought events because of its properties, decreasing mortality rates and maintaining rates of AGB gain equivalent to a non-extreme drought year. To evaluate this hypothesis, we used a dataset with more than 70 plots with repeat censuses distributed across the Amazon Basin and classified extreme drought events using maximum cumulative water deficit (MCWD) analysis. Soil samples were collected from the same plots during an intensive fieldwork campaign and PyC was quantified by hydrogen pyrolysis (HyPy). Forest plots were classified into high and low PyC based on the median across the whole dataset. Our preliminary results show that during extreme drought events, plots that have a greater concentration of PyC had significantly higher rates of AGB gain when compared with plots with lower concentrations of PyC (t-test, p < 0.05). During non-extreme drought years there was no significant difference in rates of AGB gain between plots with different concentrations of PyC. When we focus on plots with lower concentrations of PyC there is a significant decrease in rates of AGB gain during drought years compared to non-extreme drought years (t-test, p < 0.05). However, in plots with high concentrations of PyC there is no significant difference in rates of AGB gain, showing trees are able to maintain normal forest dynamics during extreme drought years. We conclude that PyC has an important role in mediating drought resistance and productivity in Amazonian forests.

How to cite: Vedovato, L., Carvalho, L., Aragão, L., and Feldpausch, T.: Pyrogenic carbon and forest dynamics during drought in Amazonian forests, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13194, https://doi.org/10.5194/egusphere-egu21-13194, 2021.

13:46–13:48
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EGU21-7956
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ECS
Viola Heinrich, Ricardo Dalagnol, Henrique Cassol, Thais Rosan, Catherine Torres de Almeida, Celso Silva Junior, Welsey Campanharo, Joanna House, Stephen Sitch, Tristram Hales, Marcos Adami, Liana Anderson, and Luiz Aragão

Overall, global forests are expected to contribute about a quarter of pledged mitigation under the Paris Agreement, by limiting deforestation and by encouraging forest regrowth.

Secondary Forests in the Neo-tropics have a large climate mitigation potential, given their ability to sequester carbon up to 20 times faster than old-growth forests. However, this rate does not account for the spatial patterns in secondary forest regrowth influenced by regional and local-scale environmental and anthropogenic disturbance drivers.

Secondary Forests in the Brazilian Amazon are expected to play a key role in achieving the goals of the Paris Agreement, however, the Amazon is a large and geographically complex region such that regrowth rates are not uniform across the biome.

To understand the impact of key drivers we used a multi-satellite data approach with the aim of understanding the spatial variations in secondary forest regrowth in the Brazilian Amazon. We mapped secondary forest area and age using a land-use-land-cover dataset – MapBiomas – and, combined with the European Space Agency Aboveground Carbon dataset, constructed regional regrowth curves for the year 2017.

We found large variations in the regrowth rates across the Brazilian Amazon due to large-scale environmental drivers such as rainfall and shortwave-radiation. Regrowth rates are similar to previous pan-Amazonian estimates in the North-West (3 ±1.0 MgC ha-1 yr-1), which are double than those in the North-East Amazon (1.3 ±0.3 MgC ha-1 yr-1). The impact of anthropogenic disturbances, namely fire and repeated deforestation prior to the most recent regrowth only reduces the regrowth by 20% in the North-West (2.4 ±0.8 MgC ha-1 yr-1) compared to 55% in the North-East (0.8 ±0.8 MgC ha-1 yr-1). Overall, secondary forest carbon stock of 294 TgC in the year 2017, could have been 8% higher with avoided fires and repeat deforestation. We found that the 2017 area of secondary forest, which occupies only ~4% of the Brazilian Amazon biome, can contribute significantly (~5.5%) to Brazil’s net emissions reduction targets, accumulating ~19.0 TgC yr-1until 2030 if the current area of secondary forest is maintained (13.8 Mha). However,this value reduces rapidly to less than 1% if only secondary forests older than 20 years are preserved (2.2 Mha).

Preserving the remaining old-growth forest carbon stock and implementing legal mechanisms to protect and expand secondary forest areas are key to realising the potential of secondary forest as a nature-based climate change mitigation solution.

How to cite: Heinrich, V., Dalagnol, R., Cassol, H., Rosan, T., Torres de Almeida, C., Silva Junior, C., Campanharo, W., House, J., Sitch, S., Hales, T., Adami, M., Anderson, L., and Aragão, L.: Quantifying the spatial patterns of Secondary Forest carbon sequestration potential in the Brazilian Amazon, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7956, https://doi.org/10.5194/egusphere-egu21-7956, 2021.

13:48–13:50
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EGU21-14109
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ECS
Sebastian Brill, Nina Löbs, Cybelli G. G. Barbosa, Juliana F. de Camargo, David Walter, Florian Ditas, Marta de Oliveira Sá, Alessandro C. de Araújo, Leonardo R. de Oliveira, Ricardo H. M. Godoi, Stefan Wolff, Meike Piepenbring, Jürgen Kesselmeier, Paulo Artaxo, Meinrat O. Andreae, Ulrich Pöschl, Christopher Pöhlker, and Bettina Weber

Primary biological aerosol particles (PBAP), better known as bioaerosols, are considered to play a role in atmospheric and climate influencing processes. Fungal spores, as a part of PBAP, account for a large fraction of coarse particulate matter in some ecosystems, as for example the Amazon rainforest. In such highly diverse ecosystems, fungi play key roles as mycorrhizal fungi for nutrient uptake of plants and as decomposers in nutrient and water cycling, and thus their community structure strongly influences local ecosystem conditions. Despite this relevance, fungal spore emission patterns under natural conditions and the corresponding triggering factors are not well characterized, yet. In this study, we present a laboratory and field measurement techniques to quantify and analyze bioaerosol emission patterns and the effect of precipitation on fungal spore emission.

For investigations under field conditions, the particle emissions of fungi (Agaricomycetes) were characterized at their site of growth in the field using an optical particle sizer and a data logger. Particle concentrations and their size distribution (0.3 to 10 µm), as well as the microclimatic temperature and humidity were measured in close vicinity to the fungal fruiting body. Generally, field measurements were performed over a time span of 24 h with some exceptions ranging up to 6 days. For laboratory measurements, a newly developed glass chamber system was used to measure particle emissions of fungi under controlled conditions. During the chamber measurements, the humidity and temperature conditions were varied and recorded with a datalogger. To simulate precipitation events, the fruiting bodies were sprayed with water between measurement sections and particle emissions were monitored before and after moistening.

First measurements of fungi under field and lab conditions showed that high humidity values were necessary to trigger fungal spore emissions. In many cases, precipitation events and the moisture status of the fungus and substrate had an influence on spore release. Based on the results of 47 field measurements, it was possible to establish a function simulating the spore emission patterns of fungi during their diurnal emission cycle. During field measurements, an emission of up to 55,000 spores per second was recorded directly at the fungus, which, according to the function, may correspond to emissions of up to 2.8 x 109 spores per day. Chamber measurements showed that spore emissions generally started 2-3 hours after artificial moistening.

Increasing deforestation is expected to cause drier conditions and to increase the possibility of droughts, which will have an impact on the species composition and quantity of fungi in the Amazon. A combination of our field and lab emission data is expected to allow a new interpretation of bioaerosol emissions and composition in the Amazon, which can be used as a baseline to analyze the potential relevance of bioaerosols in regional atmosphere and climate processes.

How to cite: Brill, S., Löbs, N., Barbosa, C. G. G., de Camargo, J. F., Walter, D., Ditas, F., de Oliveira Sá, M., de Araújo, A. C., de Oliveira, L. R., Godoi, R. H. M., Wolff, S., Piepenbring, M., Kesselmeier, J., Artaxo, P., Andreae, M. O., Pöschl, U., Pöhlker, C., and Weber, B.: Analysis of bioaerosol emission patterns of tropical fungi in the Amazon region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14109, https://doi.org/10.5194/egusphere-egu21-14109, 2021.

13:50–13:52
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EGU21-8739
David Lapola, Gilvan Sampaio, Marília Shimizu, Carlos Guimarães-Júnior, Felipe Alexandre, Manoel Cardoso, Tomas Domingues, Anja Rammig, Celso von Randow, and Luiz Rezende

Amazon region’s climate is particularly sensitive to surface processes and properties such as heat fluxes and vegetation coverage. Rainfall is a key expression of such land surface-atmosphere interactions in the region due to its strong dependence on forest transpiration. While a large number of past studies have shown the impacts of large-scale deforestation on annual rainfall, studies on the isolated effects of elevated atmospheric CO2 concentration (eCO2) on plant physiology (i.e. the β effect), for example on canopy transpiration and rainfall, are scarcer. Here we make a systematic comparison of the plant physiological effects of eCO2 and deforestation on Amazon rainfall. We use the CPTEC-Brazilian Atmospheric Model (BAM) with dynamic vegetation under a 1.5xCO2 and a 100% substitution of the forest by pasture grassland, with all other conditions held similar between the two scenarios. We find that both scenarios result in equivalent average annual rainfall reductions (Physiology: -252 mm,-12%; Deforestation: -292 mm, -13%) that are well above observed Amazon rainfall interannual variability of 5.1%. Rainfall decrease in the two scenarios are caused by a reduction of approximately 20% of canopy transpiration, but for different reasons: eCO2-driven reduction of stomatal conductance in the Physiology run; decreased leaf area index of pasture (-66%) and its dry-season lower surface vegetation coverage in the Deforestation run. Walker circulation is strengthened in the two scenarios (with enhanced convection over the Andes and a weak subsidence branch over east Amazon) but, again, through different mechanisms: enhanced west winds from the Pacific and reduced easterlies entering the basin in Physiology, and strongly increased easterlies in Deforestation. Although our results for the Deforestation scenario are in agreement with previous observational and modelling studies, the lack of direct field-based ecosystem-level experimental evidence on the effect of eCO2 in moisture fluxes of tropical forests confers a substantial level of uncertainty to this and any other projections on the physiological effect of eCO2 on Amazon rainfall. Furthermore, our results denote the incurred responsibilities of both Amazonian and non- Amazonian countries to mitigate potential future climatic change and its impacts in the region driven either by local deforestation (to be tackled by Amazonian countries) or global CO2 emissions (to be handled by all countries).

How to cite: Lapola, D., Sampaio, G., Shimizu, M., Guimarães-Júnior, C., Alexandre, F., Cardoso, M., Domingues, T., Rammig, A., von Randow, C., and Rezende, L.: Beta effect of eCO2 can cause as much rainfall decrease as large-scale deforestation in the Amazon, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8739, https://doi.org/10.5194/egusphere-egu21-8739, 2021.

Biogeochemistry, ecohydrology, and land-use in the tropics
13:52–13:54
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EGU21-8937
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ECS
Santiago Valencia, Juan Camilo Villegas, and Juan F. Salazar

Forest - savanna transition is the most widespread and perhaps more dynamic ecotone in the tropics, and extremely sensitive to climate and environmental change. Both kinds of tropical ecosystems are globally strategic and their presence and dynamics have important ecological, climatic and biogeochemical implications, even at the global scale. However, the processes and mechanisms that control this transition vary among regions and remain not fully understood. In general, this transition is influenced by multiple interactions between vegetation and environmental factors such as climate, soil properties, fire, and herbivory. However, the magnitude of these effects can vary substantially across continents, which can result in different responses to environmental change. For this reason, more regional studies are needed to describe and understand the factors and interactions that control forest - savanna transition, particularly in Northern South America, where climate alone has failed to explain this transition. Based on a combination of LiDAR and satellite-derived data, we developed a statistical analysis on the interactive effects of rainfall, soil properties, and fire on the forest - savanna transition in Northern South America, in the savanna region between Colombia and Venezuela, using tree cover as an indicator variable that differentiates forest from savanna. Specifically, we analyze the relationships of tree cover (from GEDI) with soil sand content (from SoilGrids), fire frequency (from Fire_CCI v5.1) as well as three rainfall variability components (from CHIRPS): mean dry-season rainfall, length of the dry season, and frequency of rainy days within the dry season. Our results show that tree cover increased with mean dry-season rainfall and frequency of rainy days within the dry season, whereas it decreased with increased fire frequency. In particular, mean dry-season rainfall followed by fire frequency are the most important predictors of tree cover gradient in the transition. Importantly, our results also suggest that areas with high annual rainfall (2000 to 2800 mm) have low tree cover (i.e. savanna) if the local rainfall climatology consists of infrequent (< 0.35) and low total rainfall (< 650 mm) in the dry season. This highlights the role of water availability and fire disturbance in determining the limits between forest and the second largest area of savanna in South America. Further, our results support that future projections for forest - savanna transition should include not only changes in mean annual rainfall but also changes in rainfall variability, which is expected to be more impacted by climate change. 

How to cite: Valencia, S., Villegas, J. C., and Salazar, J. F.: Analysis of determinants of forest - savanna transition in the northern South America, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8937, https://doi.org/10.5194/egusphere-egu21-8937, 2021.

13:54–13:56
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EGU21-4121
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ECS
Marlon Calispa, Raphaël van Ypersele, Benoît Pereira, Sebastián Páez-Bimos, Veerle Vanacker, Marcos Villacís, Armando Molina, Bert de Bièvre, Teresa Muñoz, and Pierre Delmelle

The Ecuadorian páramo, a neotropical ecosystem located in the upper Andes, acts as a constant source of high-quality water. It also stores significant amounts of C at the regional scale. In this region, volcanic ash soils sustain most of the paramo, and C storage results partly from their propensity to accumulate organic matter. Vegetation type is known to influence the balance between plant C inputs and soil C losses, ultimately affecting the soil organic C (SOC) content and stock. Tussock-forming grass (spp. Calamagrostis Intermedia; TU), cushion-like plants (spp. Azorella pedunculata; CU) and shrubs and trees (Polylepis stands) are commonly found in the páramo. Our understanding of SOC stocks and dynamics in the páramo remains limited, despite mounting concerns that human activities are increasingly affecting vegetation and potentially, the capacity of these ecosystems to store C.

Here, we compare the organic C content and stock in soils under tussock-forming grass (spp. Calamagrostis Intermedia; TU) and soils under cushion-like plants (spp. Azorella pedunculata; CU). The study took place at Jatunhuayco, a watershed on the western slopes of Antisana volcano in the northern Ecuadorian Andes. Two areas of similar size (~0.35 km2) were surveyed. Fourty soil samples were collected randomly in each area to depths varying from 10 to 30 cm (A horizon) and from 30 to 75 cm (2Ab horizon). The soils are Vitric Andosols and the 2Ab horizon corresponds to a soil buried by the tephra fall from the Quilotoa eruption about 800 yr. BP. Sixteen intact soil samples were collected in Kopecky's cylinders for bulk density (BD) determination of each horizon.

The average SOC content in the A horizon of the CU sites (9.4±0.5%) is significantly higher (Mann-Whitney U test, p<0.05) than that of the TU sites (8.0±0.4%), probably reflecting a larger input of root biomass from the cushion-forming plants. The 2Ab horizon contains less organic C (i.e. TU: 4.3±0.3% and CU: 4.0±0.4%) than the A horizon, but the SOC contents are undistinguishable between the two vegetation types. This suggests that the influence of vegetation type on SOC is limited to the A horizon. The average SOC stocks (in the first 30 cm from the soil) for TU and CU are 20.04±1.1 and 18.23±1.0 kg/m2,respectively. These values are almost two times greater than the global average reported for Vitric Andosols (~8.2 kg/m2 ), but are lower than the estimates obtained for some wetter Andean páramos (22.5±5 kg/m2, 270% higher rainfall) from Ecuador. Our stock values further indicate that vegetation type has a limited effect on C storage in the young volcanic ash soils found at Jatunhuyaco. Despite a higher SOC content, the CU soils store a stock of organic C similar to that estimated for the TU soils. This likely reflects the comparatively lower BD of the former soils (650±100 vs. 840±30 kg/m3). Additional studies are needed in order to establish the vegetation-related factors driving the SOC content and stability in the TU and CU soils.

How to cite: Calispa, M., van Ypersele, R., Pereira, B., Páez-Bimos, S., Vanacker, V., Villacís, M., Molina, A., de Bièvre, B., Muñoz, T., and Delmelle, P.: Soil organic carbon stocks under different páramo vegetation covers in Ecuador’s northern Andes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4121, https://doi.org/10.5194/egusphere-egu21-4121, 2021.

13:56–13:58
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EGU21-13301
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ECS
Inês Vieira, Hans Verbeeck, Félicien Meunier, Marc Peaucelle, Lodewijk Lefevre, Alexander Cheesman, Stephen Sitch, José Mbifo, Pascal Boeckx, and Marijn Bauters

Tropospheric ozone is a greenhouse gas, and high tropospheric ozone levels can directly impact plant growth and human health. In the Congo basin, simulations predict high ozone concentrations, induced by high ozone precursor (VOC and NOx) concentrations and high solar irradiation, which trigger the chemical reactions that form ozone. Additionally, biomass burning activities are widespread on the African continent, playing a crucial role in ozone precursor production. How these potentially high ozone levels impact tropical forest primary productivity remains poorly understood, and field-based ozone monitoring is completely lacking from the Congo basin. This study intends to show preliminary results from the first full year of in situ measurements of ozone concentration in the Congo Basin (i.e., Yangambi, Democratic Republic of the Congo). We show the relationships between meteorological variables (temperature, precipitation, radiation, wind direction and speed), fire occurrence (derived from remote sensing products) and ozone concentrations at a new continuous monitoring station in the heart of the Congo Basin. First results show higher daily mean ozone levels (e.g. 43 ppb registered in January 2020) during dry season months (December-February). We identify a strong diurnal cycle, where minimum values of ozone (almost near zero) are registered during night hours, and maximum values (near 100 ppb) are registered during the daytime. We also verify that around 2.5% of the ozone measurements exceeds a toxicity level (potential for ozone to damage vegetation) of 40 ppb. In the longer term, these measurements should improve the accuracy of future model simulations in the Congo Basin and will be used to assess the impact of ozone on the tropical forest’s primary productivity.

How to cite: Vieira, I., Verbeeck, H., Meunier, F., Peaucelle, M., Lefevre, L., Cheesman, A., Sitch, S., Mbifo, J., Boeckx, P., and Bauters, M.: Meteorological and fire impacts on tropospheric ozone concentration over tropical forest in the Congo Basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13301, https://doi.org/10.5194/egusphere-egu21-13301, 2021.

13:58–14:00
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EGU21-7704
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ECS
Stella White, Ribka Sionita Tarigan, Anak Agung Ketut Aryawan, Edgar Turner, Sarah Luke, Pujianto Pujianto, Jean-Pierre Caliman, and Julia Drewer

Oil palm (OP) growers are under pressure to reduce their environmental impact. Ecosystem function and biodiversity are at the forefront of the issue, but what effect do changes in management practices have on greenhouse gas (GHG) fluxes from plantations? 

The Riparian Ecosystem Restoration in Tropical Agriculture (RERTA) Project is a collaboration between the University of Cambridge and the SMART Research Institute in Riau, Indonesia. This project explores the ecological changes resulting from the restoration of riparian margins between plantations and watercourses. Four management strategies were applied on both sides of a river to create 50m riparian buffers, 400m in length: (1) A control treatment of no restoration, the removal of mature OP and replanting of young OP to the river margin; (2) Little to no agricultural management of mature OP; (3) Clearance of mature OP and enrichment planting with native forest trees; (4) Little or no agricultural management of mature OP and enrichment planting with native forest trees. Here we present a specific objective to investigate the effect of riparian restoration – and related changes in soil characteristics, structure and vegetation cover – on fluxes of N2O, CH4 and CO2 from mineral soils.

The experimental site began as a mature OP plantation, with monthly background measurements taken between January and April 2019. Palms were felled in April 2019 and monthly sampling was resumed when replanting and restoration began, in October 2019. We measured GHGs using static chambers; 6 in each riparian treatment and 16 in the actual OP plantation, 40 chambers in total. Samples were analysed using GC-FID/µECD.

Background measurements before felling showed high variability, but indicated no difference between the four experimental plots and the rest of the plantation. Fluxes measured following replanting were also highly variable, with no significant differences observed between treatments. N2O fluxes were relatively low before felling as the mature palms were no longer fertilised. Higher emissions were seen in the disturbed immature OP and forest tree treatments following replanting. Though the sites appeared to recover quickly and emission fluxes decreased after a few months, presumably as the soil settled and new vegetation began to grow. CH4 uptake was seen in the immature OP treatment immediately after replanting. In subsequent months no clear trends of CH4 uptake or emission were observed, with the greatest variability generally seen in the forest tree treatment. CH4 emissions increased in October 2020 with the beginning of the rainy season, most notably in mature OP and mature OP with forest tree treatments. Following restoration CO2 emissions were higher in treatments with established plant communities – mature OP and mature OP with forest trees.

These results suggest that riparian restoration had no significant effect on GHG fluxes from mineral soils, and would not alter the overall GHG budget of a plantation. If there is no additional GHG burden and riparian restoration results in enhancing biodiversity and ecosystem services as well as improving water quality, it will be a viable management option to improve the environmental impact of an OP plantation.

How to cite: White, S., Sionita Tarigan, R., Ketut Aryawan, A. A., Turner, E., Luke, S., Pujianto, P., Caliman, J.-P., and Drewer, J.: Greenhouse gas fluxes from an oil palm plantation on mineral soil in Indonesia undergoing riparian restoration , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7704, https://doi.org/10.5194/egusphere-egu21-7704, 2021.

14:00–14:02
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EGU21-15996
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Highlight
Ana Meijide, Cristina de la Rúa, Martin Ehbrecht, and Alexander Röll

Oil palm (Elaeis guineensis) is the most important oil crop in the world, with more than 85% of the global production coming from Indonesia and Malaysia. However, knowledge of country-wide past, current and likely future greenhouse gas (GHG) footprints from palm oil production remains largely incomplete. Over the past year, first studies reporting measurements of net ecosystem carbon dioxide (CO2) fluxes in oil palm plantations of different ages and on different soil types became available. Combining the recent CO2 flux estimates with existing measurements on methane and nitrous oxide fluxes allows for a refined quantification of the GHG footprint of palm oil production over the whole plantation life cycle.

To derive country-wide GHG emissions from palm oil production for both Indonesia and Malaysia, we applied the refined GHG footprint estimates to oil palm area extents. Therein, we differentiated between mineral and peat soils, second- and first-generation plantations and within the latter category also among previous land-use systems from which conversion to oil palm likely occurred. For deriving the current (2020) proportions for each category, we combined FAO data with existing remotely sensed maps on oil palm extent and tree density as well as peatland and intact forest layers. These area proportions were then applied to available historic (1970 – 2010) and future (2030 – 2050) oil palm extent estimates as a business-as-usual scenario (BAU), complemented by alternative scenarios. GHG footprint estimates comprise all GHG emissions from palm oil production, i.e. from land-use change, cultivation, milling and use.

Our refined approach estimates the 2020 GHG emissions from palm oil production at 1011 Tg CO2-eq. yr-1 for Indonesia and at 261 Tg CO2-eq. yr-1 for Malaysia. Our results show that while plantations on peatland only represented 17% and 15% of the total plantation area in 2020 for Indonesia and Malaysia, they accounted for 73% and 72% of the total GHG emissions from palm oil production. Emissions in 1980 and 2000 were estimated to be only 1% and 14% of the 2020 palm oil emissions for Indonesia, but already 24% and 96% for Malaysia due to the earlier oil palm expansion. Projected emissions for 2050, assuming further oil palm expansion on suitable land and constant yields from 2020 on, represent 64% of the 2020 value for Indonesia and 97% for Malaysia under a BAU expansion scenario. These lower or constant GHG emissions for future scenarios despite assumed increases in cultivated area are the consequence of lower GHG emissions in second and subsequent rotation cycles. For both countries, the 2050 BAU emissions could be reduced by more than 50% by halting all conversion of peatlands and forests to oil palm from 2020 on, and by more than 75% when additionally restoring all peatlands currently under oil palm to forest until 2050. Closing yield gaps could potentially lead to further emissions savings.   

How to cite: Meijide, A., de la Rúa, C., Ehbrecht, M., and Röll, A.: Refined past, current and future greenhouse gas footprints of palm oil production, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15996, https://doi.org/10.5194/egusphere-egu21-15996, 2021.

14:02–14:04
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EGU21-10765
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ECS
Nicoló Camarretta, Martin Ehbrecht, Arne Wenzel, Mohd Zuhdi, Miryam S. Merk, Michael Schlund, Alexander Knohl, and Stefan Erasmi

Accurate characterization of land use and land cover (LULC) is important in a rapidly changing environment such as the Indonesian tropics. Over the past 30 years, native tropical forests have been cleared and replaced by fast-growing cash-crops, such as oil palm and rubber plantations. This change in land use dramatically alters the vegetation structure of the entire region. Vegetation structural complexity is highly variable in tropical forests, and provides habitat to a large number of native species. In addition, vegetation structure has an impact on micro-climate and the exchange of greenhouse gases (GHG), water and energy. Measuring vegetation structure in the field can be costly and time consuming, particularly in remote, inaccessible areas of tropical forest. In contrast, Airborne Laser Scanning (ALS) can provide very detailed three-dimensional information on forest structure without the need to reach remote areas in the field. Here, we aim to study the potential of ALS-derived measures of structural complexity as ecological indicators to highlight differences in forest structure across a gradient of LULC in Sumatra, Indonesia. We analysed the structural complexity of four main LULC types relevant to the region: tropical secondary forests, rubber agroforests, oil palm plantations and shrublands. Several structural metrics have been extracted from ALS data over 136 circular 0.1 ha plots (34 plots per LULC type): top height, height percentiles, rumple index, leaf area index (LAI), effective number of layers (ENL), vegetation cover, number of gaps. Results from a Principal Component Analysis (PCA) indicated number of gaps to be a major driver associated with the occurrence of oil palm plantations, while higher values of key structural metrics, such as top height, LAI and ENL were strongly linked with the presence of secondary tropical forest plots. Furthermore, a clear separation in metrics behaviour between forest and oil palm plots was evident from the pairwise comparison of these metrics, with rubber and shrubland plots behaving similarly to either forests or oil palm plantings according to different metrics. Our results show clear distinctions in several structural attributes among different LULC, which indicate the need for careful considerations regarding the impact of land-use change on ecosystem functioning, biodiversity and climate.

How to cite: Camarretta, N., Ehbrecht, M., Wenzel, A., Zuhdi, M., Merk, M. S., Schlund, M., Knohl, A., and Erasmi, S.: Using Airborne Laser Scanning to characterize different land uses in a tropical landscape based on their structural complexity, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10765, https://doi.org/10.5194/egusphere-egu21-10765, 2021.

14:04–14:06
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EGU21-11776
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ECS
Sastrika Anindita, Steven Sleutel, and Peter Finke

The impact of soil age on geochemical properties and carbon cycling has been studied via chronosequences. However, only few studies have addressed how land-use and soil age might interactively shape properties of Andosols and in turn their capability to retain organic carbon (OC). Geochemical soil analyses and laboratory incubation experiments were carried out to assess soil characteristics and mineralization of soil organic carbon (SOC) in Indonesian soils with two contrasting land uses, viz. pine forest and horticulture. Both of these land uses are the results of conversion of primary forest which had similar parent materials, soil age, as well as weathering intensity. Results showed that intensive agricultural practices (+ 40-50 years) did not result in a significant loss of SOC or the increase of bulk density compared to forest. On the other hand, they were found to increase pH, exchangeable cations, base saturation, and most strikingly non-crystalline materials (i.e. Alo + ½ Feo) leading to phenotype formation in agricultural soils. Positive correlations were found between non-crystalline materials with properties such as soil specific surface area and micropores volume, and it was also positively correlated with SOC, particularly in the subsoil. This study highlighted the resilience of Andosols to soil degradation under agricultural practices and its ability to stabilize SOC.

How to cite: Anindita, S., Sleutel, S., and Finke, P.: Agriculture effects on geochemical soil properties and stability of soil organic carbon on tropical Andosols, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11776, https://doi.org/10.5194/egusphere-egu21-11776, 2021.

14:06–14:08
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EGU21-8240
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ECS
Reena Macagga, Shrijana Vaidya, Danica Antonijevic, Marten Schmidt, Matthias Lueck, Mihály Jancsó, Juergen Augustin, Pearl Sanchez, and Mathias Hoffmann

The Philippines is one of the world’s leading producers of pineapples, wherein production is comprised mostly of small family farms that are less than 2 hectares in size. As by-product, they generate a large amount of plant residues (e.g., crowns and stems) that are commonly left at the edge of the field. This practice releases substantial amount of greenhouse gas (GHG) emissions and neglects the potential value of pineapple residue. Enabling a waste treatment by returning them to the field through incorporation or mulching holds the potential to maintain soil fertility, reduce climate impact, secure yield stability, and achieving a high resource efficiency by closing material cycles locally. It may also increase soil organic carbon stock (SOC) and reduce greenhouse gas (GHG) emissions. To date, however, the knowledge about this is still very sparse.

The rePRISING project aims to demonstrate that returning pineapple residue either through mulching or incorporation to the field may help promote the closing of nutrient-cycles (C/N/P/K) locally, thus helping to increase soil fertility and soil C sequestration, while reducing GHG emissions. Within the project, the recycling of pineapple residue together with various local organic and inorganic amendments will be studied during a two-year field experiment using the manual closed chamber method. The field study will be supplemented by pot-scale greenhouse and incubation experiments, used inter alia to determine baseline GHG emissions and carbon budgets of pineapple cultivation systems and residue treatments.

Here we present first results of a pot experiment performed during winter 2020-2021 used to develop a suitable procedure for the in-situ determination of dynamic net ecosystem C balances (NECB) for pineapple cultivation systems. This will be further utilized for upcoming field study. This is challenging in so far as pineapple plants use the Crassulacean acid metabolism (CAM photosynthesis) and the manual closed chamber method has not yet been applied to determine NECB from CAM plants.

Keywords: nutrient-cycling, carbon sequestration, greenhouse gas (GHG) emissions, pineapple residue, climate change mitigation

How to cite: Macagga, R., Vaidya, S., Antonijevic, D., Schmidt, M., Lueck, M., Jancsó, M., Augustin, J., Sanchez, P., and Hoffmann, M.: Reuse of Pineapple Residue in Philippine Agriculture: determination of the net ecosystem C balance for a CAM plant in a pot-scale experiment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8240, https://doi.org/10.5194/egusphere-egu21-8240, 2021.

14:08–14:10
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EGU21-16162
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ECS
RamyaPriya Ramesh and Elango Lakshmanan

The carbon fluxes in rivers plays a critical role in the global carbon cycle but its role is always understated. The tropical rivers alone accounts for about 70% of global riverine carbon fluxes due to their large areal extent, varying climatic conditions and land use. Studies on the dissolved carbon fluxes in non-perennial tropical rivers are limited, but it holds much importance as that of perennial rivers. Hence, the present study was carried out with an objective to understand about the inorganic and organic carbon fluxes in a large non-perennial tropical river of Southern India. The samples were collected from 28 locations along the river thrice in a year from 2013-2020 and were analysed for major ions, DIC and DOC. The concentration of DIC in the river water in most of the locations is greater than that of DOC. The DOC concentration is greater at pristine locations thereby decreasing along the flow direction of the river, whereas the DIC concentration increases along the flow direction. The spatial and temporal variability in DOC and DIC concentrations is attributed due to the changes in the rainfall, river flow, climate, lithology, land use patterns, in the catchment. The DIC concentration was found to be majorly governed by silicate and carbonate weathering along with biogenic process, mineralisation and other river process, whereas the primary production, microbial process along with soil organic carbon influences the DOC concentration in the rivers. Thus, this study identifies the sources of DIC and DOC in rivers and the processes which influences the carbon export to the sea.

How to cite: Ramesh, R. and Lakshmanan, E.: Assessment of the dissolved inorganic and organic carbon flux in Cauvery, a tropical river of Southern India., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16162, https://doi.org/10.5194/egusphere-egu21-16162, 2021.

14:10–14:12
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EGU21-4075
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ECS
Giuseppe Cipolla, Salvatore Calabrese, Leonardo Valerio Noto, and Amilcare Porporato

To mitigate global warming, a noticeable research effort is being devoted to NCS (Natural Climate Solutions) as means to reduce greenhouse gas emissions or sequester carbon within the oceans or terrestrial environments by exploiting natural processes. Enhanced weathering is a NCS that aims to increase the weathering reaction rates of silicate minerals, by amending soils with crushed reactive minerals. Various studies have shown that this technique is favored by hot and humid climates (i.e., tropical ecosystems), since weathering reactions are mostly effective under high temperature and soil moisture. Despite olivine dissolution dynamics in laboratory conditions are quite well known, understanding and modeling them in field is still a challenge. Indeed, apart from some pot experiments involving soils of agricultural fields, only few weathering models are available. Given the urgency of the problem, models play a very important role for extrapolating results of laboratory and field experiments in both time and space, as well as for quantifying the impact of hydroclimatic fluctuations on the involved biogeochemical processes.

The present study explores the role of hydrological processes on long-term Forsterite dissolution, a highly reactive silicate mineral also known as Mg-olivine or simply olivine. Toward this goal, we present a novel dynamic mass balance model coupling ecohydrological and biogeochemical dynamics, including mineral dissolution. Results under different climate scenarios highlight that hydrological fluctuations lead to hysteretic patterns of weathering rate with soil moisture, meaning that the process maintains a memory of past events (i.e., dry or wet periods). The model allows to explore the twofold role of organic matter on enhanced weathering; indeed, while its decomposition is a source of CO2, organic matter also increases the soil CEC, thus buffering changes in soil pH. Carbon sequestration and nutrients availability due to enhanced weathering are quantified, in this study, as a function of MAP (Mean Annual Precipitation). Average CO2 that reacts with olivine can exceed 40 t ha-1 y-1 for MAP higher than 2000 mm, condition that is always reached in the tropics. This CO2 can be found as dissolved in soil water in the form of bicarbonate (HCO3-) and carbonate (CO32-) ions and will be leached away from the domain, eventually reaching the ocean. In presence of tropical climate olivine application also leads to an increase of soil pH and nutrients availability, especially calcium and magnesium, which in turn can enhance plant productivity. This study paves the way for a potential integration of enhanced weathering in agroecosystem management practices, especially in humid tropical regions since these are characterized by high MAP and temperature.

How to cite: Cipolla, G., Calabrese, S., Noto, L. V., and Porporato, A.: The role of hydrological processes on enhanced weathering for carbon sequestration in soils in tropical areas, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4075, https://doi.org/10.5194/egusphere-egu21-4075, 2021.

14:12–15:00