The world has been significantly transformed by human actions at least throughout the course of the Holocene with implications for ecological functioning, climate regulation, etc. Central to furthering understanding of the timing, extent and impact of these transformations is quantification of vegetation cover and land-use at local, regional and continental scales, and at centennial to millennial timescales. Recent accelerations in the intensity of human land use have been implicated for changes in biodiversity, however, relationships between land use change and diversity are complex and include important historical legacies. This session explores recent developments in, and applications of, the quantification of land-cover and land-use from palaeobotanical and palynological data in globally diverse landscapes. We welcome all contributions on methodological advances, and applications to historic and prehistoric long-term dynamics and drivers of land-use, anthropogenic land-cover and land-system change, as well as shifts in biodiversity patterns. These contributions may include pollen and other palaeobotanical approaches to land-use and land-cover change, archaeological and historical records and related palaeoecological data (e.g. palaeoentomological data), as well as modelling studies on anthropogenic land-cover change (ALCC) and climate-land use interactions.

This session contributes to the PAGES LandCover6k working group (http://pastglobalchanges.org/landcover6k). The primary goal of LandCover6k is to use global empirical data on past land-use and anthropogenic land-cover change to evaluate and improve Anthropogenic Land-Cover Change scenarios for earth system modellers (e.g. the World Climate Research Programme CMIP and PMIP initiatives). However, submissions do not need to be explicitly linked to this working group and we welcome abstracts with wider reaching themes spanning environmental responses to human activities, such as biodiversity loss and changes in ecosystem functioning.

Convener: Jessie Woodbridge | Co-conveners: Ralph Fyfe, Petr Kuneš, Furong LiECSECS
| Attendance Thu, 07 May, 10:45–12:30 (CEST)

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Chat time: Thursday, 7 May 2020, 10:45–12:30

Chairperson: Jessie Woodbridge, Ralph Fyfe , Petr Kuneš , Furong Li
D592 |
Chenyi Zhu, Hongyan Liu, Hongya Wang, Siwen Feng, and Yue Han

The most dramatic permafrost degradation is expected to occur at its southernmost distribution, which causes significant vegetation changes in the southernmost boreal forests and consequently affects the carbon stock. To reveal determinants of vegetation change and, in particular, the role of permafrost dynamics, the reconstruction of the long- term vegetation history spanning a warming-cooling cycle is required. Here, we showed that over the last 990 years, vegetation development was characterized by changes in the relative proportions of taxa, such as Larix, Pinus and Corylus, corresponding to the variation in temperature. However, since ~1950 AD, rapid warming has led to the breakdown of the stable relationship among vegetation, climate and permafrost, and the proportion of conifers has shown an increasing trend in the short term due to the influence of permafrost thawing regulated by terrain. In general, we have observed that the coupling system of vegetation, climate and permafrost was stable before ~1950 AD; however, there has been a transition in the most recent rapid warming-induced permafrost thawing. As the southern boundary of permafrost moves northward, it is suspected that the boreal forest in this region will be unstable or may even collapse in the future, and the complete replacement of conifers by broad-leaved trees could greatly reduce the carbon stock in this area by that time.

How to cite: Zhu, C., Liu, H., Wang, H., Feng, S., and Han, Y.: Determinants of ~1000-year woody vegetation dynamics at the southern boreal forest margin in Northeast China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4417, https://doi.org/10.5194/egusphere-egu2020-4417, 2020.

D593 |
| Highlight
Chun-Wei Huang, Yi-Lei Hsu, Hui Xian Lau, and Jerome Chie-Jen Ko

Global urbanization has led to biodiversity decline. Although some case studies reveal rich biodiversity in cities, we still know little about the underlying factors that shape biodiversity at different levels of urbanization. This study statistically analyzes the relationships between environmental, socio-economic and landscape-ecological factors with avian diversity along the rural-urban gradient of Taipei, Taiwan. We use stepwise regression to explore factors that are correlated to variation of bird diversity. First, based on a citizen-science based breeding bird survey in Taiwan (BBS Taiwan), we identify avian richness at different levels of urbanization, using population density as a proxy. Then we correct median income, proportion of tertiary education attainment, precipitation and temperature data from open government data of Taiwan. Finally, we quantify landscape structures using landscape metrics. The results indicate that landscape-ecological factors, such as cohesion of forest, the edge length between building and wetland and area size of building, etc. are correlated with avian richness. On the other hand, socio-economic factors, such as median income and education level are not correlated with avian diversity. Our results reveal that the luxury effect, which describes the positive influence of wealth on urban biodiversity, may not be influential at a subtropical compact city in Asia. On the contrary, we suggest an eco-friendly landscape design that creates a landscape mosaic with scattered trees or wetlands can lead to a network of ecological stepping stones through urban areas for improving bird diversity.

How to cite: Huang, C.-W., Hsu, Y.-L., Lau, H. X., and Ko, J. C.-J.: Exploring Driving Forces of Avian Diversity in a Subtropical Asian City., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7169, https://doi.org/10.5194/egusphere-egu2020-7169, 2020.

D594 |
Esther Githumbi, Marie-Jose Gaillard, Anne-Marie Lezine, Gaston Achoundong, Christelle Hély, Judicael Lebamba, Laurent Marquer, Florence Mazier, and Shinya Sugita

Currently interaction between climate and land-cover change in the past across the globe, and whether drivers are anthropogenic or natural are among the biggest debates. The impacts of climate and land-cover change are having significant consequences on biodiversity and ecosystems. Wide ranging palaeoenvironmental methods have contributed to this debate by providing long-term records of both climate and land-cover change. This provide the context for evaluating the effect of land-cover change on climate.  Inferred past land-cover and climate change from palaeoecological proxies therefore need to be quantified to provide reliable estimates of change; there are several methods of quantifying land-cover change in the past of which the Landscape Reconstruction Algorithm (LRA)  can estimate past land-cover change quantitatively at both regional and local spatial scales using fossil pollen records. The LRA includes two models (REVEALS and LOVE) and has already been tested and validated in Europe, North America, and China.

In this study, we apply the LRA on Holocene pollen records in Cameroon to estimate past land-cover change. This is the first pollen-based, quantitative land-cover reconstruction using LRA in Africa.  It will provide a comparison with land-cover change described from raw pollen data and useful information for climate modelling. The first phase involved the estimation of relative pollen productivity (RPP) for 13 taxa using the pollen-vegetation relationship described by the ERV model. The second phase involves the application of LRA using the RPPs from the 13 taxa.


 Acknowledgements: We thank the French ANR (National Research Agency; projects C3A ANR-09-PEXT-001 and VULPES ANR-15-MASC-0003) and the Belgian project BR/132/A1/AFRIFORD for financial support, IRD (France) and the Ministry of Research and National Herbarium of Cameroon for research facilities and authorizations, and A. Vincens, J.-P. Cazet, G. Buchet, L. Février, and K. Lemonnier (CNRS) for laboratory and field assistance. The study is a contribution to PAGES LandCover6k (www.pastglobalchanges.org/ini/wg/landcover6k/intro).

How to cite: Githumbi, E., Gaillard, M.-J., Lezine, A.-M., Achoundong, G., Hély, C., Lebamba, J., Marquer, L., Mazier, F., and Sugita, S.: Quantitative land-cover change in West Africa over the Holocene: case study in Cameroon, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9054, https://doi.org/10.5194/egusphere-egu2020-9054, 2020.

D595 |
Renske Hoevers, Nils Broothaerts, and Gert Verstraeten

Rivers and alluvial floodplains are dynamic environments facing natural and anthropogenic impacts. A thorough knowledge of the functioning of alluvial floodplains and their sensitivity to changes in internal and external driving forces is required for sustainable management of these ecosystems.

During the Early and Middle Holocene, most floodplains in northern and central Belgium were stable environments with limited floodplain aggradation resulting in the formation of peat. During these times, floodplains consisted mainly of large marshes where peat accumulated and river channels were absent or small. During the Late Holocene, these environments changed completely towards single channel meandering rivers with overbank deposits, impeding peat accumulation, largely as a result of increasing anthropogenic impact. However, this evolution in floodplain geoecology is diachronous as some river valleys transform a few thousand years before others.

Previous research already showed that river systems respond non-linearly to changes in land-use and land-cover in their catchments, as land-use intensity and slope-channel coupling need to cross a certain threshold to result in significant change. Hence, the differences in timing of floodplain response can to some extent be related to different land-use trajectories in the river catchments. Based on previous qualitative and semi-quantitative research the exact land-cover threshold, i.e. the land-use intensity required to result in transformation of the fluvial system, as well as the timing at which this threshold is crossed, could not be detected. Hence, a quantitative assessment of the resilience of floodplain environments to regional land-use changes is needed. A successful pilot REVEALS-based reconstruction of the Dijle catchment, showed a decrease in forest cover from the Bronze Age onwards, accompanied by an increase in the proportion of cereals.

In this study, we constructed a database of pollen-records collected in the eastern part of Flanders, mainly retrieved from river floodplains, as deposits from large lakes are not available in the area. We selected sites with varying soil properties, topographies, and histories of human impact in their catchments, to uncover regional differences in land-cover evolution through the application of the REVEALS model. To assess the applicability of this model to alluvial deposits, modern pollen data will be included and outcomes will be compared to modern vegetation maps. In addition, vegetation reconstructions will be compared with historical maps (available from 1778 AD onwards).

Results will help to answer questions regarding the sensitivity of Flanders to (future) environmental changes. Our study contributes to the understanding of Holocene land-cover change and its drivers, by providing quantitative vegetation cover reconstructions for Belgium that are currently lacking in the European REVEALS reconstructions. Moreover, it extends the application of the REVEALS model to pollen-records retrieved from alluvial deposits.

How to cite: Hoevers, R., Broothaerts, N., and Verstraeten, G.: Quantitative reconstruction of Holocene vegetation cover in Flanders, Belgium - a study based on pollen-records from alluvial floodplains, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9322, https://doi.org/10.5194/egusphere-egu2020-9322, 2020.

D596 |
Furong Li, Marie-José Gaillard, Shinya Sugita, Xianyong Cao, Ulrike Herzschuh, Yan Zhao, Qinghai Xu, and Jian Ni

Quantification of the effects of human-induced vegetation-cover change on past (present and future) climate is still a subject of debate. Our understanding of these effects greatly depends on the availability of empirical reconstructions of past anthropogenic vegetation cover. Such reconstructions can be used to evaluate Anthropogenic Land-Cover Change (ALCC) scenarios for the past (such as HYDE and KK), and simulated past vegetation using dynamic vegetation models such as LPJGUESS. In this context, China is an important region given that agriculture started already in early Holocene, and expanded rapidly over large areas throughout the eastern part of the country. Quantitative reconstructions of plant cover based on pollen data has long been a challenge. The REVEALS model (Sugita, 2007) is one of the approaches for quantitative reconstruction of past plant cover that has been applied, tested, and validated in many regions of the world over the last years. Relative pollen productivity (RPP) of plant taxa is a key parameter required for REVEALS applications. A synthesis of all RPP estimates available in temperate China is published in Li et al. (2018). These RPPs were used with pollen records from lakes and bogs to produce REVEALS-based estimates of Holocene regional vegetation-cover change in temperate China. In order to interpret the REVEALS reconstructions in terms of climate or anthropogenic land-cover change, we compared the REVEALS estimates of vegetation-cover change with existing palaeoclimatic data and archaeological evidences on human history and past land-use change. We also compared the REVEALS estimates with fractions of plant functional types simulated by LPJGUESS and ALCC scenarios from HYDE and KK.

The results suggest that the REVEALS-based values of plant cover strongly differ from the pollen percentages and provide new insights on past changes in plant composition and vegetation dynamics over the Holocene. Human-induced deforestation is highest in eastern China with 3 major phases at ca. 5500, 3000 and 2000 calibrated years before present. Disentangling human-induced from climate-induced pollen-based open-land cover remains a challenge. However,  thorough comparison of the REVEALS reconstructions with historical and archaeological information on settlement and land-use history, and with palaeoclimate reconstructions provide important clues to the question. This study is a contribution to PAGES LandCover6k.

References: Li et al., 2018. Front Plant Sci; Sugita, 2007. Holocene.

How to cite: Li, F., Gaillard, M.-J., Sugita, S., Cao, X., Herzschuh, U., Zhao, Y., Xu, Q., and Ni, J.: REVEALS-based reconstruction of Holocene vegetation abundance in temperate China: new insights on past human-induced land-cover change for climate modelling, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9417, https://doi.org/10.5194/egusphere-egu2020-9417, 2020.

D597 |
Yue Han, Hongyan Liu, Lingyu Zhou, Qian Hao, and Ying Cheng

Tree and grass coexist in south edge of Gobi, northern China. In this region, forest plays an important role in windbreak and sand fixation, and grassland is the foundation of animal husbandry. Afforestation can improve the environment and regulate the climate, but it also restricts the animal husbandry by reducing grassland. Based on robust method for tree and grass cover reconstruction with 19 000-year-long pollen records from northern China, we show that, the past tree cover peaked during the early Holocene (30.7±12.3%), and grass cover was generally stable (45.3±3.9%). Temperature, precipitation, tree-grass competition and fire had driven the postglacial evolution of tree/grass cover, and forest can suppress grassland by tree-grass competition when tree cover is higher than 13.8%. Our study provides implications for weighting between afforestation and grassland protection.

How to cite: Han, Y., Liu, H., Zhou, L., Hao, Q., and Cheng, Y.: Postglacial evolution of forest and grassland in south edge of Gobi, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10036, https://doi.org/10.5194/egusphere-egu2020-10036, 2020.

D598 |
| Highlight
Marie-Jose Gaillard, Andria Dawson, Ralph Fyfe, Esther Githumbi, Emily Hammer, Sandy Harrison, Furong Li, Marco Madella, Kathleen D. Morrison, Benjamin Stocker, Marc Vander Linden, and Nicki J. Whitehouse

The question of whether prehistoric human impacts on land cover (i.e. anthropogenic land cover change due to land use, LULC) were sufficiently large to have a major impact on regional cli-mates is still a matter of debate. Climate model simulations have shown that LULC datasets can have large regional impacts on climate in recent and prehistoric time (1). But there are major differences between the available LULC scenarios/datasets such as HYDE (History Database of the Global En-vironment) and Kaplan’s KK10 (2), and diagnoses of inferred carbon-cycle impacts show that none of the scenarios are realistic (3). The only way to provide a useful assessment of the potential for LULC changes to affect climate in the past, is to provide more realistic LULC data based on palaeovegetation and archaeological evidence to improve the LULC datasets used in climate modelling(4). We use the REVEALS model to reconstruct LC from pollen data at a regional scale, and archaeological data to map LU types and distribution, and estimate per capita LU. The archaeology-based LU maps and per-capita LU estimates are used to improve LULC datasets. Pollen-based REVEALS LC estimates are then used to evaluate/validate the new, improved LULC datasets. These new datasets will be used to implement past land use in palaeoclimate and carbon cycle model simulations. Such simulations are necessary to assess the impact of LULC changes in the past and understand the effect of ecosys-tem management on future climate. We present results from five years of PAGES LandCover6k activities. 

(1) Strandberg G, Kjellström E, Poska A, Wagner S, Gaillard M-J et al. (2014) Regional climate model sim-ulations for Europe at 6 and 0.2 k BP: sensitivity to changes in anthropogenic deforestation. Clim. Past 10, 661–680.
(2) Gaillard M-J, Sugita S, Mazier F et al (2010) Holocene land-cover reconstructions for studies on land cover-climate feedbacks. Clim. Past 6, 483-499.
(3) Stocker B, Yud Z, Massae C, Joos F (2017) Holocene peatland and ice-core data constraints on the tim-ing and magnitude of CO2 emissions from past land use. www.pnas.org/cgi/doi/10.1073/ pnas.1613889114.
(4) Harrison S P, Gaillard M-J, Stocker B D, Vander Linden M, Klein Goldewijk K, Boles O, Braconnot P, Dawson A, Fluet-Chouinard E, Kaplan J O, Kastner T, Pausata F S R, Robinson E, Whitehouse N J, Madella M, and Morrison K D (2019) Development and testing of scenarios for implementing Holocene LULC in Earth Sys-tem Model Experiments, Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2019-125, in review, 2019.




How to cite: Gaillard, M.-J., Dawson, A., Fyfe, R., Githumbi, E., Hammer, E., Harrison, S., Li, F., Madella, M., Morrison, K. D., Stocker, B., Vander Linden, M., and Whitehouse, N. J.: Goal and products of PAGES LandCover6k 2018-2020: Past Global Land Cover and Land Use for Climate Modelling, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11082, https://doi.org/10.5194/egusphere-egu2020-11082, 2020.

D599 |
Fujiang Hou, An Hu, Shenghua Chang, and Xianjiang Chen

Spatial heterogeneity has been widely used in the study of succession in abandoned croplands worldwide, and it is often accompanied by time heterogeneity. However, the effect of temporal heterogeneity on succession dynamics over decades is not well understood. Here, we used croplands with same history in northwest China that were abandoned in 1998, 1999, and 2000 and continuously monitored vegetation characteristics for ten years. Croplands were left undisturbed throughout the study. Non-metric multidimensional scaling was used to interpret changes in the plant community, and taxonomic and functional diversity measures were compared in three treatment over time. Our results show that the directions of succession in all three croplands were similar, from single superior community (Salsolacollina Pall.) with higher aboveground biomass to multi-superior community (Artemisia capillaris Thunb., Stipa bungeana Trin., Lespedeza davurica (Laxm.) Schindl, Heteropappus altaicus (Willd.) Novopokr) with lower aboveground biomass. Taxonomic and functional diversity increased rapidly in the first 4–6 years, followed by a slow increase, decrease or stabilization. Temporal heterogeneity had no effect on species richness after the 7th year, on the Shannon-Wiener index, species evenness, modified functional attribute diversity, or functional divergence after the 8th year, or functional evenness after 5th year. We conclude that temporal heterogeneity can affect the process of secondary succession but has no effect on the direction of community succession. Our findings provide evidence for using temporal heterogeneity to study succession in abandoned croplands in semi-arid areas. 

How to cite: Hou, F., Hu, A., Chang, S., and Chen, X.: Temporal heterogeneity affects the process of succession but not its direction in abandoned croplands in a semi-arid area of northwest China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12288, https://doi.org/10.5194/egusphere-egu2020-12288, 2020.

D600 |
| Highlight
Niina Kuosmanen, Petr Kuneš, Karen Halsall, Helena Svitavska Svobodova, Jana Beranova, Gina Hannon, Peter Fleischer, Richard Chiverrell, and Jennifer L. Clear

Investigating past changes in temperate mountain spruce forest ecosystems and the processes behind them can provide valuable information for understanding present and future ecosystem dynamics. To assess the late Holocene ecosystem change and disturbance history in mountain spruce forests, we sampled four small forest hollows from the High Tatra mountains in Slovakia.  

We use pollen analysis to reconstruct changes in forest composition over the last circa 5000 cal. yr BP. Fire history is analysed using macroscopic charcoal counts and charcoal area measurements. As disturbance is one of the key factors shaping mountain forest dynamics, the analysed pollen records will be processed with a new method quantifying disturbance based on plant ecological indices (Kuneš et al. 2019). These indices for disturbance will be attributed to pollen taxa and then disturbance frequency and severity for the whole community will be calculated. We assess the role of climate and human impact as potential drivers on the past forest and disturbance dynamics. The climate variable will be constructed from modelled climate data for the last 4000 years and for the past 1000 years we will use climate reconstruction from the tree-ring records from the region. We use human indicator pollen taxa as the variable for human influence on ecosystem dynamics, and to indicate human activity in the region.

Preliminary results demonstrate opening of the landscape circa 800-500 cal. yr BP in connection with a change in the disturbance regime as indicated by the disturbance indices. The presence of human indicator pollen taxa in all small hollow records suggest landscape opening in connection with anthropogenic activity in the region. In addition, the charcoal records demonstrate periods of fire, which coincide with the opening of landscape and it is plausible that change in the fire regime is connected to the intensified human activity in the region. These results will be discussed further in the presentation in the light of climate data and further data analysis.


Kuneš, P. Abraham, V. & Herben, T. 2019. Changing disturbance-diversity relationships in temperate ecosystems over the past 12 000 years. Journal of Ecology 107:1678–1688.

How to cite: Kuosmanen, N., Kuneš, P., Halsall, K., Svitavska Svobodova, H., Beranova, J., Hannon, G., Fleischer, P., Chiverrell, R., and Clear, J. L.: Late Holocene ecosystem change and disturbance dynamics in central European mountain forests, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12778, https://doi.org/10.5194/egusphere-egu2020-12778, 2020.

D601 |
Laurent Marquer, Andrea Seim, and Anne Dallmeyer and the Data Contributors

Quantifying the long-term trend of climate versus land use influence on vulnerable ecosystems is of great importance to identify the threats of landscape modifications on biodiversity and ecosystem services, and therefore on societies. The evaluation of the resilience of ecosystems is particularly important considering the ongoing climate change.

As ecosystems in arid Central Asia are mainly influenced by climate and physical geography and most species are growing near their physiological limit, the predicted increased aridity for this region likely increases the threat on the ecosystems in this region.

Pollen are the main proxy to explore changes in vegetation at different spatial (local to subcontinental) and temporal (decades to millennia) scales. To quantify human- and climate-induced changes in vegetation, past land-cover (pollen-based estimates), land use (human deforestation scenarios and human population size) and climate (variables derived from climate models) data can be combined, as it has been done in Europe (e.g. Marquer et al., 2017).

This study aims at quantifying the effect of past climate changes on vegetation in Central Asia over the past millennia at century time scale. For this purpose, we use 49 pollen data from sedimentary records (lakes and mires) which were transformed into vegetation composition and diversity indices. Pollen data as point estimates and spatial grids of past vegetation are combined with available annually resolved gridded summer temperature and precipitation estimates inferred from tree-ring chronologies in this region. The reconstructed climate and vegetation trends are compared to different transient Earth System model simulations with the help of the biome-model BIOME4 (c.f. Dallmeyer et al., 2017). Statistical analyses have been performed to compare all data.

We found clear spatial pattern in the plant distribution with i) a large abundance of coniferous trees in northernmost areas and to a lesser extend in the mountains (e.g. Tian Shan), ii) steppes in the lowlands and at high plateaus, and iii) semi-deserts and steppes in the lowlands. The vegetation composition and diversity have significantly changed over the past millennia. Those changes are mainly related to modifications in composition and diversity of plant species in steppes and semi-deserts, of coniferous trees in the mountains, and changes in land use. Our results reveal that precipitation is the major driver of vegetation composition and diversity in Central Asia whereas temperature mainly explains the spatial variation, in particular during major climate events, e.g. the Little Ice Age and the Warm Medieval Period. Further studies are now in progress to quantify the relative (to climate) influence of land use (e.g. anthropogenic land-cover change; ALCC) in the region.

This study demonstrates the climate dependency of vegetation composition and diversity in Central Asia, especially during the major climate events over the last two millennia. This opens the discussion about the resilience of vulnerable ecosystems facing severe impacts of ongoing and predicted climate changes in arid Central Asia.      

Dallmeyer et al. (2017) Climate of the Past 13, 107-134. / Marquer et al. (2017) Quaternary Science Reviews 171, 20-37.

How to cite: Marquer, L., Seim, A., and Dallmeyer, A. and the Data Contributors: Response of vegetation to past climate changes in Central Asia, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19229, https://doi.org/10.5194/egusphere-egu2020-19229, 2020.

D602 |
| Highlight
Jessie Woodbridge, Ralph Fyfe, Ruth Pelling, David Smith, and Anne DeVareilles

Conservation and promotion of biodiverse landscapes is a major target for ecological conservation and landscape management, as biodiversity is a key determinant of ecosystem functioning. Recent accelerations in the intensity of human land-use have been implicated for changes in biodiversity, but the relationships between land-use change and diversity are complex, include important historical legacies and major transformations are likely to have occurred across much longer time-scales than those covered by direct observation records. This collaborative research between Historic England and the Universities of Plymouth and Birmingham, is synthesising palaeoecological datasets from across the British Isles from both the natural and archaeological sciences to reconstruct biodiversity patterns and evaluate relationships between these patterns and land-use over multi-millennial time-scales. The fossil remains of plants, pollen and insects preserved in sediments are being compared and critically evaluated with the aim to provide valuable information about past land-use strategies, biodiversity, habitat resilience to disturbance and recovery rates. Exploring environmental change within the context of the Holocene (the last 11,700 years) allows comparison of ecosystem states across a wide range of land-use strategies, from hunter-gathering to complex patterns of land-use in later prehistoric and historical periods.

How to cite: Woodbridge, J., Fyfe, R., Pelling, R., Smith, D., and DeVareilles, A.: Human land-use change and biodiversity trends in the British Isles , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22407, https://doi.org/10.5194/egusphere-egu2020-22407, 2020.

D603 |
Gretchen Gettel, Elizabeth Wangari, Collins Muhadia, and Sharon Gubamwoyo

Economic development and food insecurity are an important drivers of land use change in tropical ecosystems.  In sub-Saharan Africa, forest and wetland conversion to agriculture and zero-grazing policies are common in highland systems, while livestock-dominated agricultural systems are more common in the drier, semi-arid low-land systems. Greenhouse gasses (GHG) from aquatic ecosystems is increasingly appreciated as missed sources of emissions from agricultural and forested landscapes, and rivers and artificial watering pans are used for livestock watering in these systems. They therefore receive manure and urea, making them potential hotspots for greenhouse gas (GHG) emissions through biogeochemical processing, but the role of livestock has not yet been examined. We performed 4 synoptic surveys for GHG concentration and fluxes in rivers in the Taita Hills and in water pans in the semi-arid region low-lands of Taita-Taveta County, Kenya in October–December 2019, which spanned the transition of short rainy season to the dry season. We also measured water-quality parameters and related them to GHG emissions in order to assess the biogeochemical processes likely responsible for the emissions in each system type. There were 9 agricultural streams (no livestock), 8 livestock streams, and 4 water pans. Results showed ten times higher CH4 and N2O  fluxes in the water pans compared to river systems (~4 vs. 40 mmol CH­4 m-2day-1 and ~4 vs. 30 mmol N2O m-2day-1)  while CO­2 emissions were two times higher in the agricultural streams (~110 vs. 60 mmol CO2 m-2day-1). Water pans also showed higher dissolved organic carbon (DOC) concentration and higher dissolved nitrogen and phosphorus (TDN and TDP) and lower dissolved oxygen (DO) concentrations than river systems. There was a significant positive relationship between pCO2 and fine benthic organic matter (FBOM) in livestock streams but no relationship with DOC, suggesting that increased sediment respiration from livestock may be responsible for CO­2 emission. In river systems, there was also a positive relationship between CH4 and CO2, which indicated that methane production from CO2 was a controlling mechanism. This contrasted with CH4 production in water pans which was related to primary production and organic inputs from livestock. N2O also showed different processes in riverine and water pan systems, with nitrification appearing to be more important in river systems, evidenced by the negative relationship of N2O production with DOC and a positive relationship with CO2. In water pans, N2O was negatively related to NO3­­, dissolved oxygen, and DOC. In addition, more negative fluxes of N2O occurred in water pans than the other sites, which suggests complete denitrification of N2O to N2.  Diurnal measurements also indicated that fluxes were positively related to livestock density; however this effect was more pronounced in the drier season and under low discharge. Water pans were also hotspots in the landscape for CH4 and N2O emissions, showing 10 – 1000 times greater emission than the surrounding landscape. Further research should examine the water pans and riverine watering holes as distinct features with the potential to impact greenhouse gas emissions from agricultural landscapes.

How to cite: Gettel, G., Wangari, E., Muhadia, C., and Gubamwoyo, S.: Effects of land use and livestock watering on greenhouse gas emissions and water quality in rivers and water pans in tropical highland and semi-arid agroecosystems in Taita-Taveta County, Kenya, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22566, https://doi.org/10.5194/egusphere-egu2020-22566, 2020.