Fairy circles are exceedingly regularly spaced barren circular patches in arid landscapes, typically encircled by a ring of taller grasses. These vegetation patterns occur in Southwestern Africa and Australia and have also been suggested to occur in North Africa, Middle East and Madagascar. The enigmatic origins of fairy circles in arid landscape shave intrigued ecologists and sparked heated debate about the two main competing hypotheses: the termite origin and vegetation self-organization hypotheses.
In the southern part of the Giribes Plains, Kunene region, northwest Namibia, fairy circles form in a distinctive, chain-like arrangement along drainage lines that run from north to south, closely aligned along a slope. These fairy circles are unusual in their extreme elongation, with the most extreme case measuring 32.5 meters long and only 7.7 meters wide. In contrast, the fairy circles in the rest of the Giribes outside the drainage lines are typically circular and exhibit a highly ordered, hexagonal pattern. Based on field work, remote sensing and mathematical modeling we explain the formation of these unique fairy circles.
The soil in the matrix between the circles is covered by physical crust, with some areas featuring a thin biocrust. This is the only place in Namibia where soil crust developed in the matrix. This crust causes the matrix soil to be nearly four times more compact than the soil within the fairy circles. The sand within the fairy circles is coarser (D50 ~600 µm) compared to the matrix soil (D50 ~300 µm), which supports the formation of the crust. Interestingly, sand in fairy circles not aligned with the drainage lines is also coarser (D50 ~450 µm). Hydraulic conductivity, measured using a mini-disk infiltrometer, is three to four times greater within the fairy circles than in the surrounded matrix.
Building on these field observations, we hypothesize that the elongated shape of the fairy circles results from anisotropic soil water diffusion. Water diffuses more readily along the drainage lines than in the surrounding matrix, causing the fairy circles to expand more rapidly along the watercourses than laterally. To test this hypothesis, we used the mathematical model of Zelnik et al. (2015), which simulates biomass and soil water densities under varying water-soil diffusion coefficient ratios, r (r=1outside the drainage lines and r>1 inside the fairy circle) and precipitation rates .
The simulations indicate that, for moderate diffusion ratios and varying precipitation rates, elongated fairy circles form along the drainage lines, while circular fairy circles emerge when the diffusion ratio is lower. The results agree with remote sensing analysis of images take from a drone. The stability of the pattern to different precipitation rates and r values was also studied. These results support the hypothesis that anisotropic soil water diffusion contributes to the elongated shape of the fairy circles in the Girbies plain, although other factors may also play a role. Indirectly our work supports the self-organization hypothesis for the origin of fairy circles. The formation of the crust in the matrix remains is still an open question for future research.
How to cite: Yizhaq, H., Getzin, S., katra, I., Kamennaya, N., Peled, Y., and Meron, E.: The origin of the elongated fairy circles in the Giribes Plains, northwest Namibia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3816, https://doi.org/10.5194/egusphere-egu25-3816, 2025.
Drying trends driven by climate change and water stress pose significant threats to ecosystem functioning and the services they provide to humanity. To better understand ecosystem response to drying trends, we study a mathematical model of plant communities that compete for water and light. We focus on two major responses to water stress: shifts in community composition to stress-tolerant species and spatial self-organization in periodic vegetation patterns. We calculate community bifurcation diagrams of spatially uniform and spatially periodic communities. The bifurcation diagram reveals that as precipitation decreases, spatially uniform community shift from fast-growing to stress-tolerant species. However, a reverse shift back to fast-growing species occurs when a Turing bifurcation is traversed and patterns form. We further find that the inherent spatial plasticity of vegetation patterns, in terms of patch thinning along any periodic solution branch and patch dilution in transitions to longer-wavelength patterns, buffers further changes in the community composition, despite the drying trend, and yet increases the resilience to droughts. Response trajectories superimposed on community Busse-balloons highlight the roles of the initial pattern wavelength and of the rate of the drying trend in shaping the buffering community dynamics. We discuss the implications of these results for dryland pastures and crop production.
How to cite: Pavithran, I., Ferre, M., Bera, B., Uecker, H., and Meron, E.: Vegetation pattern formation and community assembly under drying climate trends, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20458, https://doi.org/10.5194/egusphere-egu25-20458, 2025.
Dryland vegetation forms spatial patterns as an adaptation to water stress, driven by the uneven distribution of resources. While these patterns aid plant survival, herbivore grazing adds pressure, increasing desertification risks through vegetation loss and soil erosion. We present a novel model integrating vegetation patterning and herbivore grazing dynamics to explore their feedback loops over time. The model accounts for herbivore behaviors, including foraging, movement, and vegetation preferences. Using numerical continuation methods, we analyze solutions such as uniform and patterned vegetation-herbivore dynamics. A key finding is the emergence of traveling waves, where vegetation and herbivores propagate across the landscape. Herbivore distribution within these waves is asymmetric, causing uneven grazing stress. Surprisingly, this dynamic reduces overall grazing impact, enhancing vegetation sustainability compared to uniform grazing. Understanding these dynamics is vital for food security in drylands. By balancing herbivore populations and preserving vegetation, these interactions help mitigate drought and population growth challenges.
How to cite: Singha, J.: Traveling vegetation-herbivore waves can sustain ecosystems threatened by droughts and population growth, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19596, https://doi.org/10.5194/egusphere-egu25-19596, 2025.
Abstract: Climate models often predict that more extreme precipitation events will occur in arid and semiarid regions, where plant phenology is particularly sensitive to precipitation changes. To understand how increases in precipitation affect plant phenology, this study conducted a manipulative field experiment in a desert ecosystem of northwest China. In this study, a long-term in situ water addition experiment was conducted in a temperate desert in northwestern China. The following five treatments were used: natural rain plus an additional 0, 25, 50, 75, and 100% of the local mean annual precipitation. A series of phenological events, including leaf unfolding, fruit setting (onset, summit and end), fruit ripening (onset, summit and end) and leaf coloration of the locally dominant shrub Nitraria tangutorum were observed from 2012 to 2018. The results showed that on average, over the seven-year-study and in all treatments water addition treatments advanced the leaf unfolding date by 1.29–3.00 days, but delayed the leaf coloration date by 1.18–11.82 days. Therefore, the length of the growing season was prolonged by 2.11–13.68 days. However, water addition treatments had no significant effects on all six fruiting events in almost all years, and the occurrence time of almost all fruiting events remained relatively stable compared with leaf phenology. The inter-annual variations of fruiting events were driven by the preceding flowering events rather than temperature or precipitation.
How to cite: Bao, F.: Contrasting responses of fruiting phenology and folia phenology to water additiontreatments in the Desert Shrub Nitraria tangutorum, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2220, https://doi.org/10.5194/egusphere-egu25-2220, 2025.
The semi-arid lowlands of Baringo County, Kenya provide numerous ecosystem services to pastoral and agro-pastoral communities. However, these services have been significantly impacted by gradual changes in land cover, climate change, shrub encroachment, and invasion of grasslands by species like Prosopis juliflora. This study aimed to investigate how changes in land cover and roads affect vegetation dynamics between 2000 and 2024. This period was chosen due to the availability of consistent satellite-derived Normalized Difference Vegetation Index (NDVI) data for time series analysis. Using the Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN), we analyzed NDVI data for five land cover classes, namely: natural shrubland, artificial grassland, forest, irrigated land, and Prosopis-infested areas. The impact of roads was assessed by calculating the instantaneous energy of high-frequency Intrinsic Mode Functions (IMFs) at buffer distances of 100, 250, 500, 1000, and 1500 meters from the roads in natural ecosystems. The results revealed diverse NDVI trends for different land cover classes. Forest exhibited mixed trends, with some pixels showing positive trends while others remained stable over time. Irrigated agricultural land indicated an increase in trend until 2017, after which it plateaued. Shrubland and artificial grassland maintained steady NDVI values with modest positive trends. Prosopis-infested areas exhibited a positive trend from 2000 to 2017, followed by a decline, likely linked to community-led invasion management efforts. The positive NDVI trends observed in forests and natural shrublands may be attributed to an increased invasion of Prosopis. Seasonal variations were associated with climatic conditions. Statistical analysis indicated that distance from the road had a significant difference on instantaneous energy but with a small effect size. These findings contribute to understanding how infrastructure and land use changes influence vegetation, providing valuable insights for sustainable management of semi-arid rural landscapes.
How to cite: Nyamari, N., Nitschke, S., Kramm, T., Otieno Ochuodho, D., Bareth, G., and Bogner, C.: Impact of Roads on Vegetation Dynamics in the Semi-Arid Baringo County, Kenya, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7446, https://doi.org/10.5194/egusphere-egu25-7446, 2025.
Dryland aeolian landscapes are among the most vulnerable ecosystems under accelerating climate shift and land-use changes, where complex interactions between vegetation, soils, and landforms play a crucial role in maintaining ecosystem resilience and services. This study integrates remote sensing, field surveys, and numerical modeling to explore the coevolution of vegetation and aeolian landforms over the past four decades in East Asia’s arid regions, with a particular focus on the feedback mechanisms driving landscape stability in the arid zones under climatic and human forcing.
Analyses of aeolian landforms and climate systems in northern China reveal that declining wind speeds, associated with global terrestrial stilling, have significantly slowed dune migration rates over the past few decades, while widespread vegetation recovery has stabilized dune fields and mitigated desertification. Restoration practices, such as straw checkerboards, have accelerated vegetation recovery, increasing biodiversity and stabilizing soils, though soil fertility remains low compared to natural systems. Dust activity, an integral component of aeolian systems, have been suppressed in these areas, largely due to both climatic shifts and these large-scale restoration projects. Finally, high-resolution satellite images and field observations highlight how vegetation expansion modifies dune morphology through processes such as vegetation anchoring and sand transport alteration, leading to transitions from active to stabilized states. Conceptual models of vegetated dune morphodynamics provide insights into the role of vegetation-soil-landform feedbacks in shaping the arid landscapes.
This study emphasizes the interconnectedness of climate systems, vegetation dynamics, soil properties, and aeolian processes in maintaining ecosystem resilience and restoring ecosystem services. By linking dune morphologies and vegetation dynamics to thresholds of stability and nonlinear responses to climatic and anthropogenic pressures, the findings contribute to a deeper understanding of how dryland ecosystems adapt and evolve. These insights support more effective strategies for soil conservation, landform stabilization, and the restoration of ecosystem functions in the face of ongoing climate and land-use changes.
How to cite: Xu, Z., Wang, L., and Pang, X.: Deciphering Aeolian Landscape Dynamics: Vegetation Recovery and Dune Stabilization under Climatic and Human Influences, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4912, https://doi.org/10.5194/egusphere-egu25-4912, 2025.
Hydrological connectivity at the hillslope scale is a complex, spatially explicit phenomenon where surface and subsurface processes converge and interact, including infiltration, runoff, and lateral flow occurring during a singular rainfall event under specific antecedent soil moisture conditions.
In drylands, where Hortonian runoff generation prevails, such complexity has been conceptually simplified for operational purposes by using connectivity as a proxy for assessing ecosystem "health" or land degradation. Grounded in the current source-sink paradigm, a binary scheme of vegetation (pure sinks) and bare (pure sources) areas is used to distribute potential overland flow according to topography. The connectivity character is then distilled through the concept of Flow Length, with different metrics proposed under this rationale.
Despite this operational simplicity, the quantification of connectivity has yet to reach a standardized status, hindering intercomparison studies and the establishment of assessment baselines for land degradation.
Within the same framework umbrella, we recognize its shortcomings and propose decomposing the connectivity issue into three spatially explicit traits, each representing distinct structural features that emerge at the hillslope scale. This analytical approach aims to separately evaluate the contributions of vegetation patterns and flow routing, without the constraint of the hillslope shape. Facing the challenge of integrating these traits into a unified, synthetic metric for assessing runoff connectivity, we discuss several alternatives. The study is conducted at the experimental site in Benidorm (Alicante, Spain), using UAS-derived orthophotos and DEMs, where lateral variations within a small catchment serve to test the suitability of the proposal. This methodological proposal aims to advance the conceptual discussion toward developing a standardized approach for runoff connectivity evaluation and to inform land degradation assessments in drylands.
How to cite: Arnau-Rosalen, E., Rodriguez-Caballero, E., Marques-Mateu, A., Balaguer-Puig, M., Lopez-Carratala, J., Calvo-Cases, A., Lazaro-Suau, R., and Symeonakis, E.: Towards Standardising Runoff Connectivity Assessment at the Hillslope Scale in Drylands Using Structural Trait (De)composite., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19726, https://doi.org/10.5194/egusphere-egu25-19726, 2025.
Badlands are characterized by highly eroded, rugged landscapes with steep slopes, limited vegetation, and significant soil degradation. In badlands, vegetation plays a key role in erosion mitigation by intercepting runoff and acting as a significant factor in soil stability. However, vegetation dynamics in such an environment are determined by geomorphological factors like slope, erosion, sediment flux, and climatic conditions, characterized by temperature and precipitation patterns.
This study evaluates the significance of such drivers of vegetation transition within the badland systems using a State-and-Transition Model (STM) approach. This model predicts vegetation dynamics as a function of two basic processes: extinction (loss of vegetation) and colonization (vegetation growth over a barren patch of land). It is forced with vegetation states at four different time points (i.e., 1982, 1994, 2015, and 2021), while climate variables (e.g., temperature and precipitation), and sediment fluxes are averaged for the periods between these states. Geomorphological parameters (i.e., topographic elevation and slope) are assumed to be constant throughout the simulation period. It estimates vegetation transition probabilities using logistic regression. The model parameters are optimized through Bayesian methods (i.e., Markov Chain Monte Carlo algorithm) for climate conditions and geomorphology in the Laval catchment in the Draix-Bléone critical zone observatory, southeastern France. Model performance is quantified through repetitive training and testing to ensure the soundness of the predictions.
The results indicate that colonization is negatively impacted by higher slopes and annual sediment fluxes and is supported by increasing mean annual temperatures and summer precipitation. In contrast, vegetation extinction is driven mainly by geomorphic disturbances (e.g., slope and sediment fluxes during extreme events), while climatic factors seem to have little impact on vegetation extinction in this study area. Indeed, the forward prediction model, initiated using the 1982 vegetation state with best-fit parameters as forcing, resulted in a reasonably close match of the predicted states to the conditions observed, i.e., those of 1994, 2015, and 2021, which had an accuracy of ~0.8, with uncertainties of around ~0.35.
The present study integrates both geomorphological and climatic data to develop valid interpretations concerning environmental factors responsible for vegetation dynamics within badland topography, adding to an improved understanding of the ecosystem dynamics of these sensitive environments.
How to cite: Sharma, H., Le Bouteiller, C., and Boulangeat, I.: Geomorphic and climate-driven vegetation dynamics in badlands – A case study from Laval catchment, Draix-Bléone critical zone observatory, SE France, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6012, https://doi.org/10.5194/egusphere-egu25-6012, 2025.
In China's drylands, deserts and areas prone to desertification constitute 44% of the landscape. The desert-oasis transition zone serves as a critical buffer between the desert interior and the oasis, playing an essential role in managing and preventing desertification. Despite its importance, the question of whether ecosystem functions exhibit multistability and experience regime shifts from functional to desertified states remains unresolved, particularly concerning the relationship between changes in vegetation patterns and ecosystem state transitions at the desert edges of arid and hyper-arid regions. In this study, we examined the stability landscapes of ecosystem multifunctionality and vegetation patterns in response to decreasing precipitation at both the inter-desert scale and within individual deserts, as the distance from the oasis to the desert interior increases. We compared the precipitation and distance thresholds for abrupt changes in vegetation pattern indices with those for regime shifts in ecosystem multifunctionality. Our analysis revealed that ecosystem multifunctionality can exist in both functional and desertified states when precipitation ranges between 104.37 mm and 152.56 mm. However, when precipitation drops below 104.37 mm, a complete shift from a functional to a desertified state occurs. The average precipitation threshold for abrupt changes in vegetation pattern indices—such as the size, shape complexity, and connectivity of vegetation patches, flow length, spatial skewness of the landscape, and the power law range, cutoff, and plexpo of the vegetation patch size distribution—is 201.69 ± 34.87 mm, which is higher than the threshold for ecosystem multifunctionality regime shifts. At the scale of individual deserts, changes in vegetation patterns precede regime shifts in ecosystem multifunctionality. These findings suggest that vegetation pattern indices can serve as early warning indicators for desertification in extremely arid desert-oasis transition zones. This study contributes to the enhancement of early-warning systems and supports the monitoring of desertification processes.
How to cite: Li, C. and Zhou, W.: Vegetation patterns as early warning signals for shifts in ecosystem multifunctionality in the desert-oasis transition zone of China’s drylands , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1786, https://doi.org/10.5194/egusphere-egu25-1786, 2025.
Spatial self-organization is a common response of arid and semi-arid ecosystems to water stress. It may result in periodic patterns such as dots, gaps and labyrinths, or in more irregular arrangements such as scale-free patterns, characterised by a power law distribution of patch sizes. As pattern formation occurs over large spatial domains, in the order of km2 , it is often subject to heterogeneous environmental and soil conditions, which may lead to the anisotropic diffusion of resources.
In our project, we study the effects of anisotropic diffusion on pattern formation through the modelling of vegetation dynamics on complex network topologies.
We employ the well-known reaction-diffusion vegetation model by Gilad et al. [1], in its simplified two-equation version by Zelnik et al. [2]. Two partial differential equations describe the dynamics of soil water and biomass densities.
In our implementation, the diffusive terms refer to network Laplacia, which allows us to the modify the topology on which the model operates.
When the diffusion networks of both water and biomass are regular two-dimensional lattices, we reproduce the observed progression of periodic patterns from gaps to labyrinths to dots for decreasing precipitation.
To increase the complexity and connectivity of the network we implement the Watts-Strogatz small-world network model [3], in which a controlled number of random shortcuts is drawn over the two-dimensional lattice. Thus the number of shortcuts in the water and biomass diffusion networks become model parameters which may be used as proxies of heterogenous conditions affecting the diffusion of water and biomass respectively.
Our preliminary results show that an increase in anisotropic diffusion (number of shortcuts) has similar effects to an increase in isotropic diffusion in regards to the global variables of the ecosystem, such as average water and biomass densities. However, a small-world network topology induces the formation of steady-state non-periodic patterns, included scale free patterns, in a certain interval of network connectedness.
Further, these steady-state scale free patterns appear unstable to the expansion of the largest gaps, leading to rapid desertification following a disturbance that may originate from grazing or human intervention. Hence, we uncover the existance of a bistability between two non-periodic patterns with very different ecological value.
[1] E. Gilad, J. von Hardenberg, A. Provenzale, M. Shachak, and E. Meron. Ecosystem Engineers: From Pattern Formation to Habitat Creation. Physical Review Letters, 93(9):098105, 2004.
[2] Y. R. Zelnik, E. Meron, and G. Bel. Gradual regime shifts in fairy circles. Proceedings of the National Academy of Sciences, 112(40):12327–12331, 2015.
[3] M. E. J. Newman and D. J. Watts. Scaling and percolation in the small-world network model. Physical Review E, 60(6):7332–7342, 1999.
How to cite: Filippini, S., von Hardenberg, J., and Ridolfi, L.: Vegetation patterning dynamics induced by non-local connections, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11850, https://doi.org/10.5194/egusphere-egu25-11850, 2025.
The study of how topographic and geological complexities drive vegetation dynamics over extended timescales, provides critical insights into the interactions between landscapes and ecosystems. Our study area encompasses the Greater Serengeti-Mara Ecosystem (GSME) in the Kenya-Tanzania transboundary region, renowned for its ecological richness and dynamic environments, most famously as the setting for the world’s largest terrestrial mammal migration. We focus on two case study regions: the Mara River Basin (MRB) and the Ngorongoro Conservation Area (NCA) to investigate localized interactions between geological, topographic, and ecological processes. The ecosystems are supported by a healthy and diverse vegetation cover, impacted by natural as well as anthropogenic factors. MRB is bounded in the north by active normal faulting dominated by Utimbara and Isuria faults whereas NCA is centred on Ngorongoro Crater, a large volcanic caldera. The tectonics of NCA is well-studied but subrecent faulting of Utimbara and Isuria was previously unrecognised and the impacts of these faults on uplift, subsidence and tilting of MRB has been revealed only recently. Previous studies have explored the relationship between precipitation and vegetation dynamics in the region. Limited research has focused on soil properties, primarily examining the effects of volcanic ash on the southeastern sector of GSME. However, the role of tectonics in influencing vegetation and, by extension, the broader ecosystem remains underexplored. We used remote sensing data (Landsat 5, 7, 8 and Sentinel 2) to create a time series analysis from the years 1984 until 2024 to examine the changes in the vegetation cover in the study area. Landsat 7 & 8 and Sentinel 2 data were processed in Google Earth Engine whereas those from Landsat 5 & 7 using Erdas Imagine. The normalised differential vegetation index (NDVI) shows a clear difference in vegetation cover during wet and dry seasons throughout the four decades for both the regions. MRB, which is covered by Quaternary sediments, has a higher vegetation cover throughout the year. NCA is affected by intermittent ash eruptions from Oldoinyo Lengai and has a vegetation cover, which varies at differing altitudes within the region and also shows a considerable seasonal variation at lower altitudes. Additionally, there is a significant difference in precipitation between MRB and NCA. In such a scenario, the vegetation cover in both the regions is likely to be a function of the interaction between the inherent soil properties and precipitation. Interestingly, stable vegetation also persists along active faults. Fault escarpments and fault-bounded wetlands provide seasonally stable vegetation cover, potentially due to localized influences on hydrology and soil properties and may serve as refugia during dry seasons. Our preliminary results highlight the need to integrate geo-tectonic analysis into broader ecosystem studies to better understand their role in sustaining biodiversity and ecosystem resilience.
How to cite: Purohit, C., Ludat, A., Said, A., Machunda, R., Hank, T., Kahle, B., and Kuebler, S.: Exploring the impacts of active faulting & tectonics on the vegetation cover of the dynamic Serengeti-Mara and Ngorongoro ecosystems of East Africa through spectral index analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3466, https://doi.org/10.5194/egusphere-egu25-3466, 2025.
Shrubs, characterized by their multiple dwarf stems, are a dominant plant functional type in arid and semi-arid regions, which cover 40% of Earth's land surface. These ecosystems are fragile and highly susceptible to climate change and human disturbances. The abundance of shrubs serves as an important indicator of ecosystem health, and their projected increase due to CO₂ fertilization and warming climates could significantly alter ecosystem functioning, exacerbate desertification, and impact essential ecosystem services. Monitoring shrub fractional abundance—the proportion of vegetative cover occupied by shrubs—is crucial for understanding these dynamics and guiding sustainable management practices. However, mapping shrub fractional abundance over large areas presents challenges due to their small crowns, sparse distribution, and high density, rendering traditional field surveys and conventional satellite remote sensing techniques inadequate. In this study, we propose an innovative two-step approach that integrates sub-meter resolution Google Earth (GE) imagery with decametric-resolution Sentinel-2 time-series data for accurate and scalable shrub fractional mapping. Our methodology consists of two main steps: (1) a semi-automatic process that uses GE imagery to delineate 1.31 million shrub crowns and generate high-quality training data, and (2) a machine learning model that combines spectral and phenological features from Sentinel-2 data to upscale GE-derived shrub fractional abundance across diverse arid and semi-arid landscapes in Inner Mongolia, China. The model achieved strong predictive accuracy (R² = 0.70), with phenological features—particularly during early May, mid-June, and late September—proving critical for distinguishing shrubs from seasonal vegetation. These periods correspond to key phenophases, including germination, peak growth, and senescence of grasses, which contrast with the perennial phenology of shrubs, highlighting the significance of phenology in differentiating shrubs from dynamic seasonal vegetation. Our results demonstrate the effectiveness of integrating multi-scale remote sensing data with machine learning to address existing limitations in shrub monitoring. This approach provides a scalable and transferable framework for global mapping of shrub fractional abundance, offering valuable insights into shrub encroachment and its implications for ecosystem health in the context of changing climatic and anthropogenic conditions.
How to cite: Liu, Z., Cao, X., Peñuelas, J., Descals, A., Yang, D., Liu, L., Su, Y., Liu, L., Chen, J., and Wu, J.: Mapping Shrub Fractional Abundance: A Multi-Scale Remote Sensing and Machine Learning Framework for Arid Ecosystem Monitoring, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5452, https://doi.org/10.5194/egusphere-egu25-5452, 2025.
Streamflow in several catchments in eastern Australia has decreased considerably (up to 40%) over the past 20 to 30 years, despite stable rainfall levels. This decoupling of streamflow and rainfall undermines the predictive accuracy of rainfall-runoff models used by catchment managers, which typically rely on the assumption of a stable relationship between these variables. Similar non-stationarity in streamflow has been observed in other catchments in the world, and evidence suggests that vegetation processes may be driving this non-stationarity due to increases in temperature and CO2. Current rainfall-runoff models fail to capture the impact of these vegetation changes on evapotranspiration (ET). While these models account for ET's dependence on soil moisture, they do not consider changes in vegetation biomass and health, which can significantly alter ET and, consequently, runoff.
This contribution presents a methodology for estimating a vegetation-aware ET based on the Penman-Monteith equation and emulators that can account for changes in vegetation biomass and health. The emulators are developed using data from the Australian and New Zealand Flux Research and Monitoring network (TERN OzFlux). This network provides extensive measurements of energy, carbon, and water exchanges across various ecosystems, from which vegetation effects can be estimated under different environmental conditions, and across different vegetation types. Through this research we aim to contribute to understanding evapotranspiration dynamics and offer a reliable and simple tool for estimating vegetation effects, ultimately adding it to more realistic rainfall-runoff simulations.
How to cite: Brieva, C., Jorquera, E., Quijano, J., Kuczera, G., Saco, P., Rodriguez, J., and Kibria, G.: Accounting for Vegetation Feedbacks in Hydrological Models Using a New Vegetation-aware Evapotranspiration Formulation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5142, https://doi.org/10.5194/egusphere-egu25-5142, 2025.
Salt-tolerant Tamarix chinensis roots are crucial in preserving wetland soil and carbon sequestration, which is essential for wetland ecology. Soil-water-salt conditions influence the growth of these roots in coastal saline areas, but the specific factors and their effects remain unclear. Using principal component and partial least square structural equation modelling (SEM) methods, we studied T. chinensis root features in six Yellow River delta communities. Results showed varied root features across locations, with larger roots further inland. Root growth negatively correlated with soil texture and salinity and positively with groundwater levels. Soil texture and salinity decreased with distance from the coast, while groundwater increased with distance from the Yellow River. This suggests that geographical location influences soil water-salt conditions, impacting root characteristics. The principal component analysis–derived root feature index captured 56.7% of root feature variation. SEM revealed geographical locations indirectly influence root features, with the Yellow River’s proximity primarily affecting them through groundwater and coastal distance influencing via soil sand content and salinity. The study underscores the importance of these findings for wetland conservation and ecology.
How to cite: lizhu, S.: Soil spatial heterogeneity created by river–sea interaction influences Tamarix chinensis root features in the Yellow River Delta, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5353, https://doi.org/10.5194/egusphere-egu25-5353, 2025.
Mangrove wetlands are one of the most significant and vulnerable ecosystems in the world, providing a wide range of services including habitat, flood control and carbon storage, among others. Their vulnerability under climate change scenarios has been well documented, but recent works have shown that coastal wetlands have the capacity to accrete following the trend of SLR under particular circumstances. Suspended sediment concentration (SSC) plays a critical role in the accretion mechanisms that support wetland survival.
Wetlands in the Pacific Islands are among the most vulnerable areas to climate change and they receive considerable sediment from croplands (sugarcane) of their inland catchments. This contribution focuses on mangrove wetlands at the mouth of rivers draining into the Great Sea Reef. The objectives of our research are to evaluate the sediment loads from the catchment upstream of the coastal wetlands and to model the ecogeomorphological feedbacks among catchment, wetland and coastal reef lagoon under current conditions and future climate change scenarios. The methodology simulates the hydro-sedimentological behaviour of the watershed, under current and future scenarios with changes in land use (cropland expansion/management) and extreme events (cyclones). The output of this simulation constutute the input for the eco-geomorphological coastal wetland modelling.
This integrated modelling approach provides a better understanding of the main processes and feedbacks among vegetation, sediments and hydrodynamics within the coastal wetland, considering its interactions with the adjacent terrestrial (catchment) and aquatic (reef lagoon) ecosystems.
How to cite: Jorquera, E., Rodriguez, J., Saco, P., Sandi, S., Quijano, J., and Breda, A.: Effects of climate and human activities on mangrove wetland evolution., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7458, https://doi.org/10.5194/egusphere-egu25-7458, 2025.
The different temporal scales of surface flow and vegetation growth represent a major challenge when simulating the dynamics of ecohydrological systems. The much faster surface flow is therefore commonly simplified by treating it as stationary and linearizing the equations. While the simplified equations can be solved efficiently, they do not resolve individual runoff events. However, the sequence of events can be relevant for the dynamics of dryland vegetation. The nonlinear flow during individual precipitation events can be resolved by employing more sophisticated numerical methods, such as adaptive-time stepping and implicit time-integration. However, this requires the iterative solution of a sequence of discrete linear systems at each time step. This is complicated by asymmetry of the discrete system, originating from the advection of the flow. Here, we explore strategies for the efficient simulation of the nonlinear flow during individual precipitation events when modelling vegetation dynamics over centuries.
How to cite: Kästner, K. and Hinz, C.: Efficient and realistic modelling of individual runoff events in ecohydrological systems , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9937, https://doi.org/10.5194/egusphere-egu25-9937, 2025.
