Small natural features (SNFs) are small landmarks that differ in their abiotic characteristics from the surrounding landscape. SNFs, such as road verges, midfield islets, rocky outcrops and ancient burial mounds, provide safe havens for grassland specialist species in human-modified landscapes; therefore, their great ecological importance is in contrast to their small size. SNFs often have a high topographical heterogeneity and a related high variability in abiotic conditions; therefore, they provide a unique opportunity for establishing links between environmental heterogeneity (EH) and biodiversity. We investigated the EH components of topographically heterogeneous SNFs in a comprehensive framework, by linking environmental and biotic parameters. We studied ancient millennia-old burial mounds built by nomadic steppic tribes that are covered by semi-natural grasslands in the Pannonian (Hungary) and Continental (Bulgaria) biogeographical regions. We designated 16 study sites, each containing a few-metre-high mound with five microsites (top, north-, east-, south- and west-facing slopes) and a nearby plain grassland. At each microsite, we measured soil moisture, soil chemical properties, solar radiation and microclimate; and recorded the list and cover of vascular plants in a total of 480 plots. On the mounds, topographical heterogeneity was associated with sharp differences in microclimate and soil properties. Besides the contrast between mild north-facing and harsh south-facing slopes, east- and west-facing slopes also sustained unique microsites characterised by dynamic diurnal changes in air temperature and vapour pressure deficit. Various combinations of the EH components resulted in unique plant species compositions within the microsites, and supported the co-occurrence of species typical of contrasting habitat types, even within a couple of metres. By combining high-resolution measurements of abiotic factors with fine-scale vegetation sampling, our study provides evidence that widespread SNFs with complex topography harbour several grassland-specialist plant species and introduce a high level of EH to otherwise homogeneous plain landscapes, which cover one third of the global land area.

How to cite: Deák, B., Kovács, B., Rádai, Z., Apostolova, I., Kelemen, A., Kiss, R., Lukács, K., Palpurina, S., Sopotlieva, D., Báthori, F., and Valkó, O.: Heterogeneity in microclimate and soil parameters support diverse and unique vegetation on small natural features, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-598, https://doi.org/10.5194/egusphere-egu21-598, 2021.

Many grass-dominated ecosystems in dryland regions have experienced increasing woody plant density and abundance during the past century. An example is the Chihuahuan Desert in the southwestern US, which experienced different stages of shrub encroachment in the past 150 years. We synthesize recent developments in the roles and feedbacks of abiotic and biotic drivers of shrub encroachment in the Chihuahuan Desert using an ecosystem dynamics context through intercomparison of Long Term Ecological Research (LTER) sites. Experimental and modeling studies support a conceptual framework which underscores the roles of erosion and fire in woody plant encroachment. Collectively, research at the Jornada LTER provided complementary, quantitative support to the well-known fertile-islands framework. Studies at the Sevilleta LTER expanded the framework, adding fire as a major disturbance to woody plants. Conceptual models derived from the synthesis may guide management interventions aimed at reducing or mitigating undesirable ecosystem state change elsewhere in the world.

How to cite: Li, J. (., Ravi, S., Wang, G., Van Pelt, S., Gill, T., and Sankey, J.: Woody plant encroachment in southwestern US: Drivers, feedbacks, and conceptual models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2995, https://doi.org/10.5194/egusphere-egu21-2995, 2021.

Turkey, also known as Asia Minor, comprising largely of the Anatolian peninsula/plateau is situated in a distinct spot, surrounded by marine basins on three sides and an inner sea, coastlines on the northern and southern parts of the country cut off from the inner plateau by high mountain ranges showcasing different micro-climatic settings. The area, a natural corridor between two continents, also harbors a heavy human footprint on its terrestrial vegetation cover, having been populated since the Paleolithic and harvested at capacity since the Neolithic. Yet, despite continuous anthropogenic influence, the diverse climatic variables coupled with striking differences in geomorphology, including soil diversity, still translate into visibly diverse regional vegetation patterns in the northern and southern coastal highlands of the country, with respect to altitude. Due to its special place at the juncture of three flora regions, the peninsula also boasts a large endemic plant diversity, at a striking 30%, the highest yet in all of Europe.

The mountain ranges on the coastal regions in the Anatolian plateau extend parallel to the coastline in the North and South in sets of quasi-parallel “lines”, and perpendicular in the West. This geomorphologic set-up coupled with the differentiating effect of the sea also contributes to the distribution of terrestrial vegetation.

In this study, terrestrial vegetation in selected patches located on different mountain ranges where the anthropogenic effects are minimal (Küre and Kaçkar Mountains from the Black Sea coast with diverse geomorphologies, both hosting national parks, and Amanos Mountains as well as select transects from the Western Taurus range) is simulated using a coupled dynamic vegetation model and an ecosystem simulator, LPJ-GUESS. The model is run with reanalysis data for the static phase, and with different global circulation model outputs to forecast the potential impacts of changes in climatic drivers, such as atmospheric carbon levels, temperature, and precipitation on the key forest species in Turkey.

Turkey’s terrestrial ecosystems under future RCP scenarios have not been modelled using high-resolution data before. The preliminary findings of our simulations show suggested changes in landcover for the region as a whole. One expected outcome, in the face of rising global temperatures and aridity concerns for Turkey overall but for the Southwest in particular, is a general northerly, and in instances a north-easterly shift in key forest species with changes in forest cover and density. This study will also help us determine which climatic drivers will become more critical in the near future for the region from a terrestrial ecosystem perspective and in terms of ecological changes in real time. As Turkey still harbors remnants of old-growth forests, we strongly believe it is crucial and urgent to identify the climatic and anthropogenic challenges that lie ahead in their conservation and restoration.    

This study has been produced benefiting from the 2232 International Fellowship for Outstanding Researchers Program of the Scientific and Technological Research Council of Turkey (TUBITAK) through grant 118C329. The financial support received from TUBITAK does not mean that the content of the publication is approved in a scientific sense by TUBITAK.

How to cite: Ekberzade, B., Yetemen, O., Sen, O. L., and Dalfes, H. N.: Terrestrial ecosystem range shifts in a changing climate – preliminary findings from a spatio-temporal comparison of mountain ranges from Turkey using LPJ-GUESS, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7794, https://doi.org/10.5194/egusphere-egu21-7794, 2021.

The concept of local-scale interactions of spatially periodic vegetation patterns are well known in arid and semi-arid regions. The vegetation patterns are easily observable from aerial and satellite photography. Additionally, various mathematical models have been developed to reproduce the patterns observed in nature, aimed towards understanding the driving factors leading to pattern properties. Several studies exist attempting to analyse spatial properties of these patterns, their spatial distribution and their relationship to  topography and climate. However, there are limitations in how these studies provide spatially-distributed statistics, and on the specifics of vegetation patch and band geometries, making it difficult to compare to model predictions. 

This study proposes  a new workflow (implemented in R) to measure geometric  characteristics of vegetation bands and patches. We use high-resolution satellite imagery as the base dataset. Color filters are used to binarise and identify individual patches/bands of arbitrary irregular shapes. We then compute different geometrical properties, such as  patch-size, separation between them, orientation, among others. Additionally, the principal axes of each patch/band are identified, and used to measure characteristic lengths and widths, for which statistics are then computed, and can be represented in spatial subdomains to allow for spatial analysis at different scales. The strategy can also be easily applied to modelling results, thus facilitating comparison, and the algorithm is flexible enough to yield different forms of patterns and spatial extent.

As a test case, we apply this workflow to a study site (11.05 N, 28.35 E) in Kordofan, south Sudan (a region previously reported and documented in the literature), using Google Earth Imagery as input. For this domain (3500 x 1400 m), the  results show that the length of the patches has a strong positive correlation with their width. Additionally, the length and the average nearest neighbor distance displayed a small positive correlation to the elevation. Using the available ALOS topography, the results also confirm that that 92% of the bands in our study area are oriented perpendicularly to the slope direction, as is expected from these systems. 

This test is a first step into applying this workflow to a larger extend within Kordofan and other regions known to exhibit vegetation bands (tiger bush in wester Africa, Australia, Nevada) and perform extensive geometric and spatial analysis of the bands, as well as simulated banded systems obtained from numerical models.

Keywords: Vegetation patterns, Self-organization, Tiger-bush, Geometric analysis, Oriented direction

How to cite: Hinz, C., Nengsuwan, K., and Cavieds-Voullieme, D.: Spatial analytics of self-organized vegetation pattern in semi-arid regions: an example on tiger-bush patterns in Sudan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10102, https://doi.org/10.5194/egusphere-egu21-10102, 2021.

Drylands are one of the largest biomes over the Earth, covering around 40% of land surface. These are water limited ecosystems where vegetation occupies the most favourable positions over the landscape. Less favourable areas are frequently covered by other biotic and abiotic components such as biological soil crusts, bare soil, or stones. During most rainfall events, runoff is generated in open areas (runoff sources) and redistributed through vegetation patches (runoff sinks), therefore increasing water and nutrient availability for plants. Water redistribution feedbacks determine vegetation coverage and productivity, modulate changes in its spatial distribution, and could ameliorate the predicted negative effects of climate change over these ecosystems.

The principal aim of this study was to quantify the impact of water redistribution processes on vegetation performance, and to evaluate how this effect varies in response to aridity. To achieve it, we analysed the relationships between runoff redistribution from open areas and vegetation productivity, by combining satellite information on vegetation state and topography. More precisely, we calculated Normalized Difference Vegetation Index (NDVI) dynamics during three hydrological years in 17 study sites along an aridity gradient in the SE of the Iberian Peninsula using SENTINEL 2 images. Then we used a DEM and a high spatial resolution vegetation map to derive a water redistribution index that simulate source-sinks interactions between vegetation and open areas. Finally, we analyse the relationship between, potential water redistribution and vegetation dynamics and how it varies along the aridity gradient.

We found a non-linear relationship between potential water redistribution and vegetation productivity. Overall, vegetation NDVI increases as potential water redistribution did, which demonstrated the importance of water redistribution processes on drylands vegetation performance. However, vegetation capacity to retain runoff water is limited and there is a clear threshold above which increased potential water redistribution does not promote vegetation productivity. Thresholds are caused by the limit capacity of vegetation to infiltrate run off when preferential flows are forming, increasing ecosystem connectivity, and involving local water losses for vegetation.  Therefore, an increase in open areas between vegetation patches could have a positive effect over vegetation through hydrological connectivity but until to a certain point in which global connectivity supposed water losses for plants. This process could have important effects under climate change, by controlling the resistance and resilience of vegetation in drylands ecosystems.

Acknowledgements. This research was supported by the FPU predoctoral fellowship from the Educational, Culture and Sports Ministry of Spain (FPU17/01886) REBIOARID (RTI2018-101921-B-I00) projects, funded by the FEDER/Science and Innovation Ministry-National Research Agency, and the RH2O-ARID (P18-RT-5130) funded by Junta de Andalucía and the European Union for Regional Development.

How to cite: Rodríguez Lozano, B., Rodriguez-Caballero, E., and Cantón, Y.: Open areas in patchy ecosystems: key spaces for vegetation survival., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15022, https://doi.org/10.5194/egusphere-egu21-15022, 2021.

The Brazilian semiarid have a diversity of soils and parent material, and this influences its flora. We observed different landscapes, and we revised papers about the vegetation surveys and their relationship with the landscape elements and their evolution. Brazil's semiarid area is between average latitudes 2º and 17º South, and longitudes 35º and 46º West, on the same latitude position of Amazon Forest and Savanna biomes, and one of the few sub-equatorial dryland regions. The semiarid biome is named Caatinga and characterized by Seasonally Dry Forests and Woodlands (SDFW), one of Brazil's most degraded and least studied biomes. It was considered low in species diversity and endemism for a long time, mainly because of the semiarid climate and low research quantities. Recent studies indicated high biodiversity, surpassing the Amazon concerning the number of plant species per area. The landscape presents vast rocky pediments scattered with Proterozoic crystalline massifs and elevated sedimentary basins forming table-like plateaus. Caatinga shows an average annual rainfall of around 600mm/year; marked by seasonal irregularity, the dry season occurs between August and October, and the rainy season concentrates during the summer. Orography effects are significant, and in the higher areas such as Plateaus, the precipitation can exceed 1000mm/year, and the lack of rainfall is distributed among depressions. Dry conditions started in the Miocene when the SDTFW arrived at the Brazil northeastern by connecting with two large SDTFW of South America. The crystalline shield is the basement of the Sertaneja Depression and the Borborema Plateau, both own soils related to semiarid conditions like Luvisols, Planosols, Phaeozems, Vertisols, and shallow soils, besides Lixisols at the colluvium materials at the foot of the hills.  These soils are mainly above granites, gneisses, and schists exposed during the notching of the Sertaneja surface, with some elevated areas by most resistant rocks. These areas harbor the most typical SDTFW of the Caatinga with deciduous and spiny woodlands or small forests, in the high altitude also influenced the vegetation assembly. On the Sedimentary regions, distinct floristic communities show seasonal dynamics not controlled exclusively by the rainfall supply; at least 50% of them maintain their leaves throughout the year. Flora presents independent events of ecological speciation over the last 1,5 Ma. Predominant soils are Ferrasols and Arenosols; the latter, in some cases, may represent an advanced stage of the Ferrasol with high clay loss. These soils did not form under current climatic conditions as they demand more and regular precipitation. We noted the close relationship between parent materials, soils, and vegetation controlling the landscape characteristics and their time and space evolution.

How to cite: Alves, G.: Dryland landscapes in Brazil: the relationship between soils and vegetation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12761, https://doi.org/10.5194/egusphere-egu21-12761, 2021.

Textural layering of soil plays an important role in distributing and regulating resources for plants in many semiarid and arid landscapes. However, the spatial patterns of textural layering and the potential effects on soil hydrology and water regimes are poorly understood, especially in arid sandy soil environments like the desert-oasis ecotones in northwestern China. This work aims to determine the distribution of textural layered soils, analyze the effects of different soil-textural configurations on water regimes, and evaluate which factors affect soil water infiltration and retention characteristics in such a desert-oasis ecotone. We measured soil water content and mineral composition in 87 soil profiles distributed along 3 transects in the study area. Constant-head infiltration experiments were conducted at 9 of the soil profiles with different texture configurations. The results showed that textural layered soils were patchily but extensively distributed throughout the study area (with a combined surface area percentage of about 84%). Soil water content in the profiles ranged from 0.002 to 0.27 g/cm³ during the investigation period, and significantly and positively correlated with the thickness of a medium-textured (silt or silt loam) layer (P < 0.001). The occurrence of a medium-textured layer increased field capacity (FC) and wilting point (WP), and decreased available water-holding capacity in soil profiles. Burial depth of the medium-textured layer had no clear effects on water retention properties, but the layer thickness tended to. In textural layered soils, smaller water infiltration rate and cumulative infiltration, and shallower depths of wetting fronts were detected, compared with homogeneous sand profiles. The thickness and burial depth of medium-textured layers had obvious effects on infiltration, but the magnitude of the effects depended on soil texture configuration. The revealed patterns of soil textural layering and the potential effects on water regimes may provide new insight into the sustainable management of rainfed vegetation in the desert-oasis ecotones of arid northwestern China and other regions with similar environments around the world.

How to cite: Sun, C., Zhao, W., Liu, H., Zhang, Y., and Zhou, H.: Effects of textural layering on water regimes in sandy soils in a desert-oasis ecotone, Northwestern China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9324, https://doi.org/10.5194/egusphere-egu21-9324, 2021.

Rocky desertification induced by severe deforestation has caused the water loss and soil erosion in karst regions in southeast China, limiting local social and economic developments. To prevent further rocky desertification, the farmland which had obtained by deforestation were abandoned for recovery. As soil quality improved by agriculture abandonment should be examined, it is necessary to investigate the dynamics of physical and chemical properties of soil in different ages after abandonment. In this study, 38 investigation sites were selected for soil sampling on the slopes in Longtan trough valley in Youyang County, Chongqing Municipality, China. The dominant plant species of the investigation sites were also noted during soil sampling. The sites were divided into seven age classes according to their abandonment time. Dynamics of water content, bulk density, pH, and concentration of available potassium, available phosphorus, available nitrogen, total nitrogen and organic matters were examined. It suggests that soil quality might be deteriorated right after abandonment and then improved from around 20 years after abandonment. Deterioration of soil quality may be induced by lack of plant coverage and exposure of rock outcrops which may accelerate water loss and swelling and shrinkage cycles of soil. After the formation of plant communities and litter layer above the ground, soil quality was then apparently improved. These findings can provide a potential guideline for recovery management in karst regions in southwest of China.

How to cite: Wang, K., Wang, Z., Wang, J., Li, J., Sun, B., Yang, H., and Zhang, P.: Dynamics of physical and chemical properties of soil after agricultural abandonment in a karst region in Southwest China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10468, https://doi.org/10.5194/egusphere-egu21-10468, 2021.

A physically-based model for soil-plant-atmosphere continuum (SPAC) is parameterized and evaluated against field-measured physiological responses of a desert shrub, Haloxylon Ammodendron (HA), to rainfall pulses in a desert environment in northwestern China. Despite its simplicity, the model was successfully employed to assess the complexity and uncertainty involved in the physiological responses of HA following pulsed rainfall events. Through modelling efforts, we report a systematic evaluation of the non-linear relationship between the physiological responses of HA and pulse magnitude or antecedent moisture. The results show that following the rainfall pulses, the modeled daily transpiration and assimilation rates either stayed the same or decreased monotonically with water stress. However, the stomatal conductance (g_s) and photosynthetic rate (A_n) responses were relatively weaker when compared to the increase in water potential. We found that rainfall events with <5 mm cannot induce any substantial response of A_n (Δ<4μmol m^-2s^-1), and at least 13 mm of rain is required to increase A_n by 10 μmol m^-2s^-1. Significant responses of water use efficiency (WUE) were not even discernible from viewing the simulation. Our analysis reproduced the judgements with a certain uncertainty that HA is basically a kind of drought resistant species, it tends to have a more conservative water-use strategy and thus a safer photosynthetic behavior. The inverse–texture hypothesis is much more clearly supported by the modeling experiments, suggesting that soil texture drives differences in the effects of pulses on the magnitude and sensitivity of the physiological responses of plants, and the interaction between rainfall and soil texture may lead to the preferred acquisition and use of pulsed precipitation by HA. The modelling work and findings in this study is likely to shed light on the quantitative understanding of the physiological behavior of other plants in water-limited environments.

How to cite: Wu, C., Liu, H., Yu, Y., and Zhao, W.: Modeling the Physiological Responses of a Desert Shrub to Rainfall Pulses in an Arid Environment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14338, https://doi.org/10.5194/egusphere-egu21-14338, 2021.

Abstract: Wetlands remaining in the arid inland river landscapes of northwestern China suffer degradation and their resilience and ability to continue functioning under hydrologic and land use changes resulting from climate change may be significantly inhibited. Information on the desert-oasis wetlands, however, is sparse and knowledge of how ecological functioning and resilience may change under climate change and water-resource management is still lacking. Research in oasis wetland areas of the Northwestern China identified linkages between subsurface flow, plant transpiration, and water levels. In this study, we present an ecohydrological analysis of the energy and water balance in the wetland ecosystem. A process-based stochastic soil moisture model developed for groundwater-dependent ecosystems was employed to modelling the interactions between rainfall, water table fluctuations, soil moisture dynamics, and vegetation, and to investigate the ecohydrology of arid inland wetlands system. Field measured groundwater levels, vertical soil moisture profiles, soil water potentials, and root biomass allocation and transpiration of pioneer species in the wetlands were used to calibrate and validate the stochastic model. The parameterized model was then running to simulate the probability distributions of soil moisture and root water uptake, and quantitative descript the vegetation–water table–soil moisture interplay in the hypothesized scenarios of future. Our analysis suggested the increasing rates of water extraction and regulation of hydrologic processes, coupled with destruction of natural vegetation, and climate change, are jeopardizing the future persistence of wetlands and the ecological and socio-economic functions they support. To understand how climate change will impact on the ecohydrological functioning of wetlands, both hydrological and land use changes need to be considered in future works.

Keywords: Wetland ecosystem, groundwater, soil moisture dynamics, water balances, Heihe River Basin

How to cite: Li, L., Liu, H., Yu, Y., and Zhao, W.: Modelling the Hydrologic Regime of Arid Inland Wetlands: Non-linear Relationship Between Root-uptakes of Water and Underground Water Table, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13997, https://doi.org/10.5194/egusphere-egu21-13997, 2021.

The joint-research project "Gute Küste Niedersachsen" is a multidisciplinary approach across spatial and temporal scales investigating ecosystem services for coastal protection. Current national coastal protection concepts predominantly target flood protection and rarely consider additional benefits to coastal ecosystems or vice versa. How maritime landscapes, such as salt marshes, coastal white dunes or a diversification of dike vegetation, can be integrated into approaches of coastal protection without compromising protection levels is the driving question in "Gute Küste Niedersachsen" and heeds recent European Framework directives calls for the restoration of a good ecological status. An in-depth understanding of dynamics within coastal ecosystems, covering eco-hydrodynamics and eco-geomorphodynamics is developed in real world laboratories at the German North Sea coast, as part of the project.
Systematic field observations in collaboration between biologists, geo-ecologists and coastal engineers are conducted to identify seasonal changes of vegetation regarding zonation, height, root length density and bio-mechanical parameters like bending stiffness or tensile strength. The differences of bio-mechanical vegetation traits from specific plant species, e.g. the European beach grass Ammophila arenaria, will indicate differences in bio-stabilization states.
Complementary field data of topography and soil parameters, e.g. shear and pull-out resistance, among other parameters, are acquired, employing specifically developed instrumentation like the DiCoastar for automatic and digital measurements of shear resistance over rotation angle. Additionally, values such as water and biomass content obtained from soil samples help to elucidate erosion stability of coastal ecosystems.
Field campaigns are focused on two real world laboratories, the tidal barrier island of Spiekeroog, Germany, and a coastal mainland section. Spiekeroog offers a variety of dune systems exposed to divergent environmental conditions such as established and recently developing natural dunes at the north-eastern coast, dunes that are used for coastal protection at the north-western coast, dunes in combination with a sea wall that are already supported by sand nourishment at the western coast or established dunes along the south-western tip of the island. Furthermore, the island holds a unique setting with an engineered dune, which was created to integrate a dike system into the landscape. This offers a one-of-a-kind opportunity to investigate differences between six different dune system types within close proximity regarding their vegetation bound bio-mechanical properties and linked soil-bound erosion resistance.
In addition, Spiekeroog offers an abandoned dike line, for which a sectional re-planting is rolled out with alternative seed combinations for ecologically upgrading grass dikes and boost plant diversity while coastal protection is maintained. A direct comparison against a sea dike is made at the second real world laboratory situated at the adjacent mainland coast. This setting facilitates the comparison between different biological revetment types and their respective performance in coastal protection regarding wave-soil-vegetation interactions.
In a subsequent step, the extensive data set will be used to develop surrogate plant models and mimic nature in hydraulic laboratories and numerical simulations to project system performance under climate change scenarios. Finally, technical guidance as well as policy recommendations will be derived for enhancing ecosystem services of artificial structures for coastal protection.

How to cite: Kosmalla, V., Schönebeck, J.-M., Mehrtens, B., Keimer, K., Paul, M., Lojek, O., Schürenkamp, D., and Goseberg, N.: Soil-vegetation interactions in coastal landscapes - erosion reduction as ecosystem service in the context of integrated coastal zone management, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8324, https://doi.org/10.5194/egusphere-egu21-8324, 2021.

High mountainous areas are are strongly shaped by redistribution processes of sediments and soils. Due to the projected climate warming and the continued retreat of glaciers in the 21^st century, we can expect the area of newly exposed, highly erodible sediments and soils to increase. While soil and vegetation development is increasingly well understood and quantified, it has rarely been coupled to soil erosion. The aim of this study was to assess how soil erosion rates change with surface age. We investigated two moraine chronosequences in the Swiss Alps which were situated in a siliceous and calcareous lithology and spanned over 30 – 10’000 yrs and 110 – 13’500 yrs, respectively. We used ^239+240Pu fallout radionuclides to quantify the average soil erosion rates over the last 60 years and compared them to physico−chemical soil properties and the vegetation coverage. At both chronosequences, the erosion rates were highest in the young soils. The erosion rates decreased markedly after 3−5 ka of soil development to reach a more or less stable situation after 10−14 ka. This decrease  goes hand in hand with the development of a closed vegetation cover. We conclude that depending on the relief and vegetational development, it takes up to at least 10 ka to reach soil stability. The establishment of a closed vegetation cover with dense root networks appears to be the controlling factor in the reduction of soil erodibility in periglacial areas.

How to cite: Musso, A., Ketterer, M. E., Greinwald, K., Geitner, C., and Egli, M.: Quantification of soil erosion (using 239+240Pu) on periglacial chronosequences reveals the importance of vegetation cover in soil stabilisation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10832, https://doi.org/10.5194/egusphere-egu21-10832, 2021.

Recent detailed investigations of landforms, soils and surface deposits of the Borisoglebsk Upland northeastern slope within the Nero Lake basin (Central European Russia, Yaroslavl Region) allowed deciphering co-evolution of the major landscape components of the case study area since the Late Pleistocene. The Late Pleistocene to Holocene transition in the gully network was represented by relatively short but high-magnitude (up to 12 m) incision phase followed by significant infill till 6.5 ka. Absence of the well-developed early Holocene paleosols in the studied sections and cores suggests dominantly negative sediment budget. There is so far limited evidence of sedimentation over the first half of the Holocene. Discontinuous deposition with certain interruptions (but without distinct buried soil formation) occurred only within closed depressions and on gully fans. The second part of the Holocene prior to the widespread human settlement left more substantial traces in soil and sediment record. Despite the common perception of the pristine boreal forest landscapes to be geomorphologically stable due to erosion-protective role of woodland vegetation, several phases of dramatically increased soil and gully erosion rates have been identified. It is identified in soil bodies and sediments, both at locations dominated by denudation (evidences of multiple topsoil truncation in Atlantic and Subatlantic) and at zones of alternating incision and infill of small linear erosion features. Such extremes were most likely associated with combination of several triggers including natural forest fires and high-magnitude rainfall or snowmelt runoff events. There are several ¹⁴C dated layers of pyrogenic charcoal indicating pre-anthropogenic wildfire-induced incision and infill cycles during the middle and late Holocene.

The last phases of increased hillslope and fluvial activity within the study area can be related to increased human interference, starting from about 1600-900 years ago. The onset of cut-and-burn cultivation is independently established from available archeological evidences, dating of cut and burnt tree logs remnants, organic material buried by agrogenic colluvium and gully fans. Latest period of intensive gully growth can most likely be attributed to the XIX^th Century land tenure reform, when most of the study area gullies experienced significant linear growth, bottom incisions and appearance of several new gully branches. The most recent trend of soil and gully erosion has been evaluated by ¹³⁷Cs sediment tracing, soil empirical modeling and comparison of historical and modern maps, airborne photos and satellite images. Rates of soil redistribution on slopes decreased significantly over the last several decades due to combination of natural and anthropogenic impacts: 1) decreased spring snowmelt runoff caused mainly by generally lowered thickness of seasonally frozen topsoil layer; 2) arable land abandonment or shift from row crops and cereals to perennial grass-dominated crop rotations in the post-Soviet period. In addition, local short-term (from several years to within-year) cycles of relatively low-magnitude (not exceeding ±1 m range) incision and infill in gullies are often triggered by biogenic activities, namely beaver dam constructions and breaches and local log jams.

The study is supported by the Russian Science Foundation (Project No. 19-77-10061) and Russian Foundation for Basic Research (Project No. 19-29-05238).

How to cite: Belyaev, V., Shorkunov, I., Garankina, K., Mergelov, N., Shishkina, Y., Lobkov, V., Semochkina, A., and Van, V.: Holocene history of boreal forest landscapes of the Central European Russia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14681, https://doi.org/10.5194/egusphere-egu21-14681, 2021.

Vegetation protects soil against erosion by intercepting rain, increasing flow resistance, promoting soil infiltration and improving soil strength. However, the representation of vegetation dynamics in Landform Evolution Models (LEMs) is very simplified, which could result in over/under estimations of erosion rates. Here we use a new model framework to study the differences in erosion rates when considering different processes associated with vegetation protection. We analysed the changes in erosion rates by considering: (1) the effect of root biomass on soil erodibility, (2) the effect of leaf cover on soil diffusivity, (3) the effect of litter on flow resistance, and (4) the effect of soil carbon on soil infiltration. We implemented the model in an open-forest savannah catchment situated in Howard Springs (Northern Territory, Australia) and ran simulations using daily time step for 100 years. The modelling framework comprises a coupled Landform Evolution Model (LEM) with dynamic biochemical vegetation and biomass pools dynamics. Our results show that bare soil conditions generate a 100% increase in erosion compared to those using the full dynamic vegetation (that include protection from all carbon pools). We find that the effects from vegetation protection and rainfall are asynchronous, with substantial vegetation growth typically lagging behind substantial rainfall events. This means that rainfall events at the beginning of the rainy season contribute heavily to erosion. For the specific case of Howard Springs, leaves and roots are the most important factors that control erosion except when they are not fully recovered after the dry season. At this time the effect of the litter, and to a lesser extent the soil carbon, turn out to be determinant. Overall, this study highlights the importance of including dynamic vegetation and the effects of the biomass pools on controlling erosion in order to estimate erosion rates.

How to cite: Quijano Baron, J., Saco, P., and Rodriguez, J.: Asynchronous effects of vegetation protection on landform evolution, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14037, https://doi.org/10.5194/egusphere-egu21-14037, 2021.