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The northern Nyainqêntanglha range on the southern Tibetan Plateau reaches an elevation of 7150 m and is mainly characterized by a periglacial landscape. A monsoonal climate, with a wet period during the summers and arid conditions during the rest of the year governs the landscape processes. Large parts of the mountain range are considered permafrost due to the high altitude and the associated low air temperature. Rock glaciers, which are bodies of ice-rich debris, are a typical landform. The recently published IPCC report on the cryospheres of high mountain areas highlights the sensitivity of rock glaciers to climate warming and emphasizes the importance of their study.We study the distribution of rock glaciers of the northern Nyainqêntanglha range and our aim is to produce an inventory of active rock glaciers based on their surface motion characteristics. The lack of higher order vegetation and the relatively low winter precipitation enable us to employ Interferometric Synthetic Aperture Radar (InSAR) time-series techniques to study both seasonal and multi-annual surface displacement patterns. InSAR is a powerful microwave remote sensing technique, which makes it possible to study displacement from a few millimeters to centimeters and decimeters per year. It is thus suitable to detect sliding and creeping processes related to periglacial landscapes and permafrost conditions on the Earth’s surface. We use both Sentinel-1 (2015-2019) and TerraSAR-X ScanSAR data (2017-2019) for our analysis.In this study we differentiate rock glaciers from the surrounding seasonally sliding slopes by their significantly higher surface creeping rates with mean velocities of 5–20 cm yr-1. We also observe that the velocity of rock glaciers is less dependent on the summer monsoon, which allows us to further differentiate between rock glaciers and other landforms. This method could potentially be used to create rock glacier inventories in other remote regions, as long as the snow cover in winter is thin enough to allow continuous InSAR time-series analysis. These rock glacier inventories are necessary to assess the effects of climate change on vulnerable high mountain regions.

Soil erosion is a frequently tackled field of research and plays a major role in land degradation. Representing a discontinuous process soil loss is strongly determined by single events, which leads to high demands on modelling approaches.Here we present a first application of the physically-based soil erosion model EROSION3D in a South African setting within the framework of the project SALDi (South African Land Degradation Monitor). Parameterization of the model requires intensive field work in accordance to land use and management patterns, soil types and topography. The experimental determination of physical and hydrological processes for selected sites allows for an improvement of the modelling results. Thus, rainfall and runoff simulation campaigns were carried out on various sites with a 3 x 1 m² mobile rainfall simulator. Additionally, UAV and TLS surveying, soil sampling, laboratory analysis and digital soil mapping complemented the approach. The created datasets are firstly handled in EROSION2D to calibrate soil erosivity and hydraulic conductivity and then introduced to EROSION3D for including land use, precipitation, elevation, multi-layered soil properties, organic carbon content and additional model input parameters.The modelling procedure was applied within the boundaries of a research catchment close to Ladybrand in the Free State for first test runs. Furthermore, the same approach showed distinct differences on a conventionally tilled field vs. a conservational approach. An upscaling to larger catchments will then be carried out in basins with protected soils within Kruger National Park to directly compare them to results from intensively cultivated agricultural sites adjacent to the park boundaries.

Soils and sediments can be distinguished based on “composite fingerprints”, i.e., sets of physical and chemical properties that are suitable for discrimination. At present, statistical stepwise variable selection methods are frequently applied to identify composite fingerprints, although they have been seriously criticized. Here, we test regularized logistic regression (RLR) as an alternative approach in the context of a reservoir siltation study where the post-dam facies is to be distinguished from the pre-dam facies. The pre- and post-dam facies of four reservoirs located in the Kruger National Park were examined with respect to grain size composition, color, and content of calcium-lactate leachable phosphorus (P CAL). A composite fingerprint was identified applying RLR to training data. The fitted regression model was used for the classification of samples not involved in the training dataset. For comparison, variable selection was performed with stepwise discriminant function analysis (DFA) and samples were classified by applying linear discriminant analysis (LDA). Both approaches were validated by comparing field interpretation and classification results. The analysis was extended based on Monte Carlo simulations and synthetic datasets to quantify uncertainties and to enhance the method comparison. RLR and stepwise DFA identify grain size parameters and P CAL content to be particularly useful for the facies discrimination. Neglecting and taking into account a potential sampling bias, both approaches lead to ≤3 and 5% misclassifications, respectively. RLR outperforms stepwise DFA/LDA in Monte Carlo simulations, although misclassification rates do not significantly differ (p = 0.84). RLR uses on average 12% less fingerprint properties. Moreover, RLR-derived probabilities of group membership represent a more reliable measure for classification conclusiveness than probabilities calculated from LDA, which is evident in significantly lower (p

High resolution Digital Elevation Models (DEM) represent fundamental data for a wide range of Earth surface process studies. Over the past years, the German TanDEM-X mission acquired data for a new, truly global Digital Elevation Model with unprecedented geometric resolution, precision and accuracy. First TanDEM Intermediate Digital Elevation Models (i.e. IDEM) with a geometric resolution from 0.4 to 3 arcsec have been made available for scientific purposes in November 2014. This includes four 1° × 1° tiles covering the Kruger National Park in South Africa. Here, we document the results of a local scale IDEM height accuracy validation exercise utilizing over 10,000 RTK-GNSS-based ground survey points from fourteen sites characterized by mainly pristine Savanna vegetation. The vertical precision of the ground checkpoints is 0.02 m (1σ). Selected precursor data sets (SRTMGL1, SRTM41, ASTER-GDEM2) are included in the analysis to facilitate the comparison. Although IDEM represents an intermediate product on the way to the new global TanDEM-X DEM, expected to be released in late 2016, it allows first insight into the properties of the forthcoming product. Remarkably, the TanDEM-X tiles include a number of auxiliary files providing detailed information pertinent to a user-based quality assessment. We present examples for the utilization of this information in the framework of a local scale study including the identification of height readings contaminated by water. Furthermore, this study provides evidence for the high precision and accuracy of IDEM height readings and the sensitivity to canopy cover. For open terrain, the 0.4 arcsec resolution edition (IDEM04) yields an average bias of 0.20 ± 0.05 m (95% confidence interval, Cl95), a RMSE = 1.03 m and an absolute vertical height error (LE90) of 1.5 [1.4, 1.7] m (Cl95). The corresponding values for the lower resolution IDEM editions are about the same and provide evidence for the high quality of the IDEM products across the different resolution classes. Compared to the selected precursor DSMs, TanDEM-X will provide elevation data not only with up to 2.5 times higher geometric resolution and a 5–10 times higher vertical accuracy clearly outperforming the LE90 ⩽ 10 m benchmark.

A 30.5 m sediment core was recovered from the coastal lake Eilandvlei (EV13), which represents a unique high-resolution record of environmental change for southern Africa. For the establishment of a robust chronology, special emphasis was placed on the calibration of radiocarbon ( 14 C) ages obtained from the dating of different material. However, the reliability of 14 C ages can be problematic since coastal lakes interact with different source pools providing 14 C-depleted (“old”) carbon thus causing reservoir effects. The origin of old carbon affecting the EV13 samples was most likely sourced from the Indian Ocean. Two pre-bomb marine molluscan shells were therefore analysed to determine the regional marine reservoir offset (ΔR), with obtained ΔR values of 134 ± 38 and 161 ± 38 14 C yrs providing the first available data for the south coast of South Africa. However, the application of the resulting average ΔR mean = 148 ± 27 14 C yrs for the calibration of the entire EV13 record underestimates the variable reservoir effects throughout the Holocene. These were possibly caused by past changes in the connectivity between the present lake system and the ocean as well as a varying degree of upwelling in this area. To solve this problem, three sample pairs (each consisting of wood fragments and bulk organic sediment from the same core depth) were dated to calculate the variable past reservoir effects. This approach provided a median basal age of 8920 +200 / -250 cal BP. Palaeomagnetic secular variation stratigraphy was used to corroborate the chronology for the topmost 1.5 m of the record (past millennium), thus providing the first Holocene sediment based inclination and declination data from South Africa.

We investigate the seasonal evolution of stratification in a deep (100 m), high-altitude (4,730 m a.s.l.) dimictic lake on the Tibetan Plateau using three years of observation of Nam Co. The lake is situated at relatively low latitude (30 °N) where it receives high solar radiative forcing (observed maximum daily average 400 W m−2), yet the annual average air temperature is close to 0 °C at this high altitude. These features make Nam Co distinct from most well-documented dimictic lakes, which are usually located at higher latitude and lower altitude. We classify seasonal stratification into six phases based on strength of stratification, surface temperature relative to the temperature of maximum density, ice-cover, and heat and mixing dynamics, which we use to compare Nam Co with better-documented, higher-latitude dimictic lakes. While the three warm stratification phases (i.e. when water is warmer than the temperature of maximum density) in Nam Co are relatively cold, they are otherwise similar to that observed in high-latitude dimictic lakes. Conversely, two of Nam Co’s cold stratification phases are distinct from that reported in high-latitude lakes. These two phases are characterized by the interplay between the relatively strong radiative forcing and surface heat flux, and include the following: 1) during fall turnover, persistent winds aided by radiatively driven convection prolong vertical mixing (i.e. turnover) and surface heat loss such that the entire water column cools well below the temperature of maximum density (as low as 1 °C); and 2) in contrast, under ice-cover with relatively little snow, the entire water column of the lake warms continuously due to through-ice solar radiative flux. The intense cooling and heating during these two phases counteract each other such that hypolimnetic temperature at spring turnover is similar to that observed in high latitude lakes. Our observations highlight the relative importance of radiatively driven convection on the seasonal stratification dynamics of Nam Co, and underscore that these dynamics must be considered when attempting to predict climate change impacts on high-altitude, low-latitude lakes, including the >1100, largely unstudied, lakes on the Tibetan Plateau.

South African coastal lake sediments provide an excellent opportunity to investigate environmental changes such as sea level and climate variability during the Holocene period. In this study we present a sediment record from the coastal lake Groenvlei located in the southern Cape region which is part of South Africa's year-round rainfall zone. In order to improve the understanding of palaeoenvironmental changes in this region, we provide a high-resolution multi-proxy data set derived from geochemical, mineralogical, isotopic and granulometric analyses. The age-depth model is based on 14C and 210Pb dating and reveals a basal age of 4210 + 200/− 120 cal BP. Differences in the mineralogical composition of deposited carbonates reflect changes in the past lake water chemistry, probably caused by variations in both sea level and climate. Compared to the present, mostly drier conditions and a greater marine influence due to a higher sea level are inferred for the period between 4210 and 2710 cal BP. However, the record also indicates the occurrence of short humid phases during this time, which were probably associated with heavy rainfall events. A transition layer was deposited between 2710 and 1210 cal BP, probably as a result of reworking of sediment. During this time, the lake passed through a major change finally turning into a freshwater system from at least 1210 cal BP until the present. Our data indicate that the marine influence on the lake decreased due to a lower sea level and climate became generally more humid after 1210 cal BP probably resulting in a greater lake-internal and -external bioproductivity. Based on a comparison with other palaeoenvironmental studies from South Africa, our record suggests a prevailing winter rainfall seasonality at the southern Cape coast between 4210 and 2710 cal BP and a stronger influence of summer rainfall from 1210 cal BP onwards.

Digital Elevation Models (DEM) represent fundamental data for a wide range of Earth surface process studies. Over the past years the German TanDEM-X mission acquired data for a new, truly global Digital Elevation Model with unpreceded geometric resolution, precision and accuracy. First processed data sets (i. e. IDEM) with a geometric resolution of 0.4 to 3 arcsec have been made available for scientific purposes. This includes four 1° x 1° tiles covering the Kruger National Park in South Africa. Here we document the results of a local scale IDEM validation exercise utilizing RTK-GNSS-based ground survey points from a dried out reservoir basin and its vicinity characterized by pristine open Savanna vegetation. Selected precursor data sets (SRTM1, SRTM90, ASTER-GDEM2) were included in the analysis and highlight the immense progress in satellite-based Earth surface surveying over the past two decades. Surprisingly, the high precision and accuracy of the IDEM data sets have only little impact on the delineation of watersheds and the calculation of catchment size. But, when it comes to the derivation of topographic catchment properties (e.g. mean slope, etc.) the high resolution of the IDEM04 is of crucial importance, if - from a geomorphologist’s view - it was not for the disturbing vegetation.

Plant functional characteristics may drive plant species richness effects on ecosystem processes. Consequently, the focus of biodiversity–ecosystem functioning (BEF) experiments has expanded from the manipulation of plant species richness to manipulating functional trait composition. Involving ecophysiological plant traits in the experimental design might allow for a better understanding of how species loss alters ecosystem processes. Here we provide the theoretical background, design and first results of the ‘Trait-Based Biodiversity Experiment’ (TBE), established in 2010 that directly manipulates the trait composition of experimental plant communities. Analysis of six plant traits related to resource acquisition and use were analyzed using principal component analysis of 60 grassland species. The resulting two main axes describe gradients in functional similarity, and were used as the basis for designing plant communities with different functional and species diversity levels. Using such an approach allowed us to manipulate different levels of complementarity in spatial and temporal plant resource acquisition. In contrast to previous biodiversity experiments, the TBE is designed according to more realistic scenarios of non-random species loss along orthogonal axes of species trait dissimilarities. This allows us to tease apart the relative importance of selection and complementarity effects on multiple ecosystem processes, and to mechanistically study the consequences of plant community simplification.

The southern Cape coast, South Africa, is sensitive to climate fluctuations as it is influenced by different atmospheric and oceanic circulation systems. Palaeoecological evidence of Holocene climate variations in this region is presently limited. Here, we present a lake sediment record spanning approximately the last 670 years from Eilandvlei, a brackish coastal lake situated mid-way between Cape Town and Port Elizabeth. The results from geochemical and sedimentological analyses point to an increase in minerogenic sediment input from the catchment starting around ad 1400. Changes in the seasonal distribution of rainfall during the Little Ice Age may have altered river discharge and increased erosion rates and fluvial sediment transport in pre-colonial times. A rising mean lake level, possibly associated with an altered water balance or relative sea-level rise, may offer an explanation for the deposition of finer sediments. After ad 1450, reduced burial flux of elements associated with autochthonous sediment formation may have resulted from ecological changes in Eilandvlei. Enhanced sedimentation rates, increasing carbon, nitrogen, phosphorous and biogenic silica concentrations, as well as high concentrations of proxies for allochthonous sediment input (e.g. aluminium, titanium, zirconium) point to increasing sediment and nutrient flux into Eilandvlei from the late nineteenth century onwards. The most likely factor involved in these recent changes is land-use change and other forms of human impact.

Human-induced soil erosion is a widespread phenomenon in South Africa, and soil erosion rates reported are among the highest in the world. In addition to human disturbance, unfavourable environmental conditions are mentioned to explain the situation. But data on ‘natural’ erosion from undisturbed sites are rare. This paper presents the first assessment of sediment yield as an integrate measure of erosion, deposition and sediment transport from five catchments located entirely within Kruger National Park (KNP). KNP has been spared from agricultural development for a century and represents a near to natural geo-ecosystem in the semi-arid savanna biome. Sediment yield estimates are based on a survey of post-dam deposits in five reservoirs located in the south-eastern part of KNP. Reservoir lifetime ranges from 40 to 60 years and the size of the catchments from 8 to 100 km2. The results show distinct relations of long-term average sediment yield (SY) and area-specific sediment yield (SSY) with catchment size. Despite the unfavourable semi-arid environmental conditions, SY is comparatively low. SY varies from 130 ± 45 t y−1 for the 8 km2 catchment to 1130 ± 230 t y−1 for the 100 km2 catchment. SSY is 55 ± 15 t km−2 y−1 for catchments of 12 ± 3 km2 and 11 ± 2·4 t km−2 y−1 for the 100 km2 catchment. The latter finding suggests that decrease of SSY with increasing catchment size is not attributable to human disturbance only. However, further research is necessary to improve and enlarge the database and to verify first results and hypothetical conclusions. Copyright © 2012 John Wiley & Sons, Ltd.

This paper presents a reconstruction of the former coastal estuaries of the Quarteira and Carcavai estuaries in southern Portugal based on sedimentological, geochemical and palynological analyses of Holocene sediment cores. The results show that each estuary developed differently, depending on the morphology of the palaeovalley, environmental conditions and especially the influence of the sea and the formation of barrier systems. Both estuaries were flooded between 7000 and 5500 cal BP by sea level rise and were almost completely filled by sediment by the beginning of the Roman occupation (226 BC/ 2176 cal BP). A clear change in sedimentological processes is evident in both estuaries between 5500 and 3000 cal BP and is interpreted as an erosion phase or evidence of high-energy events such as storms or tsunamis.

This paper discusses the range of lake level changes, using hydro-acoustic techniques and sediment core data for Lake Nam Co in Central Tibet (China). This second largest Tibetan lake is situated at an elevation of 4718 m a.s.l. Lake level changes with different high stands documented by beach remnants are widespread on the Tibetan Plateau and also in Lake Nam Co. They indicate significant changes in the hydrological system triggered by the monsoonal circulation. Using hydro-acoustic techniques submerged beach remains at approximately 10/15 m, 30 m, 45 m, 70 m and 95 m below present day lake level were detected, indicating a more negative water balance than today. The −10/−15 m lake level is dated to an age equal to the Little Ice Age. All deeper lake levels are assumed to have been formed prior to ∼10000 cal BP. Folded older sediments, detected in the hydro-acoustic profiles indicate a possible larger extent of the glaciers during or prior to the Last Glacial Maximum (LGM). This is followed by a low stand or even by possible desiccation of the entire lake basin during or after the LGM.

Increasing atmospheric CO 2 concentration and related climate change have stimulated much interest in the potential of soils to sequester carbon. In 'The Jena Experiment', a managed grassland experiment on a former agricultural field, we investigated the link between plant diversity and soil carbon storage. The biodiversity gradient ranged from one to 60 species belonging to four functional groups. Stratified soil samples were taken to 30 cm depth from 86 plots in 2002, 2004 and 2006, and organic carbon contents were determined. Soil organic carbon stocks in 0-30 cm decreased from 7.3 kg C m -2 in 2002 to 6.9 kg C m -2 2 in 2004, but had recovered to 7.8 kg C m 2 by 2006. During the first 2 years, carbon storage was limited to the top 5 cm of soil while below 10 cm depth, carbon was lost probably as short-term effect of the land use change. After 4 years, carbon stocks significantly increased within the top 20 cm. More importantly, carbon storage significantly increased with sown species richness (log-transformed) in all depth segments and even carbon losses were significantly smaller with higher species richness. Although increasing species diversity increased root biomass production, statistical analyses revealed that species diversity per se was more important than biomass production for changes in soil carbon. Below 20 cm depth, the presence of one functional group, tall herbs, significantly reduced carbon losses in the beginning of the experiment. Our analysis indicates that plant species richness and certain plant functional traits accelerate the build-up of new carbon pools within 4 years. Additionally, higher plant diversity mitigated soil carbon losses in deeper horizons. This suggests that higher biodiversity might lead to higher soil carbon sequestration in the long-term and therefore the conservation of biodiversity might play a role in greenhouse gas mitigation.

The use of optical remote sensing data for savanna vegetation structure mapping is hindered by sparse and heterogeneous distribution of vegetation canopy, leading to near-similar spectral signatures among lifeforms. An additional challenge to optical sensors is the high cloud cover and unpredictable weather conditions. Longwave microwave data, with its low sensitivity to clouds addresses some of these problems, but many space borne studies are still limited by low quality structural reference data. Terrestrial laser scanning (TLS) derived canopy cover and height metrics can improve aboveground biomass (AGB) prediction at both plot and landscape level. To date, few studies have explored the strength of TLS for vegetation structural mapping, and particularly few focusing on savannas. In this study, we evaluate the potential of high resolution TLS-derived canopy cover and height metrics to estimate plot-level aboveground biomass, and to extrapolate to a landscape-wide biomass estimation using multi-temporal L-band Synthetic Aperture Radar (SAR) within a 9 km2 area savanna in Kruger National Park (KNP). We inventoried 42 field plots in the wet season and computed AGB for each plot using site-specific allometry. Canopy cover, canopy height, and their product were regressed with plot-level AGB over the TLS-footprint, while SAR backscatter was used to model dry season biomass for the years 2007, 2008, 2009, and 2010 for the study area. The results from model validation showed a significant linear relationship between TLS-derived predictors with field biomass, p < 0.05 and adjusted R2 ranging between 0.56 for SAR to 0.93 for the TLS-derived canopy cover and height. Log-transformed AGB yielded lower errors with TLS metrics compared with non-transformed AGB. An assessment of the backscatter based on root mean square error (RMSE) showed better AGB prediction with cross-polarized (RMSE = 6.6 t/ha) as opposed to co-polarized data (RMSE = 6.7 t/ha), attributed to volume scattering of woody vegetation along river valleys and streams. The AGB change analysis showed 32 ha (3.5%) of the 900 ha experienced AGB loses above an average of 5 t/ha per annum, which can mainly be attributed to the falling of trees by mega herbivores such as elephants. The study concludes that SAR data, especially L-band SAR, can be used in the detection of small changes in savanna vegetation over time.

The focus of a new experiment, set up in Jena in spring 2002, are the effects of biodiversity on element cycles and the interaction of plant diversity with herbivores and soil fauna. The experimental design explicitly addresses criticisms provoked by previous biodiversity experiments. In particular, the choice of functional groups, the statistical separation of sampling versus complementarity effects, and testing for the effects of particular functional groups differ from previous experiments. Based on a species pool of 60 plant species common to the Central European Arrhenatherion grasslands, mixtures of one to 16 (60) species and of one to four plant functional groups were established on 90 plots (20 m × 20 m) with nested experiments. In order to test specific hypotheses 390 additional small-area plots (3.5 m × 3.5 m) were set-up. Exact replicates of all species mixtures serve to assess the variability in ecosystem responses. In a dominance experiment, the effects of interactions among nine selected highly productive species are studied. Each species is grown as monoculture replicated once. Effekte der Biodiversitat auf Elementkreislaufe und Wechselwirkungen der pflanzlichen Artenvielfalt mit Bodenfauna und Herbivoren stehen im Mitttelpunkt eines neuen Experiments, das im Fruhjahr 2002 in Jena eingerichtet wurde. Das Versuchsdesign berucksichtigt ausdrucklich die Kritik, die an den Aufbau fruherer Biodiversitatsversuche gerichtet wurde. Die Auswahl funktioneller Gruppen von Pflanzenarten, die statistischen Moglichkeiten, die Effekte des “Sampling” gegen Komplementaritat zu trennen sowie den Einflus funktioneller Gruppen zu uberprufen, unterscheiden dieses Experiment von fruheren Versuchen. Sechzig typische Pflanzenarten der zentraleuropaischen Frischwiesen (Arrhenatherion) bilden den Artenpool fur den Versuch. Auf 90 Flachen wurden Artenmischungen etabliert, die 1 bis 16 (60) Arten und 1 bis 4 funktionelle Gruppen dieser Pflanzenarten enthalten. Die Versuchsparzellen haben eine Grose von 20 m × 20 m, auf denen in genesteter Anordnung verschiedene Teilexperimente durchgefuhrt werden. Zusatzlich wurden 390 kleine Parzellen (3.5 m × 3.5 m) angelegt, um spezifische Hypothesen zu uberprufen. Alle Arten werden hier mit je einer Wiederholung als Monokulturen kultiviert. Identische Wiederholungen aller Artenmischungen sollen deren Variabilitat untersuchen. In einem Dominanz-Versuch werden die Effekte der Wechselwirkungen zwischen 9 ausgewahlten hochproduktiven Arten untersucht.

BackgroundInfiltration is a key process in determining the water balance, but so far effects of earthworms, soil texture, plant species diversity and their interaction on infiltration capacity have not been studied.Methodology/principal findingsWe measured infiltration capacity in subplots with ambient and reduced earthworm density nested in plots of different plant species (1, 4, and 16 species) and plant functional group richness and composition (1 to 4 groups; legumes, grasses, small herbs, tall herbs). In summer, earthworm presence significantly increased infiltration, whereas in fall effects of grasses and legumes on infiltration were due to plant-mediated changes in earthworm biomass. Effects of grasses and legumes on infiltration even reversed effects of texture. We propose two pathways: (i) direct, probably by modifying the pore spectrum and (ii) indirect, by enhancing or suppressing earthworm biomass, which in turn influenced infiltration capacity due to change in burrowing activity of earthworms.Conclusions/significanceOverall, the results suggest that spatial and temporal variations in soil hydraulic properties can be explained by biotic processes, especially the presence of certain plant functional groups affecting earthworm biomass, while soil texture had no significant effect. Therefore biotic parameters should be taken into account in hydrological applications.

In order to predict which ecosystem functionsare most at risk from biodiversity loss, meta-analyses havegeneralised results from biodiversity experiments overdifferent sites and ecosystem types. In contrast, comparingthe strength of biodiversity effects across a large number ofecosystem processes measured in a single experimentpermits more direct comparisons. Here, we present ananalysis of 418 separate measures of 38 ecosystem processes.Overall, 45 % of processes were significantlyaffected by plant species richness, suggesting that, whilediversity affects a large number of processes not allrespond to biodiversity. We therefore compared thestrength of plant diversity effects between different categoriesof ecosystem processes, grouping processesaccording to the year of measurement, their biogeochemicalcycle, trophic level and compartment (above- orbelowground) and according to whether they were measuresof biodiversity or other ecosystem processes, biotic orabiotic and static or dynamic. Overall, and for severalindividual processes, we found that biodiversity effectsbecame stronger over time. Measures of the carbon cyclewere also affected more strongly by plant species richnessthan were the measures associated with the nitrogen cycle. In order to predict which ecosystem functions are most at risk from biodiversity loss, meta-analyses have generalised results from biodiversity experiments over different sites and ecosystem types. In contrast, comparing the strength of biodiversity effects across a large number of ecosystem processes measured in a single experiment permits more direct comparisons. Here, we present an analysis of 418 separate measures of 38 ecosystem processes. Overall, 45 % of processes were significantly affected by plant species richness, suggesting that, while diversity affects a large number of processes not all respond to biodiversity. We therefore compared the strength of plant diversity effects between different categories of ecosystem processes, grouping processes according to the year of measurement, their biogeochemical cycle, trophic level and compartment (above- or belowground) and according to whether they were measures of biodiversity or other ecosystem processes, biotic or abiotic and static or dynamic. Overall, and for several individual processes, we found that biodiversity effects became stronger over time. Measures of the carbon cycle were also affected more strongly by plant species richness than were the measures associated with the nitrogen cycle. Further, we found greater plant species richness effects on measures of biodiversity than on other processes. The differential effects of plant diversity on the various types of ecosystem processes indicate that future research and political effort should shift from a general debate about whether biodiversity loss impairs ecosystem functions to focussing on the specific functions of interest and ways to preserve them individually or in combination.

Recently the establishment of small measures, as check dams on fields and retention areas at the outlet of small catchments has been introduced in order to reach two goals at the same time : the prevention of flooding and the reduction of off-site damages from soil erosion. This concept assumes that the areas where soil erosion is occurring are as well the areas creating the flooding problem and vice versa. The results of a three- year field study presented in this paper question this assumption. They reveal a distinct difference in the spatial and temporal variability of sediment yield patterns and runoff contribution patterns on the catchment-scale., Résumé Récemment des mesures locales d'aménagement telles que les diguettes anti-érosives sur les terres agricoles et les réseaux de collecte des eaux à la sortie des petits bassins-versants ont été préconisées dans le double but de prévenir les crues et de réduire la charge des sédiments emportés par les eaux. Cette conception implique qu'un terrain sensible à une assez forte érosion est aussi une cause d'inondation et vice versa. Les résultats d'une recherche conduite sur le terrain durant trois ans remettent en question cette hypothèse. A l'échelle du bassin-versant il existe une différence considérable entre la variabilité temporelle et spatiale des écoulements et celle des sédiments transportés., Baade Jussi. Spatial and temporal variability of discharge and sediment yield in small loess-covered catchments/Variabilité spatio-temporelle des débits et de la charge sédimentaire dans de petits bassins versants lœssiques. In: Géomorphologie : relief, processus, environnement, Décembre 1996, vol. 2, n°3. pp. 65-74.