Net Soil Research Articles

EUSEDcollab: a network of data from European catchments to monitor net soil erosion by water

As a network of researchers we release an open-access database (EUSEDcollab) of water discharge and suspended sediment yield time series records collected in small to medium sized catchments in Europe. EUSEDcollab is compiled to overcome the scarcity of open-access data at relevant spatial scales for studies on runoff, soil loss by water erosion and sediment delivery. Multi-source measurement data from numerous researchers and institutions were harmonised into a common time series and metadata structure. Data reuse is facilitated through accompanying metadata descriptors providing background technical information for each monitoring station setup. Across ten European countries, EUSEDcollab covers over 1600 catchment years of data from 245 catchments at event (11 catchments), daily (22 catchments) and monthly (212 catchments) temporal resolution, and is unique in its focus on small to medium catchment drainage areas (median = 43 km2, min = 0.04 km2, max = 817 km2) with applicability for soil erosion research. We release this database with the aim of uniting people, knowledge and data through the European Union Soil Observatory (EUSO).

Groundwater effects on net primary productivity and soil organic carbon: a global analysis

Groundwater affects ecosystem services (ES) by altering critical zone ecohydrological and biogeochemical processes. Previous research has demonstrated significant and nonlinear impacts of shallow groundwater on ES regionally, but it remains unclear how groundwater affects ES at the global scale and how such effects respond to environmental factors. Here, we investigated global patterns of groundwater relationships with two ES indicators—net primary productivity (NPP) and soil organic carbon (SOC)—and analyzed underlying factors that mediated groundwater influences. We quantitatively compared multiple high-resolution (∼1 km) global datasets to characterize water table depth (WTD), NPP and SOC, and performed spatial simultaneous autoregressive modeling to test how selected predictors altered WTD-NPP and WTD-SOC relationships. Our results show widespread significant WTD-NPP correlations (61.5% of all basins globally) and WTD-SOC correlations (64.7% of basins globally). Negative WTD-NPP correlations, in which NPP decreased with rising groundwater, were more common than positive correlations (62.4% vs. 37.6%). However, positive WTD-SOC relationships, in which SOC increased with rising groundwater, were slightly more common (53.1%) than negative relationships (46.9%). Climate and land use (e.g., vegetation extent) were dominant factors mediating WTD-NPP and WTD-SOC relationships, whereas topography, soil type and irrigation were also significant factors yet with lesser effects. Climate also significantly constrained WTD-NPP and WTD-SOC relationships, suggesting stronger WTD-NPP and WTD-SOC relationships with increasing temperature. Our results highlight that the relationship of groundwater with ES such as NPP and SOC are spatially extensive at the global scale and are likely to be susceptible to ongoing and future climate and land-use changes.

Measuring uncertainty in ecosystem service correlations as a function of sample size

The ecosystem service literature has drastically expanded since the Millennium Ecosystem Assessment, yet the nature of how ecosystem services interact across space is still poorly understood. A key unresolved question is how efforts in sampling (a proxy for data availability) affect the calculation of the interactions or associations among ecosystem services. We contribute to answering this question by estimating a suite of ecosystem services and asking how the values of their interactions – in the form of spatial correlations – change as a function of the sampling rate of the landscape. Specifically, we estimate a set of seven ecosystem services for France (agricultural production potential, biodiversity, carbon storage, livestock grazing potential, net ecosystem productivity, pollination, and soil loss), applying four different measures for biodiversity, seven different methods for carbon storage, and three for pollination. We find that spatial correlations are fairly robust to the sampling rate, supporting the notion that moderate sampling rates across a heterogenous landscape are sufficient to obtain reliable estimates of the average correlation occurring across the landscape. In other words, despite heterogeneity in the spatial distribution of ecosystem services, at sufficient sample sizes we only need to randomly sample ten percent of the landscape to acquire an accurate measure of the correlations between all ecosystem services averaged across the entire landscape. Our results have implications for management, with applications for sampling extent and intensity and the identification of ecosystem service bundles.

Moss biocrusts buffer soil CO2 effluxes in a subtropical karst ecosystem

Biocrusts, specialized communities comprised of mosses, lichens, cyanobacteria, fungi, and bacteria occurring on the ground surface, are famous as ecological engineers on Earth, but less is understood in humid karst areas, where they are often widespread and provide important ecosystem services. To better understand how biocrusts affect soil carbon cycles, we performed an in situ study monitoring net soil exchange (NSE) of CO2, soil respiration (Rs), soil temperature and moisture, and determined soil nutrient contents and carbon-related enzyme activities over three different microcosms (soils covered by moss biocrusts, soils deprived of biocrust-forming mosses, and bare soils) in a subtropical karst ecosystem in southwest China. The results showed that, in comparison with bare soils, moss biocrusts increased Rs by 40% but decreased NSE by 49% and the temperature sensitivity of Rs by 35%. However, disturbance to moss biocrusts decreased Rs by 26% but increased NSE by 104% and the temperature sensitivity of Rs by 93%. Although moss biocrusts increased the content of soil organic carbon and total nitrogen and the activity of β-glucosidase, this effect was reversed by disturbance to moss biocrusts. While Rs was significantly correlated with soil temperature and moisture, the effect of moss biocrusts on Rs was partly explained by soil organic carbon, total nitrogen, and β-glucosidase. Overall, this study adds to the scarce number of experiments characterizing biocrust ecology in humid karst ecosystems and calls for management efforts to protect and restore biocrusts to buffer soil CO2 emissions under global change scenarios.

Exploring the spatial heterogeneity of ecosystem services and influencing factors on the Qinghai Tibet Plateau

Identifying the spatial heterogeneity characteristics of ecosystem services (ESs) and their influencing mechanisms is crucial for regional ecological management and sustainable development. This study quantified net primary production (NPP), water yield (WY), soil conservation (SC), sand fixation (SF), habitat quality (HQ) and total ecosystem service (TES) on the Qinghai Tibet Plateau (QTP), and then analyzed the spatial–temporal characteristics of ESs. The geographical detector model (GDM), geographically weighted regression (GWR) model, and constraint lines were used to explore the effects of influencing factors on ESs. The results showed that (1) NPP, WY, SC, HQ and TES showed an increasing trend from 2000 to 2018, while SF showed a decreasing trend. NPP, WY, SC and TES showed a spatial distribution pattern of “high values in the southeast and low values in the northwest”, while the high values of SF were located in the northern QTP and the high values of HQ were located in the southern QTP. (2) NDVI was the key factor influencing NPP, SC, HQ and TES, and precipitation dominated WY, and SF was mainly influenced by Largest patch index (LPI). (3) In most of the study areas, the natural factors (precipitation, temperature, DEM, slope and NDVI) had positive effects on NPP, SC and TES and both positive and negative effects on WY, SF and HQ. The human factors (Resident, Road and LPI) had positive effects on HQ and both positive and negative effects on other ESs. There were mainly non-monotonic constraint effects of influencing factors on ESs. Overall, natural factors had a much stronger influence on ESs than human factors, and the interactions among factors were much stronger than their independent effects. The results of this study can provide a basis for ecological protection on the QTP.

Lipid‐enhanced Oilcane does not impact soil carbon dynamics compared with wild‐type Sugarcane

AbstractThe carbon neutral potential of bioenergy relies in part on the ability of feedstocks to sequester carbon (C) in the soil. Sugarcane is one of the most widely used bioenergy crops, yet there remain unknowns about how it impacts soil C dynamics. In addition, Oilcane, a genetically modified version of Sugarcane has been produced to accumulate more energy‐dense oils and less soluble lignin, which enhances conversion efficiency but may also impact soil C cycling. Thus, our objectives were to examine the impact of Sugarcane litter decomposition on soil C formation and losses and determine if the genetic modifications to produce Oilcane alter these dynamics. To do this, we incubated bagasse (processed stem litter) and leaf litter from Sugarcane and Oilcane in microcosms with forest soil for 11 weeks. We used differences in natural abundance δ13C between C3 forest soil and C4 litter to trace the fate of the litter into respiratory losses as well as stable and unstable soil C pools. Our results show that genetic modifications to Oilcane did not substantially alter soil C dynamics. Sugarcane and Oilcane litter both led to net soil C gains dominated by an accumulation of the added litter as unstable, particulate organic C (POC). Oilcane litter led to small but significantly greater net soil C gains than Sugarcane litter due to greater POC formation, but the formation of stable, mineral associated organic matter (MAOC) did not differ between crop types. Sugarcane and Oilcane had opposing effects on tissue type where Sugarcane bagasse formed more MAOC, while Oilcane leaves preferentially remained as POC which may have important management implications. These results suggest that genetic modifications to Sugarcane will not significantly impact soil C dynamics; however, this may not be universal to other crops particularly if modifications lead to greater differences in litter chemistry.

Research on the Trade-Offs and Synergies of Ecosystem Services and Their Impact Factors in the Taohe River Basin

The Taohe River Basin is an essential ecological function area in the upper reaches of the Yellow River. Understanding the intricate trade-offs and synergies between ecosystem services (ESs) and exploring the impact of different factors are essential for achieving win–win outcomes in ecosystem management and socioeconomic development. The role of impact factors on the relationship between ESs, nevertheless, is more challenging to spatialize. This study used different models to estimate the net primary productivity (NPP), water yield (WY), and soil conservation (SC), and analyzed synergies and trade-offs between Ess. The spatial heterogeneity of the effects of natural and social factors on the relationships between Ess was explored using a geographic detector and a multi-scale geographically weighted regression (MGWR) model. The results show that: (1) NPP, WY, and SC all exhibit a rising trend, with multi-year averages of 488.99 gC/m2, 157.29 mm, and 1441.51 t/hm2, respectively; (2) NPP–WY and NPP–SC exhibit trade-offs in the majority of regions, while WY–SC are primarily synergistic in the upper and middle reaches, and they have the highest percentage of cropland, forest, and grassland; and (3) precipitation (PRE) has the greatest impact on the trade-off between NPP–WY and NPP–SC in the upper and middle reaches, and the gross domestic product (GDP), population density (POP), and distance from cropland (CROP) are the primary factors determining the synergy between NPP and WY in the lower reaches of the Loess Plateau cropping sector. PRE, digital elevation model (DEM), and CROP are the primary impact factors affecting the synergy of WY–SC. This study may serve as a reference for examining the evolutionary mechanism underlying the trade-offs and synergies between ESs and provide a scientific basis for future ecological environmental protection and regional land management in the Taohe River Basin.

Combined use of UAV-SfM surveys, soil particle tracking with RFID tags and a sediment connectivity index to study plot-scale sediment transport

To explore the processes of soil erosion at the plot scale, Digital surface model of Differences (DoD) maps (Unmanned Aerial Vehicle – Structure from Motion (UAV-SfM) method) and data from Radio Frequency Identification (RFID) tags were analysed. The comparison of differences in accuracy of UAV-SfM and 3D terrestrial laser scanner (TLS) measurements, and the integration of the UAV-SfM method and soil particle tracing with RFID tag locations were conducted to assess sediment transport in a plot in Fukushima prefecture, Japan. The Universal Soil Loss Equation (USLE) plot was installed and kept with no vegetation and no cultivation. Water and sediment discharges were measured at the outlet of the plot, and the topographic index of runoff and sediment connectivity (IC) –focused on surface roughness– was also estimated. Based on field surveys, four periods were defined. Locations of RFID tags were firstly determined by using orthoimages derived from the UAV-SfM method and then compared with those locations measured with a laser total station. The mean and standard deviation of difference amounts of UAV-SfM were of 1 and 3.3 mm, respectively. On average, the RFID tags were located with an accuracy of 3.1 cm (RMSE). Although data of tags tracing showed short transport distances with rill erosion, the results of the UAV-SfM surveys showed an increase of sediment connectivity (SC) over the study period that may explain the largest sediment discharge, especially of fine soil particles. The concurrence of higher values of SC as well as the development of new and longer rills demonstrated the important activity of net soil loss in our study site. The combination of distinct methods and techniques, all providing accurate measurements, shed light on the sediment transport process at short distances, which affects the net water and sediment discharge at larger scales.

Modeling impacts of saltwater intrusion on methane and nitrous oxide emissions in tidal forested wetlands.

Emissions of methane (CH4 ) and nitrous oxide (N2 O) from soils to the atmosphere can offset the benefits of carbon sequestration for climate change mitigation. While past study has suggested that both CH4 and N2 O emissions from tidal freshwater forested wetlands (TFFW) are generally low, the impacts of coastal droughts and drought-induced saltwater intrusion on CH4 and N2 O emissions remain unclear. In this study, a process-driven biogeochemistry model, Tidal Freshwater Wetland DeNitrification-DeComposition (TFW-DNDC), was applied to examine the responses of CH4 and N2 O emissions to episodic drought-induced saltwater intrusion in TFFW along the Waccamaw River and Savannah River, USA. These sites encompass landscape gradients of both surface and porewater salinity as influenced by Atlantic Ocean tides superimposed on periodic droughts. Surprisingly, CH4 and N2 O emission responsiveness to coastal droughts and drought-induced saltwater intrusion varied greatly between river systems and among local geomorphologic settings. This reflected the complexity of wetland CH4 and N2 O emissions and suggests that simple linkages to salinity may not always be relevant, as non-linear relationships dominated our simulations. Along the Savannah River, N2 O emissions in the moderate-oligohaline tidal forest site tended to increase dramatically under the drought condition, while CH4 emission decreased. For the Waccamaw River, emissions of both CH4 and N2 O in the moderate-oligohaline tidal forest site tended to decrease under the drought condition, but the capacity of the moderate-oligohaline tidal forest to serve as a carbon sink was substantially reduced due to significant declines in net primary productivity and soil organic carbon sequestration rates as salinity killed the dominant freshwater vegetation. These changes in fluxes of CH4 and N2 O reflect crucial synergistic effects of soil salinity and water level on C and N dynamics in TFFW due to drought-induced seawater intrusion.

Carbon capture and seasonal ‘C’ offset by Foeniculum vulgare grown with N, FYM and their integration

Field experiments were carried out on Typic Haplustepts soil having texture sandy loam with various nitrogen levels i.e. 0, 40, 60, 80, 100, 120 kg ha-1 and also integrated use of N + FYM levels taking fennel (Foeniculum vulgare) variety AF-1 as test crop. These treatments were compared with control. Results revealed that seed yield and biomass increased with increasing doses of N levels which was > 1.5 times more with 120 kg N as compared to control. Likewise N+FYM also gave more yield than their individual applications. Carbon content was lower and accumulation in seed, stover including total uptake was higher beyond the 60 kg N ha-1. Carbon content was lower in stover with higher dose of N + FYM and the accumulation in seed and stover was higher. Carbon captured by fennel was more with 12 t FYM applied either with 40 or 80 kg N ha-1. Total or net soil carbon pool was more with higher levels of N, FYM and their combinations. Net carbon offset by the crop and soil in a season was more beyond the 60 kg N or either level of FYM and also in combination with N. Mean carbon offset by fertilizer N was 4.8 t ha-1 and 5.1 t ha-1 by N + FYM. Interestingly carbon content in seed was slightly lower or equal to the stover, hence a common thresher is not applicable to separate them easily and the second most important finding is that combine use of N and FYM captured more C seasonally than the fertilizer N alone, while fertilizer N has more manufacturing C foot print than the manure. Hence, integrated use of N and FYM has multi-faced benefits for reducing C foot print of input, captures more C during a season easily accessibility to the farmers, improves the crop yield and soil properties.

Enhanced mite grazing leads to pattern shifts in soil N2O emissions after organic fertilizer application

Studies have reported inconsistent (or even opposing) effects of soil mesofauna, such as mites, on net soil N2O emissions. Here we show that whether mites affect net N2O emissions positively, negatively, or neutrally depends on the microbial guild that dominates the emissions. We found that enhanced mite grazing, following artificially elevated mite populations, led to shifts in N2O emission patterns in soils applied with organic fertilizer: N2O emissions decreased under low soil moisture conditions, whereas those under high soil moisture conditions increased. Since the dominant microbial processes underlying N2O emissions shift from fungal to bacterial denitrification with increasing soil moisture, our results imply that enhanced mite grazing tends to decrease net soil N2O emissions dominated by fungi, whereas increase those dominated by bacteria. Furthermore, we observed that mite grazing largely suppressed fungal mycelial growth after organic fertilizer application but promoted the dispersal and decomposition of fertilizer granules and N mineralization. These findings suggested that the distinct effect of enhanced mite grazing on N2O emissions dominated by fungi and bacteria could occur because high-intensity mite grazing affects fungi-derived N2O emissions mainly by consuming the biomass of N2O-producing fungi, which has a negative effect, whereas affects bacteria-derived N2O emissions mainly by stimulating bacterial N2O-producing processes via the promotion of N diffusion from the fertilizer to the soil, which has a positive effect.

Response of temperate forest ecosystem services to rainfall: A case study in the forest nature reserves of northern China

In the context of global climate change, temperate forests in climate-sensitive areas are inevitably affected. To deepen the understanding of the impact on precipitation changes into the relationship between key ecosystem services (ESs), this study selected net primary productivity (NPP), soil conservation (SC) and water yield (WY) of temperate forest in northern China as objects, and the Spearman correlation test and redundancy analysis were applied to analyze the response of ESs relationship to precipitation gradient. The results show that precipitation is the meteorological factor with the greatest impact (contribution 21.2%, p<0.01) on ESs and their relationships in temperate forests. The 600-700 mm precipitation gradient is the key turning point in the change of ESs relationship of WY with NPP and SC. This indicates that attention should be paid to the spatial variation of the 600-700 mm precipitation region in the future warm-wet in northern China, which should be used as a dividing line of forest management and policy development. Based on the results, future restoration projects in northern temperate forest should focus on (1) in areas with less than 600-700 mm of precipitation, attention should be paid to the selection of tree species for afforestation to maintain regional water balance; (2) in areas with more than 700 mm of precipitation, soil and water conservation projects need to be planned, especially in mountainous area. The research can not only support the management of temperate forest ecosystems in northern China, but also provide reference to other forest ecosystems to cope with climate change.

Exploring the effects of various rotation lengths on the ecosystem services within a multiple-use management framework

Addressing the spatio-temporal dynamics of forest development under different management scenarios with varying rotation lengths is a challenge in forest management planning. This research aims to forecast forest development and assess the relative consequences of varying rotation lengths on several ecosystem services such as wood production, habitat for biodiversity, carbon sequestration, water provision, soil protection and cultural values. Forest development is simulated with the ETCAP model to examine the long-term effects of various rotation lengths with silvicultural prescriptions on the ecosystem services. Bürücek forest planning unit is used as a case study area with 10,711 ha forests in upper Mediterranean region of Turkey. Shorter rotation lengths are considered one of the main mitigation measures to climate changes in forestry; however, lead to the increased harvest level, net present value, ground water and soil loss, and reductions in the largest stand volume, understory, basal area, carbon storage and the cultural values with less regulated forest structure. The management scenarios with longer rotation lengths, however, have highlighted improvements in the carbon storage, larger standing volume, mean stand age, basal area and cultural values, and reductions in the mean harvest volume, net present value, ground water and soil loss due to larger-even distribution of tree sizes and stand development stages. An aspiration for a higher level of provisioning services for economic motivations may need to be discarded for the sake of enhancing the capacity of forest ecosystems to sequester more carbon and provide better habitat condition for biodiversity conservation with a careful design and selection of rotation lengths. Overall, the choice of optimal rotation length is highly dependent on a desired set of management objectives and target forest structure driven mostly by management interventions with the appropriate type and level of ecosystem services, provided that a thorough understanding of forest dynamics is achieved by considering both risks and uncertainties associated with natural disturbances and socio-economic conditions.

Warming and drought weaken the carbon sink capacity of an endangered paleoendemic temperate rainforest in South America.

Measurements of ecosystem carbon (C) fluxes in temperate forests are concentrated in the Northern Hemisphere, leaving the functionally diverse temperate forests in the Southern Hemisphere underrepresented. Here, we report three years (February 2018-January 2021) of C fluxes, studied with eddy-covariance and closed chamber techniques, in an endangered temperate evergreen rainforest of the long-lived paleoendemic South American conifer Fitzroya cupressoides. Using classification and regression trees we analyzed the most relevant drivers and thresholds of daily net ecosystem exchange (NEE) and soil respiration. The annual NEE showed that the forest was a moderate C sink during the period analyzed (-287±38 g C m-2 year -1). We found that the capacity to capture C of the Fitzroya rainforests in the Coastal Range of southern Chile is optimal under cool and rainy conditions in the early austral spring (October-November) and decreases rapidly towards the summer dry season (January-February) and autumn. Although the studied forest type has a narrow geographical coverage, the gross primary productivity measured at the tower was highly representative of Fitzroya and other rainforests in the region. Our results suggest that C fluxes in paleoendemic cool F. cupressoides forests may be negatively affected by the warming and drying predicted by climate change models, reinforcing the importance of maintaining this and other long-term ecological research sites in the Southern Hemisphere.

Spatial and temporal effect and driving factors of ecosystem service trade-off in the Qingjiang River Basin, China.

Identifying the spatiotemporal differentiation characteristics of trade-offs/synergies relationships of ecosystem service in watersheds and their influencing factors is essential for ecosystem management and regulation. It is of great significance for the efficient allocation of environmental resources and the rational formulation of ecological and environmental policies. We used correlation analysis and root mean square deviation to analyze the trade-offs/synergies relationships among grain provision, net primary productivity (NPP), soil conservation, and water yield service in the Qingjiang River Basin from 2000 to 2020. Then, we analyzed the critical factors affecting the trade-offs of ecosystem services by using the geographical detector. The results showed that grain provision service in the Qingjiang River Basin presented a decreasing trend from 2000 to 2020, and that NPP, soil conservation, as well as water yield service showed an increasing trend. There was a decreasing trend in the degree of trade-offs between grain provision and soil conservation services, NPP and water yield service, and an increasing trend in the intensity of trade-offs between other services. Grain provision and NPP, soil conservation and water yield showed trade-off in the northeast and synergy in the southwest. There was a synergistic relationship between NPP with soil conservation and water yield in the central part and a trade-off relationship in the surrounding area. Soil conservation and water yield showed a high degree of synergy. Land use and normalized difference of vegetation index were the dominant factors in the intensity of trade-offs between grain provision and other ecosystem services. Precipitation, temperature, and elevation were the dominant factors in the intensity of trade-offs between water yield service and other ecosystem services. The intensity of ecosystem service trade-offs was not only affected by a single factor. In contrast, the interaction between the two services or the common factors behind the two services was the determining factor. Our results could provide a reference for developing ecological restoration planning strategies in the national land space.

Vegetation restoration enhances soil erosion resistance through decreasing the net repulsive force between soil particles

Vegetation restoration is a valid way to improve soil erosion resistance by enhancing the stability of soil aggregates. Past studies have shown that the net force (the sum of electrostatic, hydration, and van der Waals forces) between soil particles had crucial effects on the stability of soil aggregates. However, little is known about the influence of vegetation restoration on the net force and soil erosion resistance, which hinders our quantitative understanding of this process at the particle to particle level. In this study, to quantitatively analyze the influence of vegetation restoration on soil net force and their relationship with aggregate stability and erosion resistance, we collected soil samples from four different restoration stages (including farmland, grassland, shrubland, and forest), then used Na+-saturated soil aggregates (1 to 5 mm model aggregates) to conduct our experiments. The stability of soil aggregates and erosion resistance were tested through the wet sieving method and rainfall simulation experiments. Our results indicated that the soil net force was repulsive and decreased with vegetation restoration. The stability of soil aggregates and erosion resistance increased with vegetation restoration. With the decrease of electrolyte concentration, the net force and splash erosion rate both first increased (from 1 to 10−2 mol L−1) then remained stable (from 10−2 to 10−4 mol L−1), while the soil aggregate stability first decreased (from 1 to 10−2 mol L−1) then remained stable (from 10−2 to 10−4 mol L−1). The experimental results of soil aggregate stability and splash erosion rate changing with electrolyte concentration could be well explained by soil net force. Moreover, the rate of splash erosion and the stability of soil aggregates showed a significantly negative linear relationship (P < 0.01). Overall, the results indicated that the vegetation restoration process could reduce the net repulsive force of soil particles and thus increase the stability of soil aggregates and erosion resistance. These findings provided quantitative information about the mechanistic understanding of vegetation restoration improving soil erosion resistance.

Study on Multi-Scale Characteristics and Influencing Factors of Trade-Offs and Synergies between Ecosystem Services in Jiangxi Province

The trade-offs and synergies reveal the profit and loss relationship between ecosystem services, which is of great significance to the sustainable development of natural resources. The ecosystem services in Jiangxi Province, such as net primary productivity (NPP), soil conservation (SC) and water yield (WY) during 2000–2020, were estimated in this study. The correlation coefficient was adopted to analyze the trade-offs and synergies between the three ecosystem services by static space correlation and dynamic space correlation from such perspectives as Watershed, county and grid. Moreover, the influence of the three ecosystem services and the relations between them were explored from four aspects: landform, NDVI, accumulated temperature and precipitation. The results showed that the ecological environment quality in Jiangxi Province was improved and that the distribution of ecosystem services had significant regional characteristics. In the static analysis, ecosystem services at all scales were remarkably synergistic, and synergies weakened rapidly and even turned into trade-offs as the scale decreased. In the dynamic analysis, ecosystem services at all scales were mainly synergistic; the proportion of significant samples was much lower than that in the static analysis, the degree of trade-offs/synergies decreased with the decrease in scale, and the decrease was smaller than that in the static analysis. The major constraints for SC were landform and NDVI. The main constraint for WY was precipitation, and that for NPP was NDVI. Affected by various factors, NPP and SC were stably synergistic, NPP and WY were in a stable trade-off relationship, and the relationship between SC and WY was unstable. The trade-offs and synergies changed with factors and zoning.

Evapotranspiration in Semi-Arid Climate: Remote Sensing vs. Soil Water Simulation

Estimating crop evapotranspiration (ETa) is an important requirement for a rational assessment and management of water resources. The various remote sensing products allow the determination of crops' biophysical variables integrated in the evaluation of ETa by using surface energy balance (SEB) models. This study compares ETa estimated by the simplified surface energy balance index (S-SEBI) using Landsat 8 optical and thermal infra-red spectral bands and transit model HYDRUS-1D. In semi-arid Tunisia, real time measurements of soil water content (θ) and pore electrical conductivity (ECp) were made in the crop root zone using capacitive sensors (5TE) for rainfed and drip irrigated crops (barley and potato). Results show that HYDRUS model is a fast and cost-effective assessment tool for water flow and salt movement in the crop root layer. ETa estimated by S-SEBI varies according to the available energy resulting from the difference between the net radiation and soil flux G0, and more specifically according to the assessed G0 from remote sensing. Compared to HYDRUS, the ETa from S-SEBI was estimated to have an R2 of 0.86 and 0.70 for barley and potato, respectively. The S-SEBI performed better for rainfed barley (RMSE between 0.35 and 0.46 mm·d-1) than for drip irrigated potato (RMSE between 1.5 and 1.9 mm·d-1).

Measuring Annual Sedimentation through High Accuracy UAV-Photogrammetry Data and Comparison with RUSLE and PESERA Erosion Models

Model-based soil erosion studies have increased in number, given the availability of geodata and the recent technological advances. However, their accuracy remains rather questionable since the scarcity of field records hinders the validation of simulated values. In this context, this study aims to present a method for measuring sediment deposition at a typical Mediterranean catchment (870 ha) in Greece through high spatial resolution field measurements acquired by an Unmanned Aerial Vehicle (UAV) survey. Three-dimensional modeling is considered to be an emerging technique for surface change detection. The UAV-derived point cloud comparison, applying the Structure-from-Motion (SfM) technique at the Platana sediment retention dam test site, quantified annual topsoil change in cm-scale accuracy (0.02–0.03 m), delivering mean sediment yield of 1620 m3 ± 180 m3 or 6.05 t ha−1yr−1 and 3500 m3 ± 194 m3 or 13 t ha−1yr−1 for the 2020–2021 and 2021–2022 estimation. Moreover, the widely applied PESERA and RUSLE models estimated the 2020–2021 mean sediment yield at 1.12 t ha−1yr−1 and 3.51 t ha−1yr−1, respectively, while an increase was evident during the 2021–2022 simulation (2.49 t ha−1yr−1 and 3.56 t ha−1yr−1, respectively). Both applications appear to underestimate the net soil loss rate, with RUSLE being closer to the measured results. The difference is mostly attributed to the model’s limitation to simulate gully erosion or to a C-factor misinterpretation. To the authors’ better knowledge, this study is among the few UAV applications employed to acquire high-accuracy soil loss measurements. The results proved extremely useful in our attempt to measure sediment yield at the cm scale through UAV-SfM and decipher the regional soil erosion and sediment transport pattern, also offering a direct assessment of the retention dams’ life expectancy.

Difference in total N and its aggregate-associated N following cropland restoration in a karst region, Southwest China.

Cropland conversion has been cited as one of the most effective measures for increasing soil nitrogen pool in karst degraded regions. However, it is still unclear how N associated with aggregate patterns and their contribution to net soil N accumulation after cropland conversion. The experiment included four treatments with one control and three restoration strategies, that is, maize-soybean rotation cultivation (the control), sugarcane, mulberry, and forage grass cultivation. Soil samples were selected to determine the soil aggregate amount and its associated N content and stock across 0-30 cm soil layer. Macro-aggregate (> 2mm) was the predominant aggregate fraction in all cropland use types and had the largest N stock. Forage grass cultivation substantially increased N stocks in bulk soil and aggregate fractions. The N contents and stocks associated with aggregate were shown to be positively correlated with bulk soil N stocks. Furthermore, the increase in N stock in forage grass soil was largely caused by an increase in N stock within macro-aggregates (> 2mm), which is further attributed to the increased N content within macro-aggregates. Overall, forage grass cultivation replaced maize-soybean cultivation which was proposed as an ecological restoration model to improve soil N sequestration capacity due to its function in increasing the N stock of aggregate in the karst degraded region of Southwest China.