This study updates information on the evolution of glacier shrinkage in Cocuy-Güican mountains since the maximum glacier extent of the Little Ice Age (LIA), and presents the first mass balance data of Ritacuba glacier since 2009, that is compared to the available mass balance for the Conejeras Glacier (Los Nevados National Park). This study also discusses the hydrological significance of Colombian glaciers which is still largely unknown because of the very limited information available. Glaciers in Cocuy-Güican covered 13.2 km2 in 2019 that compared to the 127.8 km2 during the maximum LIA represents a shrinkage of 89.7%. Glacier cover observations in 1955, 1994, 2010 and 2019, reveal that the rate of ice loss was the largest from 1994 to 2010 (0.59 km2 yr-1) and was then more than halved from 2010 to 2019 (0.34 km2 yr-1). This slowdown in glacier retreat is in line with a moderate negative mass balance measured for 2009-2019, with an accumulated loss of 1,766 mm w.e. The progressive confinement of glaciers to higher elevation and optimal topographic context together with a lack of recent marked climatic anomalies, could explain that Cocuy-Güican glaciers have temporally reached near equilibrium state condition. This is in stark contrast with Conejeras glacier where 47,000 mm w.e. has been lost in the same period. The available data on runoff and isotopic traces of streamflows and precipitation suggest a primary control of precipitation on the hydrological variability of the high elevated sites, compared to glacier melt water.

Soil organic carbon (SOC) and iron (Fe) oxides are known to affect the formation and stability of soil aggregates. However, the effects of SOC and Fe oxides on soil aggregates stability under straw returning and potassium (K) fertilizer application in paddy–upland rotation systems are less well-studied. This study primarily investigated soil aggregates dynamics and their stability indices (mean weight diameter, MWD; geometric mean diameter, GMD), and soil binders (SOC and iron oxides) after rice and rape harvests under four treatments: F1，mineral nitrogen (N) and phosphorus (P) fertilizer; F2, mineral NPK fertilizer; F3, mineral NP fertilizer with straw returning; F4, mineral NPK fertilizer with straw returning in rice–rape cropping system. Straw returning treatments (F3 and F4) significantly (P <0.05) increased MWD and GMD, but the effect of K is not obvious. The soil aggregates stability was higher after the rape harvest than rice harvest, but SOC content was the opposite. Straw input can increase the contents of SOC, alkane-C and aromatic-C concentrations, especially in >0.25 mm aggregates. Long-term straw incorporation significantly increased the amorphous (Feo) and complex iron oxides (Fep) concentrations. SOC and Fep in bulk soil and >5 mm aggregates were significantly related with MWD, and significant relationship was observed between MWD and Feo in <5 mm fractions. Thus, the high levels of SOC, alkane-C, Feo and Fep in soil after straw returning were responsible for the aggregate stability, but the effect of potassium application is not obvious in a rice–rape cropping system.

The combination of plastic film mulching and subsurface organic amendment is a novel strategy for saline soil amelioration and utilization in China. However, how the strategy affect soil organic carbon (SOC) contents directly and indirectly (physical protection and microbiological regulation) were still not-documented. Therefore, four treatments, i.e., no amendment with and without plastic film mulching, subsurface (10-30 cm soil depth) organic amendment with and without plastic film mulching, were arranged and sampled after three-year filed experiment. Compared with no amendment with and without plastic film mulching, subsurface organic amendment increased the SOC content in the 0-40 cm soil depth by 70% and 90%, respectively. Plastic film mulching decreased SOC by 16% without organic amendment. Subsurface organic amendment transformed the dominant aggregation particles from <0.053 mm to 0.25-2 mm, indicating that both direct carbon input and indirect physical protection contributed to SOC increment. Conversely, SOC decreased with plastic film mulching due to the 14% lower fungal diversity compared with soil without plastic film mulching, was supported by the positive path coefficient from fungal diversity to SOC. Therefore, the combination of plastic film mulching and subsurface organic amendment increased SOC by 61% by direct carbon input and indirect physical protection and microbial regulation. In conclusion, subsurface organic amendment with plastic film mulching reinforced soil organic carbon increment through altering saline soil aggregate structure and regulating fungal community, and confirmed it is a feasible way to increase SOC for saline soil amelioration.

Planting Robinia pseudoacacia in water-limited regions can promote soil and water conservation and improve ecological service function. However, it can also cause the formation of below-ground dried soil layers (DSLs), causing land degradation and tree mortality. To ascertain the spatial-temporal dynamics and recovery processes of DSLs, we monitored the deep soil water content (SWC) to a depth of 500 cm at 27 sites on a typical R. pseudoacacia forest (planted in 2003) hillslope from 2017–2020, and calculated the evaluation indices of DSLs based on plant and soil criteria. We found that, compared to plant criterion identified-DSLs, the degree of soil criterion identified-DSLs was more severe, although the spatial-temporal characteristics were similar. Severe soil desiccation was identified in the forest as 79% of the 500 cm profile drying out below 101 cm. During the study period, the mean thickness of DSLs and mean SWC within DSLs were 397 cm and 9.0%, respectively, and the quantitative index of DSLs reached level III (> 0.51, severe DSLs). All DSL indices demonstrated weak or moderate variability in space and strong variability in time. Interestingly, two rainfall events triggered DSL disappearance at seven sites, indicating the possibility of DSL recovery under heavy rainfall. Possible mechanisms explaining the DSLs recovery phenomenon were linked with continued rainfall, micro-topography, soil texture, individual root characteristics, and their interactions. This information is helpful for soil water management and land development in planted forests and for reclaiming DSLs under similar conditions.

This study explored the application of a Vertical Electrokinetic system (V-EK) with multilayer electrodes in shallow soil to form an “Electric Sieve” to mitigate and prevent the soil salinization caused by salts rising from shallow groundwater in the coastal areas. In the model V-EK system, the electric resistances of soil column, reversely corresponding to salinity, at the applied voltages 4, 10 and 20 V were 266, 487 and 1272 Ω, respectively. Meanwhile, lower electrical conductivity (EC, between 67-230 μs/cm) were observed in the soil within 50 cm below the surface at the voltages of 10 V and 20 V, which was much lower than the minimum value (581 μs/cm) of the control with no current applied. For the control column without EK treatment (0 V), soil in the surface layer had the highest EC value at 1721 μS/cm due to the salts rising from the bottom, and the EC values of soil beneath the surface were in the range of 581-1127 μS/cm. Compared to control column, the level of ions in the surface soil significantly declined after V-EK treatment, especially for the column with voltage at 10 V and 20V. When voltage was at 20 V, Na+ was detected at a range of 0.06-0.08mg/g in the surface soil, a >99% reduction when compared to the controls. Similar efficacy was observed for chloride (Cl-), in the V-EK column with the voltages at 10 V and 20V.

We explored the relative importance of climate oscillations and human-driven disturbances on the change of vegetation biomass in agroecosystems, and whether it is associated with land use. The study was carried out in the drylands of the Iberian Peninsula, NW Maghreb, Palestinian West Bank, Mozambique, China and NE Brazil, using satellite time-series and the corresponding climate fields, at ten-year observation periods with spatial and temporal resolutions of 1000 m (250 m in Palestine) and one year, respectively. For each region, we separated the relative weights of climate and time by fitting multiple-stepwise regressions to a vegetation index as the dependent variable, and annual aridity (Aridity) and year number (Time) as predictors. The relative strength of the resulting standard partial regression coefficients was then compared by the Wilcoxon Signed Ranks test, and their combined associations with land uses were determined using chi-square tests. Some points of convergence are: 1. The relative weights of Aridity and Time depend on particular regional conditions and can be determined. 2. Such weights are associated with land use intensification, such that if vegetation increases over Time, Aridity increases its relative importance with intensification; if vegetation is degrading, Aridity is always more important than Time. 3. Aridity is an indicator of vulnerability to climate warming. Resilience can be improved by reducing land use intensification. 4. Vulnerability may worsen under constant climate if agriculture is intensified. These patterns enhance an integrated understanding of Sustainable Development Goals Indicator 15.3.1, particularly its land cover and productivity trend components.

There is currently a lack of evidence surrounding changes in the health of riparian zones under different land-use patterns within mega-reservoirs and around dams. Scientific evidence for the quantitative effects of stress indicators is vague and varies significantly among reservoirs and dams worldwide. In this study, we used a field-based approach to evaluate riparian health changes—influenced by pressure indicators—across 274 transects from three land-use areas (rural, rural–urban transitional, and urban) in the Three Gorges Dam Reservoir (TGDR) in China during 2019. Multivariate statistical techniques were applied to test for riparian zone changes under these variant land-use patterns. Our results showed that 13 pressure indicators significantly influenced 27 health indicators (including parameters for habitat, plant cover, regeneration, erosion, and exotics) of the riparian zones from the three land-use areas differently. Our results also showed that parameters for plant cover, erosion, and exotics were major contributors within the selected riparian health indicators, whereas land-use designs, farming systems, and pollutant activity variables were the pressure indicators with the strongest impact. Pearson correlation (with r ranging from -0.731 to 0.989) showed that urban transects exhibited the strongest comparative interaction, whereas rural–urban transitional transects formed the weakest association. Furthermore, the agglomerative hierarchical cluster analysis revealed similarities between rural and rural–urban transitional sites while confirming substantial dissimilarity in urban locations. These comprehensive and relevant results provide essential information for reservoir administrators to implement functional changes suited to TGDR land-use scenarios.

Large bird species, such as cranes are involved in human-wildlife conflicts as they often forage in croplands. The Eurasian crane (Grus grus) is a large iconic bird species, protected across Europe, which, thanks to conservation programs and its ability to utilize croplands for foraging, shows a strongly increasing population trend. This exaggerates the already existing conflicts between crop farmers and cranes spilling over to natural habitats, where foraging by large flocks can lead to land degradation. To date, no studies have evaluated the effects of biopedturbation by cranes in grasslands, despite these habitats provide important feeding grounds for this large bird across its whole range. Here we evaluated the effect of biopedturbation by foraging Eurasian cranes on the vegetation of dry grasslands in Hungary. We used indicators of vegetation naturalness, forage quality and floral resource provision to evaluate the ecosystem state from multiple aspects. We sampled 100 quadrats in disturbed patches and 100 in intact grasslands in two seasons and two years (800 observations). We found that cranes created distinct habitat patches with different species composition compared to undisturbed areas. These early-successional patches that increased the plant diversity and floral resources but decreased the area of intact grasslands. Although crane-disturbed patches could provide forage for livestock early in the season, the forage quality of the vegetation became poor later in the year. Given the strong increase of the global crane population, monitoring the landscape-level extent of the disturbed areas, and developing a complex prevention and mitigation strategy would be important.

Organic materials are essential to increase soil organic carbon (SOC). However, it is unclear whether C sequestration is primarily affected by the form of organic materials or soil types. Wheat straw, tobacco straw, and their derived biochars were added to acidic soil, saline soil and calcareous soil in the same C concentration and incubated for 30, 90, and 180 days, respectively. The contents of humic substances (HS), the structural characteristic of SOC, and enzyme activities were investigated. The results revealed that both biochar-C and crop straw-C were mainly sequestered in humin (HU) across all soil types. Moreover, humic acid (HA) levels increased in straw treatments but not in biochar treatments. The cluster analysis and principal components analysis showed that HU had a significantly positive correlation with SOC. The aryl C of SOC increased in biochar treatments, while phenolic C and O-alkyl C of SOC increased in straw treatments. A positive correlation was found between aromatic C and SOC concentration, as well as between polyphenol oxidase activity and O-alkyl C. The formation of O-alkyl C was affected by polyphenol oxidase activity. These findings suggest that the form of organic materials and microbial activity, rather than soil types, influence the formation of HS and functional groups of SOC. Soil amended with biochar can sequester more recalcitrant C while also increasing the hydrophobicity of SOC.

Numerous studies have investigated bacterial community structure in grassland ecosystems and bacterial community responses to human management at various spatial and temporal scales; however, research on soil bacterial community assembly dynamics in the course of grassland degradation is limited. Here, the authors investigate the response and assembly processes of bacterial communities adopted in two grasslands with different degrees of degradation. Stochastic processes dominated bacterial community assembly processes in response to grassland degradation, with the bacterial diversity decreasing; however, functional gene diversity increased. Furthermore, different phyla exhibited distinct response strategies: Proteobacteria and Bacteroidetes, as r-strategists, exhibited positive responses, with increases in diversity, abundance, and niche width with an increase in grassland degradation, enhancing biodiversity and productivity; other phyla (mainly Acidobacteria) exhibited greater phylogenetic dispersion and functional redundancy, and less niche overlap, highlighting the role of K-strategy in improving community resource-use efficiency in response to resource loss in degraded grasslands. The transition from K- to r- strategy in bacterial communities following grassland degradation could help communities adapt to environmental disturbance in the form of nutrient loss. The results of the present study enhance our understanding of how nutrient loss in natural grassland ecosystems leads to shifts in bacterial community composition and assembly processes mediated by different response strategies of different phyla.

Quinoa (Chenopodium quinoa), a herbaceous annual, has been widely cultivated in recent years because of its high nutritional value and strong tolerance to abiotic stresses. The study was conducted at two planting densities (LD, 10 plants/m2; HD, 65 plants/m2) on ameliorated coastal mudflats in Jiangsu Province, China (118° 46′ E, 32° 03′ N). The results showed soil salinity and organic matter were higher in the HD than LD treatment, and salinity of the rhizosphere soil was higher than that of the non-rhizosphere soil. Quinoa grown in HD was taller, with thicker stalks and lower yields per plant, but higher yield per unit area. Amplicon sequencing showed that Proteobacteria, Bacteroidota and Acidobacteria were the dominant bacterial phyla. Regarding the rhizosphere soil, the Shannon index was higher in the HD than LD, and Proteobacteria and Bacteroidota were more abundant in the HD treatment. Fifty-one differential metabolites were identified by metabolomic assays, belonging to 14 annotated metabolic pathways. S-adenosylmethionine was the most abundant and up-regulated metabolite (fold change >1.67), and was more abundant in the roots from the LD than HD treatment. Docosahexaenoic acid was more abundant in the HD than LD treatment, and was down-regulated metabolite. In conclusion, planting density was an important factor affecting quinoa yield; compared with unplanted soil, planting quinoa at low density increased the content of the important metabolite S-adenosylmethionine in the root system of quinoa, and high density cultivation of quinoa increased soil salinity and microbial abundance and diversity.

Soil is the largest carbon reservoir in terrestrial ecosystems, and thus minor changes in it can dramatically affect atmospheric CO 2 concentrations. The fragile ecological environment in the northwestern arid zone of China is susceptible to natural and anthropogenic disturbances, which lead to variations in structure and function of the ecosystem, as well as carbon source–sink dynamics. In this study, digital soil maps of soil organic carbon stocks (SOCS) were produced at a 90-m resolution for two periods (the 1980s and 2010s) based on historical soil profile data and a random forest model. The results showed that the prediction accuracy for SOCS in the topsoil (0–30 cm) was superior to that of the subsoil (30–100 cm). Among them, the mean annual evapotranspiration, normalized difference vegetation index during the growing season, multi-year mean temperature, and clay content were the main environmental factors affecting the spatial distribution of SOCS. In the past 30 years, the SOCS of the northwestern arid zone have decreased by 585.50 Tg, with a mean decline of 19.52 Tg C yr -1. The changes in SOCS caused by land-use conversion and reductions in SOCS were further shown to be attributable to grassland desertification and agricultural reclamation. These findings are valuable for exploring the carbon cycle in terrestrial ecosystems in the context of global climate change and for achieving China’s goal of carbon neutrality.

Governments and international donors are actively promoting laser-land leveller (LLL) technology to produce environmental benefits (i.e., avoid soil salinity, minimize soil erosion risk, and groundwater security) that could lead to sustainable agricultural production and averting land degradation. We investigate the adoption process of laser-land leveller (LLL) technology in Punjab, Pakistan during the period 1985–2018 using survey data from 504 farming households. A discrete-time duration model is used to investigate factors that could influence the speed of adoption of LLL technology and an endogenous switching regression (ESR) model to evaluate its impact on groundwater usage. It is found that about 70% of the surveyed households had adopted the technology. The key determinants of the speed of adoption include strong legal land entitlements, farm size, and farm location along the watercourse. Information acquired through formal and informal sources and exposure to the technology potentially reduce adoption time. The adoption of LLL reduces groundwater use by about 23% in wheat crop. These results highlight the need for improved institutional arrangements such as extension services, technology exposure, and establishing legal property rights over land to enhance uptake of LLL technology.

Tillage practices can influence soil microbial carbon use efficiency (CUE), which is critical for carbon cycling in terrestrial ecosystems. The effect of tillage practices could also be regulated by nitrogen (N) addition. However, the soil microbial mechanism about N fertilizer effect on microbial CUE under no-tillage is still unclear. We investigated how N fertilizer regulates the effect of tillage management on microbial CUE through changing microbial properties and further assessed the impact of microbial CUE on particulate (POC) and mineral-associated organic matter carbon (MAOC) using a 16-yr field experiment with no-tillage (NT) and conventional tillage (CT), both of which combined with 105 (N1), 180 (N2), and 210 kg N ha-1 (N3) N application. We found that microbial CUE increased with increasing N application rate. NT increased microbial CUE compared with CT under N1. The bacterial and fungal diversities of NT was higher than CT and N application decreased their diversities in the 0-10 cm layer. The partial least squares path model showed that bacteria diversity, fungal diversity, and fungal community structure played more critical roles in increasing microbial CUE. Furthermore, POC and MAOC under NT were higher than CT and they also increased with increasing N application rate. This could be explained by the finding that increasing microbial CUE induced by N application had the potential to increase POC and MAOC. Overall, N addition is an important pathway to influence microbial CUE, which is mainly regulated by bacterial and fungal diversities rather than their biomass under no-tillage.

Abstract: Land systems in drylands have been experiencing increasing conflicts among different land functions due to ecological vulnerability and growing demands. The improvement of one function is often at the cost of other functions, which causes trade-offs of functions. Understanding land multifunctionality and its trade-offs are prerequisites to alleviate land use conflicts and achieve land sustainability. But research often cannot well address the fuzziness and uncertainty within assessments, and neglect the nonlinear feature when quantifying the trade-offs. Taking the Heihe River Basin (HRB), a typical arid ecologically vulnerable area in China, as the study area, we applied the set pair analysis (SPA) to develop a novel framework for assessing land multifunctionality at a fine scale from the production-living-ecological angle. We then utilized the constraint line fitted with segmented quantile regression to identify the trade-offs among land functions and understand the bidirectional interaction between land systems. The results showed that the overall land multifunctionality in HRB showed an upward trend during 2000-2015, and especially the production and living functions had a larger magnitude. We used the coupling coordination degree to comprehensively indicate the interaction and found that the degree was high in the south and low in the north, which was mainly controlled by ecological function. The effects of different drivers on land functions showed nonlinear characteristics, and thresholds existed for some influencing factors. Our research provides reliable and detailed information to coordinated the development of land systems, which is helpful for sustainable land use and territorial spatial planning.

In this research, enrichment factor (EF) and pollution load index (PLI) were utilized to estimate the features of enrichment and contamination of PTEs in farmland soil. Furthermore, combining the spatial distribution characteristics of potentially toxic elements (PTEs) and positive matrix factorization (PMF) to distinguish and quantify the sources of PTEs in farmland soil, and then the potential ecological risk (PER) and human health risk (HHR) model based on PMF are applied to quantify the ecological and human health risks from different sources. Taking Puning District as an example, four sources of PTEs in farmland soil were quantitatively allocated. For ecological risk, the study area is at moderate ecological hazard level, and industrial activities were the greatest contributor. The mean E_r^i of Hg were 69.82, reaching medium ecological risk level. For human health risks, both adults and children have no evident non-carcinogenic risk in the study area. And natural source was the largest contributor to non-carcinogenic risk, followed by agricultural activities. With regard to carcinogenic risk, tolerable risks of soil PTEs in the study area were limited not only for adults but also for children. Furthermore, compared with adults, the health risks of children, whether non-carcinogenic or carcinogenic, were higher than those of adults, and the trends in health risks for children and adults were similar. A comprehensive scheme combining source contribution and risk assessment is conducive to quantitatively assess ecological risks, health risks and priority pollution sources, thereupon provide effective suggestions for protecting human health and preventing and controlling pollution.

The worldwide diversity of contaminated sites, coupled with a scarcity of available land in urban spatial planning, has led to an increasing political significance for brownfield conservation and re-use to achieve land resource sustainability. In this study, economic or so-called rebound effects of land regeneration, are studied via a global meta-analysis on value fluctuation of surrounding property. To this end, a total of 91 observations from 28 HPM (Hedonic Pricing Model) studies were synthesized to conduct a meta-analysis following a conditional random-effects procedure. The empirical results indicate that, in line with expectations, the conservation and recycling of land resource indeed generate significant rebound in the implicit price of residential houses, especially for those located within 2 kilometers of contaminated sites. Before land remediation and re-use, dwellings closest in distance to contaminated sites experience the greatest value loss. On average, the depreciation in property values within the first 1km distance from a contaminated site is about 8.18%, significantly at the 1% level, while the corresponding adverse impact from 1 to 2 km distance is a 4.8% price premium significantly at the 5% level. The significance of the stigma or rebound effects depend on 12 attributes, in which, house age, location, FAR (Floor Area Ratio) and CBD (Central Business District) variables have the largest impact, of -37.38%~37.5%. From a practical perspective, the findings of this meta-analysis: 1) help refine contributing parameters in HPM studies to evaluate environmental economics; and 2) provide meaningful decision-making support for cost-effective remediation and benefit maximization.

The present study attempts to understand land use dynamics in an area subjected to opencast and underground coal mining for the last few decades in Kotma Coalmines of Anuppur district in Madhya Pradesh, India through geospatial techniques. Land Use and Land Cover (LULC) change detection analysis was performed digitally classifying Landsat 5 (2001) as well as Landsat 8 (2020) satellite data using maximum likelihood algorithm. Results revealed that area under Dense native vegetation decreased drastically (13.74 sq. km) with the gradual and consistent expansion in the activities of coal mines which showed the highest increase in area over time (15.84 sq. km). Bivariate regression analysis showed the positive empirical relationships between vegetation indices and soil physico-chemical parameters. Studies suggested soil and vegetation is degraded over the large mining areas consistently over a long time period. Despite the continuous reforestation activities on mined areas, the decline area under dense vegetation and sparse vegetation over the twenty-year time-scale indicates that the reclamation activities are still in its’ infancy. Land Degradation Vulnerability Index (LDVI) map was generated to understand the extent of decadal land degradation trends and it shows that 8.60 % of the area is highly vulnerable to degradation. The LDI inputs will help the planners to develop alternate strategies to tackle vulnerability zones for safe mining. Monthly estimation of various meteorological parameters was also recorded to generate heat plots for the period 2001-2020. The study concludes that monitoring and assessment of fragile ecosystems are indispensable for holistic environmental management.