Understanding community restoration state and the corresponding assembly mechanism is helpful to assess the restoration measures and predict community dynamics. We collected plots by shrub cover (low, medium and high) in three Caragana mircophylla shrub-encroached grasslands which were fenced since 1979, 1983, and 2003 (fencing duration) in the northern China, to explore the effect of fencing duration and shrub cover on the community restoration by vegetation investigation and phylogenetic approach. There were significant differences in community composition among different fencing duration or shrub cover treatments. Species richness in the site of fencing since 1979 or in the plots of high shrub cover was relatively higher than that in any other sites or plots. By phylogenetic analysis, functional traits were phylogenetically convergent. Based on the standardized effect sizes of mean pairwise distance (SESMPD) ranged from -1.96 to 1.96 in six out of nine plots, which suggested that stochastic processes dominated community assembly. SESMPD were lower than -1.96 in the rest three plots which indicated that competitive exclusion drove community assembly. These results indicated that the increase of fencing duration or shrub cover could enhance competitive exclusion. The present findings highlighted the importance of shrub in influencing the community composition and community assembly, supporting that shrub-encroached grassland is another stable state in the semi-arid northern China. Therefore, it is essential to distinct shrub-encroached grassland from degraded grasslands when formulating relevant conservation and management measures in the semi-arid regions.

The effects of different straw returning and nitrogen addition levels on soil quality are important for proper coastal saline soil remediation. Two maize/wheat straw returning levels (1.0 × 10 4 kg ha -1 (2S) and 5.0 × 10 3 kg ha -1 (S)) and three inorganic nitrogen addition levels (300 kg ha -1 (N2), 150 kg ha -1 (N) and 75 kg ha -1 (N1/2))—were studied, with 150 kg ha -1 inorganic nitrogen and without straw addition treatment as the control (CK), to elucidate the response of soil physical and chemical properties to the two factors. Dry-sieving technique was applied to fractionate the soils into silt-plus-clay particles (< 0.053 mm, CS), microaggregates (0.053–0.25 mm, MI), small macroaggregates (0.25–2.0 mm, SM), and large macroaggregates (> 2 mm, LM). After four consecutive wheat-maize cycles, different straw and N fertilizer treatments obviously decreased the salinity contents, increased the total nutrient contents, and optimized the soil structure of the saline soil. The saline soil reclamation effects showed significant distinctions among the different straw and N fertilizer treatments. The 2SN2 treatment displayed the greatest effects in regard to decreasing salinity, increasing the total soil nutrient contents and optimizing the soil structure, which resulted in the best remediation effect. Straw returning play a major role in decreasing soil salinity and enhancing saline soil aggregate formation. N fertilizer addition supplies rich nutrients for straw decomposition, and promotes soil microbial growth and reproduction, which brought about C sequestration in coastal saline soil. During the coastal saline soil remediation process in the Yellow River Delta, it is suggested to prioritize straw returning and moderate N fertilizer addition, and live together with moderate P fertilizer application.

The present paper attempts to study the causative physicochemical properties of the soils, which effectively portray its dispersive and deteriorating conditions, which have led to the formation of badlands in the Mandakini River watershed Chitrakoot area, India. Following investigations were made on the soil samples collected from the field: i) grain size distribution ii) various physicochemical properties and nutrient content of the soil. The clay minerals were detected and identified with the X-ray diffraction (XRD), Fourier transform infrared (FTIR), and High-Resolution Scanning Electron Microscopy (HRSEM). The spatial maps of all these parameters were prepared in a GIS environment, and overlay analysis was performed. The results show that the soil has a silt loam texture with high bulk density. The low values of plastic limit, liquid limit, and plasticity index show the non-cohesive nature of the soils. Higher bulk density has decreased the porosity as well as permeability in the soils. This impact on porosity and permeability has reduced the favourable conditions for vegetation, and the soils contain low organic matter. Apart from the bulk density, the presence of calcrete and illitic clay mineral (low in content) has also reduced the permeability of the soils, further increasing runoff. The overlay analysis based on the liquid limit, plasticity index, bulk density, and drainage frequency shows that the area is thoroughly affected by badland processes. Three zones were categorized as severe, very severe, and extremely severe depending upon their conditions gully channel processes.

Implementation of the Natural Forest Protection Project and Grain for Green Programme in China has promoted forest restoration, increased productivity, and enhanced the carbon stocks. However, few studies have characterized temporal and spatial variation in productivity and ecological stability in planted and natural forests and evaluated the factors driving such variation. In this study, we used 1399 permanent forest plots to identify change patters in the productivity and temporal stability of above-ground biomass (AGB) and evaluated the factors driving these changes in planted and natural forests in Sichuan Province, China. The mean temporal stability of AGB was higher for natural forest than for planted forest from 1979 to 2017; While, the productivity of planted forest was higher. The stability decreased at a rate of -0.013 yr-1 in entire natural forest and -0.011 yr-1 in planted forests, and the productivity of natural forest decreased significantly over time, with a slope of -0.0065 Mg ha-1 yr-1 per calendar year. Altitude, latitude, annual precipitation, and stand age dominated variability in the productivity and AGB stability of natural forest. Richness, tree density, and stand age were the determinants of productivity and stability in planted forest. Our results suggest that selective thinning and enriching species richness and forest stand age can effectively balance the productivity and biomass temporal stability of planted forests. Older natural forests still need to be strictly protected under climate change.

Hurricanes are extreme phenomena that affect the coasts of Mexico every year. The economic and biodiversity losses caused by these extreme events are extensive. However, little is known about the effects that these severe weather incidents have on Mexico’s forest conservation and protected areas. A hydrological characterization and regionalization of the storms caused by the rain fields generated by all the hurricanes that touched the Mexican coast from 1966 to 2017 were carried out. Adimensional Huff Curves are proposed to get precipitation hyetograms from which the erosion factor of a storm is obtained; using the Universal Soil Loss Method (USLE). The results made it possible to get the typical precipitation hyetograms in the forests and protected areas, before, during, and after the impact of a hurricane. The proposed hydrological regionalization made it possible to estimate the rainfall intensity in 30 minutes to characterize the start of rain erosion. The method proposed in this research was applied in the 177 Natural Protected Areas (25628239 ha), as well as in the 370 voluntarily designated areas for Conservation (399643 ha), in Mexico. It is concluded that, with the regionalization and the proposed equations, it is possible to get typical hurricane precipitation hyetograms, which would allow us to detail the forest management plans in forests, ecological reserves, and protected areas of Mexico.

High rates of erosion and runoff production on road infrastructure have been documented, indicating that unpaved roads might be significant sources of sediment in catchments. In this paper, the production of surface sediments from unpaved rural roads at different scales is assessed. The study took place in northeastern Brazil, in a semiarid area of the Caatinga biome, vulnerable to desertification. Sediment production data from road surface segments were monitored for two years (2013-2014) under conditions of natural precipitation. By using hydrosedimentological modeling and Geographic Information System (GIS), the sediment budget was calculated at the meso-scale basin (aprox. 930 km²), in order to identify the relative contribution of roads to the sediment balance. Universal Soil Loss Equation (USLE) associated with Maner’s sediment delivery ratio (SDR) equation, proved to be an adequate approach for predicting sediment yield on the road segment scale; the best results were obtained for the road without traffic, due to the non-interference in this segment of external factors, such as traffic and maintenance activities, not explicitly considered in the model formulation. The modeling procedure showed that the roads, which occupy only 0.7% of the catchment surface, were responsible for approximately 7% of soil loss in the area. Furthermore, sediment connectivity might be enhanced by roads, which cross the river network and, therefore, deliver more directly the sediment generated at hillslopes. This is particularly important in the studied environment, where sediment connectivity is low due to limited runoff and the existence of a dense network of surface water reservoir

Soil degradation restricts the development of agriculture and the degree of soil degradation is related to land use type. Quick and efficient evaluation of the degree of soil degradation is needed for the timeous implementation of remedial measures to ensure soil sustainability. Earthworm community characteristics are closely related to soil management practices and soil quality and could be used for evaluation purposes. In this Loess Plateau study, the degree of soil degradation under nine different land use types (natural and planted woodland, shrubbery, and grassland, plus cropland, orchard, and abandoned land) was related to the earthworm community characteristics (density, biomass, and the Shannon-Wiener, Species richness, and Pielou’s evenness indices) using a soil degradation index calculated from soil physicochemical properties determined for each land use type. The earthworm community characteristics associated with a low degree of degradation were significantly higher than those associated with a high degradation degree. Compared to the artificially managed land use types, earthworms in the natural ones showed higher biomass, density, and diversity. The earthworm density, biomass, and Shannon-Weiner index were significantly correlated with soil organic matter and total nitrogen content. These findings indicate that earthworm community characteristics can comprehensively characterise the physicochemical properties and biological characteristics of soils under different land use types. Linear correlations showed a significant relationship between the soil degradation index and the earthworm community characteristics, indicating that the latter could be used effectively to evaluate and represent the degree of degradation of soils on the Loess Plateau over a certain degradation range.

Reclamation has been widely accepted to restore abandoned lands. Most studies focused on the improvement of land reclamation in soil nutrients and microbial activities. However, the effects of reclamation time on bacterial communities of abandoned salt pans are still unclear. The object of this study is to: i) assess the successional change of soil physicochemical properties and bacterial communities in reclaimed abandoned salt pans with different reclamation histories, and ii) figure out the main limit factors on the improvement of soil quality in reclaimed abandoned salt pans. The soils in a farmland (RTBL) and six abandoned salt pans with 1 year (RT1), 2 years (RT2), 3 years (RT3), 4 years (RT4), 8 years (RT8), and 9 years (RT9) of reclamation were sampled to investigate the temporal variation of soil properties, heavy metal content, bacterial community composition, and diversity. Results showed that the soil bulk density (BD), total dissolved salt (SS), median particle size (MMAD) decreased with the increase of reclamation time, while soil nutrient (soil organic matter, total nitrogen, available phosphorus, available potassium) showed an opposite trend. The bacterial α-diversity increased first, then decrease. Land reclamation enhanced the relative abundances of Acidobacteria, Chloroflexi, and Actinobacteria but reduced the relative abundances of Proteobacteria, Gemmatimonadetes, and Bacteroidetes. Compared with RTBL, the soil nutrients and bacterial community structure in RT1, RT2, RT3, and RT4 showed a significant difference.Therefore, reclamation time is a vital driving force for restoring soil physicochemical properties and bacterial communities in abandoned

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.

Evaluating the level of green development of cultivated land (GDCL) and its influence mechanism can provide important support for better promoting agricultural green development and rural revitalization. According to the concept of green development, we construct the evaluation system of “adaptability-vitality-resistance (A-V-R)” and explore the spatial and temporal differentiation characteristics and influence mechanism of China’s GDCL in 2000, 2005, 2010, 2015, and 2020 by using the methods of the Comprehensive Evaluation Model, Standard Deviation Ellipse, Theil Index, and Geographic Detector. The results show that: (1) From 2000 to 2020, the level of GDCL in China was low and improved slowly, increasing from 0.264 to 0.293, showing the characteristics of “W” fluctuation, and the focus shifted from Southwest to Northeast. (2) The GDCL in China has obvious spatial dependence, and the evolution of different types of regions has significant path dependence and spatial and temporal inertia. (3) The regional difference in the level of GDCL in China is greater than that among regions. The hierarchical structure characteristics of Northeast Region > Western Region > Central Region > Eastern Region is prominent, and show an overall increasing trend. (4) Human factors greatly impact the level of GDCL. The interaction of driving factors forms a complex multi-resultant force to jointly build a comprehensive action mechanism of GDCL level driven by demand, economy, science and technology, and ecological block.

The soil carbon (C) and nitrogen (N) dynamic was usually considered as a minor change based on a static process in the sealed soil under decades of impervious surface (IS). However, no systematic studies concerning the soil organic carbon (SOC) and nitrogen (SON) dynamic were conducted under IS in contrast with urban vegetation (i.e., forest, grass). Here we utilized fractional distillation of soils as well as stable isotopic analysis to examine soil C&N cycles after 20 and 30 years of vegetation planting and IS construction in Guangzhou and Shenzhen, Pearl River Delta, China. Soil samples including bare soil (CK) and four land use treatments were split into different chemical fractions. Then we analyzed the C&N content, C/N ratio, δ13C, δ15N, C&N recalcitrant indices (RIC, RIN), and the mean residence time (MRT). We found that the soil C&N increased first (i.e., 20 years) because of enhanced C&N stocks in both labile (LP) and recalcitrant pool (RP), and then stabilized or decreased (i.e., 30 years) with the IS ages in both cities. IS had a lower SOC decomposition rate and thus resulted in the five to ten times longer MRT (about 259–465 years) than that in vegetated soils (about 39–55 years). Moreover, the SOC&SON always showed a decoupling relation in labile pools (i.e., LC and LN) in forests in both cities. The study showed the IS remarkably altered the soil C&N dynamics, showing a great difference in SOC&SON fractions composition and turnover compared with vegetation.

In the Sahel, exacerbated soils degradation is an ecological indicator of ecosystem vulnerability. This study examines the effects of restoration of degraded lands on soils physicochemical properties and adaptability of planted woody species over a period of 4-6 years. It is based on: 1) Physicochemical analyses of soils (granulometry, calcimetry, and organic matter) carried out on 102 samples taken in the upper 10 centimeters of the soil profile of the rehabilitated and control sites, 2) measures carried out for the dimensioning of anti-erosion structures, 3) dendrometric measurements on woody species planting in 20 plots each with a rectangular shape 60 m × 30 m as well as characterization of the structure of their root systems. Physicochemical analyses show an improvement in soil quality and structure thanks to the erosion control measures. The degradation of anti-erosion structures, inferred from the rate of siltation of micro-basins, the subsidence of the bulges, the formation, and extension of the breaches, is strongly influenced by the topography, precipitation, and sandy texture of the soils. The restoration activities have led to the reconstitution of vegetation cover on degraded soils. Based on dendrometric characteristics, height class structure, and root systems architecture, significant differences were observed between woody species planted in anti-erosive structures. Eucalyptus camaldulensis groups of with a tracer root system and high density, have the highest structural parameters resulting from the adaptation of this species on Sahelian degraded lands.

As the important coal bases in northwestern China, the hydrological and ecological environment of Ordos, northern Shaanxi (Shanbei) and Shanxi Province has attracted more and more attention. Terrestrial water storage anomaly (TWSA) and precipitation, as important hydrological elements, play an important role in the distribution and growth of vegetation. In this paper, the Gravity Recovery and Climate Experiment (GRACE) satellite data, Tropical Rainfall Measuring Mission (TRMM) precipitation data, and the Remote Sensing Ecological Index (RSEI) were used to analyze the spatial-temporal changes and coupling relationships of TWSA, precipitation and ecological environment from 2002 to 2020. The numerical results showed the TWSA in the study area has a decreasing trend and the rates are -6.19mm/a, -7.67mm/a and -16.92mm/a for Ordos, Shanbei and Shanxi Province, respectively. On the contrary, the precipitation appeared an increasing trend and the rates are 0.35mm/a, 0.63mm/a and 0.18mm/a for these three sub-regions. It is found that the precipitation is not the main factor causing the variation of TWSA, but the coal mining activities and artificial irrigation activities, which is especially clear in the Taihang Mountains in eastern of Shanxi Province. The ecological environment has been improving, and TWSA and precipitation are the important hydrological factors causing this change. Precipitation is the main reason for improving the ecological environment in three sub-regions on a seasonal scale, especially in summer. The research results are helpful to understand the impact of hydrological changes on the ecological environment, which play an important role in environmental governance in coal mining areas.

In this study, we examined the effects of different mass ratios of aged refuse on Tagetes patula and rhizosphere microbes. The results showed that chlorophyll content and activities of superoxide dismutase, catalase, and peroxidase in leaf tissue increased significantly in plants cultivated in soil:aged refuse mixtures compared with ordinary soil, whereas levels of malondialdehyde and protein carbonyl decreased significantly in soil:aged refuse mixtures. Microbial community analysis revealed that aged refuse is rich in a variety of rhizosphere microbes that contribute to pollutant degradation, although microbial diversity was found to be relatively low. Bacterial genera such as Ferruginibacter, Hymenobacter, unclassified_Gemmataceae, Longimicrobium, Tychonema CCAP 1459-11B, Gemmatirosa, and Rubellimicrobium tended to be enriched to a greater extent in ordinary soil compared with soil:aged refuse mixtures. Correspondingly, bacterial genera such as Emticicia, Caedibacter, Anaerosalibacter, Tumebacillus, Patulibacter, Oceanotoga, Dyadobacter, Chloroflexus, and Acidobacteria bacterium SCN 69-37, Polycyclovorans, tended to be enriched in mixtures with a higher proportion of aged refuse. Functional prediction analysis revealed that rhizosphere microbe functions changed markedly following the addition of aged refuse. These findings indicate that aged refuse may represent a source of environmental stress for plants and modifies the dominant bacterial composition of rhizosphere microbes. The combination of organic or inorganic pollutants, plant physiological stress responses, and rhizosphere microbial community composition may have potential cooperative or dynamic equilibrium relationships. With respect to identifying potential approaches to recycling aged refuse, it will be necessary to focus on selecting optimal mass ratios of aged refuse and ordinary soil to control contaminant exposure.

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.

Soil oil-pollution is one of the most severe environmental issues at present. Shifts of soil metallome and microbiome are essential indicators for risk assessment and remediation of field soil pollutions, but not well studied undergoing the petroleum contamination. In this research, soil samples were collected from a short-term and long-term petroleum-contaminated oil field. The soil physicochemical properties, metallome, microbial community, and polluted and unpolluted soil network were testified. Results showed that the contents of soil total petroleum hydrocarbon, total carbon, total nitrogen, total sulfur, total phosphorus, calcium, copper, manganese, lead, and zinc were increased by petroleum contamination. In contrast, the soil pH was decreased by petroleum contamination regardless of the pollution duration. Petroleum-contamination also reduced bacterial and fungal α-diversity indices. In contrast, bacterial α-diversity was negatively correlated with soil TPH and EC, and fungal α-diversity was negatively correlated with soil EC. Moreover, the relative abundances of Proteobacteria, Ascomycota, Oleibacter, and Fusarium in soil were increased by petroleum contamination. Network analysis showed that number of links, modules and the network invulnerability decreased in PS, followed by the OS group. These results demonstrate that short-term heavy petroleum contamination can cause shifts in soil physicochemical properties, metallome, and microbiome and assemble a less complex and vulnerable soil microbial network. Moreover, natural restoration can hardly amend soil properties and microbial network structure. This research emphasizes that the uncommonly studied soil metallome may play a vital part in the reaction of soil microbial communities to petroleum-contamination and potential application value of synthetic community in bioremediation.

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.

This paper present results on soil contamination with petroleum hydrocarbons (PHs) on soil sorptivity and hydrophobicity under different soil moistures. The micro-infiltrometer method was used in laboratory experiment to determine the soil water repellency index (R) and the water drop penetration time (WDPT) test. The increase in PHs contamination contributed to soil repellency and caused a decrease in water sorptivity. The negative effect of contamination with PHs on soil sorptivity depended on soil moisture and was marked especially clearly after exceeding the critical moisture threshold. However, contamination by PHs did not reveal significant changes when ethanol was used instead of water. The R index and the WDPT test revealed a similar trend, inversely related to the level of soil contamination with PHs. The total amount of water available to plants in non-contaminated soil was 19.04%, while contamination equal to 100 g kg -1 caused a decrease to 6.36%. Hydrophobization of water-conducting pore surfaces by petroleum hydrocarbons severely reduced infiltration and destroyed the existing hydrological system of naturally hydrophilic soil. The almost three-fold decrease in total amount of water has a fundamental influence on increasing the risk of soil drought. The soil water repellency causes a decrease in resistance to droughts and slows the alimentation process of soil water retention. The results obtained indicated that the interrelations presented between the level of PHs contamination, soil sorptivity, water repellency, and soil moisture are key to predicting the environmental effects of contamination and effective soil remediation.