This special issue is the second published after the Global Symposium on Soil Erosion (GSER, 15-17 May 2019, Rome, Italy) and includes contributions dealing with the 2nd theme of the GSER: Policies and practices in action to address soil erosion. While there is a good scientific understanding of the physical measures that can be used to prevent or mitigate soil erosion, the main constraints to progress often relate to policy development and or implementation as well as socio-economic aspects that provide limitations to implementation of sustainable soil management (SSM) practices including those directed to control erosion. There are no right or wrong answers to which policy or approach is most effective. Some combination of approaches needs to be adopted that work in the particular political, cultural, and socio-economic environment under consideration. The papers included in this special issue provide examples, from the national to local level, that could be adapted, or used, to improve uptake and implementation of SSM practices to prevent or reduce soil erosion. Regardless of what policy or plan is developed there has to be effective interaction with the local farmers and land managers as they are key to implementing any actions that will make a practical difference on the ground. Effective policies cannot be developed or implemented without bringing the land managers “on board” and the needs and limitations of the local farmers must be thoroughly understood and considered in any policy or plan development.
Quantifying how multiple ecosystem services and functions are affected by different drivers of Global Change is challenging. Particularly in African savanna regions, highly integrated land-use activities created a landscape mosaic with flows of multiple resources between land use types. A framework is needed that quantifies the effects of climate change, management and policy interventions on ecosystem services that are most relevant for rural communities, such as provision of food, feed, carbon sequestration, nutrient cycling and natural pest control. In spite of progress made in ecosystem modelling, data availability and stakeholder interactions, these elements have neither been brought together in an integrated framework, nor evaluated in the context of real-world problems. Here, we propose and outline such framework as developed by a multi-disciplinary research network, the Southern African Limpopo Landscapes network (SALLnet). Components of the framework such as the crop model APSIM and the vegetation model aDGVM2 had already been parameterized and evaluated using data sets from savanna regions of eastern, western and southern Africa, and were fine-tuned using novel data sets from Limpopo. A prototype of an agent-based farm household model was developed using comprehensive farm survey information from the Limpopo Province of South Africa. A first test of the functionality of the integrated framework has been performed for alternative policy interventions on smallholder crop-livestock systems. We discuss the versatile applicability of the framework, with a focus on smallholder landscapes in the savanna regions of southern Africa that are considered hotspots of global change impacts.
Natural wetland along the coasts of Yellow and Bohai seas provided key stopover sites for migratory waterbirds. However, these wetlands are facing land loss. Understanding how natural wetlands loss influence habitat is an important step for habitat management. Using species distribution model to report changes in area of suitable habitat, and the effects of natural wetland loss on habitat for 80 waterbird species attributed to four functional categories (shorebird, duck, heron, gull), between 2000 and 2015 in the Yellow and Bohai seas. Of 1794.8 km2 of coastal wetland lost to development between 2000 and 2015, most represented tidal flats converted into aquaculture and salt pan habitat, or for construction. Consequently, habitat for 73 of these 80 species has decreased in area over this time period. Generally, the proportional decline in habitat suitable for species of duck was less than it was shorebirds, herons and gulls. The proportional loss of tidal flat habitat that formerly represented suitable habitat for shorebirds, herons and gulls was also significantly higher than it was for ducks. Because more species of duck exploit aquaculture and salt pan habitat converted from tidal flats than do shorebird, heron and gull species, such conversion of tidal flats pose a greater threat to shorebirds, herons and gulls than they do to ducks. Preventing further reclamation of tidal flats and managing artificial wetlands are priorities for waterbirds conservation, especially for the species ducks.
Periphyton plays an indispensable role in coastal saline-alkali land, but its function is poorly understood. Soil physical and chemical properties (pH value, salinity, soil organic matter), enzyme activity and microbial diversity (based on 16s rDNA, ITS and functional genes) were measured in periphyton formed on rice-growing coastal saline-alkali soil modified by a new type of soil conditioner. The results showed that the content of organic matter and catalase activity in periphyton were significantly higher than in the unplanted control soil. Soil pH and salinity were decreased in periphyton compared to the unplanted control soil. Based on the relative abundance, bacterial genera Desulfomicrobium, Rhodobacter, cyanobacterium_scsio_T−2, Gemmatimonas, and Salinarimonas as well as fungal genus Fusarium were more abundant in periphyton than the unplanted control soil. In terms of functional genes, the cbbM and cbbL sequencing showed higher abundance of Hydrogenophaga, Rhodovulum, Magnetospira, Leptothrix, and Thiohalorhabdus, whereas the nifH sequencing indicated higher abundance of Cyanobacteria in the periphyton compared to the unplanted soil. The relative abundance and community structure of soil microorganisms were improved by periphyton, thus reducing soil salinity and pH, increasing soil organic matter and enzyme activity. This indicated that the periphyton can improve the conditions and offer a suitable environment for plant growth in coastal saline-alkali soil.
Mapping and monitoring the Trees outside Forests (ToF) is gaining significance in the scientific community as they provide critical ecosystem services such as protecting soil and water resources, wildlife habitat, energy efficiency etc. Also, quantifying ToF can provide useful information on emissions estimation in the Agriculture, Forests, and Other Land Use (AFOLU) category of the Intergovernmental Panel for Climate Change (IPCC). Despite the importance of quantifying ToF, very few studies have attempted to quantify them in India’s natural resource inventory programs. In this study, we focus on Haryana state, India, to map ToF using very high-resolution (VHR) Indian Remote Sensing (IRS) satellite data. Haryana’s landscape is highly interspersed with croplands and ToF, thus providing a challenging environment to test VHR satellite data’s ability to quantify the diversified landscape structure. We specifically used Cartosat-1 panchromatic (2.5m) and Multispectral LISS IV (5.8m) datasets to quantify the vegetation and build a much-needed database on ToF. We used a novel classification scheme based on the geometry, i.e., point, polygon, or polygon formations, to quantify ToF at 1:10,000 scale. Our results suggest ToF with the point, area, and linear block formations of about 2,774,531, 20.51, and 128.83 sq. km, respectively, accounting for ~3.38% of the total study area . Our study highlights the usefulness of VHR satellite data and fused imagery to quantify ToF in highly diverse landscapes, with the case study in Haryana State, India. The results will help address vital ecosystem services from ToF, including greenhouse gas emissions quantification from the AFOLU category.
Saline-alkali soils are widely distributed in China, affecting plant growth and sustainable development of ecosystems. This study characterized the effects of planting Melia azedarach L. on chemical properties and microbial communities in saline-alkali soils [bare (CK), bulk (BS) and rhizosphere soil (RS)]. Compared with the bare soil, planting Melia azedarach L. lowered salt content and concentrations of extractable Na, K, Ca, Mg and Cl-, but significantly increased organic matter, total nitrogen, total phosphorus, available phosphorus, soil urease activity and alkaline phosphatase activity in the rhizosphere soil. High-throughput sequencing results indicated that bacterial richness and diversity decreased in the order RS>BS>CK. The richness of fungi was ranked RS>CK>BS, and their diversity decreased in the order CK>RS>BS. The three dominant bacterial phyla were Proteobacteria, Actinobacteria and Bacteroidetes, and the three dominant fungal phyla were Ascomycota, Basidiomycota and Glomeromycota. Redundancy analysis indicated that total phosphorus concentration and alkaline phosphatase activity significantly influenced bacterial diversity, whereas soil Ca and Mg concentrations were closely related to the fungal community diversity. In conclusion, planting Melia azedarach L. improved soil properties, increased the diversity and richness of soil microbial communities, and thus ameliorated the saline-alkali soil.
Shrub encroachment (SE) has been occurring and studied worldwide over the last century. What remains to be investigated is how soil and vegetation characteristics vary under canopy of different species of shrubs for restoration goals. Thus, this study aimed to compare the effect of three shrub species (Amygdalus scoparia, Ebenus stellata, and Daphne mezereum) on soil and vegetation characteristics under their canopies in semiarid rangelands in Iran for restoration purposes of degraded areas. Fifteen sites were randomly selected in such three shrub species which were found close to each other in each site. Soil and vegetation characteristics were measured under the three shrubs, comparing with outside the shrub canopies (control). One-way ANOVA and non-metric dimensional scaling were used to clarify the differences of the effects of different shrub species on sub-canopy soil and plants. The results indicated that the effect of different species of shrubs on soil properties was not equal, more pronounced by A. scoparia. Similarly, the highest value of herbaceous Shannon-Wiener diversity index was recorded under A. scoparia (2.07) as compared with D. mezerum (1.76), E. stellata (1.41). The highest and lowest values of Menhinick richness index were observed under A. scoparia (3.43) and E. stellata (1.46), respectively. Compared with two other shrubs, a taller canopy in A. scoparia (3.50m vs. 2.60m and 1.83m) probably led to greater litter input by the shrub. Different effects of different species of shrubs on sub-canopy soil and vegetation should be considered in the restoration projects of degraded semiarid rangelands.
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.
Decomposition of forest litter plays a major role in nitrogen (N) dynamics in soil. But to which extent that forest litter affects soil N and how much soil N is derived from the new litter remains unknown. An in-situ soil column experiment with 14-month litter decomposition was conducted to examine the effect of litter retention on soil N dynamics in a typical forest of subtropical China in 2018. Litter removal in the soil column was used as a control treatment, while natural litter or identical amount of 15N labeled litter was added to soil columns as litter retention treatment. The results showed that litter removal caused a continuous decrease in concentration of soil soluble organic nitrogen (SON) in the first 5 months, and then SON began to accumulate and its concentration went up in spring showing obvious seasonal change. Litter retention accelerated the reduction of soil SON concentration in the first 2 months, while maintained a high concentration after that period. Soil NH4+-N derived from litter was nitrified rapidly, and newly formed NO3–N was quickly immobilized or lost. Only 1.8% of soil SON came from litter N and 98.2% from indigenous soil N under the decomposition of labeled litter. Litter provided supplementation N to form new soil SON continuously, however, only a small part of SON was relatively stable, and SON played the role of reserve and regulatory pool. Soil SON and TN were formed after long-term litter accumulation and decomposition.
Benzo[a]pyrene (B[a]P) as a representative polycyclic aromatic hydrocarbons is concerned by global scientists in various fields, but its biological and biochemical actions in soil-wheat systems are still rarely reported. The B[a]P as a ubiquitous soil pollutant possesses varied contents in real environment, and herein was studied in systems of soil and wheat to obtain relative results to reveal their variations in different systems. Its bioavailability (extractability and bioaccumulation) and basic biological toxicity were tested based on three typical soil types (red, black, and brown) in China and spiked amounts (0.1, 1, and 10 mg/kg) with several orders of magnitude. Results showed that B[a]P concentrations in soil-wheat systems extracted by HPCD were insignificantly (p > 0.05) higher than Tenax-TA, and varied with soil types and spiked concentrations. Besides, the root and shoot length were mostly inhibited, in a range of -21.85%-26.35% and -0.48%-54.85%, respectively, by B[a]P in different soil types and increased with its increasing concentration. Comparatively, higher bioconcentration factor and translocation factor values were observed under lower group in red soil-wheat systems, and higher spiked groups in black and brown soil-wheat systems. Moreover, inhibitive effects posed by B[a]P were mainly targeted at wheat shoots in these soils. The simultaneous studies provided a comparable knowledge of B[a]P in ecosystems of different soil types combined with different plant species due to lots of variations, further to serve for contaminated soil remediation and sustainable agricultural management.
The restoration of surface mining is a key to meet the global ecosystem restoration target. With increased data accessibility and computing tool capabilities, it becomes possible to expand mine restoration monitoring from single mine sites to multiple mine sites on a large scale. This study constructed a new index, Mine Landscape Restoration Index (MLRI), by coupling Land Surface Temperature (LST) and Enhanced Vegetation Index (EVI) to simultaneously monitor the restoration of regional multiple mine sites. We analyze historical and future trends of restoration using Mann-Kendall test, Sen’ slope, and Hurst exponent for MLRI time series. The restoration effects of 46 surface coal mine sites located in the northwestern ecologically fragile region of China from 2000 to 2019 were assessed, based on 3675 Landsat images on Google Earth Engine. The results showed that MLRI was effective in identifying restoration areas and processes in surface mine sites, which was validated by high-resolution images and field investigation of mine samples. The restoration area overall percentage was significantly higher in mines started mining before 2000 than after 2000. According to the restoration effects, we clustered the 46 sites into high, medium, and low restoration area percentage clusters with 13, 11, and 22 mine sites, respectively. Individual clusters have aggregation characteristics within each mine region, but are distributed irregularly across the different six mine regions. This study provides a new approach to monitoring the restoration of surface coal mine sites and inform government managers in developing mine restoration programs and sustainable mining development plans.
We investigated the soil physicochemical property and arbuscular mycorrhizal fungi (AMF) resilience to the degradation and deforestation of the Chilimo dry evergreen Afromontane forest (CF). Topsoil (1-10cm) physicochemical property, AMF spore abundance (SA), and AMF infectivity were determined across four land uses, viz., natural forest (NF), shrubland (ShL), cropland (CrL), and grazing land (GrL). According to the PERMANOVA and NMDS results, soil physicochemical property was resilient to degradation (NF-ShL conversation) but not deforestation (NF-CrL or NF-GrL conversions) of CF. The one-way ANOVA results indicated that most soil physicochemical variables were significantly (p<0.05) affected by land-use change. Soil organic matter and total nitrogen, in particular, reduced significantly (p<0.05) by up to 48 and 57% due to NF-CrL and NF-GrL conversion respectively. Whereas SA was found to be resilient to both CF degradation and deforestation, AMF infectivity was resilient only to NF-CrL conversion. Generally, our results did not show a similar pattern in soil physicochemical property, SA, and AMF infectivity resilience to degradation and deforestation. However, in the case of NF-GrL conversion, both soil physicochemical property and AMF infectivity exhibited significantly (p<0.05) low resilience. Based on our results, we conclude that soil physicochemical property and AMF are important factors to consider in CF restoration planning. When planting sites are either the croplands or grazing lands, soil amendment could be recommended. AMF inoculation, however, could be recommended when the planting sites are grazing lands. These recommendations may also apply widely to dry evergreen Afromontane forests restoration but additional studies are required.
Rural communities in the drylands of Sub-Saharan Africa (SSA) derive their livelihoods primarily from their natural resource base. Unprecedented changes in these environments over the past few decades are likely to intensify in the future and land users need to develop sustainable adaptation strategies. This study aims to identify land use and land cover (LULC) changes and their drivers in a Sub-Saharan dryland, between 1986 and 2017, by integrating local knowledge and remote sensing analysis. Local knowledge and environmental perception are used as the basis for defining LULC classes and for training and validation of change detection. This study identifies bush encroachment into former pastures as the dominant LULC change with an increase of woodland by 39 % and a decrease of grassland by 74%. This process is perceived as severe degradation by local respondents and is linked to changing management regimes and unreliable rainfall patterns. Deforestation and woodland thinning can be traced back to increased habitation and farming, though the local community also identifies charcoal production as a driving factor. The integration of remote sensing and local knowledge provides a holistic view on LULC change in Pokot Central, Kenya, and offers a solid base for site specific and actor-centred management approaches necessary for sustainable pathways of drylands.
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.
Wind erosion is the main form of soil erosion in arid and semi-arid areas. It leads to soil loss and land degradation, which aggravates ecosystem vulnerability and threatens regional sustainable development. The assessment of wind erosion and the study of its driving factors can reduce soil wind erosion and provide decision-making assistance to solve environmental problems. Southern Africa is affected by severe soil erosion, which has brought a series of development problems, such as food crises and poverty. This study used meteorological and remote sensing data, and the revised wind erosion equation model to explore the temporal and spatial dynamics of soil erosion in southern Africa from 1991 to 2015. The impact of climate dynamics on soil wind erosion was also analyzed. The results showed that wind erosion fluctuated during the study period, and it first showed a downward trend and then stabilized at a relatively low level after 2010. Soil wind erosion across 66.65% of the study area significantly decreased (p < 0.05) and near-surface wind speed was the most important factor. The change in wind speed had a positive impact on soil wind erosion across 68.18% of the area. Temperature and precipitation were significantly related to soil wind erosion over 18.96% and 24.63% of the area, respectively. Both can also indirectly affect soil wind erosion through their effects on vegetation cover. This study will help decision-makers to evaluate areas that are at high-risk from soil erosion in southern Africa and enable them to effectively protect fragile ecosystems.
Soil salinization seriously affects the movement of water in soil which then affects soil stability and sustainability in industrial and agricultural development. Fly ash, one of the most discarded solid wastes from coal-fired power plants, has been widely used as a recycled resource in recent years. The basic components of soda soil have been investigated through laboratory experiments. Soda soil samples with different amounts of fly ash are tested to study the changes in the characteristics of the material due to changes in water content and evaporation rate during drying. Changes in fractal and crack intensity factor are calculated based on digital image processing technology. The results show that the residual water content of soda soil increases from 8.55% to 16.22% with increases in the fly ash content. Fly ash can improve the water retention capability of soda soil, with a rate of increase of 89.68%. The average length of the surface cracks gradually decreases with increase in fly ash content, which indicates that fly ash can effectively inhibit the development of surface cracking in soil. The rate of cracking is an important measure for characterizing the development of cracks by measuring the area of the cracks. The crack area gradually decreases with increase in the fly ash content with different rates of cracking. The rate of cracking with a fly ash content of 10% is relatively slow, which indicates that 10% fly ash can effectively reduce cracking in soda soil thus resulting in a high residual water content.
Sanjiang Plain is the largest area of freshwater wetland in China. Due to agricultural development, a large volume of groundwater in this area has been extracted over the last few decades, resulting in wetland degradation. In order to provide information for the development and protection of wetland ecosystem, investigations examining processes of wetland degradation are important. The aim of this work is to assess the impacts of wetland degradation on the communities of soil microbial community under four different types of degradation wetland including swamp meadow (SW), meadow wetland (MW), paddy farmland (PF), and cropland (CL) in Sanjiang Plain. Using both 16S and ITS rRNA gene amplicon sequencing to evaluate the fungal and bacterial diversity and composition. The dominant fungal phyla and bacterial were Ascomycota and Proteobacteria in this study, respectively. In addition, wetland degradation remarkably augmented the partial affluence of Chloroflexi and Gemmatimonadetes, but the partial affluence of Proteobacteria and Verrucomicrobia significantly diminished. Bacterial Shannon index of SW was lower than those in other sites. While, fungal diversity had no significant differences under different types of degradation wetland. Along with the wetland degradation, such differential reactions of the dominant phyla microbial and diversity were notably coordinated with TP, TK, AK, and SOM, which were the most essential criteria influencing the soil microbial communities. Generally, these outcomes suggested that wetland degradation could result in variations in soil microbial community composition structure. These changes could be used as an early warning signal for the degradation wetland in Sanjiang Plain.
Globally, urban wetlands are facing immense pressure of land use land cover changes (LULCCs) and associated water quality degradation that is severely affecting the trophic status of these pristine ecosystems. This study analyzed water quality degradation resulting due to the land system changes in the vicinity of Khushalsar, an urban wetland, in Srinagar city from 1980-2017. The analysis of satellite data indicated that the wetland has lost ~18.1 ha from 1980-2017. During the same period the urban area within the wetland increased from 0.2% to 16.5%. The land cover changes assessed in the immediate vicinity of wetland indicated an increase of 119% in built-up and 62.8% in roads. The analysis of surface water quality of the wetland showed much greater degradation of Khushalsar wetland. The Trophic State Index (TSI) ranged from 73.4-84.6 thereby indicating the hyper-eutrophic nature of the wetland. A snapshot of comparative water quality data from 2002-2018 revealed that the mean concentration of NO3–N increased from 219-433 µg L-1 and total phosphorus (TP) increased from 135.4-1236 µg L-1 indicative of continuous nutrient enrichment. Hierarchical cluster analysis (HCA) clustered 8 sampling sites into 4 groups based on likeness of water quality characteristics. Similarly, discriminant analysis (DA) showed the formation of similar patterns of clusters, authenticating the outcomes of HCA. Wilk’s λ quotient dispersion highlighted the role of nutrients and ions in the development of clusters. Principal component analysis (PCA) formed three principal components (PC’s) accounting for a cumulative variance of 90.61%.