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.
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.
Violence in Rakhine, Myanmar forcibly displaced nearly one million Rohingya who took refuge in Cox’s Bazar–Teknaf peninsula of Bangladesh. Initially, nearly 2,000 ha of forested lands had to be cleared to accommodate them in an area, that is ecologically very sensitive. Fuelwood collection and illegal logging have become widespread since their arrival, causing severe environmental degradation, including loss of a vast amount of forest cover. To devise conservation strategies of a highly sensitive ecosystem, it is imperative to understand the degree of forest cover deterioration and associated impacts related to Rohingya emigration. This study employed satellite images to monitor and model spatiotemporal pattern of forest cover degradation, and loss of ecosystem function in the peninsula. Supervised classification method was used to derive multidate land use/cover data which was then utilized to monitor spatiotemporal pattern of forest cover change from 2017–2019. Dynamic modelling was performed to predict changes in the forest covers using markov cellular automata. Analysis revealed that 3,130 ha of different forested covers were transformed into either refugee camps or degraded forest cover between 2017 and 2019. Prediction showed that around 5,115 ha of forest may experience loss from 2019–2027. Furthermore, above ground biomass and carbon stock estimation indicated a consistent loss, which is likely to swell if present rate of deforestation continues. The findings of this work have considerable implications in developing conservation decisions, priority interventions and public policies to save an ecologically sensitive area.
This paper examines land use patterns of rural households and the association with food production and income across three different zones of various forest proximity across a landscape gradient (remote, intermediate and on-road) in the Chittagong Hill Tracts region of Bangladesh. We conducted in-depth semi-structured surveys of households (175-300) and farm owners (30) to collect information on people’s perceptions of land use change, present land use patterns and contributions to food production and income. Our research found that more than half of the surveyed households experienced a decline in the land available for food production over the past 30 years. The land use patterns revealed decreasing crop lands (mainly swidden farms) and an increase in areas of planted trees. However, household use of the reduced crop land has not affected food production in the on-road zone, whereas the diversity of food sources has declined. People living in more remote areas used larger areas of crop (swidden farms) and fallow lands, fruit orchard and accessed natural forest lands that provide a diverse reservoir of food sources. The current land uses contribute to variations in annual household income, with remote dwelling people earning less to those living in the intermediate and on-road zones. In summary, this transition of land uses over three decades and changes in income and food availability cannot be generalised across the region because of zone specific differences. We recommend a broader and context-reliant landscape management approach in consideration of the diversity of forest and tree benefits.
In the last two decades, the productivity of Rice-wheat cropping system in the upper Indo-Gangetic Plains of India has stagnated and now in a declining trend. As a result, farmers shifted to a different cropland grown systems so as to achieve a higher net productivity. This study aim to assess as how nutrient index (NI), microbial diversity and soil quality changed after replacement of rice-wheat by vegetable (VGS), pulse (PGS), potato (PoGS) and mustard (MGS) grown system. An analysis of 307 soil samples from various croplands revealed a soil pH range of 6.58-8.87 with 75.3% soils under low category of mineralized N (MN) resulting in its low NI (<1.67). The highest NI, enzymatic activity and microbial biodiversity was recorded under PGS, which restored 34.2, 24.1 and 10.2% greater SOC, carbon substrate oxidation rate and MN than PoGS, respectively. The diversity indices were the highest in PGS followed by VGS, but soil quality index was 0.783 (VGS), 0.771(PGS), 0.695 (WGS), 0.663 MGS), and 0.647 (PoGS). The silt content, SOC, Zn, total N, acid phosphatase activity (ACP), available P and total culturable fungi were the key soil indicators across the cropland grown systems. Among the cropland systems, silt content, SOC, total N and ACP were the main soil indicators for PGS, whereas, silt content, SOC, P and Zn were the ideal indicators for VGS that affected microbial dynamics and soil quality. Overall, it is concluded that PGS maintained higher nutrient index, microbial and functional diversity, but VGS improve greater soil quality.
There is limited understanding about agricultural land dynamic across global drylands and the impacts of different agricultural land transitions on ecosystem productivity changes. This study attempted to fill this gap by examining the agricultural land changes and net primary productivity responses in drylands. A data-driven assessment of the effects on the ecosystem productivity of individual agricultural land displacement was carried out using three methods: the mean difference method, a newly introduced ridge-regression method, and a proposed method based on actual change excluding climate impact. Increases in productivity were accompanied by agricultural land transitions from natural land covers, expected forests. The agriculture expansion mainly replaced sparse vegetation and grassland, and increased the overall productivity of the dryland ecosystem. Mean difference method and ridge-regression method over overestimated the NPP increase caused by agricultural land expansion. Land use change contributed more than 70% to increase in net primary productivity in new agricultural area. But land use change effects less on total productivity in drylands than climate change. Monitoring agricultural land dynamics and distinguishing productivity changes caused by different agricultural land transitions is helpful to the targeted management and sustainable development of agriculture in drylands.
In desert ecosystems, the desertification process is characterized by increasing attenuation of plant productivity and deterioration of soil habitats, leading to enhanced environmental stress gradients for soil microbiomes. Despite the significance of microbial communities for multifunctionality in terrestrial ecosystems, the feedback dynamics of microbiomes and their contributions to maintaining subsurface soil multifunctionality as desertification progresses have yet to be evaluated. Here, we used three sites with different desertification stages and investigated the variation trends of microbiomes in soil profiles (0-100 cm) and their contributions to regulating multifunctionality. We first confirmed that multifunctionality did not exhibit a significant difference between superficial soils (0-20 cm) and deep soils (20-100 cm) and slightly decreased as soil depth increased throughout the entire profile. Desertification progression drove distinct variation trends of microbiomes in vertical soil profiles. Soil bacterial communities received on average more positive and progressive feedback from desertification development than fungal and archaeal communities, characterized by significant variation in bacterial alpha- and beta-diversity and slight variation in fungal and archaeal alpha- and beta-diversity. The most abundant phyla in the microbiomes did not vary between the superficial and deep soils at any desertification stage. Significant declines in microbial clades within Acidobacteria are an important feature as desertification proceeds. Particular microbial taxa rather than total microbial diversity best predict and explain the vertical profile variation in soil multifunctionality in desert ecosystems. Our results highlight the significance of microbial community composition in subsurface soils for regulating multifunctionality in desert ecosystems.
Converting alfalfa (Medicago sativa L.) into cropland (rotation cropland, RC) is a common way of land use to reuse degraded alfalfa pasture. However, it is a big challenge for RC to achieve high productivity and maintain high soil organic carbon (SOC) achieved by previous alfalfa. Here, we conducted a nine-year field experiment, with continuous cropland (CC) under plastic film mulching as reference, to evaluate soil moisture restoration, crop productivity, and SOC in RC also under plastic film mulching, in the case of fertilization and non-fertilization, respectively. SOC and total soil N in the alfalfa pasture before conversion were 12.3% and 7.7% higher, but the available P and inorganic-N were 59.2% and 71.5% lower than in CC, respectively. The crop yield and biomass were not significant between RC and CC following the second year of conversion in both fertilization and without fertilization cases. The SOC and total soil N in RC with fertilization were similar to the previous alfalfa pasture throughout the nine-year experiment, while decreased in RC without fertilization by 8.3% and 7.5% after the nine years. Soil moisture in RC at 0-0.6 m restored to the level of CC only one year after the conversion, and restored from 77.6% and 56.2% of CC to 95.3% and 69.2% at 0.6-2 and 2-5 m through nine-years after conversion. These findings help to dispel the worries about the long-term low production and rapid decline of SOC in RC and support for sustainable high-productivity and high SOC sequestration in dryland farming.
The direct characterization of the spatial distribution of elements and compound binding of salt-organic associations in soil is imperative for understanding the mechanisms of organic matter decomposition and nutrient release in soil degradation and development processes. Modern spectroscopic techniques provide a feasible method for analysis at the microscale. In this study, mid-infrared attenuated total reflectance spectroscopy (FTIR–ATR) was used to obtain molecular functional group information, laser-induced breakdown spectroscopy (LIBS) was apply to obtain micro-level distribution features of elements in soil, and two-dimensional correlation spectroscopy (2DCOS) analysis was conducted to illustrate the binding combination features of mineral-organic associations in salinized from the Hetao Irrigation District in China. The results showed that the distributions of Mg, Ca, Na, and K were heterogeneous at the micro-level; the spatial distributions of Mg and Ca showed a significant correlation (r = 0.90***), while K displayed a negative correlation with the SOM contents. In soil with lower SOM contents, the elements were distributed at the top of the ablation area and enhanced with the increasing SOM content, which reflected the trends of the SOM layer thickness outside the mineral–organic associations at the micro-level. Furthermore, 2DCOS analysis suggested that the hydrogen bonds in silicate groups were stronger than those of organic functional groups, such as C=O/C=C, when combined with salt-related compounds, and Mg, Ca, Na, and K did not originate from clay mineral compounds in salinized soil, but partially originated from deposited organic associations.
Over the past 90 years, anthropogenic degradation of soil caused by alkaline, magnesium-rich dust deposit has presented a serious problem near magnesite processing factories in Jelšava and in Lubeník (Slovakia). The objective of this study was to investigate the chemical and biological soil properties in 14 sampling sites at different distances from factories, and based on the results, to propose further use of affected land. Results revealed that the available Mg 3–68 fold exceeded very high content for texturally medium soils at all grassland sampling sites, and areas close factory contained up to 14.4–17.4 g kg-1. Higher excess of available Mg caused significant increase of soil pH (up to 9.39) and worsened the conditions for the growth of vegetation. As a result, lower stock of newly formed organic matter (0.50–0.96 g kg-1 of labile carbon) with consequently weaker enzymatic activity occurred. Therefore, enrichment by organic matter provides a measure to support the biological activity of soil. The content of monitored heavy metals (Zn, Cu, Pb and Ni) was not related to Mg and did not influence the enzymatic activity of soil. Because alkaline emissions have decreased by 99.8% since 1970, the application of classical measures (mechanical removal of the Mg-rich crust, incorporation of gypsum and manure to the soil), or newer methods (growing of Mg hyper-accumulating plants) can offer more lasting positive effects than those of 50 years ago. This study concluded that Mg-rich, alkaline dust deposition causes long-lasting anthropogenic soil degradation.
Tobacco production and curing is the single most important contributor to soil degradation and deforestation. To minimise the environmental effects of tobacco production, the environmentally friendly, and energy-efficient rocket barns technology was developed. In spite of its energy saving and environmental benefits, the adoption of rocket barns remains low and understudied. This paper assessed farmers perception and factors affecting the adoption of rocket barn technology. Data was collected using in a cross-sectional survey using structured questionnaires were from 242 Flue Cured Virginia (FCV) tobacco farmers in Uganda. Analysed was done using SPSS and STATA software. Results show that the adoption of rocket barn technology was low, at 12%, with farmers. Farmers perceived adopting the rocket barns technology to be risky and costly. Experience, training, distance to wood fuel, access to extension information, and benefits and risk perceptions were the major determinants of adoption of rocket barns technology. Promotion and adoption of rocket barns technology will require concerted sensitization and training of farmers on the environmental benefits of rocket barn technology. Emphasis such efforts should target the relatively young and inexperienced FCV tobacco farmers.
We established three simulated erosion severities with topsoil depths of 10, 20 and 30 cm in a Mollisol farmland under a maize-soybean rotation system with no-tillage. After three consecutive years of field experiment, the decrease in topsoil thickness from 30 to 10 cm resulted in 9−22% of decrease in maize yield but not soybean. Compared to the 30 and 20-cm topsoil thickness, the 10-cm topsoil significantly lowered root and shoot biomass of maize at the jointing (V7) and milk stages (R3) and of soybean at the mid-seed filling stage (R6). Compared to the 30-cm topsoil, the 10-cm topsoil decreased available nitrogen and phosphorus in soil by 42% and 36% under maize, and by 25% and 19% under soybean, respectively, while the shallow topsoil also decreased N, P and K uptake per unit root length with the decreases being less for maize than soybean. Compared to the 30-cm topsoil, the 10-cm and 20-cm topsoil significantly increased the activities of urease, phosphatase and invertase in maize-grown soil, but not in soybean-grown soil except for the activity of urease in 10-cm topsoil. Maize was more sensitive to soil erosion than soybean due to the greater decreases in soil nutrient availability and its capability of nutrient uptake. The greater stimulation of nutrient mineralization processes in soil did not alleviate the nutrient constraint to maize yield under severe erosion conditions.
Insect herbivore has great impacts on biogeochemical cycling in forest ecosystem, but experimental tests on the herbivory-decomposability relationship at the inter-specific level are rare. We conducted a 400-day field decomposition experiment in a temperate mixed deciduous forest and measured mass remaining rate, decomposition constant, total loss of carbon (C) and nitrogen (N) of litter leaf with/without obvious damage by chewing insects for different tree species. We found that herbivory effect on initial litter quality (C: N ratio) varied with species, showing a markedly negative effect on M. alba (-5.78%) and positive effect on Q. acutissima (+5.35%). Herbivory damage increased decomposition constant for M. alba and L. formosana with higher special leaf area, but decreased it for D. kaki and Q. acutissima with lower special leaf area. The contrasting effects of insect herbivory on litter decomposition could be attributed to the variability of litter initial quality caused by herbivory. Our finding that herbivore damage showed inter-specific variability in both litter quality and decomposition rate suggests that herbivory induced feedbacks to nutrient cycling and ecosystem function should be estimated at the species level in multi-species mixed deciduous forest.
The overarching goal of this study is to test innovative monitoring strategies for agricultural properties at watershed towards effectively locating erosions and correcting them, through the implementation of changes in soil management strategies. The purpose is to recover and restore degraded areas, and promote conservation agriculture. The results are, assessed by remote sensing and water quality indicators. In 2019, twelve years were completed of inspection/monitoring at Rio do Peixe watershed. From 2007 to 2017, 14,076 ha, were inspected at Vera Cruz sector, using the Conventional CDA methodology, with 94 properties having been notified. In Ocauçu, a total of 82 properties were notified, in a total surface of 9,027 ha. In Marília, the Innovative CDA Methodology was used, which allowed the inspection and rehabilitation of 52 properties, across 27,775 ha, from 2017 to 2018. After the notifications, the owners presented the conservationist technical projects for each property, which were, implemented using conservation practices, such as: improvement of vegetation cover and crop rotation, to control laminar erosion; and agricultural terracing, divergent channels and containment basin, to control gullies erosions. This work promoted a transformation from degrading agriculture to conservation agriculture, with degraded pastures having been altered into agricultural areas, with the implementation of the No-tillage. Pastures were recovered through the Integrated Crop-Livestock System, and occupancy rate was increased by 31%. This work has demonstrated to benefit Watershed farmers, by increasing their productivity and consequently the profit, as well as the local communities, improving the quality of water that supplies the region.
Little information is available about the effects of different species of shrubs on the composition of the soil seed bank (SSB) in semiarid regions. We determined the role of three dominant shrub species on SSB characteristics and evaluated their potential for their possible use in rangeland restoration projects. Fifteen sites, each containing three shrub species (Amygdalus scoparia, Daphne mezereum and Ebenus stellata) and a herbaceous patch (control) in close proximity, were sampled and their SSB density, species richness and diversity at 0-10 cm depth were determined. The results showed that the density of the SSB was highest under A. scoparia (1133 seeds per m2) and lowest in herbaceous vegetation (110 seeds per m2). Species richness and diversity of the SSB was significantly greater under E. stellata than under the other shrubs and control. This study revealed that the extent to which vegetation affected SSB characteristics did not only depend on the presence of shrubs, but also on the species of shrub. These different roles of different species of shrubs on SSB are advised to be considered in the restoration of degraded areas through planting of shrubs in semiarid regions. Planting and the extension of E. stellata cover in degraded sites could be of priority due to its prominent role in herbaceous SSB reservoir and species diversity and richness.
Land serves as a vital production resource, and therefore, land planning plays an important role in sustainable land-use design. Increasing the global population alters landscapes via land-use and land-cover change across different landscapes, including the drylands. Iran includes large areas of dryland, where the population increased by 60% from 1985 to 2016. Further population increase in Iran would require more land resources to be allocated for human needs. However, the pace and patterns of these changes remain unclear. The aim of this study was to map land-cover change from 1985 to 2016 and predict future land-cover change in the Zayandehrood ecologic sub-basins of Central Iran. By using multiseasonal Landsat imagery, nine thematic classes were mapped with a random forest classifier for 1985, 1998, and 2016 with an overall accuracy of 80% for each period. Classification results revealed that from 1985 to 2016 residential areas doubled and industrial areas increased at the expense of rangelands. Our study also revealed cropland expansion at the expense of rangelands, cropland abandonment and contraction of croplands due to residential and industrial development. Prediction of changes by 2036 with a multi-layer perceptron neural network and Markov chain analysis revealed further expansion of industries and residencies particularly nearby the protected areas such as Ghamashlu Wildlife Refuge. Predicted contraction of some degraded agricultural lands and concomitant agricultural expansion in the agricultural frontier by 2036, underscore the importance of sustainable land management in highly arid areas of Iran and improvement of the strategies for the protection of rangelands.
Globally, temperate grasslands have been significantly altered and subsequently degraded as a result of increased human population, urbanisation, and agriculture. Weeds now dominate most of these ecosystems, resulting in the loss of ecosystem services, reduced carrying capacity for farmers, and loss of habitat for native animals. This paper reviews the literature of temperate grassland restoration efforts from across the globe, and observes what techniques and combinations have been used successfully and unsuccessfully to reduce weed dominance and promote native recruitment and establishment. The findings of this review clarify that weed management should be ongoing in all projects, while optimal revegetation methods and grazing regimes are specific to site location and study scope. There is a need for an increase in long-term monitoring of restoration projects in order to make assumptions with greater confidence.
The effects of forest conversion from natural forest to agricultural system on soil microbial composition still need further study. Especially, impact on soil function after forest conversion is not yet known. In this study, by using metagenomic sequencing as well as 16S and ITS sequencing technology, we evaluated the soil microbial composition, diversity and functions based on a large number of soil samples of tropical rainforest and rubber plantation across the whole island of Hainan, south China. The results showed that (1) forest conversion changed microbial composition from bacterial groups of Proteobacteria to Chloroflexi, and fungal groups from Basidiomycota to Ascomycota. (2) The bacterial alpha diversity, beta diversity as well as the total diversity did not decrease after forest conversion. However, beta diversity of fungal community reduced resulting a net loss of total OTU richness. (3) There was no difference in soil functional compositions and diversity between rubber plantations and rainforest, however, the relative gene abundance of most COG functions, KEGG functions, CAZy functions as well as Antibiotic gene were significantly different between rubber plantation and tropical rainforest. (4) Soil pH and environmental heterogeneity were the main driver for microbial taxonomic composition and gene functional composition. Land use did not result in changes of functional gene composition, but the relative abundance of functional gene. The changed relative abundance gene would alter the ecosystem processes. In conclusion, our results confirmed that land use changes alter the soil microbial community structure and can have profound effects on ecosystem functions and processes.