Farmlands contamination with heavy metals (HMs) can be considered as a global issue especially in developing countries. The current study investigates the various pollution indices, potential ecological risk index (PERI) and human health risk caused by HMs in some selected regions of Punjab Province, Pakistan. Farmlands soil samples were collected, acid extracted and analyzed via ICP-MS (Agilent 7500c) for selected HMs. All the HMs were found within permissible limits set by worldwide regulatory authorities except Cd which exceeded its limit in 68% agricultural soils of the study area. The CF values for Cd showed high (CF≥6) degree of contamination to considerable contamination (3≤CF≤6). The CD values indicated low (CD≤6) contamination to moderate (6dermal>inhalation. Furthermore, the RI values were observed higher than 1.0×10–4 for Cd (Lahore and Faisalabad regions) and Cr (Multan and Faisalabad regions) in children working in farmlands and likely exposed to high cancer risk. So, minimization of pollutants must be the top priority of the state to reduce contaminants inputs and immobilization in soil through environmental protection laws and regulations
Planting trees is one of the most effective activities in recovering soil organic carbon (SOC) stocks of degraded areas, but we still lack information on how different tree species can influence soil respiration, one of the main sources of dioxide carbon (CO2) to the atmosphere. This study aimed to explore the influence of different forest species on the autotrophic and heterotrophic components of the total soil respiration in a bauxite mining area under reclamation. We analysed the soil CO2 efflux under five treatments: i) monoculture of clonal Eucalyptus; ii) monoculture of Anadenanthera peregrina (L.); iii) a mixed plantation of 16 native forest species (Nat); iv) a mined area without vegetation cover; and v) a natural forest cover. This design allowed exploring the soil CO2 dynamics in a gradient of recovery, from a degraded area to natural vegetation. Additionally, we measured soil temperature, moisture and soil characteristics. Soil CO2 efflux increased with increasing forest species cover in the rainy months. There was no significant change in CO2 efflux among the tree species. Heterotrophic soil respiration contributed to 64% of total soil CO2 efflux and was associated with litter decomposition. Amongst the abiotic variables, increases in soil moisture had the most influence on CO2 efflux. Therefore, these results help to understand the factors that underpin the loss of SOC and can orient management practices to improve soil organic matter and restore soil quality in degraded areas.
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.
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.
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.
Forward and reverse successions of karst rocky desertification (KRD) occur simultaneously, and are linked to human activity, thus presenting a mutual feedback loop. Previous studies have focused on the unilateral human-driven mechanism of KRD or the impact of KRD on social-economic activities. These lack quantitative measurement and in-depth understanding of interactions involved. Therefore, this study builds and applies a novel model for measuring the coupling relationship and degree between KRD and social-economic activity in the Guizhou karst region of China. Results show an overall improvement but local deteriorations in KRD from 2000 to 2011; conversely, social-economic activity intensities increased during that time period. With their spatio-temporal variations, positive and negative human–desertification coupling relationships with an increased coupling degree are found. Different coupling relationship types between KRD and social-economic development, including urbanization, economic development and household income, are shown. KRD is found to be high positively coupled with specific human behavior intensities such as population movement, steep slope cultivation and ecological restoration. An inverted U-shaped curve is observed in the coupling index of KRD and urbanization within different development levels. Negative coupling at a low urbanization level indicates the limitation of the karst physical environment on social-economic development. Positive coupling with increasing urbanization implies a conflict between environment protection and social-economic development. A return to negative coupling in several counties with high urbanization levels indicates a win-win for ecology and economy. The effectiveness of the proposed coupling model is demonstrated, informing differentiated strategies for combating KRD and improving social-economic development.
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%.
Long-term application of high nitrogen and phosphorus fertilizer and mono-tillage practices can adversely affect soil health, carbon sequestration and crop growth. A 10-year field experiment was conducted in a wheat-maize cropping system on the Loess Plateau in China to explore fertilization and tillage methods that improve SOC sequestration and crop yields. We evaluated the effects of (1) fertilization (balanced fertilization (BF), low fertilization (LF), and conventional fertilization (CF)) and (2) alternating years of different tillage (no-tillage and subsoiling (NS), subsoiling and ploughing (SP), ploughing and no-tillage (PN)) or continuous ploughing tillage (PP) on input-C, SOC pool, and crop yields. BF and rotational tillage (NS, SP, and PN) increased the amount and stabilization rate of input-C, thereby increased SOC storage, and the highest effect was found in BF+NS treatment. Simultaneously, BF produced higher contents of SOC, readily oxidizable carbon (ROC), particulate organic carbon (POC) and dissolved organic carbon (DOC) and C pool management index (CMI) at 0-10 cm depth. For tillage, rotational tillage increased labile C contents and CMI at 0-10 cm, 20-35 cm and 35-50 cm depths, which improved soil quality. Crop yields showed an increase tendency with the increases of SOC content, labile C fraction contents, and CMI. Therefore, the higher yields of wheat and maize were found in BF and rotational tillage; the highest were in BF+NS treatment. Our finding suggested that NS combined with BF may be the best management to increase SOC storage, improve soil quality and productivity on China’s Loess Plateau.
People’s preferences influence national priorities for economic development and ecological integrity. Often policy makers and development agents base their actions on unclear assumptions about people’s preferences. This paper explores rural citizens’ preferences for economic and ecological development goals and how they differ within and between communities. We collected data from three purposely selected communities representing dominant social-ecological systems in the transboundary Cubango-Okavango River Basin in southern Africa. We used contingent ranking survey experiments, which are a novel methodological advance in policy related research. This included a qualitative experimental design process that provided a broad framing underpinning the research. The contingent ranking itself allowed us to simultaneously assess (i) participants’ ranking priorities for the development goals; and (ii) participants’ preferences for the ordering of those goals. We found relatively strong preference homogeneity within and between communities. Economic development attributes were given high priority across all communities. At the same time, all communities expressed a high preference for a healthy river system providing stable water quality and quantity. This does not mean that our respondents prioritized nature conservation. They showed low preferences for preserving biodiversity and forests which provide less important local benefits than water. This is of high governance relevance. The results point at development domains where policy makers can most likely expect stronger buy-in from citizens. Understanding citizens’ preferences helps to better align national development priorities with what citizens want.
Soil salinity has today become a highly disastrous phenomenon that is responsible for crop failure worldwide and specially in countries with low farmer incomes and food insecurity. Soil salinity is often caused due to water accumulation in fields due to unscientific flood irrigation wherein plants intake the water leaving salts behind. It is, however, the sub-surface soil salinity that affects the plant growth. These salts in sub-surface soil get trapped in root nodules of plants and prevent further water intake. There have been very few studies conducted for sub-surface soil salinity estimation. Hence this study aims to estimate sub-surface soil salinity (at 60 cm depth) for early stage of wheat crop growth in a simplified manner using freely available satellite data, which is a novel feature and prime objective in this study. The study utilizes Sentinel-1 SAR (Synthetic Aperture RADAR) data for backscatter coefficient generation, Sentinel-2 multispectral data for NDSI (Normalised Differential Salinity Index) generation and on ground equipment for direct collection of soil electrical conductivity. The data were collected for two dates in November and December 2019 and one date for January 2020 during the early stage of wheat crop growth. The dates were selected keeping in mind the satellite pass over the study area of Rupnagar on the same day. Ordinary Least Squares regression was used for modelling which gave R2-statistics of 0.99 and 0.958 in training and testing phase and root mean square error of 1.92 in modelling for soil salinity estimation.
As an important soil carbon pool in Qinghai-Tibet Plateau (QTP), alpine peatland are extremely sensitive to global change. Duration of drainage and water table drawdown accelerate peatland degradation due to the soil changed from anaerobic condition to aerobic condition, which may even worsen under climate warming. Hence, the objective of our research was to evaluate the effect of drainage on microbial characteristics, greenhouse gas (GHG) emissions and their influencing factors, and further analyze whether the the variability of GHG emissions increases with warming. The results showed that the influence of water table drawdown on microbial communities were greater than that of duration of drainage. Both the fungal and prokaryotic community compositions varied with water table gradient, and soil microbiota may served as a biomarker to analyze the differences in GHG emissions among three different water table treatments. Intriguingly, the GHG emission decreased with the increase of drainage age, while water table drawdown decreased the emissions of CO2 and CH4, and increased the emission of N2O. In addition, high temperature increased CO2 by 75% and N2O by 42%, but not significantly decreased the CH4 emission rates. Structural equation modeling showed that microbe was the primary factor affecting GHG emissions from drained peatlands, especially prokaryotes. In all, this study indicate water table has a greater effect on GHG emissions than duration of drainage, and the variability of GHG emissions increases with warming.
The Yangtze River basin is distributed across subtropical monsoon climate regions, and has four seasons, including a hot rainy season. These climatic conditions provide favorable conditions for paddy-upland rotation. This paper summarizes the spatiotemporal changes in soil potassium (K) and K cycles in soil-plant systems, as well as environmental impacts on K changes, and provides information for optimal K management. During the past 30 years, soil available K increased by -7.1% to 103.4%. The increase was lower in Hunan, Guizhou, Zhejiang, and Jiangsu provinces (<10%) and higher in Anhui, Jiangxi, Henan, and Chongqing provinces (>30%), demonstrating that soil K pools were enhanced. Farm manure was gradually replaced by synthetic K sources, such as straw and mineral fertilizers, which contributed to an increase in crop yields and soil available K. The meta-analysis results showed that comprehensive K management strategies increased crop yield and soil available K by 11.0% and 44.3%, respectively, on average. Other factors such as balanced fertilization, recycling of straw, increase in atmospheric deposition, decrease in leaching, runoff, and soil K fixation also greatly influenced soil K changes, leading to improvements in crop yields, soil structure, soil fertility, and nutrient availability. Positive K cycles and appropriate K fertilizer use will facilitate proper K management, including cycling of straw, improving machinery and equipment, and estimating the optimal K fertilizer dose after straw. Future studies should focus on tradeoffs between different forms of K under various environmental conditions and accurate estimates of reductions in mineral-K fertilizer requirements following straw return.
This study’s objective was to develop a method by which smallholder forest plantations can be mapped accurately in Andhra Pradesh, India, using multitemporal visible and near-infrared (VNIR) bands from the Sentinel-2 MultiSpectral Instruments (MSIs). Conversion to agriculture, coupled with secondary dependencies on and scarcity of wood products, has driven the deforestation and degradation of natural forests in Southeast Asia. Concomitantly, forest plantations have been established both within and outside of forests, with the latter (as contiguous blocks) being the focus of this study. Accurately mapping smallholder forest plantations in South and Southeast Asia is difficult using remotely sensed data due to the plantations’ small size (average of 2 hectares), short rotation ages (4-7 years for timber species), and spectral similarities to croplands and natural forests. Cloud-free Harmonized Landsat Sentinel-2 (HLS) S10 data was acquired over six dates, from different seasons, over four years (2015-2018). Available in situ data on forest plantations was supplemented with additional training data resulting in 2,230 high-quality samples aggregated into three land use classes: non-forest, natural forest, and forest plantations. Image classification used random forests on a thirty-band stack consisting of the VNIR bands and NDVI images for all six dates. The median classification accuracy from the 5-fold cross-validation was 94.3%. Our results, predicated on high-quality training data, demonstrate that (mostly smallholder) forest plantations can be separated from natural forests even using only the Sentinel-2 VNIR bands when multitemporal data (across both years and seasons) are used.