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.
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.
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.
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.
Land use surveys show 30.5% of Brazil´s territory is dedicated to production of food, fibers, biofuels and raw materials; however, soil erosion is the main agent of land degradation and productivity decreasing. This paper reports the impacts of the adoption of conservation agriculture (CA) principles in controlling soil loss by water erosion, where Zero Tillage (ZT) and integrated Crop-Livestock-Forest (iCLF) management systems are the central policies. Annual soil loss potential, estimated for a scenery lacking CA practices, intensive conventional tillage and monoculture, is of 3.0 billion tons, with 29.5% of losses in croplands and 61.4% in rangelands. The economic impact of soil erosion based only on nutrient losses is estimated in 15.7 billion US dollars. Efforts to control water erosion, intensify agricultural production and mitigate the emission of greenhouse gases are the goal of a recent national governmental program for detailed soil survey and interpretation for land use - PronaSolos. Practices and technologies based on CA, such as ZT and iCLF, already adopted in 44.4 million hectares, with an economic impact of 2.3 billion US dollars, will be recommended to reach 60 million ha by the year 2025. Other benefits are maintenance of rural roads, reduction of soil and water pollution, increase of water quality and storage capacity of reservoirs. The success of the program and current achievements with CA in Brazil result from determination of farmers and many actors involved in controlling soil erosion; as well as plans and policies to implement practices and technologies based on CA principles.
Soil resources in East Africa are being rapidly depleted by erosion, threatening food-, water- and livelihood security in the region. Here we demonstrate how integration of evidence from natural and social sciences has supported community-led change in land management in an agro-pastoral community in northern Tanzania impacted by soil erosion. Drone survey data and geospatial analysis of erosion extent and risk, supported by communication of ‘process’ and ‘structural’ hydrological connectivity, was integrated with local environmental knowledge within participatory community workshops. Rill density data were compared between cultivated plots that had been converted from pastoral land recently and more established plots where slow-forming terrace boundaries were more established. Slope length and connectivity between plots were key factors in development of rill networks. At the two extremes, recently converted land had a rill density ca 14 times greater than equivalent established slow forming terraces. Direction of cultivation, regardless of plot boundary orientation with contours, also enhanced rill development. Evidence of this critical time window of hillslope-scale rill erosion risk during early phases of slow-forming terrace development successfully underpinned and catalysed a community-led tree planting and grass seed sowing programme to mitigate soil erosion by water. This was grounded in an implicit community understanding of the need for effective governance mechanisms at both community and District levels, to enable community-led actions to be implemented effectively. The study demonstrates the wide-reaching impact of integrated and interdisciplinary ‘upslope-downslope’ thinking to tackle global soil erosion challenges.
The native and invasive species in the Yellow River Delta were examined for their spatiotemporal characteristics and succession pattern. First, the appropriate Sentinel-2 and Landsat-8 images from 2018 were selected according to phenological characteristics. A random forest algorithm was used to verify the image spectral band significance and separability using selected images to determine the native and invasive species. Then, the spatiotemporal variation of habitat structure of native and invasive species is discussed in depth from the perspective of landscape ecology. Finally, the expansion direction and expansion mode of S. alterniflora were further analyzed, and main results were obtained as follows. (1) At the medium-high resolution multi-spectral image level, the accuracy of different vegetation community extractions can be improved by taking into consideration both the vegetation phenology and the spectral features of remote sensing images. (2) Sentinel-2 images with red edge bands have obvious advantages in vegetation community extraction as compared to Landsat-8 images (Sentinel-2, OA=82.86%, Kappa coefficient=0.79; Landsat-8, OA=78.77%, Kappa coefficient=0.74). (3) The expansion pattern of the S. alterniflora community became spatially continuous, more regularized and aggregated overtime. (4) The expansion in the north shore mainly faces to the sea, and the south bank mainly faces to the land, and this phenomena is closely related to the sedimentation of the Yellow River Delta. Marginal and external expansion both occurred, but marginal expansion predominated. The results from this study have important theoretical and scientific value for the environmental protection and sustainable development of the entire Yellow River Delta.
How soil quality and microbial communities change in conjunction with stand age in plantations is poorly understood. Here, we evaluated soil quality by using an integrated soil quality index (SQI) and traced the paralleled shifts in fungal community composition by high-throughput sequencing in a chronosequence of Chinese fir (Cunninghamia lanceolata) plantations (stand age of 3, 16, 25, 32, >80 years). Soil properties showed pronounced changes with stand age in the top 0-5 cm. The most prominent increase from 3 to >80-year-old stand was for soil organic carbon (SOC, by 2.1-times), total nitrogen (TN, 1.9-times) and available phosphorus (AP, 2.2-times). SQI increased logarithmically with stand age, with sharper change seen in the 0-5 cm layer than in the 5-15 cm layer. Mycorrhizal fungi increased in abundance initially in younger stands, but then they were gradually replaced by saprotrophic fungi in older stands due to the increase in litter input, which sustains saprotrophs. The positive correlation between saprotrophic fungi and the key soil quality indicators, such as TN, AP and NH4+, showed that higher soil quality was tightly linked with the enrichment of decomposers. Mycorrhizal taxa, such as orders Sebacinales, Thelephorales and Russulales, were positively correlated with acid phosphatase mobilizing P from organic matter. This suggests that the establishment of mycorrhizal fungi sustains tree productivity in younger stands under low soil quality. We conclude that the increase in soil quality throughout the development of Chinese fir plantations is closely linked with the observed transition of fungal communities from mycorrhizae to saprotrophs.
Conservation agriculture (CA) systems represent a set of three soil management principles that include minimal soil disturbance, permanent soil cover and crop rotations whereas the CA-based systems in this study add the bed and furrow tillage structures as integral elements of CA. This study aimed at investigating the long-term (2005-2013) influence of CA-based systems on soil health and crop productivity in northern Ethiopia. The treatments include two types of CA-based systems (permanent raised bed PRB and contour furrowing CF) and conventional tillage (CT). The experimental layout was arranged in a randomized complete block design. Soil samples were collected at 0-10 cm soil depth to assess soil health. Wheat root samples were used to measure arbuscular mycorrhizal fungi (AMF) colonization percentage using grid line intersect method. Piecewise structural equation modeling (PSEM) was used to understand linkages between management practices, soil health and crop productivity. Higher soil microbial biomass carbon (SMBC), AMF spore abundance and root colonization were recorded in PRB followed by CF as compared to CT (P < 0.05). Carbon sequestration rate, nutrient availability, plant available water capacity and air capacity were significantly higher in PRB and CF compared to CT. Outputs of the PSEM highlighted two pathways in which CA-based systems contributed to improved productivity: (1) via higher density of bacteria and improved hydraulic conductivity, and (2) via higher density of fungi and increase soil organic carbon content in the topsoil. The study concludes that CA-based systems have the potential to improve crop productivity through improved soil health.
Knowing which restoration approach provides the best returns on investment for accumulating carbon is essential to foster restoration planning, financing, and implementation. We assessed the recovery of carbon stocks, implementation and land opportunity costs of forests established by natural regeneration and high-diversity native tree plantations. Our study was based on chronosequences (10-60 yr) of 12 naturally regenerating forests, 13 restoration plantations, and 5 reference forests located in Brazil’s Atlantic Forest. Restoration plantations accumulated approximately 50% more above-ground carbon than regenerating forests throughout the chronosequence. When controlling for soil clay content, soil carbon stocks were higher in reference than in restored forests, but they were comparable between plantations and regenerating forests. After 60 years of stand development, recovery of total carbon stocks in both restoration management types reached only half of the average stocks of reference forests. Total cost-effectiveness for carbon accumulation, including both implementation and land opportunity costs, was on average 60% higher for regenerating forests than for plantations (15.1 kgC.US$-1 and 9.4 kgC.US$-1, respectively). Both restoration management types had cost-effectiveness for carbon accumulation markedly lower than the price of carbon credits considered, so some voluntary forest carbon markets are not adequately priced to support restoration derived offsets. Although tree plantations initially had higher rates of carbon storage than regenerating forests, their higher implementation and land opportunity costs make them less cost-effective for carbon farming. Our results further suggest that carbon markets alone have a limited potential to up-scale restoration efforts in Brazil’s Atlantic Forest.
Nitrogen (N) and phosphorus (P) additions to grasslands increase aboveground plant biomass and modify plant community composition, thereby affect plant-derived organic carbon inputting to soil and soil C cycling and storage. However, the effects of nutrient additions on SOC decomposition and soil C sequestration have no census and their underlying mechanisms are poorly understood. This study aimed to explore the mechanisms underlying SOC decomposition and SOC content decline in the topsoil of Tibetan alpine meadows after nine-year field N and P additions. Soil and microbial stoichiometric characteristics were measured and priming effects (PEs), substrate decomposition, as well as microbial C use efficiency (CUE) by adding 13C labeled substrate (glucose or vanillin) were analyzed. N and P additions differentially affected the magnitude and direction of PEs and SOC decomposition, accelerated substrate mineralization of glucose by 33-45% and that of vanillin by 11-45%, but decreased microbial CUE of glucose by 9-15% and that of vanillin by 11-48%. This was associated with the N and P additions-induced lower soil ecological stoichiometric ratios and higher microbial C:N:P ratios compared with Control. Therefore, these comprehensive effects of N and P additions on decomposition of SOC and plant-derived C substrates reduced SOC sequestration and thus SOC content. Long-term N and P additions would weaken soil functioning as C pool of Tibetan alpine meadows.
Soil pH is strongly associated with soil biogeochemical cycles and biodiversity in terrestrial ecosystems. GE has been widely adopted as an effective practice to restore degraded grasslands. However, the effect of GE on soil pH is still poorly understood and remains inconclusive. We synthesized data from 63 sites in the literature and 43 additional field sites and investigated the dynamics of soil pH following GE across China’s grasslands. Mean pH decreased 0.13 units with GE (mean pH was 8.15 and 8.02 for grazed and GE groups, respectively, p < 0.001). The pH of surface soil (0–20 cm) showed greatest decrease rates in GE grasslands, whereas that of deep soil (20–100 cm) had limited responses to GE. In general, the largest decrease in the rates of soil pH occurred after medium-term periods (5–15 years) of GE, whereas a smaller rate of change was found over short- (≤5 years) and long-term periods (≥15 years) of GE. Of the factors examined, the rate of soil pH change was negatively correlated to MAP, but had no significant relationship with MAT. The rate of soil pH change decreased linearly with RCC, RNC, RAC and RBC. Sedge-dominated grassland had higher pH decrease rates at 0–10 cm soil depth than grass-dominated grassland, whereas grassland dominated by forbs and shrub species showed the highest decrease in pH at 20–30 cm. Our results indicate that GE causes significant soil acidification, especially in surface soil and humid areas, which provides an important reference for future management of China’s grasslands.