Ecological responses of vegetation and environmental factors to the reversal of sandy desertification and soil-vegetation relationships

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Influence of grazing and solar panel installation on tenebrionid beetles (Coleoptera Tenebrionidae) of a central Asian steppe

Grazing may represent a major threat to biodiversity in arid grasslands. The increasing use of grasslands for solar parks may represent a new important threat. No study has investigated the effects of solar parks on soil insects. Tenebrionids are a major component of the arthropod fauna of grasslands of central Asia. These ecosystems are threatened by grazing and increasing land use for solar parks. Aim of this work was to investigate the effects of grazing and solar panels on tenebrionids in arid grasslands (desert steppe) in China by comparing their community structure in ungrazed, heavily grazed, and solar park sites. Beetles were sampled by pitfall traps, and sites were compared for abundance and diversity (Hill numbers). All sites were characterized by simple, strongly dominated tenebrionid communities. Species proportions varied among sites. Grazing negatively influenced overall abundance, but did not alter species proportions; by contrast, solar panels had no effect on the average abundance, but reduced the proportion of the most abundant species. Compared with the other two sites, the solar park was characterized by a higher plant biomass and lower temperatures. A major availability of resources and less harsh conditions in the solar park might have a role in reducing the dominance of the most abundant species, allowing other species to attain higher abundances. This led to a more balanced community structure, with higher values of diversity. Although neither grazing nor solar panel installation modified radically tenebrionid species-abundance distribution or diversity, grazing and solar panel installation had different effects in species abundances and their impact might amplify the effect of other disturbance factors such as the ongoing climate change.This research was supported by a grant of China Postdoctoral Science Foundation (2018M643770) to NT. SF benefitted from the following grants: Fondo per il finanziamento delle attivita base di ricerca 2017 (FFABR 2017, by the Ministry of Education, University and Research, Italy) with the project "Ecologia e Biogeografia di Coleotteri Tenebrionidi nella Regione Paleartica", and FFO 2022 (by Department of Life, Health and Environmental Sciences, University of L'Aquila) for the project "Struttura di comunita biotiche in ambienti di bassa ed alta quota soggetti a fattori di elevato stress termico e idrico".info:eu-repo/semantics/publishedVersio

CHARACTERISTICS OF TEMPORAL AND SPATIAL VARIATION OF NDVI IN BEIJING AND THE RELATIONSHIP WITH URBAN HEAT ISLAND EFFECT

Vegetation is an important part of ecosystems, and the use of vegetation coverage as an indicator to study the spatio-temporal dynamics of regional vegetation is necessary for ecosystem health evaluation. The urban heat island effect can change the structure and functions of urban ecosystems, and affect the climate, hydrology, atmospheric environment, and energy metabolism of cities, as well as the health of residents. Using Beijing as a case study, this research generates vegetation coverage maps using remote sensing imagery from 1998, 2003, 2008, 2013 and 2018. This study indirectly analyzes the urban heat island effect through spatio-temporal changes in vegetation cover. These analyses offer three key findings. First, vegetation coverage in Beijing from 1998 to 2018 experienced an oscillating upward trend, indicating that the urban heat island effect was weakening. Second, the vegetation coverage in Beijing exhibited a concentric structure, which increased from the central area to the surrounding area, indicating that the urban heat island effect gradually weakens from the inside to the outside of the city. Third, from 1998 to 2008, the normalized difference vegetation index (NDVI) of the areas outside the Sixth Ring Road and inside the Third Ring Road was increasing, therefore the urban heat island effect in these areas was weakening. Conversely, NDVI was decreasing between Sixth Ring Road and Third Ring Road; these areas experienced an increase in the urban heat island effect

Deserts and Desertification

A desert is an ecosystem in an arid zone in which sand dunes cover the land and sandstorms often occur. Although desert vegetation is sparse, it plays an important role in ecosystem structure and function. Desertification is one of the most severe environmental problems today. Land desertification can be controlled through many measures, such as eco-villages, eco-agriculture, biodiversity conservation, and the combination of engineering and biology. This edited volume provides new insights into the pattern of desert ecosystems and the progress of desertification control. It is a useful resource for researchers in ecology, forestry, and land desertification control

Spatiotemporal Response of Vegetation to Rainfall and Air Temperature Fluctuations in the Sahel: Case Study in the Forest Reserve of Fina, Mali

Forests constitute a key component of the Earth system but the sustainability of the forest reserves in the semi-arid zone is a real concern since its vegetation is very sensitive to the climate fluctuation. The understanding of the mechanisms for the vegetation–climate interaction is poorly studied in the context of African Sahel. In this study, the characteristics of the vegetation response to the fluctuations of precipitation and temperature is determined for the forest reserve of Fina. Rainfall estimates, air temperature and NDVI were re-gridded to a same spatial resolution and standardized with respect to their respective long-term mean. Lag-correlations analysis was used to estimate lag times between changes of climate variables and vegetation response at both seasonal and interannual bases. Results show increasing tendency of NDVI started from the 1990s coinciding the recovery of the rainfall from the 1980s drought, and the obtained correlation (r = 0.66) is statistically significant (p value < 0.01). The strongest responses of vegetation to rainfall and temperature fluctuations were found after 30 and 15 days, respectively. Moreover, at a shorter time lag (e.g., 15 days), more pronounced vegetation responses to both rainfall and temperature were found in agriculturally dominated land while at a longer time lag (e.g., 30 days), a stronger response was observed in Bare-dominated land. The vegetation response to the climate fluctuation is modulated by the land-use/cover dynamics

Situating China in the Global Effort to Combat Desertification

International efforts to tackle desertification led by the United Nations Convention to Combat Desertification (UNCCD) support participatory approaches. The emphasis has been on dialogue between different perspectives, which are often grounded in individualism rather than prioritizing society as a whole, and as a result progress in implementation has been slow. China has made substantial progress in tackling desertification, but its approaches have been controversial, and the sustainability of its achievements has been questioned. While China has been active in UNCCD processes, its approach to addressing desertification has differed from those of other countries. China can thus offer important insights into the international campaign, while acknowledging that China can also learn from the efforts of others. We compare the UNCCD’s “bottom-up” approach and China’s “top-down” approach to better understand the challenges of tackling desertification. We examine the evolution in how desertification has been addressed and shed light on the context behind the changes, focusing on the role of science, policies, and public participation. We find a convergence between top-down and bottom-up approaches and that similar challenges have been experienced. Constant communications with outsiders have enabled adjustments and changes in both China and the international community, even though their approaches remain distinct. We conclude that both approaches are moving toward solutions that start from proactive investments of governments in financial, legal, institutional, and organizational aspects, draw on scientific insights, and which are grounded in the motivated and voluntary participation of non-state actors. Improved sharing of lessons across these approaches would help to create a better enabling form of environmental governance that contributes to tackling desertification

Evolution of Ecological Security in the Tableland Region of the Chinese Loess Plateau Using a Remote-Sensing-Based Index

Maintaining optimal ecological security is a serious issue in the Chinese Loess Plateau (CLP). Remote sensing ecological indexes (RSEI) of three main tableland regions of the CLP were calculated based on spectral information provided by remote sensing imaging satellites between 2000 and 2018. We were able to use RSEI values to systematically evaluate the temporal and spatial variation in the regional ecological environment and determine the influential factors that mainly associated with these changes. The results showed that between 2000 and 2018, the ecological environment improved, remained stable, and deteriorated, respectively, in the Gansu, Shaanxi, and Shanxi tablelands. Regions with poor or fair RSEIs were concentrated around the main river basins, while regions with moderate RSEIs were associated with poor ecological conditions and poor areas. The significant spatiotemporal variation in RSEI indicates that the ecological system in this region is relatively fragile. We also observed that natural factors such as the temperature, potential evapotranspiration, and precipitation had the greatest influence on the overall ecological quality. The rapid increase in the regional population and human activity played an important role in the variation in the regional RSEI. This research will provide important information on controlling regional soil erosion and ecological restoration in the CLP

Chinese cropping systems are a net source of greenhouse gases despite soil carbon sequestration

This work was funded by National Basic Research Program of China (2014CB953800), Young Talents Projects of the Institute of Urban Environment, Chinese Academy of Sciences (IUEMS201402), National Natural Science Foundation of China (41471190, 41301237, 71704171), China Postdoctoral Science Foundation (2014T70144) and Discovery Early Career Researcher Award of the Australian Research Council (DE170100423). The work contributes to the UK-China Virtual Joint Centres on Nitrogen “N-Circle” and “CINAg” funded by the Newton Fund via UK BBSRC/NERC (grants BB/N013484/1 and BB/N013468/1, respectively).Peer reviewedPostprintPostprin

Dust emission from croplands in the Free State, South Africa

The global dust load showed a large increase during the last century due to climate change and the expansion of vulnerable land, both of which are caused by human modifications. The increase in vulnerable land, both in size as in intensity, is mainly attributed to the increase in agricultural areas and agricultural intensification. Dust emission has both an onsite effect due to the degradation of the emitting area, and an offsite effect on human health and climate. The degradation of land is especially relevant for agricultural areas where crop yield can strongly diminish due to the depletion of clay, silt, and nutrients from soils. The semi-arid Free State province has been identified as the largest emitter of dust in South Africa, which is caused by the large-scale agriculture, climate, and soil type. Dust storms have the potential to reach the densely populated Gauteng province causing negative consequences on human health and well-being. Dust events in the Free State show a strong seasonality that is attributed to the agricultural practices that leave soils bare and vulnerable to erosion after harvesting. However, the large differences in dust events per year indicate that additional surface characteristics control the emissions from these harvested croplands. One of the primary potential controls that farmers have on the emissivity of the land is the management of soil crusts, but, the role of soil crusts on sandy soils is often not considered. Therefore, this thesis will address the possible role of soil crusts on the dust emission from the Free State croplands. This thesis examines the formation of crusts by rainfall, the dust emissions from cropland soils, and the surface characteristics that control this erosion. The main instrument used to measure the erodibility of a surface is the Portable In-Situ Wind Erosion Laboratory (PI-SWERL). The comparability of this portable instrument was assessed by a cross-comparison with a traditional straight-line wind tunnel. The threshold friction velocity of sandy surfaces was similar for the two instruments, whereas the threshold friction velocity of loamy sand indicated that the PI-SWERL is a more precise instrument that is capable of detecting the initial, small PM10 emissions from a surface. To determine the potential for crusts to form on the sandy cropland soils, rainfall experiments combined with shear strength measurements were performed on Free State soils. The results showed that significant crusts develop within 15 mm of rainfall, and shear strengths similar to those measured in the laboratory were observed in the field. PI-SWERL measurements showed that these experimental crusts can limit the PM10 emission flux from 10.53 and 3.87 mg m-2 s-1 Luvisol and Arenosol soils, respectively, to below 0.03 mg m-2 s-1 for both. The addition of abraders increased the emission from a crust to 0.43 and 0.31 mg m-2 s-1 for Luvisol and Arenosol, respectively. The strong effect of crusts on emissions have been compared to field measurements, which showed a similar potential to minimize dust emissions, but also are complex interaction on the surface that defines this influence. The average emission of crusted surfaces was 0.476 mg m-2 s-1 (standard II deviation = 0.348, min = 0.004, max = 1.401 mg m-2 s-1) at a friction velocity of 0.59 m s-1, whereby the presence of abraders showed a power relationship to the emission from these surfaces. The emission from loose surfaces ranged between 1.646 mg m-2 s-1 (standard deviation 0.980, min = 0.291, max = 5.974 mg m-2 s-1), with a linear relationship between the emission and the clay and silt content. The initial sensitivity of an agricultural field to wind erosion needs to be considered when assessing the surface conditions under which crusts could play a minimizing role in the emission of dust. This is controlled by the soil cover, such as vegetation or degrading crop straw and stubble that is left after harvesting. Four fields, with a range of soil cover and crust characteristics, have been measured in the field. The soil cover has been quantified using Unmanned Aerial Vehicle (UAV) image analyses. The erodibility of the soils was characterised by the horizontal sediment flux and the saltation threshold. The soil cover differed from 11% for a harvested groundnut to 66% for a harvested maize field, the latter being the most common crop type in the Free State. This data shows the high initial importance of soil cover on the wind erosion from a field, whereby the sediment flux from the maize field was 11 and 187 times lower than that of fallow and groundnut fields. Considering the relatively high sediment flux from the fallow and low soil cover fields, crust and abrasion management should be considered on such surfaces. Some surfaces showed a depletion of clay and silt, which is evidence of land degradation caused by dust emission. This depletion could eventually lead to a lower yield and the need for more fertilizers. Furthermore, an enrichment in certain allergens and pathogens has been found in the suspended dust from Free State croplands. This shows the relevance of minimizing dust, both for the emitting region and the offsite areas that dust eventually reaches. Future studies should investigate the relationship between the sediment flux and the PM10 flux since this relationship is not known and could differ per field and soil type. Furthermore, the influence of roughness needs to be assessed because roughness is generally known to decrease the emission from a surface. However, to create roughness, it is required to disturb existing crusts, making it uncertain if such activities could increase or decrease overall emissions. Lastly, the implications raised by this thesis are not only relevant for Free State but can also be considered for other cropland areas with strong seasonality in cover and moisture

Land Degradation Assessment with Earth Observation

This Special Issue (SI) on “Land Degradation Assessment with Earth Observation” comprises 17 original research papers with a focus on land degradation in arid, semiarid and dry-subhumid areas (i.e., desertification) in addition to temperate rangelands, grasslands, woodlands and the humid tropics. The studies cover different spatial, spectral and temporal scales and employ a wealth of different optical and radar sensors. Some studies incorporate time-series analysis techniques that assess the general trend of vegetation or the timing and duration of the reduction in biological productivity caused by land degradation. As anticipated from the latest trend in Earth Observation (EO) literature, some studies utilize the cloud-computing infrastructure of Google Earth Engine to cope with the unprecedented volume of data involved in current methodological approaches. This SI clearly demonstrates the ever-increasing relevance of EO technologies when it comes to assessing and monitoring land degradation. With the recently published IPCC Reports informing us of the severe impacts and risks to terrestrial and freshwater ecosystems and the ecosystem services they provide, the EO scientific community has a clear obligation to increase its efforts to address any remaining gaps—some of which have been identified in this SI—and produce highly accurate and relevant land-degradation assessment and monitoring tools