The Changes of Spatiotemporal Pattern of Rocky Desertification and Its Dominant Driving Factors in Typical Karst Mountainous Areas under the Background of Global Change

Tracking flowpaths in a complex karst system through tracer test and hydrogeochemical monitoring: Implications for groundwater protection (Gran Sasso, Italy)

Groundwater in karst aquifers is frequently tapped for drinking purposes, due to frequent huge volumes of resources. Unfortunately, vulnerability of these aquifers can be high, due to possible fast transfer of recharge water on springs by the karst network. On Gran Sasso Mountain regional aquifer, several springs are subjected to drinking withdrawal and an updated evaluation of their potential is now a fundamental issue to be considered, facing climate change effects, which reflect on variation of discharge regimen and values. To distinguish between different contribution of spring recharge, a tracer test has been carried out on the Vitella d'Oro spring, fed both by the regional aquifer and by a local system exposed to karst features developed in the Rigopiano Conglomerates formation. Thanks to hydrogeological, hydrogeochemical and isotopic data, a conceptual model of spring recharge has been proposed and subsequently validated by the tracer test results. All information confirms the superimposition on the regional base flow, by a relevant contribution of the karst network, influencing the spring discharge in recharge periods. In detail, a fast flow component is responsible for discharge peaks and frequently of turbidity events, having a mean velocity ranging from 30 to 70 m/h in the aquifer. Besides of this fast flow, an additional aliquot of the recharge is due to the same local aquifer, but slower flow clearly identifiable by hydrochemistry and isotopic data. Thanks to these findings, a renewed management of the spring has been suggested, considering the different degrees of aquifer vulnerability (turbidity occurrence) directly related to the discharge regimen.

Evaluation of niche, diversity, and risks of microplastics in farmland soils of different rocky desertification areas

The occurrence, sources, effects, and risks of microplastics (MPs) in farmland soils have attracted considerable attention. However, the pollution and ecological characteristics of MPs in farmland soils at different levels of rocky desertification remain unclear. We collected and analyzed farmland soil samples from rocky desertification areas in Guizhou, China, ranging from no to heavy risks. We explored differences and migration of MPs across these areas, unveiled the relationship between diversity, niche, and risks of MPs, and determined influencing factors. The average abundance of soil MPs was 8721 ± 3938 item/kg, and the abundance and contamination factor (CF) of MPs escalated with the increase in rocky desertification level. Diversity, niche, and risk of soil MPs in different rocky desertification areas were significantly different. Rocky desertification caused both MP community differences and linked MP communities at different sites. Diversity and niche significantly affected MP risk (p < 0.05). Environmental factors with significant correlations (p < 0.05) with the abundance and ecological characteristics of MPs varied significantly in soils of different rocky desertification areas. This study advances our comprehension of MP pollution in farmland soils within rocky desertification areas, offering essential data and theoretical insights for the development of control strategies.

Monitoring the evolution process of karst desertification and quantifying its drivers in the karst area of Southwest China

Karst desertification (KD) is a unique desert ecological phenomenon occurring in the karst region of Southwest China (KRSC). Studying the KD evolution process and distinguishing the influences of human activities and climate factors on KD are essential for restoring KD areas. This article is based on MODIS remote sensing data and ERA5-Land data. Additionally, multiple linear regression models, correlation analysis, and residual analysis are utilized to analyze the spatiotemporal evolution characteristics of KD in the southwest region of China from 2000 to 2020. This study aims to differentiate the impacts of human activities and climate change on the desertification process in karst areas. (1) In the southwest region of China, the overall KD shows an intensifying trend at both ends of the study area and an ameliorating distribution pattern in the central region. In particular, Guizhou province, which is located in the center of the study area, demonstrated significant suppression in the KD process from 2000 to 2020. (2) In the southwest karst region, there are significant spatial differences in the correlation between the KD process and precipitation, temperature, and radiation. Temperature is significantly negatively correlated in most parts of Yunnan. (3) According to the residual analysis, approximately 89.62% of the karst areas in the southwest are influenced by climate, while 10.38% are influenced by human activities. Climate change has a relatively small impact on the ability to improve KD compared to the disruptive influence of human activities. Some human activities, such as afforestation, in which grassland and cultivated land are converted to forest, play a substantial role in inhibiting the KD process. Conversely, the rapid expansion of urban areas tends to exacerbate KD in adjacent regions. Therefore, this study of the evolution process of KD in Southwest China can provide a scientific basis for monitoring and controlling KD and provide theoretical support for coping with the challenges posed by KD to China's ecological environment.

The Response of Rocky Desertification to the Development of Road Networks in Karst Ecologically Fragile Areas

Frequent cross-regional communication makes road networks increasingly dense and has generated prominent human interference, thus resulting in the destruction of the landscape's integrity and leading to changes in the functional processes of the habitat. In order to discuss the impacts of intense human activity brought by the road networks on the rocky desertification landscape and habitat quality in karst ecologically fragile areas, taking the road networks as the humans activity intensity factor, a quantitative analysis was conducted to analyze the impacts of road networks on the spatial evolution of the rocky desertification landscape and changes in regional habitat quality characteristics under different development modes in the study area based on a landscape pattern gradient method, spatial analysis, and INVEST model. The results showed that: (1) in the study area, due to the destruction of landscape integrity caused by the development of the road networks over the past 17 years, the landscape pattern of rocky desertification tended to be fragmented and complex, first showing an inclination for rapid fragmentation and then gradual recovery later. (2) The land-use intensity and degree of rocky desertification in the industrial areas and in the tourist areas of the study area have increased to varying degrees over the past 17 years, as is seen mainly via the expansion of construction land, cultivated land enclaves in the urban expansion areas, and new development areas. (3) Unders different regional models, the fragmentation of the rocky desertification landscape in the industrial areas was higher than that in the tourist areas, resulting in a significantly lower habitat quality and obvious degrees of degradation. The research findings provide the basis for further deepening our understanding how human activity intensity affects the evolution of the regional landscape, including the development of rocky desertification, the supply of services, and supporting habitat conservation in karst ecologically fragile areas.

Quantitative assessment of the relative contributions of climate change and human activities to NPP changes in the Southwest Karst area of China

Net primary production (NPP) is an essential component of the terrestrial carbon cycle and an essential factor of ecological processes. In global change research, it was the core content to study the driving forces of NPP change. In this paper, we focused on the Southwest Karst area of China and analyzed the response mechanisms of NPP to topography, land-use types, climatic change, and human activities. Our results showed that (1) changes in elevation and slope lead to significant differences in the spatial distribution of NPP. With the increase of elevation and slope, NPP first increased and then decreased, their critical values were 2000 m and 15°, respectively. (2) NPP varied significantly among different land-use types. The average NPP of the forest was the highest, and the average NPP of cultivated land increased fastest. (3) Temperature and precipitation had the most substantial influence on NPP, both of them promoted the increase of NPP, and the effect of temperature was more obvious in the Southwest Karst area. (4) Ecological engineering significantly promoted the change of NPP, while animal husbandry significantly inhibited the change of NPP. (5) There were significant spatial differences in the driving effects and corresponding contributions of climatic change and human activities; both of them promoted the increase of NPP in the Southwest Karst area of China. Under climatic change and human activities, NPP increased by 1.24 gC·m^-2·year^-1 and 2.29 gC·m^-2·year^-1, respectively. The contributions rates of climatic change and human activities separately accounted for 35% and 65%. The contribution of human activities on NPP was much higher than that of climatic change in the Southwest Karst area, and the results suggested that we should focus on the role of human activities on NPP change.

Spatiotemporal dynamics of soil loss and sediment export in Upper Bilate River Catchment (UBRC), Central Rift Valley of Ethiopia

Soil loss is one of the major challenges for agricultural production in the Ethiopian highlands. The rate and distribution of soil loss (SL) and sediment export (SE) are essential to map degradation “hotspot” areas for prioritizing soil and water conservation measures. The objective of this study was to estimate the dynamics of SL and SE in the Upper Bilate River Catchment of Central Ethiopia. The Sediment Delivery Ratio (SDR) module of the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model was used to estimate and map SL and SE. The primary input data were rainfall, soil data, land use, and other biophysical parameters of the study area. The model output confirmed that the average total soil loss of the catchment was 36.8 million ton/yr. It is modeled that soil loss doubles within 30 years. The average annual sediment export was about 3.62 ton/ha/yr. The mean annual soil loss of the study area was 23 ton/ha/yr, which exceeded the soil loss tolerance (SLT), estimated to range between (2–18 ton/ha/yr) in Ethiopia. Based on the soil erosion risk level, about 22% of the catchment area was classified as severely degraded, while 62 % was moderately degraded. Severe soil erosion prevails in the sub-watershed (SW)-5, SW-4, and SW-13. Therefore, these sub-watersheds need priority conservation action to restore the ecosystem processes of the study area.