Ecological efficiencies of rocky desertification control measures at the regional scale remain unclear. It is urgent and challenging to determine the influences of ecological engineering on the ...variations of ecosystem services, and to evaluate the ecological benefit of rocky desertification control measures. In this study, variations of three kinds of ecosystem services (water regulation, soil conservation, and carbon sequestration) were analysed in a typical karst region of Northwest Guangxi China during the period from 2000 to 2010. The relative importance of the main factors that influence these three ecosystem services were analysed using radial basis function network, Kaiser–Meyer–Olkin (KMO), and principal component analysis. The results showed that over half of the study area has experienced an increase in water regulation (50.39%) and soil conservation (58.53%), and approximately 28.24% of the study region has undergone increased carbon sequestration. Environmental factors had a substantial impact on the ecosystem services, and the order of relative importance was as follows: geology > soil > vegetation > temperature > precipitation. Anthropogenic activities have played an important role in the changes to the ecosystem services. In addition to the significant conversion of other land types to woodland (approximately 46.80% of the total transfer area), the vegetation species, shape, and fraction, which are greatly influenced by human activities, contributed 79.05% to the variance. This resulted in a high KMO value of 0.912 (>0.9, represents very suitable), and the Bartlett test was significant (Sig. 0.00). These results showed that although natural environmental factors remained basic influences on the pattern of ecosystem services, anthropogenic activities of ecological engineering projects also had important and positive influences on the ecosystem services. This study also indicated that satellite images and new methods should be applied to deal with the relative lack of existing datasets.
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•The spatiotemporal variations in ecosystem services in a karst region were evaluated.•Relative importance of the influencing factors on ecosystem services was determined.•Ecosystem services have increased because of natural factors and human activities.•Environmental factors have marked effects on the ecosystem services.•Ecological engineering has a positive influence in improving the ecosystem services.
Ecological restoration is widespread in the karst region, southwest China, but the impacts of different restoration strategies on soil fertility indices have rarely been compared. Here soil nutrients ...and microbial communities were measured 16 years after agricultural abandonment in a karst area, southwest China. Three restoration strategies were included, i.e., i) restoration with an economic tree species Toona sinensis (TS), ii) restoration with Guimu-1 hybrid elephant grass (GG), iii) restoration with a combination of Zenia insignis and Guimu-1 hybrid elephant grass (ZG). Cropland under maize-soybean rotation (CR) was used as reference. Soil organic carbon level was more than doubled in TS, and that in GG and ZG was elevated by about 50% relative to CR. Soil total nitrogen concentration in GG was not significantly different from CR, but that in TS and ZG was increased by 93% and 55% relative to CR. Similar to nitrogen, soil total phosphorus concentration in GG was not changed relative to CR, but that in TS and ZG were significantly increased. Microbial biomass carbon and nitrogen concentrations were significantly increased in TS and GG by 124% and 82%, respectively, compared to CR, but those in ZG and CR were similar. The abundance of total PLFAs (phospholipid fatty acids) was significantly increased by 55–69% following agricultural abandonment, and there was no significant difference among the three restoration strategies. The patterns of the other microbial groups and the ratio of fungal to bacterial (F:B) PLFAs were largely similar to that of total PLFAs. Soil organic carbon was identified as the primary factor affecting the abundance of soil microbial communities. Our findings suggest that the three restoration strategies, particularly TS are efficient in improving soil fertility.
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•Effects of three restoration strategies on soil nutrients and PLFAs were compared.•The three restoration strategies were efficient in enhancing soil C pool.•Two restoration strategies were efficient in improving soil TN and TP.•The abundance of soil microbes were increased by the three restoration strategies.
•The rainfall erosivity increased in the karst region of SW China from 1901 to 2020.•There are significant differences in the spatial distribution of annual, seasonal and monthly rainfall ...erosivity.•The trend of increasing rainfall erosivity is more obvious in January in winter.•More variability is found in the monthly scale study.
Global warming changes global and regional patterns of precipitation, which will inevitably lead to more severe soil erosion risks in fragile karst ecosystems. Understanding the variation pattern of rainfall erosivity is vital for preventing and controlling soil erosion in the karst region of southwestern (SW) China. In this study, the spatiotemporal dynamic evolution pattern of the rainfall erosivity throughout the year in the karst region of SW China was explored using regression analysis and the Mann–Kendall test based on the monthly rainfall data for 1901–2020 in the CRU_TS 4.05 dataset. The results indicate that: (1) The rainfall erosivity in the karst region of SW China varies with latitude and is more significant in the south, and its interannual variations are linear and positive. (2) The interannual linear increase in rainfall erosivity was the greatest in the peak forest-plain rocky desertification control zone (FLPY). (3) The rainfall erosivity exhibited an increasing trend in spring, summer, and winter, with the most significant increase in January. (4) More variability was observed on the monthly scale. In summary, future investigations and control of soil erosion in the karst region of SW China under climate change should focus on the critical times when (e.g., January) and areas where (e.g., peak forest-plain rocky desertification control zone) rainfall erosivity changes significantly. Identifying the shift in the rainfall erosivity patterns caused by climate change is critical for assessing soil erosion risks in karst areas and for formulating countermeasures.
Gross nitrogen (N) transformations are crucial in determining soil N status, but how gross N transformations change during post-agricultural succession remains poorly understood. Here, gross N ...transformations were measured using a 15N isotope dilution technique in a subtropical karst region, southwest China. A stratified random sampling scheme was adopted and the succession sequence included grassland (~4 years), shrubland (~15 years) and secondary forest (~30 years) with cropland as reference. The soil was leptosols (limestone soil). Soil total N concentrations were significantly (P < 0.05 hereafter) elevated in the shrubland and forest relative to the cropland and grassland. No clear pattern was found for NH4+ concentration, but NO3− concentration increased from the grassland to the forest. The gross rates of N mineralization and nitrification (GN) were significantly lower in the grassland than in the cropland, but increased significantly during post-agricultural succession. There were no clear patterns for the rates of dissimilatory NO3− reduction to NH4+ and gross NO3− immobilization. Gross NH4+ immobilization (GAI) in the forest was lowest but there was no significant difference among the cropland, grassland and shrubland. Gross N mineralization rate correlated significantly with protease activity, implying that the depolymerization of N-containing polymers was likely the rate-limiting step of gross N mineralization. Net nitrate production rate and GN:GAI ratio increased significantly from the grassland to the forest, supporting that soil N cycling likely became more open during post-agricultural succession in the karst region of southwest China.
•Gross N mineralization and nitrification decrease initially and then increase.•Microbial N retention capacity is low for nitrate.•Protease activities control inorganic N production processes.•Depolymerization is the rate-limiting step of gross N mineralization.
Due to anthropogenic disturbances, the karst region in southern China is vulnerable to ecological problems such as soil erosion and surface exposure. However, limited studies on variations in ...large-scale ecological risk (ER) and their influencing factors, particularly the coupling/decoupling relationship with an exposed surface fraction (ESF), make ER regulations and ecological restoration challenging. The present study evaluates the ER of eight typical karst provinces in Southern China from 1990 to 2020 using the technique for order preference by similarity to an ideal solution (TOPSIS) model and ecosystem services (habitat quality, water yield, carbon storage, soil conservation, and food production), and extracts the contemporaneous ESF using Landsat satellite data in Google Earth Engine (GEE). The spatiotemporal change of ER and ESF are analyzed, and their coupling/decoupling relationship and driving mechanism are explored using coupling coordination degree (CCD) and multi-scale geographically weighted regression (MGWR) models. The results show that: (1) Over the past 30 years, the ER has increased until 2010 and subsequently declined, with an increasing mean value (0.463–0.503), except in Chongqing municipality. The ESF decreased significantly (the mean value dropped from 44.7% to 38.7%), except that in Sichuan province. (2) The average CCD between ER and ESF decreased with fluctuation of −0.017, with a decoupling relationship (58.18%). The coupling area is larger than the decoupling area in the Sichuan area, while other provinces are opposite. (3) The coupling/decoupling relationship in the study area is mainly driven by terrain (elevation, slope) and socio-economic (population density, per capita GDP) factors. More attention should be paid to the role of these factors in the continuous reduction and control of ESF and ER. This study can serve as a reference for similar studies in karst regions, such as risk assessment and surface monitoring, rocky desertification control, ecological engineering layout, and territorial planning.
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•Long-term and large-scale ecological risk (ER) in karst region of China is assessed.•Exposed surface fraction (ESF) reduced with the implementation of Eco-engineering.•In the last 30 years, the relationship of ER and ESF has substantially decoupled.•Terrain and socio-economic factors are the primary determinants of ER-ESF relation.
•Expanding deep learning is developed for prediction of tunnelling-induced settlement.•The effects of karst geology on tunnelling construction are evaluated.•Expanding method is validated by ANN, ...LSTM, GRU and Convd1d models.•Influence of dataset size on predictive performance is analyzed.
This paper presents the measurement and prediction of the tunnelling-induced surface response in karst ground, Guangzhou, China. A predictive method of ground settlement is proposed named as the expanding deep learning method. This method kinetically uses the expanding tunnelling data to predict ground settlement in real time. Four types of deep learning methods are compared, including artificial neural network (ANN), long short-term memory neural networks (LSTM), gated recurrent unit neural networks (GRU), and 1d convolutional neural networks (Conv1d). Based on static Pearson correlation coefficient, a kinetic correlation analysis method is proposed to evaluate the variable significance of input data on the ground settlement. The effect of cemented karst caves and variable geological conditions are then analysed. The results indicate that the expanding Conv1d model precisely predict the tunnelling-induced ground settlement. The kinetic correlation analysis can reflect the variable influence of geological condition and tunnelling operation parameters on the ground settlement.
•Erosivity can be calculated well by a power law equation with cosine relation.•The magnitude of rainfall erosivity varies unevenly among seasons.•Increasing trend of annual and seasonal rainfall ...erosivity was observed.•Erosivity density shown a significant high correlation with rainfall erosivity.•The gravity centre of rainfall erosivity has shifted across the three provinces.
Rainfall erosivity, a measure of the potential for soil erosion by water, is an important factor for estimating soil loss. Understanding the variation tendency of rainfall erosivity is especially critical for soil and water conservation in the fragile ecological environment of the karst region in southern China. This study analysed the rainfall erosivity at multiple spatial and temporal scales based on daily rainfall data observed at 223 meteorological stations during the period of 1960–2017. A daily rainfall erosivity model, co-kring interpolation, regression analysis, gravity model and the Mann-Kendall test were applied in the analysis process. The results indicate the following: (i) The mean annual rainfall erosivity is 5130.00 MJ·mm·ha−1·h−1 in southern China, with a range of 3964.24 to 6425.87 MJ·mm·ha−1·h−1, and varies greatly among different provinces. (ii) The magnitude of rainfall erosivity varies unevenly among seasons, with the mean rainfall erosivity in summer being almost 15 times higher than that in winter. (iii) The annual and seasonal rainfall erosivity has increased in the karst region of southern China over the past 58 years, whereas at the province scale, the seasonal trend in rainfall erosivity is more complex, and the trends are not necessarily linear and positive. Furthermore, at the interdecadal scale, there is no regular trend, and the data exhibit considerable variation. (iv) The temporal variation characteristics of erosivity density are basically consistent with those of rainfall erosivity, and the two show a significant high correlation. (v) The gravity centre of annual rainfall erosivity is located in Tongdao County, while the monthly gravity centre has shifted across Guangxi, Hunan and Guizhou. In summary, knowledge of rainfall erosivity patterns is valuable for assessing the risk of soil erosion and formulating countermeasures.
There is little information regarding the dynamics of fermentation products and the bacterial community in silage prepared with alfalfa (MS), perennial ryegrass (LP), and their mixture in the karst ...region. In this study, we explored the effects of combining MS with LP in different ratios (100% MS, 70% MS + 30% LP, 50% MS + 50% LP, 30% MS + 70% LP and 100% LP; fresh matter basis) on silage chemical composition, fermentation quality, bacterial communities and predicted functions during the ensiling process. Each treatment was prepared in triplicate and stored at room temperature (22-25°C) for 7, 15, and 45 days. The dry matter (DM) and water-soluble carbohydrate content of the silages increased as the LP proportion in the mixed silage increased; at 45 days, the 70% MS + 30% LP, 50% MS + 50% LP and 30% MS + 70% LP silages contained higher (
< 0.05) CP content than the 100% MS and 100% LP silages. The 30% MS + 70% LP and 100% LP silages exhibited lower (
< 0.05) pH and higher (
< 0.05) LA content than the other silages; at 45 days, none of the silages contained PA or BA. As fermentation proceeded, the abundance of harmful (
and
) and beneficial (
,
,
, and
) microorganisms decreased and increased, respectively, as the LP proportion in the mixed silage increased. The predicted functional distribution of microbial communities and metabolic pathways revealed that the 30% MS + 70% LP and 100% LP silages had a stronger capacity for fermentation and a weaker capacity for nitrate reduction than the other silages. Moreover, as the fermentation proceeded, the 30% MS + 70% LP and 100% LP treatments enhanced the functions of "Metabolism," "Genetic information processing" and "Organismal systems" at level 1, the functions of "Amino acid metabolism" and "Nucleotide metabolism" at level 2, and the functions of "Metabolic pathways," "Biosynthesis of secondary metabolites," "Biosynthesis of antibiotics" and "Purine metabolism" at level 3. Thus, adding LP could improve the fermentation quality of MS silage by changing the composition and metabolic function of microbes; furthermore, ensiling 30% alfalfa with 70% ryegrass can produce high-quality silage in the karst region.
Vegetation restoration on abandoned farmlands is one of the typical methods for accumulating soil organic carbon (OC) and total nitrogen (TN). However, the coupling of soil OC and N accumulation ...following vegetation restoration remain poorly known in karst rocky desertification regions in Southwest China. Four natural vegetation restoration lands, namely, grassland, shrubland, secondary forest I, and secondary forest II, were chosen with farmland as a reference. Soil samples were collected to determine the soil aggregates, soil OC and TN accumulation, soil inorganic N content, and soil N transformation rates. The amount of different soil aggregates fractions and stability of soil aggregates, levels of soil OC and TN in whole soil and aggregates, levels of soil inorganic N, and soil N transformation rates were considerably increased by vegetation restoration following farmland abandonment. The increases in total soil OC and TN stocks mainly contributed to the increase of OC and TN stocks in large aggregates. The soil C:N ratios and amount of exchangeable calcium were the important factors associated with soil OC and TN accumulation. Soil net N mineralization and nitrification rates were similar to the patterns of soil OC or TN concentrations in grassland to secondary forest. Soil substrate controlled soil N transformation rates along vegetation restoration. Our results suggested that abandoning farmlands for natural vegetation restoration can improve the soil structure, facilitate the coupled accumulation of soil C and N, and enhance soil N transformation rates and N availability, but the coupling accumulation of soil C and N may be limited by soil N in the early stages of vegetation restoration.
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•Vegetation restoration improved the soil structure, enhanced soil N transformation rates.•Soil OC and TN closely correlation following vegetation succession.•Soil OC and TN accumulation due to the increase of OC and TN in large aggregates.•Soil C accumulation was limited by soil N in the early stage of vegetation restoration.
