•The leaf coloration peak date is correlated with temperature and precipitation.•Generalized additive method can predict the leaf coloration peak date well.•Spring phenology may play an important ...role in predicting autumn phenology.•The leaf coloration peak date can be delayed due to future warming.
The importance of deciduous plants’ autumn phenological phase is reflected not only in the material cycle but also in the fall foliage ecotourism industry. However, the lack of observation data has made it difficult to model the phase of deciduous plants in the high-elevation karst region. Based on the data between 2001 and 2020, methods including multiple linear regression, multivariate binomial regression, robust regression, ridge regression, elastic net, and generalized additive were utilized to find out the correlation of the temperature and the precipitation with Cotinus coggygria’s leaf coloration peak date variation in the related regions of China. The mean absolute error, root mean squared error, coefficient of determination, and ratio of performance to interquartile distance were applied to evaluate the prediction accuracy. Generalized additive model's better performance suggested its capacity as a useful tool in prediction. The results showed that the increase of prophase temperature and the decrease of prophase precipitation could delay the leaf coloration peak date, while the date could be earlier on the contrary. Besides, the number of days with the daily maximum temperature continuously being above 20°C before November 10th exerted the highest contribution in the prediction of the date. Moreover, we showed that a higher average diurnal temperature range in mid-May could defer the date as an objective contributor in prediction. This indirectly reveals the importance of spring phenological phase in predicting the autumn phenological phase. Finally, the model forecasted a trend of the leaf coloration peak date delay from 2021 to 2100 under different emissions scenarios, showing the effects of warming on the plant's growth season and even the development of ecotourism.
Agricultural abandonment has been proposed as an effective way to enhance soil organic carbon (SOC) sequestration. Nevertheless, SOC sequestration in the long term is largely determined by whether ...the stable SOC fractions will increase. Here the dynamics of SOC fractions during post-agricultural succession were investigated in a karst region, southwest China using a space-for-time substitution approach. Cropland, grassland, shrubland and secondary forest were selected from areas underlain by dolomite and limestone, respectively. Density fractionation was used to separate bulk SOC into free light fraction (FLFC) and heavy fraction (HFC). FLFC contents were similar over dolomite and limestone, but bulk SOC and HFC contents were greater over limestone than over dolomite. FLFC content in the forest was greater than in the other vegetation types, but bulk SOC and HFC contents increased from the cropland through to the forest for areas underlain by dolomite. The contents of bulk SOC and its fractions were similar among the four vegetation types over limestone. The proportion of FLFC in bulk SOC was higher over dolomite than over limestone, but the case was inverse for the proportion of HFC, indicating SOC over limestone was more stable. However, the proportions of both FLFC and HFC were similar among the four vegetation types, implying that SOC stability was not changed by cropland conversion. Exchangeable calcium explained most of the variance of HFC content. Our study suggests that lithology not only affects SOC content and its stability, but modulates the dynamics of SOC fractions during post-agricultural succession.
•Both bulk SOC and its heavy fraction are greater over limestone than over dolomite.•SOC and its fractions increase during post-agricultural succession over dolomite.•Lithology affects SOC content and its stability in the karst region.•Agricultural abandonment affects SOC content but not SOC stability.
This research focused on the concentrations, pollution assessment, and source identification of eight heavy metals in acidic farmland of the karst region in China. Two hundred eighty-eight soil ...samples (0–20 cm) were collected from farmland in the karst region of Quanzhou County, Guangxi Province and analysed using multiple methods. The results revealed that the average concentrations of Cd, Pb, Zn, Cr, As, and Hg were higher than the soil background values of China, but lower than the soil environmental quality risk control standards for soil contamination of agricultural land, except for Cd. Based on the spatial distribution and the geoaccumulation index (Igeo), the order of the Igeo values was Cd > Pb > NiZn > Cr > As > Hg > Cu. There was moderate pollution of Cd, slight pollution of Pb and As, and no pollution of Ni, Zn, Cr, Hg, and Cu. Multivariate statistical analyses showed that the accumulation of As, Cr, and Ni in the soils was attributed to weathering of parent carbonate rocks. The accumulation of Cu, Pb, Zn, and Hg was mainly affected by industrial and mining activities. However, Cd mainly originated from parent rock materials and terrain with high natural background levels, followed by agricultural activities (fertilisers). Considering the impacts of these potentially toxic elements on public health, the results of this study are essential for taking preventive actions for environmental protection and sustainable development in the region.
•This is the first study to focus on heavy metals in farmland soil of the karst region, Quanzhou County.•Pollution sources were apportioned in the farmland soil of the karst region using CA and PCA.•Mostly natural and agricultural sources caused heavy metal contamination in the study area.
Biochar (BC) is widely used in soil to increase carbon sequestration. However, the long-term effects of BC application on the soil organic carbon (SOC) and labile organic carbon (LOC) fractions are ...unclear, especially in karst regions. In order to address this issue, two field experiments were designed to observe the changes in the SOC and its fractions after two years of BC application. In this study, we chose karst regions with two different ecological types, Linquan and Heishitou towns in Bijie City, China. Five BC treatment plots were established, with application rates of 0, 5, 15, 20, and 40 t·ha−1 (CK, B5, B15, B20, and B40, respectively). Compared with CK, the contents of SOC, readily oxidizable organic carbon (ROC), particulate organic carbon (POC) and recalcitrant carbon (RC) under the BC treatments in Linquan increased by 7.09–38.08%, 1.62–39.80%, 9.52–62.30% and 8.66–58.14%, respectively. In Heishitou, the increases in these contents were 3.60–38.58%, 4.40–115.23%, 19.57–50.98% and 10.94–53.87%, respectively. There are significant positive relationships between the SOC content and the ROC, POC and RC contents. However, the application of BC had no significant effect on the DOC content in the two ecological regions. In addition, the soil carbon pool index (CPI) and carbon pool management index (CPMI) increased with increasing BC application rate due to its unique physicochemical properties and nutrients. These results indicate that long-term BC amendment significantly improves the soil quality and carbon sequestration in karst regions by increasing SOC and its LOC fractions.
•Tobacco biochar amendment improved soil organic carbon and labile organic carbon fractions in karst regions.•There are significant positive relationships between the SOC content and the ROC, POC and RC contents.•Soil carbon pool index and carbon pool management index increased with increasing biochar application rate.•Long-term biochar amendment significantly improves soil quality and carbon sequestration in karst regions.
In this study, the updated Global Inventory Modeling and Mapping Studies (GIMMS) Normalized Difference Vegetation Index (NDVI) dataset for growing season (April to October), which can better reflect ...the vegetation vigor, was used to investigate the interannual variations in NDVI and its relationship with climatic factors, in order to preliminarily understand the climate impact on vegetation and provide theoretical basis for the response of ecosystem to climate change. Multivariate linear regression models, including the Ordinary Least Squares (OLS) and Geographically Weighted Regression (GWR), were adopted to analyze the correlation between NDVI and climatic factors (temperature and precipitation) together. Average growing-season NDVI significantly increased at a rate of 0.0015/year from 1982 to 2013, larger than several regions in China. On the whole, its relationship with temperature is positive and also stronger than precipitation, which indicated that temperature may be a limiting factor for the vegetation growth in the Karst region. Moreover, the correlation coefficients between grassland NDVI and climatic factors are the largest. Under the background of NDVI increasing trend from 1982 to 2013, the period of 2009-2012 was chosen to investigate the influencing factors of a sharp decline in NDVI. It can be found that the reduced temperature and solar radiation, caused by the increase in cloud cover and precipitation, may play important roles in the vegetation cover change. All in all, the systematic research on the interannual variations of growing-season NDVI and its relationship with climate revealed the heterogeneity and variability in the complicated climate change in the Karst ecosystem for the study area. It is the Karst characteristics that hinder obtaining more representative conclusions and tendencies in this region. Hence, more attention should be paid to promoting Karst research in the future.
Aims
Soil phosphorus (P) cycling in karst regions is mainly regulated by microbial activities. Natural restoration has been widely adopted in the degraded karst regions of southwest China. However, ...the response of functional genes and microbial communities involved in soil P cycling to revegetation has not been well characterized.
Methods
We used metagenomic sequencing to investigate the genes and microorganisms related to soil P cycling derived from natural restoration stages (shrubbery, TG; secondary forest, SG; old-growth forest, OG) in the southeast of Guizhou Province, China.
Results
Natural restoration affected the composition of soil P cycling genes. When TG restored into OG, the relative abundance of organic P (OP) mineralization genes increased from 45.78% to 48.38%, while the genes related to inorganic P (IP) solubilization decreased from 27.19% to 25.03%. The effect of soil nutrients on the relative abundance of OP and IP genes was greater than that of aboveground plant diversity. Structural equation modeling further indicated that soil nutrients directly drove the increase in the relative abundance of OP genes and indirectly impacted the relative abundance of IP genes. The results show that Proteobacteria (38.97%–52.72%) and Actinobacteria (13.44%–29.34%) are the main contributors to soil OP and IP cycling genes, but their contributions vary in different restoration stages.
Conclusions
Natural restoration of the degraded karst vegetation changes the acquisition strategy of soil microbial P by enhancing OP but decreasing IP cycling potentials. This study investigate the regulation of P cycling in the ecological restoration of degraded karst regions from microbial perspective.
•Considerably high SOC stocks were observed in shrubland along the soil profile.•Factors influencing SOC stocks varied with soil horizons examined.•OC content within large macroaggregate was the ...optimal predictor of SOC.•Microaggregates sequestrated more particulate OC than macroaggregates.
Soil aggregation has been recognized as the main mechanism of organic carbon (C; OC) stabilization, and OC dynamics within aggregates are closely linked to soil OC (SOC) sequestration. To unravel the roles of different-sized aggregates and the associated OC fractions in SOC accumulation, SOC stocks (SOCS), aggregate distributions, and OC fractions within aggregates were measured under five typical land-use types (cropland, grassland, shrubland, plantation forest, and natural forest) in a karst faulted basin, China. Land-use type had distinct effects on SOCS in the topsoil (0–10 cm) and along the soil profile (0–60 cm), and the primary factors influencing SOCS varied with the soil horizons. Plantation forest had the highest SOCS (51.2 Mg C ha−1) in the topsoil, whereas the SOCS in shrubland (182.7 Mg C ha−1) was distinctively higher than those of other land-use types across the soil profile. Soil microbial biomass C and mean weight diameter were the major factors driving SOCS variation in the topsoil layer and the entire soil profile, respectively. OC content within macroaggregates (>0.25 mm) was significantly positively correlated with the SOC content of bulk soil, whereas only the mass proportion of large macroaggregates (>2 mm) showed a positive relationship with SOC. Additionally, mineral-associated OC (MAOC) was the dominant fraction of SOC and was abundant in macroaggregates. However, particulate OC (POC) within aggregates was relatively enriched in the topsoil and microaggregates. Considering the decomposition and distribution characteristics of OC fractions in different-sized aggregates, we suggest that the POC/MAOC ratios of macro- and microaggregates could respectively reflect aggregate capacity to sequestrate MAOC and POC across different land-use types. Overall, shrubland is the optimal land-use type for rocky desertification control in the karst fault basin, due to the protection of POC and MAOC within different-sized aggregates.
In this research, we evaluated the effect of exogenous lactic acid bacteria and Amomum villosum essential oil (AVEO) on the chemical composition, microbial community composition, microbial functional ...diversity, and fermentation quality of Broussonetia papyrifera (BP) and Pennisetum sinese (PS) mixed silages. The BP:PS mixing ratios were 100:0, 70:30, 50:50, 30:70, and 0:100. After 3 and 30 days of ensiling at 22°C-25°C, microbial diversity and function, and fermentation quality, were assessed. Increasing PS content resulted in decreased ammoniacal nitrogen and pH, increased water-soluble carbohydrate content, increased relative abundance of Lactococcus and Acinetobacter, and reduced relative abundance of Caproiciproducens and Pseudomonas. A 50:50 BP:PS ratio effectively improved the fermentation quality compared to anaerobic fermentation with BP or PS alone, while AVEO treatment further improved fermentation quality by increasing Lactococcus relative abundance. Moreover, as fermentation proceeded, ensiling enhanced the 'Human diseases', 'Environmental information processing', and 'Cellular processes' functions at the first level, as well as the 'Two-component system' and 'ABC transporters' functions at the third level. Different additives affected the fermentation of BP and PS mixed silage by regulating microbial community succession and metabolic pathways during ensiling.
Background
Soil phosphorus (P) availability is crucial for the restoration of degraded ecosystems, but how soil organic P transforms during post-agricultural succession remains poorly understood in ...karst ecosystems.
Methods
A typical recovery gradient including manual (orchard) and natural (grassland and secondary forest) vegetation restoration after agricultural abandonment was established in a karst region of southwest China. Sequential fractionation, solution
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P nuclear magnetic resonance (NMR) and enzyme assays were performed to investigate the chemical nature and biochemical transformation of organic P during post-agricultural succession in a karst region of southwest China.
Results
We found significant redistributions of soil P fractions from inorganic P to organic P after agricultural abandonment. Specifically, orthophosphate decreased by 10.5% to 34.6%, while phosphomonoester and phosphodiester increased from 9.0% to 33.9% and 0.79% to 2.64%, respectively, during post-agricultural succession. The increased P limitation and organic P substrates induced higher phosphatase activities, with the highest acid phosphomonoesterase activity observed in secondary forest while the highest phosphodiesterase and alkaline phosphomonoesterase activities observed in grassland. Moreover, structural equation modelling demonstrated a clear increase in microbial production of alkaline phosphomonoesterase and the potential hydrolysis of phosphomonoesters under elevated P limitation.
Conclusions
In summary, our findings suggested that agricultural abandonment caused redistributions of soil inorganic P to organic P, with alkaline phosphomonoesterase-mediated phosphomonoester turnover playing a crucial role in soil P availability during post-agricultural succession in karst ecosystem.
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