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81.
Chen Tiantian Wang Qiang Wang Yuxi Peng Li 《Land Degradation u0026amp; Development》2023,34(16):5055-5070
In light of the recent pressure from global warming, extreme drought events, and deleterious human activity, the strength and long-term change trends of vegetation in karst regions—in terms of their resistance to external disturbances—have not been studied systematically. Therefore, herein, we quantified the vegetation resilience and its nonlinear change trends in south China karst under different environmental gradients by measuring the lag-1 autocorrelation to time-series Normalized Difference Vegetation Index (1990–2018), clarifying the driving forces of vegetation resilience changes. It was shown that the vegetation resilience change in south China karst was not monotonous. In the first stage (pre-2002), precipitation and warming promoted the increase of regional vegetation resilience (slope = −0.045, p < 0.0001). In the second stage (during 2002–2010), the increasing trend of vegetation resilience was not obvious and vegetation resilience was difficult to keep up with vegetation productivity, indicating the time-lagged effect of ecological restoration projects to vegetation resilience. In the third stage (post-2010), due to the continuous advancement of ecological restoration projects, vegetation resilience increased significantly and had the largest amplitude (slope = −0.128, p < 0.0001). Simultaneously, under different environmental gradients, vegetation resilience showed significant differentiation characteristics. In comparison to non-karst regions, increases in the vegetation resilience were more obvious in karst regions especially in the post-2010. With increases in the soil depth, the vegetation resilience exhibited an increasing trend, indicating its dependence on soil. At slopes >25°, the vegetation resilience increased most obviously and the resilience of meadows was the largest, which can be the preferred vegetation type for ecological restoration projects. This research provides another perspective to understand karst vegetation ecosystem and the results will facilitate the protection of karst ecosystems. 相似文献
82.
Xiaolu Sun Michael G. Ryan Zuoxin Tang Bisheng Wang Quanxiao Fang Osbert Jianxin Sun 《Land Degradation u0026amp; Development》2023,34(14):4358-4372
Categorization of soil organic carbon (SOC) into different functional subpools according to their recalcitrance and protective mechanisms helps better understand ecosystems organic carbon (OC) dynamics, and various attempts have been made to explore the suitable experimental fractionation method for such purpose. However, most previous studies neglected the influences of environmental factors on the effectiveness of varying fractionation methods. Density fractionation has shown great promise in elucidating SOC immobilization mechanisms. Here, we compared three varying types of density fractionation methods (density, density + dispersion, and density + other procedures) for categorizing the SOC into three functional pools, that is, active OC (OCactive), moderately stable OC (OCm-stable), and stable OC, (OCstable) using global data compiled for 95 sites in 31 published studies, and examined the influences of climate (mean annual temperature [MAT] and annual precipitation), vegetation type, and soil properties (soil depth, clay content, and soil type) on SOC fractions determined by the three density fractionation methods. The percentage of OCm-stable fraction was found to be highest using the density method and lowest using the density + dispersion method, due to differential density ranges between the two methods. At a global scale, the contents of total SOC and its OC fractions decreased with temperature. Precipitation had no apparent influences on the subdivided SOC fractions using either the density + dispersion method or the method of density + other procedures, whereas soil type constrained the effect of precipitation on SOC fractions using the density method. The percentage of OCm-stable determined by the density + dispersion method was more responsive to MAT and vegetation type than that by the other two methods. The percentage of OCstable determined by the method of density + other procedures was significantly and positively related to the clay content as the OCstable based on this method included small particles. For all the three methods of fractionation, soil type had a greater influence than the clay content on the SOC fractions, especially the OCm-stable and the OCstable. For soil type characterized by rich metal oxides, both the density method and the method of density + other procedures could be used for SOC fractionation. For soil type rich in nutrients, the density + dispersion method would have higher sensitivity for distinguishing the OCm-stable. 相似文献
83.
Stratified vegetation cover index: A new way to assess vegetation impact on soil erosion 总被引：1，自引：0，他引：1
Vegetation cover is an important parameter used in assessing the relationship between vegetation and soil erosion. However, the intensity of soil erosion actually changes not only with vegetation cover but also with differences in vegetation type and structure. How to integrate the cumulative effect of the different growth forms making up a vegetation community into one index for inclusion in soil loss predictive equations is an open research question. This paper proposes a method to separately measure the cover of different vegetation strata, estimate their contribution to reducing soil loss, and then to integrate this into a single vegetation index called the stratified vegetation cover index (Cs). The results show that Cs is more effective than projected vegetation cover for the assessment of soil erosion and also can overcome the disadvantages of vegetation indices such as NDVI. This means that Cs is a good substitute for vegetation cover or cover-related vegetation indices in studies on the relationship between vegetation and soil erosion. The concept of Cs may help the local governors or forest department understand the importance of vegetation structure and make right management decisions. 相似文献
84.
《Land Degradation u0026amp; Development》2018,29(2):337-348
Understanding the impact of grazing patterns on grassland production is of fundamental importance for grassland conservation and management. The objective of this study is to obtain an understanding of the trade‐offs between aboveground biomass and belowground biomass, which are influenced by environmental factors in free grazing (FG) and grazing exclusion (GE) alpine grasslands on the Tibetan Plateau. We explored the relationships between the trade‐off and environmental factors using correlation analysis, a generalized additive model and a structural equation model, and then found that the key factors that determine trade‐off showed differences in FG and GE grasslands and that the final structural equation modeling result explained that 96% (path coefficient = 0.96) and 65% (path coefficient = 0.65) of the variations in the trade‐off were due to FG or GE classifications, respectively. The results demonstrated that soil organic carbon, soil carbon/soil nitrogen, and soil available nitrogen affect the trade‐off between aboveground and belowground biomass in FG grasslands more obviously than in GE grasslands. However, the effects of growing season temperature on the trade‐off were insignificant, −0.218 and −0.181 in FG and GE grasslands, respectively. FG increased the soil bulk density, which resulted in an alteration in the soil pore size distribution and a greater resistance to root penetration. In addition, FG affected the level of soil nutrition, which will affect the nitrogen mineralization of decomposition and absorption, as well as the root biomass. Consequently, this study can provide guidance to improve the quality of grassland. 相似文献
85.
《Land Degradation u0026amp; Development》2018,29(4):1031-1040
In arid and semiarid areas, the importance of soil inorganic carbon (SIC) is at least as high as that of soil organic carbon (SOC) in affecting the regional carbon budget following vegetation rehabilitation. However, variations in SIC have been uncertain, and few studies have analyzed the interactions between the SOC and SIC pools. We measured SIC, SOC, δ13C‐SIC, and δ13C‐SOC after planting Mongolian pine (MP) and Artemisia ordosica (AO) on shifting sand land (SL) over 10 years in the Mu Us Desert, northwest China. The results showed that, compared to SL, SIC stocks at 0–100 cm in MP and AO lands significantly increased by 12.6 and 25.8 Mg ha−1, respectively; SOC stocks in MP and AO lands significantly increased by 24.0 and 38.4 Mg ha−1, respectively. Both δ13C‐SIC and δ13C‐SOC in the 2 plantation lands were significantly lower than those in SL were. All 315 samples exhibited a negatively linear relationship between SIC content and δ13C‐SIC (R2 = .70, p < .01) and showed positively linear relationships between SIC content and SOC content (R2 = .69, p < .01) and between δ13C‐SIC and δ13C‐SOC (R2 = .61, p < .01). The results demonstrated that vegetation rehabilitation on SL has a high potential to sequester SIC and SOC in semiarid deserts. The reduction in δ13C‐SIC and the relationship of SIC with δ13C‐SIC following vegetation rehabilitation suggested that SIC sequestration is likely caused by the formation of pedogenic inorganic carbon. The relationships between SIC and SOC and between δ13C‐SIC and δ13C‐SOC implied that the pedogenic inorganic carbon formation may be closely related to the SOC accumulation. 相似文献
86.
《Land Degradation u0026amp; Development》2018,29(5):1427-1441
In the dryland and degraded regions, soil moisture is the primary factor determining ecological restoration. Proper land preparations and vegetation restoration can improve soil moisture and benefit land restoration. Identifying their effects on soil moisture is thus essential for developing suitable management strategies. In this study, four typical land preparation techniques (level ditches, fish‐scale pits, zig terraces, and level benches) and non‐native vegetation types (Prunus armeniaca, Platycladus orientalis, Pinus tabulaeformis, and Caragana microphylla) were planted on a semiarid loess hilly catchment, China. Soil moisture was monitored by a time‐domain reflectometer, and its spatial–temporal variations were analyzed during the 2014–2015 growing seasons. The following results were captured. (a) Soil moisture was highest for the combination of P. orientalis and fish‐scale pits (P. orientalis/fish‐scale pits, 10.37%), followed by P. armeniaca/level ditches (10.23%), P. orientalis/zig terraces (9.67%), C. microphylla/level benches (8.62%), P. tabulaeformis/fish‐scale pits (8.05%), and P. tabulaeformis/zig terraces (7.72%). (b) Fish‐scale pits offered a better rainwater‐harvesting capacity during the rainy months, whereas zig terraces had a higher water retention capacity under extremely dry conditions (as indicated by the temporal soil moisture variation and soil water retention curves). (c) P. tabulaeformis consumed more water than other vegetation types (26.7% lower than that of P. orientalis). (d) Soil moisture in shallower layers (0–80 cm) was more affected by land preparations and was more effected by vegetation types in deeper soil layers (80–180 cm). We thus suggest that fish‐scale pits may be a better choice in wetter regions whereas zig terraces and P. orientalis are more suitable in the driest parts of the Loess Plateau to restore the fragile ecosystems. 相似文献
87.
《Land Degradation u0026amp; Development》2018,29(5):1385-1396
The study aimed to identify hydrological and landscape factors that influence sediment transport in 2 agricultural catchments in north‐western France—Moulinet and Kervidy‐Naizin—with the same climate, size, and bedrock but with contrasting suspended sediment (SS) fluxes. Discharge and SS concentrations were continuously monitored at the catchment outlets for 9 hydrological years. Data were examined at annual, seasonal, and individual storm‐flow event scales. Storm events were classified into 3 types—single small, successive, and major events—whose effect on sediment transport was studied. At the annual scale, SS yields were higher in Moulinet (16–63 × 103 kg km−2) than in Kervidy‐Naizin (3–22 × 103 kg km−2) despite similar water fluxes. However, Kervidy‐Naizin had higher potential for hillslope erosion because of more frequent occurrence of saturation excess runoff, more frequent bare soil in cultivated area, and fewer hedgerows. Major storm events were also stronger in this catchment. Although high SS concentrations and fluxes occurred only during a few major events in Kervidy‐Naizin, SS export was always substantial throughout the year in Moulinet. We hypothesised that bank degradation due to cattle trampling generated the higher SS export in the Moulinet catchment. This hypothesis was confirmed by the large decrease in SS fluxes following construction of watering troughs in the middle of the study period. In the Kervidy‐Naizin catchment, natural woody vegetation or grass buffer strips along the stream effectively protect the stream from bank erosion or a possible influx of hillslope erosion particles, except during some major events in winter. 相似文献
88.
《Land Degradation u0026amp; Development》2017,28(7):2137-2145
Clear, degradable polymer films are used with agricultural crops to alter the germination and growing environment and extend the length of the growing season. The film acts like a greenhouse, elevating temperatures and improving soil water. We examined the potential of polymer film to improve emergence and persistence of direct‐seeded native vegetation. A seed mix comprising three tree species and two shrubs was sown in early August 2015, with and without polymer film. The effect of duration of polymer film (from 0–10 weeks) on emergence and persistence was tested, and the effects of polymer film on temperature and soil moisture were monitored. Our hypothesis that polymer film would improve emergence was partially supported, with between 6 and 10 weeks of polymer film coverage increasing emergence of small‐seeded species above the level of the Control. The polymer film increased temperatures by an average of 5 °C and volumetric water content by up to 10%, compared with ambient conditions, and reduced fluctuations in soil moisture, which may have contributed to the increased emergence observed. Emergence was low across all treatments (range 0·2–47%). Our hypothesis that polymer film would improve persistence was not supported, with seedling numbers declining rapidly following removal of the polymer film and no differences between treatments in percentage persistence by the end of the experiment. We concluded that polymer film is a potentially useful tool for improving emergence of smaller‐seeded species in direct seeding for land restoration, although provided no benefit for emergence of the larger‐seeded species. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
89.
Hamid Mahyou Bernard Tychon Marie Lang Riad Balaghi 《African Journal of Range and Forage Science》2018,35(1):1-12
The assessment of rangeland productivity in semi-extensively grazed arid rangelands is a prerequisite for livestock management in relation to sustainable use of pastoral resources. The objective of this study was to assess rangeland productivity based on normalised difference vegetation index (NDVI) images. Data on phytomass were measured on 61 field samples in arid rangelands of Morocco, covering various rangeland categories during autumn (November) and spring (April), i.e. when phytomass is at low and high levels, respectively, for two consecutive years (2008 and 2009). Dekadal EROS Moderate Resolution Imaging Spectroradiometer (eMODIS) NDVI data were linearly regressed to field measurements for these four periods. Results show that phytomass values were correlated with NDVI during spring, with R2 and RMSE values of 0.82 and 0.3 t ha?1, respectively. This study indicates there is a high potential for operational use of remotely sensed data to estimate rangeland phytomass of semi-extensively grazed rangelands. 相似文献
90.