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1.
在草地生态系统中, 灌木入侵不仅会改变草本植物的分布格局, 还对生态系统的结构和功能产生重要影响。灌丛化的成因、影响、时空动态一直是植被生态学研究的热点问题, 这些问题的探究将有助于理解灌木在天然草原中的作用和地位, 对干旱半干旱区植被的保护和恢复具有重要科学意义。综述了灌丛化的成因、入侵后对生态系统中植被与土壤的影响、草地灌丛化空间动态变化和草地灌丛化演替过程, 以期为将来草地灌丛化的研究提供一些有益途径。  相似文献   

2.
干旱半干旱区灌木、半灌木等木本植物的分布面积持续增加(灌丛化)显著改变了原有植被景观及生态过程,但缺乏对长期封育过程中灌木物种取代草本物种进而影响草地群落组成、结构和功能的研究。为揭示长期封育措施下典型草原灌丛化特征及地上/地下植物群落的响应规律,研究通过对宁夏云雾山典型草原同一封育草地不同时间(2010年、2016年、2021年)植物群落(物种重要值、丰富度、多样性和生物量)和土壤特性(土壤容重、土壤水分及储水量、养分、pH)的定点观测,探讨了长期封育过程中灌木物种矮脚锦鸡儿(Caragana brachypoda)驱动的植被和土壤特性变化。结果表明,(1)灌木矮脚锦鸡儿已经取代草本植物成为封育草地的优势种,群落中灌木生物量、总生物量以及盖度、高度显著增加,但对植物密度的影响较小;(2)灌丛化过程中草地群落Patrick丰富度指数、Simpson优势度指数和Shannon-Wiener多样性指数显著降低,而Pielou均匀度指数显著增加;(3)灌丛化引起土壤深层(60-100 cm)容重显著增大,土层储水量随土层深度的增加呈先减少后增加的趋势;(4)灌丛化使得土壤有机碳含量在浅层(0...  相似文献   

3.
李小军  高永平 《生态学报》2012,32(24):7828-7835
以腾格里沙漠东南缘沙质草地和灌丛生境为研究对象,采用人工模拟降雨实验对草地样方、灌丛间裸地样方及含灌丛斑块样方的产流及氮流失过程进行观测,揭示了地表径流及其引起的氮流失对沙质草地灌丛化的响应.结果表明:(1)草地样方出现表面积水和地表径流的时间及开始产流需要的降雨量均大于含灌丛斑块样方和灌丛间裸地样方,裸地样方最小;灌丛生境径流系数为34.46%,显著小于裸地样方,大于含灌丛样方,产流量是沙质草地生境的2.26倍;表明灌木入侵造成的植被盖度下降引起了土壤水分入渗率的减小和地表产流的增加.(2)含灌丛样方单位体积径流含氮量瞬时值大于裸地样方,小于草地样方,三类样方瞬时值与单位时间径流量均呈线性负相关;草地样方单位时间氮流失量略小于含灌丛样方,两者均显著小于灌丛间裸地样方;灌丛生境氮流失总量为0.23 g/m2,是草地生境的2.09倍,灌丛和草地生境单位体积径流含氮量总体平均值分别为0.011 g/L、0.012 g/L;表明沙质草地灌丛化引起了养分流失的显著增加.  相似文献   

4.
王乐  杜灵通  马龙龙  丹杨 《生态学报》2022,42(1):246-254
宁夏盐池县从20世纪70年代开始在荒漠草原上人工种植柠条灌木用以防风固沙和生态恢复,这一人为措施极大地改变了区域生态系统的植被结构和碳循环,而定量评估人工灌丛化对荒漠草原生态系统碳储量的影响,不仅能够揭示人类活动的碳循环反馈机制,而且可为地方政府生态治理提供理论指导。结合Biome-BGC模型和Logistics生长模型模拟了1958—2017年间荒漠草原人工灌丛化前后的碳储量变化,定量分析了人工灌丛化对生态系统碳储量和组分的影响。结果表明:(1)结合Biome-BGC模型和Logistics生长模型可以较准确地模拟出荒漠草原人工灌丛化过程中生态系统碳储量的变化。(2)人工灌丛化会快速改变荒漠草原的碳储量累积特征,柠条灌木种植后的快速生长阶段极大增强了生态系统的总碳储量,导致生态系统的碳储量特征由草地型向灌木型转变。(3)人工灌丛化改变了生态系统各类型碳储量的组分结构,其对地上植被和枯落物碳储量的影响非常明显,灌丛化后生态系统的植被和枯落物碳分别增加了6倍和1.76倍;因植被碳向土壤碳转化过程较慢,故人工灌丛化对地下土壤碳储量的影响在短期内较为微弱。以上结果显示,荒漠草原人工灌丛化能显...  相似文献   

5.
中国北方草地普遍出现灌丛化现象,灌丛化改变植物群落结构、植物多样性和生产力,直接影响着草地生态保护与可持续利用。该研究以黄土高原灌丛化草地为研究对象,通过植被调查,分析比较不同坡向的灌丛斑块与禾草斑块植物群落结构(物种组成、优势种及物种多样性)和地上生物量的差异。结果发现:(1)灌丛化草地不同坡向对物种多样性及地上生物量均无显著影响(P 0.1),但不同斑块植物群落结构(P=0.001)及地上生物量(P0.001)存在显著差异。(2)灌丛化草地共出现植物29种,其中禾草斑块有27种,灌丛斑块有18种;灌丛化显著改变了植物群落的物种组成,优势种由长芒草(Stipa bungeana)更替为矮脚锦鸡儿(Caragana brachypoda),且灌丛化降低了草地物种丰富度,增加了群落均匀度。(3)灌丛化显著改变了草地地上生物量,其中灌丛斑块地上生物量较禾草斑块地上生物量增加251.2 g·m~(-2),灌丛斑块中灌木/半灌木地上生物量提高了452.1 g·m~(-2),多年生丛生禾草减少了176.5 g·m~(-2),其余功能群植物的地上生物量减少了24.4 g·m~(-2)。(4)灌丛化过程(从禾草斑块—灌丛斑块)中,植物种丢失对地上生物量减少的影响较小,新增物种和群落优势种更替促进了灌木斑块地上生物量增加;虽然灌丛化导致草地地上生物量增加,但植物物种丰富度降低和优势种更替很有可能改变草地多样性和稳定性维持机制。  相似文献   

6.
 回顾了半干旱地区天然草地灌丛化的成因和机理、灌丛化导致草地土壤水分和养分空间异质性及其对生态系统生物地球化学过程的影响,以及土壤异质性与土地退化关系等方面的研究进展,周期性气候干旱和过度放牧是天然草地灌丛化的主要原因,伴随灌木入侵而出现的草地土壤水分和养分的空间异质性,是造成生态系统水分和养分流失,以及土壤加速侵蚀的原因之一。因此,半干旱地区天然草地的灌丛化应得到一定的控制,使群落中灌丛保持适宜的密度,以避免生态系统水分和养分的损失。  相似文献   

7.
江西荒山灌木草丛的群落学特征及开发利用   总被引:6,自引:1,他引:5  
叶居新 《生态学报》1982,2(4):317-326
在以往中亚热带植被研究中所提到的有关概念,如草坡、荒坡、山地草原、荒山草甸、荒山草丛、灌丛高草群落、草山草坡、灌丛与荒山草地、次生灌草丛、亚热带次生稀树草丛、草灌丛、亚热带草丛、丘陵荒山荒地、丘陵荒坡和亚热带稀树灌木草原等等,均可认为是亚热带荒山灌木草丛的同义语。但,为与Steppe、Meadow(Prata)、Savannah及撩荒地等加以区别,我们采用了“荒山灌木草丛”的术语,而冠以“荒山”二字是为体现其动态特点和人为利用特点。 亚热带荒山灌木草丛在植被类型学上属于“灌丛和灌草丛”植被型组,但却分属于不同的植被型和植被亚型。可见“荒山灌木草丛,并非植被类型学的概念,而是亚热带地区地  相似文献   

8.
近几十年来,内蒙古典型草原小叶锦鸡儿(Caragana microphylla)灌丛化现象普遍发生,严重影响了草地生产力。平茬作为灌丛化草地主要管理方式之一,已受到广泛关注;然而平茬如何影响灌丛邻居植物群落的格局动态及其下土壤理化性质变化,仍缺少相应研究。以内蒙古草原小叶锦鸡儿灌丛化草地为研究对象,进行平茬处理,并依据距离小叶锦鸡儿灌丛的远近位置(远—2.5 m,近—0.5 m)设置样方进行植物群落调查和土壤样品的采集,经分析发现:(1)平茬处理显著提高了灌丛邻居植物群落均匀度及邻居植物群落下土壤全碳、全氮含量。(2)借助零模型(Null-model)分析,得出未平茬处理条件下,距离灌丛远近两种位置群落均表现为竞争性格局;而平茬处理条件下,群落竞争性格局作用弱化,且距离灌丛2.5 m位置处群落表现为促进性格局。(3)调查群落中物种间的关系多为中性作用;仅有少数物种对表现为显著正(或负)相互作用关系,且多由群落中优势物种组成;平茬处理条件下群落中显著负相互作用关系物种对比例下降,支持群落整体竞争性格局弱化这一结论。所得结果不仅为小叶锦鸡儿灌丛平茬处理条件下邻居植物群落及土壤环境的动态变化的探讨提供了实验依据,而且对灌丛化草地的恢复具有一定的实践指导意义。  相似文献   

9.
生态安全条件下土地利用格局优化——以皇甫川流域为例   总被引:5,自引:0,他引:5  
喻锋  李晓兵  王宏 《生态学报》2014,34(12):3198-3210
在人类活动导致的生态环境问题中,土地利用格局变化对区域生态安全起着决定性作用。选择我国乃至在世界上都罕见的多沙、粗沙、强烈水土流失的黄河皇甫川流域作为研究区域,针对土壤侵蚀和生态用水这两大影响流域生态安全的关键问题,开展土地利用变化模拟、土壤侵蚀3S监测、适宜植被盖度估算、土壤侵蚀情景模拟、土地利用格局优化等方面的综合研究。结果表明:(1)土地利用格局变化是导致土壤侵蚀变化的重要因素。从1987年到2015年,建筑用地、林地和灌丛面积增加,水域、沙地和裸砒砂岩面积减少,导致流域年平均土壤侵蚀模数由16160.72 t km-2a-1降至9710.72 t km-2a-1。(2)土地利用类型与土壤侵蚀模数密切相关并存在一定规律。6种不同土地利用类型多年平均土壤侵蚀模数的大小顺序为:裸砒砂岩沙地耕地草地林地灌丛,表明灌、林措施是流域植被恢复和土壤侵蚀减少的首选。(3)土地利用结构和空间格局优化有助于提升区域生态安全水平。在优化格局下,2007年和2015年土壤侵蚀模数比优化前分别减少5469.57 t km-2a-1和5432.77 t km-2a-1,优化后2015年土壤侵蚀模数仅为4277.95 t km-2a-1,低于流域自然侵蚀临界值或允许土壤侵蚀模数5300 t km-2a-1,优化土地利用格局成为加强流域生态环境建设的重要途径。  相似文献   

10.
草原灌丛化是全球干旱半干旱地区面临的重要生态问题。灌丛化对草原生态系统结构与功能的影响较为复杂, 有待于在更广泛的区域开展研究。该研究在内蒙古锡林郭勒典型草原选择轻度、中度和重度灌丛化草地, 通过群落调查, 结合植物功能性状和土壤理化性质观测, 研究了小叶锦鸡儿(Caragana microphylla)灌丛化对草原群落结构(物种多样性、功能多样性和功能群组成)和生态系统功能(初级生产力、植被和土壤养分库)的影响。结果表明: 1)不同程度灌丛化草地的物种丰富度、功能性状多样性和群落加权性状平均值差异显著, 其中, 中度灌丛化草地的物种多样性和功能多样性较高, 表明一定程度的灌丛化有利于生物多样性维持。2)重度灌丛化草地的地上净初级生产力(ANPP)显著高于轻度和中度灌丛化草地, 其原因主要是随着灌丛化程度加剧, 群落内一/二年生草本植物显著增加, 而多年生禾草和多年生杂类草显著减少。三个灌丛化草地的植被叶片和土壤碳、氮库差异均不显著。3)灌丛化对草原生态系统功能包括ANPP、植被和土壤养分库均没有直接的影响, 而是通过影响功能群组成、土壤理化性质和功能多样性, 间接地影响生态系统功能; 灌丛化导致功能群发生替代和土壤旱碱化是最重要的生物和非生物因素。  相似文献   

11.
Aims Shrub encroachment is a common global change phenomenon occurring in arid and semi-arid regions. Due to the difficulty of partitioning evapotranspiration into shrub plants, grass plants and soil in the field, there are few studies focusing on shrub encroachment effect on the evapotranspiration and its component in China. This study aims to illustrate shrub encroachment effect on evapotranspiration by the numerical modeling method. Methods A two-source model was applied and calibrated with the measured evapotranspiration (ET) by the Bowen ratio system to simulate evapotranspiration and its component in a shrub encroachment grassland in Nei Mongol, China. Based on the calibrated model and previous shrub encroachment investigation, we set three scenarios of shrub encroachment characterized by relative shrub coverage of 5%, 15% and 30%, respectively, and quantified their effects caused by shrub encroachment through localized and calibrated two-source model. Important findings The two-source model can well reconstruct the evapotranspiration characteristics of a shrub encroachment grassland. Sensitivity analysis of the model shows that errors for the input variables and parameters have small influence on the result of partitioning evapotranspiration. The result shows that shrub encroachment has relatively small influence on the total amount of ET, but it has clear influence on the proportion of the components of evapotranspiration (E/ET). With shrub coverage increasing from 5% to 15% and then 30%, the evapotranspiration decreased from 182.97 to 180.38 and 176.72 W·m-2, decreasing amplitude values of 0.34% and 0.44%, respectively. On average, E/ET rises from 52.9% to 53.9% and 55.5%, increasing amplitude values to 2.04% and 3.25%. Data analysis indicates that shrub encroachment results in smaller soil moisture changes, but clear changes of ecosystem structure (decreasing ecosystem leaf area index while increasing vegetation height) which lead to the decrease of transpiration fraction through decreasing canopy conductance. The research highlights that, with the shrub encroachment, more water will be consumed as soil evaporation which is often regarded as invalid part of evapotranspiration and thus resulting in the decrease of water use efficiency.  相似文献   

12.
Wind is a key abiotic factor that influences the dynamics of arid and semiarid systems. We investigated two basic relationships on vegetation manipulation (grass cover reduction) plots at the Jornada Experimental Range in southern New Mexico: (1) wind erosion rates (horizontal mass flux and dust emission) versus vegetative cover, and (2) nutrient loss versus vegetative cover. The results indicate that wind erosion rates and nutrient loss by dust emission are strongly affected by plant cover; however, the importance of shrubs and grasses in reducing dust flux may not be equal. The dramatic increase of wind erosion between 75% grass cover reduction and 100% grass cover reduction suggests that sparsely distributed mesquites are relatively ineffective at reducing wind erosion and nutrient loss compared to grasses. Comparisons of nutrients between surface soils and wind blown dust indicate that aeolian transport is a major cause for the loss of soil nutrients in susceptible environments. We found that increased aeolian flux over three windy seasons (March 2004–July 2006) removed up to 25% of total organic carbon (TOC) and total nitrogen (TN) from the top 5 cm of soil, and about 60% of TOC and TN loss occurred in the first windy season (March–July 2004). The balance between net loss of nutrients by aeolian processes and the addition of nutrients by biotic processes changed from negative (net loss) to positive (net accumulation) between 50% grass cover reduction and 25% grass cover reduction. The estimated lifetime of surface soil TOC and TN of about 10 years on the plot with 100% grass cover reduction indicates that impacts of wind erosion on soil resources can occur on very short timescales.  相似文献   

13.
《农业工程》2021,41(4):304-317
Drylands cover more than 40% of the land surface of the Earth and are characterized by patchy vegetation and that permits erosion of the surface. Vegetation-aeolian transport is an important feedback in drylands, particularly those undergoing shrub encroachment. Although one side of the feedback, the influence of vegetation loss on aeolian transport, has been well studied, the other, the influence of aeolian transport on existing vegetation, has been never studied in detail. In this study, a new ecological-wind erosion model (ECO-WEMO) that contains an aeolian transport component was created to simulate how aeolian transport impacts vegetation pattern and causes the state change. Two modeling scenarios were investigated: 1) stable grass and shrub communities without/with aeolian transport and 2) unstable shrub and grass communities without/with aeolian transport disturbed by different drought conditions. The first scenario focuses on the simulation of the influence of aeolian transport on vegetation communities and the second scenario focuses on the simulation of the state change of vegetation communities. The results from the first scenario show that: First, the mean biomasses of grass and shrub become consistent in the case of no wind in both shrub-dominated and grass-dominated communities. Second, the mean biomass of shrub becomes higher than the grass in the case of wind in shrub-dominated communities and the mean biomass of grass becomes higher than the shrub in the case of wind in grass-dominated communities. Third, the dust flux of shrub-dominated communities is higher than the grass-dominated communities. Fourth, the net change in surface height in shrub-dominated communities has a considerably higher range than in grass-dominated communities. Fifth, the spatial pattern of shrub-dominated communities is sparser than the spatial pattern of grass in the vegetation communities in the case of wind. The results from the second scenario show that: First, the state change only took place from grass-dominated communities to shrub-dominated communities in the condition of drought. Second, the state change only took place in the case of wind. Third, the state change didn't take place after the slight and moderate droughts but only took place after the drought. Fourth, large vegetation biomass reduction only took place in the case of wind after the severe drought. Our results confirm, in a modeling context, the important role that aeolian transport can play in vegetation dynamics and state change in deserts.  相似文献   

14.
Vegetation mosaics of grassland/savanna and forest can be found in tropical and subtropical regions of the world, as in southern Brazil, where climate conditions are suitable for forest. Changes in intensity or frequency of disturbances could enable woody species encroachment in grassland communities; however, the processes are related to site conditions and life history of pioneer species. In this paper, we study transition patterns of forest to grassland in the absence of grazing, but under different site conditions related to aspect (landscape position) and time since the last burn. Data are based on shrub and tree species composition and soil variables at forest–grassland boundaries. We found 119 woody species of 42 families along transects of 27 m into the forest and 31.5 m into the grassland. Gradients from forest to grassland were analysed as compositional trajectories in ordination space and differences in the spatial patterns depicted between distinct site aspects. The time since the last fire did not influence these patterns. Inside the forest, tree species diversity was significantly higher close to the edge, independent of the density of individuals. Two main mechanisms may promote forest expansion into the grassland. First, a gradual tree encroachment near the edge and, second, a mechanism linked to the recruitment of isolated pioneer trees within the grassland matrix, most frequently near rocky outcrops, where a decrease in grass biomass leads to low-intensity fires. Despite vegetation patterns at boundaries differing according to aspect, the most important explanatory factor was the distance from the forest border, not just by itself, but with all correlated parameters that are changing along the gradient.  相似文献   

15.
Aims: Shrub-encroached grassland has become an important vegetation type in China's arid and semi-arid region. Our study objective is to explore the spectral features of shrub and grass communities, as well as their empirical relationships with shrub coverage. The quantitative estimation of shrub cover based on medium-resolution Landsat satellite imagery provides the practical basis for long term retrieval of large areas of shrub expansion in the grassland region. Methods: Linear models and Multiple Endmember Spectral Analysis Model (MESMA) based on medium resolution Landsat satellite imagery were developed to quantify the shrub coverage in a shrub-encroached grassland region in Xianghuang Banner, Nei Mongol using the spectral features and their seasonal differences between the shrub and grass communities. Important findings: Compared to Leymus chinensis and Stipa krylovii dominated grass communities, Caragana microphylla community had a higher normalized difference vegetation index (NDVI), modified red edge normalized difference vegetation index (mNDVI705), and red edge slope. The red edge position of C. microphylla community shifted to longer wavelengths. The average and the maximum shrub coverage was 13% and 25%, respectively, in the shrub-encroached grassland based on both models. The correlation coefficient of determination (R2) and root mean square error (RMSE) of the linear model was 0.31 and 0.05, respectively. We found that the linear model based on seasonal differences of shrub and grass community was more suitable for retrieving shrub coverage in the study area from medium resolution imagery than the MESMA model that is based on mid-summer images.  相似文献   

16.
Semi-natural grasslands are key habitats for biodiversity conservation in Central Europe. Shrub encroachment is one of the most threatening drivers of grassland degradation and affects soil properties, microclimate, and vegetation with possible impacts on higher trophic levels. We aimed to analyse the impact of shrub encroachment with broom (Cytisus scoparius) on carabid beetle diversity, species composition, and functional traits. In a field study on dry grasslands on the island of Hiddensee (Germany) we studied 15 sites along a gradient of increasing broom encroachment and classified them into three dry grassland types with low, medium, and high shrub cover. Our results provide evidence that shrub encroachment initially has positive effects on species richness and activity densities of dry grassland carabids. Carabid species composition differed among differently shrub-covered dry grassland types, and sites with low and high shrub cover were each characterised by unique carabid assemblages. The species composition of sites with a medium shrub biomass had a transitional character and contained species which are typical for open dry grassland, but also shared species with sites with a high shrub cover. Among functional trait parameters investigated, especially the body size of carabid beetles was related to environmental parameters associated with shrub encroachment. Body size was positively correlated to shrub biomass and soil humidity, but negatively to temperature. Eurytopy values of carabids were related to high litter cover, i.e. habitat generalist (eurytopic) species mainly occurred in densely shrub-encroached sites. In order to preserve unique carabid assemblages of open dry grasslands with stenotopic and smaller species, it is most important to prevent a shrub encroachment higher than about 60% cover. For management we suggest extensive grazing (by cattle, sheep or horses) to prevent shrub encroachment on dry grasslands. In areas with high shrub cover additionally the use of goats or mechanical removal of shrubs might be necessary.  相似文献   

17.
Desert grasslands, which are very sensitive to external drivers like climate change, are areas affected by rapid land degradation processes. In many regions of the world the common form of land degradation involves the rapid encroachment of woody plants into desert grasslands. This process, thought to be irreversible and sustained by biophysical feedbacks of global desertification, results in the heterogeneous distribution of vegetation and soil resources. Most of these shrub-grass transition systems at the desert margins are prone to disturbances such as fires, which affect the interactions between ecological, hydrological, and land surface processes. Here we investigate the effect of prescribed fires on the landscape heterogeneity associated with shrub encroachment. Replicated field manipulation experiments were conducted at a shrub-grass transition zone in the northern Chihuahuan desert (New Mexico, USA) using a combination of erosion monitoring techniques, microtopography measurements, infiltration experiments, and isotopic studies. The results indicate that soil erosion is more intense in burned shrub patches compared to burned grass patches and bare interspaces. This enhancement of erosion processes, mainly aeolian, is attributed to the soil–water repellency induced by the burning shrubs, which alters the physical and chemical properties of the soil surface. Further, we show that by enhancing soil erodibility fires allow erosion processes to redistribute resources accumulated by the shrub clumps, thereby leading to a more homogeneous distribution of soil resources. Thus fires counteract or diminish the heterogeneity-forming dynamics of land degradation associated with shrub encroachment by enhancing local-scale soil erodibility. Author Contributions  SR—Conceived of or designed study, performed research, analyzed data, wrote the paper; PD—Conceived of or designed study, performed research, wrote the paper; LW—Performed research, analyzed data; GO—Contributed new methods, analyzed data; SC—Conceived of or designed study; CW—Performed research, contributed new methods or models; and SM—Contributed new methods or models.  相似文献   

18.
Many arid grassland communities are changing from grass dominance to shrub dominance, but the mechanisms involved in this conversion process are not completely understood. Aeolian processes likely contribute to this conversion from grassland to shrubland. The purpose of this research is to provide information regarding how vegetation changes occur in an arid grassland as a result of aeolian sediment transport. The experimental design included three treatment blocks, each with a 25 × 50 m area where all grasses, semi-shrubs, and perennial forbs were hand removed, a 25 × 50 m control area with no manipulation of vegetation cover, and two 10 × 25 m plots immediately downwind of the grass-removal and control areas in the prevailing wind direction, 19° north of east, for measuring vegetation cover. Aeolian sediment flux, soil nutrients, and soil seed bank were monitored on each treatment area and downwind plot. Grass and shrub cover were measured on each grass-removal, control, and downwind plot along continuous line transects as well as on 5 × 10 m subplots within each downwind area over four years following grass removal. On grass-removal areas, sediment flux increased significantly, soil nutrients and seed bank were depleted, and Prosopis glandulosa shrub cover increased compared to controls. Additionally, differential changes for grass and shrub cover were observed for plots downwind of vegetation-removal and control areas. Grass cover on plots downwind of vegetation-removal areas decreased over time (2004-2007) despite above average rainfall throughout the period of observation, while grass cover increased downwind of control areas; P. glandulosa cover increased on plots downwind of vegetation-removal areas, while decreasing on plots downwind of control areas. The relationships between vegetation changes and aeolian sediment flux were significant and were best described by a logarithmic function, with decreases in grass cover and increases in shrub cover occurring with small increases in aeolian sediment flux.  相似文献   

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