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1.
地表径流对荒漠灌丛生境土壤水分空间特征的影响 总被引：3，自引：2，他引：1
土壤水分是干旱区多尺度生态水文过程的关键影响因素和驱动因子,其时空格局是生态、水文、气象、地形等自然过程研究的重要参数。笔者研究了降水径流事件后3种不同灌丛个体尺度土壤水分空间异质性特征,结果表明,珍珠灌丛个体尺度土壤水分空间分布特征表现为灌丛边缘>灌丛内部>灌丛间裸地,驼绒藜灌丛表现为灌丛内部>灌丛边缘>灌丛间裸地,而狭叶锦鸡儿灌丛不同微生境土壤水分差异不显著。珍珠和驼绒藜灌丛同一微生境土壤水分存在坡位梯度,珍珠灌丛3个微生境土壤水分均表现为上坡位大于下坡位,而驼绒藜灌丛边缘表现为上坡位小于下坡位,其他两个微生境无明显规律;狭叶锦鸡儿灌丛土壤水分无明显的坡位梯度。3种灌丛不同微生境土壤含水量随土层深度增加的变化不明显。这说明在降水径流事件中,不同斑块的反应差异引起了地表径流的形成以及随之发生的资源再分配,从而导致了景观内土壤水分的空间异质性。 相似文献
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3.
生物土壤结皮对荒漠昆虫多样性的影响 总被引：10，自引：6，他引：4
生物土壤结皮广泛分布在干旱半干旱地区与寒区荒漠,是荒漠生态系统的主要组成和景观特征之一,其重要性已被大量的研究报道所证实。然而,关于生物土壤结皮与昆虫种类多样性之间关系的研究却很少。本文以腾格里沙漠东南缘的沙坡头地区半固定沙丘柠条－油蒿群落和固定沙丘柠条－油蒿群落为观测样地,选择具有不同类型生物土壤结皮分布的植被群落为观测样方。昆虫的调查采用100 m×100 m的样方,利用样筐和网捕法收集昆虫,记录昆虫数量,采集标本在室内进行鉴定。结果表明:与无结皮覆盖的植被区相比,生物土壤结皮在地表的覆盖显著地增加了昆虫的多样性和种的丰富度,其中以苔藓和地衣为主的结皮覆盖的植被样方中昆虫种的多样性和丰富度显著地高于以蓝藻和藻类为主的结皮样方。生物土壤结皮对荒漠昆虫多样性的贡献可能是由于稳定了土表、改善了植被系统中的土壤环境,为昆虫,特别是幼虫阶段提供相对适宜的土壤生境或部分食物来源。 相似文献
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干旱区生物土壤结皮对种子植物多样性的影响 总被引：21，自引：13，他引：8
通过调查古尔班通古特沙漠筑路形成的严重干扰样方与自然状态下轻微干扰样方种子植物多样性的差异,结合人为干扰生物土壤结皮样方的结果,综合生物土壤结皮土壤种子库、结皮上种子萌发、生长以及土壤养分与水分的特征,研究生物土壤结皮对种子植物多样性的影响。结果表明：完整结皮与适度干扰后结皮样方内植物多样性指数D分别为0.3296和0.5291,多样性指数H分别为0.8400和1.2957,差异均达到显著水平;严重干扰样方的多样性指数D和多样性指数H均显著低于轻度干扰样方的对应指标。说明对生物土壤结皮 “适度”干扰使其保持在早期发育阶段有利于增加种子植物多样性,而“严重”干扰使结皮变为流沙阶段会降低种子植物多样性。结皮影响种子植物多样性的机理主要在于发育后期的生物土壤结皮会降低土壤种子库,也会抑制多数种类种子萌发,夏秋季结皮深层土壤水分的减少也不利于深根植物的生存,但结皮土壤拥有相对较高的养分条件却能保证一年生短命植物生长和生存。相对于流沙,生物土壤结皮的存在有益于保持相对较高的植物多样性,这可能归功于生物土壤结皮有利于地表稳定性、以及其在防风蚀和土壤形成等方面重要的生态功能,因而,在采取 “适度”干扰措施以提高植物多样性之前需要慎重考虑可能带来的不利影响。 相似文献
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腾格里沙漠人工固沙植被区浅层土壤水分对降水和生物结皮的响应 总被引：2，自引：1，他引：1
选择腾格里沙漠东南缘人工植被区3种典型的地表覆被类型（藓类结皮、藻类结皮和流沙）土壤为对象,选取发生在7月和9月的两次降水事件,研究浅层土壤（3、5、10 cm）水分入渗与再分布过程。结果表明：浅表层3 cm深度土壤水分在降雨初期均表现为跳跃式增加,而在降雨中后期由于土壤剖面不同深度水势梯度减小,降水入渗速率降低,土壤水分仅呈现小幅波动。在两次降水事件中,藓类结皮和藻类结皮对降水入渗的阻碍作用比较显著,入渗速率表现为沙土 > 藻类结皮 > 藓类结皮;从水分再分布看,生物土壤结皮的存在致使水分再分配过程表现出明显的浅层化;降水过程结束后,结皮促进水分的蒸发损失,从而减少植被可利用水分含量。人工固沙植被区广泛发育的生物土壤结皮对降水入渗与再分布过程以及土壤水量平衡具有重要影响。 相似文献
6.
干扰对生物土壤结皮及其理化性质的影响 总被引：13，自引：2，他引：11
生物土壤结皮作为荒漠地区特殊环境的产物,具有较强的抗风蚀、水蚀功能,也是干旱荒漠地区植被演替的重要基础。随着人类活动的加剧,生物土壤结皮也受到不同类型和不同程度的干扰,主要包括放牧、火烧、车辆碾压等形式。干扰对生物土壤结皮的影响主要表现在生物土壤结皮结构及盖度的变化、土壤理化性质的改变、土壤微生物数量及活性的变化等几个方面。放牧对土壤物理性质的影响还没有一致的结论,除了干扰的程度还与土壤含水量有关系。火烧虽然改善了土壤结构,但是破坏了地表植被的盖度,而且恢复比较困难,也加速了外界侵蚀的力度,对土壤化学性质也有显著影响。机械碾压的破坏力最强,且没有任何的积极意义。 相似文献
7.
灌丛对沙质草地土壤结皮形成发育的影响及其作用机制 总被引：1，自引：0，他引：1
为了了解灌丛对沙地土壤结皮的影响及其作用机制, 2006—2007年在科尔沁沙地调查了灌丛群落土壤结皮的发育特征, 并进行了田间模拟降尘、添加凋落物和结皮生物接种的试验。结果如下:①大气降尘、凋落物和微生物接种均可明显促进沙地土壤结皮的形成;②湿润、遮荫环境要比干旱、光照环境更有利于沙地土壤结皮的形成,但土壤结皮形成和发育对水分的敏感程度要大于对光照的敏感程度;③灌丛的存在对于流动沙地土壤结皮的形成发育具有明显的促进作用,沙地栽植灌木后通常会产生肥岛效应,在冠层下逐步形成结皮,并由灌丛内向外扩散;④灌丛促进沙地土壤结皮发育的主要机制是灌丛具有降风滞尘、拦截凋落物、遮荫保湿的功能,能使土壤黏粉粒、有机质、土壤养分和水分含量明显增加,为结皮的形成发育创造了良好物质条件和环境条件。 相似文献
8.
北京地区农田氮素养分随地表径流流失机理 总被引：74，自引：1，他引：74
田间模拟降雨径流试验研究了北京地区农田暴雨径流氮素流失与雨强、作物覆盖、施肥因子的关系，以及侵蚀泥沙的粒径分布特征和对氮的富集作用。结果表明：（1）降雨强度越大，地表径流模数和侵蚀模数增大，氮素流失越多；作物覆盖有效地减少地表水土和颗粒态氮流失；（2）颗粒态氮浓度占径流全氮浓度的88.9%(施尿素）和98％以上（未施氮肥），是农田径流氮损失的主要形态；（3）施用化学氮肥增大了农田径流溶解态氮浓度，化学氮肥容易通过地表径流流失；（4）侵蚀泥沙的团聚体组成和原来土壤有很大差异，粒径＜0.25mm的团聚体，尤其是含氮量较高的＜0.045mm团聚体的富集是侵蚀泥沙富集氮的主要原因。减少地表径流和土壤侵蚀，降低表土速效氮含量是减少农田地表径流氮养分流失的关键。 相似文献
9.
固沙植被区两类结皮斑块土壤呼吸对降雨脉冲的响应 总被引：2，自引：1，他引：1
与降水事件密切相关的土壤水分有效性是荒漠生态系统土壤呼吸的重要驱动因子。研究了固沙植被区以藓类和藻类为主的生物土壤结皮斑块土壤呼吸对模拟降雨(5、10、20 mm)的响应。结果表明:3种降雨量对不同结皮斑块土壤呼吸均有显著的激发作用, 但2种土壤的响应特征不同。藓类结皮斑块土壤呼吸速率在降雨后0.5 h达到最大值, 而藻类结皮斑块土壤在降雨后2 h达到最大值, 其呼吸速率分别是降雨前土壤呼吸速率的43~58、21~25倍,随后, 两类结皮斑块土壤呼吸速率逐渐下降并恢复到降雨前水平。随着降雨量的增加, 藓类结皮斑块土壤最大呼吸速率和平均呼吸速率显著增大, 而藻类结皮斑块土壤则无明显变化; 2种土壤碳释放量均随着降雨量的增大而增加。在相同降雨条件下, 藓类结皮斑块土壤呼吸速率峰值和平均值及碳释放量均显著大于藻类结皮斑块土壤。表明生物土壤结皮和降雨量均对荒漠生态系统土壤呼吸起着重要的调控作用。 相似文献
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粤北石漠化灌丛坡地模拟降雨地表径流水中钙离子含量变化 总被引：4，自引：1，他引：3
通过模拟降雨试验,研究粤北地区不同石漠化程度的灌丛坡地地表径流水中钙离子含量的变化。结果表明,在不同雨强下,不同石漠化灌丛坡地地表径流量、地表径流水钙离子浓度和地表径流水钙离子总量随石漠化程度的加重呈逐渐上升后又降低的倒“U”型趋势;在同一雨强下,潜在、轻度和极重度石漠化坡地径流水钙离子流失量远低于中度和重度石漠化坡地;地表水中的钙离子流失总量和地表径流量、土层厚度、岩石裸露率均有较高的相关性,其中与地表径流量达到显著性相关。 相似文献
11.
Modelling runoff and erosion for a semi-arid catchment using a multi-scale approach based on hydrological connectivity 总被引：1，自引：0，他引：1
Runoff and erosion processes are often non-linear and scale dependent, which complicate runoff and erosion modelling at the catchment scale. One of the reasons for scale dependency is the influence of sinks, i.e. areas of infiltration and sedimentation, which lower hydrological connectivity and decrease the area-specific runoff and sediment yield. The objective of our study was to model runoff and erosion for a semi-arid catchment using a multi-scale approach based on hydrological connectivity. We simulated runoff and sediment dynamics at the catchment scale with the LAPSUS model and included plot and hillslope scale features that influenced hydrological connectivity. The semi-arid Carcavo catchment in Southeast Spain was selected as the study area, where vegetation patches and agricultural terraces are the relevant sinks at the plot and hillslope scales, respectively. We elaborated the infiltration module to integrate these runoff sinks, by adapting the parameters runoff threshold and runoff coefficient, which were derived from a rainfall simulation database. The results showed that the spatial distribution of vegetation patches and agricultural terraces largely determined hydrological connectivity at the catchment scale. Runoff and sediment yield for the scenario without agricultural terraces were, respectively, a factor four and nine higher compared to the current situation. Distributed hydrological and erosion models should therefore take account of relevant sinks at finer scales in order to correctly simulate runoff and erosion-sedimentation patterns. 相似文献
12.
We review the current state of research on vegetation heterogeneity in the Monte Desert at scales varying from landscape to intra-patch. Different factors are related to vegetation heterogeneity at every scale. At a coarse scale (i.e. landscapes and communities) vegetation heterogeneity is commonly determined by abiotic factors, whereas biotic interactions usually influence fine scale (patch, intrapatch) heterogeneity. Communities are distributed at the landscape scale according to differences in precipitation, topography and soil attributes. On the other hand, there is evidence that the spatial pattern of plant patches within communities is determined by runon –runoff processes, although biotic influences such as grazing can induce changes in the spatial pattern of patches when plant cover is strongly reduced. In the same way, at patch and intrapatch scales, biotic interactions (i.e. plant –plant interactions, grazing) determine the size and the species composition of plant patches as well as the distribution of species inside plant patches. However, the mechanisms operating behind such biotic interactions at small scales are commonly related to plant-induced changes in the physical environment. We also found evidence of cross-scale interactions, feedbacks, and non-linear effects such as those induced by grazing disturbance. Our analysis showed some regional differences in patterns and processes related to vegetation heterogeneity along the Monte Desert which can be ascribed to climatic and taxonomic variation among areas. Although information about vegetation heterogeneity and its causes and consequences in the Monte Desert is abundant, some areas where knowledge is scarce are detailed. 相似文献
13.
The natural landscapes of semiarid areas worldwide comprise a series of scattered patches of shrubs within a matrix of biologically crusted soils (BSC). As BSCs are considered ecosystem engineers the relationships between the BSC and the shrub patches determine system functioning. The objective of our study was to investigate long-term effects of agricultural practices on biological soil crusts and their influence on hydrological aspects of a semiarid ecosystem. During 1991, we experimentally simulated five of the area's agricultural practices; 1) Scraping – the topsoil was removed to a depth of 2 cm, 2) Spraying – phototrophic organisms were chemically killed with herbicide, 3) Mowing – perennial vegetation was cut and spread to simulate grazing practices, 4) Car track – a heavy roller was used to simulate car-tracks, 5) Control – undisturbed natural plots. Sixteen years later, in 2007, these agricultural practices were found to have a long-term effect on the crusted soil surface and the related soil-surface properties. Mowing and car-track treatments led to decreased overland runoff and increased hydraulic conductivity, whereas scraping and spraying treatments led to increased overland runoff production and decreased hydraulic conductivity. We conclude that the practices had a long-term residual impact on BSC succession and related soil surface properties, which affected the hydrological processes and system functioning. 相似文献
14.
Hydrological responses and soil erosion potential of abandoned cropland in the Loess Plateau, China 总被引：17，自引：0，他引：17
Recent changes in hydrological processes and soil erosion in the Loess Plateau, China, are immediate responses to cropland abandonment for revegetation, which lead to a long-term decrease in runoff generation and soil erosion. However, detailed hydrological responses and soil erosion changes have not been clearly evaluated. In this study, two issues were focused on the plot scale. The first issue relates to changes in vegetation cover and soil properties during the early stages of revegetation. Given the occurrence of soil compaction, it was hypothesized that runoff increased during this period and the soil erosion did not significantly decline, even though vegetation increased. The second issue is the effect of scale on runoff and soil erosion. Three plot groups of three vegetation types and two restoration stages were established for comparative experiments. The results from these experiments confirmed that the soil compaction occurred during revegetation in this region. Greater runoff was produced in plot group that experienced both a longer restoration time and with higher vegetation cover (such as Groups 2 and 3 in this study) than that with a shorter restoration time and lower vegetation cover (Group 1). In addition, the total soil loss rates of all plot groups were rather low and did not significantly differ from each other. This indicates that a reduction in runoff generation and soil erosion, as a result of revegetation, was limited in the early stages of restoration following the cropland abandonment. With increasing plot area, the runoff coefficient decreased for the plot group with a longer revegetation time (Groups 2 and 3), but gently increased for the one with a shorter restoration time (Group 1). In Groups 2 and 3, soil loss rate decreased when plot area enlarged. In Group 1, it decreased before a plot area threshold of 18 m2 was exceeded. However, the increase occurred when plot area crossed the threshold value. In conclusion, the high vegetation cover alone did not lead to reduction in the runoff coefficient during the early stages of revegetation. When evaluating hydrological and soil erosion responses to revegetation, the soil compaction processes should be considered. Additionally, the effect of scale on runoff and soil erosion was found to be dependent on restoration extent, and thus on restoration time. 相似文献
15.
The typical patchy structure of dryland vegetation is a result of soil–plant feedbacks occurring in water-limited areas. The resilience of dryland ecosystems depends largely on the persistence of fertility islands associated with vegetated patches, which determines the efficiency of the vegetation regarding recolonising the gaps that result from disturbances. In this study, we investigated the mechanisms underlying soil–plant interactions throughout the process of the growth and senescence of alpha grass (Macrochloa tenacissima) and the subsequent disintegration of islands of fertility and microtopography formed during the process at two nearby alpha grass communities exhibiting different degrees of development. The life cycle of alpha grass and the rise and disintegration of the underlying microrelief were accompanied by feedback changes in the content of soil C fractions presenting different times of cycling and incorporation to the soil, the collection of particles from splash erosion, redistribution phenomena related to particles of different sizes, and erosion of the most easily erodible materials. Despite their ecological and geographical proximity, the study sites differ with respect to the persistence, after plant death, of fertility islands, which almost disappear in one case, while they remain in the other, constituting a resource for the growth of new plants and resulting in greater development and resilience in the community. A subtle erodibility threshold emerges as a cause of the considerable differences in vegetation between the two sites. 相似文献
16.
A long-term drought has led to the mass mortality of shrubs in the semi-arid Israeli Negev.The most impacted shrub species is the Noaea mucronata (Forssk.) Asch.and Schweinf.In a four-year study,we found that herbaceous vegetation growth was greater in the dead shrub patches than in the surrounding inter-patch biocrusted spaces,suggesting that the dead shrub patches encompass improved micro-habitats.However,unexpectedly,the soil moisture in the dead shrub patches was consistently lower than that of the inter-patch biocrusted spaces.At the same time,soil quality in the dead shrub patches was higher than that in the inter-patch spaces.Therefore,it seems that the overall better soil conditions in the dead patches overcome the scarcity of soil-water,supporting increased herbaceous produc-tivity.For explaining the discrepancy between herbaceous vegetation and soil-water,we formulated a conceptual framework,which highlights the key factors that regulate soil-water dynamics in this dryland ecosystem.We demonstrate that herbaceous vegetation is facilitated in the dead shrub patches by a legacy effect that takes place long after the shrubs have died.The dead shrub patches encompass a unique form of ecosystem engineering.The study high-lights the complex and unpredicted impacts of prolonged droughts on dryland ecosystems. 相似文献
17.
The effects of vegetation on runoff and soil loss: Multidimensional structure analysis and scale characteristics 总被引：5，自引：0，他引：5
This review summarizes the effects of vegetation on runoff and soil loss in three dimensions: vertical vegetation structures (aboveground vegetation cover, surface litter layer and underground roots), plant diversity, vegetation patterns and their scale characteristics. Quantitative relationships between vegetation factors with runoff and soil loss are described. A framework for describing relationships involving vegetation, erosion and scale is proposed. The relative importance of each vegetation dimension for various erosion processes changes across scales. With the development of erosion features (i.e., splash, interrill, rill and gully), the main factor of vertical vegetation structures in controlling runoff and soil loss changes from aboveground biomass to roots. Plant diversity levels are correlated with vertical vegetation structures and play a key role at small scales, while vegetation patterns also maintain a critical function across scales (i.e., patch, slope, catchment and basin/region). Several topics for future study are proposed in this review, such as to determine efficient vegetation architectures for ecological restoration, to consider the dynamics of vegetation patterns, and to identify the interactions involving the three dimensions of vegetation. 相似文献
18.
This review summarizes the effects of vegetation on runoff and soil loss in three dimensions: vertical vegetation structures(aboveground vegetation cover, surface litter layer and underground roots), plant diversity, vegetation patterns and their scale characteristics. Quantitative relationships between vegetation factors with runoff and soil loss are described. A framework for describing relationships involving vegetation, erosion and scale is proposed. The relative importance of each vegetation dimension for various erosion processes changes across scales. With the development of erosion features(i.e., splash, interrill, rill and gully), the main factor of vertical vegetation structures in controlling runoff and soil loss changes from aboveground biomass to roots. Plant diversity levels are correlated with vertical vegetation structures and play a key role at small scales, while vegetation patterns also maintain a critical function across scales(i.e., patch, slope, catchment and basin/region). Several topics for future study are proposed in this review, such as to determine efficient vegetation architectures for ecological restoration, to consider the dynamics of vegetation patterns, and to identify the interactions involving the three dimensions of vegetation. 相似文献
19.
基于甘肃省清水县汤峪河径流小区2015—2017年的观测数据,研究不同植被恢复模式条件下坡面次降雨入渗、产流产沙特征。结果表明：不同植被恢复模式条件下的土壤入渗量与降雨强度呈二次函数关系,存在入渗量达到最大值的临界降雨强度。入渗速率与降雨历时可以用幂函数关系表达,符合考斯恰可夫入渗模型。不同植被恢复模式条件下的产流率在0.003 3~0.003 6 mm·min-1之间,相对裸地的减流率为54%~58%。产流率与降雨强度之间呈二次函数关系（R2>0.88）,产流率的主要影响因素是降雨强度。径流含沙量平均值乔灌混合区（3.13 g·L-1）>灌木林（2.95 g·L-1）>乔木林（2.79 g·L-1）>草地（2.58 g·L-1）,径流含沙量与降雨强度呈线性递增函数关系。裸地的产沙量显著高于各植被小区（P<0.05）,是各植被小区的43~57倍,各植被小区的减沙率在93%~94%之间,减沙效益高于其减流效益。各植被坡面土壤流失量与降雨侵蚀力呈线性递增函数关系;产流率与侵蚀产沙率之间呈极显著正相关关系（P<0.01）,二者间可采用二次函数关系表达。本研究成果可为黄土高原丘陵沟壑区水土保持优化配置提供理论依据。 相似文献