Grazing intensity in subarctic tundra affects the temperature adaptation of soil microbial communities

Grazing by large ungulates, such as reindeer (Rangifer tarandus L.), in subarctic tundra exerts a considerable effect on the soil microclimate. Because of higher insulation by the aboveground vegetation in light versus heavily grazed areas, soil temperatures during the growing season are considerably higher under heavy grazing. Here, we hypothesized that these grazer-induced changes in soil microclimate affect the temperature sensitivity of soil microbial activity. To test this hypothesis, we conducted soil incubations at different temperatures (4 °C, 9 °C and 14 °C) for six weeks using soils from sites with contrasting long-term grazing intensities. Microbial respiration at low temperature (4 °C) was significantly higher in soils under light grazing than in soils under heavy grazing; however, grazing intensity did not affect respiration rates at 9 °C and 14 °C. In soils under light grazing, post-incubation β-glucosidase (BG) activity at 4 °C was higher in soils that had been incubated at 4 °C than in soils incubated at 14 °C, suggesting functional adaptation of the soil microbial community to low temperature. Similar adaptation was not detected in soils under heavy grazing. Ion Torrent sequencing of bacterial 16S rRNA genes showed major differences in the bacterial community composition in soils incubated at different temperatures. Overall, our results indicate that tundra soil microorganisms may be more cold-adapted under low than high grazing intensity. Due to this difference in temperature adaptation, the consequences of climate warming on soil microbial processes may be dependent on the grazing intensity.     

Soil organic‐C accumulation and N availability under improved pastures established in Mediterranean oak woodlands

Long‐term effects of improved pasture establishment (with high proportion of legumes) on soil organic‐C status and N availability in Mediterranean cork oak (Quercus suber L.) woodlands were assessed. Soils were sampled beneath scattered crowns and in open areas, considering two systems: unmanaged and managed woodlands where improved pastures were installed 26 and 32 years ago. Total and labile C and N pools were measured and C and N mineralization were determined over 24 weeks laboratory incubation. Soils under improved pastures showed higher organic‐C, total‐N and net N mineralization than those under unmanaged pasture, mainly when established beneath trees. Potentially mineralizable C, C mineralization rate and microbial C were not statistically different between the unmanaged and improved pasture sites, but were higher closer to the tree than in the open area (1.8, 1.2 and 1.2 times, respectively). The qCO₂ was higher in improved pastures (1.7 times). Labile pool of C and N extracted with hot water increased under improved pasture (3.4 and 1.7 times, respectively). Results indicate that soil quality amelioration by improved pastures is stronger in the presence of oak trees. Management systems that favour oak tree maintenance and regeneration should be taken into account to reverse soil degradation.     

Biocrusts modulate warming and rainfall exclusion effects on soil respiration in a semi-arid grassland

Soil surface communities composed of cyanobacteria, algae, mosses, liverworts, fungi, bacteria and lichens (biocrusts) largely affect soil respiration in dryland ecosystems. Climate change is expected to have large effects on biocrusts and associated ecosystem processes. However, few studies so far have experimentally assessed how expected changes in temperature and rainfall will affect soil respiration in biocrust-dominated ecosystems. We evaluated the impacts of biocrust development, increased air temperature and decreased precipitation on soil respiration dynamics during dry (2009) and wet (2010) years, and investigated the relative importance of soil temperature and moisture as environmental drivers of soil respiration, in a semiarid grassland from central Spain. Soil respiration rates were significantly lower in the dry than in the wet year, regardless of biocrust cover. Warming increased soil respiration rates, but this response was only significant in biocrust-dominated areas (>50% biocrust cover). Warming also increased the temperature sensitivity (Q₁₀ values) of soil respiration in biocrust-dominated areas, particularly during the wet year. The combination of warming and rainfall exclusion had similar effects in low biocrust cover areas. Our results highlight the importance of biocrusts as a modulator of soil respiration responses to both warming and rainfall exclusion, and indicate that they must be explicitly considered when evaluating soil respiration responses to climate change in drylands.     

Oribatid communities (Acari: Oribatida) inhabiting saxicolous mosses and lichens in the Krkonoše Mts. (Czech Republic)

Composition, structure and diversity of oribatid communities inhabiting saxicolous mosses and lichens were studied in the Krkonoše Mts. (Czech Republic) along an altitudinal gradient reaching from submontane to alpine belt. Samples of various saxicolous mosses and lichens from 197 stands were collected. Impact of altitude and dominant moss or lichen species on community structure were analysed. Data were evaluated using divisive cluster analysis and direct ordination analysis. Altogether 104 oribatid species were recorded. Four groups of saxicolous habitats, which differ in the composition of their oribatid communities, were distinguished:1. Mosses below the upper forest line with accessory higher plants growing on their surface. Higher plants indicate favourable moisture conditions and an appreciable degree of humus layer development. Their oribatid mite community is rich in number of frequent species and consists of ubiquitous species, ubiquitous species with higher requirements for moisture and amount of decaying organic matter, a high number of soil dwelling species and several hygrophilous species.2. Mosses below the upper forest line without accessory higher plants. They predominantly include mosses with no or only a weakly developed humus layer. Their oribatid mite community is composed mainly of ubiquitous species and a few soil dwelling species.3. Mosses in open areas above the upper forest line. Their humus layer is not developed at all or only weakly. Humidity and temperature fluctuations are here much higher compared with mosses below the upper forest line, which are protected by the specific forest microclimate. Their oribatid mite community is poor in number of frequent and dominant species and consists predominantly of Oribatula cf. pallida and two specialised species living exclusively in mosses and lichens (Mycobates tridactylus and Trichoribates monticola).4. Saxicolous lichens. Their oribatid community comprises ubiquitous species, species frequent both in mosses and lichens and several species with a strong affinity to lichens (Mycobates carli and five species of the genus Carabodes).     

Plant-pollinator biodiversity and pollination services in a complex Mediterranean landscape

Mediterranean landscapes comprise a complex mosaic of different habitats that vary in the diversity of their floral communities, pollinator communities and pollination services. Using the Greek Island of Lesvos as a model system, we assess the biodiversity value of six common habitats and measure ecosystemic ‘health’ using pollen grain deposition in three core flowering plants as a measure of pollination services. Three fire-driven habitats were assessed: freshly burnt areas, fully regenerated pine forests and intermediate age scrub; in addition we examined oak woodlands, actively managed olive groves and groves that had been abandoned from agriculture. Oak woodlands, pine forests and managed olive groves had the highest diversity of bees. The habitat characteristics responsible for structuring bee communities were: floral diversity, floral abundance, nectar energy availability and the variety of nectar resources present. Pollination services in two of our plant species, which were pollinated by a limited sub-set of the pollinator community, indicated that pollination levels were highest in the burnt and mature pine habitats. The third species, which was open to all flower visitors, indicated that oak woodlands had the highest levels of pollination from generalist species. Pollination was always more effective in managed olive groves than in abandoned groves. However, the two most common species of bee, the honeybee and a bumblebee, were not the primary pollinators within these habitats. We conclude that the three habitats of greatest overall value for plant-pollinator communities and provision of the healthiest pollination services are pine forests, oak woodland and managed olive groves. We indicate how the highest value habitats may be maintained in a complex landscape to safeguard and enhance pollination function within these habitats and potentially in adjoining agricultural areas.     

Potential mechanisms of soil nitrogen content heterogeneity associated with biocrust development in drylands

Biological soil crusts (biocrusts) are complex communities of micro- and macro-organisms dwelling at the soil surface in dryland regions worldwide, which contribute to important ecological functions in these areas. Biocrusts may reach different developmental stages, associated to autogenic succession of specific phototrophic organisms. However, notwithstanding the large amount of existing literature, little is known regarding the relationship between biocrust stages of development and soil nutrient dynamics. In this opinion paper, we specifically focused on soil nitrogen, and compared the total nitrogen content and potential nitrogenase activity of different developmental types of biocrust (-covered) soils. Based on published reports, we looked at a possible relationship between nitrogen content at the soil surface and biocrust development, discussing the potential mechanisms leading to the observed soil nitrogen content heterogeneity. The results showed that a higher nitrogen content remained associated to the presence of moss-dominated biocrusts, and this biocrust morphotype was characterized by a lower potential nitrogenase activity compared to the cyanobacteria- and/or lichen-dominated biocrusts. We hypothesized that these seemingly contradictory findings might be attributed to three potential mechanisms: nitrogen inheritance, nutrient retention and nutrient transfer, which we hereby examined one by one. Altogether, our opinion supports the theory of biocrust succession from incipient cyanobacteria-dominated stages to more ‘mature’ stages dominated by mosses. We stress how the heterogeneous distribution of soil nitrogen, which is closely related with biocrust development and community types, eventually affects regional and even global nitrogen dynamic and storage.     

Effect of land use on forest floor and soil of a Quercus suber L. forest in Gallura (Sardinia,Italy)

In order to determine the effect of land use on forest floor and soil, two adjacent sites with different land use were investigated in Gallura (northern Sardinia, Italy). One site is a Quercus suber L. forest mainly used for cork production and the other is an open Quercus suber L. forest where livestock is put out to graze. In each site one soil profile was studied to characterize the mineral soil, and five humus profiles were opened along a vegetation transect, were studied to characterize the forest floor. Samples of L, F and H horizons of the forest floor and of the A mineral horizons were collected and analysed for each profile. In the site mainly used for cork production well‐developed ectorganic (L, F and H) horizons are always present, with a total thickness ranging from 5·2 to 9·5 cm. Humus profile is of the Moder type, while mineral soils have an A–C profile, generally 50 cm deep. Organic matter content in the forest floor ranges from 1·76–3·72 kg m⁻² and nutrients content in the mineral soil is high. In the site used chiefly for grazing the ectorganic horizons are very poorly developed, with a total thickness ranging from 1–3 cm, except for some islands under the Quercus suber L. canopy where the total thickness may reach 5·3 cm. Humus profile is of the Mull type, but the used classification system seems not appropriate when the tree density is below a critical limit. Mineral soils have an A–C profile 20–25 cm deep. The organic matter content in the forest floor ranges from 0·45 to 1·84 kg m⁻², while nutrient content in the mineral soil maintains at high level, even higher than in the former case for C, N and Ca, probably in relation with higher supply of cattle excreta. Sheet erosion is evident in the site. It is concluded that cork production will maintain a sustainable forest floor development in cork–oak forest ecosystem, whereas cattle grazing, fires and ploughing in cork–oak forests may be considered to trigger off severe soil degradation processes. Copyright © 2000 John Wiley & Sons, Ltd.     

放牧对植物群落特征和土壤微生物及酶活性的影响

[目的]探讨放牧对羊草群落和贝加尔针茅群落的影响,为草原土壤的保护和草原自然保护区建设提供科学依据。[方法]以呼伦贝尔草甸草原为样地,采用野外调查和实验室分析相结合的方法。[结果]在放牧干扰下,以羊草为建群种的群落所受的影响比贝加尔针茅群落小,植物群落盖度、高度和Simpson指数明显高于贝加尔针茅群,物种多样性更丰富,生长情况相对更好。羊草草原土壤全氮、全磷和有机质含量高于贝加尔针茅草原土壤。各放牧区土壤微生物数量均表现为:细菌放线菌真菌;垂直分布为0—10cm10—20cm;土壤脲酶、过氧化氢酶、转化酶活性、全N,全P和有机质等0—10cm土层的均高于10—20cm。相关分析表明,植物群落α多样性与土壤微生物数量、土壤酶活性、全N,全P和有机质等呈显著正相关。[结论]适度放牧有助于提高草甸草原羊草群落和贝加尔针茅群落α多样性、土壤微生物数量和土壤酶活性。两个群落相比较,羊草群落更适合放牧。     

栓皮栎林分枯落物对土壤-植物系统水分运动的影响

[目的]分析枯落物层对森林生态系统水分循环的作用。[方法]利用稳定同位素技术,测定了在旱季和雨季栓皮栎木质部水分以及枯落物层和不同土壤层水分的同位素特征。通过对比不同环境条件下(干旱期和降雨前后)枯落物层和土壤水分同位素组成的变化,并根据其与植物茎水分同位素特征的差异判断栓皮栎不同季节的水分利用来源。[结果]在旱季,随着干旱期的进行,对于平均枯落物层厚度,表层0—30cm土壤水分同位素特征由于蒸发分馏的影响逐渐变得富集,而对于因为特殊地形而造成的未分解枯落物层较厚的地方,则土壤水分同位素特征随着干旱期的进行几乎不发生变化;栓皮栎的水分来源主要集中在表层,随着干旱期的延长没有发生变化;在雨季,极端降雨后,土壤同位素特征表明枯落物截留降雨的效应明显,被枯落物截留的雨水以活塞流的形式继续向土壤入渗,栓皮栎的水分来源主要来自于表层0—10cm枯落物层(分解层)的土壤;土壤剖面水分同位素特征呈现的梯度变化与土壤层的结构有关。[结论]枯落物层的厚度,特别是未分解层,对土壤水分的同位素特征影响有差异;枯落物层的水文效应也间接改变了植物的水分利用。     

Differential effects of lichens and mosses on soil enzyme activity and litter decomposition

In the New Jersey Pinelands, canopy gaps in the pine-dominated forest support patches of lichens, mosses, and caespitose grasses. We tested the hypotheses that non-vascular plants and lichens can affect nutrient cycling processes and that mosses and lichens would differ from each other. We predicted that (1) lichen tissues would decompose more slowly than pine or moss tissues, (2) all plant materials would decompose more slowly beneath lichens than beneath mosses, and (3) soil enzyme activities would be higher under lichens than under mosses or grasses, reflecting greater nutrient limitation. We compared rates of decomposition of the litter of Pinus rigida and moss and lichen tissues, and measured soil enzyme activities responsible for nutrient mineralization from litter (acid and alkaline phosphatases, chitinase, β-glucosidase, aminopeptidase, and phenol oxidase) under three types of groundcover (lichens, mosses, and grasses) and unvegetated soil at two sites. While groundcover affected enzyme activities, the patterns of enzyme activities differed markedly between the two sites. In general, the enzyme activities were uniformly low. Decomposition rates were more strongly affected by the groundcover than by litter materials. While all litters tended to decompose more slowly under lichens than under mosses, supporting one of our initial hypotheses, the rates of decomposition were markedly different between the two sites. These results suggest that while mosses and lichens create patches of different soil function in both sites, the differences between the sites in unknown factors cause the enzyme activities and decomposition rates to differ.     

严重侵蚀红壤封禁管理马尾松林水源涵养功能的恢复研究

对严重侵蚀红壤封禁管理马尾松林的水源涵养功能进行了研究 ,结果表明 :封禁管理后的马尾松林总持水量为 1717 872t/hm2 ,比对照的大 2 19 112t/hm2 ,其中地上部分持水量为 2 4 72 2t/hm2 ,是对照的 2 7 2倍 ,土壤 0～ 40cm土层最大持水量为 1693 15t/hm2 ,比对照的高 196 2 1t/hm2 ;表土层的初渗率和稳渗率均比对照的高。说明封禁管理治理模式马尾松林的水源涵养功能已有一定程度恢复     

Using Static and Dynamic Indicators to Evaluate Soil Physical Quality in a Sicilian Area

Both capacitive indicators derived from the water retention curve and dynamic measurements of the flow‐weighted mean pore radius, R₀, were used to assess the soil physical quality of two agricultural areas (cropland and olive orchard) and two natural areas (grassland and managed woodlot plantation) potentially subject to soil degradation. The overall idea of the study was to investigate whether a dynamic indicator quantitatively derived from hydraulic conductivity measurements could be used to supplement the traditionally applied capacitive indicators retrieved from water retention measurements. According to the available criteria, only the surface layer of the cropland site showed optimal soil physical quality. In the grassland and woodlot sites, the physical quality was deteriorated also as a consequence of compaction because of grazing. Overall, the physical quality was better in tilled than nontilled soils. The optimal soil in terms of capacitive indicators had hydraulic conductivity close to saturation that was intermediate among the different land uses, and it remained 1·3–1·9 times higher than that observed in the natural sites even when the largest pores emptied. A depth effect on R₀ was observed only when larger macropores were activated. It was suggested that water transmission parameters are more affected by changes in large pore domain. The plant available water content and Dexter's S‐index showed inverse statistically significant regressions with R₀. The empirical relationships were physically convincing given that, at increasing R₀, the contribution of macropores increases, water is transmitted faster below the root zone and the soil's ability to store water is reduced. Copyright © 2013 John Wiley & Sons, Ltd.     

放牧管理对青藏高原东缘高寒草甸土壤线虫的影响及作用机制

不同强度、季节的放牧是草地生态系统中主要的放牧管理措施,在生物多样性维持以及生态过程发挥中起着重要的作用,然而,关于青藏高原东缘高寒草甸地区放牧对土壤线虫群落的研究甚少。本文调查了放牧（轻度、中度和重度）对植物群落、土壤理化性质和线虫群落的影响。结果表明：植物群落、土壤理化性质和线虫群落受到放牧、时间以及放牧和时间共同作用的影响;食细菌线虫、植物凋落物生物量、根生物量、土壤含水量、土壤有机碳含量在轻度放牧草地内最高（p＜0.05）;杂类草生物量在中度放牧草地内最高;杂食线虫数量在重度放牧地内最低（p＜0.05）。植物群落和土壤特性与土壤线虫群落有明显的相关关系（p＜0.05）。结构方程模型显示食草动物主要通过植物群落影响植食和食细菌线虫,进一步的研究应针对植物群落多样性以及个体特征对线虫群落的影响。     

4种典型荒漠草原植物群落土壤呼吸对封育禁牧的响应

采用动态密闭气室分析法,分别研究了放牧与围封条件下赖草群落、沙蒿群落、甘草群落、冰草群落4种典型荒漠草原植物群落土壤呼吸及其与温度因子的关系,揭示了4种典型荒漠草原植物群落土壤呼吸对封育禁牧的响应过程。结果表明,放牧与围封样地的土壤呼吸速率日动态均呈现出不对称的单峰型曲线,高峰值一般出现在14:00—16:00。围封样地土壤呼吸速率值大于放牧样地,但各监测时刻差异显著性不尽相同。放牧与围封样地各植物群落中较深层土温(10,15cm)和土壤呼吸速率的相关性普遍高于浅层土温(5cm)、深层土温(20cm)和气温,其中15cm土层温度与土壤呼吸速率相关性最高。除沙蒿群落外,其他3种植物群落放牧样地Q10值均显著低于围封样地,Q10值大小依次均为:沙蒿群落>赖草群落>甘草群落>冰草群落,其中沙蒿群落Q10值远高于其他3个群落。     

Soil property changes following conversion of acacia woodland into grazing and farmlands in the Rift Valley area of Ethiopia

Continued conversion of woodlands into grazing and farmland is seriously undermining the natural ecosystem of the dry and fragile Rift Valley areas of Ethiopia. This study investigated the effects of land‐use change on soil organic carbon (SOC), total nitrogen (N), pH, exchangeable bases, cation exchange capacity (CEC) and base saturation (per cent) in three adjacent land‐use types: controlled grazing, open‐grazing and farmland. A total of 81 soil samples were collected and analysed. Contents of SOC and total N decreased drastically in open‐grazing and farmland (p < 0·001), and were significantly higher in the top 0·2 m than in the subsurface soil layer. Compared with the controlled grazing, reductions in the contents of SOC and total N in the top 1 m soil layer were 22–30 and 19 per cent, respectively, due possibly to the decrease in plant biomass input into the soil and the fast decomposition of organic materials. Long‐term cultivation had significantly increased the concentration of exchangeable K. Exchangeable Na was high in the lower layers, while Mg was higher in the top surface soil. CEC also varied with soil depth (p = 0·016); it was higher in the topsoil than in the subsurface soil, which may be, among others, due to the differences in soil organic matter distribution with depth. Although these semi‐arid soils are known to have low organic carbon and CEC levels, the values from the current study area are critically low, and may indicate the further impoverishment of the soils under high agricultural and grazing pressures. Copyright © 2010 John Wiley & Sons, Ltd.     

Shifting Cyanobacterial Diversity in Response to Agricultural Soils Associated with Dust Emission

Dust emission to the atmosphere from wind‐eroded soils has many environmental impacts, including soil degradation and air pollution. Various agricultural land uses alter the topsoil properties and thus affect dust particle characteristics as well as loading of biological components into the air. In the present work, the richness and abundance of bacterial communities in topsoils of semiarid loess that are associated with dust emissions were studied by high throughput sequencing methods and were found to be affected by land uses: conventional agriculture, organic agriculture alternating with grazing, uncontrolled grazing activities and natural nondisturbed soil. Moreover, bacterial diversity was shown to be influenced by the contents of sand, CaCO₃ and particulate matter in the topsoil. Of all bacteria taxa detected, cyanobacteria were found to be most strongly influenced by land use: Natural and grazing lands were highly abundant with cyanobacterial reads (about 33%), whereas conventional agriculture lands and organic agriculture lands alternating with grazing contained only 7% cyanobacteria. When examining macro‐aggregates in two soils (natural and grazing), approximately 44% of reads were found to be affiliated to cyanobacteria, whereas in micro‐aggregates, their concentration decreased to about 11%. Intensive agricultural use leads to a reduction in soil aggregation and significantly decreases cyanobacteria abundance, in turn increasing dust emission potential and loss of topsoil materials to the atmosphere. Copyright © 2016 John Wiley & Sons, Ltd.     

Effect of fencing,artificial seeding and abandonment on vegetation composition and dynamics of ‘black soil land’ in the headwaters of the Yangtze and the Yellow Rivers of the Qinghai‐Tibetan Plateau

Rangeland management can affect plant diversity and plant functional groups of native grassland communities. To improve pasture for livestock grazing from the existing poisonous and ruderal vegetation in the ‘black soil land’ grassland in the headwaters of the Yangtze and the Yellow Rivers (HAYYR) of the Qinghai‐Tibetan Plateau, three treatments (fencing‐FT, artificial seeding with local grasses‐ST and abandonment‐AT) were applied during a 5‐year period (2000–2005). Plant diversity and groups (sedges, grasses and dwarf shrubs) in the treated plots were compared with non‐treated control plots. Results showed that (1) FT promoted an increase in forbs species, but there was no change in the other plant functional groups; (2) with ST, species richness of forbs decreased but grass species increased indicating that sowing local grasses could change plant composition of black soil land in the short‐term, and increase the proportion of grasses and, thus, forage for grazing and (3) AT, after plowing, was similar to CK plots, with forbs being the dominant plant functional group for the 5 years. In conclusion, the goal to alter black soil land cover from poisonous and ruderal plants to more useful plants for livestock grazing by either fencing, artificial seeding or abandonment was not successful in the long term. Copyright © 2008 John Wiley & Sons, Ltd.     

围栏封育对荒漠草原灌丛草地土壤优先流的影响研究

为探究围封对灌丛草地土壤优先流的影响,以宁夏吴忠市盐池县典型荒漠草原区为研究区,通过野外入渗染色试验、图像处理分析等方法,对围封荒漠草原灌丛草地土壤优先流的影响进行评价。结果表明:(1)围栏封育与放牧管理样地土壤水分入渗特征存在差异,在围栏封育样地,草地、天然柠条林地、人工柠条林地的入渗染色图像分别在0—125,0—115,0—105 cm呈现均匀分布,而在125—240,115—150,105—140 cm呈现染色分支,在放牧管理样地,草地、天然柠条林地、人工柠条林地入渗染色图像分别在0—80,0—70,0—80 cm呈现均匀分布,围栏封育导致土壤优先流发生深度更大;(2)土壤剖面染色面积比表现为围栏封育草地＞围栏封育天然柠条林地＞围栏封育人工柠条林地＞放牧管理人工柠条林地＞放牧管理天然柠条林地＞放牧管理草地,土壤染色深度表现为围栏封育草地＞围栏封育天然柠条林地＞放牧管理草地＞放牧管理天然柠条林地＞围栏封育人工柠条林地＞放牧管理人工柠条林地,围栏封育管理会导致土壤剖面染色面积比及染色深度增大;(3)土壤优先流变异系数表现为放牧管理天然柠条林地＞放牧管理人工柠条林地＞围栏封育天然柠条林地＞放牧管理草地＞围栏封育人工柠条林地＞围栏封育草地,放牧管理导致土壤优先流程度增加,而围栏封育降低灌木林地及草地的优先流程度。因此,在荒漠草原等干旱半干旱地区,围栏封育可作为提升土壤水分均匀入渗深度、降低优先流发生程度、提高土壤水分利用效率的重要管理方式。     

土壤生物结皮在干旱半干旱地区退化生态系统恢复中的作用(英文)

 土壤生物结皮是由细菌、真菌、藻类、地衣和苔藓等形成的一种混合体,作为干旱半干旱地区生态系统的组成部分,它对生态系统镶嵌格局和生态过程有不可忽视的影响;同时,土壤生物结皮通过影响局部水分条件,可以起到稳定土壤表层、减少土壤侵蚀、增加土壤氮养分的作用:因此,土壤生物结皮能够为土壤表层提供一种天然保护的作用,对干旱半干旱地区退化生态系统的恢复具有非常重要的作用。     

Heterogeneity in soil hydrological response from different land cover types in southern Spain

This paper reports results from the analysis of the soil hydrological response to simulated rainfall in a cork oak forest in Los Alcornocales Natural Park (SW Spain). Four different soil/vegetation units were selected for the field experiments: [1] cork oak woodland, [2] heathland, [3] grassland, and [4] cork oak/olive tree mixed forest. Rainfall simulations tests were performed on circular plots of 1256.6 cm² at an intensity of 56.5 mm h^− 1 for 30 min.Marked differences in the hydrological behavior of the studied vegetation types were observed after the rainfall simulations. The soils under woodland showed low runoff rates and coefficients. The highest runoff rates were measured on the heath and grass-covered parts of the hillslope. Water repellency of the soil, measured from water drop penetration tests, reduced infiltration (especially under the heathland), and seems to be the cause of fast ponding and runoff generation during the first stages of rainstorms.The mosaic of different patterns of hydrological response to rainfall, such as runoff generation or infiltration, is governed by the spatial distribution of vegetation and its influence on the soil surface.