古尔班通古特沙漠不同类型生物结皮对草本植物多样性影响

选择古尔班通古特沙漠的北部(一号点)、中部(二号点)、南部(三号点)3个不同样点的裸沙和藻结皮、地衣结皮与苔藓结皮3种生物结皮类型,对比研究了草本植物多样性的差异性及其主要环境影响因素.结果表明:(1)不同生物结皮类型的土壤理化性质有明显差异,土壤有机质、全氮、全磷、全钾含量以及黏粒、粉粒和细沙的含量随生物结皮演替显著...     

Responses of microbial activities and soil physical-chemical properties to the successional process of biological soil crusts in the Gurbantunggut Desert,Xinjiang

Biological soil crusts(BSCs) are capable of modifying nutrient availability to favor the establishment of biogeochemical cycles. Microbial activities serve as critical roles for both carbon and nutrient transformation in BSCs. However, little is known about microbial activities and physical-chemical properties of BSCs in the Gurbantunggut Desert, Xinjiang, China. In the present research, a sampling line with 1-m wide and 20-m long was set up in each of five typical interdune areas selected randomly in the Gurbantunggut Desert. Within each sampling line, samples of bare sand sheet, algal crusts, lichen crusts and moss crusts were randomly collected at the depth of 0–2 cm. Variations of microalgal biomass, microbial biomass, enzyme activities and soil physical-chemical properties in different succession of BSCs were analyzed. The relationships between microalgal biomass, microbial biomass, enzymatic activities and soil physical-chemical properties were explored by stepwise regression. Our results indicate that microalgal biomass, microbial biomass and most of enzyme activities increased as the BSCs developed and their highest values occurred in lichen or moss crusts. Except for total K, the contents of most soil nutrients(organic C, total N, total P, available N, available P and available K) were the lowest in the bare sand sheet and significantly increased with the BSCs development, reaching their highest values in moss crusts. However, pH values significantly decreased as the BSCs developed. Significant and positive correlations were observed between chlorophyll a and microbial biomass C. Total P and N were positively associated with chlorophyll a and microbial biomass C, whereas there was a significant and negative correlation between microbial biomass and available P. The growth of cyanobacteria and microorganism contributed C and N in the soil, which offered substrates for enzyme activities thus increasing enzyme activities. Probably, improvement in enzyme activities increased soil fertility and promoted the growth of cyanobacteria, eukaryotic algae and heterotrophic microorganism, with the accelerating succession of BSCs. The present research found that microalgal-microbial biomass and enzyme activities played important roles on the contents of nutrients in the successional stages of BSCs and helped us to understand developmental mechanism in the succession of BSCs.     

古尔班通古特沙漠地衣结皮对放牧踩踏干扰的小尺度响应

古尔班通古特沙漠地衣结皮对放牧踩踏干扰及其所引起的生境异质性具有重要的指示作用。研究表明：① 放牧踩踏干扰主要集中于结皮层（0~5 cm）,随机调查的样方中,90%的样方干扰率均低于30%,生物土壤结皮(BSCs)破损尚处于较安全的范围;② 放牧踩踏干扰降低了BSCs总盖度,不同类型的结皮对践踏干扰的反应具差异性,其中,真菌-藻类共生形成的地衣结皮与干扰率呈极显著负相关（P<0.01）,干扰率>30%的样方中,抗风蚀能力较强的苔藓结皮、地衣结皮盖度均显著低于未受干扰样方,地衣共生体的破坏导致真菌数量显著增加（P<0.05）;③ 有机质、土壤容重等土壤理化指标均与干扰率呈负相关,干扰率>30%的样方中各指标均低于未受干扰样方。其中,土壤容重是对放牧干扰比较敏感的指标,与地衣结皮盖度亦呈极显著正相关（P<0.01）,与流沙盖度呈显著负相关（P<0.05）。     

Carbon fixation and influencing factors of biological soil crusts in a revegetated area of the Tengger Desert,northern China

Biological soil crusts （BSCs） are an important type of land cover in arid desert landscapes and play an important role in the carbon source-sink exchange within a desert system. In this study, two typical BSCs, moss crusts and algae crusts, were selected from a revegetated sandy area of the Tengger Desert in northern China, and the experiment was carried out over a 3-year period from January 2010 to November 2012. We obtained the effec- tive active wetting time to maintain the physiological activity of BSCs basing on continuous field measurements and previous laboratory studies on BSCs photosynthesis and respiration rates. And then we developed a BSCs carbon fixation model that is driven by soil moisture. The results indicated that moss crusts and algae crusts had significant effects on soil moisture and temperature dynamics by decreasing rainfall infiltration. The mean carbon fixation rates of moss and algae crusts were 0.21 and 0.13 g C/（m2.d）, respectively. The annual carbon fixations of moss crusts and algae crusts were 64.9 and 38.6 g C/（m2.a）, respectively, and the carbon fixation of non-rainfall water reached 11.6 g C/（m2.a） （30.2% of the total） and 8.8 g C/（m2.a） （43.6% of the total）, respectively. Finally, the model was tested and verified with continuous field observations. The data of the modeled and measured CO2 fluxes matched notably well. In desert regions, the carbon fixation is higher with high-frequency rainfall even the total amount of seasonal rainfall was the same.     

Species composition, distribution patterns and ecological functions of biological soil crusts in the Gurbantunggut Desert

As one of the most important biological factors that maintain the stability of the largest fixed and semi-fixed desert in China,the Gurbantunggut Desert,the biological soil crusts (BSCs) develop well and play critical ecological roles in the desert ecosystem. In this paper,we briefly summarize our research findings since 2002 including species composition,distribution pattern and ecological functions of BSCs in the desert. Our results indicate abundant species diversity of BSCs in the Gurbantunggut Desert in comparison to other deserts in China. At the scales of sand dune or whole desert,the distribution patterns of BSCs are location-specific. The existence of BSCs in this desert could:(1) accelerate the formation of desert soil and the weathering of minerals; (2) accumulate organic matter in surface soil through related species in soil crusts; (3) enhance the abilities of sand surface to resist wind erosion; (4) influence seed germination of vascular plants; and (5) enhance the production of dew deposition on sandy soil surface.     

Topographic differentiations of biological soil crusts and hydraulic properties in fixed sand dunes,Tengger Desert

Biological soil crusts(BSCs) play an important role in surface soil hydrology. Soils dominated with moss BSCs may have higher infiltration rates than those dominated with cyanobacteria or algal BSCs. However, it is unnown whether improved infiltration in moss BSCs is accompanied by an increase in soil hydraulic conductivity or water retention capacity. We investigated this question in the Tengger Desert, where a 43-year-old revegetation program has promoted the formation of two distinct types of BSCs along topographic positions, i.e. the moss-dominated BSCs on the interdune land and windward slopes of the fixed sand dunes, and the algal-dominated BSCs on the crest and leeward slopes. Soil water retention capacity and hydraulic conductivity were measured using an indoor evaporation method and a field infiltration method. And the results were fitted to the van Genuchten–Mualem model. Unsaturated hydraulic conductivities under greater water pressure(–0.01 MPa) and water retention capacities in the entire pressure head range were higher for both crust types than for bare sand. However, saturated and unsaturated hydraulic conductivities in the near-saturation range(–0.01 MPa) showed decreasing trends from bare sand to moss crusts and to algal crusts. Our data suggested that topographic differentiation of BSCs significantly affected not only soil water retention and hydraulic conductivities, but also the overall hydrology of the fixed sand dunes at a landscape scale, as seen in the reduction and spatial variability in deep soil water storage.     

黄土高原藓结皮覆盖土壤导水性能和水流特征

生物结皮具有特殊的水文物理性质,为探究其对土壤水分渗透性和水流特征的影响,以黄土高原风沙土和黄绵土上3种典型地表覆盖类型(裸地、藓结皮、藓结皮-草本植物混合)为对象,采用环刀法和染色示踪法对其导水性质与水流特征进行探究。结果表明:藓结皮对2种土壤类型0~5 cm土层土壤理化性质影响较大,与裸地相比土壤容重降低了9.85%~10.00%,土壤黏粒含量增加了1.01~1.29倍,表层有机质含量提高了2.73~3.02倍;藓结皮使0~5 cm土层土壤饱和导水率降低了61.32%~88.89%,而在5~10 cm土层饱和导水率则有明显上升。另外,由于草本植物的影响,藓结皮-草本植物0~5 cm土层与藓结皮土壤相比土壤饱和导水率提高了1.32~6.43倍;黄绵土藓结皮与藓结皮-草本植物的染色面积比均高于裸地,且水分下渗深度增加了10 cm,而风沙土藓结皮与风沙土裸地的染色面积比差异不明显。综上所述,藓结皮和藓结皮-草本植物的存在改变了表层土壤水分渗透性以及水流运动特征和水分下渗深度,影响着黄土高原土壤水分保持和生态恢复。     

Biocrust-induced partitioning of soil water between grass and shrub in a desert steppe of Northwest China

Maintaining the stability of exotic sand-binding shrub has become a large challenge in arid and semi-arid grassland ecosystems in northern China. We investigated two kinds of shrublands with different BSCs (biological soil crusts) cover in desert steppe in Northwest China to characterize the water sources of shrub (Caragana intermedia Kuang et H. C. Fu) and grass (Artemisia scoparia Waldst. et Kit.) by stable ¹⁸O isotopic. Our results showed that both shrublands were subject to persistent soil water deficiency from 2012 to 2017, the minimum soil depth with CV (coefficient of variation) <15% and SWC (soil water content) <6% was 1.4 m in shrubland with open areas lacking obvious BSC cover, and 0.8 m in shrubland covered by mature BSCs. For C. intermedia, a considerable proportion of water sources pointed to the surface soil. Water from BSCs contributed to averages 22.9% and 17.6% of the total for C. intermedia and A. scoparia, respectively. C. intermedia might use more water from BSCs in rainy season than dry season, in contrast to A. scoparia. The relationship between shrub (or grass) and soil water by δ¹⁸O shown significant differences in months, which partly verified the potential trends and relations covered by the high variability of the water source at seasonal scale. More fine roots at 0-5 cm soil layer could be found in the surface soil layer covered by BSCs (8000 cm/m³) than without BSCs (3200 cm/m³), which ensured the possibility of using the surface soil water by C. intermedia. The result implies that even under serious soil water deficiency, C. intermedia can use the surface soil water, leading to the coexistence between C. intermedia and A. scoparia. Different with the result from BSCs in desert areas, the natural withdrawal of artificial C. intermedia from desert steppe will be a long-term process, and the highly competitive relationship between shrubs and grasses also determines that its habitat will be maintained in serious drought state for a long time.     

不同沙丘部位和不同结皮类型对土壤种子库的影响

采用萌发法对古尔班通古特沙漠沙垄不同部位生物结皮类型的种子库进行研究,发现不同沙丘部位和结皮类型种子分布特征有一定的规律性:藻类结皮的种子数量、丰富度和多样性均显著高于地衣和苔藓结皮。生物结皮从藻类到地衣和苔藓的演替,有降低种子数量和种子多样性的现象。在不同沙丘部位,沙丘顶部流沙的种子数量和多样性较低,与丘顶流沙相比沙丘底部的藻类结皮显示出较高的丰富度和多样性,但沙丘底部的地衣和苔藓结皮与丘顶流沙相比未表现出明显的差异。背风坡中部的藻类结皮种子多样性较高,显著高于迎风坡中部的藻类结皮。     

Snowpack shifts cyanobacterial community in biological soil crusts

Winter snowpack is an important source of moisture that influences the development ofbiological soil crusts(BSCs)in desert ecosystems.Cyanobacteria are important photosynthetic organismsin BSCs.However,the responses of the cyanobacterial community in BSCs to snowpack,snow depth andmelting snow are still unknown.In this study,we investigated the cyanobacterial community compositionand diversity in BSCs under different snow treatments(doubled snow,ambient snow and removed snow)and three snow stages(stage 1,snowpack;stage 2,melting snow;and stage 3,melted snow)in theGurbantunggut Desert in China.In stages 1 and 2,Cyanobacteria were the dominant phylum in the bacterialcommunity in the removed snow treatment,whereas Proteobacteria and Bacteroidetes were abundant inthe bacterial communities in the ambient snow and doubled snow treatments.The relative abundances ofProteobacteria and Bacteroidetes increased with increasing snow depth.The relative abundances ofCyanobacteria and other bacterial taxa were affected mainly by soil temperature and irradiance.In stages 2and 3,the relative abundance of Cyanobacteria increased quickly due to the suitable soil moisture andirradiance conditions.Oscillatoriales,Chroococcales,Nostocales,Synechococcales and unclassifiedCyanobacteria were detected in all the snow treatments,and the most dominant taxa were Oscillatorialesand Chroococcales.Various cyanobacterial taxa showed different responses to snowpack.Soil moisture andirradiance were the two critical factors shaping the cyanobacterial community structure.The snowpackdepth and duration altered the soil surface irradiance,soil moisture and other soil properties,whichconsequently were selected for different cyanobacterial communities.Thus,local microenvironmentalfiltering(niche selection)caused by snow conditions may be a dominant process driving shifts in thecyanobacterial community in BSCs.     

生物土壤结皮结构、功能及人工恢复技术

生物土壤结皮作为典型的有机地被层,广泛分布在干旱半干旱地区.由于其具有良好的水土保持及土壤稳定等功能,可有效控制土地沙漠化,防治水土流失,因此,生物土壤结皮恢复被看作是荒漠生态系统修复和重建的关键.本文系统综述了国内外学者在生物结皮领域开展的研究工作,包括生物土壤结皮的生物组成、演替过程、生态功能、干扰响应、人工培育及...     

Effects of artificially cultivated biological soil crusts on soil nutrients and biological activities in the Loess Plateau

Biological soil crusts （BSCs） play an important role in the early succession of vegetation restoration in the Loess Plateau, China. To evaluate the effects of artificially cultivated BSCs on the soil surface micro-envir- onment, we obtained natural moss crusts and moss-lichen crusts from the Loess Plateau of Shaanxi province, and subsequently inoculated and cultivated on horizontal and sloping surfaces of loess soil in a greenhouse. The chemical and biological properties of the subsoil under cultivated BSCs were determined after 10 weeks of cul- tivation. The results indicated that BSCs coverage was more than 65% after 10 weeks of cultivation. Moss crust coverage reached 40% after 5 weeks of cultivation. Compared with the control, soil organic matter and available nitrogen contents in moss crust with the horizontal treatments increased by 100.87% and 48.23%, respectively; increased by 67.56% and 52.17% with the sloping treatments, respectively; they also increased in moss-lichen crust with horizontal and sloping treatments, but there was no significant difference. Available phosphorus in cultivated BSCs was reduced, soil pH was lower and cationic exchange capacity was higher in cultivated BSCs than in the control. Alkaline phosphatase, urease and invertase activities were increased in artificially cultivated BSCs, and alkaline phosphatase activity in all cultivated BSCs was obviously higher than that in the control. Numbers of soil bacteria, fungi and actinomycetes were increased in the formation process of cultivated BSCs. These results indicate that BSCs could be formed rapidly in short-term cultivation and improve the mi- cro-environment of soil surface, which provides a scientific reference for vegetation restoration and ecological reconstruction in the Loess Plateau. China.     

黄土高原土壤生物结皮对植物种子出苗和生长的影响

为了解生物土壤结皮对植物种子萌发出苗和植物生长的影响,于2009年7～8月在陕西省吴起县进行野外调查,对油松（Pinus tabulaeformis）、柠条（Caragana korshinskii）、沙棘（Hippophae rhamnoides）和杜梨（Pyrus betulae-folia）种子进行萌发实验,研究...     

Shrub modulates the stoichiometry of moss and soil in desert ecosystems,China

Desert mosses, which are important stabilizers in desert ecosystems, are distributed patchily under and between shrubs. Mosses differ from vascular plants in the ways they take up nutrients. Clarifying their distribution with ecological stoichiometry may be useful in explaining their mechanisms of living in different microhabitats. In this study, Syntrichia caninervis, the dominant moss species of moss crusts in the Gurbantunggut Desert, China, was selected to examine the study of stoichiometric characteristics in three microhabitats (under living shrubs, under dead shrubs and in exposed ground). The stoichiometry and enzyme activity of rhizosphere soil were analyzed. The plant function in the above-ground and below-ground parts of S. caninervis is significantly different, so the stoichiometry of the above-ground and below-ground parts might also be different. Results showed that carbon (C), nitrogen (N) and phosphorus (P) contents in the below-ground parts of S. caninervis were significantly lower than those in the above-ground parts. The highest N and P contents of the two parts were found under living shrubs and the lowest under dead shrubs. The C contents of the two parts did not differ significantly among the three microhabitats. In contrast, the ratios of C:N and C:P in the below-ground parts were higher than those in the above-ground parts in all microhabitats, with significant differences in the microhabitats of exposed ground and under living shrubs. There was an increasing trend in soil organic carbon (SOC), soil total nitrogen (STN), soil available phosphorous (SAP), and C:P and N:P ratios from exposed ground to under living shrubs and to under dead shrubs. No significant differences were found in soil total phosphorous (STP) and soil available nitrogen (SAN), or in ratios of C:N and SAN:SAP. Higher soil urease (SUE) and soil nitrate reductase (SNR) activities were found in soil under dead shrubs, while higher soil sucrase (STC) and soil β-glucosidase (SBG) activities were respectively found in exposed ground and under living shrubs. Soil alkaline phosphatase (AKP) activity reached its lowest value under dead shrubs, and there was no significant difference between the microhabitats of exposed ground and under living shrubs. Results indicated that the photosynthesis-related C of S. caninervis remained stable under the three microhabitats while N and P were mediated by the microhabitats. The growth strategy of S. caninervis varied in different microhabitats because of the different energy cycles and nutrient balances. The changes of stoichiometry in soil were not mirrored in the moss. We conclude that microhabitat could change the growth strategy of moss and nutrients cycling of moss patches.     

我国干旱沙漠地区不同类型土壤结皮的理化性质研究

本研究对我国干旱沙漠地区不同类型土壤结皮的理化性质特征进行了系统研究。研究结果表明:无论是不同地区还是同一地区不同发育程度的土壤结皮机械组成,它们的共同特征都是砂粒和粗粉粒含量相对较多,细粉粒和粘粒含量相对较少;从流沙到土壤结皮的形成过程中,粗粉粒是土壤结皮形成的关键基础。通过对同一地区不同发育程度的结皮机械组成比较说明结皮形成初期对颗粒组成有一定的要求,组成达到一定范围才能形成结皮,结皮一旦形成,随时间的增加,结皮厚度在不断增加,但质地基本不变。土壤结皮的形成过程是土壤养分和有机质不断富积的过程。各研究区的土壤结皮pH值相差不大,均在8左右,呈弱碱性;碱化度均≥5,处于碱化发育过程中。由于各地降水量和土壤母质发育的不同,不同地区以及同一地区不同发育程度的土壤结皮之间的CaCO3含量差异较大;同一地区土壤结皮的全盐量差异不大;不同地区土壤结皮的阴阳离子交换量差异较大,同一地区之间差异不大。该文对进一步研究土壤结皮的形成有一定的参考价值。     

沙漠水渠人工固沙区沙篙和沙拐枣灌丛的土壤水分特征对比

在古尔班通古特沙漠引水渠沿线建植5a的人工固沙区内,选择自然生长的沙蒿和沙拐枣灌丛,依据冠幅大小设置5个水平距离梯度和4个土层深度梯度.对比研究了二者的土壤水分特征.结果表明,随土层深度的增加,两种灌丛土壤含水量均呈增加趋.,中下部2层(20～40 cm和40～60 cm)土壤含水量显著(P<0.05)高于上部2层(0...     

土壤微生物在生物结皮形成中的作用及生态学意义

在荒漠地区的固定、半固定沙地和流动沙地上,微生物、藻类植物及地衣、苔藓植物能参与并形成生物结皮,其在干旱和半干旱荒漠地区具有重要生态意义。其中土壤微生物因其极强的适应性和生存能力,在生物结皮形成各阶段都起着积极的作用。土壤微生物的生长和活性与土壤酶活性的变化具有良好的相关性,它的组成、分布和数量因沙丘类型和沙土层深度的不同而有所变化,也受到季节和植被的影响。土壤微生物的生理代谢活动及数量变化可以改变沙土表面理化性质,在土壤结皮的形成、植物营养的转化过程中发挥积极作用,为植物生长创造了良好的条件。     

不同技术措施对梭梭免灌造林成活率的影响

分别于2009年、2010年春季,在新疆古尔班通古特沙漠南缘选取了迎风坡、丘间平地、背风坡作为研究样地,采用不同的技术措施(保水剂、生根粉和液体地膜)进行梭梭免灌造林试验,以确定这些技术措施是否能有效提高古尔班通古特沙漠地区免灌造林成活率。结果表明:实施这些措施后,不同立地条件之间梭梭免灌造林成活率存在显著差异;水分是限制古尔班通古特沙漠梭梭免灌造林成活的关键因子,土壤理化性质对梭梭免灌造林成活率影响不显著;三种造林措施对梭梭免灌造林成活率有一定作用,但效果不显著。     

沙漠生物结皮对维管植物养分吸收的影响

生物结皮是沙地表面被固定的重要特征,并能够富集养分,通过降水淋溶作用改善沙丘土壤的性质。研究表明,生物结皮层覆盖对植物体的养分元素吸收具有促进作用,但是,由于不同植物养分生理特性的差异及其根系分布深度的不同,不同植物吸收养分时对生物结皮层肥岛效应的敏感程度不同。     

Microbiotic Crust Influence on Unsaturated Hydraulic Conductivity

Microbiotic crusts occur extensively in rangeland soils . Developed by filaments of cyanobacteria and algae , and thalli of lichen and moss entanglement of soil particles , they create a physical discontinuity in the surface profile with greater concen trations of clay , silt , and potentially hydrophobic organic matter. These conditions potentially contribute to variability in soil hydrology of arid land and should be considered in the development of hydrologic and erosion models. However, there is limited manipulative research examining the functional relationships between soil and microbiotic crusts . We investigated the influence of cyanobacterial-dominated microbiotic crust on measured hydraulic conductivity (K) in a sandy loam soil at a southeastern Utah site . Using a tension infiltrometer , we determined K under three surface treatments: undisturbed , chemically killed (representing dead microphytes within the crust), and removed (scalped) microbiotic crusts. We applied treatments to spatially interspersed intact surface soils within shrub interspaces . Microbiotic crusts at this site and in this stage of successional development had no discernible influence on K. This finding supports results from research conducted in a variety of soils from sandy to silt dominated with a range of microbiotic development . Because this research was site and time specific , and because the role of microbiotic crusts in the environment continues to be debated , additional research is warranted to deter mine how stage of development of microbiotic crust influences soil hydrology .