Haloalkaliphilic actinomycetes in soils of Mongolian desert steppes

The abundance of actinomycetes isolated from the soils of Mongolian desert steppes varies from several thousand to hundreds of thousands of CFU/g soil, depending on soil type and isolation medium. Eight actinomycete genera have been found in these soils: Streptomyces, Micromonospora, Saccharopolyspora, Actinomadura, Microtetraspora, Thermomonospora, Nocardia, and Dactylosporangium. The streptomycete complexes of brown desert-steppe and gray-brown desert alkaline soils include halophilic, alkaliphilic, and haloalkaliphilic species that grow most successfully on the media with a salt concentration of 5% and pH 8–9.     

Efficient sampling of ground-dwelling arthropods using pitfall traps in arid steppes

Pitfall trapping is probably the most frequently used method for sampling ground-dwelling arthropods. While the capture of specimens in pitfall traps largely depends on the number of individuals in the sampled area, trap design and trapping effort for a given environment, can also affect sampling success. The aim of this study was to determine the best pitfall trapping design for collecting ground-dwelling arthropods in the wind-blown and cold arid steppe areas of Patagonia. We tested four designs of traps, six types of preservative and different times of activation as well as the quantity of traps. Both preservation attributes and sampling efficiency differed between different trap designs and fluids compared. We conclude that in order to obtain reliable data on the structure of a community of ground-dwelling arthropods in Patagonia, at least three pitfall traps per experimental unit are required. In addition, traps should be opened for a minimum of 10 days filled with 300 ml of 30% ethylene glycol. We also suggested the use of a simple trap design (i. e. without funnel or roof). We believe these findings will contribute to more appropriate sampling of the ground dwelling fauna of Patagonia as well as other arid areas, leading to more reliable diversity studies.     

Assessment of biotic and abiotic factors controlling herbaceous biodiversity in Mongolian steppes

Spatial patterns of herbaceous biodiversity in Mongolia steppe were examined and explained with biotic and abiotic factors including climate, livestock grazing, and fire disturbance. Vegetation data were collected from 63 sites across different steppe types (i.e., semi-desert, typical, and forb steppes) in 2012 and 2013. Three categorical (three steppe types, burned or not, grazed or not) and three continuous variables (precipitation, vegetation productivity, site-camp distance) were developed from national climate and GIS database of Mongolia and two satellite sensor products: Tropical Rainfall Measuring Mission (TRMM) precipitation and June-to-August accumulated Moderate Resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI_JJA). The prescribed factors were utilized to examine single- and multiple-factor effects on biodiversity and community structure, by using correlation, stepwise multiple regression analysis, and ordination. Our results indicate the positive effect of precipitation and fire but negative effect of grazing on biodiversity in our study region. Localized herding effect was recognized to areas less than 1.5 km away from the herder's camp sites. Fire, precipitation and productivity (NDVI_JJA) were identified as important factors affecting biodiversity of remote regions. Based on the results, we infer that pastureland biodiversity of Mongolia is controlled by region-scale variations of climate and vegetation productivity, but locally modified by intensive livestock grazing pressure with different grazing sensitivity for different steppe types.     

Habitat engineering under dry conditions: The impact of pikas (Ochotona pallasi) on vegetation and site conditions in southern Mongolian steppes

Question: Does ecosystem engineering by small mammals have a significant influence on vegetation patterns in the arid steppe vegetation of southern Mongolia? Location: Gobi Altay Mountains, southern Mongolia. Methods: We assessed the impact of the small lagomorph Ochotona pallasi on plant community composition, nutrient levels and biomass production in montane desert steppes. Data were derived from vegetation relevés, harvests of above‐ground standing crop and a bioassay, followed by analyses of soil and plant nutrient contents. Results: Although the local climate is arid with <150 mm annual precipitation, clear evidence of allogenic ecosystem engineering was found. Plant communities on burrows differed from those on undisturbed steppe in that they contained more species of annuals and dwarf shrubs, and a greater abundance of the important fodder grass Agropyron cristatum. Standing crop and nutrient concentrations were higher for plants growing on burrow soil. In situ measurements and a pot experiment showed that this effect was related to increased levels of soil nutrients (P, K, N) rather than moisture availability. Conclusions: The study confirms that O. pallasi positively influences soil nutrient levels on its burrows, which leads to increased grassland productivity even under dry conditions. Thus, O. pallasi does not deteriorate site conditions, and the need for presently applied pest control schemes aimed at this species should be reassessed.     

Annual plants in arid and semi-arid desert regions

Annual plants are the main vegetation in arid and semi-arid desert regions. Because of their unique traits, they are the optimal experimental subjects for ecological studies. In this article, we summarize annual plants’ seed germination strategies, seedling adaptability mechanism to environments, seed dispersal, and soil seed banks. We also discuss the biotic and abiotic factors affecting the composition and dynamics of annual plant populations and communities. Because annual plants have important ecological functions in desert vegetation systems, this study on annual plants will be of great benefit to the conservation and restoration of desert ecosystems, the rational utilization of resources, and the sustainable development of desert regions. __________ Translated from Chinese Journal of Ecology, 2006, 25(7): 851–856 [译自: 生态学杂志]     

Annual plants in arid and semi-arid desert regions

Annual plants are the main vegetation in arid and semi-arid desert regions.Because of their unique traits,they are the optimal experimental subjects for eco-logical studies.In this article,we summarize annual plants' seed germination strategies,seedling adaptability mechanism to environments,seed dispersal,and soil seed banks.We also discuss the biotic and abiotic factors affecting the composition and dynamics of annual plant populations and communities.Because annual plants have important ecological functions in desert vegetation systems,this study on annual plants will be of great bene-fit to the conservation and restoration of desert ecosys-tems,the rational utilization of resources,and the sustainable development of desert regions.     

Effect of enclosure on reproductive allocation of wheatgrass Agropyron mongolicum populations in desert steppes

Plants generally adopt different reproductive strategies to adapt to their environments and increase their fitness. Here, we studied the effects of enclosure cultivation on the reproductive allocation of a wheatgrass species Agropyron mongolicum in the Desert steppes of Northern China. The results showed that: (a) after enclosure cultivation, the height, clump width, coverage, and clump biomass of A. mongolicum significantly increased by 78.96% (p = .040), 63.50% (p = .013), 50.89% (p = .032), and 205.38% (p = .022), respectively, whereas density did not show a significant change (p = .330). (b) Enclosure cultivation significantly affected the biomass of A. mongolicum. Compared with cultivation outside the fence, root, leaf, and spike biomass of A. mongolicum inside the fence significantly increased by 183.52% (p = .020), 334.09% (p = .011), and 381.25% (p = .005), respectively. In addition, root biomass was the highest among the components (38.53 and 13.59 g inside and outside the fence, respectively) and spike biomass was the lowest (6.16 and 1.28 g inside and outside the fence, respectively). (c) Enclosure cultivation affected elemental nutrient allocation and the caloric values of various components of A. mongolicum, and the caloric values are positively correlated with carbon, nitrogen, and phosphorus contents. Enclosure cultivation significantly reduced carbon, nitrogen, and phosphorus in the roots, as well as nitrogen and phosphorus in the spikes, but significantly increased nitrogen in the spikes by 9.78%. The caloric values of A. mongolicum inside and outside the fence in decreasing order were as follows: spikes > leaves > stems > roots. Comparison of cultivation effects between inside and outside the fence showed that the caloric values of the spikes and roots significantly increased by 0.92% and 1.60%, respectively, whereas those of the leaves significantly decreased by 0.70%. Our results demonstrate that the reproductive allocation of elemental nutrients and caloric values in nonreproductive and reproductive organs are plastic to arid environments.     

干旱区荒漠生态系统的土壤呼吸

采用LI-8100土壤碳通量测量系统测定了准噶尔盆地高(B)、低(A)两个盖度级3个典型荒漠植物群落梭梭、盐穗木、假木贼的土壤呼吸速率,比较分析了各样地土壤呼吸的变化特征及水热因子对荒漠土壤呼吸特征的可能影响.结果表明:生长季,土壤呼吸速率存在明显的日变化和季节变化规律,不同盖度和群落类型的荒漠土壤呼吸速率变化形式基本相同.日变化格局最高值出现在12:00～14:00,最低值在8:00或20:00;夏季各月(6、7、8月份)土壤呼吸速率高于秋季月份(9、10月份),春季(5月份)最低.高盖度梭梭群落样地日平均土壤呼吸速率与其他样地存在显著差异.各样地土壤呼吸速率与地表温度呈不同程度的正相关,而与土壤温度的相关性较弱;高盖度盐穗木样地(土壤湿度最高)、梭梭样地(土壤湿度最低)土壤呼吸速率与土壤湿度呈显著负相关.地表温度-土壤湿度的多变量模型能在更大空间尺度解释荒漠土壤呼吸速率时间变化的61.9%.样地间土壤呼吸速率的差异可能主要受土壤湿度影响.高、低盖度的梭梭、盐穗木和假木贼群落的Q10值分别为1.34、1.3、1.65、1.58、1.17和1.31,平均值1.39.     

极旱荒漠植物对AM真菌物种多样性的影响

2015年7月在甘肃安西极旱荒漠国家级自然保护区采集膜果麻黄Ephedra przewalskii、红砂Reaumuria songarica、合头草Sympegma regelii、泡泡刺Nitraria sphaerocarpa和珍珠猪毛菜Salsola passerine 5种典型荒漠植物根区土壤样品,分析了植物种类对arbuscular mycorrhiza(AM)真菌群落组成和生态分布的影响。在分离的7属45种AM真菌中包括无梗囊霉属Acaulospora 17种,球囊霉属Glomus 13种,这两属是5种植物共同优势属;盾巨孢囊霉属Scutellospora 5种,管柄囊霉属Funneliformis 4种,根内根生囊霉属Rhizophagus 3种,近明囊霉属Claroideoglomus 2种,多孢囊霉属Diversispora1种。主成分分析研究说明5种植物根区AM真菌群落组成和物种多样性差异显著。结果表明,植物种类对AM真菌群落组成和分布特征影响显著。     

Anthropogenic transformation of soil and vegetation resulting from afforestation in southern steppes

Recent data (2006–2008) on characteristics of the vegetation and soils of the solonetzic complex in areas with tree failures within the Volgograd-Elista-Cherkessk forest shelterbelt have been compared with those obtained prior to afforestation (1950). The results show that the vegetation and soils have changed profoundly. Solonetzic agrozems in tree failure sites have been occupied by herbaceous plant communities similar in composition to natural communities. Anthropogenically altered soils formed under forest plantations have no natural analogs. The initial strongly saline shallow (crusty) solonetz soils with a chloride-sulfate or sulfate-chloride composition of salts have transformed into slightly saline solonetzic and solonchakous agrozems with sodium sulfate salinity or with increased alkalinity in the middle of the soil profile and a dealkalized arable horizon.     

Effects of P fertilisation and ectomycorrhizal fungal inoculation on early growth of eucalypt plantations in southern China

Eucalypt plantations in China have largely been established on soils that are low in phosphorus (P) and have few eucalypt-compatible ectomycorrhizal fungi. Effects of P application and ectomycorrhizal fungal inoculation on early tree growth in plantations of Eucalyptus urophylla Blake in Guangdong (Gaoyao) and E. globulus Labill. in Yunnan (Chuxiong) in southern China were investigated as part of a larger study. Application of superphosphate at establishment, in the presence of a basal fertiliser, increased early growth of E. urophylla and E. globulus. The optimum treatments for maximum stand volume at year 3 were 200 kg P ha^–1 which increased stand volume by 750% on the strongly acidic, P-deficient lateritic red oxisol at Gaoyao, and 40 kg P ha^–1 which increased stand volume by 55% on the mildly P-deficient red ultisol at Chuxiong, at 3 years. Superphosphate increased tree survival at Gaoyao as well as at Chuxiong. Nursery inoculation of eucalypt seedlings with ectomycorrhizal fungi significantly affected tree height and stand volume of the E. urophylla plantation, but the effect (positive or negative) was isolate-dependent and related to tree survival rate. A Laccaria isolate (CSIRO E4728) significantly increased stand volume by 27% at Gaoyao and a Scleroderma (MURU LH041) increased growth by 15% at Chuxiong at age 3 years. All isolates increased tree growth under P-limited soil conditions and only one isolate increased tree growth at marginal soil P. The results suggest that tree growth should be able to be optimised in plantations by the use of effective ectomycorrhizal fungi combined with a judicious fertilisation program at establishment.     

煤炭井工开采对干旱荒漠区植被动态变化的影响

我国西北干旱荒漠区生态环境脆弱,煤炭开采活动严重地破坏植被和影响生态环境,而煤炭井工开采对干旱荒漠区植被动态变化的影响尚不明确。以灵武市为例,采用遥感技术和野外实地调查相结合的方法,分析2000-2019年间煤炭井工开采对植被动态变化的影响。结果表明：灵武市的植被主要以沙蒿（Artemisia salsoloides）、柠条（Caragana korshinskii）和芨芨草（Achnatherum splendens）等荒漠植物为主;2000-2019年间,植被覆盖度（FVC）和绿度变化率（GRC）表明灵武市植被整体呈现改善趋势;归一化植被指数（NDVI）与年降水量（P）和年平均风速（S）等气象因子显著相关,表明气候因子对区域植被动态变化起主要作用;煤炭开采区侵占草地和灌丛面积,使得土地利用类型发生变化,生态环保政策的实施对于区域土地利用类型的变化和植被改善具有重要作用。实地调查分析表明煤炭开采改变了矿区植物群落结构,植被盖度和物种多样性指数均在煤炭开采后1-4a呈下降趋势,5-9a为上升趋势,10a自然恢复后与对照区的变化趋势一致,说明在自然条件下煤炭开采区植被恢复经历了退化期、改善期和初步恢复期等过程。这些研究结果为西北干旱荒漠区煤炭井工开采矿区植被恢复和生态环境建设提供了理论基础。     

Late Holocene vegetation history suggests natural origin of steppes in the northern Mongolian mountain taiga

Insular occurrences of steppe vegetation are a common feature of the northern Mongolian mountain taiga. Steppe vegetation is limited here to southern slopes, whereas northern slopes and valley bottoms are principally wooded with light and dark taiga forests. In a case study in the valley of the river Eroo at Khonin Nuga Research Station in the western Khentey Mountains, we searched for evidence of an anthropogenic versus natural origin of steppe vegetation on the southern slopes. Pollen data of three profiles covering the last 2500 years showed continuous presence of steppe throughout the late Holocene with human influence restricted to the recent past. Virtual absence of charcoal in the soil on and beneath three steppe slopes suggested that the present steppe grasslands are not replacing former forests burnt by humans or lightning. The floodplains in the center of the Eroo valley were recently deforested. This is suggested by the pollen analysis and by interviews with local people on landuse history. Steppe grasslands of the study area have probably never been used as pastures. Pastoral nomads traditionally avoided the Eroo valley near Khonin Nuga because of difficult access and high densities of wolves and bears. All our data suggest that the present vegetation pattern of the western Khentey with steppes (and single small Ulmus pumila trees) on south-facing slopes occurring as islands in the mountain taiga is driven by climate and relief and is not the result of human activities as suggested for other regions of Asia.     

植物对荒漠生境的趋同适应

植物体的表型特征是其基因与生态因子二者共同作用的结果,生活在荒漠生境中的植物由于遭受相同的自然选择压力,在外部形态、内部结构、生活史特征、生理特性、次生代谢产物的合成以及大分子物质的诱导产生等诸多表型方面均表现出高度趋同的现象。随着研究手段的改善,对植物趋同适应的研究已逐渐深入到了分子水平。研究荒漠生境中植物的趋同适应对于人们深刻地认识和理解植物与环境间的相互关系及其分子基础,以及利用功能基因改良重要作物的抗逆性等将会产生深远的影响;对极端干旱环境下特殊次生代谢产物的定向发现及重要先导化合物的筛选等有着重大的指导意义;同时对我国的西部开发及干旱区的生态恢复亦有重要的参考价值。     

Direct and indirect effects of grazing constrain shrub encroachment in semi‐arid Patagonian steppes

Question: What are the long‐term effects of grazing exclusion on the population structure and dynamics of, and interactions among, three dominant shrub species? Location: Grass‐shrub Patagonian steppe, Chubut, Argentina. Methods: Permanent plots were established in grazed paddocks and paddocks excluded from grazing in representative Patagonian rangelands. Shrub abundance, population size‐structure, short‐term (two 3‐yr periods) and long‐term (matrix models) population dynamics, and neighborhood interactions of three native and codominant shrub species (Mulinum spinosum, Senecio filaginoides and Adesmia volckmanni) were measured and analysed using different statistical approaches. Results: The total density of shrubs was 74% higher in paddocks excluded from grazing, owing mainly to increases in Mulinum (80%) and Senecio (68%) species. However, differences in size structure between ungrazed and grazed paddocks were only detected in Mulinum. Demographic rates differed between shrub species, time‐periods and grazing conditions. In particular, recruitment in the short term (especially in wet years) and population growth rate in the long term (λ) were higher in paddocks excluded from grazing only in Mulinum populations. Senecio populations showed a marginal increase in recruitment and mortality independent of the grazing condition in the wet and dry period. Grazing exclusion modified the balance of neighborhood interactions among the three shrub species. In grazing‐exclusion paddocks, there was a balance between positive and negative interspecific interactions, while in grazed paddocks there were more negative intraspecific and interspecific interactions, resulting in a net negative balance of neighborhood interactions. Conclusions: Our understanding of woody encroachment in arid rangelands can be informed through evaluation of direct and indirect effects of grazing exclusion on the abundance and demography of dominant woody species. In Patagonian arid steppes, the occurrence of woody encroachment in rangelands excluded from grazing can be explained by altered responses in plant‐animal and plant‐plant interactions among shrub species.     

干旱区荒漠稀疏植被覆盖度提取及尺度扩展效应

选择线性混合像元分解模型、亚像元模型、最大三波段梯度差法模型以及修正的三波段梯度差法的2个变异模型来提取植被覆盖度,结合地面实测数据,探讨了提取干旱区荒漠稀疏植被覆盖度信息的适宜模型,并以简单平均法模拟了不同尺度的覆盖度影像,通过尺度上推检验了模型在MODIS尺度上的反演效应.结果表明：线性混合像元分解模型反演覆盖度的精度高于其他模型,适于稀疏植被地区,但端元的正确选取较难,从而影响其运用;亚像元分解模型是一个通用模型,植被分类图越精细,通过亚像元分解模型得到的覆盖度精度越高,但这也同时意味着该模型需要测定大量的输入参数;最大三波段梯度差法的算法简单、易于操作,其在农田等中高植被覆盖区及裸土区的预测值与实测值接近,但对干旱区稀疏植被的估计精度偏低;修正后的三波段最大梯度差法模型在稀疏植被覆盖区的预测值与实测值基本一致,在不同尺度上反演的覆盖度信息与实测值的一致性较好.该方法可有效提取干旱区低覆盖度植被信息.     

内蒙古退化荒漠草原土壤有机碳和微生物生物量碳含量的季节变化

为探明荒漠草原土壤有机碳（SOC）和微生物生物量碳（MBC）含量特征,分别在内蒙古达茂旗、四子王旗和苏尼特右旗设置样地,依次代表轻度、中度和重度退化草地,分析了不同样地表层土壤(0～20 cm)SOC和MBC含量变化及季节动态.结果表明：退化草地SOC和MBC含量均随草地退化程度增加而减小;除2006年夏季外,轻度、中度退化荒漠草地的土壤可培养微生物总数都高于重度退化荒漠草地;MBC含量和土壤可培养微生物总数均在夏秋季较高,春冬季较低.相关分析结果显示,SOC含量与MBC含量之间呈极显著正相关（P<0.01）,说明两者均可作为评价荒漠草原草地退化的敏感指标.