甘南草原高原鼢鼠年龄划分及其组成分析

建立高原鼢鼠(Eospalax baileyi)种群年龄鉴定划分标准,可为对其的监测及防控提供科学依据。研究于2015年5月、10月分别在甘南草原碌曲县采用夹捕法捕捉高原鼢鼠469只(雄鼠209只,雌鼠260只),在对样本进行逐个解剖和数据记录之后,参考其体重、体长、胴体重及毛色等,对高原鼢鼠的年龄划分标准进行研究。依据胴体重将高原鼢鼠分为6组:亚成年组(雄144 g,雌106 g),成年Ⅰ组(雄144~210 g,雌106~148 g)、成年Ⅱ组(雄211~276 g,雌149~190 g)、成年Ⅲ组(雄277~342 g,雌191~232 g)、成年Ⅳ组(雄343~408 g,雌233~274 g)和老年组(雄409 g,雌275 g)。年龄结构表显示,不同的季节和不同地理区域高原鼢鼠的种群年龄结构类型均为增长型。     

贝加尔针茅草原土壤真菌群落结构对氮素和水分添加的响应

研究氮沉降和降雨变化对土壤真菌群落结构的互作效应,对未来预测多个气候变化因子对草地生态系统的交互作用具有重要意义。以施氮和灌溉模拟氮沉降和降雨增加,采用裂区设计,应用高通量测序技术,研究8个氮添加水平(0、15、30、50、100、150、200、300 kg N hm~(-2)a~(-1))和2个水分添加水平(不灌溉、模拟夏季增雨100 mm灌溉)对土壤真菌群落结构的影响。结果表明,氮素和水分添加后,土壤真菌群落中占优势的门类分别为接合菌门Zygomycota(22.0%—48.9%)、担子菌门Basidiomycota(7.8%—18.5%)、子囊菌门Ascomycota(9.4%—20.1%)、球囊菌门Glomeromycota(0.7%—3.1%)、壶菌门Chytridiomycota(0.1%—1.3%)。常规降雨条件下,随着氮添加水平升高,接合菌门相对丰度呈现出先升高后降低的趋势,N50处理最高;子囊菌门相对丰度在高氮添加时(N100—N300)呈升高趋势。而在氮素和水分同时添加条件下,随着氮添加水平升高,接合菌门相对丰度呈降低趋势,子囊菌门相对丰度变化则不明显。在相同的氮添加水平下,水分添加使接合菌门相对丰度增加,而担子菌门、子囊菌门、球囊菌门和壶菌门的相对丰度降低。在不同氮素和水分添加条件下,有5个土壤真菌门类11个真菌纲相对丰度变化显著。接合菌门的Mortierella属,担子菌门的Entolomataceae科和Geastrum属相对丰度变化极显著,可作为土壤真菌群落结构变化的指示种。PCo A分析结果也表明氮素和水分添加改变了土壤真菌群落结构。植物-土壤-微生物系统的结构方程模型结果表明,植物群落组成及植物物种丰富度的变化是土壤真菌群落结构发生变化的主要影响因素,土壤无机氮及p H的变化主要通过影响植物群落间接影响真菌群落,其对真菌群落的直接影响则较小。综上,氮素和水分添加改变了土壤真菌群落结构,且两者存在明显的互作效应,水分添加可改变氮添加对土壤真菌群落的影响。     

植被退化对温带典型草原根系-土壤系统碳氮分配的影响

以3种不同退化程度的温带典型草原(大针茅轻度退化、中度退化和重度退化)为研究对象,研究植被退化对温带典型草原土壤及根系碳氮含量及储量的影响。结果显示:(1)植被退化对地下根系碳含量影响不显著(P0.05),而对地下根系氮含量的影响显著(P0.05),中度退化样地根系氮含量显著高于轻度退化和重度退化样地(P0.05)。(2)植被退化对根系碳氮储量影响显著(P0.05),根系碳氮储量随着土层深度增加而减少,总根系碳氮储量随退化程度加剧而降低。(3)土壤有机碳、总碳和总氮含量及储量均受退化程度和采样深度的影响显著(P0.05),其含量随着土壤深度的增加而显著减少,随退化程度加剧而显著降低(P0.05)。(4)土壤是根系-土壤系统碳氮储存的最主要场所,储量占比90%以上。虽然土壤碳氮储量均存在表层聚集现象,但表层储量所占比例在各样地间差异显著(P0.05)。     

典型草原啮齿动物密度与牧草损失量的关系

研究啮齿动物密度对牧草损失量的关系,对于计算草地经济损害水平至关重要,可以为草地畜牧业管理决策提供指导。本研究于2012 - 2016 年,在锡林郭勒典型草原(东乌珠穆沁旗),应用标志重捕法和样方法对啮齿动物密度以及9 月份植物地上生物量进行调查,用啮齿动物密度及其日食量来估算鼠类对牧草的损害程度,确定牧草损失量。研究结果表明:(1)啮齿动物密度与牧草损失量的最佳拟合曲线是三参数S 型曲线,为:Loss = k/(1+e ^{a - rdensity});(2)当啮齿动物密度>906 个标准鼠单位/hm² 时,牧草产量发生最大损失(牧草产量损失比=23.30% );(3)根据所拟合的曲线,得出该类型草地啮齿动物对牧草损害的危害阈值为174 个标准鼠单位/hm² 。     

Effects of fencing on ecosystem carbon exchange at meadow steppe in the northern slope of the Tianshan Mountains

草本层和大气间的碳交换及其对环境因子的响应是目前研究的热点。该研究通过静态箱法, 采用LI-840 CO₂/H₂O红外分析仪, 对新疆天山北坡草甸草原围封9年的样地和围栏外自然放牧生态系统碳交换进行监测, 分析了围栏内外生态系统碳交换的差异性、日变化、季节变化及其与环境因子的关系。结果表明: 围栏内生态系统碳交换高于围栏外, 围栏内外表现出明显的差异性; 围栏内外生态系统碳交换均存在明显的日变化和季节变化规律, 呈单峰曲线, 且在植物生长季峰形比较明显。在整个监测期间, 围栏内外生态系统CO₂净交换最小值分别为-7.62和-6.63 μmol·m ^-2·s ^-1, 生态系统呼吸最大值分别为8.55和7.04 μmol·m ^-2·s ^-1, 生态系统总初级生产力最大值分别为-14.66和-13.89 μmol·m ^-2·s ^-1。因围栏内植被得到保护, 草本植物生长茂盛, 光合作用强, 生态系统CO₂净交换较小, 同时有机碳的输入增强了生态系统呼吸。分析发现生态系统碳交换与气温和0-10 cm土壤温度显著相关, 与气温的相关性高于与0-10 cm土壤温度的相关性, 且围栏内禁牧处理相关性高于围栏外自然放牧草地; 土壤含水量与生态系统碳交换存在一定的相关性, 但其相关性略低于温度与生态系统碳交换的相关性。     

Spatio-environmental determinants of the genetic structure of three steppe species in a highly fragmented landscape

Habitat fragmentation can lead to substantial genetic depletion. As a consequence, restoration schemes often involve the introduction of propagules into isolated plant populations to improve genetic diversity. To avoid introducing maladapted seed material, such measures need to account for landscape genetic processes. However, surprisingly little is known as to whether different species within a distinct fragmented ecosystem respond similarly or idiosyncratically to eco-geographical variation.Using AFLP markers, we studied the population genetic structure in three species of the highly fragmented Kulunda steppe (South Siberia): Adonis villosa, Jurinea multiflora and Paeonia hybrida. In each population, we conducted a vegetation survey. We performed Mantel tests and an RDA approach to investigate how genetic structure was affected by three spatio-environmental variables: spatial distance, floristic composition and climate.Despite strong fragmentation, genetic diversity was moderate (A. villosa, J. multiflora) to high (P. hybrida), while differentiation was weak (A. villosa) to moderate (P. hybrida, J. multiflora). Mantel tests showed that spatial distance correlated with genetic distance in A. villosa and P. hybrida. Floristic composition was significantly associated with genetic differentiation in A. villosa. Climate did not have an effect on genetic structure in any species.All three species are long-lived, which may contribute to explaining why genetic effects of recent fragmentation are still limited. We highlight that floristic composition can be a powerful predictor of population differentiation in species that show rather stable conditions in their recent population histories (e.g. A. villosa). This can have important implications for identifying source populations where restoration actions involve the (re)introduction of propagules. In contrast, for P. hybrida and J. multiflora, we could not identify deterministic drivers of differentiation. We advocate that future studies should aim at disentangling the interactive effects of varying life cycles, eco-evolutionary population histories and spatio-environmental heterogeneity in fragmented landscapes.     

草原区不同植物群落蒸发蒸腾的研究

 在中国科学院内蒙古草原生态系统定位研究站,采用“土柱称重法”对典型草原群落蒸发蒸腾进行实验观测,主要研究结果如下：1．草原沙地、羊草草原和河漫滩草甸是本地区差异明显的三种群落。草甸蒸腾最大(9.2 mm·d-1),比另两种群落高2—3倍;草甸蒸发最小(0.4mm·d-1),约为沙地的1／4,草原 的l／8。2．羊草草原在本区分布广,大针茅草原是本区半干旱地带性代表。由于这两种群落主要有关背景值的不同,羊草群落蒸散值(4.4—5.Omm·d-1)明显高于大针茅群落(3.5—3.8 mm·d-1),而且羊草群落的T／E1)值(～2)也明显大于大针茅(～1)。在生长季节中,羊草草原蒸散随气温升高而升高,在盛夏达最高值,然后随气温降低而降低。然而由于降雨变化的影响,羊草草原蒸发蒸腾的季节变化时而出现较大幅度的波动。3．根据1989年实测的降水和羊草群落蒸发蒸腾的季节变化,分析羊草群落的水分收支,可以看到实验区羊草草原的水分收支是大体平衡的。     

Responses of a C3 and a C4 perennial grass to elevated CO2 and temperature under different water regimes

An experiment was carried out to determine the effects of elevated CO₂, elevated temperatures, and altered water regimes in native shortgrass steppe. Intact soil cores dominated by Bouteloua gracilis, a C₄ perennial grass, or Pascopyrum smithii, a C₃ perennial grass, were placed in growth chambers with 350 or 700 μL L^?1 atmospheric CO₂, and under either normal or elevated temperatures. The normal regime mimicked field patterns of diurnal and seasonal temperatures, and the high-temperature regime was 4 °C warmer. Water was supplied at three different levels in a seasonal pattern similar to that observed in the field. Total biomass after two growing seasons was 19% greater under elevated CO₂, with no significant difference between the C₃ and C₄ grass. The effect of elevated CO₂ on biomass was greatest at the intermediate water level. The positive effect of elevated CO₂ on shoot biomass was greater at normal temperatures in B. gracilis, and greater at elevated temperatures in P. smithii. Neither root-to-shoot ratio nor production of seed heads was affected by elevated CO₂. Plant tissue N and soil inorganic N concentrations were lower under elevated Co₂, but no more so in the C₃ than the C₄ plant. Elevated CO₂ appeared to increase plant N limitation, but there was no strong evidence for an increase in N limitation or a decrease in the size of the CO₂ effect from the first to the second growing season. Autumn samples of large roots plus crowns, the perennial organs, had 11% greater total N under elevated CO₂, in spite of greater N limitation.     

The influence of soil texture on the soil water dynamics and vegetation structure of a shortgrass steppe ecosystem

We analyzed soil water data from three sites with different soil textures in the shortgrass steppe of northeastern Colorado, USA. Our objective was to evaluate the relationship between the occurrence of plant functional types and the effect of soil texture on soil water availability. Soil water availability was greatest in the upper soil layers at all three sites, but the loamy sand site had significantly greater soil water availability than the sandy clay loam and sandy clay sites in wetter years at depths below 60 cm. Calculations of proportional water availability by layer using both field data and fifty-year soil water model simulations, showed that the sandy clay loam and sandy clay soils on average had greater water availability in layers 30 cm and above, but that the loamy sand had the greatest water availability in layers beneath this, particularly at 105 cm. This observation can be linked to the occurrence of a fine textured subsoil at this site. The textural pattern in the loamy sand profile effectively creates two water resources: a shallow pool accessible to all plants; and a deep pool accessible only to deep-rooted plants. This is offered as an explanation for the co-dominance of the two main plant functional types at the loamy sand site. At the other two sites, shallow-rooted shortgrass vegetation dominated, being more consistent with the general pattern for the area. Thus the patterns of vegetation structure at the three sites were consistent with the hypothesis. Aboveground net primary production data for the three sites, along with transpiration estimates from the model simulations, indicated that the additional water availability in the coarse textured soil was associated with higher overall plant productivity.Nomenclature: Taxonomic nomenclature follows R. L. McGregor & T. M. Barkley (1986) Flora of the Great Plains. Great Plains Flora Association. University Press of Kansas, Lawrence.     

中国东北草原植物中的C3和C4光合作用途径

以光合作用关键羧化酶ＰＥＰＣ和ＲｕＢＰＣ活性化,并且参照叶片ＣＯ补偿浓度,δ＾１３Ｃ值和叶片解剖结构特点来鉴定东北草原区２３３种植物的Ｃ３,或Ｃ４光全作用途径,这些植物隶属于１４４属７３科,其中１３７种为首次鉴定。８９种具有Ｃ４光合作用途径,隶属于５５属１７科;１４４种人有Ｃ３光俣作用途径;隶属于９４属２８在多数Ｃ４种分布在禾本科、莎草科、苋科和藜科。苋属、地肤属、狗昌属和虎尾草属中的均为Ｃ４植物