Relationships between precipitation, soil water and groundwater at Chongling catchment with the typical vegetation cover in the Taihang mountainous region, China

Vegetation cover plays an important role in the process of evaporation and infiltration. To explore the relationships between precipitation, soil water and groundwater in Taihang mountainous region, China, precipitation, soil water and water table were observed from 2004 to 2006, and precipitation, soil water and groundwater were sampled in 2004 and 2005 for oxygen-18 and deuterium analysis at Chongling catchment. The soil water was sampled at three sites covered by grass (Carex humilis and Carex lanceolata), acacia and arborvitae respectively. Precipitation is mainly concentrated in rainy seasons and has no significant spatial variance in study area. The stable isotopic compositions are enriched in precipitation and soil water due to the evaporation. The analysis of soil water potential and isotopic profiles shows that evaporation of soil water under arborvitae cover is weaker than under grass and acacia, while soil water evaporation under grass and acacia showed no significant difference. Both delta O-18 profiles and soil water potential dynamics reveal that the soil under acacia allows the most rapid infiltration rate, which may be related to preferential flow. In the process of infiltration after a rainstorm, antecedent water still takes up over 30% of water in the topsoil. The soil water between depths of 0-115 cm under grass has a residence time of about 20 days in the rainy season. Groundwater recharge from precipitation mainly occurs in the rainy season, especially when rainstorms or successive heavy rain events happen.

围封对退化矮嵩草草甸群落结构和主要种群空间分布格局的影响

通过研究围栏封育1年后中度退化的矮嵩草草甸（夏季牧场）群落结构的变化,探讨主要植物种群在小尺度（50 cm×50 cm）上的空间分布格局,并从生活史特征和生态适应对策等角度探讨产生和维持这些格局的机理。结果表明,围封1年显著降低了群落中主要种群矮嵩草（Kobresia humilis）、高山唐松草（Thalictrum alpinum）和雪白委陵菜（Potentilla nivea）的重要值,而增加了线叶龙胆（Gentiana farreri）的重要值;显著增加了群落的地上生物量和总生物量,但对地下生物量和群落多样性的影响不显著。围封使退化矮嵩草草甸主要种群矮嵩草、高山唐松草、珠芽蓼（Polygonum viviparum）、线叶嵩草（Kobresia capillifolia）和金露梅（Potentilla fruticosa）等空间分布格局从放牧后的随机分布向聚集分布发展,而雪白委陵菜、重齿风毛菊（S.katochaeteMaxim）、矮火绒草（Leonto-podium nanum）和美丽风毛菊（Saussurea pulchra）等种群的空间分布格局没有发生改变;但黑褐苔草（Carex atro-fusca）的空间格局从放牧后的聚集分布转向随机分布。因此,退化的矮嵩草草甸在围封的初始阶段,由于避免了家畜的选择性采食及其践踏作用,首先可能是使主要种群的空间分布格局有从随机分布向聚集分布变化的趋势,从而使小尺度的种间隔离来降低种间的竞争强度,从而改变了不同物种对资源和空间的竞争能力,进而推动群落物种组成和结构的恢复演替。

青藏苔草的组织培养和快速繁殖

1植物名称青藏苔草(Carex moorcroftii Falc ex Boott)。2材料类别种子。3培养条件(1)诱导培养基:MS+NAA 0.5 mg•L~(-1) (单位下同)+6-BA 1+2,4-D 0.5;(2)继代培养基:MS+NAA 0.5+6-BA 0.5+2,4-D 2;(3)芽分化培养基:MS+6-BA 1+NAA 1;(4)生根培养基:1/2MS+ IAA 3。以上培养基中均附加3%蔗糖和0.7%琼脂,pH5.8。

青藏高原几种高寒植物的抗寒生理特性

研究了青藏高原高寒地区3种多年生植物在生长过程中植物叶组织的可溶性糖、脯氨酸和丙二醛（MDA）含量、超氧化物歧化酶（SOD）和过氧化物酶（POD）活性的变化及其生理特性。结果表明；矮嵩草（Kobresia humilis）、垂穗披碱草（Elymus nutans）和黑褐苔草（Carex atro-fusca）叶中的可溶性糖含量随着生长期的进程而增加；脯氨酸含量的变化因植物种类的不同而表现各异，其中在各生长期．垂穗披碱草的脯氨酸含量均高于矮嵩草和黑褐苔草，并在草盛中期表现出明显的差异；3种高寒植物叶片中的丙二醛（MDA）含量随着生长季和气温的变化而呈现不断增加的趋势；3种植物中的超氧化物歧化酶（SOD）和过氧化物酶（POD）活性表现出随生长期和气温变化而改变的趋势，但黑褐苔草的2种膜保护酶活性最高，垂穗披碱草的次之．矮嵩草最低。可见，在不同生长季，这3种高寒植物的抗寒生理反应或低温适应方式可能是多途径的．其中在抗寒物质代谢、膜脂过氧化能力和抗氧化酶系统等方面，有生理反应的共同规律和各自特有的生理抗寒特性．其适应性与抗逆性有所不同，这种差异和生理特性可能与高寒植物的遗传特性和极端高寒低温环境胁迫有关。

青藏高原5种牧草木质素含量及其体外消化率研究

在海拔高度3200 m的中国科学院海北高寒草甸生态系统定位站选取羊茅（Festuca ovina）、早熟禾（Poa annua）、（上艹下洽）草（Koeoeriacristata）以及莎草科的矮蒿草（Kobresia humilis）、黑褐苔草（Carex alrofusca)5种青藏高原重要牧草品种，分别测定羊茅、早熟禾、（上艹下洽）草、矮蒿草茎、矮蒿草叶、黑褐苔草茎和黑褐苔草叶的木质素含量，并采用二级离体培养法测定其体外消化率，比较不同牧草间木质素含量及消化率差异。1999和2000年两年的实验结果表明，牧草木质素含量与其体外消化率之间为极显著负相关（P<0.01）；就同种牧草不同器官而言，牧草茎的木质素含量明显高于叶，其降解率较低；3种禾本科牧草及2种莎草科牧草不同牧草品种间木质素含量和体外消化率差异不显著。

青海湖区针茅草原植物群落特征及群落多样性研究

根据样方调查资料，采用聚类分析法，研究了青海湖区针茅草原围栏封育后植物群落特征及群落多样性变化。结果表明，草原经过长期围栏后，群落内优势种发生了不同程度的分异，由围栏外的紫花针茅(Stipa purpurea)+青海苔草(Carex ivanovae)草原演变成围栏内的冷地早熟禾(Poa crymophila)+猪毛蒿(Artemisia scoparia)草原群落，导致了群落结构特征的变化；长期的围栏活动对提高草原群落的盖度和生产能力是有益的，但却降低了群落的物种丰富度和多样性；草原开垦后，对周围草原有明显的影响，所形成土垄的群落特征和多样性变化都发生了极大的差异，成为赖草(Leymus secalinus)+大籽蒿(Atremisia sieversiana)群落类型，群落的物种丰富度和多样性均降低。

青藏高原不同海拔梯度2种莎草科牧草模拟体外消化率研究

利用大板山北坡3200m～3800m的海拔梯度，分别在3200 m、3400m、3600m和3800m处选取矮嵩草（Kobresia humilis)、黑褐苔草（Carex alrofusca)2种青藏高原重要莎草科牧草，并用二级离体培养法模拟测定其体外消化率，1999和2000年的测定结果发现，随着海拔升高牧草体外消化率呈增加的趋势，海拔高度从3200m升高到3800m，矮嵩草叶、矮嵩草茎、黑褐苔草叶、黑褐苔草茎的体外消化率分别增加了8.30和4.48、8.45和5.03、10.94和9.58、7.85和8.09个百分点。显著性分析结果表明，牧草体外消化率与牧草所生长的海拔高度之间的正相关关联差异达到显著水平（P＜0.05)。

Net primary productivity and spatial distribution of vegetation in an alpine wetland, Qinghai-Tibetan Plateau

To initially describe vegetation structure and spatial variation in plant biomass in a typical alpine wetland of the Qinghai-Tibetan Plateau, net primary productivity and vegetation in relationship to environmental factors were investigated. In 2002, the wetland remained flooded to an average water depth of 25 cm during the growing season, from July to mid-September. We mapped the floodline and vegetation distribution using GPS (global positioning system). Coverage of vegetation in the wetland was 100%, and the vegetation was zonally distributed along a water depth gradient, with three emergent plant zones (Hippuris vulgaris-dominated zone, Scirpus distigmaticus-dominated zone, and Carex allivescers-dominated zone) and one submerged plant zone (Potamogeton pectinatus-dominated zone). Both aboveground and belowground biomass varied temporally within and among the vegetation zones. Further, net primary productivity (NPP) as estimated by peak biomass also differed among the vegetation zones; aboveground NPP was highest in the Carex-dominated zone with shallowest water and lowest in the Potamogeton zone with deepest water. The area occupied by each zone was 73.5% for P. pectinatus, 2.6% for H. vulgaris, 20.5% for S. distigmaticus, and 3.4% for C. allivescers. Morphological features in relationship to gas-transport efficiency of the aerial part differed among the emergent plants. Of the three emergent plants, H. vulgaris, which dominated in the deeper water, showed greater morphological adaptability to deep water than the other two emergent plants.

Carbon dioxide dynamics and controls in a deep-water wetland on the Qinghai-Tibetan Plateau

To initially characterize the dynamics and environmental controls of CO2, ecosystem CO2 fluxes were measured for different vegetation zones in a deep-water wetland on the Qinghai-Tibetan Plateau during the growing season of 2002. Four zones of vegetation along a gradient from shallow to deep water were dominated, respectively by the emergent species Carex allivescens V. Krez., Scirpus distigmaticus L., Hippuris vulgaris L., and the submerged species Potamogeton pectinatus L. Gross primary production (GPP), ecosystem respiration (Re), and net ecosystem production (NEP) were markedly different among the vegetation zones, with lower Re and GPP in deeper water. NEP was highest in the Scirpus-dominated zone with moderate water depth, but lowest in the Potamogeton-zone that occupied approximately 75% of the total wetland area. Diurnal variation in CO2 flux was highly correlated with variation in light intensity and soil temperature. The relationship between CO2 flux and these environmental variables varied among the vegetation zones. Seasonal CO2 fluxes, including GPP, Re, and NEP, were strongly correlated with aboveground biomass, which was in turn determined by water depth. In the early growing season, temperature sensitivity (Q(10)) for Re varied from 6.0 to 8.9 depending on vegetation zone. Q(10) decreased in the late growing season. Estimated NEP for the whole deep-water wetland over the growing season was 24 g C m(-2). Our results suggest that water depth is the major environmental control of seasonal variation in CO2 flux, whereas photosynthetic photon flux density (PPFD) controls diurnal dynamics.

Distribution and species diversity of plant communities along transect on the Northeastern Tibetan plateau

The distribution and species diversity of plant communities along a 600 km transect through the northeastern Tibetan Plateau (32 degrees 42'-35 degrees 07' N, 101 degrees 02'-97 degrees 38' E) with altitudes from 3255 to 4460 m are described. The transect started from the Youyi Bridge of Banma through Dari, Maqin and Maduo to Zaling Lake. The data from 47 plots along the transect are summarized and analyzed. The mean annual temperature, the mean annual rainfall and the length of growing season decreases from 2.6 to -4.5 degrees C, from 767.2 to 240.1 mm, from 210 to 140 days, respectively, along the transect from the southeastern Banma to northwestern Zaling Lake. The number of vascular plant species recorded in 47 plots is 242 including 2 tree, 34 shrub, 206 herb species. Main vegetation types on the transect from southeast to northwest are: Sabina convallium forest, Picea likiangensis forest, Pyracantha fortuneana + Spiraea alpina shrub, Hippophae neurocarpu shrub, Sibiraea angustata + Polygonum viviparum shrub, Stellera chamaejasme herb meadow, Potentilla fruticosa + Salix obscura + Carex sp. Shrub, Kobresia capillifolia meadow, P. froticosa + Kobresia humilis shrub, Caragana jubata + S. obscura shrub, Kobresia tibetica meadow, Kobresia pygmaea meadow, K. pygmaea + Stipa purpurea steppe meadow, Stipa purpurea steppe. Plant richness and diversity index all showed a decreasing trend with increasing of elevation along transect from southeast to northwest. Detailed information on altitudinal ranges and distribution of the alpine vegetation, vascular flora and environments over the alpine zone at northeastern Tibetan Plateau provides baseline records relevant to future assessment of probable effects of global climate changes.

Methane emissions from different vegetation zones in a Qinghai-Tibetan Plateau wetland

We measured methane (CH4) emissions in the Luanhaizi wetland, a typical alpine wetland on the Qinghai-Tibetan Plateau, China, during the plant growth season (early July to mid-September) in 2002. Our aim was to quantify the spatial and temporal variation of CH4 flux and to elucidate key factors in this variation. Static chamber measurements of CH4 flux were made in four vegetation zones along a gradient of water depth. There were three emergent-plant zones (Hippuris-dominated; Scirpus-dominated; and Carex-dominated) and one submerged-plant zone (Potamogeton-dominated). The smallest CH4 flux (seasonal mean = 33.1 mg CH4 m(-2) d(-1)) was, observed in the Potamogeton-dominated zone, which occupied about 74% of the total area of the wetland. The greatest CH4 flux (seasonal mean = 214 mg CH4 m(-2) d(-1)) was observed in the Hippuris-dominated zone, in the second-deepest water area. CH4 flux from three zones (excluding the Carex-dominated zone) showed a marked diurnal change and decreased dramatically under dark conditions. Light intensity had a major influence on the temporal variation in CH4 flux, at least in three of the zones. Methane fluxes from all zones increased during the growing season with increasing aboveground biomass. CH4 flux from the Scirpus-dominated zone was significantly lower than in the other emergent-plant zones despite the large biomass, because the root and rhizome intake ports for CH4 transport in the dominant species were distributed in shallower and more oxidative soil than occupied in the other zones. Spatial and temporal variation in CH4 flux from the alpine wetland was determined by the vegetation zone. Among the dominant species in each zone, there were variations in the density and biomass of shoots, gas-transport system, and root-rhizome architecture. The CH4 flux from a typical alpine wetland on the Qinghai-Tibetan Plateau was as high as those of other boreal and alpine wetlands. (C) 2004 Elsevier Ltd. All rights reserved.