祁连山海北地区两种高寒草甸植被类型的土壤热通量比较

对祁连山海北地区矮嵩草(Kobresia humilis)草甸和金露梅(Potentilla fruticosa)灌丛草甸两种植被类型土壤热通量观测和比较分析发现:晴天两种植被类型区土壤热通量日变化均表现为单峰型,夜间低午后高;阴雨天土壤热通量变化复杂,随降水或云层厚薄波动剧烈。金露梅灌丛草甸土壤热通量的日变化较矮嵩草草甸更为平稳。两种草甸土壤热通量的月际变化同样表现为单峰型,12月最低(矮嵩草草甸和金露梅灌丛草甸分别为-40.27MJ/m2和-16.85MJ/m2)、6月最高(矮嵩草草甸和金露梅灌丛草甸分别为20.47MJ/m2和18.98MJ/m2)。矮嵩草草甸与金露梅灌丛草甸土壤热通量的年总量差异明显,分别为-24.72MJ/m2和48.10MJ/m2。表现出前者由土壤深层向地表散热,而后者由地表向土壤深层输送热量。两种植被类型区不同时间尺度上的土壤热通量与冠层净辐射均有显著的线性相关关系。由于冠层厚度的影响,金露梅灌丛草甸土壤热通量所占净辐射的比例较小,同步性较差,反馈延时约2.5h,而矮嵩草草甸的土壤热通量与净辐射的相关性更加密切。     

两种高寒植被长波辐射的气候学特征及比较

地球边界层热量来源是地表吸收太阳短波辐射后再以长波辐射形式加热的结果,而边界层生物活动与近地表热量息息相关,讨论长波辐射的变化特征对生态系统的物质流动及能量交换具有重要意义。以2003年对高寒矮嵩草草甸、金露梅灌丛两种植被类型观测的资料,比较分析了两种植被类型地面长波辐射（ULR）、大气逆辐射（DLR）以及地面有效长波辐射（ELR）的变化特征。结果表明,高寒矮嵩草草甸、金露梅灌丛ULR、DLR以及ELR均具有明显的日、月变化。其中矮嵩草草甸、金露梅灌丛的ULR月平均日变化在北京时间14∶00最高,凌晨最低;DLR在16∶00-18∶00最高,凌晨最低;ELR在8∶00最低,14∶00最高。月变化中,两种植被类型区ULR、DLR的最低值出现在1-2月,较高值出现在7-9月,而ELR变化趋势比较复杂。总体而言,金露梅灌丛的DLR、ULR变化值明显比矮嵩草草甸的高。     

高寒矮嵩草草甸地面热源强度及与生物量关系的初步研究

在青藏高原海北高寒矮嵩草草甸地区,依据2002年涡度相关法观测的能量平衡各分量资料和6-10月植物地上、地下生物量测定值,分析了高寒矮嵩草草甸近地表热量平衡、地面热源强度的变化特征,讨论了地面热源强度与植物生物量季节变化过程中的相互关系。结果表明:在青藏高原海北高寒矮嵩草草甸地区,年内地面均为热源,热源强度季节变化明显,地面热源强度年平均为88.5 W/m2;地上生物量季节变化与热源强度具有显著的正相关关系,而地下生物量季节变化与热源强度关系不明显。     

青海湖2种高寒嵩草湿草甸湿地生态系统水热通量比较

基于涡度相关技术,研究了2015年青海湖2种高寒嵩草湿草甸湿地生态系统水热通量的特征。结果表明:(1)2015年青海湖高寒藏嵩草和小嵩草湿草甸湿地生态系统日平均水汽通量分别为1.74,0.99mm,年水汽通量分别为633.3,362.1mm。(2)青海湖2种高寒嵩草湿草甸湿地生态系统感热、潜热和净辐射日变化均呈单峰曲线,感热和潜热月平均日变化最大值出现的时间均晚于净辐射。藏嵩草湿草甸湿地生态系统感热月均日变化最大值最大为179.06W/m~2,最小为46.02W/m~2;潜热最大为312.55W/m~2,最小为30.58 W/m~2;小嵩草湿草甸湿地生态系统感热月均日变化最大值最大为161.86 W/m~2,最小为31.60 W/m~2;潜热最大为215.44 W/m~2;最小为14.08 W/m~2。(3)通过波文比分析发现,2种高寒嵩草湿草甸湿地生态系统生长季能量分配以潜热为主,非生长季小嵩草湿草甸湿地生态系统能量分配以感热为主,藏嵩草湿草甸湿地生态系统则较为复杂。藏嵩草湿草甸湿地生态系统全年能量平衡率为0.82,小嵩草湿草甸湿地生态系统为0.89,增加土壤热通量项能改善能量平衡状况。     

不同亚高山草甸群落类型的土壤入渗特征及影响因素

对卧龙自然保护区不同海拔高度的典型亚高山草甸群落类型(嵩草草甸、狼毒草甸、糙野青茅草甸)的土壤入渗性能进行了对比研究。结果表明,亚高山草甸土壤入渗过程总体上可分为3个阶段,即入渗瞬变阶段(0—5 min)、入渗渐变阶段(5—30min)和稳定入渗阶段(30min后)。在入渗瞬变阶段和渐变阶段,不同群落类型的入渗速率表现为嵩草草甸狼毒草甸糙野青茅草甸。另外,在嵩草草甸的研究表明,随着土层深度增加,土壤入渗速率呈现逐渐递减的趋势。分别运用Philip、蒋定生、Horton、Kostiakov 4种模型拟合了不同亚高山草甸群落类型的土壤入渗过程,表明Horton模型的拟合精度最高。相关分析表明,亚高山草甸土壤稳渗速率与土壤容重存在极显著负相关关系,而与土壤总孔隙度、非毛管孔隙度、土壤通气度以及单位面积的地上部分生物量均呈极显著正相关关系。     

青藏高原高寒嵩草草甸植被群落特征对退化演替的响应

以空间代替时间的方法,于2012年7月中旬-8月中旬在青藏高原祁连山南麓分别选取原生、轻度、中度和重度4种不同退化梯度的高寒嵩草（Kobresia）草甸,对其土壤理化、水分特征和植被群落进行研究,以探究高寒嵩草草甸生态功能退化过程中植被群落的变化特征.结果表明,中度退化样地的地上生物量、表层（0-10cm）土壤含水量和降水地表入渗速率显著最小（P＜0.01）,表层地下生物量、表层土壤有机质、表层田间持水量和草毡层厚度显著最大（P＜0.01）.基于退化高寒嵩草草甸群落的植被功能群和群落多样性的非度量多维排序结果表明,其退化过程可明确划分为原生植被、轻度退化、中度退化和重度退化4个阶段,冠层高度、地上生物量、草毡层厚度和降水地表入渗速率对群落变化的相对贡献较大.植被群落对退化过程的响应为非平衡型（Non-equilibrium）,群落变化的“分水岭”存在于中度退化和重度退化之间.研究结果对退化嵩草草甸的恢复措施选择具有重要的指导意义.     

高寒矮嵩草草甸地上生物量和叶面积指数的季节动态模拟

基于2007年中国科学院海北高寒草甸生态系统定位站植被和气象观测资料,探讨了高寒矮嵩草草甸群落叶面积指数、地上生物量的季节动态变化及其数学模型,分析了叶面积指数与地上生物量的相互关系,以及气象条件对叶面积指数和地上生物量的影响。结果表明,高寒矮嵩草草甸群落植被生长期地上生物量的季节动态变化可以用Logistic回归模型拟合;植被叶面积指数的季节动态变化可以用三次函数曲线拟合,叶面积指数受温度和降水量的影响明显,与植物生长期日平均气温≥3℃的积温和降水累积量分别有三次函数的拟合关系,而考虑与积温和降水累积量的综合关系可用二元二次函数拟合;同时,叶面积指数与地上生物量之间有二次函数的拟合关系。     

亚高山草甸土纤维素分解过程及与环境因子的对应关系

对海北高寒草甸生态系统的矮嵩草研究表明 ,在亚高山草甸土中纤维素的分解 ,作用均在月均温度最高时达最大 ,2月份最小 ,年内表现有明显的单峰式曲线变化过程 ;非退化矮嵩草草甸的纤维素分解显著高于退化的矮嵩草草甸 ;纤维素分解除自身的季节变化规律外 ,与气象等环境因子有关 ,特别是与水热协调配合具有极显著线性正相关关系 (P <0 .0 0 1 ) .     

草地生物量的动态模拟

本文以作物生长模拟理论为基础,考虑到草原群落多种群的特点，对高寒矮嵩草草甸建立了能反映气象因子与生物因子对种群生物量时间动态综合影响的总模式，包括对任意种群作用、呼吸作用、同化物分配等生理过程的定量模拟及叶面积指数动态、群落结构动态模拟等6类子模式，能够定量地给出该草甸群落地上生物量和地下生物量的季节变化，是草原植被光合产量模拟研究的较好尝试。     

黑河流域甘州区湿地植物物种多样性研究

以芦苇群落和西藏嵩草两个群落为对象,研究了两个群落的植物物种及组成特征。结果表明,芦苇群落以芦苇为优势种,以西藏嵩草为亚优势种,二者重要值之和为0.434 2;西藏嵩草群落以西藏嵩草为优势种,重要值为0.187 6。物种多样性分析表明,两群落的物种多样性指数(H)和均匀度指数(J)均波动幅度较大,优势度(D)值波动幅度较小;芦苇和西藏嵩草群落的多样性指数与均匀度指数呈现出显著的正相关关系,但与物种丰富度指数无明显相关,而与生态优势度指数呈明显的负相关关系;两群落H,D,J和丰富度指数(S)值的差异并不显著;芦苇和西藏嵩草群落的共有种有14种,相似性系数为51.85%,说明西藏嵩草群落和芦苇群落的群落组成相近,它们存在一定的内在联系。     

Plant production, and carbon and nitrogen source pools, are strongly intensified by experimental warming in alpine ecosystems in the Qinghai-Tibet Plateau

The aim of this study was to assess initial effects of warming on the nutrient pools of carbon and nitrogen of two most widespread ecosystem types, swamp meadow and alpine meadow, in the Qinghai-Tibet Plateau, China. The temperature of the air and upper-soil layer was passively increased using open-top chambers (OTCs) with two different temperature elevations. We analyzed air and soil temperature, soil moisture, biomass, microbial biomass, and nutrient dynamics after 2 years of warming. The use of OTCs clearly raised temperature and decreased soil moisture. The aboveground plant and root biomass increased in all OTCs in two meadows. A small temperature increase in OTCs resulted in swamp meadow acting as a net carbon sink and alpine meadow as a net source, and further warming intensified this processes, at least in a short term. On balance, the alpine ecosystems in the Fenghuoshan region acted as a carbon source.     

藏北高寒草甸植物群落对土壤线虫群落的影响

2011年5月—11月,对西藏北部高寒草甸3种典型植物群落下0～30 cm范围内不同深度土层的土壤线虫群落进行调查,浅盆法收集土壤线虫,应用个体密度、多样性指数等特征值来分析高寒环境下土壤线虫群落的组成、分布特征与多样性。调查共分离得到33 038条土壤线虫,隶属于2纲6目51科93属;线虫个体密度平均为847条100 g-1干土;表聚性明显。研究结果表明,不同植物群落间的土壤线虫群落组成存在一定差异,土壤线虫数量的大小顺序为委陵菜植物群落<藏北嵩草植物群落<高山嵩草植物群落,土壤线虫数量差异显著(p<0.05);土壤线虫数量随生长季变化发生明显波动,返青期最多,盛长期次之,枯草期最低;不同植物群落的优势属种类不同。生物多样性为委陵菜植物群落>高山嵩草植物群落>藏北嵩草植物群落,这可能是放牧干扰强度不同,以及植物群落影响下的土壤性质分异所导致的结果。总之,不同植物群落下土壤线虫群落特征的分异初步显示出线虫指示环境因子影响土壤生态系统的潜力。     

Storage and controlling factors of soil organic carbon in alpine wetlands and meadow across the Tibetan Plateau

Alpine wetlands and meadows across the Three Rivers Source Region (TRSR) store high soil organic carbon (SOC). However, information on factors affecting SOC storage is scanty. Herein, we investigated SOC storage and explored factors affecting SOC storage, including climate, soil properties and above- and belowground biomass, using 50 soil profiles across the TRSR on the Tibetan Plateau. The SOC storage was 491.9 ± 158.5 Tg C and 545.2 ± 160.8 Tg C in the TRSR alpine wetlands and meadow, respectively. The SOC stock was positively correlated with the mean annual precipitation. However, no significant correlation between SOC stock and mean annual temperature was observed, as opposed to the global trend. In addition, SOC stock was positively correlated with both the aboveground biomass (AGB) and belowground biomass (BGB). Soil pH indirectly affected SOC stock, while SOC stock positively correlated with Al and Fe oxyhydroxides. Compared with vegetation biomass and climatic factors, soil properties, including soil pH and Al and Fe oxyhydroxides (Al_o and Fe_o), affected not only SOC stock variation but also affected the impact of vegetation and climatic factors on SOC stock. Climate factors, AGB, BGB, soil pH, Al_o and Fe_o jointly accounted for 59% of SOC stock variation in alpine wetlands and 64% of SOC stock variation in alpine meadow. This study suggests that soil properties are the dominant factors affecting SOC variation in alpine wetlands and meadow on the Tibetan Plateau.     

放牧高寒嵩草草甸的稳定性及自我维持机制

以空间代时间,在＂三江源＂和中国科学院海北高寒草甸生态系统研究站地区,将处于不同退化阶段的高寒嵩草草甸作为研究对象,进行了其植物群落、地表状况、草毡表层厚度、根土比和水分渗透速率的演替过程与规律研究,以明晰放牧高寒嵩草草甸退化过程中其系统稳定性及自我维持机制。结果表明,高寒嵩草草甸虽然结构简单,但在长期适应寒冷气候进化过程中形成了低矮化、细绒化和草毡表层加厚、极度发育等一系列特殊的稳定性维持机制,可以承受一定范围内的人为干扰和气候波动,具有较高的系统稳定性与自我调控能力,但系统遭到破坏后的恢复能力极差。今日高寒草甸的大面积退化,是人类所赋加于草地的承载力远超过其承载力阈值而导致系统稳定性崩溃的结果。     

Changes in plant diversity,biomass and soil C,in alpine meadows at different degradation stages in the headwater region of three rivers,China

Field surveys and experiment analyses were applied to detect the relationships between plant diversity, community biomass and soil resources at different degradation successional stages in the headwater region of three rivers in an alpine meadow. The chronosequence approach (space‐for‐time substitution) is a viable tool for obtaining integrated information within successional studies. The experimental plots were located in the Guoluo area, which is part of the source region for the Yangtze and Yellow Rivers. The results showed not only that the quantities of roots and soil that are ‘carriers’ for cultivating soil roots were altered not only by disturbance (including overgrazing) and environmental factors but also that the proportion of the rhizome to soil at the 0–10 cm soil layer was enhanced by disturbance in heavy degradation. The plant community composition changed, and the number of plant species and the proportions of fine forage decreased. Moreover, soil fertility levels decreased remarkably, and the soil was degenerated. Plant community biomass levels at different degradation successional stages affected the soil microbial biomass carbon, soil organic carbon and also affected soil fertility conditions. Soil organic carbon and soil total nitrogen declined with grassland degeneration, and the distribution of soil organic carbon was influenced greatly. The alpine species Kobresia pygmaea was at different degradation successional stages, and the plant community biomass was significantly related to soil nutrients. In the positive successional series, the composition of plant functional groups became complex gradually, plant species richness was gradually enhanced, and the change in the composition of each plant functional group also reflected the restoration degree plant community structure. Copyright © 2008 John Wiley & Sons, Ltd.     

放牧对小嵩草草甸土壤酶活性及土壤环境因素的影响

观测了放牧对高寒小嵩草草甸土壤酶活性及土壤环境因素的影响,结果表明:①随着放牧压力的增大,植被盖度、地上生物量、土壤有机质、全氮、硝态氮、全磷、有效磷、土壤水分明显下降,而地下生物量、土壤容重、pH及根土比呈现增大趋势,不同放牧处理间植物群落特征及土壤理化特性显示出明显的差异(P0.05);②纤维素分解酶、多酚氧化酶、脲酶、蛋白酶、碱性磷酸酶和蔗糖酶活性均随放牧压力增大而下降,只有过氧化氢酶以轻牧最高,各处理间上述土壤酶活性差异程度不同;③随着土壤深度的增加,土壤水分含量、地下生物量、根土比、土壤有机质及氮、磷养分等明显下降,而土壤容重和pH逐渐增大,且不同层次之间存在显著的差异(P0.05);④除过氧化氢酶和多酚氧化酶外,其它土壤酶活性随土壤深度的加深显著减小。     

The biogeochemistry of phosphorus across an alpine topographic/snow gradient

Phosphorus (P) availability has generally been assumed to be the limiting or co-limiting factor for plant growth in alpine environments. To test this assumption, the biogeochemistry of phosphorus (P) along an alpine topographic/snow gradient located on Niwot Ridge, Colorado Front Range was studied in the context of P limitation for plant growth. We measured the various P pools using a selective extraction procedure, determined sorption parameters, and quantified P availability indices. The topographic/snow gradient at Niwot Ridge is divided by the aspect and slope position in relation to the dominant westerly winds into leeward-sloping, windward-sloping and generally level sites. Our study found that the snow-melting gradient along the alpine transect greatly affected the antecedent soil moisture, which in turn, controlled the spatial pattern of the major soil attributes such as texture, OC, weathering index, bulk density, non-labile and labile P pools and P availability. The level sites exhibited the highest concentration of organically bound P (1056±75 mg/kg), labile P (315±32 mg/kg), and P in soil solutions corrected for soil adsorption capacity (field condition, 4.9±4.1 mg/l and saturated paste, 8.0±7.5 mg/l). Results of correlation analysis between the various P pools and aboveground biomass of different plant groups suggests that a high level of available P provides a growing advantage to only certain alpine plants and is not a good indicator of the spatial distribution of total aboveground biomass.     

青藏高原不同植被类型土壤微生物数量及影响因子

应用稀释平板法对青藏高原不同植被土壤0~25 cm土层的细菌、真菌和放线菌的数量特征进行对比研究。结果表明:植被类型、温度、土壤理化性质都影响微生物数量。不同植被类型下,微生物数量未达显著性差异,但是藏嵩草草甸和沼泽草甸的土壤微生物数量要大于其他植被类型。其中、灌丛草甸强烈的抑制细菌的生长,真菌对植被类型和温度最为敏感。不同植被下的土壤理化性质差异性显著,土壤理化性质与微生物数量显著相关,较适的土壤全氮(6.96～15.72 g kg-1)、磷和土壤有机质(302.41~367.79 g kg-1)促进土壤微生物的生长;高含量的磷不利于真菌、细菌和放线菌的生长。