高寒退化草地中垫状点地梅的生态系统工程师作用

垫状植物是高寒地区广泛分布的一类具有特殊形态的植物,被称为高寒生态系统工程师,其在高寒退化草地中的作用如何?本研究以位于西藏当雄念青唐古拉山脉南坡4500m的一处高寒退化草地为例,调查了垫状点地梅覆盖区域内外的物种多样性、土壤养分以及水分的差异。结果表明:垫状点地梅可以显著改善土壤养分,提高幅度大约为16%-48%,其中有机质和总氮(N)分别增加了16.2%和18.9%;局部土壤含水量提高约12%;样方内的物种丰富度(S)、Shannon-Wiener指数(H)和Simpson指数(D)都随着垫状点地梅盖度的增加而呈增加的趋势。垫状点地梅在退化草地中具有显著的改善土壤微环境和提高群落物种多样性的作用,应加强保育以促进高寒退化草地的恢复。     

Variations in soil properties and their effect on subsurface biomass distribution in four alpine meadows of the hinterland of the Tibetan Plateau of China

To understand and predict the role of soils in changes in alpine meadow ecosystems during climate warming, soil monoliths, extending from the surface to the deepest roots, were collected from Carex moorcroftii, Kobresia humilis, mixed grass, and Kobresia pygmaea alpine meadows in the hinterland of the Tibetan Plateau, China. The monoliths were used to measure the distribution with depth of biomass, soil grain size, soil nutrient levels, and soil moisture. With the exception of the K. pygmaea meadow, the percentages of gravel and coarse sand in the soils were high, ranging from 37.7 to 57.8% for gravel, and from 18.7 to 27.9% for coarse sand. The texture was finest in the upper 10 cm soil layer, and generally became coarser with increasing depth. Soil nutrients were concentrated in the top 15 cm soil layer, especially in the top 10 cm. Soil water content was low, ranging from 3 to 28.4%. Most of the subsurface biomass was in the top 10 cm, with concentrations of 79.8% in the K. humilis meadow, 77.6% in the mixed grass meadow, and 62.3% in the C. moorcroftii meadow. Owing to deeper root penetration, the concentration of subsurface biomass in the upper 10 cm of K. pygmaea soil was only 41.7%. The subsurface biomass content decreased exponentially with depth; this is attributed to the increase in grain size and decrease in soil nutrient levels with depth. Soil water is not a primary factor influencing the vertical and spatial distribution of subsurface biomass in the study area. The lack of fine material and of soil nutrients resulted in low surficial and subsurface biomass everywhere.     

某中外合作企业在地质勘探中的环境保护措施

环境保护是我国的一项基本国策,地质勘探是矿产资源开发的必由之路,在地质勘探过程中切实保护好生态环境,是我们面临的一个十分严峻的问题.某中外矿业合作勘探部在新疆伊利地区地质勘探中采取了一系列的环境保护措施,按照该措施实施的先后顺序及其执行情况作了较细致的介绍,该措施是地质勘探阶段一套较为全面的环境保护管理办法,在当地环境保护方面起到了积极的作用.     

2009/2010年黄河源区高寒草甸下垫面能量平衡特征分析

以青藏高原黄河源玛多为实验区, 基于TRM-ZS1气象生态环境监测仪2009年11月1日至2010年10月31日辐射及能量通量观测数据, 采用波文比能量平衡法, 进行了该区域潜热和感热通量的估算, 分析了黄河源区高寒草甸下垫面辐射收支, 潜热、 感热和土壤热通量在不同季节的分配, 对该区域冬季地面加热场强度的变化进行了研究.结果表明: 该区域总辐射、 净辐射较强, 总辐射平均日积分值为18.06 MJ·m^-2·d^-1, 净辐射平均日积分值5.95 MJ·m^-2·d^-1, 曾观测到高达979.5 W·m^-2的净辐射通量.全年地表平均反射率为0.30, 接近于荒漠和半荒漠下垫面的反射率.植物生长季土壤湿度和冬、 春季地面积雪是影响该区域地表反射率的两个最主要因素.该区域感热通量年积分值为742.68 MJ·m^-2·a^-1, 潜热通量年积分值为1 388.58 MJ·m²·a^-1, 全年中地表以潜热方式传递热量为主.分季节分析, 冬季感热潜热强度相当, 春季以感热为主, 夏秋季则以潜热为主.土壤热通量年积分值为38.06 MJ·m^-2·a^-1, 全年热通量在热量平衡中约占1.8%, 但季节分配不平衡, 在冬季, 有|G|>H+LE, 土壤热通量是热平衡最大的分量.该区域地表全年向大气释放热量, 地表对大气而言是热源.     

冻融循环对青藏高原腹地不同生态系统土壤细菌群落结构的影响

通过构建16S rRNA基因克隆文库,研究了冻融循环对青藏高原腹地北麓河的高寒沼泽草甸和高寒沙化草原两种不同生态系统土壤细菌群落结构的影响. 结果表明: α-、 β-、 γ- 和δ-变形菌门(α-、 β-、 γ- 和δ-Proteobacteria)、 酸杆菌门(Acidobacteria)、 放线菌门(Actinobacteria)、 拟杆菌门(Bacteroidetes)和浮霉菌门(Planctomycetes)为两个生态系统土壤共有的细菌类群, 其中, 变形菌门、 酸杆菌门及浮霉菌门细菌为研究区域优势菌, 而厚壁菌门(Firmicutes)为高寒沼泽草甸土壤所特有, 疣微菌门(Verrucomicrobia)和绿弯菌门(Chloroflexi)细菌是高寒沙化草原土壤特有的细菌类群, 表明青藏高原腹地两种生态系统土壤具有丰富的细菌多样性. 冻融循环会降低区域土壤的细菌多样性, 随冻融循环, 高寒沼泽草甸和高寒沙化草原生态系统土壤放线菌门丰度均呈现下降趋势, 但大部分细菌随冻融循环的变化在两种生态类型中呈现不同的变化规律, 结果说明冻融循环对于不同生态系统土壤细菌群落结构的影响既存在相似性, 也存在着较大的差异.     

青藏高原多年冻土区高寒草甸植物种群物候学定量研究

采用青藏高原腹地北麓河多年冻土区高寒草甸14种代表性植物种群2009年和2010年两个生长季的物候观测资料, 进行植物种群物候学特征的定量分析, 划分物候类型并指出影响不同物候期的环境因子主次. 结果表明: 营养期和结实期的物候指数都较大, 分别为32.70和24.39, 其他物候期则相对较小; 整个生长期持续天数较短, 为155 d左右. 14种植物可划分为3种类型和6大类群. 在营养期和整个生长期, 与物候变化最为密切的环境因子为降水量, 其次为日照时数, 温度居第三; 而影响其他物候期的因子均以日照时数为主, 降水量和温度依次居后.     

Effects of elevated air temperatures on soil thermal and hydrologic processes in the active layer in an alpine meadow ecosystem of the Qinghai-Tibet Plateau

In this study,effects of elevated air temperatures on thermal and hydrologic process of the shallow soil in the active layer were investigated. Open-top chambers(OTCs)were utilized to increase air temperatures 1-2℃ in OTC-1 and 3-5℃ in OTC-2 in the alpine meadow ecosystem on the Qinghai- Tibetan Plateau.Results show that the annual air temperatures under OTC-1 and OTC-2 were 1.21℃ and 3.62℃ higher than the Control,respectively.The entirely-frozen period of shallow soil in the active layer was shortened and the fully thawed period was prolonged with temperature increase.The maximum penetration depth and duration of the negative isotherm during the entirely-frozen period decreased, and soil freezing was retarded in the local scope of the soil profile when temperature increased.Meanwhile, the positive isotherm during the fully-thawed period increased,and the soil thawing was accelerated.Soil moisture under different manipulations decreased with the temperature increase at the same depth. During the early freezing period and the early fully- thawed period,the maximum soil moisture under the Control manipulation was at 0.2 m deep,whereas under OTC-1 and OTC-2 manipulations,the maximum soil moisture were at 0.4-0.5 m deep. These results indicate that elevated temperatures led to a decrease of the moisture in the surface soil.The coupled relationship between soil temperature and moisture was significantly affected by the temperature increase.During the freezing and thawing processes, the soil temperature and moisture under different manipulations fit the regression model given by the equationθV=a/{1+exp[b(TS+c)]}+d.     

The morphology and hydrology of small spring-dominated channels

Small, low order channels located in wet meadows along the Mogollon Rim of northern Arizona that receive the bulk of their flow from spring discharge exhibit a morphology that differs markedly from channels that receive the bulk of their flow from runoff. These small, spring-dominated channels generally have dense vegetation cover, vertical (or near vertical) banks with flat channel beds that are armored with clasts up to 60 mm. Clasts armoring the spring-dominated channels become mobile at 45 to 85% of the bankfull depth. The lack of fine-grained material in the bed of the spring-dominated channels reflects the small drainage size, lack of fine grain input from the spring, and winnowing affect of the consistent discharge. Minor amounts of large woody debris were present in some of the spring-dominated channels, however, unlike previous studies it does not appear to play a role in the spring-dominated channel morphology. Sinuosity values for spring-dominated channels averaged 1.19, while the average sinuosity values for the runoff-dominated channels, 1.08, were significantly lower. Measured width-to-depth ratios averaged 2.4 in the spring-dominated channels, much lower than the average ratio of 11.6 found for the runoff-dominated channels. The standard deviation of width-to-depth ratios was higher for runoff-dominated channels, reflecting a more variable channel profile. A third channel type, here referred to as hybrid channels, receive significant flow from both springs and runoff. These channels have characteristics that fall between spring-dominated and runoff-dominated channels.Elevation, gradient, organic matter content, and sediment grain size distribution of the wet meadows in which the channels are formed do not exhibit significant differences between channel types, suggesting that these factors are not responsible for the observed differences in channel morphologies. The major differences in controls on the channel morphology found between the spring-dominated and runoff-dominated channels are the discharge regime and the sediment input. The hydrology unique to the spring-dominated channels and the lack of fine-grained sediment input combine to create the observed differences.     

季节性放牧对黄河源区高寒草甸植被耗水量及水分利用效率的影响

研究季节性放牧对植被耗水量、水分利用效率的影响,是探索如何提高高寒草甸水源涵养能力的重要内容之一。以青藏高原三江源高寒草甸季节性放牧样地与自然放牧样地为研究对象,分析了季节性放牧和自然放牧条件下高寒草甸植被耗水量、水分盈亏量、水分利用效率（WUE）的动态变化及其与环境因素的关系。结果表明：在植被生长季（5-9月）,季节性放牧样地和自然放牧样地植被耗水量在5月开始增加, 7月达最高,分别为160.94 mm和145.96 mm,季节性放牧样地植被总耗水量（395.52 mm）比自然放牧样地（348.14 mm）高13.61%。生长季平均来看,季节性放牧样地和自然放牧样地5-9月水分正盈余,分别为13.58 mm和70.96 mm,但在植物生长旺季（8月）略有亏缺。季节性放牧样地和自然放牧样地植被耗水量均与降水量呈弱的正相关关系。季节性放牧样地植被地上净初级生产量（ANPP）、地下净初级生产量（BNPP）和总的净初级生产量（NPP）比自然放牧样地分别高32.54 g·m^-2、5.96 g·m^-2、38.50 g·m^-2,季节性放牧样地ANPP的水分利用效率（WUE）比自然放牧样地高53.85%,而BNPP、NPP的WUE比自然放牧样地分别低13.06%和9.97%。这表明,季节性放牧可提高植被生产量和耗水量,但对高寒草甸WUE的影响因放牧方式不同导致地上、地下生物量分配格局不同而有所差异。     

两个时期若尔盖高原沼泽湿地景观格局的对比研究

以若尔盖高原为研究区,选择1977年的Landsat MSS影像、2007年的Landsat TM影像和研究区90m分辨率的数字地形图为数据源,利用景观生态学方法及遥感和地理信息系统技术,对若尔盖高原1977年和2007年两个时期的沼泽湿地(包括沼泽和沼泽化草甸)景观格局进行了对比研究。结果显示,与1977年相比,2007年研究区沼泽与沼泽化草甸的面积比(沼泽面积/沼泽化草甸面积)发生了明显变化,沼泽与沼泽化草甸的面积比由1977年的1/3减少到2007年的1/7;2007年沼泽面积明显减少,其面积只占沼泽湿地总面积的13%;两个时期,研究区沼泽湿地景观都集中连片分布,聚集度均高于90;与1977年相比,2007年沼泽湿地景观的斑块数减少,景观类型趋于单一,而平均斑块面积和聚集度都在增加;研究区沼泽湿地90%以上分布在坡度小于5°的空间范围内,随着坡度的增大,沼泽湿地的退化程度显著增高;与1977年相比,2007年研究区沼泽湿地景观分布质心发生了一定的空间位移,沼泽质心向西南偏移了3.88km,沼泽化草甸质心向东北偏移了12.35km。