Distribution characteristics of soil organic carbon of alpine meadow in the Eastern Qinghai-Tibet Plateau

A study on the distribution characteristics of soil organic carbon (SOC) in the alpine meadow in the Eastern Qinghai-Tibet Plateau has been carried out. The results indicate that the content of soil organic carbon (C _SOC) in the topsoil of terrace meadow (TM) ((67.16 ± 1.02) g·kg⁻¹) is more than that in the soil of upland meadow (UM) ((63.42 ± 0.65) g·kg⁻¹), while the C _SOC in upland shrubland (US) ((67.49 ± 0.83) g·kg⁻¹) is the most abundant in the scoreh stage (September). From May to September, the C _SOC in the topsoil of UM and US tends to descend, but that of TM tends to ascend. As for the distribution of the C _SOC and the density of SOC in the soil in the three sample areas, the data show that the deeper the soil, the lesser the content and density of SOC. The C _SOC in US is higher than that in TM and UM; the C _SOC in UM is the lowest at 0–10 cm soil depth. The density of SOC in US is always the lowest among UM, TM, and US at 0–40 cm depth, which shows that the storage of carbon in UM is more than that in US in the same range; the carbon pool capacity in UM is higher than that in US in the same range. Biography: ZHANG Wei (1979–), male, Lecturer, research direction: ecology of environment.     

土地利用变化对高寒草甸植物群落结构及物种多样性的影响

以原生高寒嵩草草甸封育系统为对照,研究了不同土地利用对植物群落结构和物种多样性的影响,检验了不同人工重建措施对植被的相对影响程度.研究结果表明:高寒嵩草草甸草地退化导致植被稀疏、覆盖度下降、群落物种组成减少、群落中各功能群的比例发生变化、物种多样性降低.退化草地封育自然恢复7年后,恢复最快的是一年生杂草,其次是禾草类;重度退化草地改建成人工草地7年后,禾本科植物仍然是群落中的优势类群,但原生植被中的优势功能群--莎草类在任何人工草地中没有出现;经相关分析表明,物种多样性指数与均匀度指数呈极显著正相关(P＜0.01),与物种丰富度呈显著正相关(P＜0.05).不同土地利用条件下,各群落之间种相似性系数的变化表明,退化草地经过多年的封育,或经松耙补播后逐步向原生植被方向演替;人工草地逐步向退化演替方向发展.     

夏季高寒沙地乌柳林的水分来源

【目的】共和盆地位于青藏高原的半干旱区,属于典型的高寒沙地,是青海省土地荒漠化最严重的区域之一。乌柳是当地退化草地恢复的主要树种,乌柳林的稳定性是其可持续管理的关键。研究夏季乌柳林的水分来源以分析它们在半干旱区能否维持稳定性。【方法】利用稳定氢、氧同位素技术研究了夏季4个林龄乌柳林的水分来源,比较乌柳林的木质部水分与各潜在水源的稳定氢、氧同位素值,确定7月乌柳林主要利用的水源。【结果】不同林龄乌柳林可利用不同深度的土壤水或地下水。其中,2年生乌柳林主要利用地表下25 cm的土壤水,占总水源的75.5%; 10年生乌柳林主要利用地表下25～75 cm的土壤水和地下水,占总水源的73.9%; 20年生乌柳林主要利用地表下50～75 cm的土壤水和地下水,占总水源的67.7%; 30 年生乌柳林主要利用地表下25 cm的土壤水和地下水,占总水源的69.6%。随着林龄的增加(从10 a到30 a),乌柳林对地下水的依赖性逐渐增强。【结论】乌柳林通过调整水分利用策略来适应共和盆地的半干旱气候。利用稳定的深层土壤水和地下水有助于长期维持乌柳林稳定性,建议将乌柳作为高寒沙地和其他半干旱地区退化植被恢复的主要树种推广。     

川西北高寒草甸生长季土壤氮素动态

研究了川西北高寒草甸生长季土壤氮素变化特征,结果表明:研究区0～40 cm土层在整个生长期内,有机质含量均高于60 g.kg-1,全氮含量高于2.83 g.kg-1,养分含量丰富.浅丘山地草甸土壤氮素随季节变化呈现增加的趋势,植被覆盖变化(浅丘山地灌丛)或退化程度增加(丘前阶地草甸)使得土壤氮素随季节呈现出先减少后缓慢增加的变化,但影响主要表现在0～30 cm土层中,并且越往表层,差异越大.川西北高寒草甸土壤C/N值偏小(<25),利于氮的矿化养分释放.由于研究样地中灌丛的出现,虽然没有引起明显的"沃岛"现象,但加大土壤养分空间异质性的趋势.     

Macroinvertebrate richness is lower in high-elevation lakes vs nearby streams: evidence from Grand Teton National Park,Wyoming

Mountain ecosystems will be strongly impacted by climate change, yet little is known of extant biodiversity in high-elevation lakes, particularly in North America. In this study, we sampled the littoral zone of six alpine and subalpine lakes in Grand Teton National Park (GRTE), Wyoming, to characterise invertebrate diversity and environmental variation in these climate change-threatened ecosystems. Overall, we collected 19 aquatic invertebrate taxa, and found that each lake harboured a unique assemblage of invertebrates despite close geographic proximity in some instances (e.g. less than 5 km). The results of this study complement previous efforts focused on macroinvertebrate diversity of streams in the Teton Range, highlighting much lower diversity in montane lakes vs nearby streams. Taken together, the two studies establish an important baseline understanding of mountain freshwater biodiversity in GRTE. With rapidly changing hydrologic inputs to mountain lakes driven primarily by the recession of alpine glaciers, these results may help target aquatic invertebrates to monitor as climate change affects the region. Moreover, these data clarify habitat factors, both biotic and abiotic, that influence high-elevation lake assemblages of the Teton Range.     

Changes in plant community diversity and aboveground biomass along with altitude within an alpine meadow on the Three-River source region

The grassland is an important component of terrestrial ecosystems and plays a significant role in biodiversity and ecosystem functions.In the present study,the changes of plant species diversity and aboveground biomass productivity were examined along with the altitude in natural alpine grassland in the source region of three rivers on the Qinghai-Tibetan Plateau.Eleven experimental locations were selected with altitudes ranging from 3862 to 4450 m above sea level(a.s.l.).The results indicated that Kobresia pygmaea meadow,Kobresia humilis meadow and Salix cupularis shrub meadow had higher indices of diversity and aboveground biomass.The distribution of species diversity,richness and aboveground biomass showed similarly unimodal patterns across the altitude gradient with the highest indices appeared at mid-altitudes locations.The changing trend of species diversity,richness and evenness also showed significant unimodal patterns with total aboveground biomass,and the highest species diversity occurred at intermediate level of productivities.This research would provide a valuable reference for the protection of grassland biodiversity and maintaining of the grazing ecosystem function in the source region of the Three Rivers.     

川西北高寒草甸土壤呼吸速率日变化及温度影响因子比较

根据远红外气体分析原理,采用Li-6400-09土壤呼吸室和Li-6400光合速率测定仪对川西北高寒草甸土壤呼吸速率日变化进行测定,并同步记录大气温度、0、5、10、15和20 cm地温,探讨温度对土壤呼吸速率的影响.结果表明,在选取的浅丘山地灌丛(US)、浅丘山地草甸(UM)、丘前阶地草甸(TM)3块样地中,土壤呼吸速率日变化均呈单峰型,日均呼吸速率是UM((5.34±0.339)μmol.m-2.s-1)>US((5.14±0.225)μmol.m-2.s-1)>TM((4.49±0.282)μmol.m-2.s-1),差异极显著(P<0.01).大气温度、0和5 cm地温与3块样地土壤呼吸速率相关性最强,以5 cm地温最突出;10 cm地温与呼吸速率相关性较好;15和20 cm地温与呼吸速率相关性很小.基于Q10值,土壤呼吸速率对5 cm地温的变化最敏感,各样地对温度的响应是UM>US>TM.     

祁连山北坡冬季牧场积雪盖度与植被、地形的关系

以祁连山高寒草原为对象,测定4个坡向冬季牧场的坡度、立枯物高度和盖度及积雪盖度,分析积雪盖度与植被和地形特征之间的关系,构建基于植被(立枯物高度和盖度)和地形因素(坡度和坡向)的牧场积雪盖度估测模型,为牧场的管理提供理论依据.通过研究发现:祁连山北坡高寒草原积雪盖度与立枯物高度和盖度呈极显著负相关,与坡度和坡向呈极显著正相关;坡向和坡度与立枯物高度和盖度呈显著负相关,坡向对立枯物积累的负效应比坡度更明显.冬季牧场立枯物盖度对积雪的直接作用最大,坡度通过立枯物盖度对积雪盖度的间接作用其次,坡向和坡度通过立枯物高度对积雪盖度的间接作用显著;坡度对立枯物高度的直接作用高于坡向,其对立枯物盖度的直接作用显著.祁连山高寒草原的积雪盖度可通过植被或/和地形特征的多元线性回归方程很好地估测,基于植被和地形综合因素所建立的最佳积雪盖度估测模型为:SC(%)=70.278+4.210A+0.269S-0.138SLH-0.534SLC(R~2=0.630,P0.001)(式中,A,S,SLH和SLC分别为坡向、坡度(°)、立枯物高度(cm)和盖度(%)).     

青藏高原草地畜牧业生产现状、问题及对策

为科学评估青藏高原草地畜牧业生产现状,对四川省、青海省和西藏自治区的13个乡镇的153户牧户进行了入户调研,综合分析了高寒地区各调研户户均饲草供给、家畜生产、基础设施条件及家庭收支情况,提出了阻碍草地畜牧业可持续发展的饲草供给不足、经济效率低下、基础设施落后、生产技术滞后等关键问题,并提出了相应的应对策略.调研结果可为国家相关部门制定政策法规,促进高寒牧区畜牧业可持续发展,实现牧区生态安全和牧民增产增收提供重要参考.     

地形对贺兰山高山林线分布高度的影响?

运用遥感数据和空间分析技术提取贺兰山高山林线,并结合DEM数据计算相关地形因子,采用相关分析和多元回归分析定量研究不同地形因子对高山林线分布高度的影响.结果表明,贺兰山高山林线上、下边界平均高度分别为3 106和3 022m,主山脊西侧山地高山林线上、下边界分布高度范围和平均高度比东侧略高.在山地两侧影响高山林线上边界高度的地形因子及其贡献率具有差异.南北朝向指数和地形指数对山地西侧高山林线上边界高度变化的相对贡献率分别为56.7%和43.3%;南北朝向指数、地形指数和坡度对东侧高山林线上边界高度变化的相对贡献率分别为50.9%、31.0%和18.1%.坡向是影响贺兰山高山林线分布高度的重要地形因素,而坡面凹凸程度和坡度对高山林线分布高度的影响与其他地形因素具有一定关系.