黄河源高寒草原下垫面土壤冻融过程中陆-气间的水热交换特征分析

高寒草原水热交换的季节性特征显著,土壤冻融过程对地-气水热交换有着重要的影响.本文利用黄河源区汤岔玛小流域2014年5月至2015年5月陆面过程观测数据,将土壤冻融过程划分为完全融化(TT)和完全冻结(FF)两种状态与融冻(T-F)和冻融(F-T)两个过程,并分析了期间高寒草原下垫面净辐射、感热通量、潜热通量和地表热通...     

青藏高原多年冻土区沼泽草甸土壤CH_4产生速率研究

用实验室培养法对青藏高原多年冻土区沼泽草甸土壤不同温度条件下的CH4产生速率进行了研究.结果表明：CH4产生速率与温度之间呈现显著的指数关系,整个土壤剖面平均CH4生成速率和CH4生成速率初始值随温度的变化具有显著的相似性,都表现出随温度的升高而增加规律,0℃、5℃、18℃时的CH4生成速率分别是-18℃时的5.7、1...     

天山北坡三工河流域中山带森林发育与气候土壤的关系

开展干旱区山地森林发育状况及其土壤因素影响的分析,对干旱区乃至全球山地森林带的成因研究具有重要的理论意义。以天山北坡三工河流域为研究区,主要利用森林调查与遥感影像数据,确定该流域森林带的分布状况,并结合流域气象与土壤采样数据,重点分析气候土壤因素对森林发育的影响。结果表明:1.该流域森林带位于海拔1 510～2 720 m,胸径与树高随海拔增加呈双峰曲线;其中胸径两个峰值分别位于约海拔2 000 m与2 550m,而树高峰值分别为海拔2 100 m与2 600 m,均稍高于胸径的峰值海拔高度;2.在森林带内,年均温随海拔高度增加呈线性下降趋势,最冷月均温(1月)则表现先增加后减小趋势;与其他地区相比,该流域高山林线年均温较高,最冷月均温相差较大,而最热月均温差异不明显;年降水量呈先增加后减小的趋势,且在海拔2 000 m左右达到最大值。土壤属性随海拔递增呈规律性的变化趋势:森林带内海拔约2 000～2 700 m树木发育较好,其有机质、全磷及全氮含量较高;CaCO3,pH值及电导率最小值与海拔2 000 m的最大降水带恰好吻合;土壤A层(0～10 cm)有机质、全磷及全氮含量与B(10～30 cm)、C(>3...     

藏东南色季拉山急尖长苞冷杉林线地带地上生物量随海拔的变化特征

从亚高山森林到高山林线,逐渐严酷的生长环境影响了生物量的积累和分配.本研究采用相对生长法和样方收获法估算了藏东南色季拉山急尖长苞冷杉林在禾同海拔(4 190 m,4 270 m和4 326 m)的地上生物量,分析了群落中不同层次地上生物量、各器官生物量及其分配比例随海拔的变化格局.结果表明:1.急尖长苞冷杉群落地上生物量在181～284 t/hm2之间,其中,乔木层在11～-248 t/hm2,灌木层为35～62 t/hm2,草本层为0.9～1.5 t/hm2;2.群落地上生物量随海拔升高急剧降低,降低的平均幅度为73.1 t/(hm2·100 m);3.随海拔升高,群落地上生物量分配到非光合器官(树干和枝条)的比例显著降低,分配到叶的比例呈增加趋势.随海拔的增加,急尖长苞冷杉群落通过增加叶生物量所占比例(高叶寿命)以延长养分在植物体内的存留时间,提高生态系统的养分利用效率,从而适应高海拔地区的低温胁迫环境.     

黄河源区高寒草地-大气间水热交换通量特征

利用黄河源区玛曲观测站2016年涡动相关系统和微气象梯度塔观测资料,分析了高寒草地 大气间水热交换通量的特征。结果表明：夜间地表各通量值很小,净辐射和感热通量为负值,潜热通量的值较小但始终为正。日出后随着太阳辐射和地表加热作用各通量迅速增大,在14时左右达到峰值。暖季（6—8月）夜间感热通量占净辐射的比例(H/Rn)高于感潜通量占净辐射的比例(LE/Rn),日出后LE/Rn开始升高而H/Rn减小,日间LE/Rn大于H/Rn。冷季（12月—次年2月）H/Rn始终大于LE/Rn,感热通量在冷季的能量分配中占据主导地位。暖季LE/Rn、H/Rn均随土壤温度升高而升高。冷季H/Rn与5 cm深度土壤温度表现出了更为明显的二次关系,随着温度升高先降低后升高,当温度小于-7 ℃时H/Rn降低,大于-6 ℃时H/Rn增大。暖季H/Rn随着土壤湿度增大先降低后升高,LE/Rn先升高后降低。在0—1.5 kPa,暖季饱和水汽压差与LE/Rn、H/Rn均呈线性关系,并随着饱和水汽压差增大,LE/Rn增大而H/Rn减小;1.5 kPa之后,LE/Rn、H/Rn变化特征均保持其原有趋势。     

祁连山南坡灌丛草甸生物量变化与水热因子的关系研究

通过野外调研和室内实验,研究了祁连山南坡灌丛草甸地上生物量的生长季变化,并对地上生物量与水热因子的关系进行了探讨。结果表明：在不同区域群落结构有所不同,覆盖度越低,上层和下层的植物高度越低,丰富度和多样性越小。但均匀度还受草场退化阶段的影响,群落结构相对稳定,植物的均匀度越高;地上生物量的年内变化是单峰曲线,乌鞘岭和门源的地上生物量在7月份最大,祁连和野牛沟的地上生物量在9月份最大;地上生物量的积累与前1月和前2月的气温和降水正相关,与前4月的气温也正相关,并且对气温变化的敏感性大于降水,但与地温和土壤水分的相关性不明显,前1月表层地温较高对地上生物量的积累有积极作用;对于地上生物量积累,日气温、日相对湿度、降水量有直接正向作用,而日最高气温、日最低气温、日水汽压有直接负向作用,5 cm、20 cm地温和0~10 cm、20~30 cm土壤水分也有直接正向作用,而10 cm地温和10~20 cm土壤水分也有直接负向作用。     

CO2 processes in an alpine grassland ecosystem on the Tibetan Plateau

In this paper, the CO2 concentrations profile from 1.5 m depth in soil to 32 m height in atmosphere were measured from July 2000 to July 2001 in an alpine grassland ecosystem located in the permafrost area on the Tibetan Plateau, which revealed that CO2 concentrations varied greatly during this study period. Mean concentrations during the whole experiment in the atmosphere were absolutely lower than the CO2 concentrations in soil, which resulted in CO2 emissions from the alpine steppe soil to the atmosphere. The highest CO2 concentration was found at a depth of 1.5 m in soil while the lowest CO2 concentration occurred in the atmosphere. Mean CO2 concentrations in soil generally increased with depth. This was the compositive influence of the increasing soil moistures and decreasing soil pH, which induced the increasing biological activities with depth. Temporally, the CO2 concentrations at different layers in air remained a more steady state because of the atmospheric turbulent milking. During the seasonal variations, CO2 concentrations at surface soil interface showed symmetrical patterns, with the lowest accumulation of CO2 occurring in the late winter and the highest CO2 concentration in the growing seasons.     

Petrology of the Yugu peridotites in the Gyeonggi Massif,South Korea: Implications for its origin and hydration process

Peridotites exposed in the Yugu area in the Gyeonggi Massif, South Korea, near the boundary with the Okcheon Belt, exhibit mylonitic to strongly porphyroclastic textures, and are mostly spinel lherzolites. Subordinate dunites, harzburgites, and websterites are associated with the lherzolites. Amphiboles, often zoned from hornblende in the core to tremolite in the rim, are found only as neoblasts. Porphyroclasts have recorded equilibrium temperatures of about 1000°C, whereas neoblasts denote lower temperatures, about 800°C. Olivines are Fo_90–91 in lherzolites and Fo₉₁ in a dunite and a harzburgite. The Cr# (= Cr/(Cr + Al) atomic ratio) of spinels varies together with the Fo of olivines, being from 0.1 to 0.3 in lherzolites and around 0.5 in the dunite and harzburgite. The Na₂O content of clinopyroxene porphyroclasts is relatively low, around 0.3 to 0.5 wt% in the most fertile lherzolite. The Yugu peridotites are similar in porphyroclast mineral chemistry not to continental spinel peridotites but to sub‐arc or abyssal peridotites. Textural and mineralogical characteristics indicate the successive cooling with hydration from the upper mantle to crustal conditions for the Yugu peridotites. Almost all clinopyroxenes and amphiboles show the same U‐shaped rare earth element (REE) patterns although the level is up to ten times higher for the latter. The hydration was associated with enrichment in light REE, resulting from either a slab‐derived fluid or a fluid circulating in the crust. The mantle‐wedge or abyssal peridotites were emplaced into the continental crust as the Yugu peridotite body during collision of continents to form a high‐pressure metamorphic belt in the Gyeonggi Massif. The peridotites from the Gyeonggi Massif exhibit lower‐pressure equilibration than peridotites, with or without garnets, from the Dabie–Sulu Collision Belt, China, which is possibly a westward extension of the Gyeonggi Massif.     

Soil organic carbon and nitrogen content of density fractions and effect of meadow degradation to soil carbon and nitrogen of fractions in alpine Kobresia meadow

This research was conducted on the non-disturbed native alpine Kobresia meadow(YF) and the severely degraded meadow(SDL) of Dari County of Qinghai Province.By a density fractionation approach,each soil sample was divided into two fractions:light fraction(LF) and heavy fraction(HF).The obtained fractions were analyzed for organic carbon(OC) and nitrogen(N) concentrations.The results showed:(1) the OC concentration in HF and LF was 3.84% and 28.63% respectively while the nitrogen concentration in HF and LF wa...