Impact of Cloud on Net Ecosystem CO2 Exchange of Alpine Meadow in Tibetan Plateau

Meteorological elements and CO2 fluxes over alpine meadow ecosystem were observed continuously from 2004 to 2005in Damxung Alpine Meadow Flux Station,China Flux Network.Based on the eddy covariance CO2 fluxes and meteorological data obtained,the relationships among the CO2 fluxes,the cloud amount,and the meteorological factors in alpine meadow ecosystem were explored and analyzed.Some conclusions can be drawn from the discussion with previous researches as following:(1)the cloud amount can affect the net ecosystem CO2 exchange(NEE)of alpine meadow on Tibetan Plateau;(2)the soil temperature sensitive to the cloud amount,is a major environmental controlling factor for NEE,and closely relates to the maximum of NEE.In the morning period with large cloud amount,the NEE reaches its maximum when the clearness index ranges from 0.5 to 0.7; yet in the afternoon it comes to the maximum with the index from 0.2 to 0.35.The span of soil temperature covers from 12 to 15℃ as the NEE at its highest;(3)the scatterplots between NEE and photosynthetic available radiation(PAR)was a significant inverse triangle in the clear day,two different kinds of concave curves in the cloudy day,and strongly convergent rectangular hyperbola in the overcast day.These differences were controlled by the changes of light radiation and soil temperature.     

高原牧区自然生态价值的测算——以四川省甘孜藏族自治州新龙县为例

自然生态系统提供人类需要的各种服务,有广泛的使用价值,其中生态服务功能,即无形资产的价值最为重要。本文对新龙县环境的特殊性进行了分析,根据影响生态价值的相关因素,计算了新龙县天然林和天然草地的生态服务功能平均价值,并进一步计算出新龙县1999~2003年受到保护和管理的天然林和天然草地的生态服务功能价值。结果显示,新龙县天然林的生态服务功能平均价值为11837元/hm2,草地为7915元/hm2,1999~2003年,新龙县生态服务功能价值增加值占调整后GDP的比重高达65%~85%。但这部分价值长期未得到统计和合理的补偿,为实现流域环境和经济的可持续发展,建议建立国家、地方、区域、行业多层次的补偿系统,同时逐步完善市场机制。     

青藏高原东缘的隆升及其水系的响应

本文基于ASTER GDEM数据,采用简单数学函数拟合龙门山地区15条河流的河流纵剖面形态,并结合基岩水力侵蚀模型来分析龙门山不同段落的地形形态特征。初步获得以下几点认识:(1)通过对龙门山地区河流纵剖面的分析,龙门山整体上具有较强的隆升速率,导致这一地区强烈的河流侵蚀作用;(2)龙门山中段和南段的河流双对数图以上凸型为主,说明该区域未达到均衡状态,处于前均衡期;(3)龙门山北段的河流双对数图呈直线形态,说明该区域达到均衡状态,处于均衡期;(4)龙门山中段和南段具有更强的构造活动性、更高的隆升速率,控制了该地区地貌、水系演化过程,并且导致这一地区容易发生地质灾害。     

The pika and the watershed: The impact of small mammal poisoning on the ecohydrology of the Qinghai-Tibetan Plateau

With approximately 20 % of the world’s population living in its downstream watersheds, the Qinghai-Tibetan Plateau (QTP) is considered “Asia’s Water Tower.” However, grasslands of the QTP, where most of Asia’s great rivers originate, are becoming increasingly degraded, which leads to elevated population densities of a native small mammal, the plateau pika (Ochotona curzoniae). As a result pikas have been characterized as a pest leading to wide-spread poisoning campaigns in an attempt to restore grassland quality. A contrary view is that pikas are a keystone species for biodiversity and that their burrowing activity provides a critical ecosystem service by increasing the infiltration rate of water, hence reducing overland flow. We demonstrate that poisoning plateau pikas significantly reduces infiltration rate of water across the QTP creating the potential for watershed-level impacts. Our results demonstrate the importance of burrowing mammals as ecosystem engineers, particularly with regard to their influence on hydrological functioning.     

黄土高原丘陵沟壑区脆弱农业生态系统服务评价——以安塞县为例

论文以典型黄土高原丘陵沟壑区安塞县为例,运用市场价值法、替代工程法、影子价格法、机会成本法等方法对其境内7种不同类型农业生态系统的保持土壤(Es)、涵养水分(Ew)、固定CO²和释放O²(Ea)、维持营养物质循环(En)、净化环境(Ee)等服务功能进行了价值核算,初步估算出安塞县生态系统各服务功能的价值总量为3169870.46×10⁴元,是其农林产品服务价值(Vp)的170倍。这一方面表明脆弱生态系统依然担当了重要的生态系统服务功能,为其经济生产力提供了巨大的生态服务。各种服务价值的大小依次为En(占89.85%)、Ew(占4.39%)、Ea(占4.18%)、Vp(占0.58%)、Es(占0.81%)、Ee(占0.18%)。另一方面也充分反映出在该地区“生态生产力”与“经济生产力”严重失衡。     

Carbonaceous matter in glacier at the headwaters of the Yangtze River: Concentration, sources and fractionation during the melting process

Carbonaceous matter has an important impact on glacial retreat in the Tibetan Plateau, further affecting the water resource supply. However, the related studies on carbonaceous matter are still scarce in Geladaindong (GLDD) region, the source of the Yangtze River. Therefore, the concentration, source and variations of carbonaceous matter at Ganglongjiama (GLJM) glacier in GLDD region were investigated during the melting period in 2017, which could deepen our understanding on carbonaceous matter contribution to glacier melting. The results showed that dissolved organic carbon (DOC) concentration of snowpit samples (283?±?200?μg/L) was much lower than that of precipitation samples (624?±?361?μg/L), indicating that large parts of DOC could be rapidly leached from the snowpit during the melting process. In contrast, refractory black carbon (rBC) concentration measured by Single Particle Soot Photometer of snowpit samples (4.27?±?3.15?μg/L) was much higher than that of precipitation samples (0.97?±?0.49?μg/L). Similarly, DOC with high mass absorption cross-section measured at 365?nm value was also likely to enrich in snowpit during the melting process. In addition, it was found that both rBC and DOC with high light-absorbing ability began to leach from the snowpit when melting process became stronger. Therefore, rBC and DOC with high light-absorbing ability exhibited similar behavior during the melting process. Based on relationship among DOC, rBC and K⁺ in precipitation, the main source of carbonaceous matter in GLJM glacier was biomass burning during the study period.     

陕北黄土高原土壤性质及其生态化学计量的纬度变化特征

为了研究不同纬度下土壤的生态化学计量特征,为黄土高原退化生态系统的植被恢复与重建提供理论依据,通过采集黄土高原陕北地区不同纬度下5 个典型植被区的34 个典型土样,测定并分析土壤养分及生态化学计量指标随纬度和植被的变化特征。结果表明,从南到北土壤碱性逐渐增强;土壤容重逐渐增大;土壤速效钾、硝态氮、铵态氮等速效养分逐渐降低,纬度变异性较大;土壤速效磷纬度变异性小。土壤有机碳、土壤全氮、土壤全磷表现出一致的变化规律,随着纬度的增加逐渐降低,变异性较大,表层土壤大于下层土壤。土壤速效养分也表现出表层土壤大于下层土壤,而土壤容重及土壤pH值表现出下层土壤大于表层土壤。0~5 cm土层土壤的碳氮比(C:N)、碳磷比(C:P)、氮磷比(N:P)分别为8.79~22.00、9.91~35.92、1.06~3.25,5~20 cm土层土壤的分别为8.02~21.03、7.36~24.01、0.82~2.22。土壤的C:N受气候变化影响较小,在黄土高原陕北地区随纬度的升高无明显的变化;而土壤C:P、N:P变异性较大,随着纬度的升高显著下降。随着植被的恢复土壤碳氮磷等养分逐渐累积,森林植被明显高于荒漠植被及沙区植被。土壤有机碳与全氮、全磷之间存在极显著的正相关,C:N 与N:P 存在极显著的正相关,与C:P 存在显著的负相关,C:P 与N:P 存在极显著的正相关。黄土高原土壤C:N较为稳定,不随纬度变化;随着植被的恢复,相对于高纬度地区,低纬度地区更容易缺磷;高纬度地区的植被更容易受到N含量的限制,因此对于该区域应该更加注重N肥的施用。     

黄土高原地区森林植被生态需水研究

水土流失是黄土高原面临的主要生态问题,而退耕还林还草、恢复植被是治理水土流失、改善生态环境的必然选择.但黄土高原位于干旱半干旱地区,水资源匮乏是影响该地区植被生态建设的根本因子.因此,植被生态需水研究对于该地区的生态环境建设具有极其重要的意义.本文根据最新遥感图像资料,在GIS支持下,计算了黄土高原地区现有林地生长季的最小生态需水量和适宜生态需水量,其结果分别为262.49×10⁸ m³和421.34×10⁸ m³.除去降雨对林地耗水的补给外,以最小生态需水量为标准,则黄土高原地区在生长季发生水分亏缺的林地面积为7 639.09 km²,占现有林地总面积的9.1%,亏缺水量为4.77×10⁸ m³;以适宜生态需水量为标准,则有57.7%的现有林地在生长季中发生水分亏缺,亏缺水量为58.55×10⁸ m³.     

基于灰关联的坝地分层淤积量与侵蚀性降雨响应研究

论文在全面调查陕北黄土高原淤地坝的基础上,选取典型淤地坝挖取剖面,进行分层测量取样,利用库容曲线和实测各淤积层的厚度求得各层泥沙淤积量,根据黄土高原暴雨产沙过程原理及淤积过程降雨资料,反演各淤积层所对应的侵蚀性降雨。运用灰色关联分析法,分析计算了坝地泥沙淤积量和侵蚀性降雨的4个指标(降雨侵蚀力R、降雨量P、最大30分钟降雨强度I30、平均降雨强度I)之间的关联度。研究结果表明:侵蚀性降雨4个指标中,降雨侵蚀力R和坝地泥沙淤积量的关系最为密切,降雨量P对淤积量的影响次之,最大30分钟降雨强度I30和平均降雨强度I对淤积量的影响最小;并且建立了坝地泥沙淤积量与降雨侵蚀力R和降雨量P的二元线性回归方程。     

长江源区大气降水化学特征及离子来源

基于长江源区冬克玛底流域2013年6～9月采集的64个降水样品,分析了降水的pH值、电导率及离子浓度特征,并应用因子分析、相关分析、富集因子及后向轨迹法,讨论了降水离子主要来源及其与大气环流的联系.结果表明,长江源区冬克玛底流域降水pH值变化范围为5. 26～9. 25,加权平均值为6. 70;电导率变化范围为0. 23～28. 70μS·cm-1,加权平均值为3. 45μS·cm-1,低于瓦里关全球大气本底站降水电导率;总离子浓度变化范围为7. 0～376. 9μeq·L-1,平均总浓度仅为40. 8μeq·L-1;各离子加权平均浓度大小顺序为:HCO_3~- NH_4~+ Ca~(2+) NO_3~- SO_4~(2-) Na~+ Cl~- K~+ Mg~(2+); HCO_3~-、NH_4~+、Ca~(2+)和NO_3~-是降水中的主要离子,占总离子浓度的74. 75%;相对酸度(FA)分析表明,有97. 8%的降水酸度被碱性物质中和,同时中和因子(NF)分析表明NH_4~+和Ca~(2+)对降水酸性的中和起主导作用;研究区降水离子主要来自陆源的贡献,而来自海源的输入则相对较少;结合气团的后向轨迹分析发现,不同来源的总离子浓度差异明显,其加权平均浓度大小顺序为:局地源西风源季风源,表明不同的大气环流背景和气团来源对降水化学组成具有重要影响.长江源区大气降水受人类活动影响较小,其降水化学特征一定程度上可以代表偏远地区的大气质量状况和本底值.研究结果能够为长江源区水质的保护以及为评估人类活动对该区域大气环境的影响提供科学依据.