INTERRELATIONSHIP BETWEEN WATER QUALITY AND GROUNDWATER FLOW DYNAMICS IN A SMALL WETLAND SYSTEM ALONG A SANDY HILL RIDGE

Detailed modelling of the hydrological setting of fen meadows appears to be possible provided that detailed information on geomorphology, hydrochemistry and piezometric heads is available for a number of years. In the Laegieskamp, a small wetland reserve located in the central part of The Netherlands, a piezometric monitoring network was sampled for water quality analysis and piezometric heads between 1986 and 1992. Average yearly discharge and recharge periods were used for FLOWNET calculations. First, the models were used to determine, with the help of information on water quality, the hydrological systems in the study area. Secondly, they were used to define the present and past hydrological setting of a fen meadow in the reserve. The hydrological systems and water quality in the study area have changed considerably over the past 65 years. At present the fen meadow is mainly fed by precipitation. The mineral-rich conditions favouring the fen meadow vegetation are thought to be maintained thanks to a clayey peat layer and an oscillating shallow water body that prevents rapid leaching of minerals. The sulphate content in the fen exhibits a pattern of temporal variation, which is related to the severity of the annual drought. Our study showed that groundwater flow is mainly lateral, instead of the assumed vertical infiltration of groundwater in previous regional studies. This led us to the conclusion that conservation and restoration perspectives are much better than previously expected. The polluted middle, deep groundwater is not a major threat to this fen at the moment. © 1997 John Wiley & Sons, Ltd.     

高寒草甸土壤有机碳储量及其垂直分布特征

青藏高原是全球变化的敏感区。高寒草甸草原是青藏高原上最主要的放牧利用草地资源之一。选择青藏高原东北隅海北站内具有代表性的高寒草甸土壤进行高分辨率采样,测定土壤根系和有机碳含量。研究得出,青藏高原高寒草甸土壤贮存有巨大的根系生物量 (23544.60 kg ha^-1~27947 kg ha^-1) 和土壤有机碳 (21.52 GtC);自然土壤表层 (0~10 cm) 储存了整个剖面土壤有机碳总量的30%左右。比较发现,高寒草甸土壤的有机碳平均贮存量 (23.17×10⁴ kgCha^-1) (0~60 cm) 较相应深度的热带森林土壤、灌丛土壤和草地土壤的有机碳贮存量高约1~5倍多。在全球碳预算研究中,青藏高原高寒草甸土壤有机碳库不可忽视。随着全球变暖,表层土壤有机碳分解释放的CO₂将增加。为了减少高寒草甸生态系统的碳排放,应加强高寒草甸土壤地表覆被的保护,合理种植深根系植物。这对减缓全球大气CO₂浓度升高的速率以及可持续开发高寒草甸的生态服务功能都具有重要意义。     

滇西北亚高山草甸退化梯度上马蹄黄地上形态特征变化

马蹄黄(Spenceria ramalana)是滇西北亚高山草甸的旅游景观资源,其地上形态特征随草甸退化梯度的变化趋势尚少见报道。于2018年7月在香格里拉市调查、对比了3个退化梯度(一级退化,DI;二级退化,DII;无退化对照,CK)上马蹄黄的植株高度、展度、叶片数量、叶片长度、叶片宽度、叶面积、叶片长宽比和生存状态。结果表明:(1)与CK相比,DI和DII梯度上马蹄黄的植株高度、展度、叶片数量、叶片长度、叶片宽度和叶面积均显著减小(P<0.05);(2)DII梯度上马蹄黄的叶片长度、叶片宽度和叶面积显著高于DI梯度(P<0.05);(3)CK、DI和DII中马蹄黄的叶片长宽比分别为3.5±0.3、2.9±0.4和2.3±0.1,叶片形状由倒披针形向倒卵形过渡;(4)DI、DII和CK中马蹄黄的生存状态指数分别是0.12、0.23和0.63。     

亚高山湿地摇蚊亚化石记录的近两百年来环境演化——以重庆葱坪湿地为例

偏远的亚高山湿地受人为活动直接干扰较小,是追踪气候变化和大气沉降双重影响下湿地生态系统演化的理想研究地.本研究以位于巫山的葱坪湿地为研究对象,基于一根50 cm沉积岩芯的²¹⁰Pb和¹³⁷Cs测年、摇蚊亚化石和元素序列,探讨该湿地近200年来环境演化历史.结果表明,摇蚊种群由1910年之前的Chironomus anthracinus-type、Limnophyes sp.、Cladotanytarsus mancus-type 1变为1910-1925年的C.mancus-type 1、C.anthracinus-type、Procladius sp.和Endochironomus impar-type的优势组合,这些优势种均指示浅水环境.此后,耐营养种E.impar-type、Polypedilum nubeculosum-type和C.anthracinus-type逐渐成为优势种.冗余分析表明,总磷、总碳和钙是解释摇蚊组合变化的显著环境因子.20世纪30年代以前摇蚊种群可能与进入湿地的径流量小、水位较低相关,而20世纪中叶以来摇蚊组合变化指示大气沉降增长背景下湿地营养富集过程.在大气沉降和气候变化的双重影响下,耐营养属种增加和生物多样性降低表明葱坪湿地生态环境正发生退化.     

斑块状海草床对大型底栖动物群落的影响

本研究根据2013年5月在山东省广饶县潮间带海草床及附近海域大型底栖动物的采样数据,对斑块状海草床及邻近海域的大型底栖动物群落多样性、组成和结构进行了比较研究。结果显示,在本研究的海草床及附近海域共获得大型底栖动物41种,其中甲壳动物的物种数量最多(16种),多毛类动物(15种)和软体动物(10种)次之。大型底栖动物优势种有7种,包括多毛类3种,甲壳动物和软体动物各2种。整个研究海域大型底栖动物群落的平均丰度为661.33 ind/m~2,最主要的丰度贡献者为光滑河篮蛤和丝异须虫,它们的丰度均表现出显著的空间差异;动物丰度在海草床覆盖海域明显高于非海草覆盖海域。聚类分析、nMDS排序、SIMPER分析和IMS分析结果显示,在沿海草床的距离梯度上,大型底栖动物并未表现出明显的线性趋势。因此,斑块状海草床的生态服务功能仍然存在,但相当有限。因此,对功能退化的斑块状海草床的保护势在必行,以期恢复其原有的生态服务功能。     

Soil organic carbon storage and soil CO_2 flux in the alpine meadow ecosystem

High-resolution sampling,measurements of organic carbon contents and 14C signatures of selected four soil profiles in the Haibei Station situated on the northeast Tibetan Plateau,and application of 14C tracing technology were conducted in an attempt to investigate the turnover times of soil organic car-bon and the soil-CO2 flux in the alpine meadow ecosystem. The results show that the organic carbon stored in the soils varies from 22.12×104 kg C hm-2 to 30.75×104 kg C hm-2 in the alpine meadow eco-systems,with an average of 26.86×104 kg C hm-2. Turnover times of organic carbon pools increase with depth from 45 a to 73 a in the surface soil horizon to hundreds of years or millennia or even longer at the deep soil horizons in the alpine meadow ecosystems. The soil-CO2 flux ranges from 103.24 g C m-2 a-1 to 254.93 gC m-2 a-1,with an average of 191.23 g C m-2 a-1. The CO2 efflux produced from microbial decomposition of organic matter varies from 73.3 g C m-2 a-1 to 181 g C m-2 a-1. More than 30% of total soil organic carbon resides in the active carbon pool and 72.8%―81.23% of total CO2 emitted from or-ganic matter decomposition results from the topsoil horizon (from 0 cm to 10 cm) for the Kobresia meadow. Responding to global warming,the storage,volume of flow and fate of the soil organic carbon in the alpine meadow ecosystem of the Tibetan Plateau will be changed,which needs further research.     

升温处理对植物碳同位素测试结果的影响

通过研究内蒙古锡林郭勒典型草原生态系统和青海海北高寒草甸生态系统的12种植物在不同升温条件下的碳同位素测试结果,讨论升温处理及其造成的轻微炭化对植物碳同位素组成的影响并分析其作用机理。升温处理对多数植物样品的碳同位素组成没有强烈影响,但也可能导致部分植物的碳同位素组成变重(尤其是当样品发生轻微炭化时),其分馏程度会因物种的不同而不同。     

祁连山海北高寒草甸地区微气候特征的观测研究

对祁连山海北高寒草甸地区近夏至日微气象观测分析表明：（１）１４：００（北京时,下同）太阳总辐射瞬时值最高可达１０６１Ｗ．ｍ＾－２,净辐射、反射辐射、光合有效辐射和紫外辐射分别为６７０、２１８、３８０和１６８Ｗ．ｍ＾－２,分别约为在太阳总辐射的５８％、２０％、３６％和１４％,６月下旬日平均反射率约为０．２２;（２）土壤热通量、感热通量和潜热通量瞬时值最大分别为９１、２７４和３６２Ｗ．ｍ＾－２,相应占     

Effects of grazing exclusion on plant productivity and soil carbon,nitrogen storage in alpine meadows in northern Tibet,China

Grazing exclusion is widely adopted in restoring degraded alpine grasslands on the Qinghai-Tibetan Plateau. However, its effectiveness remains poorly understood. In this study, we investigated the effects of grazing exclusion on plant productivity, species diversity and soil organic carbon （SOC） and soil total nitrogen （STN） storage along a transect spanning from east to west of alpine meadows in northern Tibet, China. After six years of grazing exclusion, plant cover, aboveground biomass （AGB）, belowground biomass （BGB）, SOC and STN were increased, but species diversity indices declined. The enhancement of AGB and SOC caused by grazing exclusion was correlated positively with mean annual precipitation （MAP）. Grazing exclusion led to remarkable biomass increase of sedge species, especially Kobresia pygmaea, whereas decrease of biomass in forbs and no obvious change in grass, leguminous and noxious species. Root biomass was concentrated in the near surface layer （10 cm） after grazing exclusion. The effects of grazing exclusion on SOC storage were confined to shallow soil layer in sites with lower MAP. It is indicated that grazing exclusion is an effective measure to increase forage production and enhance soil carbon sequestration in the studied region. The effect is more efficient in sites with higher precipitation. However, the results revealed a tradeoff between vegetation restoration and ecological biodiversity. Therefore, carbon pools recover more quickly than plant biodiversity in the alpine meadows. We suggest that grazing exclusion should be combined with other measures to reconcile grassland restoration and biodiversitv conservation.     

青藏高原典型高寒草甸植被生长发育对气候和冻土环境变化的响应

利用青藏高原河南县典型高寒草甸生态系统群落结构、地上生物量、发育期及其气候、冻土环境观测资料,系统研究了高寒草甸植被生长发育特征及其对气候变化和冻土退化的响应机理.研究表明：20世纪80年代后期以来,随年代进程高寒草甸植被出现了牧草返青初期无明显变化,而黄枯初期显著延迟,致使生长期延长,覆盖度总体下降,但自2004后开...