南沙群岛海域理化参数垂向分布特征及跃层生态系的提法

自1985～1999年中国科学院南沙综合科学考察队在南沙群岛进行了12个航次的综合科学考察.根据调查的结果,通过分析南沙群岛海域理化参数垂向分布特征,得出次表层海水理化参数具有极值现象、跃变现象和波动现象的特点,讨论了这些独特特征反映的独特生境,提出了南沙群岛海域垂直方向上存在跃层生态系的观点.     

Studies on the role of marine bacteria in the upwelling ecosystem——Ⅰ.Bacterial biomass in the upwelling regions

-Six cruises were carried out off the south bank of Fujian - Taiwan during the period of December 21, 1987 to November 15, 1988 to estimate the contribution of bacterial biomass carbon (BBC) to the totai particulate organic pools using epifluorescent microscopic technique. The results show that the standing crop of bacteria fluctuated from 0. 95 to 66. 60 mg /m3 (dry weight). Upwelling phenomena appeared in the region around Nanpeng Island in summer while in the region of Waixie in all seasons. The average value of BBC was 27. 60(±6. 08)mg/m3and 21. 32 (±2. 34) mg/m3 respectively. The seasonal and spatial distribution is discussed in relation to environmental factors as well as upwelling phenomena. The role of bacteria in the flow of material and energy in the upwelling ecosystem is emphasized.     

北京市生态涵养区生态系统服务供给与流动的能值分析

近年来北京市建成区扩张迅速,对城市周边地区的生态系统服务需求上升。本文以北京市生态涵养区为例,利用能值评估方法评估该区域生态系统服务,分析各生态系统及其与城市系统之间的服务流动和依赖关系。研究结果表明：从生态系统类型上看,2012年森林生态系统服务对涵养区生态系统服务贡献最大,占到生态系统服务总能值的79.7%,其次为农田和水域生态系统,分别占总能值的19.7%和0.6%;从生态系统服务类型上看,森林生态系统的有机物生产和水源涵养是其主要的生态系统服务,分别占总能值产出的40.4%和35.8%。粮食供给是农田系统的主要能值输出,占农田生态系统能值的70%。水域提供的生态系统服务中,能值比例较高的依次为水源供给、洪水调蓄和水产品供给,分别占水域生态系统能值的35.1%、28.6%和28.2%;从能值转移矩阵分析可以看出,对城市来说,森林生物量、森林土壤水、水域地下水和农田生物量是重要的生态系统服务供给组分;系统能值动态分析结果表明,2004年到2012年森林和水域生态系统重要程度增加,农田生态系统重要程度有所减少,城市系统的角色由主动变为被动。因此,在未来的发展规划中,对森林和水域生态系统的保育应给予足够关注。     

天然林资源保护一期工程生态成效评估——以甘肃小陇山地区为例

天然林资源保护工程是在中国广泛开展的一项重要生态建设工程。本文在构建生态多元评估指标体系的基础上,评估工程实施的生态成效,对于其进一步决策与管理具有重要的科学意义。通过遥感、生态系统质量等多源数据融合,采用生态系统宏观格局、生态系统质量、生态系统服务等方面指标的现状和时空变化特征,评估小陇山地区天然林保护一期工程(2000-2010年)实施成效。结果表明：①工程实施后,小陇山地区落叶阔叶林、落叶阔叶灌木林、草地等生态系统类型的面积大幅度增加,生态系统宏观状况转好,其中黄河流域生态系统宏观状况转好趋势明显好于长江流域。②研究区叶面积指数(LAI)和最大植被覆盖度(FC)在2000-2010年期间的多年变化斜率分别为0.022和0.510,生态系统质量上升趋势明显。其中黄河流域改善程度高于长江流域。③2010年研究区固碳量为700.20 t/hm²,相比工程初期的2000年增加了4.69%;工程实施之后的10年间,研究区水源涵养量呈增长趋势,土壤保持量亦呈增长趋势;就流域而言,黄河流域的生态系统服务的提升程度均更为明显。     

The weak effects of fencing on ecosystem respiration, CH4, and N2O fluxes in a Tibetan alpine meadow during the growing season

Fencing is the most common land-management practice to protect grassland degradation from livestock overgrazing on the Tibetan Plateau. However, it is unclear whether fencing reduces CO_2, CH_4, and N_2O emission. Here, we selected four vegetation types of alpine meadow(graminoid, shrub, forb, and sparse vegetation) to determine fencing effects on ecosystem respiration(Re), CH_4, and N_2O fluxes during the growing season. Despite increased average monthly ecosystem respiration(Re) for fenced graminoid vegetation at the end of the growing season, there was no significant difference between grazing and fencing across all vegetation types. Fencing significantly reduced average CH_4 uptake by about 50% in 2008 only for forb vegetation and increased average N_2O release for graminoid vegetation by 38% and 48% in 2008 and 2009,respectively. Temperature, moisture, total organic carbon, C/N, nitrate, ammonia, and/or bulk density of soil, as well as above-and belowground biomass, explained 19%~71% and 6%~33% of variation in daily and average Re and CH_4 fluxes across all vegetation types, while soil-bulk density explained 27% of variation in average N_2O fluxes. Stepwise regression showed that soil temperature and soil moisture controlled average Re, while soil moisture and bulk density controlled average CH_4 fluxes. These results indicate that abiotic factors control Re, CH_4, and N_2O fluxes; and grazing exclusion has little effect on reducing their emission—implying that climatic change rather than grazing may have a more important influence on the budgets of Re and CH_4 for the Tibetan alpine meadow during the growing season.