若尔盖高原生态环境恶化与沼泽退化及其形成机制

根据１９９６－１９９８年野外考察与研究获得信息,结合前人研究的资料,论证了若尔盖高原沼泽区生态环境恶化,沼泽退化十分严重,其主要表现为：沼泽旱化,沼泽类型改变,沼泽逆向生态演替,沼泽区沙化,野生动物种类,种群数量减少,土壤质量下降,沼泽水质变劣,草场退化和鼠害猖獗,剖析了沼泽区生态环境恶化,沼泽退化与人类活动干扰,自然因素作用的关系,进而阐明了人类活动干扰是沼泽区生态环境恶化,沼泽退化主要原因。     

Plankton origin of particulate dimethylsulfoniopropionate in a Mediterranean oligotrophic coastal and shallow ecosystem

We report here dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) levels as a function of plankton communities and abiotic factors over a 12-month cycle in the Mediterranean oligotrophic coastal and shallow ecosystem of Niel Bay (N.W. Mediterranean Sea, France). Total particulate DMSP (DMSP_p) and DMS concentrations were highly seasonal, peaking during a spring (April) bloom at 8.9 nM and 73.9 nM, respectively. Significant positive correlations were found between total DMSP_p concentration and the abundance or biomass of the dinoflagellate Prorocentrum compressum (Spearman's rank correlation test: r = 0.704; p = 0.011). Similarly, DMS concentrations peaked during the development of blooms of P. compressum and Gymnodinium sp. There seemed to be a positive relationship between the chlorophyll a to pheopigment ratio and DMS concentrations, suggesting that DMS was released during phytoplankton growth. High DMS levels recorded in the shallow Niel Bay may also result from the activity of benthic macroalgae, and/or macrophytes such as Posidonia spp., or the resuspension of sulfur species accumulating in sediments. The fractionation of particulate DMSP into three size classes (>90 μm, 5–90 μm and 0.2–5 μm) revealed that 5–90 μm DMSP-containing particles made the greatest contribution to the total DMSP_p pool (annual mean contribution = 62%), with a maximal contribution in April (96%). This size class consisted mainly of dinoflagellates (annual mean contribution = 68%), with P. compressum and Gymnodinium sp. the predominant species, together accounting for up to 44% of the phytoplankton present. The positive correlation between DMSP concentration in the 5–90 μm size class and the abundance of P. compressum (Spearman's rank correlation test: r = 0.648; p = 0.023) suggests that this phytoplankton species would be the major DMSP producer in Niel Bay. The DMSP collected in the >90 μm fraction was principally associated with zooplankton organisms, dominated by copepods (nauplii and copepodites). DMSP_>90, not due to a specific zooplankton production, resulted from the phytoplankton cells ingested during grazing. The concomitant peaks of DMS concentration and zooplankton abundance suggest that zooplankton may play a role in releasing DMSP and/or DMS through sloppy feeding.     

沼泽甲烷排放及其主要影响因素

综合评述了不同类型沼泽产生、氧化和排放甲烷能力的差异及其主要影响因素。沼泽水位的变化引起沼生植物种群更替，从而形成不同类型的沼泽及其土壤剖面形态特征，进而导致沼泽产生和排放甲烷能力的不同。腐泥沼泽产生和排放甲烷能力最强，泥炭沼泽次之，森林沼泽再次之，苔藓泥炭沼泽最弱。甲烷排放以夏季最多，春秋季次之，冬季最低。在影响沼泽排放甲烷能力中，水位的变化最为强烈，底物、植物种类及数量和温度次之，pH、外源氮和土壤性质也有一定的作用。     

抚仙湖近60年来沉水植物群落变化趋势分析

自1960s以来,抚仙湖沿岸带沉水植物群落发展迅速,而监测频率相对不足.为了解抚仙湖沉水植物群落现状及过去60年内的变化趋势,于2016年7月,对抚仙湖全湖沉水植物进行调查,并结合以往多次调查数据进行趋势分析.本次调查设置了36条样带共41个样点.在实测数据验证后,使用卫星多光谱相机数据基于归一化植被指数(NDVI)计...     

不同形态磷酸盐对铜绿微囊藻和蛋白核小球藻生长的影响

地表糙度是衡量地表径流形成的一个重要指标．以东北区典型泥炭沼泽——金川泥炭沼泽为例,考虑地表坡度影响,用链条法对不同群落中糙度系数指标进行计算,并以泥炭沼泽中物种多样性、踏头个数以及踏头形态差异变率系数为主,初步分析泥炭泥泽地表糙度的变化机制,结果表明：在芦苇-臌囊苔草群落、臌囊苔草群落和油桦-臌囊苔草-泥炭藓群落三个植物群落中,糙度系数指标的变化与群落中物种丰富度和生物多样性变化相一致;糙度系数变化与踏头个数呈负相关关系,与踏头形态差异变率系数呈正相关关系说明物种多样性越小,生态优势度越大,优势种植物越少,踏头个数越多,踏头形态变率系数越小,微地貌形态发育相对较一致,糙度系数越小;反之,则地表糙度系数越大。     

Experimental hydrological forcing to illustrate water flow processes of a subarctic ladder fen peatland

Large peatland complexes dominate the landscape of the James Bay Lowland in subarctic Ontario, Canada. However, there is not a thorough understanding of the hydrological processes occurring in these important systems, particularly how ladder fens connect large domed bogs to the aquatic ecosystems that drain the peatland complex. Ladder fens consist of a pool‐rib topography where flow downgradient is controlled by the peat ribs. Within the ribs, low‐lying preferential flow paths typically enhance the transmission of water, whereas the elevated ridge microforms impede water flow to downgradient aquatic ecosystems. To assess the hydrological connectivity, we study the role of the water table, peat transmissivity, and microtopography of a small ladder fen for 3 summers (2013–2015) in the James Bay Lowland. The system was manipulated with a sustained hydrological forcing (water addition) to the upslope boundary of the fen during 2014 (38 m³/day) and 2015 (30 m³/day). There was an exponential increase in transmissivity towards the peat surface due to extremely high‐hydraulic conductivities within the upper few centimeters of the peat deposit. At the maximum water table, the saturated hydraulic conductivity of the 0.1 m layer of peat below the water table varied depending on peat microtopography (preferential flow paths = 42–598 m/day and ridges = 16–52 m/day), resulting in high‐hydrological connectivity periods. Furthermore, during 2015, there was an abnormally large amount of precipitation (300 mm vs. long‐term average ~ 100 mm) that resulted in complete surface water connectivity of the site. This caused rapid movement of water from the head of system to the outlet (~15 hr) and runoff ratios >1, compared to low‐water table periods (runoff ratio ~ 0.05). This study highlights the profound importance of the transmissivity–water table feedback mechanism in ladder fens, on controlling the water retention and drainage of large peatland complexes.     

Geochemical and stratigraphic evidence of environmental change at Lynch's Crater, Queensland, Australia

This is one of the first applications of geochemical proxies to define changes in vegetation, hydrology and atmospheric dust influence on a peat deposit in the southern hemisphere. A 6.6 m deep peat record from Lynch's Crater in NE-Queensland, Australia, provides a sensitive  5000 to 30,000 cal years BP archive of environmental change. The deposit consists of 1.5 m of ombrotrophic peat underlain by a minerotrophic peat. Within the minerotrophic section, sponge spicules and diatom fragments offer evidence of prolonged flooding of the peat environment resulting in several layers containing (up to 50%) high inorganic material. The Ca and Mg data display episodes of enhanced dust influx and nutrient recycling and support previous palynological studies that show a Pleistocene to Holocene switch from sclerophyll woodlands to rainforest vegetation.