青藏高原高寒沼泽化草甸群落生物量及地下CNP对积雪增加的响应

以青藏高原多年冻土区高寒沼泽化草甸为研究对象,采用雪栅栏诱导方式模拟积雪厚度增加,结合植物地上、地下根系以及土壤养分变化,分析了高寒沼泽化草甸对积雪厚度增加的响应。结果表明：积雪厚度增加后,0~20 cm浅层土壤温度和水分含量增加;植物群落高度和土壤表层0~10 cm根系生物量显著增加,植物群落组成和地上生物量没有变化;地下0~20 cm土壤碳（C）、氮（N）、磷（P）总储量降低,根系中C、N、P储量增加;土壤表层0~10 cm总N∶P比显著增加,但是有效磷含量在0~10 cm和10~20 cm土层均显著增加。可见,积雪厚度增加并不影响沼泽化草甸植物群落的组成和地上生物量,仅增加植被高度;增加土壤表层总N∶P比意味着积雪厚度增加可能会减轻沼泽化草甸土壤中氮限制,从而减缓沼泽化草甸的氮匮乏状况。结论可为高寒生态系统响应积雪变化研究提供样地尺度的观测数据,并为冰冻圈生态系统应对未来气候变化的模型估算提供数据支撑。     

青藏工程走廊活动层厚度预测模型与分布特征研究

为探究青藏工程走廊沿线多年冻土区活动层厚度分布情况,结合青藏公路、青藏铁路沿线300个钻孔点的活动层厚度监测数据,基于年平均地表温度、平均植被指数、等效纬度、纬度、高程和含冰量等参数建立了活动层厚度的经验公式、随机森林和径向基函数（radial basis function, RBF）神经网络预测模型。各预测模型结果表明,活动层厚度与各预测因子间具有极强的非线性关系;RBF神经网络预测模型具有最高的预测精确度,拟合优度R²达到0.84。运用RBF神经网络预测模型和高精度遥感数据绘制活动层厚度分布图,分布图显示研究区内活动层厚度主要为2~4 m,总面积为5 468.3 km²,面积占比为47.27%,主要分布于楚玛尔平原至北麓河盆地和唐古拉山区南部至头二九山区;活动层厚度大于4 m次之,总面积为3 382.3 km²,面积占比为29.24%,整体分布偏向南部地区,主要分布于布曲河谷地至头二九山区。并对研究区活动层厚度与含冰量、地温关系进行了研究,结果表明活动层厚度随含冰量增加而减小、随地温升高而增加。     

北黄海微表层细菌丰度与可培养细菌群落结构分析

为分析海洋微表层这一特殊生境中的细菌类群,于2010—2011年4个航次对北黄海微表层和次表层海水中的总菌丰度、可培养细菌丰度和群落结构进行了分析。采用流式细胞仪测定总菌丰度,平板计数法测定可培养细菌丰度,PCR-16SrDNA分析可培养细菌的群落结构。结果表明,调查海域微表层海水总菌均值为1.76×106 cell/mL,次表层海水总菌均值为1.07×106 cell/mL。可培养细菌丰度范围是1.00×102~1.70×106 CFU/mL,微表层和次表层可培养细菌所占总菌数量的百分比分别为13.05%和0.45%。微表层对总菌的富集因子(EF)均值为2.02,可培养细菌的EF均值为74.16。PCR-16SrDNA序列分析结果表明,该海域可培养细菌分属变形菌门(Proteobacteria)(94.34%)、厚壁菌门(Firmicutes)(1.89%)、拟杆菌门(Bacteroidetes)(1.89%)和放线菌门(Actinobacteria)(1.89%)4个类群。本研究初步发现,微表层对细菌具有较强的聚集作用,尤其对可培养细菌聚集作用更为明显。微表层中可培养细菌的群落结构与次表层有所不同,其种类丰富,来源和功能多样。由此可见,微表层独特的生境成就了其独特的微生物类群,其生态功能有待于进一步研究。     

湛江湾浮游动物群落结构特征及其周年变化

2010年10月至2011年9月对湛江湾浮游动物进行了周年调查,研究了其群落结构的周年变化及影响因素。结果共检出浮游动物87种和29类浮游幼虫,隶属于16大类群,群落结构主要由桡足类(30种)、浮游幼虫(29类)和原生动物(23种)所组成,分别占总种类数的25.86%、25.00%和19.83%。浮游动物种类数以4月最多,2月和3月最少,4~9月的总种类数均高于其他月份。湛江湾浮游幼虫以底栖动物幼虫为主,在4月种类最多,5月丰度最高,4~7月为湛江湾海洋动物的繁盛时期。浮游动物优势种共有22种(类),其中浮游幼虫9类,原生动物7种,桡足类3种,水母类、毛颚类、被囊类各1种,以12月、4月和5月优势种最多(8种),2月最少(2种),无全年优势种,群落结构明显趋于小型化。各相邻月份的共有种类数在18~33种,物种更替率R的范围为37.25%~73.61%,多样性指数H'、均匀度J及丰富度d的年均值较低,分别为2.64、0.54和3.32。在调查期间,湛江湾浮游动物丰度出现了3个高峰,且分别由不同的浮游动物类群组成,其中12月份的高峰主要由原生动物组成,2月份的高峰主要由桡足类组成,而5月份的高峰则主要由浮游幼虫组成,3大类群共同主导湛江湾浮游动物群落结构;浮游动物生物量仅在2月和9月出现高峰,呈现月份双峰型变化。湛江湾浮游动物的周年变化主要受水温、食物及摄食压力的影响。     

东海陆架表层沉积物细菌群落结构及地理分布研究

本研究通过构建16S r DNA克隆文库,对东海陆架五个站点的沉积物样品进行群落结构及地理分布研究。结果表明:东海陆架沉积物细菌分属于13个类群,包括变形菌门(Proteobacteria)、厚壁菌门(Firmicutes)、酸杆菌门(Acidobacteria)、绿弯菌门(Chloroflexi)、放线菌门(Actinobacteria)、硝化螺旋菌门(Nitrospira)、WS3、拟杆菌门(Bacteroidetes)、螺旋体门(Spirochaetes)、OP8、浮霉菌门(Planctomycetacia)、疣微菌门(Verrucomicrobiae)和芽单胞菌门(Gemmatimonadetes),其中变形菌门(γ-变形菌纲、δ-变形菌纲)和绿弯菌门为优势菌群,Latescibacteria(WS3)、疣微菌门和芽单胞菌门分别是站点DH6、DH21和DH9的特有类群。五个站点细菌多样性从高到低排序依次为DH9DH21DH17DH6DH16,其群落结构和丰度与各站点不同沉积环境类型有关。     

中街山列岛岩礁海域鱼类群落多样性研究

加快包括岛礁海域鱼类资源在内的渔业资源调查研究,可以进一步完善该区域鱼类群落生态学内容,探究岩礁海域生境生态学功能,为该海域鱼类资源的养护修复、可持续利用和有效管理提供科学依据。本文基于2013年11月—2014年10月的中街山列岛岩礁海域鱼类资源调查数据,对研究区域鱼类组成及群落多样性分析,结果如下:全年渔获鱼类49种隶属9目28科42属,暖水种和暖温种分别为25和24种,底层、近底层和中上层鱼类各为12、26和11种,定居种、季节性洄游种和偶见种各为28、19和2种;褐菖鲉为全年的绝对优势种,黄姑鱼年IRI值最大,为37.23;迁移指数分析显示群落7月份稳定性最高;ABC曲线分析显示6月受到的干扰最小,2月受到的干扰最大;流刺网年渔获率和CPUE分别为44.03尾/km、13.43 kg/km,延绳钓作业分别为4.91尾/100钓、1.67kg/100钓;群落多样性指数分析结果显示,Margalef种类丰富度指数2月最低,为2.35,7月最大,为4.93;Shannon-Wiener多样性指数7—8月均值最大,为2.80左右;均匀度指数最大和最小值分别是0.97、0.74;三种多样性指数均呈现随气温升高而增大的趋势,但均匀度指数变化没有前2个指数明显,12月和5月3种指数均有波动现象发生。     

Evidence of a phase shift to Epizoanthus gabrieli Carlgreen, 1951 (Order Zoanthidea) and loss of coral cover on reefs in the Southwest Atlantic

There is at present a ‘coral reef crisis’; one of the more drastic consequences of this is a phase shift, in which reef‐building corals are replaced by non‐reef building benthos such as macroalgae and soft corals. Previous studies have principally focused on the shift to macroalgae. Our goal was to investigate whether the dominance of the zoanthid Epizoanthus gabrieli on some reefs of Todos os Santos Bay, Brazil, represented a non‐algal phase shift. In 2003, we identified a high cover of this species on two reefs (52% and 70%), but only in 2007 was it possible to confirm a reduction in coral cover. This dominance has persisted for over 9 years, characterizing a true phase shift. This loss of coral cover may be a result of anthropogenic disturbances within the bay; however, given the large number of human impacts, further studies are needed to identify specific causes of this shift. Although there are some reports of phase shift involving species pertaining to the Class Anthozoa, this is the first report of this phenomenon involving the order Zoanthidea.     

Saldanha Bay,South Africa II: estimating bay productivity

Saldanha Bay is a narrow-mouth bay on the west coast of South Africa linked to the southern Benguela upwelling system. Bay productivity was investigated by use of the conventional light-and-dark bottle oxygen method, and, for comparison, through assimilation of the stable isotope tracer ¹³C. Gross community production GCP and net community production NCP, as determined from the oxygen method, were respectively 2.6 and 2.4 times higher than estimates determined from the stable isotope method. Chlorophyll a (Chl a) concentrations increased with the onset of spring and well-defined subsurface maxima developed in association with increasingly stratified conditions (mean water column Chl a concentrations ranged from 5.4 to 31.5?mg m^?3 [mean 15.5?mg m^?3; SD 7.6]). A sharp decline in photosynthetic rates P* (GCP normalised to Chl a concentration) with depth was attributed to light limitation, as demonstrated by the high vertical attenuation coefficients for downward irradiance K_d, which varied from 0.29 to 0.70?m^?1 (mean 0.48?m^?1; SD 0.12). Productivity maxima were consequently near-surface despite the presence of deeper subsurface biomass maxima. The community compensation depth Z_cc, where gross community production balances respiratory carbon loss for the entire community, ranged from 2.9 to 9.2?m (mean 5.8?m; SD 2.2), and was typically shallower than the 1% light depth for PAR (photosynthetically available radiation), Z1%PAR, which is traditionally assumed to be the depth of the euphotic zone and which ranged from 6.6 to 15.9?m (mean 9?m; SD 2.6). Autotrophic communities, where organic matter is produced in excess of respiratory demand, were confined on average to the upper 5.8?m of the water column, and often excluded the bulk of the phytoplankton community, where light limitation is considered to lead to heterotrophic community metabolism. Estimates of integrated water column productivity ranged from 0.84 to 8.46?g C m–2 d^?1 (mean 3.35?g C m^?2 d^?1; SD 1.9).     

Spatial heterogeneity in a deep artificial lake plankton community revealed by PCR-DGGE fingerprinting

To explore the spatial heterogeneity of plankton communities in a deep artificial lake(Songhua Lake,China),samples were collected at seven sites. Samples were investigated by denaturing gradient gel electrophoresis(DGGE) analysis of the PCR-amplified 16 S and 18 S r RNA genes and specif ic bands were sequenced. Cluster analysis of the DGGE profiles revealed that all of the samples grouped into two distinct clusters,in accordance with sampling site; while in each cluster,the divergence of sub-clusters correlated with sampling depth. Sequence analysis of selected dominant DGGE bands revealed that most sequenced phylotypes(84%) exhibited ≥97% similarity to the closest sequences in Gen Bank,and were affiliated with ten common freshwater plankton phyla(Proteobacteria,Actinobacteria,Bacteroidetes,Cyanobacteria,Bacillariophyta,Pyrrophyta,Cryptophyta,Ciliophora,Stramenopiles,and R otifera). Several of these groups are also found worldwide,indicating the cosmopolitan distribution of the phylotypes. The relationships between DGGE patterns and environmental factors were analyzed by redundancy analysis(RDA). The results suggested that,total nitrogen,nitrate,nitrite,ammonia,and CODM n concentrations,and water temperature were strongly correlated with the variation in plankton composition.     

Monitoring grass nutrients and biomass as indicators of rangeland quality and quantity using random forest modelling and WorldView-2 data

Land use and climate change could have huge impacts on food security and the health of various ecosystems. Leaf nitrogen (N) and above-ground biomass are some of the key factors limiting agricultural production and ecosystem functioning. Leaf N and biomass can be used as indicators of rangeland quality and quantity. Conventional methods for assessing these vegetation parameters at landscape scale level are time consuming and tedious. Remote sensing provides a bird-eye view of the landscape, which creates an opportunity to assess these vegetation parameters over wider rangeland areas. Estimation of leaf N has been successful during peak productivity or high biomass and limited studies estimated leaf N in dry season. The estimation of above-ground biomass has been hindered by the signal saturation problems using conventional vegetation indices. The objective of this study is to monitor leaf N and above-ground biomass as an indicator of rangeland quality and quantity using WorldView-2 satellite images and random forest technique in the north-eastern part of South Africa. Series of field work to collect samples for leaf N and biomass were undertaken in March 2013, April or May 2012 (end of wet season) and July 2012 (dry season). Several conventional and red edge based vegetation indices were computed. Overall results indicate that random forest and vegetation indices explained over 89% of leaf N concentrations for grass and trees, and less than 89% for all the years of assessment. The red edge based vegetation indices were among the important variables for predicting leaf N. For the biomass, random forest model explained over 84% of biomass variation in all years, and visible bands including red edge based vegetation indices were found to be important. The study demonstrated that leaf N could be monitored using high spatial resolution with the red edge band capability, and is important for rangeland assessment and monitoring.