贵州省赤水县桫椤调查初报

国家一级重点保护植物桫椤,目前世界上少数国家尚存,国内除华南、西南地区及台湾等少数省份外亦不多见。其中贵州省赤水县桫椤不仅面积广,且数量多,生长旺。据不完全统计,全县35个乡中,有20个乡有分布,面积     

Influence of overwinteringDaphnia on spring zooplankton communities: An experimental study

To evaluate the influence of overwintering individuals of zooplankton on spring zooplankton communities, the dynamics of zooplankton communities with or without overwintering individuals were observed in experimental ponds from fall to spring. An insecticide, carbaryl, was used to regulate the overwintering individuals. In ponds which received insecticide applications in November or January, all cladoceran and rotiferan species were eliminated by the treatments and did not reappear until late March or early April, even when the chemical disappeared rapidly. The low water temperature may delayed the establishment of the populations from resting eggs. In these ponds, populations of various cladoceran and rotiferan species, which seemed to be originated from resting eggs, were built up in the spring. In control ponds,Daphnia ambigua orD. longispina overwintered as juveniles and adults and established a large spring population earlier than other cladocerans and rotifers overwintering as resting eggs. The latter zooplankters did not increase in the spring probably because their growth was suppressed by the precedingDaphnia species through competition. In nature, even if the number of overwintering individuals is small, they may have a potential to build up a large population earlier than the individuals hatching from resting eggs. As a result, the species which have overwintered as individuals seem to predominate in the spring and have a large influence on the spring zooplankton community.     

Influence of wetland hydroperiod on diversity and abundance of metamorphosing juvenile amphibians

Numbers of successfully metamorphosing juvenile amphibians were tabulated at three wetlands in South Carolina, U.S.A. using terrestrial drift fences with pitfall traps. A relatively undisturbed Carolina bay was studied for eight years, a partially drained Carolina bay for four years, and a man-made borrow pit for three years. Annual production of juveniles at the undisturbed Carolina bay ranged from zero to 75,644 individuals of 15 species. Fewer individuals of fewer species typically metamorphosed at the borrow pit than at the undisturbed bay, with the least numbers at the partially drained Carolina bay. Both total number and species diversity of metamorphosing juveniles at each site each year showed a strong positive correlation with hydroperiod, i.e., the number of days a site contained standing water that year. Data for one common anuran species and the most common salamander species were analyzed separately by multiple regression, in addition to the community analyses. For the mole salamander, Ambystoma talpoideum, hydroperiod was a significant predictor of the number of metamorphosing juveniles, but the number of breeding females was not. For the ornate chorus frog, Pseudacris ornata, the number of breeding females was a significant predictor of the number of metamorphosing juveniles, but hydroperiod was not. Variation in the dates of wetland filling and drying interacts with other factors to determine amphibian community structure and diversity. Either increasing or decreasing the number of days a wetland holds water could increase or decrease the number and species diversity of amphibians in and around a wetland.     

多样性指数公式在鸟类群落中应用的探讨

一、前言多样性是反映生物群落功能的组织特征,它与生境密切相关,可以作为生态学上的一个灵敏度指标;它是群落中关于丰富度和均匀度的一个函数,用其指数可以定量地分析群落的     

西双版纳热带季节雨林植物种类多样性的一种研究方法

一、方法1.样地的选择样地分别选取热带干性季节雨林的典型代表——以箭毒木(Antiaris toxicaria)、龙果(Pouteria grandifolia)为标志的群落,以千果榄仁(Terminalia myriocarpa)、番龙眼     

福建武夷山甜槠群落能量的研究

在生物量、生产力研究基础上,对武夷山甜槠（Ｃａｓｔａｎｏｐｓｉｓ ｅｙｒｅｉ（Ｃｈａｍ ｐ．ｅｘ Ｂｅｎｔｈ．） Ｔｕｔｃｈ．）群落各组分的热值、群落能量现存量、能量年净固定量以及太阳能转化效率进行了研究。结果表明：（１）甜槠群落各组分样品的干重热值具有一定的差异,树皮热值最高,细根热值最低。（２）甜槠群落的能量现存量达７８０５８４．１ ｋＪ·ｍ － ２,其中地上部分为６７８９１３．８ ｋＪ·ｍ － ２,占总量的８６．９８％ ;地下部分为１０１６７０．３ ｋＪ·ｍ － ２,占１３．０２％ 。（３）甜槠群落的能量年净固定量（１９９２年）为２６８５６．２ ｋＪ·ｍ － ２·ａ－ １,林地太阳光合有效辐射能的转化效率为１．２９６％ 。     

Adaptation of soil bacterial communities to prevailing pH in different soils

Abstract: The bacterial community response to pH was studied for 16 soils with pH(H₂O) ranging between 4 and 8 by measuring thymidine incorporation into bacteria extracted from the soil into a solution using homogenization-centrifugation. The pH of the bacterial solution was altered to six different values with dilute sulfuric acid or different buffers before measuring incorporation. The resulting pH response curve for thymidine incorporation was used to compare bacterial communities from the different soils. There was a correlation between optimum pH for thymidine incorporation and the soil pH(H₂O). Even bacterial communities from acid soils had optima corresponding to the soil pH, indicating that they were adapted to these conditions. Thymidine incorporation was also compared with leucine incorporation for some soils. The leucine to thymidine incorporation ratio was constant over the tested pH interval when incorporation values were adjusted for isotope dilution. A good correlation was found between the scores along the first component (explaining 80% of the variation) and soil pH ( r ² = 0.85), if principal component analysis of the pH response curves for thymidine incorporation was used. The pH response curves differed most for the extreme pH values used, and a linear relationship was found between the logarithm of the ratio of thymidine incorporation at pH 4.3 to incorporation at pH 8.2 and the soil pH ( r ² = 0.86). Thus, a simplified technique using only two pH values, when measuring the thymidine incorporation, could be used to compare the response to pH of bacterial communities.     

The effects of soil warming on plant recruitment

We demonstrate, using a simple field experiment, that soil warming is sufficient, independent of other cues, to potentially alter the recruitment of Betula pendula seedlings. This study suggests that changing temperature, and correlated changes in edaphic factors, can alter patterns in plant recruitment via differential effects on seed dormancy. Increased soil temperatures (of less than 5 °C) throughout the year led to a significant increase in the number of birch seedlings that emerged from soil samples collected in the spring. No concomitant changes in the emergence of other species was observed. Such temperature induced changes in seedbank dynamics and their subsequent effects on the competitive interactions within a plant community suggest far reaching ecological consequences of current increases in global temperature.     

The vegetation of the Puna Belt at laguna de Pozuelos Biosphere Reserve in northwest Argentina

The presence of species and their cover values together with soil and topographic characteristics were recorded at 40 sites along an altitudinal gradient of the Puna Belt at Pozuelos, in the High Andes in northwest Argentina. Classification and ordination of plant assemblages showed that soil and topography were the best predictors of the variation in species distribution. The different plant assemblages which occur along the topographic gradient follow the geographic variation in rainfall in this Andean region. Perennial bushes and grasses colonize the plains and slopes with fine textured soils which retain their water content. In contrast, deciduous bushes and cactuses grow on steep, rocky, dry slopes. Open woods also occur on east-facing steep, rocky slopes which are sheltered from winds.     

Plant growth and reproduction along CO2 gradients: non-linear responses and implications for community change

The effects of rising atmospheric CO₂ concentrations on natural plant communities will depend upon the cumulative responses of plant growth and reproduction to gradual, incremental changes in climatic conditions. We analysed published studies of plant responses to elevated CO₂ to address whether reproductive and total biomass exhibit similar enhancement to elevated vs. ambient CO₂ concentrations, and to assess the patterns of plant response along gradients of CO₂ concentrations. In six annual plant species, mean enhancement at double ambient vs. ambient CO₂ was 1.13 for total biomass and 1.30 for reproductive biomass. The two measures were significantly correlated, but there was considerable scatter in the relationship, indicating that reproductive responses cannot be consistently predicted from enhancement of total biomass. Along experimental CO₂ gradients utilizing three concentrations, there was a great diversity of response patterns, including positive, negative, non-monotonic and non-significant (flat) responses. The distribution of response patterns differed for plants grown in stands compared to those grown individually. Positive responses were less frequent in competitive environments, and non-monotonic responses were more frequent. These results emphasize that interpolation of plant response based on enhancement ratios measured at elevated vs. ambient CO₂ concentrations is not sufficient to predict community responses to incremental changes in atmospheric conditions. The consequences of differential response patterns were assessed in a simulation of community dynamics for four species of annual plants. The model illustrates that the final community composition at a future point in time depends critically on both the magnitude and the rate of increase of atmospheric CO₂.