Distribution of ground-dwelling beetles （Coleoptera） across a forest-clearcut ecotone in Wolong Natural Reserve, southwestern China

Abstract The influence of edge effect on ground-dwelling beetles (Coleoptera) across a forest-clearcut ecotone was studied in Wolong Natural Reserve, southwestern China. During the field research, a total of 30 739 beetles were collected with pitfall traps along transects, which extending 100 m from the edge into the forest interior and 100 m into the clearcut. Of the collection, Carabidae comprised 92%, Staphylinidae 3%, Curculionidae 2%, and Tenebrionidae 2%, and these four families can be considered as abundant groups. Family richness, Shannon diversity and equitability display a significant decrease from forest interior, edge to clearcut. Based on the family composition and abundance, ground-dwelling beetles of the forest interior can be separated from those in the clearcut by Principal coordinate analysis ordination, and beetle assemblages in the forest edge were more similar to forest assemblages than to those found in the clearcut by cluster analysis. Seasonal dynamics of family richness showed a monotone peak in the middle season, with a highest value in the forest interior and a lowest value in the clearcut. Family abundance showed two peaks in the middle season, always with more individuals in the clearcut than in the forest interior or in the edge. Multiple linear regression analyses showed that the cover of shrub and litter were the two most important factors in determining family richness, Shannon diversity, equitability and abundance. Our results show that the forest edge and clearcut have obviously different composition and diversity of ground-dwelling beetles from forest interior at the family level. However, more edges have been formed due to increasing forest fragmentation (clearcutting or logging), so it is necessary to preserve large and intact forest to protect the diversity of ground-dwelling beetles in Wolong Natural Reserve.     

Species composition and correlation of understory woody plants in Chinese fir plantation in the lower subtropical area

There are 71 species in the shrub layer of the Cunninghamia lanceolata plantation after natural succession. The species richness and diversity have increased with slight anthropogenic disturbance. The status and function of understory woody species were judged by the analysis of the important value (IV). x ² statistics and r test were used for testing the significance of interspecific association and correlation among 25 main understory woody plants selected from the woody population. The results clearly showed their interspecific relationships and their differences in resource utilization. Species-pairs of positive association were in the majority. Most species were accommodated in the shady habitat. There was a positive correlation between the IV of the species and the interspecific association. The higher the IV of the species, the closer and more significant was the interspecific association. Based on analytical results of interspecific association and correlation, 25 woody plants in the shrub layer could be divided into four ecological species groups: I. Ficus hispida + Antidesma bunius + Mallotus barbatus + Ficus cunia + Saurauia tristyla + Mallotus philippinensis + Maesa japonica + Ficus hirta + Alchornea rugosa + Ficus fulva + Mallotus apelta; II. Cudrania tricuspidata + Schefflera octophylla; III. Cunninghamia lanceolata + Clerodendron cytophyllum + Millettia semicastrata + Randia spinosa + Litsea cubeba + Litsea pungens; IV. Ardisia japonica + Psychotria rubra + Vitex quinata + Cephalanthus occidentalis + Pithecellobium lucidum + Mycetia sinensis. If species group III or II is the advantaged species in the shrub layer, the community would change from a coniferous forest to a sparse evergreen broad-leaved forest. For group IV, the community would be relatively stable. For group I, the coniferous forest would be mixed with coniferous-broad leaved forest. The classification of ecological species groups would provide a theoretical basis on judging its ecological function, adjusting the stand structure of the plantation and directing the suitable natural vegetation type through the close-natural restoration process. __________ Translated from Acta Ecologica Sinica, 2005, 25(9): 2173–2179 [译自: 生态学报, 2005, 25(9): 2173–2179]     

影响武夷山景区松墨天牛种群动态变化的因素分析

为了监测武夷山景区松墨天牛Monochamus alternatus Hope的发生,防范松材松材线虫Bursaphelonchus xylophilus病的入侵,于2005-2007年每年4-9月,在武夷山景区10个地点进行了调查,研究了气象因素和环境因素对松墨天牛数量变化的综合影响规律及其程度,对调查结果进行了矢量递进因子分析。结果表明：环境因子和气象因子是松墨天牛羽化孔数和诱集成虫数变化的主要因素,影响松墨天牛成虫诱集数的环境因子按重要性排列依次为：郁闭度、地被物覆盖率、海拔、林龄、坡位、坡向和树高;影响羽化孔数的环境因子按重要性排列依次为：郁闭度、地被物覆盖率、树高、林龄、海拔、坡位和坡向。影响松墨天牛诱集成虫数和羽化孔数的气象因子按重要性排列依次为：月平均温度、最高与最低温差、总降雨量（mm）、气压（hpa）和平均湿度（%）。单从环境因子和气象因子的统计数据分析,环境因子的重要性次序是：坡位、郁闭度、地被物覆盖率、海拔（m）、 林龄（a）、树高（m）、坡向;气象因子的重要性次序是：气压（hpa）、 平均温度 （℃）、最高与最低温差（℃）、 总降雨量（mm）、平均湿度（%）。按月分析和按年度分析时其相对重要性基本上是一致的。结论认为,环境因子和气象因子对松墨天牛的数量变化有重要影响。     

Floral adaptation and diversification under pollen limitation

Pollen limitation (PL) of seed production creates unique conditions for reproductive adaptation by angiosperms, in part because, unlike under ovule or resource limitation, floral interactions with pollen vectors can contribute to variation in female success. Although the ecological and conservation consequences of PL have received considerable attention in recent times, its evolutionary implications are poorly appreciated. To identify general influences of PL on reproductive adaptation compared with those under other seed-production limits and their implications for evolution in altered environments, we derive a model that incorporates pollination and post-pollination aspects of PL. Because PL always favours increased ovule fertilization, even when population dynamics are not seed limited, it should pervasively influence selection on reproductive traits. Significantly, under PL the intensity of inbreeding does not determine whether outcrossing or autonomous selfing can evolve, although it can affect which response is most likely. Because the causes of PL are multifaceted in both natural and anthropogenically altered environments, the possible outcrossing solutions are diverse and context dependent, which may contribute to the extensive variety of angiosperm reproductive characteristics. Finally, the increased adaptive options available under PL may be responsible for positive global associations between it and angiosperm diversity.     

Genetic and historic evidence for climate-driven population fragmentation in a top cetacean predator: the harbour porpoises in European water

Recent climate change has triggered profound reorganization in northeast Atlantic ecosystems, with substantial impact on the distribution of marine assemblages from plankton to fishes. However, assessing the repercussions on apex marine predators remains a challenging issue, especially for pelagic species. In this study, we use Bayesian coalescent modelling of microsatellite variation to track the population demographic history of one of the smallest temperate cetaceans, the harbour porpoise (Phocoena phocoena) in European waters. Combining genetic inferences with palaeo-oceanographic and historical records provides strong evidence that populations of harbour porpoises have responded markedly to the recent climate-driven reorganization in the eastern North Atlantic food web. This response includes the isolation of porpoises in Iberian waters from those further north only approximately 300 years ago with a predominant northward migration, contemporaneous with the warming trend underway since the ‘Little Ice Age’ period and with the ongoing retreat of cold-water fishes from the Bay of Biscay. The extinction or exodus of harbour porpoises from the Mediterranean Sea (leaving an isolated relict population in the Black Sea) has lacked a coherent explanation. The present results suggest that the fragmentation of harbour distribution range in the Mediterranean Sea was triggered during the warm ‘Mid-Holocene Optimum’ period (approx. 5000 years ago), by the end of the post-glacial nutrient-rich ‘Sapropel’ conditions that prevailed before that time.     

The ‘New Wave’ in plant demographic inference: more loci and more individuals

Plant population genetic surveys are starting to take full advantage of technological advances in genotyping methods and of methodological advances in demographic inference. In this issue of Molecular Ecology, Keller et al. (2010) illustrate this trend with a particularly convincing study of rangewide genetic variation in a North American poplar, using both SNP and sequence data. They first investigate population genetic structure by estimating the most likely number of genetic clusters using a more formal approach than most other studies to date. They proceed by estimating gene flow among the inferred populations and by testing predictions on the distribution of low frequency alleles derived from recent work on range expansions.     

Can small wildlife conservancies maintain genetically stable populations of large mammals? Evidence for increased genetic drift in geographically restricted populations of Cape buffalo in East Africa

The Cape buffalo (Syncerus caffer caffer) is one of the dominant and most widespread herbivores in sub‐Saharan Africa. High levels of genetic diversity and exceptionally low levels of population differentiation have been found in the Cape buffalo compared to other African savannah ungulates. Patterns of genetic variation reveal large effective population sizes and indicate that Cape buffalos have historically been interbreeding across considerable distances. Throughout much of its range, the Cape buffalo is now largely confined to protected areas due to habitat fragmentation and increasing human population densities, possibly resulting in genetic erosion. Ten buffalo populations in Kenya and Uganda were examined using seventeen microsatellite markers to assess the regional genetic structure and the effect of protected area size on measures of genetic diversity. Two nested levels of genetic structure were identified: a higher level partitioning populations into two clusters separated by the Victoria Nile and a lower level distinguishing seven genetic clusters, each defined by one or two study populations. Although relatively small geographic distances separate most of the study populations, the level of genetic differentiation found here is comparable to that among pan‐African populations. Overall, correlations between conservancy area and indices of genetic diversity suggest buffalo populations inhabiting small parks are showing signs of genetic erosion, stressing the need for more active management of such populations. Our findings raise concerns about the future of other African savannah ungulates with lower population sizes and inferior dispersal capabilities compared with the buffalo.     

松山自然保护区森林群落的数量分类和排序

根据68个森林群落样方数据,采用双向指示种分析(TW INSPAN)方法,对松山自然保护区的森林群落进行分类和采用除趋势对应分析(DCA)、典范对应分析(CCA)方法进行排序。结果表明:(1)TW INSPAN将该区的森林群落分为13类型;(2)样方的DCA排序及样方和优势种的CCA排序较好地揭示了该区森林群落的分布格局与环境梯度的关系;CCA第一轴明显地反映出森林群落的海拔梯度、枯枝落叶层厚度和土壤深度变化,沿CCA第一轴从左到右,海拔逐渐升高,枯枝落叶层越厚和土壤越深;第二轴与海拔高度和坡度成正相关,而与土壤紧实度成负相关。其中海拔梯度是环境因子中对森林群落起决定性作用的因子。(3)与DCA相比,CCA的排序轴更有利于生态意义的解释,后者能同时反映样方间在种类组成上及环境因子组成上的相似性,表现在排序图中样方较集中,群落间的界线变得较模糊,因此如果排序同分类结合使用,DCA的效果要好于CCA。(4)TW INSPAN分类与DCA和CCA排序的结果,同时表明了该地区森林群落的垂直分布格局。     

大气热层结条件对林冠显热的影响

应用欧拉二阶闭合模型研究了大气热层结条件下森林冠层显热通量源汇分布和通量特征.结果表明:白天,冠层上的不稳定层结和冠层下的稳定层结是森林冠层大气层结的一种特有现象;温度廓线的变化表明林冠高度2/3处存在较强的热源;冠层内大气处于弱稳定状态时,热量继续向上输送,呈现出热通量的反梯度输送.显热通量日变化的模拟值与实测值吻合,其R2=0.9035(P0.01).在显热收支方程中添加浮力项,可提高反演模型在实际大气中的模拟精度,从而改善模型对热通量收支的模拟能力.     

不同模型对拟合大兴安岭林火发生与气象因素关系的适用性

选用符合林火发生数据结构的Poisson和零膨胀Poisson(ZIP)模型对大兴安岭林区1980—2005年间林火发生与气象因素关系进行建模分析,并与普通最小二乘回归(ordinary least squares,OLS)方法的结果进行了对比分析.结果表明:OLS模型对研究区域林火发生与气象因素关系的拟合结果较差(R2=0.215);Poisson和ZIP模型的拟合效果较好,具有较好的火灾次数预测能力,且ZIP模型的预测能力高于Poisson模型.运用AIC和Vuong检验方法对Poisson和ZIP模型的拟合水平进行进一步检验,表明ZIP模型的数据拟合度优于Poisson模型.