Comment on "Productivity is a poor predictor of plant species richness"

Adler et al. (Reports, 23 September 2011, p. 1750) analyzed the standardized sampling data from 48 herbaceous-dominated plant communities and concluded that "Productivity is a poor predictor of plant species richness" at fine-scale. However, their method was biased toward site-number-dominated plant communities. They also failed to provide enough data for regional analysis and detailed information for within-site analysis.     

Corridors increase plant species richness at large scales

Habitat fragmentation is one of the largest threats to biodiversity. Landscape corridors, which are hypothesized to reduce the negative consequences of fragmentation, have become common features of ecological management plans worldwide. Despite their popularity, there is little evidence documenting the effectiveness of corridors in preserving biodiversity at large scales. Using a large-scale replicated experiment, we showed that habitat patches connected by corridors retain more native plant species than do isolated patches, that this difference increases over time, and that corridors do not promote invasion by exotic species. Our results support the use of corridors in biodiversity conservation.     

塞罕坝植物物种丰富度海拔分布格局

物种多样性一直是生态学研究的热点,而物种丰富度的海拔分布格局是物种多样性研究的一个重要内容。以塞罕坝机械林场的天然植被为研究对象,探讨塞罕坝地区植物的物种组成以及物种丰富度的海拔分布格局。结果表明:(1)在研究区调查的184块样地中,共有维管植物53科、197属、365种,分别占该地区总数的65.4%、63.1%和59.1%。其中乔木8科、12属、16种;灌木11科、23属、43种;藤本1科、1属、2种;草本41科、108属、304种。该区优势科、属明显,优势科主要有菊科、禾本科、蔷薇科、豆科、唇形科。大部分的科内,属、种缺少,区域单属科以及单种科比例高,体现出该区地理环境复杂的特点。(2)物种丰富度为草本层灌木层乔木层;随着海拔的升高,科、属、种以及乔木的变化不显著;灌木丰富度随海拔的变化出现先升高后降低的单峰格局,即中度海拔物种丰富度最高。草本层丰富度总体趋势是随海拔升高而升高。     

阿拉善高原植物区域物种丰富度格局及其环境解释

目的阿拉善高原境内分布着超过20万km2典型的温带荒漠生态系统,这些荒漠生态系统对全球气候与土地利用类型的变化极其敏感,然而水分、能量与生境异质性对该区植物区域物种丰富度的相对影响,以及这种影响在不同生活型植物间的差异还没有得到系统研究。方法本文利用阿拉善高原大尺度植物区域物种丰富度数据,并结合相关的气候与生境异质性数据,尝试系统地探讨阿拉善高原植物区域物种丰富度地理格局及其潜在的影响因素。结果（1）阿拉善高原植物区域物种丰富度存在显著的经纬度格局,全部物种、草本植物与木本植物区域物种丰富度均呈现出沿经度的升高而增加,沿纬度的升高而递减的变化趋势。（2）方差分解结果显示,水分与能量因子共同解释了全部物种、草本植物与木本植物区域物种丰富度60.7%、62.5%及42.6%的空间变异; 两者单独的解释率分别为15.2% ~ 19.6%与2.8% ~ 5.3%。生境异质性分别解释了3组植物区域物种丰富度17.2%、12.3%、29.3%的变异,其单独解释率分别为3.1%、1.0%和11.8%。气候因素与生境异质性对草本植物与木本植物区域物种丰富度的相对影响并不一致;草本植物物种丰富度主要由气候因素决定,而木本植物丰富度则受气候因素与生境异质性的共同控制。（3）气候与生境异质性三者共同解释了区域物种丰富度54.4% ~ 63.8%的变异,但仍然有36.2% ~ 45.6%的变异没有得到解释。结论阿拉善高原植物区域物种丰富度格局由水分与能量类气候因子共同决定,水资源可用性是阿拉善地区植物物种多样性维持最为关键的限制因子。生境异质性对阿拉善高原植物丰富度,尤其是木本植物丰富度有着不可忽略的作用,是干旱区植物多样性维持的重要影响因素。阿拉善高原不同生活型植物区域物种丰富度的影响因素可能并不一致,其他未知潜在因素对阿拉善植物区域物种丰富度亦存在着重要影响。      

Geographic range size and determinants of avian species richness

Geographic patterns in species richness are mainly based on wide-ranging species because their larger number of distribution records has a disproportionate contribution to the species richness counts. Here we demonstrate how this effect strongly influences our understanding of what determines species richness. Using both conventional and spatial regression models, we show that for sub-Saharan African birds, the apparent role of productivity diminishes with decreasing range size, whereas the significance of topographic heterogeneity increases. The relative importance of geometric constraints from the continental edge is moderate. Our findings highlight the failure of traditional species richness models to account for narrow-ranging species that frequently are also threatened.     

Impact of nitrogen deposition on the species richness of grasslands

A transect of 68 acid grasslands across Great Britain, covering the lower range of ambient annual nitrogen deposition in the industrialized world (5 to 35 kg Nha-1 year-1), indicates that long-term, chronic nitrogen deposition has significantly reduced plant species richness. Species richness declines as a linear function of the rate of inorganic nitrogen deposition, with a reduction of one species per 4-m2 quadrat for every 2.5 kg Nha-1 year-1 of chronic nitrogen deposition. Species adapted to infertile conditions are systematically reduced at high nitrogen deposition. At the mean chronic nitrogen deposition rate of central Europe (17 kg Nha-1 year-1), there is a 23% species reduction compared with grasslands receiving the lowest levels of nitrogen deposition.     

Plant species richness and ecosystem multifunctionality in global drylands

Experiments suggest that biodiversity enhances the ability of ecosystems to maintain multiple functions, such as carbon storage, productivity, and the buildup of nutrient pools (multifunctionality). However, the relationship between biodiversity and multifunctionality has never been assessed globally in natural ecosystems. We report here on a global empirical study relating plant species richness and abiotic factors to multifunctionality in drylands, which collectively cover 41% of Earth's land surface and support over 38% of the human population. Multifunctionality was positively and significantly related to species richness. The best-fitting models accounted for over 55% of the variation in multifunctionality and always included species richness as a predictor variable. Our results suggest that the preservation of plant biodiversity is crucial to buffer negative effects of climate change and desertification in drylands.     

Polar desert adaptations of a high arctic plant species

Plants of Saxifraga oppositifolia (Saxifragaceae) possess metabolic adaptations that allow them to grow successfully in polar desert microenvironments. Net photosynthesis (net carbon uptake) continues to be positive during drought until the leaf water stress declines to the range of -21 to -29 bars, which is considerably below the nonstress range of 0 to -10 bars. The plants can survive leaf water stresses of at least -44 bars in the field and leaf water stresses of -55 bars in a growth chamber.     

The nature of plant species

The species concept is a central tenet of biological diversity. Attempts to describe diversity have led to empirical concepts of species based on assumptions found wanting for plants. Plant species lack reality, cohesion, independence, and simple evolutionary or ecological roles. The concept of species for plant taxonomists and evolutionists can only serve as a tool for characterizing diversity in a mentally satisfying way. Diversity is idiosyncratic. ft is impossible to reconcile idiosyncrasy with preconceived ideas of diversity. The search for hidden likenesses is unlikely to yield a unifying species concept. The concept that is most operational and utilitarian for plants is a mental abstraction which orders clusters of diversity in multidimensional character space.     

Global correlations in tropical tree species richness and abundance reject neutrality

Patterns of species richness and relative abundance at some scales cannot be distinguished from predictions of null models, including zero-sum neutral models of population change and random speciation-extinction models of evolutionary diversification. Both models predict that species richness or population abundance produced by independent iterations of the same processes in different regions should be uncorrelated. We find instead that the number of species and individuals in families of trees in forest plots are strongly correlated across Southeast Asia, Africa, and tropical America. These correlations imply that deterministic processes influenced by evolutionarily conservative family-level traits constrain the number of confamilial tree species and individuals that can be supported in regional species pools and local assemblages in humid tropical forests.     

广东省自然保护区物种丰富度与环境因子的关系

物种丰富度是反映物种多样性的指标之一,研究物种丰富度与环境因子的关系对自然保护区的发展、规划和管理具有重要意义.研究选取广东省已经进行过深入调查的19个自然保护区为样本,对物种丰富度(科数、属数和种数)及环境因子(经度、纬度、海拔、年均温度、无霜期、年均降雨量、相对湿度、面积)的关系进行分析.结果表明,物种丰富度与经度呈显著负相关,与海拔呈显著正相关.     

南海陆坡沉积物细菌丰度预测

分别利用参数模型和无参数估计法预测南海陆坡沉积物柱MD05-2896中的细菌丰度.基于非培养的PCR-RFLP的16SrRNA基因分子技术,扩增了沉积物柱中的细菌16S rRNA基因序列,并构建16S rRNA基因文库.系统发育分析表明16S rRNA基因文库中,大多数序列属于17个已知的“门”.分别以99％、97％、90％和80％序列一致性作为分类单元分界点,将16SrRNA基因序列组群为分类单元.使用逆高斯分布模型、对数正态分布模型、负二项式分布模型、帕雷托分布模型、双指数分布模型以及ACE、ACE-1等估计方法预测不同分类单元分类水平下的细菌丰度.结果表明在“种”级分类水平上,负二项式分布为最优估计模型,估计细菌丰度为244±10(SE).不过,受实验条件的限制,该估计值可能偏低.     

Comparative species richness in fluctuating and constant environments: coral-associated decapod crustaceans

The number of decapod species associated with the coral Pocillopora damicornis is compared between two regions on the Pacific coast of Panama which are of the same geologic age but differ in environmental characteristics. The relationship between number of species and coral head size does not differ between the two regions but species composition among coral heads is more variable in the fluctuating environment. Thus there are more species (55 compared to 37) associated with corals in the fluctuating environment than in the constant environment. These data impugn the concept that environmental constancy increases species richness. They support the hypothesis that species equilibrium within habitats is maintained by measurable ecological factors-in this case, the effects of a natural physical disturbance.     

平潭周边海岛植物丰富度、相似度与岛屿空间特征的关系

[目的]了解平潭周边海岛植物丰富度及相似度与岛屿空间特征之间的关系。[方法]对平潭周边16座岛屿设置样方进行植被调查,统计了各岛屿植物物种丰富度及岛屿间的植物物种相似度,并利用典型相关分析及多元回归分析海岛植物物种丰富度及相似度与岛屿空间特征的关系。[结果]典型相关分析表明,海岛面积、岸线长度、海岛海拔与乔木、蕨类植物和1、2年生草本丰富度正相关;周长面积比与藤本植物丰富度负相关。多元回归分析表明,周长比、与海坛岛(平潭主岛)距离比与相似度正相关;海岛面积比、海岛类型与海岛植物物种相似度负相关。[结论]平潭周边海岛中面积越大、岸线长度越长、海拔越高的岛屿,其乔木、蕨类植物和1、2年生草本植物丰富度越高;周长面积比与植物物种丰富度成反比,周长面积比越大的岛屿其藤本植物丰富度越低;岛屿与海坛岛的距离、岛屿岸线长度越相近,海岛开发程度越强,其植物物种相似度越高。     

生物柴油树种评价与筛选

在福建省乡土油料树种资源调查的基础上,提出了福建生物柴油树种筛选的主要标准:种子含油率≥30%,种子千粒重≥100 g,脂肪酸组成中C16和C18的总量大于50%。对乌桕、无患子等20种传统油料树种进行3个指标多层次的联合选择,初步确定麻疯树、乌桕、野茉莉、蓖麻、无患子、竹柏可作为植物源生物柴油树种,其种子含油率为30.0%-54.1%,种子千粒重109.9-137.3 g,油脂脂肪酸组成中C16和C18的总量为58.2%-100.0%、酸值为1.29-63.6 mg.g-1、皂化值为151.9-205.7 mg.g-1。     

Comment on "Plant species richness and ecosystem multifunctionality in global drylands"

Maestre et al. (Reports, 13 January 2012, p. 214) reported a general, but weak, positive relationship between plant diversity and ecosystem multifunctionality in global drylands. We show that the strength of this relationship changes consistently along multiple environmental gradients, becoming strongly positive in stressed habitats. This suggests that biodiversity loss may have especially strong consequences in harsh environments.     

补播对玛曲高寒沙化草地物种丰富度和生物量的影响

【目的】研究补播对玛曲高寒沙化草地物种丰富度和生物量的影响。【方法】于2006和2007年在甘肃玛曲高寒沙化草地进行禾草补播试验。【结果】补播当年物种丰富度增加,补播第2年物种丰富度下降。补播后,禾草类生物量一直占据主要部分,补播后地上生物量比对照显著增加。2007年生长季各处理的地上生物量均高于2006年,3种禾草混播处理对草地地上生物量的提高最显著。【结论】中华羊茅、草地早熟禾和垂穗披碱草3种禾草混播的处理可作为玛曲高寒沙化草地的补播组合。     

Mutual feedbacks maintain both genetic and species diversity in a plant community

The forces that maintain genetic diversity among individuals and diversity among species are usually studied separately. Nevertheless, diversity at one of these levels may depend on the diversity at the other. We have combined observations of natural populations, quantitative genetics, and field experiments to show that genetic variation in the concentration of an allelopathic secondary compound in Brassica nigra is necessary for the coexistence of B. nigra and its competitor species. In addition, the diversity of competing species was required for the maintenance of genetic variation in the trait within B. nigra. Thus, conservation of species diversity may also necessitate maintenance of the processes that sustain the genetic diversity of each individual species.