Soil pH and species diversity in coastal dunes

Soil pH was measured at two different spatial scales in coastal dunes on Norderney, North Sea, and in Mecklenburg-Vorpommern, Baltic Sea, Germany. Relationships between the variability in soil pH, species richness and species diversity are presented. Species richness and diversity were highest in grey dunes, where soil pH was at intermediate levels; both variables were lower in yellow and brown dunes. The variability in pH increased with increasing species diversity and also with scale. Overall, soil pH variability decreased with increasing vegetation cover. The lowest pH heterogeneity was found in heath dominated by Empetrum nigrum L. and grey dunes dominated by Campylopus introflexus (Hedw.) Brid. Increasing abundance of dominant species and decreasing species diversity of vegetation apparently reduces soil heterogeneity. Decreasing species diversity of vegetation is likely to explain decreasing variability in soil pH.     

松嫩平原羊草草地植物功能群组成及多样性特征对水淹干扰的响应

为研究草地植被对水淹干扰的响应 ,在松嫩平原羊草 (Aneurolepidiumchinense)草地 1998年部分遭受水淹的吉林省大安市三家甸子草场内设置了经历不同水淹强度的样带 ,并对这些样带的植被组成及物种多样性特征进行了比较研究。结果表明 :1)在植被的水分生态类型功能群组成中 ,随水淹干扰强度的增加 ,湿生、湿中生类植物功能群的优势度比例基本上是逐渐增加的 ,中生、中旱生类植物功能群的优势度比例则逐渐减小 ;2 )在植被的生活型功能群组成中 ,随水淹干扰强度的增加 ,一年生植物的优势度比例呈单峰型变化 ,地下芽植物比例增加 ,地面芽植物比例减小。某些单个物种优势度比例的不规则变化和功能群组成的规则变化表明 ,生态补偿作用不仅仅存在于植物群落的各个功能群之间 ,而且存在于同一功能群内部的不同物种之间 ;3)群落的物种丰富度、多样性在经历中等强度水淹干扰的样带上较高 ,而在未受干扰的对照样带和受干扰较为严重的样带都较低 ,这有力地支持了中度干扰假说。     

Gravel pits support waterbird diversity in an urban landscape

Few studies exist documenting changes in rotifer communities over long time intervals. Here, we explore seasonal and long-term variation in rotifer communities in four Polish lakes sampled in 1976 and again in 1997. Rarefied, asymptotic species richness did not differ significantly across study years, although values in 1997 tended to be higher. Simpson’s and Shannon–Wiener diversity measures provided inconsistent temporal results, with only the former indicating significantly higher richness in 1997. Sorensen’s coefficient of community similarity was as high among lakes in 1976 (0.81) and in 1997 (0.76) as within lakes across the 21-year span (0.77). Nonlinear redundancy analysis of species’ abundances revealed large, consistent seasonal changes across lakes, smaller consistent shifts between sampling periods, and small differences between lakes. Collectively, these metrics indicate that species composition was relatively stable among lakes within years and within lakes between years, while species’ abundance patterns were far more variable and most affected by season. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: S. I. Dodson     

Woody species diversity influences productivity and soil nutrient availability in tropical plantations

We investigated the relationship between plant diversity and ecological function (production and nutrient cycling) in tropical tree plantations. Old plantations (65–72 years) of four different species, namely Araucaria cunninghamii, Agathis robusta, Toona ciliata and Flindersia brayleyana, as well as natural secondary forest were examined at Wongabel State Forest, in the wet tropics region of Queensland, Australia. Two young plantations (23 years) of Araucaria cunninghamii and Pinus caribaea were also examined. The close proximity of the older plantations and natural forests meant they had similar edaphic and climatic conditions. All plantations had been established as monocultures, but had been colonised by a range of native woody plants from the nearby rainforest. The extent to which this had occurred varied with the identity of the plantation species (from 2 to 17 species in 0.1 ha blocks). In many cases these additional species had grown up and joined the forest canopy. This study is one of the few to find a negative relationship between overstorey plant diversity and productivity. The conversion of natural forest with highly productive, low-diversity gymnosperm-dominated plantations (young and old Araucaria cunninghamii and Pinus caribaea) was found to be associated with lower soil nutrient availability (approximately five times less phosphorus and 2.5 times less nitrogen) and lower soil pH (mean = 6.28) compared to the other, less productive plantations. The dominant effects of two species, Araucaria cunninghamii and Hodgkinsonia frutescens, indicate that ecosystem functions such as production and nutrient availability are not determined solely by the number of species, but are more likely to be determined by the characteristics of the species present. This suggests that monoculture plantations can be used to successfully restore some functions (e.g. nutrient cycling and production), but that the level to which such functions can be restored will depend upon the species chosen and site conditions. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The relationship between productivity and multiple aspects of biodiversity in six grassland communities

Biodiversity is a multifaceted concept but most studies examining the association between the biodiversity of a community and its productivity focus only on species richness. Consequently, studies are needed to examine how other facets of biodiversity vary with productivity if we want to have a better understanding of the distribution of biodiversity across our planet. We evaluated how a number of biodiversity measures (species richness, evenness, dominance, rarity, Simpson’s diversity, and Shannon–Weiner diversity) varied across natural productivity gradients at 6 grassland sites in the continental US. Variation in productivity did not account for a substantial amount of variation in any measure of biodiversity at small spatial scales (≈1 m²) at most sites. When productivity accounted for substantial variation in biodiversity, different measures of biodiversity responded to productivity in different ways. For example, dominance changed in a U-shaped fashion along a productivity gradient whereas richness increased in an asymptotic fashion. Consequently, diversity indices, which account for both species richness and evenness, varied in a hump-shaped fashion along the productivity gradient. Our results highlight that an exclusive focus on the association between species richness and productivity provides an incomplete picture of how a community’s biodiversity is related to its functioning.     

Multi-scale comparisons of cliff vegetation in Colorado

We developed a nested vegetation sampling protocol to sample the plant diversity on south-facing cliffs and cliff bases in Jefferson County, Colorado. The multi-scale plots included three nested spatial scales, 1 m², 20 m², and 40 m². We compared plant species richness and species diversity among large cliffs, medium cliffs, small cliffs, and non-cliff sites using Hill's diversity numbers (N ₀, N ₁, and N ₂) for the 1-m² quadrats. Species richness (N ₀) was calculated for the 20-m² and 40-m² plots. Our results indicate that plant species diversity on the cliff faces did not increase with increasing cliff area. This pattern was consistent at all three sampling scales. A model selection was run to determine if plant species diversity values on the cliff faces were associated with cliff variables. None of the cliff variables measured were good predictors of diversity at the 1-m² scale. However, at the 20-m² scale, canyon differences and a positive relationship with increasing cliff surface roughness explained 70% of the variability in species richness. Although most plant species sampled on the cliff faces were also found in the base plots, 13 species were sampled only on the cliff faces. Additionally, dry south facing cliffs support a mix of xeric and mesic plants indicating that cliffs may provide unique microenvironments for plant establishment. This revised version was published online in August 2006 with corrections to the Cover Date.     

A new family of Fisher-curves estimates Fisher's alpha more accurately

Fisher's alpha is a satisfactory scale-independent indicator of biodiversity. However, alpha may be underestimated in communities in which the spatial arrangement of individuals is strongly clustered, or in which the total number of species does not tend to infinity. We have extended Fisher's curve to allow for an accurate calibration of Fisher's alpha in such communities. In spite of its good performance, the use of this extended curve is complicated by its optimization procedure. Therefore, we have simulated the extended Fisher curve by modifying the smooth expolinear curve, using three ecologically meaningful parameters only, i.e. Fisher's alpha, a coefficient describing the effects of clustering and the maximum number of species. The resulting equations successfully describe species-individual relationships from both spatial and temporal observations on both plant and animal communities. This family of equations combines three advantages: Fisher's alpha can be quantified more accurately, the number of estimated parameters is flexible and can be kept to a minimum, while all parameters can legitimately be compared across sites.     

The effects of forest disturbance on diversity of tropical soil nematodes

We provide the first account of the effects of forest disturbance on species richness of nematodes in tropical forest soils, from 24 sites along gradients of disturbance and regeneration in the Mbalmayo Forest Reserve, Cameroon. Species richness was very high. Samples of 200 nematodes from individual soil cores contained a maximum of 89 and an average of 61 species; in total we recorded 431 species and approximately 194 genera. The model of Siemann et al. (1996), predicting that species richness scales as the number of individuals I ^0.5, underestimates nematode diversity 4–6 fold in these samples. Over 90% of specimens cannot be assigned to known species. Although nematode species richness declined with forest disturbance, statistically significant effects were detectable only under the most extreme conditions (active slash-and-burn agriculture and complete mechanical forest clearance) and even here remained at 40% of the richness of near primary sites. Impacts on trophic structure were also small, and there were no significant changes in the maturity index (MI) (Bongers 1990) with disturbance (mean MI across all treatments was very high, at 3.58). In the light of this study, the problems of completing reliable all-taxon inventories in tropical forests are briefly discussed. Received: 22 July 1996 / Accepted: 3 April 1997     

祁连山区不同海拔草地群落的物种多样性

依据植物在各海拔带出现的频率和不同海拔带植物种的生活型,对祁连山区草地群落海拔2500～3000m的物种α多样性变化特征进行了研究．结果表明,随海拔升高,Shahnon-Wiener指数从1．432上升到1．832,Simpson指数的变化较为复杂．海拔2701～2800m带是物种多样性的一个重要转折点,是物种多样性较丰富的地带．在祁连山草地群落中,有毒的与食性较差的物种在各海拔带所占比例均超过50％,生物量占到整个样地生物量的60％以上,物种多样性已呈现衰退．     

Does cross-taxon analysis show similarity in diversity patterns between vascular plants and bryophytes? Some answers from a literature review

The objective of this study was to clarify the taxon surrogacy hypothesis relative to vascular plants and bryophytes. A literature review was conducted to obtain papers that met the following criteria: (i) they examined species richness values; or (ii) they evaluated the species richness within the same study sites, or under the same spatial variation conditions. Twenty-seven papers were accessed. The richness of the two taxa, compared in 32 cases, positively co-varied in about half of the comparisons. The response to the spatial variation in environmental or human-induced factors of the two taxa in terms of species richness was rather variable. Based on current knowledge, the main documented findings regard forest habitats and nival gradients. In forest habitats, co-variation in species richness is likely when similar environments are analysed and seems to be strengthened for boreal forests. Along the nival gradient, a different response in terms of richness of the two taxa suggests that vascular plants cannot be considered good surrogates for bryophytes.     

高寒草甸植物群落中物种丰富度与生产力的关系研究

 以物种组成较为复杂的青藏高原东部地区典革高寒草甸植物群落为背景,从不同的时间和空间尺度水平研究了植物群落中物种丰富度与生产力（地上部生物量）关系的基本模式。结果表明：1）总体而言,高寒草甸植物群落中物种丰富度与生产力的关系呈对数线性增加关系,这实际上是空间和时间尺度放大时在时间和空间尺度的相互作用下高寒草甸植物群落中物种丰富度与生产力关系的一种总体模式;2）随着研究的时间和空间尺度的改变,物种丰富度与生产力的关系会发生一些相应的变化,但空间尺度比时间尺度对物种丰富度与生产力的关系造成的影响更为显著,这可能