Species richness patterns in the understorey of Pyrenean Pinus sylvestris forest

Abstract. Species richness was studied in the understorey of natural Pinus sylvestris forest in the eastern Pyrenees. Understorey plant species were grouped in three structural groups as woody species, herbs and mosses. The response curves of total species richness and species richness of each structural group were fitted against environmental and stand-structural parameters, using Generalized Linear Models. The results suggested that, to predict species richness, environmental parameters were more important than tree-canopy structural parameters, in particular incoming radiation and soil nutrient concentration. The species richness response curve was often humped in relation to soil nutrient concentration. Different patterns of species richness were found for each structural group.     

Preferences of dead wood inhabiting bryophytes for decay stage,log size and habitat types in Hungarian beech forests

Abstract

This study describes the quantitative preferences of epixylic bryophytes for decay stages, log size and habitat type. The two habitats investigated were zonal (situated on plateaux without extreme microclimatic conditions) and ravine-like near-natural beech stands. Preferences of 30 bryophyte species are described using logistic regression modelling. The species pool differed between habitat types. In the ravine-like forests more species are found. Regionally rare epixylic species (mainly liverworts) were limited to these forests. The species richness of individual logs was also higher in the ravine-like than in the zonal forests and the proportion of logs of all sizes colonized by bryophytes was higher in the former. The species were classified into four categories on the basis of their preference for decay stages: strict epixylics, indifferent species, preferential epixylics and epiphytes. The epixylics and preferential epixylics prefer advanced decay stages while the latter extend further into earlier decay stages than strict epixylics. Common epixylic species have a wider tolerance to decay stage than rare ones. Probabilities of species occurrence increase with log size, more strongly in zonal stands than in ravines. A simple successional scheme for bryophyte succession on dead wood is proposed on the basis of the observed species responses.     

Species richness and distribution patterns of leaf-inhabiting endophytic fungi in a temperate forest canopy

In 2005, researchers at the Leipzig Canopy Crane Research Facility collected living leaves of four temperate tree species at heights of between 15 and 33 m above the ground. Following surface sterilisation of the leaves, leaf-fragments were cultured on malt extract agar which allowed the growth of endophytic fungi into the surrounding medium. Isolated cultures were identified by morphology and sequence analysis of the D1/D2 region of the large subunit rDNA. Phylogenetic analysis established the taxonomic positions of the fungi. A total of 49 different taxa were identified, representing 20 families and ten orders. With the exception of one basidiomycetous yeast, all taxa belonged to filamentous ascomycetes. Species richness was highest on Tilia cordata and lowest on Quercus robur. Species-accumulation curves showed that the sampling effort was not sufficient to cover the majority of the likely species at the investigation site. Most endophytes proved to be ubiquitous within the canopy of the investigation site, but habitat preferences in terms of different tree species, different light regimes and season (sampling times) were obvious for some abundant endophytes. Apiognomonia errabunda and Aspergillus niger occurred predominantly on Q. robur, Diplodina acerina on Acer pseudoplatanus, one species of Phoma significantly prefered shaded leaves from the lower canopy layer whereas Sordaria fimicola prefered sun-exposed leaves from the upper tree crowns. Seasonal patterns were observed, for example, for A. errabunda, which was abundant in young leaves in the spring and almost completely absent in aged autumn-leaves, thus suggesting the accumulation of antifungal secondary plant metabolites during the growing season. Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users. Wilfried Morawetz died in March 2007.     

Species richness and spatial distribution of blackflies (Diptera: Simuliidae) in streams of Central Amazonia, Brazil

1. The spatial distribution and species richness of blackflies were evaluated at 58 stream sites in Central Amazonia, Brazil. Samples were taken along a north–south axis of approximately 130 km and a east–west axis of approximately 220 km.
2. Based on stream-site characteristics, the occurrence of larvae of the six most frequently collected species was highly predictable (79.3–91.5% accuracy in prediction of occurrence). The predictive value of stream size and the presence of impoundments agrees with results of similar work in the Holarctic Region, suggesting a general responses of blackflies to environmental parameters.
3. Although only 19.0% of interstream variation in species richness was explained by a regression model, results suggested that species richness was greater in larger, cooler, faster, covered streams with rocky beds than in smaller, warmer, slower, open streams with sandy bottoms. Overall, the species richness of blackflies (11 species in total) was lower than in the temperate zone suggesting, for some taxa at least, that aquatic communities do not follow the terrestrial pattern of greater species richness in the tropics.     

中国苔藓植物的地理分区及分布类型

在对中国苔藓植物相关研究资料进行总结归纳的基础上,对中国苔藓植物的分区进行了重新划分,将最初的7个分区划分为10个分区,从华中区中分出华东区,由华北区中分出华西区,并将青藏区及云贵区内的云南西北部、四川西南部和西藏东南部组成单独的横断山区。就中国苔藓植物的分布类型及可能的分布路线也作了讨论,指出中国苔藓植物的分布路线有3条,一条是从喜马拉雅地区经滇西北、川西沿长江流域到中国的东南部;一条位于喜马拉雅、横断山区和台湾之间;第三条则从喜马拉雅地区通过秦岭直至长白山区。     

Effects of river level fluctuation on plant species richness, diversity, and distribution in a floodplain forest in Central Amazonia

River levels in Central Amazonia fluctuate up to 14 m annually, with the flooding period ranging from 50 to 270 days between the rising and falling phases. Vast areas of forest along the rivers contain plant species that are well adapted to annual flooding. We studied the effect of flooding level on tree species richness, diversity, density, and composition in lake, river, and stream habitats in Jaú National Park, Brazil. 3051 trees >10 cm diameter (at 1.3 m diameter at breast height, dbh) were measured and identified in 25 10 m × 40 m randomly selected plots in each habitat. Ordination methods and analysis of variance results showed that forested areas near lakes had significantly lower species richness of trees than riverine and streamside habitats. Plot species richness and diversity were strongly negatively correlated with the water level and duration of flooding. The drier (stream) habitat had more total species (54 species of trees) and more unique species of trees (6 tree species) than the riverine (52 tree species; 3 unique species) and lake (33 tree species; 3 unique species) habitats. Species composition overlap among habitats was surprisingly high (42.6–60.6% overlap), almost one-third of the species were found in all three habitat types, and few species were unique to each habitat. We conclude that: (1) duration of flooding has a strong impact on species richness, diversity and plant distribution patterns; (2) most species are adapted to a wide range of habitats and flood durations; and (3) while flood duration may decrease local diversity, it also creates and maintains high landscape-scale diversity by increasing landscape heterogeneity. Received: 20 April 1997 / Accepted: 14 January 1999     

Light and warming drive forest understorey community development in different environments

Plant community composition and functional traits respond to chronic drivers such as climate change and nitrogen (N) deposition. In contrast, pulse disturbances from ecosystem management can additionally change resources and conditions. Community responses to combined environmental changes may further depend on land‐use legacies. Disentangling the relative importance of these global change drivers is necessary to improve predictions of future plant communities. We performed a multifactor global change experiment to disentangle drivers of herbaceous plant community trajectories in a temperate deciduous forest. Communities of five species, assembled from a pool of 15 forest herb species with varying ecological strategies, were grown in 384 mesocosms on soils from ancient forest (forested at least since 1850) and postagricultural forest (forested since 1950) collected across Europe. Mesocosms were exposed to two‐level full‐factorial treatments of warming, light addition (representing changing forest management) and N enrichment. We measured plant height, specific leaf area (SLA) and species cover over the course of three growing seasons. Increasing light availability followed by warming reordered the species towards a taller herb community, with limited effects of N enrichment or the forest land‐use history. Two‐way interactions between treatments and incorporating intraspecific trait variation (ITV) did not yield additional inference on community height change. Contrastingly, community SLA differed when considering ITV along with species reordering, which highlights ITV’s importance for understanding leaf morphology responses to nutrient enrichment in dark conditions. Contrary to our expectations, we found limited evidence of land‐use legacies affecting community responses to environmental changes, perhaps because dispersal limitation was removed in the experimental design. These findings can improve predictions of community functional trait responses to global changes by acknowledging ITV, and subtle changes in light availability. Adaptive forest management to impending global change could benefit the restoration and conservation of understorey plant communities by reducing the light availability.     

Distance Decay of Tree Species Similarity in Protected Areas on Terra Firme Forests in Colombian Amazonia

In this study, we investigated the pattern of floristic similarity as a function of geographical distances and environmental variability in well-drained uplands (terra firme) in Colombian Amazonia. The study site comprised three National Natural Parks, Tinigua, Chiribiquete, and Amacayacu, located in different geological units that represent a soil fertility gradient linked to parental materials. Differences in species richness between sites were compared using rarefaction analysis. A clear floristic transition appeared in the east–west direction following a soil fertility gradient along the first PCoA axis. In multiple regression analyses based on distance matrices, both geographical distances and geology explained 64 percent of the total floristic variation. Geographical distances alone accounted for 12 percent of variation in floristic similarities among plots, while geology alone accounted for 1 percent, and the joint effect of both explained 51 percent of the floristic variation. The species richness trend supports the existence of a latitudinal corridor southward of the geographical Equator in the Amazon basin, where tree diversity reaches the maximum expected values. A coupled effect of stochastic dispersal limitation and habitat specialization would certainly appear to be an appropriate explanation for tree species turnover in terra firme forests in Colombian Amazonia, strongly emphasizing that competition and neutrality must be supplementary rather than mutually exclusive processes. This result pinpoints the effect of dispersal on floral mixing as an ongoing active process for structuring tree communities in NW Amazonia, and the size of the reserves as a relevant issue to protect rare species from extinction by chance.
     

不同森林类型根系分布与土壤性质的关系

在红壤丘陵区选取8种典型森林类型,对不同土层深度、不同径级的根长密度分布特征、根长分维数,以及根系特征与土壤容重、有机碳、全氮的关系进行了研究。结果表明:马尾松低效林根长密度最小,杉木低效林和湿地松林较大,表层土壤根长密度与灌草覆盖度显著相关(r=0.793,P<0.05)。各种森林类型的根长密度随着土壤深度的增加均表现为递减规律,但随深度的增加,不同森林类型的差异逐步缩小,且植物种类及生长状况对根长密度分布的影响越来越小。在相同的土层中,根长密度随径级的变化并不一致,马尾松低效林0相似文献   

Drivers of understorey biomass: tree species identity is more important than richness in a young forest

林下生物量影响因素：幼龄林树种特性比丰富度更重要 生物多样性与生态系统功能的正相关关系已被广泛报道,其主要来源于对草原生态系统的研究。然而,该结论并不一定适用于更复杂的环境,例如具有不同垂直层次的森林。举例而言,已有研究表明上层乔木树种丰富度与林下生产力降低有关。树种丰富度是否会通过增加(由于生境异质性)或降低(通过增强竞争)资源的可利用性进而影响林下生产力,以及林下生产力是否受树种特性的影响更大,这些影响机制都可能会随着时间的推移而改变。此外,研究还表明,丰富度-生产力关系随着环境背景的变化而改变。本研究利用可以操控树种丰富度的实验林场研究了这些不同垂直层位里的时间和环境动态。在中国亚热带森林生物多样性与生态系统功能(BEF-China)研究计划的框架下,我们在3年时间里沿树种丰富度梯度反复采集林下生物量样本,研究了不同环境处理中树种丰富度、树种特性和时间对林下生物量的影响。尽管我们发现乔木层特性对林下生物量有显著和一致的影响,但是树种丰富度对后者却不具有这种影响。另外,在森林结构层之间,可能并不存在单一的、具有普遍性的上层乔木树种丰富度与林下生产力的相关关系,并且与上层乔木相关的环境因素(如透光率)对林下生产力的贡献程度会随着时间而变化。总体而言,我们的结果表明,在研究森林结构层之间的关系时应将时间动态变化考虑在内。     

Alterations in flood frequency increase exotic and native species richness of understorey vegetation in a temperate floodplain eucalypt forest

The delivery of environmental flows for biodiversity benefits within regulated river systems can potentially contribute to exotic weed spread. This study explores whether exotic plants of a floodplain forest in Victoria, Australia, are characterised by specific functional groups and associated plant traits linked to altering hydrological conditions over time. Permanently marked 20 × 20 m² plots from five wetland sites in Eucalyptus camaldulensis floodplain forest were sampled twice, first in the early 1990s (1993–1994) and then 15 years later (2007–2008). Species cover abundance data for understorey vegetation communities were segregated by season and analysed using ordination analysis. Exotic species richness was modelled as a function of site flooding history and native species richness using general linear models. Site ordinations by detrended correspondence analysis showed differential community compositions between survey dates, but native and exotic species were not clearly differentiated in terms of DCA1 scores. Most exotics belonged to functional groups containing annual species that germinate and reproduce under drier conditions. Exotics reproducing under wetter conditions were in the minority, predominantly perennial and capable of both sexual and asexual reproduction. Site flooding history and native species richness significantly predicted exotic species richness. Vegetation changes are partially structured by reduced flood frequency favouring increased abundance of exotic, sexually reproducing annuals at drier sites. Sites of low flood frequency are more sensitive to future exotic weed invasion and will require targeted management effort. Flow restoration is predicted to benefit propagule dispersal of species adopting dual regeneration strategies, which are predominantly natives in this system.     

Species richness and abundance of forest birds in relation to radiation at Chernobyl

The effects of low-level radiation on the abundance of animals are poorly known, as are the effects on ecosystems and their functioning. Recent conclusions from the UN Chernobyl forum and reports in the popular media concerning the effects of radiation from Chernobyl on animals have left the impression that the Chernobyl exclusion zone is a thriving ecosystem, filled with an increasing number of rare species. Surprisingly, there are no standardized censuses of common animals in relation to radiation, leaving the question about the ecological effects of radiation unresolved. We conducted standardized point counts of breeding birds at forest sites around Chernobyl differing in level of background radiation by over three orders of magnitude. Species richness, abundance and population density of breeding birds decreased with increasing level of radiation, even after controlling statistically for the effects of potentially confounding factors such as soil type, habitat and height of the vegetation. This effect was differential for birds eating soil invertebrates living in the most contaminated top soil layer. These results imply that the ecological effects of Chernobyl on animals are considerably greater than previously assumed.     

Activity and ranging patterns of Colombian woolly monkeys in north-western Amazonia

In this study, I revise three aspects of the socioecology of woolly monkeys (genus Lagothrix) that might give us a better understanding of the patterns found in this species: (1) the association between temporal variation in fruit abundance and diet, activity, and ranging patterns; (2) the individual trade-offs associated with living in small or large groups, and (3) the relationship between social dominance and foraging success. Using behavioral and ecological data collected during 3 years in Tinigua Park, Colombia, I found that woolly monkeys tend to avoid open-degraded forests, where fruit production is generally lower than it is in mature forests. Diet and activity budgets were highly associated with temporal patterns of fruit production. Daily path length was positively correlated with group size and monthly fruit abundance, and negatively correlated with habitat quality. I found differences in activity budgets and the diet preferences of different age/sex classes. For example, adult males rest more and juveniles play more than other classes. Juveniles and adult females without infants look for arthropods more often than adult males and females with young infants, who showed the highest frequencies of fruit feeding. Dominant adult males were not consistently the most efficient foragers on fruits according to two different indexes. Most of these results are consistent with the expectations from strong intra-group competition for resources. However, females with infants received benefits during feeding similar to those of dominant adult males, which may be mediated by differential aggression from males to other group members (juveniles and females without infants).     

Avian distribution in treefall gaps and understorey of terra firme forest in the lowland Amazon

We compared the bird distributions in the understorey of treefall gaps and sites with intact canopy in Amazonian terra firme forest in Brazil. We compiled 2216 mist-net captures (116 species) in 32 gap and 32 forest sites over 22.3 months. Gap habitats differed from forest habitats in having higher capture rates, total captures, species richness and diversity. Seventeen species showed a significantly different distribution of captures between the two habitats (13 higher in gap and four higher in forest). Gap habitats had higher capture rates for nectarivores, frugivores and insectivores. Among insectivores, capture rates for solitary insectivores and army ant followers did not differ between the two habitats. In contrast, capture rates were higher in gaps for members of mixed-species insectivore flocks and mixed-species insectivore–frugivore flocks. Insectivores, especially members of mixed-species flocks, were the predominant species in gap habitats, where frugivores and nectarivores were relatively uncommon. Although few canopy species were captured in gap or forest habitats, visitors from forest mid-storey constituted 42% of the gap specialist species (0% forest) and 46% of rare gap species (38% forest). Insectivore, and total, captures increased over time, but did so more rapidly in gap than in forest habitats, possibly as a response to gap succession. However, an influx of birds displaced by nearby timber harvest also may have caused these increases. Avian gap-use in Amazonian terra firme forests differs from gap-use elsewhere, partly because of differences in forest characteristics such as stature and soil fertility, indicating that the avian response to gaps is context dependent.     

Species richness and distribution of eastern Australian lake chironomids and chaoborids

1. Chironomids and chaoborids were collected across eastern Australia and Tasmania in dune, glacial, sinkhole and maar lakes. Based on sampling exuviae from these relatively undisturbed freshwater lakes, we observed that species richness on the Australian continent was substantially greater than previously reported, and challenge the long‐standing view that chironomid species richness is depauperate in Australian lakes, compared with the northern hemisphere. 2. While chironomid species richness was equivalent across the four geographical regions sampled (tropical northern Queensland, Fraser Island, south‐eastern mainland Australia and Tasmania), there were only five ‘cosmopolitan’ species found across all regions. In general, species distributions were more closely associated with geographical region than with lake characteristics, and there were species assemblage differences among biogeographical regions. More than half of the 134 identified species were restricted to a single geographical region. Overall, Tasmanian lakes had the highest proportion of locally endemic species. 3. Latitude and altitude more strongly influenced species assemblages than did lake chemistry, although species richness sometimes varied among lake geomorphic types within a region.     

六种人工针叶幼林下地表苔藓植物生物量与碳贮量

调查了岷江上游6种人工针叶幼林(油松林、华山松林、日本落叶松林、云杉林、油松-华山松混交林和云杉-华山松混交林)下地表苔藓植物生物量,测定了C含量并估计了林分地表苔藓植物C贮量,比较分析了它们的差异性.结果表明,6种人工针叶幼林下地表苔藓植物总生物量在3.11～460.36 kg·hm^-2之间,而平均C含量在37.44±0.21%～3.9±0.70%之间,总C贮量在1.12±0.03～168.9±0.92 kg·hm^-2之间,但在样方水平上只有云杉林地表苔藓植物生物量与其它林型间差异明显,落叶松林下C含量与其它差异明显(P＜0.0).6种人工林类型中,云杉林地表苔藓植物总生物量和C贮量最高,华山松林下最低.综合分析表明,样方调查数量与布局对生物量取样精度有重要影响,岷江上游人工林下地表苔藓植物生物量与C贮量较低,林分类型与林分特征有重要影响,而疏伐、修枝等措施是改善人工密林下地表苔藓植物发育,增加生物量与C贮量的有效管理措施.     

闽西北不同类型毛竹林养分分布及生物循环特征

以福建省永安市集约经营的毛竹纯林(Ⅰ)、竹阔混交林(Ⅱ)和竹针混交林(Ⅲ)3种类型林分为研究对象,对其N、P、K、Ca、Mg元素分布格局及生物循环特征进行了研究。结果表明,毛竹林N、P、K、Ca、Mg5种养分元素的排列顺序为土壤层乔木层凋落物层灌木层草本层,其中土壤层(0～60cm)养分累积量占系统养分总量99%。3种林分养分元素累积量的排列顺序为ⅡⅠⅢ,分别为146196.59、144466.35和105002.59kg.hm-2,其中植被层养分累积量的排列顺序为ⅠⅡⅢ,凋落物层和土壤层养分累积量排列顺序为ⅡⅠⅢ,竹阔混交林土壤层和凋落物层养分累积量最高,立地生产潜力最大。林分Ⅰ和Ⅱ的养分利用系数显著高于林分Ⅲ,反映了林分维持高生产力需要消耗更多的养分元素;循环系数排列顺序为ⅢⅡⅠ,竹针混交林和竹阔混交林维持林木生长所需的养分元素少于毛竹纯林;毛竹纯林养分周转时间最长,竹阔混交林次之,竹针混交林最短,分别为31.89年、12.39年和12.23年,混交林周转时间显著低于毛竹纯林。竹阔混交林既有较高的生产力,又有较强的养分归还能力,是一种较好的经营方式。