Phylogenetic structure of angiosperm communities during tropical forest succession

The phylogenetic structure of ecological communities can shed light on assembly processes, but the focus of phylogenetic structure research thus far has been on mature ecosystems. Here, I present the first investigation of phylogenetic community structure during succession. In a replicated chronosequence of 30 sites in northeastern Costa Rica, I found strong phylogenetic overdispersion at multiple scales: species present at local sites were a non-random assemblage, more distantly related than chance would predict. Phylogenetic overdispersion was evident when comparing the species present at each site with the regional species pool, the species pool found in each age category to the regional pool or the species present at each site to the pool of species found in sites of that age category. Comparing stem size classes within each age category, I found that during early succession, phylogenetic overdispersion is strongest in small stems. Overdispersion strengthens and spreads into larger size classes as succession proceeds, corroborating an existing model of forest succession. This study is the first evidence that succession leaves a distinct signature in the phylogenetic structure of communities.     

Change in community phylogenetic structure during tropical forest succession: evidence from New Guinea

Ecologists have recently interpreted patterns of phylogenetic distance among coexisting species as indicative of processes affecting community assembly during forest succession. We investigated plant community phylogenetic structure along a successional gradient in New Guinean lowland rain forest. We surveyed all trees with diameter at breast height ≥ 5 cm in nineteen 0.25 ha plots representing younger secondary, older secondary, and primary forest. We estimated plant community phylogeny from rbcL gene sequences to quantify change in phylogenetic structure during succession. Mean phylogenetic distance among co‐occurring trees increased with total basal area per plot, a proxy for forest age. Significant phylogenetic clustering was detected in secondary forest whereas primary forest was significantly over‐dispersed relative to null expectations. We examined the sensitivity of these patterns to various methods of branch length estimation and phylogenetic uncertainty. Power to detect community phylogenetic patterns when equal branch lengths were assumed was weak in comparison to direct molecular and time‐calibrated measures of divergence. Inferred change during forest succession was also robust to phylogenetic uncertainty so long as temporal information was incorporated in estimates of divergence. The observed patterns are consistent with processes of environmental filtering during tropical forest succession giving way to other processes in primary forests including density‐dependence.     

Evidence for community assembly constraints during succession in dune slack plant communities

Community assembly during succession can be constrained by both local and regional factors. Despite an increasing regional species pool size during succession, we found a limit on the number of species in 1 × 1 m plots in dune slacks. Three alternative hypotheses (habitat heterogeneity, dispersal limitation and niche limitation) explaining this community saturation were tested. A null model analysis showed that species richness in the plots had an unusually low variance suggesting that beta habitat diversity was not likely to explain the limitation on species richness. Because we did not find a correlation between the distribution of species over the slack and their dispersal capacity, we also excluded the dispersal limitation hypothesis. Finally, a guild proportionality analysis revealed that the abundances of forb, graminoid and ruderal species showed low an unusually low variance over all age classes involved. This provides evidence for nonrandom community assembly during succession, likely to be determined by competitive exclusion among species of the same guild.     

Soil food web components affect plant community structure during early succession

There is a growing awareness among ecologists of the strong links that exist between above- and belowground food webs. So far, the majority of studies have considered these links from the microbial point of view, usually with single plants or very simple plant communities. Here, we report the interactions between two components of the soil food web, root-feeding insects and arbuscular mycorrhizal (AM) fungi, and their effects on the structure and development of early successional plant communities. We use long-term field experiments that employ manipulations of these organisms, both singly and in combination. Both groups have strong effects on plant community structure, with root-feeding insects increasing and AM fungi decreasing plant species richness. Root-feeding insects appear to accelerate the process of early succession, while AM fungi retard it. There are strong interactions between the insects and fungi. The effect of insects is greatest when AM fungi are present. It is suggested that this is a consequence of plant physiology, rather than any direct interaction between the groups involved. Meanwhile, AM fungi have their greatest effect on plant communities when insects are absent, suggesting that there is some disruption of the symbiosis by the invertebrates. In developing plant communities, the rate and direction of the succession is therefore determined by the relative abundance of these two members of the soil food web. The next challenge will be to understand the roles of other members of the subterranean web in terms of their interactions with insects and AM fungi and effects on plant community development.     

Benthic invertebrate community structure is influenced by forest succession after clearcut logging in southeastern Alaska

To assess the effects of timber harvesting on headwater streams in upland forests, benthic community structure was contrasted among four dominant forest management types (old growth, red alder-dominated young growth, conifer-dominated young growth, clearcut) and instream habitats (woody debris, cobble, gravel) in southeastern Alaska. Benthos in streams of previously harvested areas resulted in increased richness, densities and biomass relative to old growth types, particularly in young growth stands with a red alder-dominated riparian canopy. Woody debris and gravel habitats supported a combination of higher densities and biomass of invertebrates than cobble habitats. In addition, woody debris also supported a richer and more diverse invertebrate fauna than either cobble or gravel substrates. Maintaining both a woody debris source and a red alder component in regenerating riparian forests following timber harvesting should support greater invertebrate densities and diversity following clearcutting.     

Functional diversity changes during tropical forest succession

Functional diversity (FD) ‘those components of biodiversity that influence how an ecosystem operates or functions’ is a promising tool to assess the effect of biodiversity loss on ecosystem functioning. FD has received ample theoretical attention, but empirical studies are limited. We evaluate changes in species richness and FD during tropical secondary forest succession after shifting cultivation in Mexico. We also test whether species richness is a good predictor of FD. FD was calculated based on a combination of nine functional traits, and based on two individual traits important for primary production (specific leaf area) and carbon sequestration (wood density). Stand basal area was a good predictor of successional changes in diversity and FD, in contrast to fallow age. Incidence-based FD indices increased logarithmically with stand basal area, but FD weighted by species’ importance values lacked pattern with succession. Species richness and diversity are strong predictors of FD when all traits were considered; linear relationships indicate that all species are equally functionally complementary, suggesting there is little functional redundancy. In contrast, when FD was calculated for individual traits and weighted for abundances, species richness may underestimate FD.Selection of functional trait(s) critically determines FD, with large consequences for studies relating biodiversity to ecosystem functioning. Careful consideration of the traits required to capture the ecosystem process of interest is thus essential.     

Leaf-nutrient accumulation and turnover at three stages of succession from heathland to forest

Abstract. Accumulation of nutrients in leaves of the dominating species of three ecosystems, characterizing the secondary succession from Genisto-Callunetum heathland through Leucobryo-Pinetum birch-pine woodland to mature Querco-Fagetum oak-beech forest, as well as nutrient turnover within these ecosystems was studied. The objective of the study was to establish potential variations in quantity and quality of nutrient supply to the plants with respect to succession dynamics. The results show very low leaf nutrient concentrations of all species investigated, coinciding with low nutrient availability in the soil. However, the nutrient content of leaves and leaf litter of Quercus petraea and Fagus sylvatica, which dominate the late succession stages, and in Betulapéndula are higher than in the photosynthetic organs (leaves and young shoots) of Calluna vulgaris and Pinus sylvestris. The combination of the higher nutrient content of the leaves and an increasing leaf-litter production during succession results in an increased nutrient turnover via leaf-litter fall. However, due to the high leaf biomass, the storage of nutrients in the leaf biomass is highest within the birch-pine woodland. From this, it may be assumed that the low demand and the low loss of nutrients via leaf-litter fall are favourable for Pinus at the early stages of forest succession on poor sandy soils. In contrast, Quercus and Fagus are provided with better growth conditions at the later stages of succession resulting from the accumulation of plant-available nutrients in the ecosystem by Pinus sylvestris, combined with a higher nutrient turnover as compared with the heathland.     

AOB community structure and richness under European beech, sessile oak, Norway spruce and Douglas-fir at three temperate forest sites

Background and aims

The relations between tree species, microbial diversity and activity can alter ecosystem functioning. We investigated ammonia oxidizing bacteria (AOB) community structure and richness, microbial/environmental factors related to AOB diversity and the relationship between AOB diversity and the nitrification process under several tree species.

Methods

Forest floor (Of, Oh) was sampled under European beech, sessile oak, Norway spruce and Douglas-fir at three sites. AOB community structure was assessed by PCR-DGGE and sequencing. Samples were analyzed for net N mineralization, potential nitrification, basal respiration, microbial biomass, microbial or metabolic quotient, pH, total nitrogen, extractable ammonium, organic matter content and exchangeable cations.

Results

AOB community structure and tree species effect on AOB diversity were site-specific. AOB richness was not related to nitrification. Factors regulating ammonium availability, i.e. net N mineralization or microbial biomass, were related to AOB community structure.

Conclusion

Our research shows that, at larger spatial scales, site specific characteristics may be more important than the nature of tree species in determining AOB diversity (richness and community structure). Within sites, tree species influence AOB diversity. The absence of a relation between AOB richness and nitrification points to a possibly role of AOB abundance, phenotypic plasticity or the implication of ammonia oxidizing archaea.     

长白山温带森林不同演替阶段土壤化学性质及微生物群落结构的变化

土壤微生物是生态系统物质循环和能量流动的驱动者,其群落结构可以用来表征土壤生态过程及其对地上植被变化的响应机制。本研究采用时空替代法在长白山地区选取了阔叶红松林演替序列的5个不同阶段:杨桦幼龄林、杨桦中龄林、杨桦成熟林、阔叶红松成熟林和阔叶红松过熟林,采用磷脂脂肪酸法(PLFA)测定了土壤微生物群落组成和结构,分析了其随地上植被演替过程的变化,同时比较了不同演替阶段土壤化学性质差异。结果表明:随着演替的正向进行,土壤总有机碳、全碳、全氮、全磷含量显著提高,碳氮比逐渐下降。土壤微生物生物量、群落结构及组成发生明显变化:土壤微生物总PLFAs、细菌PLFAs、革兰氏阳性菌PLFAs、革兰氏阴性菌PLFAs含量显著增加;真菌PLFAs(18:2ω6c)先增加后减少,中期阶段的杨桦成熟林土壤真菌PLFA含量最高,同时细菌/真菌最小;革兰氏阳性菌/革兰氏阴性菌(G+/G-)随着演替的进行逐渐增大。土壤微生物生物量与土壤全碳、总有机碳、全氮、全磷含量呈显著正相关,与碳氮比呈显著负相关;冗余分析(RDA)结果显示,全碳、总有机碳、全氮和碳氮比是影响土壤微生物群落结构的主要因素。本研究表明,随着植被演替的正向进行,土壤质量逐渐提高;土壤微生物群落组成明显改变;土壤微生物群落结构与土壤理化性质显著相关。     

Comparative physiology and demography of three Neotropical forest shrubs: alternative shade-adaptive character syndromes

A suite of functionally-related characters and demography of three species of Neotropical shadeadapted understory shrubs (Psychotria, Rubiaceae) were studied in the field over five years. Plants were growing in large-scale irrigated and control treatments in gaps and shade in old-growth moist forest at Barro Colorado Island, Panama. Irrigation demonstrated that dry-season drought limited stomatal conductance, light saturated photosynthesis, and leaf longevity in all three species. Drought increased mortality of P. furcata. In contrast, irrigation did not affect measures of photosynthetic capacity determined with an oxygen electrode or from photosynthesis-CO₂ response curves in the field. Drought stress limited field photosynthesis and leaf and plant survivorship without affecting photosynthetic capacity during late dry season. Leaves grown in high light in naturally occurring treefall gaps had higher photosynthetic capacity, dark respiration and mass per unit area than leaves grown in the shaded understory. P. furcata had the lowest acclimation to high light for all of these characters, and plant mortality was greater in gaps than in shaded understory for this species. The higher photosynthetic capacity of gap-grown leaves was also apparent when photosynthetic capacity was calculated on a leaf mass basis. Acclimation to high light involved repackaging (higher mass per unit leaf area) as well as higher photosynthetic capacity per unit leaf mass in these species. The three species showed two distinct syndromes of functionally-related adaptations to low light. P. limonensis and P. marginata had high leaf longevity (3 years), high plant survivorship, low leaf nitrogen content, and high leaf mass per unit area. In contrast, P. furcata had low leaf survivorship (1 year), high plant mortality (77–96% in 39 months), low leaf mass per unit area, high leaf nitrogen content, and the highest leaf area to total plant mass; the lowest levels of shelf shading, dark respiration and light compensation; and the highest stem diameter growth rates. This suite of characters may permit higher whole-plant carbon gain and high leaf and population turnover in P. furcata. Growth in deep shade can be accomplished through alternative character syndromes, and leaf longevity may not be correlated with photosynthetic capacity in shade adapted plants.     

Changes in the community structure of ammonia-oxidizing bacteria during secondary succession of calcareous grasslands

The community structure of β-subclass Proteobacteria ammonia-oxidizing bacteria was determined in semi-natural chalk grassland soils at different stages of secondary succession. Both culture-mediated (most probable number; MPN) and direct nucleic acid-based approaches targeting genes encoding 16S rRNA and the AmoA subunit of ammonia monooxygenase were used. Similar shifts were detected in the composition of the ammonia oxidizer communities by both culture-dependent and independent approaches. A predominance of Nitrosospira sequence cluster 3 in early successional fields was replaced by Nitrosospira sequence cluster 4 in late successional fields. The rate of this shift differed between the two areas examined. This shift occurred in a background of relative stability in the dominant bacterial populations in the soil, as determined by domain-level polymerase chain reaction–denaturing gradient gel electrophoresis (PCR–DGGE). Molecular analysis of enrichment cultures obtained using different ammonia concentrations revealed biases towards Nitrosospira sequence cluster 3 or Nitrosospira sequence cluster 4 under high- or low-ammonia conditions respectively. High-ammonia MPNs suggested a decease in ammonia oxidizer numbers with succession, but low-ammonia MPNs and competitive PCR targeting amoA failed to support such a trend. Ammonia turnover rate, not specific changes in plant diversity and species composition, is implicated as the major determinant of ammonia oxidizer community structure in successional chalk grassland soils.     

Ectomycorrhizal fungal diversity and community structure on three co-occurring leguminous canopy tree species in a Neotropical rainforest

? The ectomycorrhizal (ECM) symbiosis was historically considered restricted to the temperate zones, but recent studies have shown the importance of this symbiosis across the tropics. We examined ECM fungal diversity, host plant phylogeny and ECM host preferences in a rainforest dominated by the leguminous host plants Dicymbe corymbosa, Dicymbe altsonii and Aldina insignis. ? Ectomycorrhizal fungi were identified by internal transcribed spacer rDNA sequencing and host species were verified with chloroplast trnL sequencing. To test whether Dicymbe and Aldina represent independent gains of the ECM symbiosis, we constructed a Fabaceae phylogeny using MatK and trnL. We identified four independent ECM lineages within the Fabaceae. ? We detected a diverse community of 118 ECM species dominated by the /clavulina, /russula-lactarius, /boletus, and /tomentella-thelephora lineages. Ectomycorrhizal species in Agaricales, Atheliales and Polyporales may represent previously unrecognized tropical-endemic ECM lineages. Previous studies suggested that ECM fungi did not diversify in the tropics, but the /clavulina lineage appears to have a center of diversity in tropical South America. ? Dicymbe and Aldina represent independent gains of the ECM symbiosis in Fabaceae but their fungal symbionts showed no host preferences. Spatial factors are more important than hosts in structuring the ECM fungal community in this ecosystem.     

Species richness and structure of three Neotropical bat assemblages

We compared the assemblages of phyllostomid bats in three Neotropical rainforests with respect to species richness and assemblage structure and suggested a method to validate estimates of species richness for Neotropical bat assemblages based on mist-netting data. The fully inventoried bat assemblage at La Selva Biological Station (LS, 100 m elevation) in Costa Rica was used as a reference site to evaluate seven estimators of species richness. The Jackknife 2 method agreed best with the known bat species richness and thus was used to extrapolate species richness for an Amazonian bat assemblage (Tiputini Biodiversity Station; TBS, 200 m elevation) and an Andean premontane bat assemblage (Podocarpus National Park; BOM, 1000 m elevation) in Ecuador. Our results suggest that more than 100 bat species occur sympatrically at TBS and about 50 bat species coexist at BOM. TBS harbours one of the most species-rich bat assemblages known, including a highly diverse phyllostomid assemblage. Furthermore, we related assemblage structure to large-scale geographical patterns in floral diversity obtained from botanical literature. Assemblage structure of these three phyllostomid assemblages was influenced by differences in floral diversity at the three sites. At the Andean site, where understorey shrubs and epiphytes exhibit the highest diversity, the phyllostomid assemblage is mainly composed of understorey frugivores and nectarivorous species. By contrast, canopy frugivores are most abundant at the Amazonian site, coinciding with the high abundance of canopy fruiting trees. Assemblage patterns of other taxonomic groups also may reflect the geographical distribution patterns of floral elements in the Andean and Amazonian regions.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 617–629.     

淀山湖浮游植物群落特征及其演替规律

为探明淀山湖浮游植物群落结构演变与富营养化之间的关系,于2004-2006年对上海市最大天然淡水湖泊淀山湖的浮游植物进行逐月采样调查,分析其群落结构特征.共采集到淀山湖浮游植物84属205种,主要由绿藻(种类数占50%)、硅藻(20%)、蓝藻(13%)、裸藻(13%)等组成.相邻两月之间种类相似性系数呈现冬春季高、夏秋季低的趋势:优势种为银灰平裂藻(Merismopedia glauca)、小席藻(Phormidium tenus)、铜绿微囊藻(Microcystis aeruginosa)、具缘微囊藻(M.marginata)、湖泊鞘丝藻(Lyngbya limnetica)、微小色球藻(Chroococcus minutus),颗粒直链藻最窄变种(Melosira granulata var.angustissima )、啮蚀隐藻(Cryptomonas erosa)、小球藻(Chlorella vulgate)和四尾栅藻(Scenedesmus quadricauda)等.浮游植物群落细胞数量主要由蓝藻(42.73%)、绿藻(37.75%)、硅藻(12.67%)和隐藻(6.06%)组成;生物量主要由硅藻(36.75%)、蓝藻(16.78%)、绿藻(16.36%)和隐藻03.53%)等组成.淀山湖浮游植物群落结构季节演替模式不同于PEG(Plankton Ecology Group)模型,其中蓝藻从春末开始大量出现,夏季大量繁殖,一直延续到秋初.综合文献资料看出,淀山湖浮游植物群落已从1959年的硅藻一金藻型、1987-1988年的隐藻-硅藻型演变为2004-2006年的蓝藻-绿藻型;数量由1959年的103 ind./L上升至2004-2006年的1.11×107 cells/L.演替的总体趋势表现为:贫中营养型的金藻、甲藻比例下降,富营养型的蓝藻、隐藻和微型绿藻增加.浮游植物数量和群落结构的演变指示了淀山湖水体的富营养化进程.     

Phylogenetic and functional dissimilarity does not increase during temporal heathland succession

Succession has been a focal point of ecological research for over a century, but thus far has been poorly explored through the lens of modern phylogenetic and trait-based approaches to community assembly. The vast majority of studies conducted to date have comprised static analyses where communities are observed at a single snapshot in time. Long-term datasets present a vantage point to compare established and emerging theoretical predictions on the phylogenetic and functional trajectory of communities through succession. We investigated within, and between, community measures of phylogenetic and functional diversity in a fire-prone heathland along a 21 year time series. Contrary to widely held expectations that increased competition through succession should inhibit the coexistence of species with high niche overlap, plots became more phylogenetically and functionally clustered with time since fire. There were significant directional shifts in individual traits through time indicating deterministic successional processes associated with changing abiotic and/or biotic conditions. However, relative to the observed temporal rate of taxonomic turnover, both phylogenetic and functional turnover were comparatively low, suggesting a degree of functional redundancy among close relatives. These results contribute to an emerging body of evidence indicating that limits to the similarity of coexisting species are rarely observed at fine spatial scales.     

群落结构和叶面积指数在具茨山植被次生演替中的变化

采取3S(GIS,RS和GPS)技术和野外作业相结合的方法,研究了河南省具茨山人为干扰后植被次生演替过程。在此基础上,从宏观和微观尺度对不同演替阶段典型群落的结构变化和植被叶面积指数(LAI)动态进行分析。结果表明:乔木阶段的植被LAI均值为4.1～5.5;灌木阶段为3.0～3.7;草本阶段为1.0～1.5。部分灌木林在生长季的LAI和盖度高于乔木林。随着演替进行,群落结构也发生很大变化,乔木种类和数量逐步上升。植被系统的复杂度和稳定性不断增强,其发挥的生态功能和生态服务价值随之提高。     

Correspondence between community structure and function during succession in phenol- and phenol-plus-trichloroethene-fed sequencing batch reactors

The effects of more than 2 years of trichloroethene (TCE) application on community succession and function were studied in two aerobic sequencing batch reactors. One reactor was fed phenol, and the second reactor was fed both phenol and TCE in sequence twice per day. After initiation of TCE loading in the second reactor, the TCE transformation rates initially decreased, but they stabilized with an average second-order rate coefficient of 0.044 liter mg(-1) day(-1) for 2 years. In contrast, the phenol-fed reactor showed higher and unstable TCE transformation rates, with an average rate coefficient of 0.093 liter mg(-1) day(-1). Community analysis by terminal restriction fragment length polymorphism (T-RFLP) analysis of the 16S rRNA genes showed that the phenol-plus-TCE-fed reactor had marked changes in community structure during the first 100 days and remained relatively stable afterwards, corresponding to the period of stable function. In contrast, the community structure of the phenol-fed reactor changed periodically, and the changes coincided with the periodicity observed in the TCE transformation rates. Correspondence analysis of each reactor community showed that different community structures corresponded with function (TCE degradation rate). Furthermore, the phenol hydroxylase genotypes, as determined by restriction fragment length polymorphism analysis, corresponded to community structure patterns identified by T-RFLP analysis and to periods when the TCE transformation rates were high. Long-term TCE stress appeared to select for a different and stable community structure, with lower but stable TCE degradation rates. In contrast, the community under no stress exhibited a dynamic structure and dynamic function.     

Small-scale spatial variability in phylogenetic community structure during early plant succession depends on soil properties

During early plant succession, the phylogenetic structure of a community changes in response to important environmental filters and emerging species interactions. We traced the development of temperate-zone plant communities during the first 7 years of primary succession on catchment soils to explore patterns of initial species assembly. We found pronounced small-scale differences in the phylogenetic composition of neighbouring plant assemblages and a large-scale trend towards phylogenetic evenness. This small-scale variability appears to be mediated by soil properties, particularly carbonate content. Therefore, abiotic environmental conditions might counteract or even supersede the effects of interspecific competition among closely related species, which are usually predicted to exhibit patterns of phylogenetic evenness. We conclude that theories on phylogenetic community composition need to incorporate effects of small-scale variability of environmental factors.     

Temporal patterns in rates of community change during succession

While ecological dogma holds that rates of community change decrease over the course of succession, this idea has yet to be tested systematically across a wide variety of successional sequences. Here, I review and define several measures of community change rates for species presence-absence data and test for temporal patterns therein using data acquired from 16 studies comprising 62 successional sequences. Community types include plant secondary and primary succession as well as succession of arthropods on defaunated mangrove islands and carcasses. Rates of species gain generally decline through time, whereas rates of species loss display no systematic temporal trends. As a result, percent community turnover generally declines while species richness increases--both in a decelerating manner. Although communities with relatively minor abiotic and dispersal limitations (e.g., plant secondary successional communities) exhibit rapidly declining rates of change, limitations arising from harsh abiotic conditions or spatial isolation of the community appear to substantially alter temporal patterns in rates of successional change.