Species Abundance Distribution Patterns Research Articles

Species-abundance distribution patterns at different successional stages of conifer and broad-leaved mixed forest communities in Changbai Mountains, China

Aims Our objective was to explain processes that dominate species-abundance distribution pattern and mecha-nism of community assembly in temperate forests. Methods We used three 5.2-hm2 permanent plots established in secondary Populus davidiana-Betula platyphylla forest, secondary conifer and broad-leaved mixed forest and Tilia amurensis-Pinus koraiensis mixed forest in Changbai Mountains. Within each plot, we randomly selected 500 subplots within 260 m × 200 m at the scales of 10 m × 10 m, 30 m × 30 m, 60 m × 60 m and 90 m × 90 m. We calculated the mean value of species-abundance distributions taken from the 500 subplots as the observed species-abundance distribution. We estimated the fitted species-abundance distributions by neutral, log-normal, Zipf, broken stick and niche preemption models at differ-ent scales. Simulation effects were tested by Chi-square test, Kolmogorov-Smirnov (K-S) test and Akaike Infor-mation Criterion (AIC). For the neutral model, we first estimated two parameters θ and m and then simulated 600 species-abundance distributions. The average of these 600 species-abundance distributions was the best-fit result of the neutral model. We employed the 95% confidence envelopes that were approximated by the 2.5 and 97.5 percentiles of the abundances of species of rank i = 1 to S over the 600 simulations to test goodness-of-fit for the neutral model. All of the computations were conducted in R 2.14.1 with UNTB and VAGEN packages. Important findings The neutral model fit species-abundance distribution at different successional stages of conifer and broad-leaved mixed temperate forest communities. All five models fit the observed value at the 10 m × 10 m sampling scale, and the goodness of fit of the log-normal, Zipf, broken stick and niche preemption models were better than that of the neutral model. That means at small sampling scale the species-abundance distribution is dominated by neutral process and niche process; however, the niche process is much more important. At other sampling scales (30 m × 30 m, 60 m × 60 m, 90 m × 90 m), the neutral model was the best-fit model. As the sam-pling scales increased, other models gradually dropped out. At the sampling scale of 90 m × 90 m, none of the models fit well, except for the neutral model. This suggests for north temperate forests in the Changbai Mountains that the random process represented by neutral model is the main ecological process that determines the species-abundance distribution pattern at middle and large sampling scales and that the species-abundance distri-butions at different sampling scales are likely dominated by different ecological processes.

Species abundance distribution patterns of <I>Pinus tabulaeformis</I> forest in Huoshan Mountain of Shanxi Province, China

Aims Determination of species abundance distribution is important in research on species diversity. Our major objective was to determine species abundance distribution models to advance understanding of distribution mechanisms and to assist preservation of biological diversity. Methods Based on data collected from field surveys, we examined the species abundance patterns of tree, shrub and herb layers in Pinus tabulaeformis forest in Huoshan Mountain, Shanxi Province. We used niche preemption (NPM), broken stick (BSM) and overlapping niche (ONM) models and two species abundance statistical models (log-series distribution model (LSD) and log-normal distribution model (LN)) and neutral theory model (NT). The simulation effects were verified by Chi-square tests, Likelihood-ratios (L-R) tests, Kolmogorov-Smirnov (K-S) tests and Akaike Information Criterion (AIC). Important findings The best niche model for the tree layer is NPM, because it had the smallest AIC value and no significant difference (p > 0.05) between the theory predictions and observed species abundance distributions. The next best is ONM; BSM does not fit the tree layer. All three niche models are suitable for the shrub layer. ONM is the best for the herb layer, followed by BSM and NPM. LSD is good for understanding distribution mechanisms in Pinus tabulaeformis forest. LN can fit both the herb and shrub layers, but not the tree layer. NT cannot explain any layer. These findings indicate that the community has relatively few dense species and more sparse species, the species richness and diversity indices of the tree and shrub layers are much smaller than those of the herb layer, and the community evenness is relatively smaller. We conclude that one model cannot fit differ- ent data but that more than one model can fit the same data even for the same layer. Therefore, we should choose different models to study the species abundances of forest communities. We suggest that these methods might be useful for the protection of the biodiversity of forest dominated by Pinus tabulaeformis.

Distribuição temporal e espacial de anuros em área de Pampa, Santa Maria, RS

Este estudo teve como objetivo determinar a riqueza, a constância de ocorrência, os modos reprodutivos, o padrão de distribuição da abundância, a temporada de vocalização e testar a correlação das variáveis climáticas sobre a atividade de vocalização dos anuros em uma região do Bioma Pampa, Santa Maria, Rio Grande do Sul. Durante o período de novembro de 2001 a outubro de 2002 foram realizadas coletas mensais empregando o método de ‘busca em sítio de reprodução’ e exame de exemplares depositados na Coleção Herpetológica do Setor de Zoologia da Universidade Federal de Santa Maria (ZUFSM). Foi registrada a ocorrência de 25 espécies de anuros. A anurofauna registrada corresponde a 30% das espécies encontradas no Rio Grande do Sul e normalmente está associada a áreas abertas encontradas no estado e em países vizinhos. Foram registrados quatro modos reprodutivos: modo 1 (14 espécies; 58,3%); modos 11 e 30 (nove espécies; 37,5%) e modo 24 (uma espécie; 4,2%). A baixa diversificação de modos reprodutivos provavelmente está relacionada à homogeneidade do hábitat primariamente campestre. A maior parte das espécies mostrou-se constante ou acessória na área estudada e o padrão de distribuição da abundância das espécies apresentou ajuste aos modelos Broken Stick e Log-normal, caracterizados pela homogeneidade na distribuição da abundância das espécies. A maioria das espécies apresentou grande plasticidade na ocupação de hábitats, mas poucas foram plásticas no uso dos sítios de vocalização. Houve correlação positiva, ainda que fraca, da riqueza de espécies com a precipitação mensal acumulada e da abundância com a temperatura média máxima. As correlações obtidas indicaram que na área estudada a temperatura parece atuar mais sobre a abundância de machos em atividade de vocalização e a precipitação sobre a riqueza, apesar da riqueza de espécies ser significativamente maior durante o período mais quente do ano. Estes resultados revelaram que as variáveis climatológicas testadas explicaram muito pouco da ocorrência sazonal das espécies, assim a influência de outras variáveis ambientais merece ser testada em estudos futuros.

Species abundance distribution patterns of microarthropods in surface decomposing leaf-litter and mineral soil on a desert watershed

Species abundance distribution patterns of microarthropods in surface decomposing leaf-litter and mineral soil on a desert watershed