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Yuan C.,Key Laboratory for Conservation of the Rare | Yuan C.,Yunnan Academy of Forestry | Meng G.,Yunnan Academy of Forestry | Fang X.,Yunnan Academy of Forestry | And 5 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2012

Understanding the population's change patterns in time and space of endangered species is essential for decision-making to conservation of the rare and endangered species. However, most populations of these species are small, and it is difficult to use traditional quadrat sampling techniques for demographic analysis. Alcimandra cathcartii, a rare and endangered plant, is one of the first-class nationally protected species in China, but little is known about the population ecology of this species because of the limitations of research scale and analytic methods. The objective of this present study is to examine: 1) the age structure of A. cathcartii population; 2) spatial distribution pattern and its change with spatial scale; and 3) the spatial distribution pattern and spatial relationship at different spatial scales and growth stages. The Ripley's L-function was used to analyze the spatial pattern and spatial association of different development stages, based on the investigation data from 4-hm2 plot in a primary middle-mountain moist evergreen broad-leaved forest in Gaoligong Mountain, Yunnan. The 4-hm2 plot was divided into 100 quadrats, and all stems of A. cathcartii with diameter at breast height (DBH) ≥1 cm were measured, tagged, and mapped. All individuals of this species were divided into three growth stages according to its DBH sizes: small trees, 1 cm≤DBH<7. 5 cm; medium trees, 7. 5 cm≤DBH<22. 5 cm; and large trees, DBH≥22. 5 cm. The results showed that the number of small individuals of A. cathcartii was the highest in three growth stages. The age structure of the species was inverted "J" shape curve, and the population is currently in rising stage and is stable. The distribution pattern of this population is closely related to the spatial scale, with an aggregation distribution in less than 75 m and a random distribution in ≥75 m spatial scale. The habitat heterogeneity may play an important role in the formation of the spatial distribution of the population. There were obvious differences in spatial distribution patterns among different growth stages of the population. The smaller individuals showed aggregation distribution at smaller spatial scale, while larger trees were random distribution type at all spatial scales (0-100m). The spatial relationships among different development stages are negative correlation at smaller scale, while it tends to be no association at larger scale. This indicates that there may be different mechanism on the formation of distributions at different spatial scales and growth stages. Based on the analysis, it was suggested that the age structure and spatial distribution pattern of A. cathcartii population were determined by the combined impact of the species bioecological properties, intra-and inter-specific interactions, and environmental factors. The results of this study implicates that it is important for conservation of small populations of A. cathcartii to strengthen protection of the forest ecosystem and habitats with these rare and endangered species. Source

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