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Habitat-specific demography across dune fixation stages in a semi-arid sandland: understanding the expansion, stabilization and decline of a dominant shrub

作　　者：Shou-Li Li、Fei-Hai Yu、Marinus J. A. Werger、Ming Dong*、Pieter A. Zuidema
影响因子：5.260
刊物名称：Journal of Ecology
出版年份：2011
卷：99  期：2  页码：610-620

论文摘要：

 1. Maintaining viable populations in different habitats requires physiological, morphological and demographic adaptations of plants. In sandland environments, plants experience substantial variation in growing conditions during the dune fixation process, with high sand mobility in early stages and denser vegetation cover in later stages.
2. We studied the changes in demography of a dominant shrub, Artemisia ordosica, at three stages of dune fixation: semi-fixed dunes, fixed dunes and fixed dunes covered with microbiotic crust. Demographic data fromthree annual censuses were used to parameterize integral projection models (IPMs) to conduct comparative demographic analyses.
3. Plant growth and reproduction decreased strongly as dunes became more fixed. Shrinkage in plant height occurred very frequently, particularly in the fixed dunes with microbiotic crust. Population growth rate (k) declined substantially with dune fixation: from rapid expansion in semi-fixed dunes (k = 1.35–1.09) to moderate decline in fixed dunes with microbiotic crust (k = 0.94–0.89).
4. Elasticity analysis revealed that survival was a key vital rate for population growth in all habitats. Growth and fecundity were of higher importance in the semi-fixed habitat than in the other two habitats where shrinkage became an important factor determining k. Seedlings and small plants were critical for population growth in semi-fixed dunes, whereas moderate to large-sized plants were most important in the other habitats.
5. Results of life table response experiments showed that the observed strong decrease in k during dune fixation was mainly caused by reduction in fecundity, but with additional and considerable contributions fromreduced plant growth and increased occurrence of shrinkage. Thus, populations in semi-fixed dunes are able to expand rapidly due to a much higher fecundity compared to those in other habitats.
6. Synthesis. Artemisia ordosica adopts different life history strategies along the dune fixation process. Fast expansion in semi-fixed dunes is enabled by high seed production and effective recruitment, while populations at later dune fixation stages are maintained through frequent plant shrinkage. Integral projection models are highly appropriate tools for analysing such life history changes as they are based on statistical comparisons of vital rates across habitats.
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