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Diversity Changes During Pioneer Stages in a Subhumid Pampean Grassland Succession

Jose M. Facelli, Evelina D'Angela and Rolando J. C. Leon
The American Midland Naturalist
Vol. 117, No. 1 (Jan., 1987), pp. 17-25
DOI: 10.2307/2425703
Stable URL: http://www.jstor.org/stable/2425703
Page Count: 9
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Diversity Changes During Pioneer Stages in a Subhumid Pampean Grassland Succession
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Abstract

The hypothesis that species richness and evenness increase during early succession is tested in a postagricultural grassland succession in the Argentine Pampa. The relationship between species diversity and spatial heterogeneity of the community is also examined. Species heterogeneity (H'), evenness (J'), species richness (N'), spatial heterogeneity (Db), and relative extinction (ER) and invasion (IR) rates were calculated. Db did not increase with succession nor was it positively correlated with species diversity. Diversity increased during the 1st year and a half and decreased during the last 2 years. The initial diversity increase is attributed to high initial IR, that decreased as the species richness increased. Later in the succession, increased interference of the dominant grass, Lolium multiflorum, caused high ER and low evenness. We suggest that these changes were encouraged by the lack of disturbance. Comparison of the reported results with similar studies by other authors shows that the disturbance regime influences diversity patterns during early successional stages in herb communities.

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