Abstract
Variation in species composition between two communities is so-called β diversity, or dissimilarity, and can be separated into two components: turnover and nestedness. However, the mechanisms underlying these two components remain ambiguous, particularly for different lifeforms. In this study, we examined the altitudinal gradient of biodiversity in the Baotianman Nature Reserve of the eastern Qinling Mountains in central China and found that turnover is the predominant process accounting for β diversity, that dispersal limitation is the main factor influencing species diversity, and that its effect on trees is greater than on shrubs, with herbs least affected. Nestedness, in contrast, is less prominent and generally affected by the richness deviation between communities, and the impact of richness deviation is stronger on shrubs than on trees, and in turn, stronger than on herbs. We zoned the altitudinal vegetation communities by pairwise dissimilarity index, and found that the peak value of turnover rather than β diversity indicates the existence of transitional zones; the higher the turnover index, the greater the diversity between communities. Comparatively, nestedness indicates species overlap between communities. The highest nestedness index usually occurs in the interior of vegetation zones. The result of community clustering by pairwise dissimilarity shows that understory species could have been mostly replaced upwards, while the dominant tree species may keep stable, indicating that dispersal limitation works differently for different lifeforms.
Highlights
One of the top issues in community ecology is the altitudinal gradient of mountain biodiversity, which is usually measured by three indicators: α, β, and γ diversity [1]. α and γ diversity indices measure species diversity for local sites and a regional species pool, respectively. β diversity describes species variance among sites [2], and numerous methods have been introduced to measure it, among which the multiplicative [1,3] and additive [4,5] approaches derived from α and γ diversity are widely used
We examined the altitudinal species richness patterns of different lifeforms in the Baotianman Nature Reserve and found that the species richness of all lifeforms humped at the middle elevation with the herb maximum richness at a higher elevation
We zoned the altitudinal vegetation gradient into five sub-belts and compared the results by traditional zonation method and the hierarchical clustering method based on dissimilarity
Summary
One of the top issues in community ecology is the altitudinal gradient of mountain biodiversity, which is usually measured by three indicators: α, β, and γ diversity [1]. α and γ diversity indices measure species diversity for local sites and a regional species pool, respectively. β diversity (dissimilarity) describes species variance among sites [2], and numerous methods have been introduced to measure it, among which the multiplicative [1,3] and additive [4,5] approaches derived from α and γ diversity are widely used. One of the top issues in community ecology is the altitudinal gradient of mountain biodiversity, which is usually measured by three indicators: α, β, and γ diversity [1]. Β diversity (dissimilarity) describes species variance among sites [2], and numerous methods have been introduced to measure it, among which the multiplicative [1,3] and additive [4,5] approaches derived from α and γ diversity are widely used. Pairwise measure dissimilarity is an intuitive way to assess the variance of species among communities; this method has become prevalent in recent years [6,7,8]. Pairwise dissimilarity has been seldom studied between adjacent sites along an altitudinal gradient [13]. Yang et al [13]
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