Abstract:
In-depth exploration of the species abundance distribution (SAD) pattern of plant
communities under different terrains in the subtropical karst area can reveal the mechanism of
formation of the SAD of the community under different terrains, thereby enriching the theory of
plant community construction in this area. In this paper, the arbor layer and shrub layer of plant
communities under four typical landforms of ridge, trough, saddle and depression in Maolan karst
area of Guizhou Province were used as the objects. The empirical cumulative distribution
function(ECDF) was used to characterize the SAD, at the same time, the Wilcoxon rank sum test was
used to analyze the differences in species abundance between different terrains. Then different ecological models were used for fitting, and Kolmogorov-Smirnov (K-S) test and Akaike
Information Criterion (AIC) were used to detect model acceptance and goodness of fit. The results
were as follows: (1) There were differences in the number of individuals and species in plant
communities under different terranes, the number of individuals in saddles was the most, the number
of species in depressions was the most, and the number of individuals and species in ridges was the
least. (2) There were significant differences among shrub layers, between ridge and saddle, between
ridge and depression, between saddle and trough valley, and between saddle and depression, while
there were no significant differences in the SAD of arbor layers in plant communities under different
terrains. (3) The SAD of the arbor layer under different terrains was well accepted by the neutral
model. The ridge fits best, but all terrains were poorly accepted by ecological models, only the ridge
and saddle passed through the two niche models, and the goodness of fit was not as good as that of
the neutral model. The shrub layer was also well accepted by the neutral model with the best fit of
the saddle, but it was poorly accepted by the niche model, and only the depression passed the broken
stick model. Overall, the arbor layer was more acceptable to the two ecological models than the
shrub layer, probably because the SAD of the arbor layer had more obvious imprints of ecological
processes. However, the difference in the goodness of fit of the shrub layer under different terrains is
greater, which may be related to the more drastic changes of the shrub layer species to the
environment. Consequently, different terrains lead to different ecological processes of community
construction, and the SAD pattern gradually adapts to the terrain.
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