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CONTROL OF VEGETATION ON CONTRASTING SUBSTRATES: HERB PATTERNS ON SERPENTINE AND SANDSTONE
Author(s) -
Moral Roger del
Publication year - 1982
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1982.tb13252.x
Subject(s) - transect , principal component analysis , moisture , quadrat , vegetation (pathology) , detrended correspondence analysis , ordination , ecology , biology , habitat , environmental science , geography , mathematics , statistics , medicine , pathology , meteorology
Binary discriminant analysis (BDA) reveals relationships between species distributions and environmental variables. In this study, BDA was applied to transects on serpentine and sandstone in the Wenatchee Mountains, Washington. Species presence and states of ten habitat variables were recorded in each quadrat. Species response patterns significantly different from a random expectation suggested that distributions are controlled by soil moisture far more strongly on serpentine than they are on sandstone, where light and its correlates are more important. Environmental patterns were explored with direct principal components analysis (PCA) of standardized environmental variables and indirectly by PCA of the significant D‐values. The latter is biased towards variables to which species respond strongly. The results emphasize the environmental and floristic contrasts between substrates. On serpentine, direct PCA indicates that effective moisture, soil fertility, and insolation control the first three axes, while on sandstone, insolation, fertility, and effective moisture control the first three axes, respectively. The PCA of D‐values (Q‐mode) is similarly interpreted: moisture is strongly correlated with the first component on the serpentine transect, while insolation and fertility are correlated with the first component on sandstone. Species ordinations also result from Q‐mode analysis. They reflect species responses to the identified gradients and indicate mutual species‐environment interactions. These analyses conform to the hypothesis that mineral conditions of serpentine select against intolerant species and that survivors respond primarily to moisture conditions that are a result of low productivity, attributable to adverse nutrient conditions. On sandstone, the moisture gradient is less pronounced, and direct canopy effects that create variable light conditions predominate. BDA is a useful tool in ecological survey and pattern analysis. Species responses to environmental factors may be estimated quickly and directly. This method will help to focus subsequent research, improve experimental design, and generate explicit and testable hypotheses about species‐habitat interactions.