||Few studies have directly addressed the effects of disturbance on spatial and temporal heterogeneity. Spatial heterogeneity is the degree of dissimilarity in species composition from one point to another in a community, whereas temporal heterogeneity is compositional change within a site over time. The purposes of this study were to determine (1) if a quadratic relationship exists between within-site heterogeneity and disturbance frequency as predicted by the intermediate disturbance hypothesis (IDH), (2) if disturbed and undisturbed sites have similar heterogeneity as implied by the disturbance heterogeneity
hypothesis (DHM), and whether or not these results differed with scale, and (3) if there is
a relationship between spatial and temporal heterogeneity as implied by the DHM. Analyses
were based on plant species composition data collected over 9 yr in quadrats permanently
located in experimental management units subjected to different burning frequencies at
Konza Prairie Research Natural Area, Kansas, USA.
The relationship between disturbance frequency and within-site heterogeneity was opposite that predicted by the IDH. Heterogeneity was lowest at intermediate disturbance frequencies. Heterogeneity in annually burned prairie was lower than in unburned prairie and prairies burned once every 4 yr in contrast to predictions of the DHM. However, this relationship did not hold at larger spatial scales. There was a positive relationship between within-site spatial and temporal heterogeneity on annually burned sites, sites burned once
every 4 yr, and nearly so on sites burned every other year. Within-site heterogeneity was negatively correlated with cover of Andropogon gerardii, and positively correlated with total richness and species diversity. Studies of variation, in addition to averages, will increase our ability to predict patterns of species distribution and abundance within and between communities in response to disturbance.