The influence of environmental factors on vascular plant assemblages in created and natural vernal pools in southwestern New York (USA)

Background/Question/Methods   Vernal pools provide critical amphibian breeding habitat, support unique wetland plant assemblages within terrestrial landscapes, and may include plant species of conservation concern. In the northeastern United States, farming and development have eliminated much of the microtopographic variation required for vernal pool development and hydrologic function. In an effort to mitigate these losses, over 300 vernal pools have been constructed in southwestern New York since 2003. The vegetation within these pools had not previously been assessed, and it was unclear to what extent the plant assemblages in created pools would develop to resemble those of natural reference pools. The major objectives of our research were to 1) elucidate the influences of selected environmental factors on vascular plant species diversity, composition, and cover in natural and created pools, 2) determine the degree of similarity between natural and created pool plant assemblages, and 3) describe pool designs that facilitate the establishment of desired plants. We characterized and compared the plant assemblages and ecological condition of created pools (n=60) and natural reference pools (n=7) in southwestern New York, and used nonmetric multidimensional scaling to detect correlation of environmental factors with plant species diversity, composition, and cover. Pools ranged from 2-6 years old.

Results/Conclusions   Preliminary analyses indicated that light availability explained much of the variation in plant species composition and diversity in created pools, with pool age and area as secondary predictors. Several environmental variables appear to be correlated. Pending analyses will help identify the principal influences on vernal pool plant assemblages. Light availability was generally greater in created pools compared to natural ones, but was also more variable among created pools. On average, natural pools experienced more significant drawdown than created pools. Though created pools generally had a higher occurrence of ruderal species, at least 30 species commonly associated with natural vernal pools had colonized created pools. Differences in composition and diversity could be due in part to the young age of the pools included in this study. As created pool assemblages develop over time, species richness and the proportion of disturbance-adapted species may decrease. Future work will expand this study to include older (40+ years) constructed pools to investigate the importance of time in the development of vernal pool plant assemblages.