What limits the occupancy of rare plant species in restored habitats? A trait comparison between rare and widespread species in restored Missouri glades

Background/Question/Methods

Understanding factors that limit species presence within restored habitats has been a longstanding goal of restoration ecology, especially in terms of factors that govern differences in the relative rarity and commonness between species. While some species are widespread and abundant, others are locally abundant, but regionally rare. These differences in occupancy rates may be heavily influenced by species traits since species traits may determine whether or not the species could persist locally when the habitat became degraded, and whether or not the species could recolonize when the habitat was restored. Traits important for allowing species to persist locally or disperse into restored habitats may include: wide habitat tolerances, clonality, perennial life-form, self-compatibility, wind dispersal, and small seed size. To determine if plant traits related to persistence or dispersal ability explain species occupancy patterns, I surveyed 32 restored cedar glades in Missouri. I assessed species occupancy and abundance and collected information on dispersal mechanism, breeding system, life-form, height, and habitat associations. I used a stepwise multiple regression analysis and AIC model selection to assess the extent to which the variance in occupancy could be explained by a composite of the aforementioned species traits.

Results/Conclusions

The multiple regression analysis indicated that the traits most important for explaining species occupancy in restored glades were dispersal mechanism, habitat association, and life-form (R-squared: 0.32, p=0.03). The results of this study provide several important implications for the future of restoration efforts. First, our results serve to indicate species that may be in need of active seeding efforts in restored areas such as species with annual or biennial life-forms, gravity dispersed seeds, and specialization on early successional habitats. Conversely, species with perennial life-forms, wind dispersed seeds, and habitat associations that include mid-successional habitats are likely to become widespread after restoration on their own. Second, our results may also aid in the prioritizing of habitat conservation. For example, habitats that are diverse in species with poor dispersal and persistence traits should be prioritized for conservation as they could serve as seed sources for other restored areas. In addition to these results, I will discuss some preliminary results from an ongoing establishment experiment that seeks to address whether or not species traits may explain establishment patterns under different stress and competitive treatments typically encountered in restored habitats.