COS 122-9
Bottom-up effects in restoration: Using non-target species and ecosystem function to measure success of wet-meadow restoration in the Sierra Nevada
Much of restoration ecology follows a bottom up paradigm - if appropriate conditions for species at lower trophic levels (plants and other primary producers) are created, species at higher trophic levels (pollinators, herbivores, and predators) will follow. Robust pollination services underpin the reproductive continuity of plant communities in restored systems, however because pollinators are rarely the target of restoration we know little about the impacts on pollinator populations and pollination function.
Bee and plant communities across twenty-two Sierra Nevada subalpine wet meadows were monitored from 2011 to 2013 to determine if and when pollination function is restored. Meadows were classified as restored, degraded, or remnant based on the status of floodplain connection. Restored meadows in the study range in age from one to sixteen years since pond-and-plug restoration was complete. Using a space-for-time proxy, each meadow represents a time-step at which floral and pollinator communities have reassembled. Floral diversity and abundance was measured using floral density transects. Each meadow was surveyed for flower visitors along a 500x1.5 m belt transect every fourteen days. Pollination function was directly measured via in situ pollen deposition, pollen tube development, seed set, and insect visitation for three plant species.
Results/Conclusions
Data showed diversity, evenness and species richness is positively correlated with time since restoration. Similarity among pollinator communities, visualized using nonmetric multidimensional scaling (NMDS), showed clustering by stage of restoration. Where young meadow bee communities more closely resembled degraded meadows, and old meadow communities (8 to 16 years) more closely resembled intact target meadows. A hand pollination study on Camassia quamash reveals it is not pollen limited in old restored meadows (L= -0.036, p= 0.46, df= 4). Single day pollen deposition to sentinel plants of C. quamash, Penstemon rydbergii, and Sidalcea oregana in restored meadows (age 2 to 16 years) received equal pollination compared to target meadows (p=0.81, df= 89). This is evidence that pollination function returns to target levels as early as two years post restoration. This research shows the non-target effect of hydraulic restoration predominantly drives deterministic succession towards a baseline/target conditions of community structure of bees and pollination services. The restoration and resiliency of ecological functions like pollination and plant-reproduction are ultimately critical measures of success in habitat restoration.