PS 29-99 - Are we able to predict the quality of hedgerow pollinator habitat restoration using local bee-plant interactions?

Background/Question/Methods

Pollination is an important ecosystem service, with 35% of crops dependent on wild and managed animal pollinators. However, populations of both wild and managed pollinators are declining globally due to habitat loss, fragmentation, and degradation. Even when managed pollinators are abundant, wild pollinators still contribute to pollinating crops. This effect is strongest when agricultural landscapes are proximal to florally diverse areas. Hedgerows, small amendments of native flowering plants, provide one such diverse area and a promising avenue for increasing occurrence of native bee pollinators in farms.

Bee-plant relationships are species-dependent, so the species planted in a hedgerow can have a large effect on the bee community. Tools have been developed to aid in choosing hedgerow plants that maximize various pollinator metrics (e.g., species richness, abundance, phylogenetic diversity, etc). Here we ask whether such tools can reliably predict attributes of the pollinator community by comparing tool-predicted and actual pollinator communities for a large data-set collected in California’s Central Valley. We also look at temporal patterns of pollinator assembly as a hedgerow matures after initial planting.

Results/Conclusions

Using bee-plant interaction data collected across agricultural, natural landscapes, and within hedgerows, we show the species composition as well as the number of plant species in the hedgerow, predict the abundance and species richness of the hedgerow bee communities. We expect when we score the plant mixes occurring at hedgerows, mixtures containing plants that rank highly in predicted species richness, abundance, phylogenetic diversity, and phenological continuity will also rank highly in the observed values for these metrics.

We surveyed sites comprising weedy control edges, mature hedgerows, or young maturing hedgerows (0-9 years old). Mature hedgerows exhibit higher species richness than control sites, and new hedgerows increase in species richness as they mature. Initial findings also indicate that phylogenetic diversity increases with hedgerow maturation. Therefore, we expect observed scores in hedgerows will better approximate predicted scores as the hedgerow matures. However, it is possible that as hedgerows mature, plant mixes change, complicating predictions.

Overall, we expect that the hedgerows surveyed will validate the predictive value of existing restoration tools and that predictions about hedgerow quality are more accurate for mature hedgerows. We hope this work will help establish conservation tools for planning pollinator conservation efforts in agricultural contexts.