Long-term effects of connectivity on plant species richness

Background/Question/Methods

Landscape connectivity – or the degree to which the landscape facilitates dispersal – is a fundamentally important factor regulating species diversity and is becoming increasingly in human-dominated landscapes that are affected by habitat fragmentation and climate instability.  The impact of connectivity on diversity, however, is not well understood. In particular, there are no long-term experimental tests of how connectivity affects species diversity over long time scales. We ask how connectivity affects plant species richness over time using a long-term dataset from a large, replicated landscape experiment that tests for connectivity effects with the presence of structural corridors.  We also assess the relative importance of the ecological processes (i.e., colonizations, extinctions) responsible for these patterns over time.

Results/Conclusions

In our experimental landscapes, connectivity has increased plant species richness over time. After twelve years, plant species richness is 20% higher in connected vs. unconnected patches.  However, an initial increase in species richness due to connectivity has since reached a stable effect, suggesting that connectivity effects may reach a long-term plateau.  The positive effects of connectivity we have observed are generated by both increased colonizations and decreased extinctions, but the relative importance of these two processes changes over time.  Our results indicate that the magnitude of connectivity effects change over time, which has important implications for long-term landscape conservation and management.