Optimizing colonization proccesses to post-fire lands in Joshua Tree National Park

Background/Question/Methods

The ecological consequences of habitat loss and fragmentation differ depending on the spatial configuration of the landscape and how this influences colonization rates. Joshua Tree National Park (JTNP) in southern California is experiencing habitat loss and fragmentation due to an increase in fire size and frequency, which is facilitated by the invasion of non-native grasses. Even 65 years after a burn, a site within JTNP has not approached its pre-burned vegetation character. One conservation strategy that JTNP managers are implementing is planting vegetation patches within the burned areas, but the most cost-effective planting configuration is unknown.

Rodents are indicators of habitat quality due to their small home range and their influence on ecosystem structure via seed predation and dispersal, while terrestrial arthropods generally have short generation times making them ideal systems to monitoring subtle community changes.We examined the influence of landscape structure on rodent and arthropod colonization patterns as a way to assess how alternative planting schemes might influence community dynamics and restoration success.  We sampled rodent and arthropod community composition across a range of patch configurations by varying patch size, isolation levels, dispersal pathways, and surrounding matrix qualities.

Results/Conclusions

It was found that the habitat patch configurations that allow for a minimum of three colonization pathways was the most influential to rodent colonization, independent of patch size or distance from mainland (e.g. clustered, flower-like design  versus linear design). Ants were highly attracted to burned matrices, while spiders were typically found in pristine habitats. It was also found that both rodents and arthropods were negatively affected by the presence of a nearby second burn. For future vegetation plantings, we strongly recommend that habitat patches are planted in a clustered design to maximize colonization pathways rather than in a linear corridor configuration. We also recommend prioritizing areas within or near an area with multiple disturbances.