Research on invasive species has documented myriad ecosystem and community effects; yet still ecologists grapple with concrete mechanisms producing these effects. Plant detritus provides a major link between community and ecosystem ecology and in terrestrial systems is the major pathway through which most system energy flows. Here I report results of a three-year invasive grass litter manipulation in a semi-arid, formerly shrub-dominated, system. Working with non-native grasses that are common and widespread throughout western North America, I added and removed grass litter in areas of both high and low non-native grass abundance. For two years thereafter I followed a number of soil, shrub and arthropod parameters.
Results/Conclusions
Contrary to many other studies, but consistent with my earlier observational work, I found native shrubs were enhanced in areas of both manipulated and naturally higher grass litter abundance. They showed greater new growth, and supported a greater abundance and richness of shruboreal arthropods. Neither soil nor native shrub leaf tissue carbon and nitrogen content showed significant differences due to my litter treatments, but soil temperature decreased while soil moisture significantly increased with non-native litter cover. I can therefore trace a pathway by which non-native grass produces abundant litter which lowers soil temperature and then can significantly increase soil moisture, leading to more native shrub growth and larger, more speciose arthropod communities. This may trigger effects further up the food web and highlights the importance of considering both community and ecosystem effects by invasive plants when attempting to understand more clearly how they act on native landscapes.