Decomposition in aquatic and terrestrial invaded systems: Scientific and educational insights from collaboration within the Ecological Research as Education Network

Background/Question/Methods

In this collaborative project, faculty in the Ecological Research as Education Network (EREN) and their students are using a common, web-accessible litterbag protocol to collect decomposition data for invasive and native species. The introduction of woody invasive species has been shown to significantly alter nutrient dynamics within the areas they invade, yet the impact of these invasions may extend beyond the terrestrial habitat into local streams, and the impact of the invasion in both these ecosystems may be dependent on the relative abundance of the invasive. Our objectives for this study are to (1) develop and test integrative protocols for aquatic and terrestrial decomposition that can be conducted in the context of an undergraduate curriculum, (2) experimentally test whether decomposition rates of invasive species are faster than the decomposition rates of native species across a wide range of environments and (3) identify the invasive abundance necessary to affect decomposition rates. To simulate different levels of invasion, litterbags were filled with leaf litter from woody species using five invasive:native ratios. Ten replicates of each treatment were deployed into a stream and also into a nearby upland area at each site, and then collected at intervals throughout the following year to assess mass loss.

Results/Conclusions

While invasive litter did often decay faster than native counterparts, this pattern was not universal for all species or at all sites. For example, Rhamnus cathartica litter decayed faster than native counterparts but Ailanthus altissima decayed similarly to its native counterparts at all sites, reinforcing the importance of species-specific litter quality. Decay in some mixtures also appeared nonadditive, though this also varied among sites, habitat, and time of sampling. Ten faculty contributed data during the first year of the project, and this number has doubled in second year of the project, with 20 faculty from 18 different schools currently participating. This decomposition project was incorporated into undergraduate teaching in a variety of ways, each with unique benefits and challenges. Pairing an independent study student with a course, or pairing multiple courses are some ways to manage the large amount of lab processing required while providing maximal student engagement.