Assessing the effects of mesh enclosures on invertebrates and litter breakdown in a floodplain forest of the southeastern USA
The litter bag method has been used to study litter breakdown for over 50 years but remains a criticized technique. One major criticism is the effect of mesh enclosures, specifically the use of two or more mesh sizes to evaluate the role of arthropods, on litter breakdown. We aimed to evaluate the effectiveness of a new basket-style mesh enclosure in mitigating microclimatic mesh effects while still excluding invertebrates. We evaluated five basket treatments constructed from 300-lm mesh: no basket, closed basket, closed basket with bottom slits, open basket, and open basket with bottom slits, which held invasive Chinese privet (Ligustrum sinense) litter on the Oconee-River floodplain, GA, USA. After 134 days, we found that temperature and humidity did not vary among treatments but that litter breakdown rates (k) and invertebrate composition were different among treatments. Litter breakdown was faster in the no basket treatment (the most open treatment) than in closed baskets without slits (the most closed treatment). Microinvertebrates were not effectively excluded from baskets but most macroinvertebrates were excluded from baskets (open and closed) without slits, except for some small predators. Unexpectedly, we found some evidence that using litter bags of two different mesh sizes may have a secondary trophic effect on litter breakdown, further complicating how best to evaluate the impact of arthropods on litter breakdown.