OOS 27-1 - Tree traits predict the abundance and diversity of soil organisms across century-old monocultures

Background/Question/Methods
Soil invertebrate communities play a large role in ecosystems by mediating above and belowground interactions. However, the factors shaping soil invertebrate communities are poorly characterized in forests. Tree traits influence soil properties and may be predictive of invertebrate communities. Many of the most abundant and diverse families of macroinvertebrates function in ecosystems remains largely undescribed. In this study, we characterized the effects of leaf habits and mycorrhizal associations on soil macroinvertebrate abundance and diversity. We conducted our study utilizing 18 single species forest plots at the Morton Arboretum in Lisle, Illinois. Plots represented all combinations of leaf habit and mycorrhizal association types. From June through July 2021, we surveyed soil invertebrate communities weekly using cover boards. We conducted a series of Generalized Linear Mixed effect models to predict the abundance and diversity of major orders of invertebrates by leaf habit and fungal association in R.

Results/Conclusions
From a total of 36,953 observed individuals over two months, our results show that macroinvertebrate communities vary with both leaf habit and mycorrhizal association. We observed a total of 20 orders across the 8 sampling dates. For seven of these orders (Coleoptera, Isopoda, Hymenoptera, Opiliones, Diplopoda, Orthoptera, and Aphids) abundance was generally higher in evergreen stands than in deciduous stands (P = 0.035). However, this was largely driven by higher abundance in ECM evergreen stands compared to ECM deciduous stands (interaction: P < 0.001). Additionally, both Shannon and Simpson Diversity Indices across plots were lower in evergreen and ECM fungal associations (interaction: P < 0.03). The specific environments created by tree species and their fungal associations seem to drive variability in the abundance and diversity of the macroinvertebrate community. As the range of evergreen and ECM is threatened with environmental change, it may have adverse implications on the diversity of key macroinvertebrate communities. While explicitly connecting soil communities to ecological function is necessary, these observed differences are important to understand on a species level as forest composition shifts with environmental change.