Document Type


Publication Date

Spring 3-2022


Aquaculture and Fisheries | Biodiversity | Forest Biology | Other Animal Sciences | Other Ecology and Evolutionary Biology | Terrestrial and Aquatic Ecology

Description, Abstract, or Artist's Statement

Decomposition plays an important ecological role in carbon and nutrient cycling that supply food and energy resources to food webs. This study investigates the potential role that leaf decomposition of different leaf species may play in macroinvertebrate assemblages in upper Midwest streams. We hypothesized that the different decomposition rates experienced with different leaf species and in different streams would have an effect on invertebrate colonization due to the variance in nutrient availability. Due to altered fire regimes and other influences, forests are experiencing declines in fire-adapted, heliophytic species such as oaks and compositional shifts toward shade-tolerant, mesophytic species such as maples. This compositional shift in forest species, also known as Mesophication, may have implications for macroinvertebrate communities. Sugar Maple (Acer saccharum) and Bur Oak (Quercus macrocarpa) leaves were chosen to test the effect of their decomposition on invertebrates due to their prevalence in the Midwest, research supporting their expected difference in decomposition rates, and implications for Mesophication. Dried leaves were placed into 60 mesh bags (30 of each leaf species) with a starting dry mass of 5g ± 0.1, into three different streams for 22 days. Mass loss was measured to quantify decomposition rates and macroinvertebrates within each mesh bag were collected and identified to the family level. In agreement with past research, Sugar Maple leaves decomposed significantly faster than Bur Oak leaves. Leaf decomposition rate varied significantly across the experiment (ANOVA, F= 55.428, p= 0.000) and was strongly impacted by leaf type (ANOVA, F=264.449, p=0.000) and by stream (ANOVA, F=5.640, p=0.006) . However, contrary to our hypothesis, leaf type did not have an effect on invertebrate communities observed in the leaf bags in terms of abundance, Simpson’s diversity, Shannon’s diversity, or Family Biotic Index. Likewise, stream did not have an effect on macroinvertebrate indices, except for richness (ANOVA, F=5.047, p=.010). Invertebrate assemblages in all streams were dominated by predator and collector/gatherer taxa. Overall, leaf type did not have a significant effect on macroinvertebrate communities found colonizing the leaf packs despite the leaf types significant difference in decomposition rates. A possible explanation for this lack of effect is that the numerically dominant predator and collector/gatherer taxa may rely on leaf types for habitat or protection from predators as opposed to being directly involved in the decomposition process like shredders (which were rare in all streams). Further research might include allowing for a longer decomposition time to look for the impact of later colonizing species or species that may differ in preference once the difference between leaf types becomes more pronounced later in decomposition.