Joseph LaForge

Pollinators and their pollination services maintain native plant diversity, which in turn impacts the diversity and abundance of species that depend on those floral resources, such as herbivores and seed-eaters. To restore tallgrass prairies, prescribed burns are used to replicate the historic fires that played a key role in maintaining the expanses of herbaceous vegetation. Although much is known about the effects of spring-applied burns on grasslands, burns during other seasons are increasingly recommended as an alternative management practice. Unfortunately, the effects of these alternative burns on plant-pollinator interactions, and thus wildflower seed production, are poorly understood. Here we sought to characterize the recruitment of insect pollinator communities to Pediomelum tenuiflorum, a native perennial found throughout Kansas, following two different seasonal burning regimes (Spring, Fall) in a replicated experimental design. In response  to the exceptional drought experienced by the plants, we observed low primary pollinator visitation rates and minimal seed production. This minimal seed production led to a lack of seed pods collected. Many seeds were seen to abort before reaching maturity.

Cellulose, the major component of plant biomass, is largely indigestible and therefore unavailable as an energy source to most organisms. Some bacterial species use cellulase enzymes to hydrolyze cellulose and release sugar subunits for subsequent metabolism. This work aims to characterize species composition and metagenomic features of microbial communities that survive solely on cellulose. Ten soil communities (C#) were established on carboxymethylcellulose (CMC) as an organic carbon source. Universal primers for fungal 18S rRNA indicated that fungi are not present in these communities. 16S rRNA metagenomic sequencing identified the “Operational Taxonomic Units (OTUs)” comprising each bacterial community.

Cellulose is a major carbon source for many microbial soil communities, but the community interactions between cellulolytic and non-cellulolytic species during cellulose degradation is poorly understood. In this investigation, metagenomic sequencing revealed a high level of variability in species diversity and composition of ten microbial assemblages randomly established on carboxymethylcellulose (CMC) plates from the same temperate soil sample. The number of species, or operational taxonomic units (OTUs), per established assemblage ranged from 33 to 236, and three “assemblage clades” with distinct community structures were identified. Only two OTUs were common to all ten assemblages, but these appear to play a minimal role in cellulose metabolism. Achromobacter (OTU7), a non-cellulolytic Betaproteobacterium, was the predominant component of the GW-C clade, which demonstrated the most consistent and rapid growth on three different cellulose-based substrates. Whole metagenomic sequencing of two of the GW-C assemblages identified two Actinobacteria species, Cellulosimicrobium sp. and Kitasatospora sp., which are particularly enriched with cellulolytic genes. A third Actinobacteria species, Gordonia sp., from the GW-A clade is also highly enriched in cellulolytic genes. All three Actinobacterial species were isolated and tested for CMC digestion rates in monoculture and in various combinations. Interestingly, the highest cellulolytic rates were only observed in the presence of Achromobacter. This study shows that integrated waste management practices and cellulose-based biofuels industries would benefit by optimizing cellulolytic species composition.