Floral abundance and soil characteristics affect wild bee community structures and nesting dynamics in tallgrass prairies

prairie;community;bee;management;plant;patch-burn-graze;soil;interaction

Buckles, Brittany J ; Harmon-Threatt ; Alexandra N.

关键词: prairie;    community;    bee;    management;    plant;    patch-burn-graze;    soil;    interaction;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/89062/BUCKLES-THESIS-2015.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Tallgrass prairies have been reduced to less than 5% of their former range, yet provide essential habitats for many native plants and animals such as pollinators. Land managers work to preserve the biodiversity within these tallgrass prairies by implementing management techniques such as burning, haying, and patch-burn-grazing (PBG). All treatments utilize burning, but haying removes aboveground biomass and PBG includes grazing by cattle. The impacts of these management practices on important ecological factors for bee species, such as floral community structure and nesting resources are examined in this study. Floral resources and bee communities are usually positively correlated within ecosystems due to their mutualistic interactions. The interactions between flowers and bees are important in maintaining the sustainability of many ecosystems including managed prairies. In Chapter 1, I investigate how management alters the abundance, richness, diversity, and composition of both plant and bee communities and whether there are differences in the interactions between bee species and the plants they forage on within 20 different prairie sites in Missouri. Analyses were conducted for the four treatments and by collapsing the treatments into two groups, grazed and ungrazed. I discovered that floral abundance in ungrazed sites is higher than on sites that support cattle. However, the bee communities that utilize prairie ecosystems do not change based on management techniques. This may be due to the resilience of the bee species that occur in Missouri compared to the species that occurred in Missouri before the landscape was fragmented. Species remaining in the highly disturbed prairie fragments may be less specialized and better adapted at persisting despite the difference in management. Despite there being no difference in bee communities in grazed and ungrazed patches, the interaction networks between bee species and their host plants are more complex in the prairies without cattle and more competitive in the prairies with cattle. Additionally, out of the 1769 bees included in my study, only two were honey bees. Therefore, I found no evidence that honey bees are displacing native bees in prairie ecosystems. Soil characteristics could also affect bee community structure and nesting rates on prairies because most bees nest underground for the majority of their lives. In Chapter 2, I investigate the soil characteristics within the four management treatments including temperature, moisture, pH, bulk density, composition, and bare ground ranks and compare the measurements to ground-nesting bee nesting rates. I used emergence tents to collect ground-nesting bees and associated soil cores. The soil composition was not different based on management techniques, but sites without grazers supported a higher nesting rate compared to PBG sites. This difference may be attributed to lower soil moisture and bulk density, and higher pH and bare ground in ungrazed sites compared to sites that included cattle all of which have been previously associated with increased bee nesting.In Chapter 3, I discuss collecting the rare Macropis steironematis Robertson 1891. She was collected at Stony Point Prairie Conservation Area (37° 31.640’, -94° 01.688’) on June 19, 2014 while foraging on Rosa carolina, the prairie rose.Only a few ambiguous records of this species have been recorded in the United States and, to the best of my knowledge, no extant specimens are available from the state of Missouri. My study provides evidence that the oil-collecting bee, M. steironematis is still present in Missouri.Overall, this study assesses differences in prairie management such as burning, haying, and the time of burning in PBG. I found that PBG, regardless of the time of the last burning, reduces floral abundance and nesting rates of ground-nesting bees compared to sites that are burned and hayed. Additionally, PBG sites had higher soil moisture and bulk density, and lower pH and bare ground compared to sites that were burned or hayed, which could negatively affect nesting rates on prairies. However, PBG does not reduce the tallgrass prairie bee communities, but it does interfere with important bee-plant interactions by increasing competition between bees and decreasing the complexity of the interactions when compared to sites that are managed with burning or haying.