Effects of Drought Conditions on Microbial Communities in Native Rangelands

Climate change is a result of greenhouse gases released into the atmosphere. These changes are expected to cause extreme weather conditions, including severe storms. Large amounts of rain will fall in shorter periods of time, leading to heavy runoff, and increasing the severity of drought conditions within the soil (Zeglin et al. 2013). Native grasslands occupy almost a quarter of the earth’s land surface and are valuable ecological resources. They contain soils with high concentrations of organic matter and play a key role in mitigating greenhouse gas emissions through carbon sequestration. There are a variety of grassland management techniques including annual burning, patch burning, and cattle grazing. These management techniques can be beneficial for ecosystems, but can also alter soil compositions (Jerome et al. 2014). Microbial communities in the soil influence many ecosystem processes such as nutrient acquisition, carbon and nitrogen cycling, and soil formation (Heijden et al. 2008). Changes in precipitation patterns can effect microbes in these grasslands by causing shifts in community composition, and changes in nutrient cycling and decomposition processes. Many microbial activities can be directly correlated with water availability, and drought conditions may be detrimental to these grazed grassland ecosystems (Gray et al. 2011). Summer months and differences in time lead to changes in temperatures and rainfall patters, similarly having the potential to alter activity and structure of microbial communities. This study was conducted at the Konza Prairie Biological Station in eastern Kansas, USA. Soil samples were collected to compare June versus July and moist versus dry treatments. Findings from this study concluded that seasonal changes through June and July alter microbial communities in Konza Prairie soil. Total PLFA concentrations significantly increased, with the largest increase occurring in fungi. This change caused a decrease in relative abundance of gram positive and gram negative bacteria, and also an increase in the ratio of fungi to bacteria. Drought conditions caused no significant change in microbial communities, suggesting the microbes in the soil have a high tolerance for lack of moisture

Sediment Phosphorus Release at Lake Fayetteville, Summer 2020

The purpose of this project was to evaluate the release of dissolved phosphorus (P) from bottom sediment at Lake Fayetteville, and the potential use of aluminum sulfate (Al2(SO4)3) to remediate the P stored and released by bottom sediments. Intact sediment cores (n=18) were taken at three locations, named inlet, mid and dam sites at Lake Fayetteville. The cores were incubated with 1 L of overlying water with light excluded and bubbled with air (half, aerobic treatment) and N2 (other half, anaerobic). Water samples were pulled and analyzed for soluble reactive P (SRP), and that water was replaced with filtered lake water with SRP less than the lab’s method detection limit (MDL, ≤0.005 mg L‐1). The SRP mass accumulating in the overlying water was used to estimate SRP release rates from the sediment, and mean rates were compared by treatments, sites and before and after alum dosing. Sediment SRP release rates were significantly greater under anaerobic conditions (mean=7.22 mg m‐2 d‐1) than aerobic (mean=0.85 mg m‐2 d‐1), and within those conditions rates were not different between sites. The addition of alum to the overlying water reduced SRP concentrations near the MDL in most cores, and sediment SRP release rates were significantly less after alum dosing, except for the cores from the mid lake site under aerobic conditions. Overall, it likely that this internal SRP source is an important factor in the development and occurrence of harmful algal blooms (and likely microcystin production) at Lake Fayetteville. Alum might be a means to successfully reduce this internal SRP source