Date of Award

12-1-2018

Degree Name

Doctor of Philosophy

Department

Zoology

First Advisor

Whiles, Matt

Abstract

Ecological restorations have become increasingly important as humans have made irreversible changes to ecosystems; biogeochemical cycle alterations and land use changes have led to degraded conditions (Vitousek et al. 1997a). While some modifications to the environment are unavoidable, society is beginning to realize that changes are necessary. While some ecosystem functions may be beyond repair (e.g., biodiversity loss and extinction of species), it is important that the problem is faced head on and those functions that are still salvageable be restored. These environmental repairs can be done through ecological restoration. I looked at two different ecosystems, prairie streams and agricultural streams, that have undergone restoration to help functions. Patch-burn grazing (PBG) is increasingly used as a management practice on the few remaining tallgrass prairie parcels in an effort to simulate effects of large ungulate grazers. Yet, little is known about potential impacts and recovery of aquatic habitats from this management approach. My objective was to assess the influence of PBG with cattle on prairie streams and build on previous research at this site. I hypothesized that cattle grazing would negatively impact water quality and reduce stream biotic integrity, but riparian fencing would mitigate these impacts. We also assessed stream recovery for two years following the removal of ungulates from the study sites and hypothesized that biological and chemical effects would reverse. Six headwater streams (two controls, two PBG with 10 m fenced riparian zones, and two PBG with unfenced riparian zones) on Osage Prairie, Missouri, were sampled over seven years (2009-2015) encompassing pre-PBG (2 years), PBG (3 years), and post-PBG (2 years) periods. Macroinvertebrates and water chemistry were sampled monthly. Nitrate (NO3-) concentrations increased in the fenced and unfenced watersheds compared to the control watersheds (p = 0.015 and p < 0.0001, respectively) and between the fenced and unfenced watersheds (p = 0.001) during the PBG period relative to pre-PBG. Total phosphorus (TP) increased in the fenced and unfenced watersheds after grazing began compared to the control (both p < 0.0001) but did not differ between the fenced and unfenced watersheds (p = 0.187). Relative Chironomidae biomass and abundance increased in the unfenced watersheds in response to grazing (p = 0.008 and p < 0.001, respectively). No differences were observed in relative Chironomidae biomass and abundance, NO3-, and TP from pre-PBG to post-PBG indicating the recovery of these metrics. Results suggest that the negative effects of PBG on prairie streams can be somewhat mitigated by riparian fencing. Additionally, these streams are relatively resilient to PBG and recovery can take place during a rest cycle as brief as two years. Approximately one billion dollars is spent annually on restorations of degraded stream reaches in the United States. However, few projects are monitored upon completion, or monitoring focuses on a single parameter. Other than modifications to physical attributes of streams, the influence of restoration projects on ecosystem processes remains largely unknown. We sampled eleven Midwestern streams that had undergone habitat restorations from 3-15 years prior to sampling. Restoration techniques included in-stream habitat enhancements, bank stabilization, and riparian restoration. We predicted that gross primary production (GPP) would be lower in restored streams due to decreased nutrient inputs, and that respiration would be greater due to increased litter inputs from restored riparian areas. We also hypothesized that the restored streams would have greater invertebrate richness, abundance, and biomass, as well as high densities of intolerant taxa such as Ephemeroptera, Plecoptera, and Trichoptera (EPT taxa) due to higher water quality and better habitat. Restored reaches and unrestored upstream reaches were sampled for physical characteristics, water chemistry, benthic algal biomass, whole-stream metabolism, and macroinvertebrate communities. GPP in restored sites was marginally higher than unrestored sites (t5 = 2.53, p = 0.05), despite no differences in PO4-3, NO3-, or NH4+ concentrations. Three restored sites were autotrophic (P/R > 1), while four unrestored sites were heterotrophic. Total macroinvertebrate biomass was marginally higher in the restored sites compared to unrestored sites (t10 = 1.94; p = 0.08). EPT biomass was also marginally higher in restored sites than unrestored sites (t10 = 1.91; p = 0.09) but no difference was observed in EPT abundance. Results suggest that stream habitat restorations enhance some, but not all ecosystem processes and marginally enhance macroinvertebrate communities.

Available for download on Thursday, August 22, 2019

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