Effects of Management Practices on Grassland Plant and Bird Community Composition in Kane County Forest Preserves

Loss of grassland ecosystems over the past century has increased importance of efforts to improve and restore habitat for native plant species and the biotic communities they support. As a result of these efforts, biotic and abiotic conditions and interactions with the environment are altered. Species evolution based on these particular environmental conditions has caused many species to be mapped onto various environmental gradients which can be defined as niche separation. This study attempted to determine what environmental gradients had the strongest impact upon grassland bird and plant species niche separation, particularly those gradients defined by management activities such as burning, chemical maintenance, and mechanical maintenance of forbs and brush. The main hypothesis tested was that abundance of grassland bird and plant species will be positively related to the increase in frequency of maintenance events including burn, chemical, and mechanical maintenance. The related sub-hypothesis is that bird and plant communities will also respond to other abiotic and biotic factors or characteristics of the sampling units. In 45 sampling units within 9 forest preserves in Kane County, IL. Plant species percent cover, bird species abundance, soil moisture, and vegetation structure were measured. Data including burn regime, chemical and mechanical maintenance, grassland age, and seeding/planting frequencies were obtained from the Forest Preserve District of Kane County. Other variables analyzed including percent fragmentation, grassland size, and proportion of neighboring habitat type (forest, wetland, and shrubland) or land use (developed or agriculture) were determined using ArcMap. Eighteen environmental/management factors were analyzed against 156 plant species and 42 bird species across the 45 sampling units using canonical correspondence analysis (CCA). CCA axes explained 45.1% and 51.5% of total variation in plant and bird species distributions, respectively. This study’s two hypotheses were partially supported because both grassland plant and bird species responded positively to mechanical maintenance of brush and forbs, prescribed burning, and other environmental factors. Top environmental/management factors that influenced plant species distribution were hours of mechanical forb maintenance; followed by proportion of neighboring forest, wetland, and shrubland within a 400m radius; hours of mechanical brush maintenance; vegetation height; and grassland size within a 200m radius. Top factors that influenced bird species distribution were soil moisture followed by grassland size within both 200m and 400m radii, percent fragmentation both 200m and 400m radii, hours of mechanical forb maintenance, and proportion of neighboring agriculture cover within a 400m radius. Ten factors, three of which were maintenance activities, influenced both plant and bird species distributions. Results of both plant and bird species CCAs suggest that there is no single dominating environmental gradient that influences distribution. Moreover, additional environmental factors not included in this study may influence both grassland plant and bird species distributions. This study highlights the importance of conducting observational analyses on management sites to determine what major factors influence species presence and how management decisions can best be used to have the largest benefit upon the community as a whole