Plant community responses to grassland restoration efforts across a large‐scale precipitation gradient

Abstract

Identifying how plant species diversity varies across environmental gradients remains a controversial topic in plant community ecology because of complex interactions among putative factors. This is especially true for grasslands where habitat loss has limited opportunities for systematic study across broad spatial scales. Here we overcome these limitations by examining restored plant community responses to a large‐scale precipitation gradient under two common Conservation Reserve Program (CRP) restoration approaches. The two restoration strategies examined were CP2, which seeds a relatively low number of species, and CP25, which seeds a higher number of species. We sampled plant communities on 55 CRP fields distributed along a broad precipitation gradient (410–1,170 mm mean annual precipitation) spanning 650 km within the grassland biome of North America. Mean annual precipitation (MAP) was the most important predicator of plant species richness and had a positive, linear response across the gradient. To a lesser degree, restoration practices also played a role in determining community diversity. The linear increase in species richness across the precipitation gradient reflects the species pool increase from short to tallgrass prairie communities and explained most of the richness variation. These findings provide insight into the diversity constraints and fundamental drivers of change across a large‐scale gradient representing a wide variety of grassland habitats. Across a broad environmental gradient, initial planting differences between restoration practices had lower effects on plant diversity than expected. This suggests that new strategies are needed to effectively establish diverse plant communities on large‐scale restorations such as these.

Precipitation, Not Land Use, Primarily Determines the Composition of Both Plant and Phyllosphere Fungal Communities

“…The broad variability in MAP not only affects ecosystem annual net primary productivity, but also plant community composition, cover, and diversity (Lauenroth et al, 1978;Watson et al, 2021). Our results are congruent with Watson et al (2021) and suggest that MAP is an important plant diversity predictor for regionally distinct plant communities. Our indicator taxon analyses highlighted that it is indeed the dominant graminoids that define these grassland communities, particularly so in the mesic tallgrass prairies.…”

“…Plant communities and their shifts along gradients have been extensively studied (see Watson et al, 2021), whereas similar studies on fungal communities and/or their diversity are less common (but see e.g., Tedersoo et al, 2014;Glynou et al, 2016;Rudgers et al, 2021). Factors that may affect fungal communities include latitude (Arnold et al, 2000;Arnold and Lutzoni, 2007;Tedersoo et al, 2014), climate (McGuire et al, 2012U'ren et al, 2012;Zimmerman and Vitousek, 2012;Eusemann et al, 2016;Oita et al, 2021;Rudgers et al, 2021), soil (Tedersoo et al, 2020;Bowman and Arnold, 2021;Rudgers et al, 2021), plant host (Hoffman and Arnold, 2008;U'ren et al, 2012;Lau et al, 2013;Kembel and Mueller, 2014;Tedersoo et al, 2020;Rudgers et al, 2021), and disturbance (Delgado-Baquirizo et al, 2021).…”

Ground Beetle (Coleoptera: Carabidae) Responses to Cattle Grazing, Grassland Restoration, and Habitat across a Precipitation Gradient

“…This was not due to a larger species pool and associated increase in abundance of carabid species. This differential response in the East region was also seen in plants associated with Kansas CRP [ 52 ] and may be driven (at least in part) by the increased mean annual precipitation. The comparatively high mean annual precipitation in the east may create differences in microhabitat availability and plant community structure, thus improving resources for insects.…”

“…While we were able to standardize grazing pressure across the precipitation gradient, there were numerous factors out of our control, such as the age of each restoration and the frequency at which the sites were burned. Historically, CP2 is the older of the two practices, thus CP2 sites were typically established earlier (25.26 ± 0.90 [SE] yr) than CP25 sites (13.85 ± 0.92 [SE] yr) [ 52 ]. Additionally, burning was used as a mid-contract management more frequently in eastern tallgrass sites (33.6% of sites) than in western short grass (1.2% of sites).…”

“…As part of a broader three-year study (2017–2019) on various organisms including birds [ 50 , 51 ], arthropods [ 50 ], and plants [ 52 ], a randomized list of CRP landowners in Kansas was obtained from the United States Department of Agriculture (USDA), which administers the CRP. Eligibility of a site was determined by minimum area requirements for birds (≥35 acres/14.2 ha [ 53 , 54 ]), distance from the next closest site (≥1 km), and the year it was enrolled in CRP (2012 or earlier, and with a contract not expiring before September 2019).…”