Pasture management, grazing, and fire interact to determine wetland provisioning in a subtropical agroecosystem
Sonnier, Grgory, Pedro F. QuintanaAscencio, Patrick J. Bohlen, John E. Fauth, David G. Jenkins, and Elizabeth H. Boughton. Pasture Management, Grazing, and Fire Interact to Determine Wetland Provisioning in a Subtropical Agroecosystem. Ecosphere 11, no. 8 (2020).
Wetlands in agroecosystems provide multiple ecosystem services, including provisioning services such as forage production. Here, we examine how pasture management intensity (semi-natural pastures vs. highly managed pastures (fertilized, heavily drained, planted with productive grasses), cattle exclusion (grazed vs. fenced), prescribed ﬁre (burned vs. unburned), and their interactions affect provisioning services provided by small, isolated, and seasonally ﬂooded wetlands in subtropical pastures and rangelands. We used a replicated, full-factorial experiment on 40 seasonally ﬂooded wetlands located in Florida (USA), and measured standing plant biomass and annual net primary productivity in each wetland. Biomass was sorted by species to calculate species abundance of palatable and unpalatable plants. We used general linear mixed models to evaluate the effect of treatments and their interactions on biomass quantity, plant tissue nutrients (% C, % N, and % P), and forage nutritive value (using in vitro organic matter digestibility). Plant standing biomass and productivity were greatest in wetlands embedded in highly managed pastures, but in grazed wetlands, a large proportion of this biomass was unpalatable to cattle. Excluding cattle from wetlands in highly managed pastures increased productivity, standing biomass, and the amount of palatable species (~6.3 t/ha) compared to grazed wetlands (~3.3 t/ha), especially when these wetlands were also exposed to prescribed ﬁre. Total P in plant tissue was consistently higher in wetlands within highly managed pastures, but total N responses to treatments varied between years. In vitro digestibility was higher in vegetation from wetlands within highly managed pastures, but not in fenced wetlands despite the higher amount of palatable species, suggesting that palatability and digestibility were decoupled. Subtropical wetlands in agroecosystems provide substantial provisioning services, and our study suggests that targeted management can increase these services. However, the pasture type surrounding a wetland interacts with grazing and ﬁre management to affect provisioning services. We propose that fencing off selected wetlands (speciﬁcally in highly managed pastures) followed by low-intensity grazing with adequate resting periods could beneﬁt ranchers and have less persistent impacts on this ecosystem.