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Understanding the effects of agricultural land use on wetland N cycling is critical in areas such as south-central Florida, where widespread agricultural activities intersect with extensive wetland systems. We examined annual net N mineralization ([N.sub.min]) (buried-core method) and denitrification rates (acetylene-block method) in 24 small seasonal wetlands on a cattle ranch in this region, 12 each in intensively managed improved pastures (IP) and less intensively managed semi-native pastures (SNP). Wetlands in IP had less detritus, higher N concentrations, lower C/N ratios (0-15 cm), and higher microbial biomass N than did wetlands in SNP. Cumulative annual net [N.sub.min] was lower in IP wetlands (98 [+ or -] 17 kg N [ha.sup.-1]) than in SNP wetlands (133 [+ or -] 18 kg N [ha.sup.-1]). Nitrification was much lower in IP than in SNP wetlands and dominated net [N.sub.min] during the dry season (December-June), but was negligible during the flooded period (July-October). Cumulative annual denitrification was lower in IP wetlands (17.7 [+ or -] 3.4 kg N [ha.sup.-1]) than in SNP wetlands (34.7 [+ or -] 6.3 kg N [ha.sup.-1]). Soil N cycling rates correlated with N[O.sub.3.sup.-] and N[H.sub.4.sup.+] concentrations, which correlated with soil C content. Our results show that the more intensive management of improved pastures was associated with declines in wetland soil C content and lower rates of nitrification and denitrification. Abbreviations: IP, improved pasture; OM, organic matter; SNP, semi-native pasture.

Land use practices exert a major influence on plant productivity, soil and plant nutrient content, and within-stand nutrient cycling in wetlands in agricultural landscapes. We examined differences between improved and seminative pastures in plant and soil nutrient characteristics in seasonally flooded wetlands in subtropical grazing land of south central Florida. The wetlands were embedded within either grazed improved pastures with a long-term history of fertilizer application or seminative pastures with no history of previous fertilizer application. Soil nutrient concentrations decreased with soil depth for both land use types. Total C, N, and P were significantly greater (P < 0.05) in the 0- to 15-cm mineral layer compared with the deeper layers (15-30, 30-45 cm) for both improved and seminative pasture wetland soils. Improved pasture wetlands had greater amounts of total P (22.3 kg P [ha.sup.-1]) in the upper 0- to 15-cm soil layer than did the seminative pasture wetlands (15.7 kg P [ha.sup.-1]). Plant and soil (0-15 cm) N/P and C/P ratios were lower in improved pasture wetlands compared with seminative pasture wetlands, suggesting greater P enrichment in improved pasture wetlands. Microbial biomass C and N decreased with soil depth in both pasture types. Soil microbial biomass C/total C ratios decreased with soil depth and were similar for both improved and seminative pasture wetlands. Our results suggest that plant and soil nutrient enrichment and storage in temporary wetlands may be impacted by adjacent land use practices, which potentially leads to the alteration of the structure and functions of these wetland ecosystems.

Expanding global commerce may be increasing the likelihood of exotic earthworm invasions, which could have negative implications for soil processes, other animal and plant species, and importation of certain pathogens. [...]

Aims: The stress gradient hypothesis predicts that competition will be important in productive environments while facilitation will be common in environments with high stress or consumer pressure. However, abiotic stress and grazing may vary independently and even occur simultaneously. Here we examine the outcome of plant interactions in grazed wetlands where consumer pressure and abiotic stress occur concurrently. We hypothesized that cattle grazing and microhabitat would alter the outcome of plant interactions. Given that wetland edges are drier and less productive than wetland centers we expected that facilitation would be greatest in drier wetland edges due to greater abiotic stress regardless of cattle presence. Location: Archbold Biological Station's Buck Island Ranch (BIR), south‐central Florida, USA (27°09′ N, 81°11′ W). Methods: We conducted an experiment for two growing seasons in ten wetlands, five exposed to cattle grazing and five fenced. Two wetland obligate plants were included (Panicum hemitomon and Alternanthera philoxeroides), and plots were assigned to three treatments (a) all neighbors removed; (b) all neighbors removed except Juncus effusus, a dominant, unpalatable plant; and (c) all neighbors intact (control), in both wetland centers and edges. Differences in survival, change in height and number of leaves were assessed. Results: In ungrazed wetlands, plant survival was higher in wetland edges vs centers, while it did not differ between microhabitats in grazed wetlands. Survival in wetland edges was further increased by the presence of Juncus effusus. Positive interactions under grazed conditions were clear when plant height was assessed, but negative interactions affected leaf production in both ungrazed and grazed wetlands. Conclusions: Grazing interacts with wetland microhabitat to alter plant survival. Facilitative interactions on plant height were apparent in grazed wetlands. Understanding how plant interactions change under different biotic and abiotic contexts is important for informing ecosystem restoration and management. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Aims Understanding the drivers of grassland structure and function following livestock removal will inform grassland restoration and management. Here, we investigated the effects of fire and nutrient addition on structure and function in a subtropical semi-native grassland recently released from grazing in south-central Florida. We examined responses of soil nutrients, plant tissue nutrients, biomass of live, standing dead and litter, and plant species composition to experimental annual prescribed fire applied during different seasons (wet season vs. dry season), and nutrient additions (N, P and N + P) over 9 years. Methods Experimental plots were set up in a randomized block split-plot design, with season of prescribed fire as the main treatment and nutrient addition as the subplot treatment. Species cover data were collected annually from 2002 to 2011 and plant tissue and plant biomass data were collected in 2002-2006 and 2011. Soil nutrients were analyzed in 2004, 2006 and 2011. Important Findings Soil total phosphorus (P) levels increased substantially with P addition but were not influenced by prescribed fire. Addition of P and N led to increased P and N concentrations in live plant tissues, but prescribed fire reduced N in live tissue. Levels of tissue N were higher in all plots at the beginning of the experiment, an effect that was likely due to grazing activity prior to removal of livestock. Plant tissue N steadily declined over time in all plots, with annually burned plots declining faster than unburned plots. Prescribed fire was an important driver of standing dead and litter biomass and was important for maintaining grass biomass and percent cover. Nutrient addition was also important: the addition of both N and P was associated with greater live biomass and woody forbs. Removal of grazing, lack of prescribed fire, and addition of N + P led to a reduction of grass biomass and a large increase in biomass of a woody forb. Annual prescribed fire promoted N loss from the system by reducing standing dead and litter, but maintained desirable biomass of grasses. [ABSTRACT FROM AUTHOR]

In the USA, the United States Department of Agriculture (USDA) Natural Resource Conservation Service (NRCS) has restored millions of acres of wetlands through its Wetland Reserve Easement (WRE) programs. However, few quantitative studies have explored whether WREs have enhanced wetland hydrology and wetland plant communities. Additionally, USDA Compatible Use Permits for cattle grazing and other management practices are sometimes issued for WREs, but little is known about potential benefits/detriments of such practice on the success of wetland restoration. In this study, we tested if hydrological restoration of previously drained species poor pastures increased water depth and hydroperiod. Restoration involved plugging key ditches, adding water control structures and a berm. We also tested if hydrological restoration increased plant diversity (alpha and beta), floristic quality (using coefficient of conservatism) and increased the cover of wetland species (using species wetland status). Finally, we tested if cattle grazing had an effect on the success of restoration by comparing grazed plots to fenced plots. We studied two conservation easements (a total of 748 acres) located on semi-native pastures in central Florida, USA. We monitored vegetation using permanent transects stratified by vegetation type before (2004–2005) and after (2012) the restoration (2008). We assessed wetland hydroperiod using groundwater wells set up in 2003 and located within and outside the boundaries of these two easements. We used linear mixed models and multivariate analyses to compare vegetation and hydroperiods pre- and post-restoration. Number of flooded days increased following restoration in one of the easements, but we did not detect significant changes in hydrology in the other easement. Floristic quality, beta diversity and cover of obligate wetland species increased in both conservation easements and in most vegetation types. These vegetation changes were likely due to restoration activities since annual rainfall was not significantly different pre- and post-restoration. Cattle grazing did not have a negative or positive effect on the success of restoration, nor did we detect any positive effect of grazing on the success of restoration. Overall, our study shows that hydrological restoration can enhance wetland hydroperiod, water depth and wetland vegetation, but more resources should be allocated to short- and long-term monitoring of the restoration success. [ABSTRACT FROM AUTHOR]

Abstract: Semi-natural grasslands have become increasingly important to conservation in both temperate and subtropical regions due to their diversity and escalating pressures toward conversion or abandonment. As more semi-natural grasslands are incorporated into conservation easements or other protected areas, questions arise about appropriate management for maintaining biodiversity. We conducted an 8year split-plot experiment on the effect of season of burn and nutrient status on plant composition in semi-natural grassland released from ranchland management. Our objective was to find alternative approaches to manage semi-natural grasslands under varying nutrient enrichment when typical ranch management is ceased. We predicted that: (1) burning at high fertility would counteract competitive exclusion and increase diversity and that this increase would be greatest in the historical fire season (summer) to which species are adapted; and (2) that plant composition in plots released from disturbance would shift to greater abundance of competitive species, including shrubs, which would displace smaller grass and forb species and result in reduced diversity. Total species richness and graminoid richness were lowest in unburned, ungrazed plots. Graminoid richness was greatest in winter burned-grazed plots (due mainly to sedges) and forb richness was greatest in summer burn plots. In unburned plots, after 5years, a native shrub, Eupatorium capillifolium (Lam.) Small, and native forb, Lachnanthes caroliniana (Lam.) Dandy, became abundant and grasses declined. Winter burn plots were dominated by a small shrub, Euthamia graminifolia (L.) Nutt. var. hirtipes (Fernald) C. and J. Taylor. Our experiment suggests that maintaining grassland structure and reducing shrub cover in grasslands released from typical ranchland management in subtropical Florida requires burning, and that summer is the most beneficial season of burn to reduce shrub encroachment and encourage both graminoid and forb richness. [Copyright &y& Elsevier]

The article presents a study on the effectiveness of pasture water management in controlling the loss of nutrients in surface runoff in the Northern Everglades in Florida. It investigates two water management treatments on Bahia grass such as the reduced flow treatment and unobstructed flow. It notes that the reduced flow treatment was applied in the pastures by installing water control structures in drainage ditches. It indicates the effectiveness of pasture water retention in reducing runoff volume and total nitrogen loads in pastures having unobstructed and reduced flow. The phosphorus loads, on the otherhand, lowered in pastures with reduced flow compared to pastures with unobstructed flow.

Climate and litter quality are primary drivers of terrestrial decomposition and, based on evidence from multisite experiments at regional and global scales, are universally factored into global decomposition models. In contrast, soil animals are considered key regulators of decomposition at local scales but their role at larger scales is unresolved. Soil animals are consequently excluded from global models of organic mineralization processes. Incomplete assessment of the roles of soil animals stems from the difficulties of manipulating invertebrate animals experimentally across large geographic gradients. This is compounded by deficient or inconsistent taxonomy. We report a global decomposition experiment to assess the importance of soil animals in C mineralization, in which a common grass litter substrate was exposed to natural decomposition in either control or reduced animal treatments across 30 sites distributed from 43°S to 68°N on six continents. Animals in the mesofaunal size range were recovered from the litter by Tullgren extraction and identified to common specifications, mostly at the ordinal level. The design of the trials enabled faunal contribution to be evaluated against abiotic parameters between sites. Soil animals increase decomposition rates in temperate and wet tropical climates, but have neutral effects where temperature or moisture constrain biological activity. Our findings highlight that faunal influences on decomposition are dependent on prevailing climatic conditions. We conclude that (1) inclusion of soil animals will improve the predictive capabilities of region- or biome-scale decomposition models, (2) soil animal influences on decomposition are important at the regional scale when attempting to predict global change scenarios, and (3) the statistical relationship between decomposition rates and climate, at the global scale, is robust against changes in soil faunal abundance and diversity. [ABSTRACT FROM AUTHOR]

Abstract: Livestock significantly affect wetland soils and vegetation but their impacts on wetland nutrient dynamics are poorly understood. We set up a full factorial laboratory experiment to assess the effects of Juncus effusus, grazing exclusion, and flooding on P flux from intact cores collected from seasonal wetlands in cattle pastures in south Florida. We collected intact cores from Juncus tussocks and plant interspaces inside and outside 4-year grazing exclosures in five replicate wetlands. We incubated the cores for 50 days under continuous flooding or weekly 1-day flooding cycles and measured P concentrations in surface and pore water. Grazing exclosures had less Juncus (17%) and bare ground (2%) than adjacent grazed areas (Juncus, 48%; bare ground, 12%), but did not affect P fluxes. Initial fluxes of soluble reactive P (SRP) were much higher in cores with Juncus (242±153mgPm−2 day−1) than without Juncus (14±20mgPm−2 day−1). In weekly flooded cores P fluxes fell to 19.7±13.4mgPm−2 day−1 in cores with and 2.7±2.6 in cores without Juncus. The strong effect of Juncus on P flux was an indirect effect of cattle grazing, but 4 years of grazing exclusion did not have a significant effect on P fluxes. [Copyright &y& Elsevier]