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Questions: Grasslands provide important provisioning services worldwide and their management has consequences for these services. Management intensification is a widespread land‐use change and has accelerated across North America to meet rising demands on productivity, yet its impact on the relationship between plant diversity and productivity is still unclear. Here, we investigated the relationship between plant diversity and grassland productivity across nine ecoclimatic domains of the continental United States. We also tested the effect of management intensification on diversity and productivity in four case studies. Methods: We acquired remotely sensed gross primary productivity data (GPP, 1986–2018) and plant diversity data measured at different spatial scales (1, 10, 100, 400 m2), as well as climate variables including the Palmer drought index from two ecological networks. We used general linear mixed models to relate GPP to plant diversity across sites. For the case study analysis, we used linear mixed models to relate plant diversity to management intensity, and tested if the management intensity influenced the relationship between GPP (mean and temporal variation) and drought. Results: Across all sites, we observed positive relationships among species richness, productivity, and the temporal stability of mean annual biomass production. These relationships were not affected by the scale at which species richness was observed. In three out of the four case studies, we observed that management effects on species richness were only significant at broader scales (i.e., ≥10 m2) with no clear effect found at the commonly used 1‐m2 quadrat scale. In one case study, species‐poor, intensively managed pastures presented the highest productivity but were more sensitive to dry conditions than less intensified pastures. However, in other case studies, we did not observe significant effects of management intensity on the magnitude or stability of productivity. Conclusions: Generalization across studies may be difficult and require the development of intensification indices general enough to be applied across diverse management strategies in grazilands. Understanding how management intensification affects grassland productivity will inform the development of sustainable intensification strategies. [ABSTRACT FROM AUTHOR]

Isolated, seasonal wetlands within agricultural landscapes are important ecosystems. However, they are currently experiencing direct and indirect effects of agricultural management surrounding them. Because wetlands provide important ecosystem services, it is crucial to determine how these factors affect ecological communities. Here, we studied the long‐term effects of land‐use intensification, cattle grazing, prescribed fires, and their interactions on wetland plant diversity, community dynamics, and functional diversity. To do this, we used vegetation and trait data from a 14‐year‐old experiment on 40 seasonal wetlands located within seminatural and intensively managed pastures in Florida. These wetlands were allocated different grazing and prescribed fire treatments (grazed vs. ungrazed, burned vs. unburned). Our results showed that wetlands within intensively managed pastures have lower native plant diversity, floristic quality, evenness, and higher nonnative species diversity and exhibited the most resource‐acquisitive traits. Wetlands embedded in intensively managed pastures were also characterized by lower species turnover over time. We found that 14 years of cattle exclusion reduced species diversity in both pasture management intensities and had no effect on floristic quality. Fenced wetlands exhibited lower functional diversity and experienced a higher rate of community change, both due to an increase in tall, clonal, and palatable grasses. The effects of prescribed fires were often dependent on grazing treatment. For instance, prescribed fires increased functional diversity in fenced wetlands but not in grazed wetlands. Our study suggests that cattle exclusion and prescribed fires are not enough to restore wetlands in intensively managed pastures and further highlights the importance of not converting seminatural pastures to intensively managed pastures. Our study also suggests that grazing levels applied in seminatural pastures maintained high plant diversity and prevented tree and shrub encroachment and that in the absence of grazing, prescribed fire became crucial to maintaining higher species evenness. [ABSTRACT FROM AUTHOR]

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 are an important source of CH4 globally. However, uncertainty surrounding the impact of anthropogenic activities on CH4 emissions from wetlands limits understanding of how these ecosystems will respond to management changes. Furthermore, by neglecting the potential for management to influence CH4 emissions likely inflates error of CH4 emissions for regional and global CH4 models. This study employed a replicated factorial experimental design to investigate how management of the agricultural landscape, including grazing and/or management intensity, influences net CH4 emissions from embedded, seasonal subtropical wetlands. This research further determined key mechanisms by which management decisions at the landscape scale modulate CH4 emissions from the embedded wetlands. Net CH4 exchange was measured using a closed chamber system over two complete wet/dry seasonal cycles in 16 wetlands embedded in either agronomically improved pastures (improved wetlands) or less intensively grazed unfertilized seminative pastures (seminative wetlands), as well as in grazed and ungrazed wetlands in each treatment. Emissions of CH4 were higher from improved wetlands (2.82 μmol m−2 s−1) than seminative wetlands (0.75 μmol m−2 s−1), particularly during the wet season. Enhanced CH4 emissions in improved wetlands relative to seminative wetlands were caused by increased soil wetness and by higher biomass in improved seminative wetlands. Unlike subtropical flooded pastures, our results showed that grazers do not alter CH4 emissions from subtropical wetlands. Current and future changes in management intensity of pastures may cause shifts in net soil CH4 emissions from embedded subtropical wetlands, which could further enhance this emission source. Key Points: Wetlands are methane sources, but little is known regarding how surrounding agricultural practices impact emissionsWetlands embedded in intensely managed pastures have higher methane emissions than wetlands surrounded by seminative landscapesWhether a wetland was grazed or ungrazed had no impact on the amount of methane released from the wetland [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]

Growing demand for food from finite agricultural lands requires the optimization of agricultural management, including the potential interactive effects of these practices on ecosystems. We experimentally examined the interactive and temporal effects of three ranching practices (pasture management intensity, livestock grazing, and prescribed fire) on soil nutrients in 40 geographically-isolated seasonal wetlands. Wetlands were embedded in a subtropical ranch, and the long-term experiment used a factorial design with wetlands as experimental units. Soils (0–15 cm) were collected three times over 9 years; at experiment start (2007), one year after prescribed burns started (2009), and seven years later (2016). Samples were analyzed for soil bulk density, organic matter (OM), total nitrogen (N), carbon (C), and phosphorous (P). A lag effect was observed in response to fire; differences were not observed in 2009, but were detected in 2016 after multiple fire cycles had occurred. Rangeland practices showed 2- and 3-way interactive effects, especially for total P and N stocks. Total P increased most in the wetlands embedded within highly managed, grazed, and burned pastures (2.31 ± 0.76 g m −2 yr −1 ), consistent with legacy effects of historical fertilizer application, cattle activity, and ash deposit due to fire. Wetlands in semi-natural and burned pastures had the lowest rates of soil N storage (5.13 ± 7.33 g m −2 yr −1 ) compared to all other treatments (24.5 ± 10.8 g m −2 yr −1 ). Total C stocks were not significantly impacted by ranching practices throughout the study. In summary, ranching practices can additively and interactively alter soil nutrient stocks after a time lag, and legacy effects of P application still impact wetlands decades later. Our study is one of few focused on ranchland wetlands and shows that wetlands in highly managed, grazed, and/or burned pastures can sequester soil P and N, playing an important role in nutrient processing for agricultural landscapes and watersheds. [ABSTRACT FROM AUTHOR]

Pasture management intensity, livestock grazing and prescribed fire are three widespread agricultural practices that affect small, isolated wetlands, but few studies have investigated their individual and interactive effects. Pasture management intensity refers to the degree of human alteration of grassland, ranging from intensively managed pastures planted with introduced forage, fertilizer/lime additions and artificial drainage to semi-natural pastures with mixed native and non-native vegetation, no fertilizer/lime additions and little or no artificial drainage., We examined individual and interactive effects of these three agricultural practices on individual, isolated wetlands using a replicated, full-factorial experiment on 40 entire wetlands in south Florida, USA. Wetlands were embedded in two pasture management intensities: intensively managed and semi-natural., After three years of treatment initiation, vegetation of wetlands released from grazing and unburned embedded in semi-natural pastures had significantly lower evenness and coefficient of conservatism scores compared to wetlands released from grazing and burned, grazed unburned wetlands and grazed burned wetlands in the same pasture management intensity. For wetlands embedded in intensively managed pastures, evenness and coefficient of conservatism scores did not differ among treatments., Release from grazing increased abundance of the native, weedy herb, Eupatorium capillifolium., Grazing interacted with prescribed fire to affect shrub abundance and non-native richness; relative abundance of shrubs and non-native richness were greater in wetlands released from grazing and burned and did not differ among burn treatments in grazed wetlands. Interactive effects, especially three-way interactions, were uncommon and not as important as differences between the two pasture management intensities., Synthesis and applications. Vegetation diversity and floristic quality of wetlands embedded in intensively managed pastures resisted common restoration management techniques such as release from grazing and prescribed fire, at least in the short term. In contrast, removing all top-down disturbances from wetlands embedded in semi-natural grasslands can negatively affect vegetation species diversity and floristic quality. Future studies should examine how intensity and seasonality of grazing and prescribed fire affect wetland vegetation, and track long-term responses to evaluate lag effects. [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 teabag index (TBI) was adopted to quantify subtropical wetland decomposition. • Land-use intensification, grazing, and fire interactively affected decomposition. • Hydrology and climate contributed to spatial–temporal variation in decomposition. • TBI is a useful indicator to inform wetland ecosystem service management. Understanding how global change drivers and their interactions affect decomposition in wetlands embedded in agricultural landscapes remains challenging, especially in tropical and subtropical biomes, which are disproportionately important for global carbon cycling yet with high uncertainties. In a long-term whole-ecosystem experiment, we used a widely-adopted indicator of decomposition, the Teabag Index (TBI), to investigate individual and interactive effects of surrounding land-use intensity, cattle grazing, and prescribed fire on seasonal wetland decomposition (i.e., decay rate k , and stabilization factor S) in an exemplar subtropical landscape in central-south Florida, USA. We ask: (1) How do land-use intensity and management practices affect the decomposition in seasonal wetlands? (2) How does wetland decomposition vary with hydrological gradient and seasonal climatic condition? (3) What are the dominant direct and indirect pathways through which land-use intensity and management practices affect wetland decomposition? Our results showed that, overall, surrounding land-use intensity exerted much stronger effects on litter decomposition compared to grazing and prescribed fire, and cattle grazing reduced decomposition rate k. There was a complex three-way interaction among land-use intensity, grazing and fire on the stabilization factor S – a proxy related to carbon sequestration potential. Grazing-fire interactive effects on S only existed in wetlands embedded in intensively-managed landscapes, where grazing reduced S in burned wetlands but did not affect S in unburned wetlands. Decay rate k showed profound temporal variation primarily driven by seasonal climatic conditions (especially precipitation), whereas S varied spatially along the hydrological gradient. Our structural equation modeling (SEM) analyses further revealed that effects on k were also indirectly manifested through changes on soil C/N, C/P, and pH, while effects on S were manifested through alterations in soil C/P ratio, pH, soil nutrients and water content. Our TBI results suggest that anthropogenic environmental changes, including land-use intensification, livestock introduction and fire suppression, could compromise carbon sequestration potential in tropical and subtropical seasonal wetlands. Our research highlights the importance of considering landscape context in wetland management and demonstrates the use of TBI as an indicator to quantify and inform combinations of land management and agricultural practices could conserve wetlands and sustain their vital functions and services, especially from the lens of promoting carbon storage and nutrient retention services. [ABSTRACT FROM AUTHOR]

• Phosphorus decreased within a year in highly altered wetlands with grazing and fire. • After a year, phosphorus and ammonia decreased in highly altered wetlands with fire. • After 6 years, only ammonia decreased with grazing removed and fire. • In a lab experiment, plants & detritus released phosphorus & nitrogen after burning. Small, isolated, depressional wetlands increasingly exist in developed landscapes and are highly vulnerable to hydrologic alterations and eutrophication. Globally, grazing lands contain a significant number of these wetlands, and the practices of grazing, prescribed fire and fertilizing have all been shown separately to influence wetland nutrient dynamics. However, wetlands are often exposed to a combination of these practices and the interactive effects have yet to be fully elucidated. The purpose of this study was to examine the effects of pasture management, grazing, and fire on water quality in isolated wetlands on a subtropical ranch in South-Central Florida. We used a factorial experiment on 40 whole wetland ecosystems manipulating grazing (fenced or not) and fire (burned or not) in two pasture types (intensely managed and semi-native). Grab samples of water were collected over 8 years, including one pre-treatment year, at peak growing season, in all wetlands and analyzed for nitrogen and phosphorous. In addition, we conducted a laboratory experiment to simulate the effect of a prescribed burn on water quality using live plant tissue, detritus, and soil taken from grazed and fenced wetlands to investigate the interactions of these practices on short-term responses of water quality. In the field experiment, after one year of experimental treatments, wetlands exposed to both grazing and prescribed burns had relatively low phosphorous in water in intensely managed pastures. After multiple years of treatment only ammonia was reduced with burning and fencing in both pasture-types. In the lab experiment, simulated burning caused a pulse release of phosphorous and a reduction of nitrogen due to volatilization of both live plant tissue and detritus, but the magnitude was influenced by grazing and pasture-type. This study of rangeland management on wetland water quality demonstrates the effect of these practices, especially prescribed burns, on improving nutrient release in agricultural wetlands and shows that management effects on nutrient release varies with historical land use and over time. [ABSTRACT FROM AUTHOR]

Bacteria and fungi are primary components in wetland soil microbial communities and provide essential ecosystem functions and services. Understanding responses of bacterial and fungal communities to multiple drivers of environmental change and their interactions is crucial for wetland conservation and management, particularly for those embedded in agricultural landscapes. Yet little is known about effect of agricultural land use and wetland management on soil microbial communities in subtropical seasonal wetlands. Here, we used a long-term whole-ecosystem wetland experiment to examine individual and interactive effects of upland land-use intensification, livestock grazing, and prescribed fire on soil bacteria and fungi. We asked: (1) How do land-use intensification, grazing and fire disturbances interact to alter taxonomic composition and functional potential of wetland soil bacterial and fungal communities? (2) To what extent would these management and disturbance effects on wetland microbial communities manifest through alterations in soil properties? Our results showed that both microbial taxonomic and functional composition are responsive to agricultural land use and wetland management. Upland land-use intensification was the strongest driver (as compared to fire and grazing) in shaping bacterial and fungal community composition. Specifically, land-use intensification increased functional richness of both bacteria and fungi, whereas grazing and fire only interactively affected bacterial functional richness. In addition, responses of bacterial and fungal species diversity to wetland management varied, where grazing and fire reduced fungal species diversity in wetlands embedded in low-intensity managed pastures, but none of these management practices altered bacterial species diversity. Further, we found that pH and secondary nutrients (i.e., Ca and Mg) availability were the most important soil properties that explain how agricultural land use and wetland management drive the composition of bacterial and fungal communities. Our findings suggest that integration of lime application into intensified land uses to neutralize soil pH could facilitate maintenance of microbial diversity and associated functions. Our results highlight the need to comprehensively assess management impacts on soil microorganisms, rather than using a single or few indicators, due to inconsistent responses of bacterial and fungal communities, as well as their varied taxonomic and functional responses. ● Agricultural land use and wetland management have either individual or interactive effects on soil microbial communities. ● Upland intensification exerts stronger effects on wetland soil microbial communities than grazing and fire. ● Fungal diversity is more responsive to land management than bacterial diversity. ● Agricultural management and disturbances can affect potential microbial functions in wetlands. [ABSTRACT FROM AUTHOR]