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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]

Biodiversity impacts are rarely included in systems analyses of livestock production. We piloted two approaches toward quantifying biodiversity impacts, pressure‐state‐response (PSR) and potential species loss (PSL), at a cow–calf operation in Florida for which extensive environmental data were available. Using these approaches, we compared livestock production on two vegetation types, semi‐native pasture (SNP) and improved pasture (IMP), and we found fewer deleterious effects on biodiversity associated with SNP (characterized by low stocking rates and no fertilizer) than with IMP, as evidenced by a lower PSL and greater biotic integrity under PSR. Both approaches agreed in the direction of the outcome, but we argue that, when possible, they should be applied complementarily to inform both absolute and per‐unit product biodiversity impacts of livestock production. This research demonstrates how to incorporate biodiversity into life‐cycle perspectives of livestock sustainability assessments when data availability varies, supporting the expansion of multi‐metric, holistic evaluations that are absent from most livestock system analyses. [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]

Evapotranspiration (ET) constitutes the largest loss of water from subtropical grassland and wetland ecosystems, yet data in much of the world have high uncertainty at the landscape scale as there is little information on plant water use. Additionally, anthropogenic alterations to grasslands are a major threat globally and alter ecosystem water use, but the impact of these changes is often unquantified. A major reason for this is the complexity and expense of field‐based ET quantification methods such as agricultural lysimeters and eddy covariance systems. Accurate measurements of ET are critical for sustainable water management. This study developed two different low‐cost lysimeters—weighing‐type and water level‐based, to measure ET under partly controlled conditions for single species as well as mixed grassland and wetland communities. Lysimeters were placed in an open‐sided, transparent‐roofed shadehouse and watered periodically. ET values were then compared with (i) actual ET from an eddy covariance tower onsite, (ii) vapour transport‐based reference ET models (FAO Penman–Monteith, modified Turc and Abtew simple radiation models), and (iii) reference ET data customized for vegetation types from the Florida Automated Weather Network (FAWN). Both weighing‐type and water level lysimeters yielded seasonal patterns and annual magnitudes similar to other ET methods. Annual ET measurements from single‐species weighing‐type lysimeters (ranging from 881 to 1278 mm for four plant species, n = 5 per species, 20 in total) and water level lysimeters (1085 ± 306 mm, plant community average, n = 31) were about 10–20% lower than reference ET models (~1300 mm) and similar to FAWN data (1050 mm). Actual ET from eddy covariance was 722 mm for 10 months (missing data for February and March), while weighing lysimeter measurements for the dominant grass Paspalum notatum was 885 mm for the same 10 months. While rainfall exclusion and watering can result in ET differing from actual field conditions, low‐cost lysimeters can provide an independent measure of ET for comparison with regional ET models/remote sensing data lacking field validation. Thereby, low‐cost lysimeters are potentially useful for water resources and ecosystem management in data‐poor regions of the world. [ABSTRACT FROM AUTHOR]

Biotic and abiotic factors interact with dominant plants—the locally most frequent or with the largest coverage—and nondominant plants differently, partially because dominant plants modify the environment where nondominant plants grow. For instance, if dominant plants compete strongly, they will deplete most resources, forcing nondominant plants into a narrower niche space. Conversely, if dominant plants are constrained by the environment, they might not exhaust available resources but instead may ameliorate environmental stressors that usually limit nondominants. Hence, the nature of interactions among nondominant species could be modified by dominant species. Furthermore, these differences could translate into a disparity in the phylogenetic relatedness among dominants compared to the relatedness among nondominants. By estimating phylogenetic dispersion in 78 grasslands across five continents, we found that dominant species were clustered (e.g., co‐dominant grasses), suggesting dominant species are likely organized by environmental filtering, and that nondominant species were either randomly assembled or overdispersed. Traits showed similar trends for those sites (<50%) with sufficient trait data. Furthermore, several lineages scattered in the phylogeny had more nondominant species than expected at random, suggesting that traits common in nondominants are phylogenetically conserved and have evolved multiple times. We also explored environmental drivers of the dominant/nondominant disparity. We found different assembly patterns for dominants and nondominants, consistent with asymmetries in assembly mechanisms. Among the different postulated mechanisms, our results suggest two complementary hypotheses seldom explored: (1) Nondominant species include lineages adapted to thrive in the environment generated by dominant species. (2) Even when dominant species reduce resources to nondominant ones, dominant species could have a stronger positive effect on some nondominants by ameliorating environmental stressors affecting them, than by depleting resources and increasing the environmental stress to those nondominants. These results show that the dominant/nondominant asymmetry has ecological and evolutionary consequences fundamental to understand plant communities. [ABSTRACT FROM AUTHOR]

Fertilisation experiments have demonstrated that nutrient availability is a key determinant of biomass production and carbon sequestration in grasslands. However, the influence of nutrients in explaining spatial variation in grassland biomass production has rarely been assessed. Using a global dataset comprising 72 sites on six continents, we investigated which of 16 soil factors that shape nutrient availability associate most strongly with variation in grassland aboveground biomass. Climate and N deposition were also considered. Based on theory‐driven structural equation modelling, we found that soil micronutrients (particularly Zn and Fe) were important predictors of biomass and, together with soil physicochemical properties and C:N, they explained more unique variation (32%) than climate and N deposition (24%). However, the association between micronutrients and biomass was absent in grasslands limited by NP. These results highlight soil properties as key predictors of global grassland biomass production and point to serial co‐limitation by NP and micronutrients. [ABSTRACT FROM AUTHOR]

Increasing demand for agricultural products is driving grassland management intensification with subsequent impacts on ecosystem services and disservices. Key questions related to grassland production as well as environmental and social concerns must be addressed to ensure sustainability. We propose a unified perspective, addressing numerous trade‐offs and synergies between grassland ecosystem services and disservices, and considering an array of ecological and human consequences associated with history and ongoing shifts in management strategies. Much of our discussion utilizes evidence from humid grasslands; however, our examples and recommendations have global implications for the future of grassland management. We characterize four categories of ecosystem services and disservices (provisioning, supporting, regulating, and cultural) provided by perennial grasslands that are extensively managed (low or no input, never cultivated) or intensively managed (high‐input, cultivated). We explore a range of potential outcomes following transition from extensive to intensive agroecosystems around the globe. Additionally, we suggest specific research priorities to better evaluate ecosystem services and disservices across management intensities. Finally, we highlight potential benefits of landscape mosaics that include grasslands across a continuum of extensive to intensive strategies. [ABSTRACT FROM AUTHOR]

The effects of altered nutrient supplies and herbivore density on species diversity vary with spatial scale, because coexistence mechanisms are scale dependent. This scale dependence may alter the shape of the species–area relationship (SAR), which can be described by changes in species richness (S) as a power function of the sample area (A): S = cAz, where c and z are constants. We analysed the effects of experimental manipulations of nutrient supply and herbivore density on species richness across a range of scales (0.01–75 m2) at 30 grasslands in 10 countries. We found that nutrient addition reduced the number of species that could co‐occur locally, indicated by the SAR intercepts (log c), but did not affect the SAR slopes (z). As a result, proportional species loss due to nutrient enrichment was largely unchanged across sampling scales, whereas total species loss increased over threefold across our range of sampling scales. [ABSTRACT FROM AUTHOR]

Global change is impacting plant community composition, but the mechanisms underlying these changes are unclear. Using a dataset of 58 global change experiments, we tested the five fundamental mechanisms of community change: changes in evenness and richness, reordering, species gains and losses. We found 71% of communities were impacted by global change treatments, and 88% of communities that were exposed to two or more global change drivers were impacted. Further, all mechanisms of change were equally likely to be affected by global change treatments—species losses and changes in richness were just as common as species gains and reordering. We also found no evidence of a progression of community changes, for example, reordering and changes in evenness did not precede species gains and losses. We demonstrate that all processes underlying plant community composition changes are equally affected by treatments and often occur simultaneously, necessitating a wholistic approach to quantifying community changes. [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]

Within the greater food system, LTAR work is focused on food production (although LTAR scientists also seek to understand how sustainable agroecosystems interact with all food system components), and future directions will include life-cycle assessments. Agriculture also faces increasing demands from growing populations, rising wealth, and concomitant changes in food preferences that impact the entire food system, from food production to food and waste distribution (Ramankutty I et al i . 2018). Interwoven into society as a source of food, nutrition, livelihoods, and monetary resources, agriculture shapes and depends on the environment. [Extracted from the article]

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]

The article presents a study which examined the environmental drivers affecting carbon dioxide (CO2) and methane (CH4) fluxes in temporary flooded subtropical wetlands. Also cited are the relationship between gross primary productivity (GPP) with radiation and temperature, the reasons behind soil inundation, and the role of subtropical and tropical wetlands in the global carbon (C) cycle.

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]

Abstract: The impact of grazing on C fluxes from pastures in subtropical and tropical regions and on the environment is uncertain, although these systems account for a substantial portion of global C storage. We investigated how cattle grazing influences net ecosystem CO2 and CH4 exchange in subtropical pastures using the eddy covariance technique. Measurements were made over several wet‐dry seasonal cycles in a grazed pasture, and in an adjacent pasture during the first three years of grazer exclusion. Grazing increased soil wetness but did not affect soil temperature. By removing aboveground biomass, grazing decreased ecosystem respiration (Reco) and gross primary productivity (GPP). As the decrease in Reco was larger than the reduction in GPP, grazing consistently increased the net CO2 sink strength of subtropical pastures (55, 219 and 187 more C/m2 in 2013, 2014, and 2015). Enteric ruminant fermentation and increased soil wetness due to grazers, increased total net ecosystem CH4 emissions in grazed relative to ungrazed pasture (27–80%). Unlike temperate, arid, and semiarid pastures, where differences in CH4 emissions between grazed and ungrazed pastures are mainly driven by enteric ruminant fermentation, our results showed that the effect of grazing on soil CH4 emissions can be greater than CH4 produced by cattle. Thus, our results suggest that the interactions between grazers and soil hydrology affecting soil CH4 emissions play an important role in determining the environmental impacts of this management practice in a subtropical pasture. Although grazing increased total net ecosystem CH4 emissions and removed aboveground biomass, it increased the net storage of C and decreased the global warming potential associated with C fluxes of pasture by increasing its net CO2 sink strength. [ABSTRACT FROM AUTHOR]

Temporal stability of ecosystem functioning increases the predictability and reliability of ecosystem services, and understanding the drivers of stability across spatial scales is important for land management and policy decisions. We used species-level abundance data from 62 plant communities across five continents to assess mechanisms of temporal stability across spatial scales. We assessed how asynchrony (i.e. different units responding dissimilarly through time) of species and local communities stabilised metacommunity ecosystem function. Asynchrony of species increased stability of local communities, and asynchrony among local communities enhanced metacommunity stability by a wide range of magnitudes (1-315%); this range was positively correlated with the size of the metacommunity. Additionally, asynchronous responses among local communities were linked with species' populations fluctuating asynchronously across space, perhaps stemming from physical and/or competitive differences among local communities. Accordingly, we suggest spatial heterogeneity should be a major focus for maintaining the stability of ecosystem services at larger spatial scales. [ABSTRACT FROM AUTHOR]

Soil carbon sequestration in agroecosystems could play a key role in climate change mitigation but will require accurate predictions of soil organic carbon ( SOC) stocks over spatial scales relevant to land management. Spatial variation in underlying drivers of SOC, such as plant productivity and soil mineralogy, complicates these predictions. Recent advances in the availability of remotely sensed data make it practical to generate multidecadal time series of vegetation indices with high spatial resolution and coverage. However, the utility of such data largely is unknown, only having been tested with shorter (e.g., 1-2 yr) data summaries. Across a 2,000 ha subtropical grassland, we found that a long time series (28 yr) of a vegetation index (Enhanced Vegetation Index; EVI) derived from the Landsat 5 satellite significantly enhanced prediction of spatially varying SOC pools, while a short summary (2 yr) was an ineffective predictor. EVI was the best predictor for surface SOC (0-5 cm depth) and total measured SOC stocks (0-15 cm). The optimum models for SOC in the upper soil layer combined EVI records with elevation and calcium concentration, while deeper SOC was more strongly associated with calcium availability. We demonstrate how data from the open access Landsat archive can predict SOC stocks, a key ecosystem metric, and illustrate the rich variety of analytical approaches that can be applied to long time series of remotely sensed greenness. Overall, our results showed that SOC pools were closely coupled to EVI in this ecosystem, demonstrating that maintenance of higher average green leaf area is correlated with higher SOC. The strong associations of vegetation greenness and calcium concentration with SOC suggest that the ability to sequester additional SOC likely will rely on strategic management of pasture vegetation and soil fertility. [ABSTRACT FROM AUTHOR]

Pastures are an extensive land cover type; however, patterns in pasture greenhouse gas ( GHG) exchange vary widely depending on climate and land management. Understanding this variation is important, as pastures may be a net GHG source or sink depending on these factors. We quantified carbon dioxide ( CO2) and methane ( CH4) fluxes from subtropical pastures in south Florida for three wet-dry seasonal cycles using eddy covariance, and estimated two annual budgets of CO2, CH4, and GHG equivalent emissions. We also estimated the impact of water retention practices on pasture GHG emissions and assessed the impact of these emissions on stakeholder payments for water retention services in a carbon market framework. The pastures were net CO2 sinks sequestering up to 163 ± 54 g CO2-C·m−2·yr−1 (mean ± 95% CI), but were also strong CH4 sources emitting up to 23.5 ± 2.1 g CH4-C·m−2·yr−1. Accounting for the increased global warming potential of CH4, the pastures were strong net GHG sources emitting up to 584 ± 78 g CO2-C eq.·m−2·yr−1, and all CO2 uptake was offset by wet season CH4 emissions from the flooded landscape. Our analysis suggests that CH4 emissions due to increased flooding from water management practices is a small component of the pasture GHG budget, and water retention likely contributes 2-11% of net pasture GHG emissions. These emissions could reduce water retention payments by up to ~12% if stakeholders were required to pay for current GHG emissions in a carbon market. It would require at least 93.7 kg CH4-C emissions per acre-foot water storage (1 acre-foot = 1233.48 m3) for carbon market costs to exceed water retention payments, and this scenario is highly unlikely as we estimate current practices are responsible for 11.3 ± 7.2 kg CH4-C emissions per acre-foot of water storage. Our results demonstrate that water retention practices aimed at reducing nutrient loading to the Everglades are likely only responsible for a minor increase in pasture GHG emissions and would have a small economic consequence in a carbon market. [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]

Summary 1. Plant-plant interactions fluctuate between competition and facilitation depending upon ecological conditions and species traits. Facilitative interactions are expected to increase in frequency via associational defences with increasing consumer pressure. The ability of species to cope with competition and/or ecological stressors may alter the outcome of plant-plant interactions. 2. We conducted a transplant experiment to determine if native and non-native grasses and forbs respond similarly to interactions with Juncus effusus L., an unpalatable benefactor species, along a grazing intensity gradient in two contrasting pasture types: intensively managed and semi-natural. We expected competitive taller, erect species (grasses) and non-natives to obtain stronger facilitative effects than shorter, sprawling species (forbs) and natives. 3. We transplanted two species each of grasses and forbs, including one native and one non-native species of each, into 1-m2 grazed plots or exclosure plots either with or without Juncus in wetlands experiencing a range of grazing intensities across the two pasture types. 4. Interactions with Juncus varied from facilitation in grazed plots to competition in exclosures for the two grasses and the non-native forb. Juncus did not facilitate the native forb in grazed conditions. Grazing negatively influenced all species. For the grasses, facilitation intensity increased as grazing intensity increased, while facilitation intensity for forbs was unrelated to grazing intensity. 5. Synthesis. Facilitation intensity of a dominant macrophyte increased with consumer pressure for tall grasses in productive subtropical wetlands. These findings suggest that facilitation can allow native and non-native species to pass through human-induced ecological filters, such as cattle grazing, with implications for understanding forces governing community composition in disturbed environments. [ABSTRACT FROM AUTHOR]

Question: Does management intensity affect the association between non-native and native species and between non-native species and soil nutrients in wetlands? Location: MacArthur Agro-Ecology Research Center, Florida, USA. Methods: We evaluated native and non-native plant richness and relative frequency in 15 1-m2 plots in 40 wetlands across two types of pastures, highly managed (fertilized, ditched, planted, heavily grazed by cattle) and semi-natural (unfertilized, lightly seasonally grazed). Plant biomass was collected in five 0.25-m2 plots per wetland and sorted to species. Soil cores were collected to analyse soil total nitrogen (N) and phosphorus (P). An information-theoretic approach was used to compare mixed effects models considering the association of non-native richness, relative frequency, and biomass with native richness, relative frequency, biomass, C3 grass relative frequency (a dominant native group), N, P and wetland-type. Results: Non-native richness was negatively correlated with native richness in semi-natural wetlands, but there was no evidence of an association between these variables in highly managed wetlands. Non-native richness increased with increasing soil N in semi-natural wetlands, but not in the highly managed wetlands. Soil P was positively related to non-native frequency in semi-natural wetlands but negatively related in highly managed wetlands. Non-native frequency and biomass were negatively related to relative frequency of C3 grasses in both management types. Conclusions: Our results indicate that management intensity influences relationships between native and non-native richness. Management intensity interacts with abiotic or biotic factors, such as soil nutrients and composition, in predicting where non-native species will most likely need control. [ABSTRACT FROM AUTHOR]

Different management regimes imposed on similar habitat types provide opportunities to investigate mechanisms driving community assembly and changes in species composition. We investigated the effect of pasture management on vegetation composition in wetlands with varying spatial isolation on a Florida cattle ranch. We hypothesized that increased pasture management intensity would dampen the expected negative effect of wetland isolation on native species richness due to a change from dispersal-driven community assembly to niche-driven assembly by accentuated environmental tolerance. We used native plant richness, exotic plant richness and mean coefficient of conservatism (CC) to assess wetland plant assemblage composition. Sixty wetlands were sampled, stratified by three levels of isolation across two pasture management intensities; semi-native (less intensely managed; mostly native grasses, never fertilized) and agronomically improved (intensely managed, planted with exotic grasses, and fertilized). Improved pasture wetlands had lower native richness and CC scores, and greater total soil phosphorus and exotic species coverage compared to semi-native pasture wetlands. Increased wetland isolation was significantly associated with decreases in native species richness in semi-native pasture wetlands but not in improved pasture wetlands. Additionally, the species–area relationship was stronger in wetlands in improved pastures than semi-native pastures. Our results indicate that a) native species switch from dispersal-based community assembly in semi-native pastures to a species-sorting process in improved pastures, and b) recently-introduced exotic species already sorted for more intensive management conditions are primarily undergoing dispersal-based community assembly. That land-use may alter the relative importance of assembly processes and that different processes drive native and exotic richness has implications for both ecosystem management and restoration planning. [ABSTRACT FROM AUTHOR]

Increasingly, agriculture is recognized as valuable not only for food production, but also for regulating and supporting ecosystem services such as those encompassing biodiversity and water. Various government programs provide incentives to farmers and ranchers to maintain ecosystem services, with an emerging focus on payment‐for‐ecosystem services (PES) programs. However, interactions among ecosystem services, including synergies or trade‐offs, at spatial scales relevant to land managers are not well understood. Here, we examined how a PES program for enhanced water retention on subtropical ranchlands in the headwaters of the Everglades affected seven indicators of ecosystem services and three indicators of disservices within wetlands (local scale) and among wetlands (wetland scale) at four different ranches. We used general linear mixed models and model selection to evaluate the feasibility of explicit, a priori hypotheses using data from 15 wetlands sampled across four participating ranches. Our study indicated that managing for increased water retention could result in both synergies and trade‐offs among ecosystem services. Higher water retention increased wetland plants at both local and wetland scales and was associated with reduced mosquitoes. Trade‐offs included significant declines in forage plant cover and decreases in amphibian abundance with higher water retention. Unimodal non‐linear relationships described responses of macroinvertebrates, fish, mosquito, and non‐native plant abundance to increasing water retention. These complex relationships indicate that optimizing water retention, provisioning services, and wetland biodiversity in ranchlands may not be straightforward. Unimodal non‐linear relationships among water retention and biodiversity suggest there is a threshold of water retention that represents a trade‐off for also maintaining biodiversity. Land use was an important driver of ecosystem disservices, with more intensely managed ranches having a greater potential for ecosystem disservices such as increased cover of non‐native plants, abundant mosquitoes, and lower amphibian abundance. Multidisciplinary collaboration was required to design, implement, monitor, and assess this PES program for trade‐offs and synergies. [ABSTRACT FROM AUTHOR]