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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]

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]

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]

The invasive Pomacea maculata (= Pomacea insularum) (Perry) (Island Apple Snail) is becoming increasingly abundant in the southeastern US with potentially detrimental effects on wetland vegetation and water quality. Here, we investigate the association of plant-community structure and aquatic-predator abundance with Island Apple Snail invasion in seasonal wetlands on a cattle ranch in south-central Florida. We found a negative correlation between Island Apple Snail abundance and abundance of its preferred forage species, raising concerns that the snail may have already altered plant communities in these seasonal wetlands. We also found a negative correlation between Island Apple Snail abundance in wetlands and distance to the nearest ditch. In a snail-growth experiment, we found a negative effect of species evenness and a positive effect of total vegetation cover on Island Apple Snail weight gain. To understand Island Apple Snail invasion success in seasonal wetlands, more research is needed on the relative importance of landscape- versus local-scale wetland characteristics and how resources such as preferred forage versus egg-laying sites affect snail-population growth. [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]