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Lake Placid, FL, United States

Bohlen P.J.,Macarthur Agro Ecology Research Center | Bohlen P.J.,University of Central Florida | Villapando O.R.,South Florida Water Management District
Journal of Environmental Quality | Year: 2011

A 4-yr (2005-2008) study was conducted to evaluate the potential of pasture water management for controlling nutrient losses in surface runoff in the Northern Everglades. Two pasture water management treatments were investigated on Bahia grass (Paspalum notatum Flüggé) pastures: reduced flow and unobstructed flow. The reduced flow treatment was applied to four of eight 20.23-ha pastures by installing water control structures in pasture drainage ditches with flashboards set at a predetermined height. Four other pastures received the unobstructed-flow treatment, in which surface runoff exited pastures unimpeded. Automated instruments measured runoff volume and collected surface water samples for nutrient analysis. In analyzing data for before-after treatment analysis, the 2005 results were removed because of structural failure in water control structures and the 2007 results were removed because of drought conditions. Pasture water retention significantly reduced annual total nitrogen (TN) loads, which were 11.28 kg ha-1 and 6.28 kg ha-1, respectively, in pastures with unobstructed and reduced flow. Total phosphorus (TP) loads were 27% lower in pastures with reduced flow than in pastures with unobstructed flow, but this diff erence was not statistically significant. Concentrations of available soil P were significantly greater in pastures with reduced flow. Pasture water retention appears to be an effective approach for reducing runoff volume and TN loads from cattle pastures in the Northern Everglades, but the potential to reduce TP loads may be diminished if higher water table conditions cause increased P release from soils, which could result in higher P concentration in surface runoff. © 2011 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. Source

Huang C.-Y.,University of Georgia | Hendrix P.F.,University of Georgia | Fahey T.J.,Cornell University | Bohlen P.J.,Macarthur Agro Ecology Research Center | Groffman P.M.,Cary Institute of Ecosystem Studies
Ecological Modelling | Year: 2010

Recent studies have reported that earthworm invasions alter native communities and impact nutrient cycling in terrestrial ecosystems. We developed a simulation model to evaluate the potential impacts of earthworm invasions on carbon dynamics, taking into consideration earthworm feeding strategies and priming effects on the microorganisms through their casting activities. Responses of carbon stocks (forest litter, soil organic matter, microbial biomass and earthworm populations) and carbon fluxes (litter decomposition, earthworm consumption, and microbial respiration) were used to evaluate an earthworm invasion of a forest ecosystem. Data from a northern temperate forest (Arnot Forest, New York) were adapted for model calibration and evaluation. Simulation results suggest that the impact and outcome of earthworm invasions are affected by pre-invasion resource availability (litter and soil organic matter), invasive earthworm assemblages (particularly feeding strategy), and invasion history (associated with earthworm population dynamics). The abovementioned factors may also determine invasion progress of earthworm species. The accuracy of the model could be improved by the addition of environmental modules (e.g., soil water regimes), precise parameters accounting for individual species attributes under different environmental conditions (e.g. utilization ability of different types of food resources), as well as earthworm population dynamics (size and structure) and interactions with predators and other invasive/indigenous species during the invasion progress. Such an earthworm invasion model could provide valuable evaluation of the complicated responses of carbon dynamics to earthworm invasions in a range of forest ecosystems, particularly under global change scenarios. © 2010 Elsevier B.V. Source

Chamberlain S.D.,Cornell University | Boughton E.H.,Macarthur Agro Ecology Research Center | Sparks J.P.,Cornell University
Ecosystems | Year: 2015

Cattle are a major methane (CH4) source from pasture ecosystems; however, the underlying landscape can be a significant and unaccounted source of CH4. In general, landscape CH4 emissions are poorly quantified, vary widely across time and space, and are easily underestimated if emission hotspots or episodic fluxes are overlooked. In this study, CH4 emissions from subtropical lowland pastures were quantified using static chambers, eddy covariance, and mobile spectrometer surveys. Landscape emissions were the dominant CH4 source, and cattle were responsible for 19–30% of annual emissions. The entire ecosystem emitted 33.84 ± 2.25 g CH4 m−2 y−1 as estimated by eddy covariance-measured fluxes. Landscape emissions were highly variable, and seasonal flooding drove high magnitude emissions from the underlying landscape. Large CH4 emissions were observed from wetlands and, to a lesser extent, from the entire landscape during the wet season. In contrast, during the dry season, there were no appreciable landscape CH4 emissions, although canals, which cover only 1.7% of the total land area, were responsible for 97.7% of dry-season emissions. Ecosystem CH4 fluxes, measured by eddy covariance, varied seasonally and positively correlated to water table depth, soil and air temperatures, and topsoil water content. The results presented here are the first to use mobile spectrometers to map biogenic CH4 emissions at the landscape scale, and strongly suggest that the underlying landscape is a strong CH4 source that must be considered in addition to cattle emissions. © 2015, Springer Science+Business Media New York. Source

Boughton E.H.,University of Central Florida | Quintana-Ascencio P.F.,University of Central Florida | Nickerson D.,University of Central Florida | Bohlen P.J.,Macarthur Agro Ecology Research Center
Applied Vegetation Science | Year: 2011

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-m 2 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-m 2 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, C 3 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 C 3 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. © 2011 International Association for Vegetation Science. Source

Boughton E.H.,Macarthur Agro Ecology Research Center | Boughton R.K.,University of Florida
Biological Invasions | Year: 2014

At the landscape scale, ecosystem engineers are expected to increase species diversity; however, diversity could decline if the ecosystem engineer is over-abundant. Thus, invasive ecosystem engineers are expected to have strong impacts, due to their high abundances and novel disturbances. An invasive ecosystem engineer, the feral swine (Sus scrofa), is a species that creates intense soil disturbances, altering soil and plant communities. In this study, we examine the effects of this invasive ecosystem engineer on experimental plant plots that had been protected for over a decade. Feral swine avoided recently burned plots and preferred plots with N addition. Rooted plots shifted from a bunchgrass dominated wet prairie to a monotypic stand of the native, Lachnanthes caroliana. Feral swine were also attracted to plots with existing patches of L. caroliana suggesting a potential positive feedback between swine activity and L. caroliana patch expansion that could result in an alternative state. © 2014, Springer International Publishing Switzerland. Source

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