Browsing by Subject "grassland"

Now showing 1 - 4 of 4
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    Consequences of nutrient enrichment for soil organic matter cycling in grasslands
    (2015-07) Riggs, Charlotte
    Human activities have increased the availability of nutrients, such as nitrogen (N), phosphorus (P), and potassium (K), worldwide. Since alterations to nutrient cycles influence carbon (C) fixation and decomposition processes, nutrient enrichment affects global C stocks -- such as soil C. Carbon in soil organic matter (SOM) far outweighs vegetative C in the majority of biomes, especially grasslands. Consequently, either positive or negative changes to grassland soil C sequestration could feed back to influence the global C cycle. Unfortunately, the effects of nutrient enrichment on SOM cycling remain uncertain. In my dissertation, I examined the effects of nutrient addition on SOM cycling at participatory sites of the Nutrient Network -- a coordinated, global network of nutrient addition experiments that follow standard protocols for sampling and analysis. I found that the total soil C stock at experimental grasslands worldwide increased in response to the addition of N, P, and K. Furthermore, in a regional study in the US Central Great Plains, I found that N addition decreased microbial decomposition of SOM and tended to increase soil aggregation. Finally, in a laboratory study I found that decreased microbial biomass likely explains the decreased microbial decomposition of SOM in response to N addition. Overall, my results suggest that nutrient enrichment will lead to increased sequestration of soil C in some grassland soils.
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    Data and R Code for Analyses in "Grassland birds demonstrate delayed response to large-scale tree removal in central North America"
    (2015-09-30) Thompson, Sarah, J; thom1253@umn.edu; Thompson, Sarah, J
    These files contain R code and data required for analsyes detailed within "Grassland birds demonstrate delayed response to large-scale tree removal in central North America" in the Journal of Applied Ecology. The lead author wrote this code to analyze multi-year point count data collected in west-central Minnesota. The purpose of the study was to assess the success of habitat restoration activities aimed at removal of encroaching trees and shrubs.
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    Data for fire regime shapes butterfly communities through changes in nectar resources in an Australian tropical savanna, 2019-2020
    (2023-08-03) Leone, Julia B; Larson, Diane L; Richards, Anna E; Schatz, Jon; Andersen, Alan N; jleone@fmr.org; Leone, Julia B
    We studied responses of butterflies, vegetation structure, and floral resources to fire regime at a long-term fire experiment near Darwin in the Australian tropical savanna. This dataset consists of data collected during the 2019/2020 wet season at 18 1-ha plots in three blocks, where each block contains six randomly assigned fire treatments. We measured butterfly, vegetation structure, and floral resources data, and collected fire regime data. These data are associated with Leone et al. (2023). Fire regime shapes butterfly communities through changes in nectar resources in an Australian tropical savanna. Ecosphere. Along with its associated paper, we hope these data will provide helpful information for those working in fire management, butterfly conservation, and biodiversity conservation more broadly.
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    Plant diversity, CO2 and N influence inorganic and organic N leaching in grasslands
    (2007) Dijkstra, Feike A; West, Jason B; Hobbie, Sarah E; Reich, Peter B; Trost, Jared
    In nitrogen (N)-limited systems, the potential to sequester carbon depends on the balance between N inputs and losses as well as on how efficiently N is used, yet little is known about responses of these processes to changes in plant species richness, atmospheric CO2 concentration ([CO2]), and N deposition. We examined how plant species richness (1 or 16 species), elevated [CO2] (ambient or 560 ppm), and inorganic N addition (0 or 4 g·m−2·yr−1) affected ecosystem N losses, specifically leaching of dissolved inorganic N (DIN) and organic N (DON) in a grassland field experiment in Minnesota, USA. We observed greater DIN leaching below 60 cm soil depth in the monoculture plots (on average 1.8 and 3.1 g N·m−2·yr−1 for ambient N and N-fertilized plots respectively) than in the 16-species plots (0.2 g N·m−2·yr−1 for both ambient N and N-fertilized plots), particularly when inorganic N was added. Most likely, loss of complementary resource use and reduced biological N demand in the monoculture plots caused the increase in DIN leaching relative to the high-diversity plots. Elevated [CO2] reduced DIN concentrations under conditions when DIN concentrations were high (i.e., in N-fertilized and monoculture plots). Contrary to the results for DIN, DON leaching was greater in the 16-species plots than in the monoculture plots (on average 0.4 g N·m−2·yr−1 in 16-species plots and 0.2 g N·m−2·yr−1 in monoculture plots). In fact, DON dominated N leaching in the 16-species plots (64% of total N leaching as DON), suggesting that, even with high biological demand for N, substantial amounts of N can be lost as DON. We found no significant main effects of elevated [CO2] on DIN or DON leaching; however, elevated [CO2] reduced the positive effect of inorganic N addition on DON leaching, especially during the second year of observation. Our results suggest that plant species richness, elevated [CO2], and N deposition alter DIN loss primarily through changes in biological N demand. DON losses can be as large as DIN loss but are more sensitive to organic matter production and turnover.