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  • 1
    ISSN: 1432-0789
    Keywords: Key words Snails ; Nitrogen ; Desert ; Mineralization ; Nitrification ; Respiration ; Feces ; N cycling processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Snail grazing and feces production have been shown to be major components of the nitrogen (N) budget of Negev Desert ecosystems. However, the movement of N from feces into soil N cycling processes has not been studied. In this study, we measured immediate N release from different types of snail feces following wetting of dry desert soils, and characterized potential net N mineralization and nitrification and soil respiration over a 12-day incubation under laboratory conditions. The dynamics of inorganic N exhibited two distinct phases during the 12-day incubation: (1) immediate release of inorganic N following wetting of the soil and (2) decline of inorganic N from day 1 to day 12 of the incubation. The immediate pulse of N release from this one wetting event (6–25 mg N m–2) was larger than annual atmospheric inputs of N to Negev Desert ecosystems (〈2 mg N m–2); however, from 50 to 80% of the N released upon wetting was consumed by the end of the incubation. There were differences in inorganic N release and respiration from feces from different kinds of snails, and from feces from the same species of snail fed different plants. The results suggest that while snail feces contribute significant amounts of plant available N to Negev ecosystems, plants must compete with other “sinks” for this N.
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  • 2
    ISSN: 1432-0789
    Keywords: Snails ; Nitrogen ; Desert ; Mineralization ; Nitrification ; Respiration ; Feces ; N cycling processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Snail grazing and feces production have been shown to be major components of the nitrogen (N) budget of Negev Desert ecosystems. However, the movement of N from feces into soil N cycling processes has not been studied. In this study, we measured immediate N release from different types of snail feces following wetting of dry desert soils, and characterized potential net N mineralization and nitrification and soil respiration over a 12-day incubation under laboratory conditions. The dynamics of morganic N exhibited two distinct phases during the 12-day incubation: (1) immediate release of inorganic N following wetting of the soil and (2) decline of inorganic N from day 1 today 12 of the incubation. The immediate pulse of N release from this one wetting event (6–25 mg N m-2) was larger than annual atmospheric inputs of N to Negev Desert ecosystems (〈2 mg N m-2); however, from 50 to 80% of the N released upon wetting was consumed by the end of the incubation. There were differences in inorganic N release and respiration from feces from different kinds of snails, and from feces from the same species of snail fed different plants. The results suggest that while snail feces contribute significant amounts of plant available N to Negev ecosystems, plants must compete with other “sinks” for this N.
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  • 3
    ISSN: 1432-0789
    Keywords: 2,4-D ; Dicamba ; Microbial biomass Wetland ; Forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A study was conducted to evaluate relationships between microbial biomass and the dissipation of 2,4-D (2,4-dichlorophenoxy acetic acid) and dicamba (2-methoxy-3,6-dichlorobenzoic acid) in soil. We hypothesized that the size of the microbial biomass should be a strong predictor of the pesticide degradation capacity of a particular soil. Soils with a high microbial biomass should have relatively high levels of general microbial activity and should support a diversity of degradation pathways. In this study, we quantified the degradation of 2,4-D and dicamba in a range of soils with different concentrations of microbial biomass. The herbicides 2,4-D and dicamba were added to similar soils collected from five different land use types (home lawn, cornfield, upland hardwood forest, wetland forest, and aquifer material) and incubated for 80 days under laboratory conditions. Herbicide residue and microbial biomass (C and N) analyses were performed 5, 10, 20, 40, and 80 days following herbicide application. Microbial biomass-C and -N and soil organic matter content were positively correlated with dissipation of 2,4-D and dicamba. The results suggest that there are relationships between the size of the soil microbial biomass and the herbicide degradation capacity of an ecosystem. These relationships may be useful for developing approaches for evaluating and predicting the fate of pesticides in different ecosystems.
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  • 4
    ISSN: 1432-0789
    Keywords: Key words Carbon ; Nitrogen ; Microbial biomass ; Mineralization ; Respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The effects of acetate additions to northern hardwood forest soils on microbial biomass carbon (C) and nitrogen (N) content, soil inorganic N levels, respirable C and potential net N mineralization and nitrification were evaluated. The experiment was relevant to a potential watershed-scale calcium (Ca) addition that aims to replace Ca depleted by long-term exposure to acid rain. One option for this addition is to use calcium-magnesium (Mg) acetate, a compound that is inexpensive and much more readily soluble than the Ca carbonate that is generally used for large-scale liming. Field plots were treated with sodium (NA) acetate, Na bicarbonate or water (control) and were sampled (forest floor – Oe and Oa combined) 2, 10 and 58 days following application. It was expected that the addition of C would lead to an increase in biomass C and N and a decrease in inorganic N. Instead, we observed no effect on biomass C, a decline in biomass N and an increase in N availability. One possible explanation for our surprising results is that the C addition stimulated microbial activity but not growth. A second, and more likely, explanation for our results is that the C addition did stimulate microbial growth and activity, but there was no increase in microbial biomass due to predation of the new biomass by soil fauna. The results confirm the emerging realization that the effects of increases in the flow of C to soils, either by deliberate addition or from changes in atmospheric CO2, are more complex than would be expected from a simple C : N ratio analysis. Evaluations of large-scale manipulations of forest soils to ameliorate effects of atmospheric deposition or to dispose of wastes should consider microbial and faunal dynamics in considerable detail.
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  • 5
    ISSN: 1432-1939
    Keywords: Key words Grassland ; Nitrogen cycle ; Ungulates ; Yellowstone National Park ; 15N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We studied how ungulates and a large variation in site conditions influenced grassland nitrogen (N) dynamics in Yellowstone National Park. In contrast to most grassland N studies that have examined one or two soil N processes, we investigated four rates, net N mineralization, nitrification, denitrification, and inorganic N leaching, at seven paired sites inside and outside long-term (33+ year) exclosures. Our focus was how N fluxes were related to one another among highly variable grasslands and how grazers influenced those relationships. In addition, we examined variation in soil δ15N among grasslands and the relationships between soil 15N abundance and N processes. Previously, ungulates were reported to facilitate net N mineralization across variable Yellowstone grasslands and denitrification at mesic sites. In this study, we found that herbivores also promoted nitrification among diverse grasslands. Furthermore, net N mineralization, nitrification, and denitrification (kg N ha–1 year–1, each variable) were postively and linearly related to one another among all grasslands (grazed and fenced), and grazers reduced the nitrification/net N mineralization and denitrification/net N mineralization ratios, indicating that ungulates inhibited the proportion of available NH4 + that was nitrified and denitrified. There was no relationship between net N mineralization or nitrification with leaching (indexed by inorganic N adsorbed to resin buried at the bottom of rooting zones) and leaching was unaffected by grazers. Soil δ15N was positively and linearly related to in situ net N mineralization and nitrification in ungrazed grasslands; however, there was no relationship between isotopic composition of N and those rates among grazed grasslands. The results suggested that grazers simultaneously increased N availability (stimulated net N mineralization and nitrification per unit area) and N conservation (reduced N loss from the soil per unit net N mineralization) in Yellowstone grasslands. Grazers promoted N retention by stimulating microbial productivity, probably caused by herbivores promoting labile soil C. Process-level evidence for N retention by grazers was supported by soil δ15N data. Grazed grassland with high rates of N cycling had substantially lower soil δ15N relative to values expected for ungrazed grassland with comparable net N mineralization and nitrification rates. These soil 15N results suggest that ungulates inhibited N loss at those sites. Such documented evidence for consumer control of N availability to plants, microbial productivity, and N retention in Yellowstone Park is further testimony for the widespread regulation of grassland processes by large herbivores.
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  • 6
    Publication Date: 2014-03-26
    Description: Changes in land use, land cover, and land management present some of the greatest potential global environmental challenges of the 21st century. Urbanization, one of the principal drivers of these transformations, is commonly thought to be generating land changes that are increasingly similar. An implication of this multiscale homogenization hypothesis...
    Keywords: Sustainability Science
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 7
    Publication Date: 2014-06-01
    Description: Earth’s surface is rapidly urbanizing, resulting in dramatic changes in the abundance, distribution and character of surface water features in urban landscapes. However, the scope and consequences of surface water redistribution at broad spatial scales are not well understood. We hypothesized that urbanization would lead to convergent surface water abundance and distribution: in other words, cities will gain or lose water such that they become more similar to each other than are their surrounding natural landscapes. Using a database of more than 1 million water bodies and 1 million km of streams, we compared the surface water of 100 US cities with their surrounding undeveloped land. We evaluated differences in areal ( A _WB) and numeric densities ( N _WB) of water bodies (lakes, wetlands, and so on), the morphological characteristics of water bodies (size), and the density ( D _C) of surface flow channels (that is, streams and rivers). The variance of urban A _WB, N _WB, and D _C across the 100 MSAs decreased, by 89, 25, and 71%, respectively, compared to undeveloped land. These data show that many cities are surface water poor relative to undeveloped land; however, in drier landscapes urbanization increases the occurrence of surface water. This convergence pattern strengthened with development intensity, such that high intensity urban development had an areal water body density 98% less than undeveloped lands. Urbanization appears to drive the convergence of hydrological features across the US, such that surface water distributions of cities are more similar to each other than to their surrounding landscapes. ©2014 The Author(s)〈br /〉〈br /〉〈a href="http://doi.org/10.1007/s10021-014-9751-y" target="_blank"〉〈img src="http://bib.telegrafenberg.de/typo3temp/pics/f2f773b55e.png" border="0"〉〈/a〉
    Print ISSN: 1432-9840
    Electronic ISSN: 1435-0629
    Topics: Biology
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  • 8
    Publication Date: 2014-04-01
    Description: The relationship between herbivores, plants and nutrient dynamics, has been investigated in many systems; however, how these relationships are influenced by changing climate has had much less attention. In the northeastern USA, both moose populations and winter climate have been changing. Moose, once extirpated from the region, have made a comeback; while locally, snow depth and duration of snow cover have declined. There is considerable uncertainty in how these changes will interact to influence forested systems. We used small experimental plots and transects along with snow removal (to elicit soil freezing and expose potential forage plants), mechanical browsing, and fecal additions (labeled with 15N) to examine ecosystem responses. We found that snow removal changed moose browsing behavior, with balsam fir more heavily browsed than sugar maple or Viburnum under low snow conditions. Soil freezing alone did not significantly alter N dynamics or selected plant responses, but there were significant interactions with moose activity. The combined effects of moose fecal additions, mechanical browsing, and soil freezing resulted in higher levels of NO_3 − leaching under fir and maple, whereas Viburnum had essentially no response to these multiple factors. Our results suggest that declines in snow depth can initiate a cascade of ecosystem responses, beginning with exposure of plants to increased browsing that then triggers a series of responses that can lead to higher N losses, precipitated by decreased N demand in plants compromised by soil freezing damage. Balsam fir may be particularly susceptible to this cascade of multiple stresses. ©2013 Springer Science+Business Media New York
    Print ISSN: 1432-9840
    Electronic ISSN: 1435-0629
    Topics: Biology
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  • 9
    Publication Date: 2016-02-29
    Description: In an era of increasingly multidisciplinary science, it is essential to identify the frontiers as well as the core of an inherently holistic discipline: ecosystem ecology. To achieve this, we led a series of town hall events at multiple scientific-society meetings over a two-year period followed by a workshop with a diverse set of ecosystem scientists to review and expand on those outcomes. For the society town hall events ~70 individuals were asked to give short, provocative (the so-called, soapbox) presentations and audience members (~250) filled out tailored surveys. Both presentations and surveys were transcribed and themes were extracted and analyzed before and during the follow-up workshop. Formal ethnographic analysis of the soapbox texts produced three major themes: “frontiers,” “capacity building,” and “barriers to implementation,” including several subthemes. A workshop was held to analyze the ethnographic data where workshop participants further grouped key frontiers as (1) rethinking the drivers of ecosystem change, (2) new insights into ecosystem process and function, (3) evaluating human dimensions of ecosystem ecology, and (4) new angles on problem-solving/applied research. In addition, 13 experts were interviewed to crosscheck interpretations. The survey data, workshop deliberations, and expert interviews suggest that the core of these frontiers defines the current state and provides the foundational knowledge that bounds ecosystem ecology as a discipline. In response to emerging complex environmental issues and ongoing socioecological challenges, the edges of these frontiers expand fundamental ecosystem ecology to engage and intersect with disciplinary realms to create new ways of making sense of complexity, and to develop an even more holistic understanding of ecological systems. In this paper, we present our synthesis of the frontier and core research themes with the goal of inspiring the next wave of studies in ecosystem ecology. ©2016 The Author(s)〈br /〉〈br /〉〈a href="http://doi.org/10.1007/s10021-016-9967-0" target="_blank"〉〈img src="http://bib.telegrafenberg.de/typo3temp/pics/f2f773b55e.png" border="0"〉〈/a〉
    Print ISSN: 1432-9840
    Electronic ISSN: 1435-0629
    Topics: Biology
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  • 10
    Publication Date: 2016-10-12
    Description: Nitrogen (N) pollution of freshwater, estuarine and marine ecosystems is widespread and has numerous environmental and economic impacts. A portion of this excess N comes from urban watersheds comprised of natural and engineered ecosystems that can alter downstream N export. Studies of urban N cycling have focused on either specific ecosystems or on watershed-scale mass balances. Comparisons of specific N transformations across ecosystems are required to contextualize rates from individual studies. Here we reviewed urban N cycling in terrestrial, aquatic and engineered ecosystems, and compared N processing in these urban ecosystem types to native reference ecosystems. We found that net N mineralization and net nitrification rates were enhanced in urban forests and riparian zones relative to reference ecosystems. Denitrification was highly variable across urban ecosystem types, but no significant differences were found between urban and reference denitrification rates. When focusing on urban streams, ammonium uptake was more rapid than nitrate uptake in urban streams. Additionally, reduction of stormwater runoff coupled with potential decreases in N concentration suggests that green infrastructure may reduce downstream N export. Despite multiple environmental stressors in urban environments, ecosystems within urban watersheds can process and transform N at rates similar to or higher than reference ecosystems.
    Print ISSN: 0168-6496
    Electronic ISSN: 1574-6941
    Topics: Biology
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