| 1. |
- Conley, Daniel, et al.
(författare)
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Deforestation causes increased dissolved silicate losses in the Hubbard Brook Experimental Forest
- 2008
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013. ; 14:11, s. 2548-2554
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Tidskriftsartikel (refereegranskat)abstract
- Globally significant increases in the riverine delivery of nutrients and suspended particulate matter have occurred with deforestation. We report here significant increases in streamwater transport of dissolved silicate (DSi) following experimental forest harvesting at the Hubbard Brook Experimental Forest, NH, USA. The magnitude of the streamwater response varied with the type of disturbance with the highest DSi export fluxes occurring in the manipulations that left the most plant materials on the soil surface and disturbed the soil surface least. No measurable loss of amorphous silica (ASi) was detected from the soil profile; however, ASi was redistributed within the soil profile after forest disturbance. Mass-balance calculations demonstrate that some fraction of the DSi exported must come from dissolution of ASi and export as DSi. Land clearance and the development of agriculture may result in an enhanced flux of DSi coupled with enhanced erosion losses of ASi contained in phytoliths.
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| 2. |
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| 3. |
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| 4. |
- Lindenmayer, D. B., et al.
(författare)
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Value of long-term ecological studies
- 2012
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Ingår i: Austral ecology (Print). - : Wiley. - 1442-9985 .- 1442-9993. ; 37:7, s. 745-757
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Forskningsöversikt (refereegranskat)abstract
- Long-term ecological studies are critical for providing key insights in ecology, environmental change, natural resource management and biodiversity conservation. In this paper, we briefly discuss five key values of such studies. These are: (1) quantifying ecological responses to drivers of ecosystem change; (2) understanding complex ecosystem processes that occur over prolonged periods; (3) providing core ecological data that may be used to develop theoretical ecological models and to parameterize and validate simulation models; (4) acting as platforms for collaborative studies, thus promoting multidisciplinary research; and (5) providing data and understanding at scales relevant to management, and hence critically supporting evidence-based policy, decision making and the management of ecosystems. We suggest that the ecological research community needs to put higher priority on communicating the benefits of long-term ecological studies to resource managers, policy makers and the general public. Long-term research will be especially important for tackling large-scale emerging problems confronting humanity such as resource management for a rapidly increasing human population, mass species extinction, and climate change detection, mitigation and adaptation. While some ecologically relevant, long-term data sets are now becoming more generally available, these are exceptions. This deficiency occurs because ecological studies can be difficult to maintain for long periods as they exceed the length of government administrations and funding cycles. We argue that the ecological research community will need to coordinate ongoing efforts in an open and collaborative way, to ensure that discoverable long-term ecological studies do not become a long-term deficiency. It is important to maintain publishing outlets for empirical field-based ecology, while simultaneously developing new systems of recognition that reward ecologists for the use and collaborative sharing of their long-term data sets. Funding schemes must be re-crafted to emphasize collaborative partnerships between field-based ecologists, theoreticians and modellers, and to provide financial support that is committed over commensurate time frames.
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| 5. |
- Saccone, Loredana, et al.
(författare)
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Factors that Control the Range and Variability of Amorphous Silica in Soils in the Hubbard Brook Experimental Forest
- 2008
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Ingår i: Soil Science Society of America Journal. - : Wiley. - 0361-5995. ; 72:6, s. 1637-1644
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Tidskriftsartikel (refereegranskat)abstract
- In terrestrial ecosystems, the largest pool of amorphous silica (ASi) is stored in soils and is an important reservoir of biologically active Si for the global biogeochemical cycling of Si. Only limited data are available that quantify the size of this reservoir and often these estimates are made from the physical separation of silt-sized phytoliths, which can underestimate the ASi pool. Soil samples from five watersheds in a temperate-zone continental ecosystem at the Hubbard Brook Experimental Forest, New Hampshire, were analyzed for ASi using alkaline digestion. Soils from two of the watersheds were analyzed after experimental forest removal. In undisturbed watersheds, ASi was concentrated at the surface of the soil profile, similar to organic matter, and then progressively decreased with depth. This investigation supports our hypothesis that forest disturbance leads to redistribution of Si in the soil. In fact, although deforestation led to significant decreases in ASi in the upper soil horizons, total profile ASi (similar to 17,400 kg SiO2 ha(-1)) remained essentially unchanged, implying translocation downward. Significant increases in the transport of dissolved silica (DSi) by rivers have been observed With deforestation, however, in which the ASi pool in soils may play an important role. Additional studies should target the potential role of ASi as a buffer for DSi losses from deforested watersheds.
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| 6. |
- Lindenmayer, David B., et al.
(författare)
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New Policies for Old Trees : Averting a Global Crisis in a Keystone Ecological Structure
- 2014
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Ingår i: Conservation Letters. - : Wiley. - 1755-263X. ; 7:1, s. 61-69
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Tidskriftsartikel (refereegranskat)abstract
- Large old trees are critical organisms and ecological structures in forests, woodlands, savannas, and agricultural and urban environments. They play many essential ecological roles ranging from the storage of large amounts of carbon to the provision of key habitats for wildlife. Some of these roles cannot be replaced by other structures. Large old trees are disproportionately vulnerable to loss in many ecosystems worldwide as a result of accelerated rates of mortality, impaired recruitment, or both. Drivers of loss, such as the combined impacts of fire and browsing by domestic or native herbivores, chemical spray drift in agricultural environments, and postdisturbance salvage logging, are often unique to large old trees but also represent ecosystem-specific threats. Here, we argue that new policies and practices are urgently needed to conserve existing large old trees and restore ecologically effective and viable populations of such trees by managing trees and forests on much longer time scales than is currently practiced, and by protecting places where they are most likely to develop. Without these steps, large old trees will vanish from many ecosystems, and associated biota and ecosystem functions will be severely diminished or lost.
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| 7. |
- Liptzin, Daniel, et al.
(författare)
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Spatial and Temporal Patterns in Atmospheric Deposition of Dissolved Organic Carbon
- 2022
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Ingår i: Global Biogeochemical Cycles. - : American Geophysical Union (AGU). - 0886-6236 .- 1944-9224. ; 36:10
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric deposition of dissolved organic carbon (DOC) to terrestrial ecosystems is a small, but rarely studied component of the global carbon (C) cycle.Emissions of volatile organic compounds (VOC) and organic particulates are the sources of atmospheric C and deposition represents a major pathway for the removal of organic C from the atmosphere.Here, we evaluate the spatial and temporal patterns of DOC deposition using 70 data sets at least one year in length ranging from 40° south to 66° north latitude. Globally, the median DOC concentration in bulk deposition was 1.7 mg L −1. The DOC concentrations were significantly higher in tropical (<25°) latitudes compared to temperate (>25°) latitudes.DOC deposition was significantly higher in the tropics because of both higher DOC concentrations and precipitation. Using the global median or latitudinal specific DOC concentrations leads to a calculated global deposition of 202 or 295 Tg C yr −1 respectively.Many sites exhibited seasonal variability in DOC concentration. At temperate sites, DOC concentrations were higher during the growing season; at tropical sites, DOC concentrations were higher during the dry season. Thirteen of the thirty-four long-term (>10 years) data sets showed significant declines in DOC concentration over time with the others showing no significant change.Based on the magnitude and timing of the various sources of organic C to the atmosphere, biogenic VOCs likely explain the latitudinal pattern and the seasonal pattern at temperate latitudes while decreases in anthropogenic emissions are the most likely explanation for the declines in DOC concentration.
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| 8. |
- Rhoades, Charles C., et al.
(författare)
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Biogeochemistry of beetle-killed forests : Explaining a weak nitrate response
- 2013
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 110:5, s. 1756-1760
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Tidskriftsartikel (refereegranskat)abstract
- A current pine beetle infestation has caused extensive mortality of. lodgepole pine (Pinus contorta) in forests of Colorado and Wyoming; it is part of an unprecedented multispecies beetle outbreak extending from Mexico to Canada. In United States and European watersheds, where atmospheric deposition of inorganic N is moderate to low (<10 kg.ha.y), disturbance of forests by timber harvest or violent storms causes an increase in stream nitrate concentration that typically is close to 400% of predisturbance concentrations. In contrast, no significant increase in streamwater nitrate concentrations has occurred following extensive tree mortality caused by the mountain pine beetle in Colorado. A model of nitrate release from Colorado watersheds calibrated with field data indicates that stimulation of nitrate uptake by vegetation components unaffected by beetles accounts for significant nitrate retention in beetle-infested watersheds. The combination of low atmospheric N deposition (<10 kg.ha.y), tree mortality spread over multiple years, and high compensatory capacity associated with undisturbed residual vegetation and soils explains the ability of these beetle-infested watersheds to retain nitrate despite catastrophic mortality of the dominant canopy tree species.
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| 9. |
- Svensson, Teresia, 1975-, et al.
(författare)
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Is chloride a conservative ion in forest ecosystems?
- 2012
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Ingår i: Biogeochemistry. - : Springer. - 0168-2563 .- 1573-515X. ; 107:1-3, s. 125-134
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Tidskriftsartikel (refereegranskat)abstract
- Chloride (Cl-) has often been assumed to be relatively unreactive in forest ecosystems, and is frequently used as a conservative tracer to calculate fluxes of water and other ions. Recently, however, several studies have detailed cycling of Cl- in vegetation and soils. In this study Cl- budgets are compiled from 32 catchment studies to determine the extent to which Cl- is conserved in the passage through forest ecosystems. Chloride budgets from these sites vary from net retention (input/output) to net release (output/input). In the overall data set, including those sites with very high inputs of seasalt Cl-, there was a strong correspondence between inputs and outputs. However, sites with low Cl- deposition (<6 kg ha-1 year-1) consistently showed net release of Cl-, suggesting an internal source or a declining internal pool. The results indicate that Cl- may be a conservative ion in sites with high Cl- deposition, but in sites with low deposition Cl- may not be conservative. We discuss the possible causes of the Cl- imbalance and reasons why Cl- may not be conservative in ecosystem functions.
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