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  • 1
    Electronic Resource
    Electronic Resource
    FOREST PRACTICES AS NONPOINT SOURCES OF POLLUTION IN NORTH AMERICA (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 29 (1993), S. 0 
    Details
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: : Forest management activities may substantially alter the quality of water draining forests, and are regulated as nonpoint sources of pollution. Important impacts have been documented, in some cases, for undesirable changes in stream temperature and concentrations of dissolved oxygen, nitrate-N, and suspended sediments. We present a comprehensive summary of North American studies that have examined the impacts of forest practices on each of these parameters of water quality. In most cases, retention of forested buffer strips along streams prevents unacceptable increases in stream temperatures. Current practices do not typically involve addition of large quantities of fine organic material to streams, and depletion of streamwater oxygen is not a problem; however, sedimentation of gravel streambeds may reduce oxygen diffusion into spawning beds in some cases. Concentrations of nitrate-N typically increase substantially after forest harvesting and fertilization, but only a few cases have resulted in concentrations approaching the drinking-water standard of 10 mg of nitrate-NIL. Road construction and harvesting increase suspended sediment concentrations in streamwater, with highly variable results among regions in North America. The use of best management practices usually prevents unacceptable increases in sediment concentrations, but exceptionally large responses (especially in relation to intense storms) are not unusual.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1752-1688.1993.tb03233.x
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  • 2
    Electronic Resource
    Electronic Resource
    LAWS AND PROGRAMS FOR CONTROLLING NONPOINT SOURCE POLLUTION IN FOREST AREAS (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 29 (1993), S. 0 
    Details
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: : Recent federal legislation strengthened nonpoint source pollution regulations and helped to support and standardize pollution control efforts. A comprehensive review of current state and federal programs for forest areas reveals a substantial increase in agency water quality protection activities. These new efforts emphasize monitoring to assess the use and effectiveness of best management practices (BMPs). Recent monitoring reveals that BMP use is increasing and that such use typically maintains water quality within standards. However, information is generally lacking about the cost effectiveness of BMP programs. Carefully designed and executed monitoring is the key to better specification of BMPs and more cost effective water quality protection. (KEY TERMS: water quality; nonpoint source pollution; water law; watershed management; forestry; best management practices.)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1752-1688.1993.tb01500.x
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  • 3
    Electronic Resource
    Electronic Resource
    Primary production and carbon allocation in relation to nutrient supply in a tropical experimental forest (2003)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 9 (2003), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Nutrient supply commonly limits aboveground plant productivity in forests, but the effects of an altered nutrient supply on gross primary production (GPP) and patterns of carbon (C) allocation remain poorly characterized. Increased nutrient supply may lead to a higher aboveground net primary production (ANPP), but a lower total belowground carbon allocation (TBCA), with little change in either aboveground plant respiration (APR) or GPP. Alternatively, increases in nutrient supply may increase GPP, with the quantity of GPP allocated aboveground increasing more steeply than the quantity of GPP allocated belowground. To examine the effects of an elevated nutrient supply on the C allocation patterns in forests, we determined whole-ecosystem C budgets in unfertilized plots of Eucalyptus saligna and in adjacent plots receiving regular additions of 65 kg N ha−1, 31 kg P ha−1, 46 kg K ha−1, and macro- and micronutrients. We measured the absolute flux of C allocated to the components of GPP (ANPP, TBCA and APR), as well as the fraction of GPP allocated to these components.Fertilization dramatically increased GPP. Averaged over 3 years, GPP in the fertilized plots was 34% higher than that in the unfertilized controls (3.95 vs. 2.95 kg C m−2 yr−1). Fertilization-related increases in GPP were allocated entirely aboveground – ANPP was 85% higher and APR was 57% higher in the fertilized than in the control plots, while TBCA did not differ significantly between treatments. Carbon use efficiency (NPP/GPP) was slightly higher in the fertilized (0.53) compared with the control plots (0.51). Overall, fertilization increased ANPP and APR, and these increases were related to a greater GPP and an increase in the fraction of GPP allocated aboveground.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.2003.00558.x
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  • 4
    Electronic Resource
    Electronic Resource
    NITROGEN AND PHOSPHORUS CONCENTRATIONS IN FOREST STREAMS OF THE UNITED STATES (2004)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 40 (2004), S. 0 
    Details
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: : Seventy to eighty percent of the water flowing in rivers in the United States originates as precipitation in forests. This project developed a synoptic picture of the patterns in water chemistry for over 300 streams in small, forested watersheds across the United States. Nitrate (NO3−) concentrations averaged 0.31 mg N/L, with some streams averaging ten times this level. Nitrate concentrations tended to be higher in the northeastern United States in watersheds dominated by hardwood forests (especially hardwoods other than oaks) and in recently harvested watersheds. Concentrations of dissolved organic N (mean 0.32 mg N/L) were similar to those of NO3∼, whereas ammonium (NH4+) concentrations were much lower (mean 0.05 mg N/L). Nitrate dominated the N loads of streams draining hardwood forests, whereas dissolved organic N dominated the streams in coniferous forests. Concentrations of inorganic phosphate were typically much lower (mean 12 mg P/L) than dissolved organic phosphate (mean 84 mg P/L). The frequencies of chemical concentrations in streams in small, forested watersheds showed more streams with higher NO3− concentrations than the streams used in national monitoring programs of larger, mostly forested watersheds. At a local scale, no trend in nitrate concentration with stream order or basin size was consistent across studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1752-1688.2004.tb01586.x
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  • 5
    Electronic Resource
    Electronic Resource
    Do Forests Receive Occult Inputs of Nitrogen? (2000)
    Springer
    Ecosystems 3 (2000), S. 321-331 
    Details
    ISSN: 1435-0629
    Keywords: Key words: nitrogen input; forest biogeochemistry; long-term studies.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nitrogen (N) cycle of forest ecosystems is understood relatively well, and few scientists expect that major revisions will be necessary; most current work on N cycling focuses on improving the precision estimates of pools and fluxes, or measuring the magnitudes of well-known pools in response to management or disturbances. However, in the past few decades more than a dozen articles in refereed journals have claimed very high rates of N input, far beyond the rates expected for known sources of N. In this review, we summarize the literature on N accretion rates in forests that lack substantial contributions from symbiotic N-fixing plants. We critique each study for the strength of the experimental design behind the estimate of N accretion and consider whether unexpectedly large inputs of N really occur in forests. Only 6 of 24 estimates of N accretion had strong experimental designs, and only 2 of these 6 yielded estimates of 〉5 kgN ha-1 y-1. The high accretion estimates with a strong experimental design come from repeated sampling at the Walker Branch watersheds in Tennessee, where N accretion rates ranged from 50 to 80 kg N ha-1 y-1 over 15 years after harvesting. At the same location, an unharvested stand showed no significant change. We conclude that there is no widespread evidence of high rates of occult N input in forests. Too few studies have carefully tested for balanced N budgets in forests (inputs minus outputs plus change in storage), and we recommend that at least a few of these studies be undertaken on soils that permit high precision sampling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100210000029
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  • 6
    Electronic Resource
    Electronic Resource
    Rapid Changes in Soils Following Eucalyptus Afforestation in Hawaii (1999)
    Springer
    Soil Science Society of America journal 63 (1999), S. 222-225 
    Details
    ISSN: 1435-0661
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Eucalyptus saligna (Sm.)]. Soil C did not change significantly (average = -23g C m-2 yr-1 to 30 cm; 95% confidence -139 to +93g C m-2 yr-1). This lack of change in soil C resulted from a rapid loss of older soil C derived from sugarcane (-191 g C m-2 yr-1) and a rapid gain of new soil C from eucalyptus (160 g C m-2 yr-1 ). Soil N declined by 19 g N m-2 yr-1 (P = 0.08), despite fertilizer additions of 31 to 70 g m-2. Large reductions in exchangeable Ca and Mg probably resulted from dissolution and leaching of residual lime from prior agricultural management. We conclude that intensive sampling regimes may detect relatively small changes in tropical forest soils, and that expectations of C accumulation in soils following afforestation may need to be reconsidered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/
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  • 7
    Electronic Resource
    Electronic Resource
    Foliage litter quality and annual net N mineralization: comparison across North American forest sites (1997)
    Springer
    Oecologia 111 (1997), S. 151-159 
    Details
    ISSN: 1432-1939
    Keywords: Key words Litter quality ; Lignin:N ratio ; Nitrogen mineralization ; Climate ; Forests and grasslands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The feedback between plant litterfall and nutrient cycling processes plays a major role in the regulation of nutrient availability and net primary production in terrestrial ecosystems. While several studies have examined site-specific feedbacks between litter chemistry and nitrogen (N) availability, little is known about the interaction between climate, litter chemistry, and N availability across different ecosystems. We assembled data from several studies spanning a wide range of vegetation, soils, and climatic regimes to examine the relationship between aboveground litter chemistry and annual net N mineralization. Net N mineralization declined strongly and non-linearly as the litter lignin:N ratio increased in forest ecosystems (r 2 = 0.74, P 〈 0.01). Net N mineralization decreased linearly as litter lignin concentration increased, but the relationship was significant (r 2 = 0.63, P 〈 0.01) only for tree species. Litterfall quantity, N concentration, and N content correlated poorly with net N mineralization across this range of sites (r 2 〈 0.03, P = 0.17–0.26). The relationship between the litter lignin:N ratio and net N mineralization from forest floor and mineral soil was similar. The litter lignin:N ratio explained more of the variation in net N mineralization than climatic factors over a wide range of forest age classes, suggesting that litter quality (lignin:N ratio) may exert more than a proximal control over net N mineralization by influencing soil organic matter quality throughout the soil profile independent of climate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050219
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  • 8
    Electronic Resource
    Electronic Resource
    An empirical analysis of the factors contributing to 20-year decrease in soil pH in an old-field plantation of loblolly pine (1989)
    Springer
    Biogeochemistry 8 (1989), S. 39-54 
    Details
    ISSN: 1573-515X
    Keywords: acid deposition ; forest decline ; soil acidification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The pH of weak-acid solutions is controlled by acid concentration (HA + A−), the degree of acid dissociation (A−/HA), and the strength of the acids present (pKa). We developed an empirical approach that allows the relative importance of each of these factors to be estimated for soils. This empirical model was applied to soils collected from an old-field plantation of loblolly pine (Pinus taeda L.) at 5 and 25 years of age. During this period, soil pH dropped by 0.3 to 0.8 units, and extractable calcium, magnesium and potassium declined by 20 to 80%. The empirical model indicates that the decline in pH resulted largely from the reduction in base saturation of the exchange complex. However, the average acid strength of the exchange complex decreased during the 20 years, preventing a greater decline of perhaps 0.1 to 0.2 units in the observed pH. The rate of decrease in the acid neutralizing capacity to pH 3.5 was about 1.3 kmolc/ha annually, while the increase in base neutralizing capacity was about 2.7 and 1.6 kmolc/ha annually to pH 5.5 and 8.2, respectively. Extractable alkali and alkaline earth cations declined by about 2.2 kmolc/ha annually, matched by the rate of increase in aluminium. These changes demonstrated the dynamic nature of poorly buffered soils, and indicated that changes in soil acidity may be expected over a period of decades (especially following changes in land-use).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02180166
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  • 9
    Electronic Resource
    Electronic Resource
    Why do Tree Species Affect Soils? The Warp and Woof of Tree-soil Interactions (1998)
    Springer
    Biogeochemistry 42 (1998), S. 89-106 
    Details
    ISSN: 1573-515X
    Keywords: nutrient availability ; soil development ; tree-soil interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Many ideas have been advanced regarding how trees affect soils. Enough evidence is now available to evaluate the strength of these ideas and to consider interactions between tree species and soils in an evolutionary context. Forest floor mass commonly differs by about 20% for different species growing on the same site; differences of up to 5-fold have been reported. Litterfall mass and N content commonly differ by 20 to 30%, but larger differences are also common (especially with N-fixing species). The net mineralization of soil N typically differs by 50% or more among species, indicating very strong feedback possibilities. We evaluate the evolutionary context of tree effects on soils by considering 3 degrees of coupling of trees to soils: tightly woven connections where the fitness of the tree is enhanced by its effect on soils; loosely woven interactions where selection for tree fitness unrelated to soil properties leads to indirect effects on soils (either enhancing or impairing fitness); and frayed interactions where the effects of trees on soil derive from features of the ecosystem that do not involve direct selection for tree fitness. Evidence supports each of these degrees of interaction for at least some cases, and no single context explains all the interactions between trees and soils. Important areas for further work include: next-generation assessments of the effects of trees on soil suitability for the same (and different) species, and the role of soil organisms in developing and modifying the effects of trees on soils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005948126251
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  • 10
    Electronic Resource
    Electronic Resource
    Nitrogen fixation and the mass balances of carbon and nitrogen in ecosystems (1998)
    Springer
    Biogeochemistry 43 (1998), S. 63-78 
    Details
    ISSN: 1573-515X
    Keywords: carbon ; mass balance ; nitrogen ; nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Ecosystems with high rates of nitrogen fixation often have high loss rates through leaching or possibly denitrification. However, there is no formal theoretical context to examine why this should be the case nor of how nitrogen accumulates in such open systems. Here, we propose a simple model coupling nitrogen inputs and losses to carbon inputs and losses. The nitrogen balance of this model system depends on plant (nitrogen fixer) growth rate, its carrying capacity, N fixed/C fixed, residence time of nitrogen and carbon in biomass, litter decay rate, litter N/C, and fractional loss rate of mineralized nitrogen. The model predicts the requirements for equilibrium in a nitrogen-fixing system, and the conditions on nitrogen fixation and losses in order for the system to accumulate nitrogen and carbon. In particular, the accumulation of nitrogen and carbon in a nitrogen-fixing system depend on an interaction between residence time in vegetation and litter decay rate in soil. To reflect a possible increased uptake of soil nitrogen and decreased respiratory cost of symbiotic nitrogen fixers, the model was then modified so that fixation rate decreased and growth rate increased as nitrogen capital accumulated. These modifications had only small effects on carbon and nitrogen accumulation. This suggests that switching from uptake of atmospheric nitrogen to mineral soil nitrogen as nitrogen capital accumulates simply results in a trade-off between energetic limitations and soil nitrogen limitations to carbon and nitrogen accumulation. Experimental tests of the model are suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006057428096
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