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81.
Contemporary carbon balance and late Holocene carbon accumulation in a northern peatland 总被引:2,自引:0,他引:2
NIGEL T. ROULET †‡ PETER M. LAFLEUR§ PIERRE J. H. RICHARD¶ ‡ TIM R. MOORE ‡ ELYN R. HUMPHREYS JILL BUBIER 《Global Change Biology》2007,13(2):397-411
Northern peatlands contain up to 25% of the world's soil carbon (C) and have an estimated annual exchange of CO2‐C with the atmosphere of 0.1–0.5 Pg yr−1 and of CH4‐C of 10–25 Tg yr−1. Despite this overall importance to the global C cycle, there have been few, if any, complete multiyear annual C balances for these ecosystems. We report a 6‐year balance computed from continuous net ecosystem CO2 exchange (NEE), regular instantaneous measurements of methane (CH4) emissions, and export of dissolved organic C (DOC) from a northern ombrotrophic bog. From these observations, we have constructed complete seasonal and annual C balances, examined their seasonal and interannual variability, and compared the mean 6‐year contemporary C exchange with the apparent C accumulation for the last 3000 years obtained from C density and age‐depth profiles from two peat cores. The 6‐year mean NEE‐C and CH4‐C exchange, and net DOC loss are −40.2±40.5 (±1 SD), 3.7±0.5, and 14.9±3.1 g m−2 yr−1, giving a 6‐year mean balance of −21.5±39.0 g m−2 yr−1 (where positive exchange is a loss of C from the ecosystem). NEE had the largest magnitude and variability of the components of the C balance, but DOC and CH4 had similar proportional variabilities and their inclusion is essential to resolve the C balance. There are large interseasonal and interannual ranges to the exchanges due to variations in climatic conditions. We estimate from the largest and smallest seasonal exchanges, quasi‐maximum limits of the annual C balance between 50 and −105 g m−2 yr−1. The net C accumulation rate obtained from the two peatland cores for the interval 400–3000 bp (samples from the anoxic layer only) were 21.9±2.8 and 14.0±37.6 g m−2 yr−1, which are not significantly different from the 6‐year mean contemporary exchange. 相似文献
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JANET E. BERTRAM TIM J. CLOUGH ROBERT R. SHERLOCK LEO M. CONDRON MAUREEN O'CALLAGHAN† NAOMI S. WELLS JESSICA L. RAY 《Global Change Biology》2009,15(8):2067-2077
Atmospheric concentrations of the greenhouse gas nitrous oxide (N2 O) have continued to rise since the advent of the industrial era, largely because of the increase in agricultural land use. The urine deposited by grazing ruminant animals is a major global source of agricultural N2 O. With the first commitment period for reducing greenhouse gas emissions under the Kyoto Protocol now underway, mitigation options for ruminant urine N2 O emissions are urgently needed. Recent studies showed that increasing the urinary concentration of the minor urine constituent hippuric acid resulted in reduced emissions of N2 O from a sandy soil treated with synthetic bovine urine, due to a reduction in denitrification. A similar effect was seen when benzoic acid, a product of hippuric acid hydrolysis, was used. This current laboratory experiment aimed to investigate these effects using real cow urine for the first time. Increased concentrations of hippuric acid or benzoic acid in the urine led to reduction of N2 O emissions by 65% (from 17% to <6% N applied), with no difference between the two acid treatments. Ammonia volatilization did not increase significantly with increased hippuric acid or benzoic acid concentrations in the urine applied. Therefore, there was a net reduction in gaseous N loss from the soil with higher urinary concentrations of both hippuric acid and benzoic acid. The results show that elevating hippuric acid in the urine had a marked negative effect on both nitrification and denitrification rates and on subsequent N2 O fluxes. This study indicates the potential for developing a novel mitigation strategy based on manipulation of urine composition through ruminant diet. 相似文献
84.
Abstract: Weather and climatic conditions may impact on the timing of breeding in birds. We examined changes in the laying date of the starling Sturnus vulgaris at Lower Hutt, New Zealand in the period 1970–2003 and investigated possible relationships with the El Niño Southern Oscillation (ENSO). Laying dates (expressed both as first and modal dates for the local population) were significantly delayed over the study period, i.e. starlings tended to lay later. The timing of breeding was non‐linearly related to ENSO, with early laying associated with both low and high values of ENSO. We suggest that changes in laying dates varied with food availability, which fluctuated according to climatic events. 相似文献
85.
TIM M. BERRA
fls GONZALO ALVAREZ KATE SHANNON 《Biological journal of the Linnean Society. Linnean Society of London》2010,101(1):228-241
A pedigree of the Galton–Darwin–Wedgwood families that was exhibited as a poster at the Third International Congress of Eugenics in 1932 at the American Museum of Natural History has been located in the archives of Truman State University in Kirksville, Missouri. This pedigree was prepared by Harry Hamilton Laughlin, Director of the Eugenics Record Office of the Carnegie Institute. The pedigree shows consanguineous marriages within the three families. A special collection of rare Darwin family photographs assembled by Leonard Darwin has also been found in the Truman State University archives. These photographs were exhibited as a poster alongside the pedigree at the 1932 Eugenics Congress. The poster of the Galton–Darwin–Wedgwood pedigree is published here, together with a tabular version providing ready access to the information contained in the pedigree. Also included are the Darwin family photographs and a biographical sketch of Laughlin. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 228–241. 相似文献
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PHILLIP CASSEY TIM M. BLACKBURN RICHARD P. DUNCAN STEVEN L. CHOWN 《Austral ecology》2005,30(4):475-480
Abstract Biological invasions have commonly occurred, and to a lesser degree continue to do so, without human assistance. It is, however, a combination of the rate and magnitude, as well as the distances and agency involved, that separates human‐driven invasion processes from self‐perpetuated colonization events. Exotic species are a pervasive and major component of human‐induced global change. Decisions to manage invasive species will require judgements to be communicated from scientists to policy makers, because scientists may often be the only ones in the position to make them. 相似文献
88.
Hydraulic microhabitats and the distribution of macroinvertebrate assemblages in riffles 总被引:6,自引:0,他引:6
1. The influence of hydraulic conditions on the spatial distribution of macroinvertebrate assemblages was investigated in three riffles in a perennial Australian river. 2. Velocity, depth and variability of substrate roughness were measured at each of 56 macroinvertebrate sampling locations. Complex hydraulic variables (roughness Reynolds number, shear velocity, Froude number) were calculated from combinations of two or three of the directly measured variables. The biological significance of directly measured and complex hydraulic variables was determined by a combination of univariate and multivariate statistical procedures. 3. Macroinvertebrate abundance, number of taxa and community composition were significantly different between the identified roughness Reynolds number, Froude number, velocity and shear velocity microhabitats throughout the studied riffles. 4. Regression analysis showed macroinvertebrate abundance and number of taxa were negatively related to roughness Reynolds number, shear velocity, velocity and Froude number. Depth was negatively related to abundance. In general, the majority of the macroinvertebrate community preferred the areas of riffles with the lowest near‐bed turbulence. 5. Roughness Reynolds number explained more of the spatial variation in invertebrate abundance, number of taxa and community composition than the other hydraulic variables, either directly measured or calculated. Of the directly measured variables, velocity had the greatest explanatory power, which was marginally less than roughness Reynolds number and shear velocity. 6. This study demonstrated that small‐scale differences in hydraulic conditions created by combinations of velocity, depth and substrate roughness have an important role in the spatial distribution of macroinvertebrate assemblages in riffle habitats. 相似文献
89.
TIM C. G. RICH DAVID MARDON IAN CURTIS STAN J. HEYWARD VERA G. HEYWARD DOUGLAS R. MCKEAN TONY HALL STACEY HARRIS ANTONY O'ROURKE ROBYN S. COWAN MICHAEL F. FAY fls 《Botanical journal of the Linnean Society. Linnean Society of London》2005,147(2):203-211
Sagina boydii F. B. White (Caryophyllaceae), Boyd's pearlwort, is an enigmatic taxon of unknown geographical origin which is only known in cultivation and is of uncertain taxonomic status. Morphological, cytological and geographical evidence suggests that it is most similar to S. procumbens L. and S. saginoides (L.) H. Karst., but it differs in its compact growth form. Genetically, AFLP analysis shows that it can be included as part of the variation in S. procumbens . In cultivation, it will grow true from seed. Other compact growth forms occur in S. procumbens but do not grow true from seed. As S. boydii is part of the variation in S. procumbens , is of uncertain geographical origin, is known only in cultivation, and grows true from seed, it is best treated as a new cultivar, Sagina procumbens 'Boydii'. A neotype and standard specimen is designated. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 147 , 203–211. 相似文献
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