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921.
Missing methane emissions from leaves of terrestrial plants 总被引:2,自引:0,他引:2
DAVID J. BEERLING TOM GARDINER† GRAHAM LEGGETT† Y MCLEOD‡ W. PAUL QUICK 《Global Change Biology》2008,14(8):1821-1826
The controversial claim that attached leaves of terrestrial plants emit CH4 aerobically remains to be corroborated. Here, we report CH4 fluxes and CO2 exchange rates for leaves of the C4 species Zea mays using a high-accuracy traceable online analytical system. In contrast to earlier results for Z. mays , our measurements provide no evidence for substantial aerobic CH4 emissions from photosynthesizing leaves illuminated with photosynthetically active radiation ( λ =400–700 nm), or from dark-respiring leaves. Preliminary measurements with the same system indicated a similar lack of aerobic CH4 emissions in the light or dark from leaves of the C3 species Nicotiana tabacum . These findings are supported by independent high-precision 13 C-labeling studies that also failed to confirm substantial aerobic CH4 emissions from plants. Nevertheless, we are not able to exclude the possibility that CH4 emissions from plants may be linked to nonenzymatic processes with an action spectrum lying outside the wavelength range for photosynthesis. 相似文献
922.
DIANA H. WALL MARK A. BRADFORD MARK G. ST. JOHN JOHN A. TROFYMOW VALERIE BEHAN‐PELLETIER DAVID E. BIGNELL J. MARK DANGERFIELD WILLIAM J. PARTON JOSEF RUSEK WINFRIED VOIGT VOLKMAR WOLTERS HOLLEY ZADEH GARDEL FRED O. AYUKE RICHARD BASHFORD OLGA I. BELJAKOVA PATRICK J. BOHLEN ALAIN BRAUMAN STEPHEN FLEMMING JOH R. HENSCHEL DAN L. JOHNSON T. HEFIN JONES MARCELA KOVAROVA J. MARTY KRANABETTER LES KUTNY KUO‐CHUAN LIN MOHAMED MARYATI DOMINIQUE MASSE ANDREI POKARZHEVSKII HOMATHEVI RAHMAN MILLOR G. SABARÁ JOERG‐ALFRED SALAMON MICHAEL J. SWIFT AMANDA VARELA HERALDO L. VASCONCELOS DON WHITE XIAOMING ZOU 《Global Change Biology》2008,14(11):2661-2677
Climate and litter quality are primary drivers of terrestrial decomposition and, based on evidence from multisite experiments at regional and global scales, are universally factored into global decomposition models. In contrast, soil animals are considered key regulators of decomposition at local scales but their role at larger scales is unresolved. Soil animals are consequently excluded from global models of organic mineralization processes. Incomplete assessment of the roles of soil animals stems from the difficulties of manipulating invertebrate animals experimentally across large geographic gradients. This is compounded by deficient or inconsistent taxonomy. We report a global decomposition experiment to assess the importance of soil animals in C mineralization, in which a common grass litter substrate was exposed to natural decomposition in either control or reduced animal treatments across 30 sites distributed from 43°S to 68°N on six continents. Animals in the mesofaunal size range were recovered from the litter by Tullgren extraction and identified to common specifications, mostly at the ordinal level. The design of the trials enabled faunal contribution to be evaluated against abiotic parameters between sites. Soil animals increase decomposition rates in temperate and wet tropical climates, but have neutral effects where temperature or moisture constrain biological activity. Our findings highlight that faunal influences on decomposition are dependent on prevailing climatic conditions. We conclude that (1) inclusion of soil animals will improve the predictive capabilities of region‐ or biome‐scale decomposition models, (2) soil animal influences on decomposition are important at the regional scale when attempting to predict global change scenarios, and (3) the statistical relationship between decomposition rates and climate, at the global scale, is robust against changes in soil faunal abundance and diversity. 相似文献
923.
Abstract Predation is recognized as a major selective pressure influencing population dynamics and evolutionary processes. Prey species have developed a variety of predator avoidance strategies, not least of which is olfactory recognition. However, within Australia, European settlement has brought with it a number of introduced predators, perhaps most notably the red fox (Vulpes vulpes) and domestic cat (Felis catus), which native prey species may be unable to recognize and thus avoid due to a lack of coexistence history. This study examined the response of native Tasmanian swamp rats (Rattus lutreolus velutinus) to predators of different coexistence history (native predator‐ spotted‐tail quoll (Dasyurus maculatus), domestic cats and the recently introduced red fox). We used an aggregate behavioural response of R. l. velutinus to predator integumental odour in order to assess an overall behavioural response to predation risk. Rattus lutreolus velutinus recognized the integumental odour of the native quoll (compared with control odours) but did not respond to either cat or fox scent (compared with control odur). In contrast, analyses of singular behaviours resulted in the conclusion that rats did not respond differentially to either native or introduced predators, as other studies have concluded. Therefore, measuring risk assessment behaviours at the level of overall aggregate response may be more beneficial in understanding and analysing complex behavioural patterns such as predator detection and recognition. These results suggest that fox and cat introductions (and their interactive effects) may have detrimental impacts upon small native Tasmanian mammals due to lack of recognition and thus appropriate responses. 相似文献
924.
JONG HYUN HAM † DORIS MAJERCZAK SOPHIE EWERT MYSORE-VENKATARAU SREEREKHA DAVID MACKEY DAVID COPLIN 《Molecular Plant Pathology》2008,9(5):633-643
Pantoea stewartii subsp. stewartii ( Pnss ) causes Stewart's bacterial wilt of sweet corn and leaf blight of maize. The pathogenicity of Pnss depends on synthesis of extracellular polysaccharide and an Hrp type III secretion system. WtsE, a type III secreted effector protein, is essential for the virulence of Pnss on corn. It belongs to the AvrE family of effectors, which includes DspA/E from Erwinia amylovora and AvrE1 from Pseudomonas syringae . Previously, WtsE was shown to cause disease-associated cell death in its host plant, sweet corn. Here, we examine the biological activity of WtsE in several non-host plants. WtsE induced cell death in Nicotiana benthamiana , tobacco, beet and Arabidopsis thaliana when it was transiently produced in plant cells following agroinfiltration or translocated into plant cells from Pnss , Escherichia coli or Pseudomonas syringae pv. phaseolicola ( Pph ). WtsE-induced cell death in N. benthamiana , tobacco and beet resembled a hypersensitive response and in N. benthamiana it was delayed by cycloheximide. Interestingly, WtsE strongly promoted the growth of Pnss in N. benthamiana prior to the onset of cell death. Deletion derivatives of WtsE that failed to induce cell death in N. benthamiana and tobacco also did not complement wtsE mutants of Pnss for virulence in sweet corn, indicating a correlation between the two activities. WtsE also induced cell death in A. thaliana , where it suppressed basal defences induced by Pph . Thus, WtsE has growth-promoting, defence-suppressing and cell death-inducing activities in non-host plants. Expression of WtsE also prevented the growth of yeast, possibly due to an innate toxicity to eukaryotic cells. 相似文献
925.
926.
1. Gut content analyses (GCA) of benthic macroinvertebrates, supplemented by carbon and nitrogen stable isotope analyses (SIA), were used to determine the relative contribution of leaf litter and autochthonous food sources to consumer biomass in five shaded and five unshaded streams in tropical Hong Kong. 2. Only four obligate shredders and two facultative shredders were identified out of 58 morphospecies dissected. Non‐shredder taxa consumed little (<23% food eaten) coarse particulate organic matter (CPOM) in spite of its abundance in streams, and GCA revealed that fine particulate organic matter was the major food (25–99%) of most primary consumers. 3. Stable isotope analysis results were in general agreement with the findings of GCA, and confirmed that three of the four obligate shredders had a high dependence (55–78% of assimilated carbon) on CPOM. 4. Autochthonous energy sources were important in all streams: non‐shredding primary consumers examined, which accounted for 72% of total macroinvertebrate abundance in shaded streams, derived (on average) 61% of their biomass from autochthonous foods; the equivalent values for unshaded streams were 72% (abundance) and 71% (biomass). 相似文献
927.
Experimental dietary manipulations for determining the relative importance of allochthonous and autochthonous food resources in tropical streams 总被引:3,自引:1,他引:2
1. Autochthonous sources of organic matter appear to make a minor contribution to food webs in temperate forest streams, but their roles in supporting consumer biomass in tropical lotic environments have received little attention. We investigated the importance of autochthonous and allochthonous food sources to Brotia hainanensis (Pachychilidae), a detritivorous and algivorous snail common in Hong Kong hillstreams, using experimental dietary manipulations and assimilation-based analyses, including stoichiometry, carbon (C) and nitrogen (N) stable isotopes and fatty acid (FA) profiles.
2. Juvenile B. hainanensis collected in Pak Ngau Shek Stream were cultured under controlled laboratory conditions and fed for 2 months with either conditioned Liquidambar formosana (Hamamelidaceae) leaf litter or periphyton. Samples of B. hainanensis were also collected from the stream at the end of the experiment for comparison with snails reared in the laboratory.
3. Periphyton and leaf litter exhibited marked differences in C/N ratios, δ13 C and δ 15 N values and FA profiles. Stable isotope analysis and FA profiling of laboratory-reared and field-collected B. hainanensis both confirmed that snails relied primarily on autochthonous foods, especially periphytic diatoms and cyanobacteria. Stoichiometry results indicated that periphyton was a more nutritious food (with lower C/N ratio) than leaf litter.
4. This is the first study demonstrating that the combined use of stable isotopes and FA profiles is an effective diagnostic tool to trace the basal food sources of consumers in natural stream habitats. Our findings further support the hypothesis that primary production in tropical streams is generally more important to aquatic consumers than inputs of terrestrial detritus. 相似文献
2. Juvenile B. hainanensis collected in Pak Ngau Shek Stream were cultured under controlled laboratory conditions and fed for 2 months with either conditioned Liquidambar formosana (Hamamelidaceae) leaf litter or periphyton. Samples of B. hainanensis were also collected from the stream at the end of the experiment for comparison with snails reared in the laboratory.
3. Periphyton and leaf litter exhibited marked differences in C/N ratios, δ
4. This is the first study demonstrating that the combined use of stable isotopes and FA profiles is an effective diagnostic tool to trace the basal food sources of consumers in natural stream habitats. Our findings further support the hypothesis that primary production in tropical streams is generally more important to aquatic consumers than inputs of terrestrial detritus. 相似文献
928.
DAVID M. WATERHOUSE† BENT E. K. LINDOW‡ NIKITA V. ZELENKOV§ GARETH J. DYKE 《Palaeontology》2008,51(3):575-582
Abstract: Two new fossil psittaciform birds from the Lower Eocene 'Mo Clay' (Fur Formation) of Denmark ( c . 54 Ma) are described. An unnamed specimen is assigned to the extinct avian family of stem-group parrots, Pseudasturidae (genus and species incertae sedis ), while a second ( Mopsitta tanta gen. et sp. nov.) is the largest fossil parrot yet known. Both specimens are the first fossil records of these birds from Denmark. Although the phylogenetic position of Mopsitta is unclear (it is classified as family incertae sedis ), this form is phylogenetically closer to Recent Pstittacidae than to other known Palaeogene psittaciforms and may, therefore, represent the oldest known crown-group parrot. 相似文献
929.
F. NESLIHAN INAL-EIROGLU AYSEGUL OZERDEM DAVID MIKLOWITZ AYSEN BAYKARA AYNUR AKAY 《World psychiatry》2008,7(2):110-112
The study aimed to ascertain the prevalence of mood and disruptive behavior disorders and symptoms in 35 children of 29 adult outpatients with a DSM-IV diagnosis of bipolar I disorder, compared with 33 children of 29 healthy adults, matched with patients on age, socioeconomic status and education. The offspring of bipolar patients had a 9.48 fold higher risk of receiving a psychiatric diagnosis. While only two children of patients with bipolar disorder were diagnosed with a mood disorder, 30.9% displayed mild depressed mood, compared with 8.8% of the controls, a statistically significant difference. The bipolar offspring also scored significantly higher on the hyperactivity and conduct problems subscales as well as the ADHD index of the Conners’ Teacher Rating Scale. The disruptive behavior and mood symptoms observed in early life in the offspring of bipolar patients may indicate the need for early psychosocial intervention. 相似文献
930.
J. MARK DANGERFIELD ANTHONY J. PIK DAVID BRITTON ANDREW HOLMES MICHAEL GILLINGS IAN OLIVER DAVID BRISCOE ANDREW J. BEATTIE 《Austral ecology》2003,28(3):227-236
Abstract Most ecologists are comfortable with the notion of habitats as recognizable entities and also with situations where the junction between two adjacent habitats forms a discrete edge. Such edges form naturally because of sharp changes in important edaphic, geomorphological, climatic or chemical properties to which plants, in particular, respond. Less clear is the effect of such edges on assemblages of mobile organisms, especially invertebrates that operate at relatively small spatial scales. The objective of the present study was to sample invertebrate composition across a natural edge between a well‐developed riparian habitat on fluvial sands and a saltbush habitat developed on a stony gibber plain in a semi‐arid region of New South Wales, Australia. A total of 150 pitfall traps on five 1‐km‐long transects that straddled the edge produced more than 13 000 adult specimens from 21 ordinal invertebrate taxa. A total of 10 446 beetle, ant, wasp, fly and springtail specimens were further sorted into 426 morphospecies. Comparisons and estimates of trends in abundance and richness were made, along with computation of multivariate dissimilarity and permutation statistics, to determine if the land system edge was coincident with changes in invertebrate abundance and composition. These analyses were unable to detect disjunctions in diversity coincident with the edge. The data suggest that many taxa are either present consistently in both habitats or are mostly found in one habitat but ‘leak’ several hundred metres across into the other. Few taxa were unique to either habitat. The result is that assemblage composition for invertebrates changes gradually over distances of up to 400 m either side of the edge and that the distance to a recognizable change in composition is taxon dependent. Even sharp habitat edges, as defined by discrete changes in soils and plants, are not edges but broad transition zones for many invertebrate taxa. There are several implications of these results, especially for landscape ecology. 相似文献