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81.
Global assessment of experimental climate warming on tundra vegetation: heterogeneity over space and time 总被引:2,自引:0,他引:2
Elmendorf SC Henry GH Hollister RD Björk RG Bjorkman AD Callaghan TV Collier LS Cooper EJ Cornelissen JH Day TA Fosaa AM Gould WA Grétarsdóttir J Harte J Hermanutz L Hik DS Hofgaard A Jarrad F Jónsdóttir IS Keuper F Klanderud K Klein JA Koh S Kudo G Lang SI Loewen V May JL Mercado J Michelsen A Molau U Myers-Smith IH Oberbauer SF Pieper S Post E Rixen C Robinson CH Schmidt NM Shaver GR Stenström A Tolvanen A Totland O Troxler T Wahren CH Webber PJ Welker JM Wookey PA 《Ecology letters》2012,15(2):164-175
Understanding the sensitivity of tundra vegetation to climate warming is critical to forecasting future biodiversity and vegetation feedbacks to climate. In situ warming experiments accelerate climate change on a small scale to forecast responses of local plant communities. Limitations of this approach include the apparent site-specificity of results and uncertainty about the power of short-term studies to anticipate longer term change. We address these issues with a synthesis of 61 experimental warming studies, of up to 20 years duration, in tundra sites worldwide. The response of plant groups to warming often differed with ambient summer temperature, soil moisture and experimental duration. Shrubs increased with warming only where ambient temperature was high, whereas graminoids increased primarily in the coldest study sites. Linear increases in effect size over time were frequently observed. There was little indication of saturating or accelerating effects, as would be predicted if negative or positive vegetation feedbacks were common. These results indicate that tundra vegetation exhibits strong regional variation in response to warming, and that in vulnerable regions, cumulative effects of long-term warming on tundra vegetation - and associated ecosystem consequences - have the potential to be much greater than we have observed to date. 相似文献
82.
Kringelbach ML Lehtonen A Squire S Harvey AG Craske MG Holliday IE Green AL Aziz TZ Hansen PC Cornelissen PL Stein A 《PloS one》2008,3(2):e1664
Darwin originally pointed out that there is something about infants which prompts adults to respond to and care for them, in order to increase individual fitness, i.e. reproductive success, via increased survivorship of one's own offspring. Lorenz proposed that it is the specific structure of the infant face that serves to elicit these parental responses, but the biological basis for this remains elusive. Here, we investigated whether adults show specific brain responses to unfamiliar infant faces compared to adult faces, where the infant and adult faces had been carefully matched across the two groups for emotional valence and arousal, as well as size and luminosity. The faces also matched closely in terms of attractiveness. Using magnetoencephalography (MEG) in adults, we found that highly specific brain activity occurred within a seventh of a second in response to unfamiliar infant faces but not to adult faces. This activity occurred in the medial orbitofrontal cortex (mOFC), an area implicated in reward behaviour, suggesting for the first time a neural basis for this vital evolutionary process. We found a peak in activity first in mOFC and then in the right fusiform face area (FFA). In mOFC the first significant peak (p<0.001) in differences in power between infant and adult faces was found at around 130 ms in the 10-15 Hz band. These early differences were not found in the FFA. In contrast, differences in power were found later, at around 165 ms, in a different band (20-25 Hz) in the right FFA, suggesting a feedback effect from mOFC. These findings provide evidence in humans of a potential brain basis for the "innate releasing mechanisms" described by Lorenz for affection and nurturing of young infants. This has potentially important clinical applications in relation to postnatal depression, and could provide opportunities for early identification of families at risk. 相似文献
83.
Is intensity of plant root mycorrhizal colonization a good proxy for plant growth rate,dominance and decomposition in nutrient poor conditions? 下载免费PDF全文
Tatiana G. Elumeeva Vladimir G. Onipchenko Johannes H. C. Cornelissen Galina V. Semenova Lidia G. Perevedentseva Grégoire T. Freschet Richard S. P. van Logtestijn Nadejda A. Soudzilovskaia 《植被学杂志》2018,29(4):715-725
Questions
Mycorrhizae may be a key element of plant nutritional strategies and of carbon and nutrient cycling. Recent research suggests that in natural conditions, intensity of mycorrhizal colonization should be considered an important plant feature. How are inter‐specific variations in mycorrhizal colonization rate, plant relative growth rate (RGR ) and leaf litter decomposability related? Is (arbuscular) mycorrhizal colonization linked to the dominance of plant species in nutrient‐stressed ecosystems?Location
Teberda State Biosphere Reserve, northwest Caucasus, Russia.Methods
We measured plant RGR under mycorrhizal limitation and under natural nutrition conditions, together with leaf litter decomposability and field intensity of mycorrhizal colonization across a wide range of plant species, typical for alpine communities of European mountains. We applied regression analysis to test whether the intensity of mycorrhizal colonization is a good predictor of RGR and decomposition rate, and tested how these traits predict plant dominance in communities.Results
Forb species with a high level of field mycorrhizal colonization had lower RGR under nutritional and mycorrhizal limitation, while grasses were unaffected. Litter decomposition rate was not related to the intensity of mycorrhizal colonization. Dominant species mostly had a higher level of mycorrhizal colonization and lower RGR without mycorrhizal colonization than subordinate species, implying that they were more dependent on mycorrhizal symbionts. There were no differences in litter decomposability.Conclusions
In alpine herbaceous plant communities dominated by arbuscular mycorrhizae, nutrient dynamics are to a large extent controlled by mycorrhizal symbiosis. Intensity of mycorrhizal colonization is a negative predictor for whole plant RGR . Our study highlights the importance of mycorrhizal colonization as a key trait underpinning the role of plant species in carbon and nutrient dynamics in nutrient‐limited herbaceous plant communities.84.
Shifts in priming partly explain impacts of long‐term nitrogen input in different chemical forms on soil organic carbon storage 下载免费PDF全文
Minghua Song Yu Guo Feihai Yu Xianzhou Zhang Guangmin Cao Johannes H. C. Cornelissen 《Global Change Biology》2018,24(9):4160-4172
Input of labile organic carbon can enhance decomposition of extant soil organic carbon (SOC) through priming. We hypothesized that long‐term nitrogen (N) input in different chemical forms alters SOC pools by altering priming effects associated with N‐mediated changes in plants and soil microbes. The hypothesis was tested by integrating field experimental data of plants, soil microbes and two incubation experiments with soils that had experienced 10 years of N enrichment with three chemical forms (ammonium, nitrate and both ammonium and nitrate) in an alpine meadow on the Tibetan Plateau. Incubations with glucose–13C addition at three rates were used to quantify effects of exogenous organic carbon input on the priming of SOC. Incubations with microbial inocula extracted from soils that had experienced different long‐term N treatments were conducted to detect effects of N‐mediated changes in soil microbes on priming effects. We found strong evidence and a mechanistic explanation for alteration of SOC pools following 10 years of N enrichment with different chemical forms. We detected significant negative priming effects both in soils collected from ammonium‐addition plots and in sterilized soils inoculated with soil microbes extracted from ammonium‐addition plots. In contrast, significant positive priming effects were found both in soils collected from nitrate‐addition plots and in sterilized soils inoculated with soil microbes extracted from nitrate‐addition plots. Meanwhile, the abundance and richness of graminoids were higher and the abundance of soil microbes was lower in ammonium‐addition than in nitrate‐addition plots. Our findings provide evidence that shifts toward higher graminoid abundance and changes in soil microbial abundance mediated by N chemical forms are key drivers for priming effects and SOC pool changes, thereby linking human interference with the N cycle to climate change. 相似文献
85.
Protein Kinase C Activation Upregulates Intercellular Adhesion of α-Catenin–negative Human Colon Cancer Cell Variants via Induction of Desmosomes 下载免费PDF全文
Jolanda van Hengel Lionel Gohon Erik Bruyneel Stefan Vermeulen Maria Cornelissen Marc Mareel Frans van Roy 《The Journal of cell biology》1997,137(5):1103-1116
The α-catenin molecule links E-cadherin/ β-catenin or E-cadherin/plakoglobin complexes to the actin cytoskeleton. We studied several invasive human colon carcinoma cell lines lacking α-catenin. They showed a solitary and rounded morphotype that correlated with increased invasiveness. These round cell variants acquired a more normal epithelial phenotype upon transfection with an α-catenin expression plasmid, but also upon treatment with the protein kinase C (PKC) activator 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Video registrations showed that the cells started to establish elaborated intercellular junctions within 30 min after addition of TPA. Interestingly, this normalizing TPA effect was not associated with α-catenin induction. Classical and confocal immunofluorescence showed only minor TPA-induced changes in E-cadherin staining. In contrast, desmosomal and tight junctional proteins were dramatically rearranged, with a conversion from cytoplasmic clusters to obvious concentration at cell–cell contacts and exposition at the exterior cell surface. Electron microscopical observations revealed the TPA-induced appearance of typical desmosomal plaques. TPA-restored cell–cell adhesion was E-cadherin dependent as demonstrated by a blocking antibody in a cell aggregation assay. Addition of an antibody against the extracellular part of desmoglein-2 blocked the TPA effect, too. Remarkably, the combination of anti–E-cadherin and anti-desmoglein antibodies synergistically inhibited the TPA effect.
Our studies show that it is possible to bypass the need for normal α-catenin expression to establish tight intercellular adhesion by epithelial cells. Apparently, the underlying mechanism comprises upregulation of desmosomes and tight junctions by activation of the PKC signaling pathway, whereas E-cadherin remains essential for basic cell–cell adhesion, even in the absence of α-catenin.
相似文献86.
87.
Taxonomic effect on plant base concentrations and stoichiometry at the tips of the phylogeny prevails over environmental effect along a large scale gradient 下载免费PDF全文
Despite the well‐known importance of all elements to plant growth and nutrient fluxes in ecosystems, most studies to date have been restricted to the roles of foliar nitrogen (N) and phosphorus (P). Much less is known about cycling and pools of base cations in ecosystems and the drivers of variation in cation concentrations among plant species, even though these cations are paramount for plant and ecosystem function. In particular, little is known about the contributions of taxonomic position and environmental variation on base cation concentrations. The extent to which concentrations of elements in plants are determined by phenotypic response to their availability in current environments versus by inherent species‐specific uptake and processing adaptations, should be most directly evident at the tips of the phylogeny, where inherent variation among species should reflect relatively recent adaptation to environmental variation since their common ancestry. To test this hypothesis, we explored the geographic pattern and the effects of taxonomy, climate and soil on concentrations and stoichiometry of the base cations potassium (K), sodium (Na), calcium (Ca) and magnesium (Mg) across a lineage of Artemisia species and their close relatives across northern China. We found that species identity explained the largest proportion of the total variance for all four base cations (38.3–53.8%) and their stoichiometry (35.2–59.6%). K, Na and Ca concentrations increased significantly with climate seasonality, while Ca concentration decreased with annual temperature and precipitation. Plant K concentration, K:Ca and K:Mg were negatively correlated with soil organic carbon concentrations, but positively with soil pH. Our results suggest that taxonomy still needs to be fully considered for interpreting variation in vegetation nutrition and stoichiometry along broad geographical gradients even for species at the tips of the phylogeny. 相似文献
88.
89.
Plant species traits are the predominant control on litter decomposition rates within biomes worldwide 总被引:9,自引:0,他引:9
Cornwell WK Cornelissen JH Amatangelo K Dorrepaal E Eviner VT Godoy O Hobbie SE Hoorens B Kurokawa H Pérez-Harguindeguy N Quested HM Santiago LS Wardle DA Wright IJ Aerts R Allison SD van Bodegom P Brovkin V Chatain A Callaghan TV Díaz S Garnier E Gurvich DE Kazakou E Klein JA Read J Reich PB Soudzilovskaia NA Vaieretti MV Westoby M 《Ecology letters》2008,11(10):1065-1071
Worldwide decomposition rates depend both on climate and the legacy of plant functional traits as litter quality. To quantify the degree to which functional differentiation among species affects their litter decomposition rates, we brought together leaf trait and litter mass loss data for 818 species from 66 decomposition experiments on six continents. We show that: (i) the magnitude of species-driven differences is much larger than previously thought and greater than climate-driven variation; (ii) the decomposability of a species' litter is consistently correlated with that species' ecological strategy within different ecosystems globally, representing a new connection between whole plant carbon strategy and biogeochemical cycling. This connection between plant strategies and decomposability is crucial for both understanding vegetation-soil feedbacks, and for improving forecasts of the global carbon cycle. 相似文献
90.
Plant functional traits control a variety of terrestrial ecosystem processes, including soil carbon storage which is a key component of the global carbon cycle. Plant traits regulate net soil carbon storage by controlling carbon assimilation, its transfer and storage in belowground biomass, and its release from soil through respiration, fire and leaching. However, our mechanistic understanding of these processes is incomplete. Here, we present a mechanistic framework, based on the plant traits that drive soil carbon inputs and outputs, for understanding how alteration of vegetation composition will affect soil carbon sequestration under global changes. First, we show direct and indirect plant trait effects on soil carbon input and output through autotrophs and heterotrophs, and through modification of abiotic conditions, which need to be considered to determine the local carbon sequestration potential. Second, we explore how the composition of key plant traits and soil biota related to carbon input, release and storage prevail in different biomes across the globe, and address the biome-specific mechanisms by which plant trait composition may impact on soil carbon sequestration. We propose that a trait-based approach will help to develop strategies to preserve and promote carbon sequestration. 相似文献