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Meng F.D.,CAS Institute of Tibetan Plateau Research | Jiang L.L.,CAS Institute of Tibetan Plateau Research | Zhang Z.H.,CAS Northwest Institute of Plateau Biology | Cui S.J.,CAS Institute of Tibetan Plateau Research | And 20 more authors.
Ecology | Year: 2017

Our ability to predict how temperature modifies phenology at the community scale is limited by our lack of understanding of responses by functional groups of flowering plants. These responses differ among species with different life histories. We performed a reciprocal transplant experiment along four elevation gradients (e.g., 3,200, 3,400, 3,600 and 3,800 m) to investigate the effects of warming (transferred downward) and cooling (transferred upward) on plant flowering functional groups (FFGs) and community phenological sequences (i.e., seven phenological events). Warming significantly decreased early-spring- flowering (ESF) plant coverage and increased mid-summer- flowering plant (MSF) coverage, while cooling had the opposite effect. All community phenological events were advanced by warming and delayed by cooling except for the date of complete leaf-coloring, which showed the opposite response. Warming and cooling could cause greater advance or delay in early-season phenological events of the community through increased coverage of MSF species, and warming could delay late-season phenological events of the community by increased coverage of ESF species. These results suggested that coverage change of FFGs in the community induced by temperature change could mediate the responses of the community phenological events to temperature change in the future. The response of phenological events to temperature change at the species level may not be sufficient to predict phenological responses at the community-level due to phenological compensation between species in the community. © 2016 by the Ecological Society of America.


Hu Y.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Hu Y.,Key Laboratory of Stress Physiology and Ecology in Cold and Arid Regions of Gansu Province | Wang Q.,CAS Institute of Tibetan Plateau Research | Wang Q.,University of Chinese Academy of Sciences | And 10 more authors.
Plant and Soil | Year: 2016

Aims: A lacking of understanding about cooling effects on methane (CH4) fluxes and potential asymmetrical responses to warming and cooling causes uncertainty about climate change effects on the atmospheric CH4 concentration. We investigated CH4 fluxes in an alpine meadow on the Tibetan Plateau in response to climate warming and cooling. Methods: A 2-year reciprocal translocation experiment was implemented to simulate climate warming (i.e. downward translocation) and cooling (i.e. upward translocation) along an elevation gradient with four different vegetation types (at 3200, 3400, 3600 and 3800 m elevation) during the growing season (May to October) in 2008 and 2009. Results: Although the effects of warming and cooling varied depending on vegetation type, elevation and timescale (i.e., daily and seasonally), warming increased average seasonal CH4 uptake by 60 %, while cooling reduced it by 19 % across all vegetation types, based on a 1.3–5.1 °C difference in soil temperature at 20 cm depth. Soil temperature over the range of 4–10 °C explained 11–25 % of the variation in average seasonal CH4 fluxes, while there was no relationship with soil moisture over the range of 13–39 % and soil NH4 +-N and NO3 −N content. Methane uptake was more sensitive to warming than to cooling. Conclusions: Because of warming and cooling spells in the alpine region, warming effects on CH4 uptake would be over-estimated by 64 % if cooling effects on it are not considered. Our findings suggest that asymmetrical responses of CH4 fluxes to warming and cooling should be taken into account when evaluating the effects of climate change on CH4 uptake in the alpine meadow on the Tibetan plateau. © 2016 Springer International Publishing Switzerland


Duan J.,CAS Institute of Tibetan Plateau Research | Duan J.,Binhai Research Institute in Tianjin | Wang S.,CAS Institute of Tibetan Plateau Research | Wang S.,CAS Northwest Institute of Plateau Biology | And 13 more authors.
Soil Biology and Biochemistry | Year: 2013

Few studies of the effects of litter diversity on the temperature sensitivity of mixed litter mass loss (MLML) are available. We tested the hypothesis that high litter diversity would reduce the magnitude of effects of climate and environmental change on MLML with 0.5/1 mm litter bags and sampling once after 1 yr of decomposition, using 51 combinations of litter mixtures from 25 dominant species at 3200 and 3800 m elevations on the Tibetan Plateau. Generally, our study supported our hypothesis. High temperature (i.e. lower elevation) reduced the dependency of MLML and non-additive effects on species richness. Species composition significantly affected MLML and its Q10 (i.e. the ratio of litter mass loss rate at a temperature T1 that is 10 °C lower than a temperature T2) when species richness was less than 8. Shrubs significantly decreased the Q10 of MLML when the species richness of litter mixture was less than 4. These findings suggest that the influence of future warming on MLML may depend on the balance between the magnitude of the impacts of climate change on shrub invasion and loss of species diversity in alpine region. © 2012 Elsevier Ltd.


Jiang L.L.,CAS Institute of Tibetan Plateau Research | Jiang L.L.,Tibet University | Wang S.P.,CAS Institute of Tibetan Plateau Research | Wang S.P.,Tibet University | And 31 more authors.
Ecology | Year: 2016

The timing of the fruit-set stage (i.e., start and end of fruit set) is crucial in a plant's life cycle, but its response to temperature change is still unclear. We investigated the timing of seven phenological events, including fruit-set dates during 3 yr for six alpine plants transplanted to warmer (approximately +3.5°C in soils) and cooler (approximately -3.5°C in soils) locations along an altitudinal gradient in the Tibetan area. We found that fruit-set dates remained relatively stable under both warming and cooling during the 3-yr transplant experiment. Three earlier phenological events (emergence of first leaf, first bud set, and first flowering) and two later phenological events (first leaf coloring and complete leaf coloring) were earlier by 4.8-8.2 d/°C and later by 3.2-7.1 d/°C in response to warming. Conversely, cooling delayed the three earlier events by 3.8-6.9 d/°C and advanced the two later events by 3.2-8.1 d/°C for all plant species. The timing of the first and/or last fruit-set dates, however, did not change significantly compared to earlier and later phenological events. Statistical analyses also showed that the dates of fruit set were not significantly correlated or had lower correlations with changes of soil temperature relative to the earlier and later phenological events. Alpine plants may thus acclimate to changes in temperature for their fruiting function by maintaining relatively stable timings of fruit set compared with other phenological events to maximize the success of seed maturation and dispersal in response to short-term warming or cooling. © 2016 by the Ecological Society of America.


Hu Y.,CAS Institute of Tibetan Plateau Research | Hu Y.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Jiang L.,CAS Institute of Tibetan Plateau Research | Wang S.,CAS Institute of Tibetan Plateau Research | And 11 more authors.
Agricultural and Forest Meteorology | Year: 2016

Information about the potential effects of climate change, especially cooling, on ecosystem respiration (Re) in alpine meadows is scarce. We determined the effects of warming and cooling on Re on the Tibetan Plateau using a 2-year reciprocal translocation experiment with 4 different vegetation types (3 alpine meadows and 1 alpine shrub differentiated by plant community composition) along an elevation gradient from 3200 to 3800m (with vegetation types E2, E4, E6 and E8 at 3200, 3600, 3800 and 3800m, respectively) during the growing seasons in 2008 and 2009. Mean growing seasonal Re decreased by 13.6, 30.3 and 40.7% per 200m rise in elevation (cooling) for vegetation types E2, E4 and E6, but increased by 1.3, 35.9 and 58.8% per 200m decrease in elevation (warming) for vegetation types E4, E6 and E8, respectively. Soil temperature explained 49.3-64.0% of daily Re variation and aboveground biomass explained 21.5-61.6% of average Re variation of the growing season for all vegetation types, but the effect of soil moisture on Re was small over 2-year. The values of Re temperature sensitivity increased with an increase in elevation for both warming (3.3, 24.3 and 53.5%°C-1 for vegetation types E4, E6 and E8) and cooling (8.0, 19.1 and 24.4%°C-1 for vegetation types E2, E4 and E6), suggesting that alpine meadow at higher elevation was more sensitive to both warming and cooling. Based on the values of Re temperature sensitivity for all pooled vegetation types (25.4, 5.6 and 19.6%°C-1 for warming, cooling and pooled warming and cooling), it could be over-estimated by 23% for warming alone compared with pooled warming and cooling. Therefore, asymmetrical responses of Re to warming and cooling should be taken into account when we evaluate the effect of temperature change on Re using models in the future. © 2015.


Wang S.,CAS Institute of Tibetan Plateau Research | Wang C.,CAS Institute of Tibetan Plateau Research | Wang C.,University of Chinese Academy of Sciences | Duan J.,CAS Northwest Institute of Plateau Biology | And 9 more authors.
Agricultural and Forest Meteorology | Year: 2014

Previous studies have focused on the effects of increased temperatures on a single green-up and/or flowering event, but less is known about how acceleration of spring phenology may change subsequent phenological events. We present results of a field experiment to test the hypotheses that (1) the timing of phenological events does not necessarily delay as elevation increases; (2) changes in the timing of a sequence of phenological events will be consistent for all phenological events along the elevation gradient; and thus (3) change in the timing of phenological events does not affect the duration of the entire reproductive stage in the alpine region. The experiment was conducted along an elevation gradient from 3200 to 3800. m using two early-spring flowering (ESF) sedges and four mid-summer flowering (MSF) plants (two forbs and two grasses). Generally, our results only supported the first hypothesis. Lower elevation delayed the starting dates of all phenological events for ESF plants at 3200. m compared with other elevations, whereas the opposite trend was observed for MSF-grasses. MSF-forbs had the earliest leaf-out at 3200. m and the earliest first flowering at 3600. m, and onset of fruit-set advanced with increasing elevation. The entire reproductive duration was shortened with increasing elevation for MSF-forbs, whereas it was the shortest for ESF at 3600. m and for MSF-grasses at 3200 and/or 3800. m. Individual reproductive stages had independent responses to climate change. The duration of the entire growing season for ESF plants decreased as elevation increased. For MSF-forbs, it was longest at 3200. m and shortest at 3400. m, while for MSF-grasses it was shortest at 3200. m and at 3800. m. Reproduction was compressed into shorter time periods only for MSF-forbs at 3600 and 3800. m. Therefore, reproduction is not tightly integrated across the life cycle, and earlier reproductive development induced by warmer spring temperatures did not consistently advance flowering and fruiting times and their durations for the alpine plants studied. The effects of climate change on the timing and duration of phenological events were species-specific. Selection for changes in the timing and duration of individual phenological stages in response to climate change due to evolutionary adaptation should be taken into account. © 2014 Elsevier B.V.


PubMed | Eastern Oregon University, National Institute for Agro Environment science, CAS Northwest Institute of Plateau Biology, Tibet University and 6 more.
Type: Journal Article | Journal: Ecology | Year: 2016

The timing of the fruit-set stage (i.e., start and end of fruit set) is crucial in a plants life cycle, but its response to temperature change is still unclear. We investigated the timing of seven phenological events, including fruit-set dates during 3yr for six alpine plants transplanted to warmer (approximately +3.5C in soils) and cooler (approximately -3.5C in soils) locations along an altitudinal gradient in the Tibetan area. We found that fruit-set dates remained relatively stable under both warming and cooling during the 3-yr transplant experiment. Three earlier phenological events (emergence of first leaf, first bud set, and first flowering) and two later phenological events (first leaf coloring and complete leaf coloring) were earlier by 4.8-8.2d/C and later by 3.2-7.1d/C in response to warming. Conversely, cooling delayed the three earlier events by 3.8-6.9d/C and advanced the two later events by 3.2-8.1d/C for all plant species. The timing of the first and/or last fruit-set dates, however, did not change significantly compared to earlier and later phenological events. Statistical analyses also showed that the dates of fruit set were not significantly correlated or had lower correlations with changes of soil temperature relative to the earlier and later phenological events. Alpine plants may thus acclimate to changes in temperature for their fruiting function by maintaining relatively stable timings of fruit set compared with other phenological events to maximize the success of seed maturation and dispersal in response to short-term warming or cooling.


PubMed | CAS Northwest Institute of Plateau Biology, CAS Institute of Tibetan Plateau Research, Binhai Research Institute in Tianjin and Japan Institute for Environmental Sciences
Type: | Journal: Ecology | Year: 2016

Our ability to predict how temperature modifies phenology at the community scale is limited by our lack of understanding of responses by functional groups of flowering plants. These responses differ among species with different life histories. We performed a reciprocal transplant experiment along four elevation gradients (e.g. 3200, 3400, 3600 and 3800 m) to investigate the effects of warming (transferred downward) and cooling (transferred upward) on plant flowering functional groups and community phenological sequences (i.e. seven phenological events). Warming significantly decreased early-spring-flowering (ESF) plant coverage and increased mid-summer-flowering plant (MSF) coverage, while cooling had the opposite effect. All community phenological events were advanced by warming and delayed by cooling except for the date of complete leaf-coloring, which showed the opposite response. Warming and cooling could cause greater advance or delay in early-season phenological events of the community through increased coverage of MSF species, and warming could delay late-season phenological events of the community by increased coverage of ESF species. These results suggested that coverage change of flowering functional groups in the community induced by temperature change could mediate the responses of the community phenological events to temperature change in the future. The response of phenological events to temperature change at the species-level may not be sufficient to predict phenological responses at the community-level due to phenological compensation between species in the community. This article is protected by copyright. All rights reserved.


Liu Y.,Tianjin University of Science and Technology | Yang G.,Tianjin University of Science and Technology | Xu G.,Binhai Research Institute in Tianjin
Journal of Information and Computational Science | Year: 2010

Randomness and fuzziness are two basic types of uncertainty. However, a lot of surveys showed that some kind of uncertainty cannot be modeled by randomness nor fuzziness. So in this paper, the states of components and systems are considered as uncertain variables. Then the uncertain coherent system is defined and its structural properties are proposed. Moreover, the dual of uncertain coherent system is introduced and some useful theorems are given. Finally, the reliability of uncertain coherent system is arrived and some examples are given. Copyright © 2010 Binary Information Press.

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