Warming experiments underpredict plant phenological responses to climate change

Division of Biological Sciences, University of California San Diego, 9500 Gilman Drive 0116, La Jolla, California 92093, USA.
Nature (Impact Factor: 41.46). 05/2012; 485(7399):494-7. DOI: 10.1038/nature11014
Source: PubMed


Warming experiments are increasingly relied on to estimate plant responses to global climate change. For experiments to provide meaningful predictions of future responses, they should reflect the empirical record of responses to temperature variability and recent warming, including advances in the timing of flowering and leafing. We compared phenology (the timing of recurring life history events) in observational studies and warming experiments spanning four continents and 1,634 plant species using a common measure of temperature sensitivity (change in days per degree Celsius). We show that warming experiments underpredict advances in the timing of flowering and leafing by 8.5-fold and 4.0-fold, respectively, compared with long-term observations. For species that were common to both study types, the experimental results did not match the observational data in sign or magnitude. The observational data also showed that species that flower earliest in the spring have the highest temperature sensitivities, but this trend was not reflected in the experimental data. These significant mismatches seem to be unrelated to the study length or to the degree of manipulated warming in experiments. The discrepancy between experiments and observations, however, could arise from complex interactions among multiple drivers in the observational data, or it could arise from remediable artefacts in the experiments that result in lower irradiance and drier soils, thus dampening the phenological responses to manipulated warming. Our results introduce uncertainty into ecosystem models that are informed solely by experiments and suggest that responses to climate change that are predicted using such models should be re-evaluated.

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    • "Climate warming has led to a renewed interest in plant phenology (the timing of periodic life-history events, such as bud break), as vegetation is increasingly observed to become active earlier in spring (Wolkovich et al., 2012; Richardson et al., 2013) and – less frequently – to have a delayed senescence in autumn (Natali et al., 2011). Evidence for this comes from local to landscape scales, with methods ranging from single shoot observations to remote sensing (Pau et al., 2011; Wolkovich et al., 2012). Changes in phenology and growing season length are expected to be most pronounced in regions with a strong seasonal climate (Pau et al., 2011), such as the Arctic, where annual cycles are constrained by a short growing season, and where current and predicted warming rates are highest (ACIA, 2004). "
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    ABSTRACT: There is compelling evidence from experiments and observations that climate warming prolongs the growing season in arctic regions. Until now, the start, peak, and end of the growing season, which are used to model influences of vegetation on biogeochemical cycles, were commonly quantified using above-ground phenological data. Yet, over 80% of the plant biomass in arctic regions can be below ground, and the timing of root growth affects biogeochemical processes by influencing plant water and nutrient uptake, soil carbon input and microbial activity. We measured timing of above- and below-ground production in three plant communities along an arctic elevation gradient over two growing seasons. Below-ground production peaked later in the season and was more temporally uniform than above-ground production. Most importantly, the growing season continued c. 50% longer below than above ground. Our results strongly suggest that traditional above-ground estimates of phenology in arctic regions, including remotely sensed information, are not as complete a representation of whole-plant production intensity or duration, as studies that include root phenology. We therefore argue for explicit consideration of root phenology in studies of carbon and nutrient cycling, in terrestrial biosphere models, and scenarios of how arctic ecosystems will respond to climate warming.
    New Phytologist 09/2015; DOI:10.1111/nph.13655 · 7.67 Impact Factor
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    • "During climate change, the native species may be out-competed by faster growing, more plastic and aggressive species extending their range (Hellmann et al. 2008, Walther et al. 2009) or there is a possibility of changing growth and habitat patterns of native species under resource changed environment (Wolkovich et al. 2012, Ranjitkar et al. 2013). For decades, understanding phenotypic plasticity of any plant has been instrumental in determining its recruitment/spread over a geographical area (Richards et al. 2006, Funk and Vitousek 2007). "
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    ABSTRACT: To understand the spread of native populations of Lepidium latifolium growing in different altitudes in Ladakh region of Western Himalayas, photosynthetic and fluorescence characteristics were evaluated in relation to their micro-environment. Three sites representing sparsely populated (SPS), moderately populated (MPS) and densely populated site (DPS) were selected. Results showed that the DPS had higher photosynthetic accumulation than MPS and SPS. The higher transpiration rate at DPS despite lower VpdL and higher relative humidity suggest that the regulation of its leaf temperature by evaporative cooling. Intrinsic soil parameters like water holding capacity and nutrient availability also play crucial role in higher biomass here. The quantum efficiency of PSII photochemistry (Fv /Fm , NPQ, ɸPSII ) and light curve at various PPFD's suggests better light harvesting potential and light compensation point at DPS than the other two sites. Concomitantly, plants at SPS had significantly higher lipid peroxidation, suggesting a stressful environment, and higher induction of antioxidative enzymes. Metabolic content of reduced glutathione also suggests an efficient mechanism in DPS and MPS than SPS. High light intensities at MPS are managed by specialized contrive of carotenoid pigments and PsBs gene product. Large pool of violaxanthin and lutein plays an important role in this response. It is suggested that L. latifolium is present as 'sleeper weed' that has inherent biochemical plasticity involving multiple processes in Western Himalayas. Its potential spread is linked to site-specific micro-environment, whereby, it prefers flat valley bottoms with alluvial fills having high water availability, and has little or no altitudinal effect. This article is protected by copyright. All rights reserved.
    Physiologia Plantarum 08/2015; DOI:10.1111/ppl.12362 · 3.14 Impact Factor
    • "The Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) stated that phenology can be used as a simple and integrative indicator on how species and ecosystems respond to climate change (Parry et al. 2007). Results from phenological studies around the world clearly demonstrate the impact of increasing temperatures on plants and animals and the feedback of shifting phenology to climate change (e.g., Penuelas et al. 2009; Walther 2010; Wolkovich et al. 2012; Richardson et al. 2013). Many phenological models have been developed to simulate the relationships between plant phenology and environmental factors (Schwartz and Chen 2002; Vitasse et al. 2011; Chen and Xu 2012; Chuine et al. 2013). "
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    ABSTRACT: It is important to accurately determine the response of spring and autumn phenology to climate change in forest ecosystems, as phenological variations affect carbon balance, forest productivity, and biodiversity. We observed phenology intensively throughout spring and autumn in a temperate deciduous woodlot at Milwaukee, WI, USA, during 2007-2012. Twenty-four phenophase levels in spring and eight in autumn were recorded for 106 trees, including white ash, basswood, white oak, boxelder, red oak, and hophornbeam. Our phenological progression models revealed that accumulated degree-days and day length explained 87.9-93.4 % of the variation in spring canopy development and 75.8-89.1 % of the variation in autumn senescence. In addition, the timing of community-level spring and autumn phenophases and the length of the growing season from 1871 to 2012 were reconstructed with the models developed. All simulated spring phenophases significantly advanced at a rate from 0.24 to 0.48 days/decade (p ≤ 0.001) during the 1871-2012 period and from 1.58 to 2.00 days/decade (p < 0.02) during the 1970-2012 period; two simulated autumn phenophases were significantly delayed at a rate of 0.37 (mid-leaf coloration) and 0.50 (full-leaf coloration) days/decade (p < 0.01) during the 1970-2012 period. Consequently, the simulated growing season lengthened at a rate of 0.45 and 2.50 days/decade (p < =0.001), respectively, during the two periods. Our results further showed the variability of responses to climate between early and late spring phenophases, as well as between leaf coloration and leaf fall, and suggested accelerating simulated ecosystem responses to climate warming over the last four decades in comparison to the past 142 years.
    International Journal of Biometeorology 07/2015; DOI:10.1007/s00484-015-1031-9 · 3.25 Impact Factor
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