Northern temperate ecosystems are experiencing warmer and more variable winters, trends that are expected to continue into the foreseeable future. Despite this, most studies have focused on climate change impacts during the growing season, particularly when comparing responses across different vegetation cover types. Here we examined how a perennial grassland and adjacent mixed forest ecosystem in New Hampshire, United States, responded to a period of highly variable winters from 2014 through 2017 that included the warmest winter on record to date. In the grassland, record‐breaking temperatures in the winter of 2015/2016 led to a February onset of plant growth and the ecosystem became a sustained carbon sink well before winter ended, taking up roughly 90 g/m2more carbon during the winter to spring transition than in other recorded years. The forest was an unusually large carbon source during the same period. While forest photosynthesis was restricted by leaf‐out phenology, warm winter temperatures caused large pulses of ecosystem respiration that released nearly 230 g C/m2from February through April, more than double the carbon losses during that period in cooler years. These findings suggest that, as winters continue to warm, increases in ecosystem respiration outside the growing season could outpace increases in carbon uptake during a longer growing season, particularly in forests that depend on leaf‐out timing to initiate carbon uptake. In ecosystems with a perennial leaf habit, warming winter temperatures are more likely to increase ecosystem carbon uptake through extension of the active growing season. Our results highlight the importance of understanding relationships among antecedent winter conditions and carbon exchange across land‐cover types to understand how landscape carbon exchange will change under projected climate warming.
Increases in temperature related to global warming have important implications for organismal fitness. For ectotherms inhabiting temperate regions, ‘winter warming’ is likely to be a key source of the thermal variation experienced in future years. Studies focusing on the active season predict largely positive responses to warming in the reptiles; however, overlooking potentially deleterious consequences of warming during the
- NSF-PAR ID:
- 10373250
- Publisher / Repository:
- Springer Science + Business Media
- Date Published:
- Journal Name:
- Oecologia
- Volume:
- 200
- Issue:
- 1-2
- ISSN:
- 0029-8549
- Page Range / eLocation ID:
- p. 259-271
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Increasing temperatures during climate change are known to alter the phenology across diverse plant taxa, but the evolutionary outcomes of these shifts are poorly understood. Moreover, plant temperature‐sensing pathways are known to interact with competition‐sensing pathways, yet there remains little experimental evidence for how genotypes varying in temperature responsiveness react to warming in realistic competitive settings.
We compared flowering time and fitness responses to warming and competition for two near‐isogenic lines (NILs) of
Arabidopsis thaliana transgressively segregating temperature‐sensitive and temperature‐insensitive alleles for major‐effect flowering time genes. We grew focal plants of each genotype in intraspecific and interspecific competition in four treatments contrasting daily temperature profiles in summer and fall under contemporary and warmed conditions. We measured phenology and fitness of focal plants to quantify plastic responses to season, temperature and competition and the dependence of these responses on flowering time genotype.The temperature‐insensitive NIL was constitutively early flowering and less fit, except in a future‐summer climate in which its fitness was higher than the later flowering, temperature‐sensitive NIL in low competition. The late‐flowering NIL showed accelerated flowering in response to intragenotypic competition and to increased temperature in the summer but delayed flowering in the fall. However, its fitness fell with rising temperatures in both seasons, and in the fall its marginal fitness gain from decreasing competition was diminished in the future.
Functional alleles at temperature‐responsive genes were necessary for plastic responses to season, warming and competition. However, the plastic genotype was not the most fit in every experimental condition, becoming less fit than the temperature‐canalized genotype in the warm summer treatment.
Climate change is often predicted to have deleterious effects on plant populations, and our results show how increased temperatures can act through genotype‐dependent phenology to decrease fitness. Furthermore, plasticity is not necessarily adaptive in rapidly changing environments since a nonplastic genotype proved fitter than a plastic genotype in a warming climate treatment.
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Abstract Changes in seasonality associated with climate warming (e.g. temperature, growing season duration) are likely to alter invertebrate prey biomass and availability in aquatic ecosystems through direct and indirect influences on physiology and phenology, particularly in arctic lakes. However, despite warmer thermal regimes, photoperiod will remain unchanged such that potential shifts resulting from longer and warmer growing seasons could be limited by availability of sunlight, especially at lower trophic levels. Thus, a better understanding of warming effects on invertebrate prey throughout the growing season (e.g. early, peak, late) is important to understand arctic lake food‐web dynamics in a changing climate.
Here, we use a multifaceted approach to evaluate prey availability to predators in lakes of arctic Alaska. In a laboratory mesocosm experiment, we measured different metrics of abundance for snails (
Lymnaea elodes ) and zooplankton (Daphnia middendorffiana ) across three time periods (early, mid‐ and late growing season) and across three temperature and photoperiod treatments (control, increased temperature and increased temperature × photoperiod). Additionally, we used generalised additive models and generalised additive mixed‐effects models to relate long‐term empirical observations of zooplankton biomass (1983–2015) to observed temperature regimes in an arctic lake. We then simulated zooplankton biomass for the warmest temperature observations across the growing season to inform likely zooplankton biomass regimes under future change.We observed variable responses by snails and zooplankton across experiments and treatments. Early in the growing season, snail development was accelerated at multiple life stages (e.g. egg and juvenile). In mid‐season, in accordance with warmer temperatures, we observed significantly increased
Daphnia abundances. However, in the late season,Daphnia appeared to be limited by photoperiod. Confirming our experimental results, our models of zooplankton biomass showed an increase of nearly 20% in warmer years. Further, these model estimates could be conservative as the consumptive demand of fishes may increase in warmer years as well.Overall, our results highlight the importance of interactive effects of temperature and seasonality. Based primarily on temperature, we can readily predict the response of fish metabolism in warmer temperatures. However, in this context, we generally require a better understanding of climate‐driven responses of important invertebrate prey resources. Our results suggest invertebrate prey biomass and availability are likely to respond positively with climate change based on temperature and seasonality, as well as proportionally to the metabolic requirements of fish predators. While further research is necessary to understand how other food‐web components will respond climate change, our findings suggest that the fish community at the top of arctic lake food webs will have adequate prey base in a warming climate.
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Summary Climate change causes both temporal (e.g. advancing spring phenology) and geographic (e.g. range expansion poleward) species shifts, which affect the photoperiod experienced at critical developmental stages (‘experienced photoperiod’). As photoperiod is a common trigger of seasonal biological responses – affecting woody plant spring phenology in 87% of reviewed studies that manipulated photoperiod – shifts in experienced photoperiod may have important implications for future plant distributions and fitness. However, photoperiod has not been a focus of climate change forecasting to date, especially for early‐season (‘spring’) events, often assumed to be driven by temperature. Synthesizing published studies, we find that impacts on experienced photoperiod from temporal shifts could be orders of magnitude larger than from spatial shifts (1.6 h of change for expected temporal vs 1 min for latitudinal shifts). Incorporating these effects into forecasts is possible by leveraging existing experimental data; we show that results from growth chamber experiments on woody plants often have data relevant for climate change impacts, and suggest that shifts in experienced photoperiod may increasingly constrain responses to additional warming. Further, combining modeling approaches and empirical work on when, where and how much photoperiod affects phenology could rapidly advance our understanding and predictions of future spatio‐temporal shifts from climate change.
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