Impact of climate change on cold hardiness of Douglas‐fir (Pseudotsuga menziesii): environmental and genetic considerations

Abstract

The success of conifers over much of the world's terrestrial surface is largely attributable to their tolerance to cold stress (i.e., cold hardiness). Due to an increase in climate variability, climate change may reduce conifer cold hardiness, which in turn could impact ecosystem functioning and productivity in conifer-dominated forests. The expression of cold hardiness is a product of environmental cues (E), genetic differentiation (G), and their interaction (G × E), although few studies have considered all components together. To better understand and manage for the impacts of climate change on conifer cold hardiness, we conducted a common garden experiment replicated in three test environments (cool, moderate, and warm) using 35 populations of coast Douglas-fir (Pseudotsuga menziesii var. menziesii) to test the hypotheses: (i) cool-temperature cues in fall are necessary to trigger cold hardening, (ii) there is large genetic variation among populations in cold hardiness that can be predicted from seed-source climate variables, (iii) observed differences among populations in cold hardiness in situ are dependent on effective environmental cues, and (iv) movement of seed sources from warmer to cooler climates will increase risk to cold injury. During fall 2012, we visually assessed cold damage of bud, needle, and stem tissues following artificial freeze tests. Cool-temperature cues (e.g., degree hours below 2 °C) at the test sites were associated with cold hardening, which were minimal at the moderate test site owing to mild fall temperatures. Populations differed 3-fold in cold hardiness, with winter minimum temperatures and fall frost dates as strong seed-source climate predictors of cold hardiness, and with summer temperatures and aridity as secondary predictors. Seed-source movement resulted in only modest increases in cold damage. Our findings indicate that increased fall temperatures delay cold hardening, warmer/drier summers confer a degree of cold hardiness, and seed-source movement from warmer to cooler climates may be a viable option for adapting coniferous forest to future climate.

Tolerance to multiple climate stressors: a case study of Douglas‐fir drought and cold hardiness

“…Drought hardiness and cold hardiness were assessed in related studies in 2012 at three of the common gardens (cool, moderate, and warm) on 35 populations (Bansal et al. ,b). For the current analyses, data from the cool and warm gardens were used because they represented the extremes with regard to annual temperature and precipitation.…”

“…Bud, stem, and needle damage were assessed following artificial freeze tests (Bansal et al. ), with lower cold damage corresponding to greater cold hardiness. Four test temperatures were used to produce a range of damage scores.…”

“…The primary purpose of this analysis was to understand the overall pattern of covariation in tolerance to stress, as opposed to individual traits associated with drought or cold hardiness (which are covered in detail in Bansal et al. ,b). We used trait values for drought and cold hardiness from the warm and cool gardens, respectively, because innate variation in tolerances to drought and cold among populations is most strongly expressed in response to the dry and cool climates of those respective gardens.…”

“…) and cold hardiness (Bansal et al. ) of Douglas‐fir. When wild populations of Douglas‐fir experience environmental stress under natural conditions, then genetics, environment, and the interactions all influence the observed in situ expressions of stress tolerance traits, which are the ultimate drivers of persistence through environmental stress.…”

The Favored Mechanism for Coping with Acute Cold Stress: Upregulation of miR-210 in Rats

“…Long - or short-term cold exposure may lead to growth retardation [1], loss of genetic information [2] and immune suppression [3]. In general, cold stress is classified into acute cold stress (ACS) and chronic cold stress according to exposure time to low environmental temperature [4].…”