Patterns of cold-hardiness in a stenothermic environment: The antarctic

The development of cold hardiness in coniferous species is, as in most woody species, under the control of the climatic environment that prevails where the trees are grown. Although there are interspecific differences in the capacity for cold hardening and a wide range of variation exists, it is likely that there is a generic process for the plants to cold harden and deharden. In this chapter we describe the seasonal changes in cold hardiness in conifer species and use this seasonality of hardening and dehardening as a basis to discuss the quantitative aspects of environmental control of the development and loss of cold hardiness. Finally, these quantitative relationships are the bases for development of predictive models of cold hardening and dehardening.

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.

► Cold hardiness of Pinus nigra shows local adaptation to climate at its geographic origin. ► Winter cold hardiness increases with summer drought and summer warming. ► Cold hardiness is related to the content of soluble carbohydrates and composition of fatty acids and alkanes. ► P. nigra shows similar cold hardiness as the native Central European forest trees. Adaptation to the adverse effects of climate change is being investigated more and more through the introduction of species from warmer and drier climates, such as the (sub-) mediterranean Pinus nigra to dry sites in temperate Central Europe. Winter survival, however, may pose a serious threat to this strategy as cold extremes, which naturally determine the poleward range limits of forest trees, are not expected to follow the general warming trend in the near future. Here, juveniles of P. nigra from eight provenances throughout Europe were exposed to different climate change scenarios (factorial combinations of 42 days of drought and warming by 1.6 °C) in a common garden experiment in Bayreuth, Germany. Cold hardiness (LT50) was determined by the Relative Electrolyte Leakage method (REL) in two consecutive winters. Cold hardiness of foliage differed by 10 °C between the provenances studied and a local adaptation to minimum temperature was found. Cold hardiness was further affected by extreme summer drought, increasing cold hardiness by 3.9 °C on average in the subsequent winter, and by summer warming, increasing cold hardiness by 3.4 °C. Year-round warming had no significant effect on cold hardiness. Cold hardiness was related to the content of soluble carbohydrates and to the composition of fatty acids and alkanes in the needles. Juveniles of P. nigra exhibited a comparable cold hardiness as juveniles of species native to Central Europe ( Pinus sylvestris , Picea abies , Fagus sylvatica and Quercus petraea ) under the same climatic conditions. Cold hardiness of the fine roots of P. nigra averaged −16.5 °C compared to −23.8 °C on average for needles. Our results imply that the cold hardiness of the foliage is adaptive to both long-term growing conditions at the seed origin (genetic heritage) and short-term alterations of these conditions (individual plasticity), while first hints suggest that cold hardiness of the roots is high and might not be adaptive. For P. nigra , below- and above-ground cold hardiness of selected provenances in mid-winter appear suitable for cultivation in temperate regions.

Insects as cold-blooded animal,its proliferation face challenges about how live through the long and cold winter.To live through the winter safely,insects must adapt to the low temperature in winter,and enhancing the cold hardiness is an important adaptive seasonal mechanism.In recent years,researches about insects cold hardiness develop continuously,which contain the factors that influence cold hardiness,cold hardiness mechanisms and so on.The factor include environmental factors such as seasonal changes and differences in latitude or altitude,and the insect's own developmental stage,diapause states and so on.

Background and Aims Grapevine production in cool climates is limited by aspects of winter survival and frost risk. Cold hardiness-related traits are key to future viticultural sustainability as climate variations, including acute cold events and frost, are predicted to increase even in traditional cultivation regions. This study examines the variation in dormant bud cold hardiness (supercooling) and dormancy (chilling requirement) in 43 different genotypes of the wild grapevine species Vitis riparia, the dominant wild species used to incorporate cold hardiness traits into new hybrid grapevine cultivars. Methods and Results Cold hardiness was evaluated bi-weekly in 2 years using measures of low temperature exotherms. Whole winter responses were modelled to determine significant factors affecting cold hardiness and determine genotypic differences. Results demonstrate significant differences in supercooling ability and deacclimation rate (loss of cold hardiness) between genotypes. Conclusions This study determined that genotypic differences contribute to initial differences in cold hardiness. However, data modelling suggests that midwinter cold hardiness changes are driven by environment as all Vitis riparia tested in this study respond to temperature in the same manner during the endodormant period of winter. In contrast, responses to warming temperature during ecodormancy are significantly different by genotype. Significance of the Study This study has demonstrated that these two traits interact to determine differences in early versus late winter cold hardiness and help identify breeding germplasm with delayed loss of cold hardiness.

Cold hardiness evaluation is important for screening woody species in cold areas. We compared cold hardiness by estimating the 50% lethal temperature (LT 50 ) using electrolyte leakage test (ELLT 50 ) and triphenyltetrazolium chloride test (TTCLT 50 ) for 26 woody species in the Bashang region of China. One-year-old shoots were collected in January and exposed to five subfreezing temperatures in a programmable temperature and humidity chamber. LT 50 was estimated by fitting relative electrolyte leakage and percentage of dead tissue against test temperature. For all tested species, triphenyltetrazolium chloride (TTC) staining of the pith was weak and the cambium TTCLT 50 was lower than the extreme minimum temperature (−37 °C) recorded in the region. The cambium TTCLT 50 and the sd were lower than that for the phloem and xylem. The phloem TTCLT 50 was lower than the xylem TTCLT 50 , and the two sd s were similar. The ELLT 50 showed no significant correlation with any TTCLT 50. For most species, the ELLT 50 was higher than the cambium and phloem TTCLT 50 and was not significant different with the xylem TTCLT 50 . The ELLT 50 showed higher sd than any tissue TTCLT 50. Based on results obtained in this study, when choosing cold hardiness of single stem tissue as an indicator for screening woody species, the xylem should be considered first, followed by the phloem; the cambium and pith were unsuitable. The cold hardiness estimated by ELLT 50 was more suitable as indicator for screening woody species than that of stem tissue in winter estimated by TTCLT 50 .