Wookey P A, Robinson C H, Parsons A N, Welker J M, Press M C, Callaghan T V, Lee J A
Department of Biological Sciences, University of Exeter, Hatherly Laboratories, Prince of Wales Road, EX4 4PS, Exeter, UK.
Centre for Arctic Biology, Department of Animal and Plant Science, University of Sheffield, P.O. Box 601, S10 2UQ, Sheffield, UK.
Oecologia. 1995 Jun;102(4):478-489. doi: 10.1007/BF00341360.
Opportunities exist in high Arctic polar semidesert communities for colonisation of unvegetated ground by long-lived clonal plants such as Dryas octopetala. This can be achieved by lateral spread of vegetative ramets, or by sexual reproduction and seedling recruitment. The objectives of this study were (1) to determine whether these two means of proliferation show differential sensitivity to contrasting components of the abiotic environment (temperature, soil nutrient and water availability) and (2) to evaluate the potential for D. octopetala to respond to climate change by an increase in cover and biomass in polar semi-desert communities. Factorial environmental manipulations of growing season temperature, soil nutrient and water status were conducted over 3 years at a polar semi-desert community in Svalbard, Norway (78°56.12'N, 11°50.4'E) and both clonal and sexual reproductive performance, together with instantaneous net photosynthesis (P), were recorded during the third season (1993). D. octopetala capitalised rapidly on an amelioration in the availability of inorganic nutrients (N, P and K) by an expansion in leaf area and biomass supported by increased P per unit leaf weight, and by apparent luxury uptake of nutrients (particularly P). Several facets of sexual reproductive development and seed viability were markedly improved by elevated temperatures or soil nutrient availability. Thus although D. octopetala is a long-lived clonal plant, with many traits characteristic of stress resistance syndrome, it showed considerable phenotypic plasticity in response to environmental manipulations. The results support the hypothesis that clonal growth confers survival potential during unfavourable years, together with the ability to capitalise on nutrient flushes and recycle nutrients internally. Continued investment in sexual reproduction ensures that seed setting is successful during favourable years, even if these occur infrequently. Cimate warming in the high Arctic could thus result in changes in the cover, biomass and the relative significance of clonal versus sexual proliferation of D. octopetala (and thus the genetic diversity of the population) but the long-term responses will probably be constrained by lack of available nutrients.
在北极极地半荒漠群落中，存在着一些机会，可供像八瓣仙女木这样的长寿克隆植物在无植被的土地上定殖。这可以通过无性分株的横向扩展，或者有性繁殖和幼苗补充来实现。本研究的目的是：（1）确定这两种繁殖方式对非生物环境的不同组成部分（温度、土壤养分和水分有效性）是否表现出不同的敏感性；（2）评估八瓣仙女木通过增加极地半荒漠群落中的覆盖度和生物量来应对气候变化的潜力。在挪威斯瓦尔巴群岛的一个极地半荒漠群落（北纬78°56.12'，东经11°50.4'），对生长季节温度、土壤养分和水分状况进行了为期3年的因子环境操纵实验，并在第三个季节（1993年）记录了无性和有性繁殖表现以及瞬时净光合速率（P）。八瓣仙女木通过扩大叶面积和生物量迅速利用无机养分（氮、磷和钾）有效性的改善，这是由单位叶重的光合速率增加以及明显的养分奢侈吸收（特别是磷）所支持的。温度升高或土壤养分有效性提高显著改善了有性生殖发育和种子活力的几个方面。因此，尽管八瓣仙女木是一种长寿的克隆植物，具有许多抗逆综合征的特征，但它对环境操纵表现出了相当大的表型可塑性。结果支持了这样的假设，即克隆生长在不利年份赋予了生存潜力，同时具有利用养分脉冲和在内部循环养分的能力。对有性繁殖的持续投入确保了在有利年份即使很少出现也能成功结籽。因此，北极地区的气候变暖可能会导致八瓣仙女木的覆盖度、生物量以及克隆与有性繁殖的相对重要性（从而种群的遗传多样性）发生变化，但长期反应可能会受到可用养分缺乏的限制。
