模拟气候变化对2针叶树种种子萌发和幼苗生长的影响

Effects of simulated climate change on seed germination and seedling growth of two coniferous tree species

气候变化影响林木早期生长,设置温度和水分的双因素三水平控制实验,研究山西气候变化对关帝山林区2种针叶树种种子萌发和幼苗生长的影响作用。结果表明,增温2℃和降水量增加20%利于这2树种种子出苗:出苗稳定期提前,出苗率提高;但增温6℃,降水减少20%时,种子出苗稳定期延迟,出苗率降低。气候变化对2树种的影响作用不同:华北落叶松对暖干化气候更敏感,增温或减少降水时,该种幼苗的死亡率大幅增加,苗高降低;温度和降水量变化对油松幼苗存活率和地上生长的影响作用不明显。降水量减少条件下的增温,促进华北落叶松和油松幼苗的主根和侧根伸长。发生土壤干旱时,华北落叶松和油松幼苗生长策略改变,优先满足根系生长。暖干化气候不利于华北落叶松种群的更新,生长季高温降低了幼苗适应性,即使降水量增加亦不能缓解。

[Background]Early development stages of trees are expected to be more sensitive to climate change,and represent a major bottleneck to plant community recruitment. In North China,drought index had increased dramatically since 1990 s,understanding on seedling＇s response to anticipated decrease in water availability is urgently needed. Larix principis-rupprechtii and Pinus tabulaeformis are two dominant coniferous tree species in North China,and play significant ecological roles in water conservation.[Methods] We collected seeds of these two species from Guandi Mountain,Shanxi Province,and conducted a controlled greenhouse experiment to investigate how climate changes（ warming and precipitation change） would affect their seedling emergence and growth. Three levels were set for both temperature and water supply. Temperature levels were monthly mean temperature（ T0） over the past 15years（ 1999-2013）,increased by 2 ℃（ T1） and by 6 ℃（ T2）. Water supply levels were monthly mean precipitation（ W） over past the 15 years（ 1999-2013）,reduction by 20%（ W-） and addition by 20%（ W＋）. A two-way ANOVA was used to compare seedling growth（ including seedling emergence percentage,needle length,height,length of main root,number of lateral root,and length of lateral root）between the two treatments to the species. If the interaction was tested to be significant（ P 〈0. 05）,oneway ANOVA was used to test the effects of water treatments on seedling indexes,and multiple comparison was used otherwise. The least significant difference method（ LSD） was used to test the significantdifferences of all data at level of 0. 05. [Results] Seed germination of the two species was affected by temperature and precipitation changes. Seedling ＇s stable germination time reduced and seedling emergence percentage improved by increased temperature of 2 ℃ and water addition. However,in the condition of increased temperature of 6 ℃ or water reduction,stable germination time of seedling delayed and seedling emergence percentage decreased. Seedlings of the two species presented different responses to the climate change. L. principis-rupprechtii was affected more greatly by warming and drying climate than P. tabulaeformis. Seedling morality of L. principis-rupprechtii increased sharply and seedling height decreased by higher temperature and water reduction. The changes from increased temperature or precipitation showed no significant effects on seedling survival and aboveground-growth of P.tabulaeformis. Underground growth of both L. principis-rupprechtii and P. tabulaeformis increased by longer primary and lateral roots. [Conclusions] Soil drought was induced by dramatically increased temperature and reduced precipitation,which resulted in adaptive strategy of the two species by reducing aboveground growth and giving priority to root growth. Seedlings showed an interspecific variation of response to water deficit. L. principis-rupprechtii was more sensitive to climate change than P.tabulaeformis. The regeneration of L. principis-rupprechtii was inhibited by warming and drying climate.The seedling growth was negatively affected by highly increased temperature in growing period,and it could not be improved by water addition.