新疆蒿类荒漠土壤种子库萌发及其幼苗定居对增温增雨的适应策略

The adapative mechanism of plant to warming and precipitation changes have an importance effect on combating climatic change, seeking advantages and avoiding disadvantages, and seed germination and its seedling growth of soil seed bank are an importance strategy for plant to adapat climatic change. The fragile Artemisia desert of Xinjiang is the sensitive area of climatic change, and is the frontier of rangland degradation. The studies on seed germination of soil seed bank and its seedling establishment under climatic change are an importance instructing effect on vegetative recovery and succession of degradated Artemisia desert in the future. In order to discover change law and adpative mechnism of seed germination and its seedling growth of soil seed bank to climate changes under "warming-wetting" trend of Xinjiang climate, the characteristics of soil seed bank seed germination pattern and seedling establishment of moderate degradated Artemisia desert under different warming, increasing percipitation and interactive of warming and percipitation are monitored by laborary simulating control. At the same time, in order to predict the succession of Artemisia desert community in the future, the coupling relationship between the exiting vegetation in the field and germination species of soil seed bank, the forming community of germination seedling are analyses. Those studies will not only provide the science base on the vegetative recovery of degradated Artemisia desert and combating climate changes in the future, but also enrich and develop the vegetative community succession theory under climatic change in grassland.

全球增温、降水格局改变已成为共识，揭示未来气候条件下植物适应性对人类应对气候变化、趋利避害具有重要意义，而土壤种子库内种子的萌发及幼苗定居是植物响应气候变化的重要途径。处于退化前沿的新疆蒿类荒漠草地生境脆弱，对气候变化敏感，未来气候变化下其土壤种子库种子萌发及幼苗定居对该区域植被的恢复与演替具有重要指示作用。针对新疆气候向“暖、湿”方向发展的现状，以中度退化蒿类荒漠为对象，采用野外实地调查与室内模拟控制法，通过对不同增温、增雨及其协同作用下土壤种子库种子萌发格局及其幼苗定居特征的监测，明确其对气候变化的响应规律，揭示其适应机制；通过野外现存植物群落、可萌发土壤种子库、当年幼苗定居群落间的耦合关系分析，阐明增温增雨情景下蒿类荒漠群落的演替趋势，最终为未来退化蒿类荒漠植被的恢复及应对气候变化的研究提供科学依据，并丰富和发展气候干扰下草地植物群落替理论。

全球增温、降水格局改变已成为共识，而土壤种子库种子萌发及存活是植物响应气候变化的重要途径之一。针对新疆气候向 “暖、湿”方向发展趋势，研究了增温增雨及协同作用对中度退化蒿类荒漠土壤种子库种子萌发、幼苗定居的响应规律，并通过群落相似性分析揭示了其所形成群落的演替趋势，这对应对未来气候变化具重要有意义。结果表明：（1）降水增加促进了蒿类荒漠草地土壤种子库种子的萌发，利于退化草地恢复。随降水增加，0-10cm土层种子库萌发的物种数、萌发总密度、可萌发种子库及存活幼苗的群落多样性（Shannon-Wiener指数、Pielou指数、Patrick指数）、幼苗群落数量特征总体呈增加趋势。与对照比，0-5cm土层增水20%、25%处理萌发物种数、总密度依次显著增加1.5-2.6倍、55%-248%，5-10 cm土层增加相对较低。无论降水增加与否，0-10cm土层伊犁绢蒿均有萌发，且降水增加显著促进伊犁绢蒿、木地肤、串珠老鹳草的萌发。蒿类荒漠可萌发土壤种子库与地上现存植被Sorensen相似性随降水增加呈增加趋势，降水增加 ≥20％处理高于降水增加≤15％处理。土壤种子库可萌发种子密度具明显的空间异质性，受取样位置及降水交互影响，年度间种子萌发有较大波动性。（2）温度增加抑制了蒿类荒漠土壤种子库种子萌发，可能不利于退化草地恢复。 随温度增加，0-10 cm土层可萌发土壤种子库物种数、萌发总密度、多年生草本及双子叶植物萌发数、可萌发种子库及定居幼苗的群落多样性均呈下降趋势，但适度增温可促进一年生草本植物的萌发，而幼苗群落数量特征呈先增后降趋势，增温4℃最高。与对照比，增温6℃处理0-10cm土层萌发物种数及萌发总密度显著降低33.3%-75.0%。蒿类荒漠可萌发土壤种子库、定居幼苗与地上现存植被群落相似性随温度增加呈下降趋势，但适度增温（≤4℃）与对照间差异不显著。（3）0-10cm土层种子库种子萌发总密度，单、双子叶植物密度及一年生草本、多年生草本、半灌木的萌发密度均不受温度、降水的交互影响，且土壤种子库在适度增温及高增雨组合下种子萌发相对较好。