CO_2浓度和降水协同作用对短花针茅生长的影响

Effects of interactive CO_2 concentration and precipitation on growth characteristics of Stipa breviflora

关于二氧化碳(CO2)浓度和降水等单因子变化对植物生长的影响研究已很多,但多因子协同作用的影响研究仍较少,制约着植物对全球变化响应的综合理解与预测。利用开顶式生长箱(OTC)模拟研究了CO2浓度升高(450和550μmol/mol)和降水量变化(-30%、-15%、对照、+15%和+30%)的协同作用对荒漠草原优势植物短花针茅(Stipa breviflora)生长特性的影响。结果表明:550μmol/mol CO2浓度下短花针茅植株的生物量和叶面积较对照显著增加,但450μmol/mol CO2浓度下的变化不明显;降水增多导致植株生物量、叶面积、叶数和株高显著增加;CO2浓度与降水协同作用显著影响短花针茅植株生物量。CO2浓度升高在一定程度上缓解了降水减少对短花针茅的胁迫效应,但降水量减少30%则明显抑制了CO2浓度升高带来的效应。研究结果有助于增进荒漠草原植物对未来气候变化的适应性理解,可为制定荒漠草原应对气候变化的对策提供依据。

Although lot of the studies on the effects of single factor, such as atmospheric CO2 concentration and precipitation, on plant growth characteristics have been done, the effects of interactive CO2 concentration and precipitation on plant growth characteristics have not been studied yet. Those restricted the comprehensive understanding and accurate prediction of the effects of global change on plant growth characteristics. Stipa breviflora is one of the dominant plant species in desert steppe and a kind of forage grass with high quality. Investigating the sensitivity and adaptive capacity of S. breviflora to climate change is significant for maintaining the stabilization of desert ecosystem and the security of stockbreeding. We had studied the effects of increased CO2 concentration and varied precipitation as well as their interactions on the growth characteristics （ such as plant height, leaf area, survival rate, leaf number and biomass, etc. ） of S. breviflora based on the simulation experiment using open-top chambers （OTC） from June to August （the main growing season） in 2011. In this paper, three levels of CO2 concentrations （control, 450 and 550 i.~mol/mol ）, five levels of precipitation （ -30% , -15% , control, ＋15% , and ＋30% based on the average monthly precipitation from 1978 to 2007 in Siziwangqi county, Inner Mongolia） and their interactions were studied. There were six replicates （i. e. , six pots with four plants per pot） for every CO2 concentration treatment and precipitation treatment. The seeds were sowed on April 18th and well watered before control experiment. Then 90 pots of plants with consistent growing vigor were randomly selected and placed into different chambers as different treatments. High-purity CO2 was pumped into those chambers with high CO2 concentration day and night, regulated by a CO2 automatic control system. Each precipitation regime was converted to irrigation amounts of every month and then divided into 10 times to water, i.e. watered every three days after 4：00pro. The chambers were covered in rainy days to avoid extra water input. The whole experimental site was covered with sun-shading net to lower the temperature in chambers at 9：00--16：00 on clear days. Plant heights were measured in late July and late August, respectively. Leaf number, leaf area and biomass were measured at the stage with the biggest biomass. The results indicated that, comparing with the control, the growth characteristics of S. breviflora did not change significantly under 4501xmol/mol CO2 concentration. However, the biomass, plant heights （in July）, leaf area and single leaf area of S. breviflora increased significantly under 550~mol/mol CO2 concentration, while leaf number and plant heights （ in August） did not change significantly. The changes of precipitation obviously affected the biomass, leaf area, leave number, plant height and survival rate of S. breviflora. The interactions of increased CO2 concentration and varied precipitation had significant effects on the biomass of S. breviflora. CO2 fertilization effect could offset the adverse impact induced by decreasing precipitation, but the effect of increasing CO2 concentration would be reduced markedly when the precipitation decreased about 30%. This result would help to understand the adaptation of desert steppe to future climatic change and to make countermeasures to cope with climatic change.