本文在全球气候变化的背景下,利用开顶式生长室(OTC, open top chamber)于2011与2012年进行模拟增温,同时实施降水量增加的处理,研究增温与增水处理及其交互作用对内蒙古典型草原优势植物克氏针茅光合作用的影响。于2012年生长季使用Li-6400对克氏针茅叶片的各光合作用特征参数进行测量。结果表明,增温明显降低克氏针茅的叶片光合速率(P_n)与气孔导度(G_s),并存在明显季节变化趋势。在7月与9月增温分别使P_n降低17%和27%,使G_s分别降低24%和32%。同时增温降低克氏针茅蒸腾速率(T_r)、叶绿素含量、核酮糖-1,5-二磷酸(RuBP)羧化的最大速率(V_(cmax))、RuBP再生能力的最大速率(J_(max))、表观量子效率(AQE)与最大光合速率(P_nmax),但使水分利用效率(WUE)增加16.5%。降水增加对高温条件下的光合作用具有补偿效应。降水增加促进了克氏针茅的P_n、G_s、T_r、叶绿素含量、V_(cmax)、J_(max)、AQE与P_nmax,但对WUE影响不明显。温度水分对克氏针茅光合作用与WUE的影响,是由气孔开合与非气孔因素共同引起的。增温与增水条件下克氏针茅气孔导度在光合速率与蒸腾速率间存在权衡。温度与降水增加显著影响克氏针茅叶片各光合特性参数,但二者交互作用对植物光合作用无显著影响。
英文摘要:
This study was conducted to examine the interactive effects of climate warming and changing precipitation on photosynthetic parameters of Stipa krylovii to evaluate the effects of future climate change on a typical steppe environment. Open top chambers (OTCs) were used to simulate warming +2℃, based on the local temperature increase from 1961 to 2010 (IPCC, 2007) and precipitation enhancement of +20%, based on the local average monthly precipitation from 1961-2010. The photosynthetic parameters were measured by a portable gas exchange system (LI-6400) in the growing season of 2012. Warming significantly reduced the photosynthetic rate (P_n) and stomatal conductance (G_s) of S. krylovii, and there was a clear seasonal trend. Warming reduced P_n 17% and 27% and reduced G_s by 24% and 32% in July and September, respectively. Warming also reduced the transpiration rate (T_r), chlorophyll content, the maximum ribulose 1,5-bisphosphate (RuBP) carboxylation rate (V_(cmax)), RuBP regeneration capacity (J_(max)), apparent quantum efficiency (AQE) and the maximum photosynthetic rate (P_nmax) of S. krylovii. Conversely, water use efficiency (WUE) increased by 16.5%. Precipitation enhancement produced compensatory effects on photosynthesis responses to warming. Precipitation enhancement promote P_n, G_s, T_r, chlorophyll content, V_(cmax), J_(max), AQE and the P_nmax of S. krylovii but had did not affect WUE. The effects of temperature and precipitation on photosynthesis and WUE of S. krylovii was caused by stomatal and non-stomatal factors. Under warm conditions and precipitation enhancement, G_s influenced both P_n and T_r. No interactive effects were observed.