大气CO_(2)浓度升高和海平面上升对滨海湿地植物地下生物量的影响

Effects of Atmospheric CO_(2)Concentration Rising and Sea Level Rising on Belowground Biomass of Plants in Tidal Wetlands

大气CO_(2)浓度升高和海平面上升会通过影响植物的分布和生长状况,继而影响湿地的稳定性。地下生物量是调节潮汐湿地生态系统功能的关键因素,包括土壤有机质的积累和湿地海拔高程的维持。本文通过设置开顶式生长箱(OTC:open top chamber)试验探究不同海拔的3个典型植物群落(SC群落:C_(3)植物为主的群落;MX群落:C_(3)、C_(4)植物混合群落;SP群落:C_(4)植物为主的群落)对CO_(2)浓度升高和海平面上升的响应差异。研究结果显示:CO_(2)浓度升高能够显著增加SC、MX和SP群落的根茎、根和总地下生物量,但年际差异较大。海平面上升显著降低了3个群落植物的根生物量和SC群落高CO_(2)浓度处理下及SP群落对照处理下的总地下生物量,但对根茎却无显著影响。在高盐的条件下,高CO_(2)浓度一定程度上能够缓解高盐分对植物的胁迫,但高CO_(2)浓度的施肥作用下降。对照条件下的SC和MX群落总地下生物量随试验年份延长呈下降趋势,其下降主要是由于海平面的快速上升导致的,而高CO_(2)浓度能减缓其下降趋势,一定程度上抵消胁迫。因此,海平面上升正严重威胁未来湿地的稳定性,而CO_(2)浓度升高能一定程度上缓解海平面上升的危害。

Elevated atmospheric CO_(2)concentration and sea level can influence the stability of the wetland by affecting the distribution and growth of plants.Underground biomass is a critical factor regulating ecosystem functions of coastal marshes,including the accumulation of soil organic matter and the maintenance of wetland elevation.In this paper,OTC(open top chamber)experiments were set up to explore the varied responses of three communities with different plant compositions(SC community:C_(3)-dominated community;MX community:mixed C_(3)-C_(4)community;SP community:C_(4)-dominated community)to elevated CO_(2)and sea level.The results show that the increase of CO_(2)significantly promotes the rhizome,root and total underground biomass of SC,MX and SP communities,and the biomass varies greatly between years.The rise of sea level significantly reduces root biomass of plants in three communities and total underground biomass under elevated CO_(2)treatment in SC community and ambient CO_(2)treatment in SP community,but has no significant effect on rhizome biomass.Under the condition of high salinity,elevated CO_(2)alleviates the stress of high salinity on plants to some extent,but the fertilization effect of elevated CO_(2)decreased.The total underground biomass of SC and MX communities under ambient CO_(2)treatment is decreased over time,which is mainly due to the rise of sea level.Increased total biomass under elevated CO_(2)partially slows down the decrease and offsets the stress to some extent.Therefore,the rise of sea level may affect the stability of wetlands in the future,and elevated CO_(2)could alleviate the impact of some sea level rise on wetlands.