Effects of 3-year air warming on growth of two perennial grasses (Phragmites australis and Imperata cylindrica) in a coastal salt marsh reclaimed for agriculture

题名：Effects of 3-year air warming on growth of two perennial grasses (Phragmites australis and Imperata cylindrica) in a coastal salt marsh reclaimed for agriculture
领域：MARINE & FRESHWATER BIOLOGY 三区
来源：Aquatic Botany

发表年代：2014年

作者：Zhong QC, Gong JN Wang KY, Zhang C*

The aim of this study was to examine the potential effects of air warming on growth of two perennialgrasses (a C3species Phragmites australis (Cav.) Trin. ex Steud. and a C4species Imperata cylindrica (Linn.)Beauv.) in a coastal salt marsh reclaimed for agriculture. For this purpose, open-top chambers (OTCs)were used with a mean air temperature elevation of approximately 1.5◦C on Chongming Island locatedat the Yangtze Estuary. After 3 years’ treatment, a series of growth-related traits of the two species underwarming conditions were compared to the same plant materials under the ambient conditions. RegardingP. australis, air warming significantly decreased leaf net photosynthetic rate by 28%, together with leafarea, aboveground biomass and relative growth rate of aboveground biomass by 22%, 28% and 36% at theshoot level, respectively; but it markedly increased specific leaf area by 12% at the shoot level, togetherwith shoot density, leaf area index and aboveground biomass by 142%, 87% and 69% at the populationlevel, respectively. On the other hand, for I. cylindrica, air warming did not significantly change leafnet photosynthetic rate, morphological or growth traits of aboveground part at the shoot level; but itmarkedly decreased shoot density, leaf area index and aboveground biomass by 49%, 45% and 47% at thepopulation level, respectively. Air warming had no significant effect on rhizome biomass of P. australisdown to a depth of 20 cm; but it significantly decreased the rhizome biomass of I. cylindrica by 42%.Air warming had no significant effect on the mean soil temperature, volumetric moisture or inorganicnitrogen in the upper soil layer; but it markedly increased the mean soil porewater salinity by 119%. Inan environment with elevated air temperature and warming-increased soil salinity, P. australis enhancedpopulation-level aboveground biomass by increasing shoot density and specific leaf area despite of thedecreased leaf photosynthetic rate and shoot-level growth, while the clonal propagation of I. cylindricawas suppressed by warming-increased soil salinity and inter-specific competition from P. australis. Ourresults suggest that P. australis may well maintain the dominance over I. cylindrica in the reclaimed saltmarsh, when air temperature elevation is within 1.5◦C over the next few decades.