氮输入和水淹对短叶茳芏生长、养分及固碳的影响

Effects of nitrogen addition and submergence on the growth,nutrients,and carbon sequestration characteristics of Cyperus malaccensis

外源氮输入显著改变河口湿地植物生长和固碳能力,进而影响河口湿地生态系统碳、氮循环过程。以闽江口湿地土著种短叶茳芏(Cyperus malaccensis)为研究对象,通过15个月的中型生态系实验,分析不同氮输入水平(CK,0 g N m^(-2)a^(-1);N8,8 g N m^(-2)a^(-1);N16,16 g N m^(-2)a^(-1))和2种水淹(T1,每天水淹时长2—3 h;T2,每天水淹时长11—12 h)处理对短叶茳芏生长、养分和固碳的影响,探讨短叶茳芏在环境变化下的生长、固碳特征。结果表明:T2处理株高极显著高于T1处理,N8、N16处理的植物株高显著高于CK处理,植物成熟季节的株高也极显著最高(P<0.001)。水淹状况和植物生长期对短叶茳芏的密度有显著影响:T1处理密度极显著高于T2处理,植物成熟季节的密度也极显著最高(P<0.001),但是氮输入没有显著提高植物密度。植物碳含量较为稳定,T2处理地上碳含量显著高于T1处理(P<0.05),但是氮输入和植物生长期对地上碳含量影响不显著。氮输入水平、水淹状况和植物生长期则对植物地上氮含量都有显著影响(P<0.05)。N8处理的植物地上生物量和固碳量极显著最高,CK处理极显著最低,植物成熟期的地上生物量和固碳量也极显著最大(P<0.001),但是不同水淹处理植物生物量和固碳量无显著差异。闽江口湿地短叶茳芏具有较强的环境适应能力,在持续氮输入环境下,闽江口湿地的短叶茳芏可能向高潮滩拓展。

Exogenous nitrogen enrichment can significantly change plant growth and the capacity for carbon sequestration/fixation of wetland plants, and influence the carbon and nitrogen cycles of the estuarine ecosystems. In this study, we examined the effects of nitrogen addition （CK, 0 g N m-2a-1; N8, 8 g N m-2a-1; N16, 16 g N m-2a-1） and submergence （T1, submerged approximately 2-3 hours every day; T2, submerged approximately 11-12 hours every day） on the growth, nutrients, and carbon sequestration characteristics of Cyperus malaccensis using the mesocosm method in a 15 month experiment. The growth, nutrients, and carbon sequestration of C. malaccensis under the experimental environment were also discussed. The results demonstrated that the height of C. malaccensis under the T2 treatment was significantly greater than that under the T1 treatment, and height in N8 and N16 treatments was also significantly greater than that of CK over the entire experimental period. Furthermore, the height of C. malaccensis was the greatest in the mature season（P 〈 0.001）. Submergence and growth period factors had marked effects on the density of plants, and the density of C. malaccensis was significantly greater under the T1 treatments than under the T2 treatments for all times, and the density of C. malaccensis was also the highest during the mature season（P 〈 0.001）; however, nitrogen addition did not result in a marked increase in the density of plants. The aboveground carbon concentration of C. malaccensis was stable, which was higher in T1 treatments than in T2 treatments（P 〈 0.05）, whereas nitrogen addition and the growth period treatments showed no marked influence on the aboveground carbon concentration. Nitrogen addition, submergence, and the growth period factors significantly affected the aboveground nitrogen concentration（P 〈 0.05）. The value of aboveground biomass and carbon sequestration in C. malaccensis was the greatest in the N8 treatment, lowest in the CK treatment, and highest during the mature season（P 〈 0.001）; however, there were no significant differences between submergence groups. C. malaccensis had a strong ability to adapt to changes in the environment, which means that C. malaccensis has the potential to expand to high tidal flat environments under conditions of continuous nitrogen addition in the Min River estuary.