氮输入对沼泽湿地植物生长和氮吸收的影响

氮是湿地植物生长必不可少的营养元素之一,但当外源氮输入超出植物生长需要时,氮素将抑制植物生长。不同植物对氮输入的响应不同,同一植物不同器官对氮输入的响应也不一致。为了探讨氮输入对湿地植物生长和氮吸收的影响机制,本文选取滇西北典型湖泊湿地纳帕海湖滨挺水植物茭草（Zizania caduciflora）和水葱（Scirpus validus）为对象,通过控制实验,研究了3个不同氮输入水平0 g·m-2·a-1（对照,CK）、20 g·m-2·a-1（N20）、40 g·m-2·a-1（N40）]对茭草和水葱生物量积累、根冠比、氮吸收的影响。结果表明：培养期内,茭草地上生物量始终表现为N40〉N20〉CK,即氮输入促进茭草地上生物量积累;而水葱地上生物量随培养时间不同而发生变化,培养早期N20处理促进水葱地上生物量积累,N40处理抑制水葱地上生物量积累。茭草地下生物量表现为N40〉CK〉N20,即氮输入不足抑制茭草地下生物量积累,足够氮输入促进茭草地下生物量积累;水葱地下生物量表现为CK〉N20〉N40,即氮输入抑制水葱地下生物量积累。植物地上部分和地下部分生长对氮输入的响应也不一致,导致植物根冠比发生变化,茭草根冠比表现为N20

Effects of nitrogen input on marsh wetland plant growth and nitrogen uptake

Nitrogen is an essential plant nutrient. However, pant growth will be restrained if the nitrogen input excess the need of plant growth. There are different respects for different plants under nitrogen input. Moreover, there are different respects in plant organs under nitrogen input. In order to investigate the effects of nitrogen input on plant growth and nitrogen abstraction, taking the typical marsh plant Zizania caduciflora and Scirpus validus in Napahai wetland of Northwest Yunnan as test material, a control experiment was conducted to study their aboveground biomass, belowground biomass, root/shoot biomass ratio and nitrogen uptake under effects of different levels of nitrogen input. Three nitrogen fertilization treatment, i.e., 0 g-m-2 （CK）, 20 g-m-2 （ N20 ） and 40 g＇m-2 （ N40 ）, were installed. The result showed that the aboveground biomass ofZizania caduciflora was N40〉N20〉CK, nitrogen input promoted the aboveground biomass accumulation of Zizania caduciflora. The aboveground biomass of Scirpus validus changed with the incubation time. In the early stage, the aboveground biomass accumulation of Scirpus validus increased under N20 nitrogen input and reduced under N40 nitrogen input. The belowground biomass of Zizania caduciflora was N40〉CK〉N20. The belowground biomass accumulation of Zizania caduciflora reduced under limited nitrogen input and increased under enough nitrogen input. The belowground biomass of Scirpus validus was CK〉N20〉N40.Nitrogen input restrained the belowground biomass accumulation of Scirpus validus. It was indicated that the response of plant to nitrogen input was various among different species. Moreover, the responses of aboveground and belowground of one species to nitrogen input were also different. The root/shoot biomass ratios were changed differently. The root/shoot biomass ratios of Zizania caduciflora and Scirpus validus were N20〈CK〈N40 and N40〈N20〈CK respectively. Nitrogen input promoted the nitrogen uptake of Zizania caduciflora and Scirpus validus. Nitrogen input influence on the aboveground nitrogen content of Zizania caduciflora and the belowground nitrogen content of Scirpus validus significantly.