小叶章对氮沉降的生理生态响应

Ecophysiological Responses of Calamagrostis angustifolia to Nitrogen Deposition

在非淹水(W1)和淹水(W2)条件下,分4个氮处理[分别相当于氮沉降率0 g/(m2.a)、1 g/(m2.a)、3 g/(m2.a)和5 g/(m2.a)]模拟了氮沉降对三江平原典型湿地植物小叶章(Calamagrostis angustifolia)生长及其碳、氮代谢等生理生态指标的影响。结果表明,随着氮沉降量的增加,小叶章的叶面积、株高、植株分蘖数、生物量(叶、茎、根)均呈增加趋势。两种水分条件下,氮沉降处理平均小叶章叶绿素、叶片可溶性蛋白和游离氨基酸含量分别较对照处理增长20.37%、10.52%和19.18%,而可溶性糖含量则下降了14.69%。1 g/(m2.a)、3 g/(m2.a)和5 g/(m2.a)氮沉降处理的净同化率分别为对照处理的1.10倍、2.80倍和3.81倍。与非淹水条件相比,淹水条件下小叶章对氮沉降率的适应能力较强,氮沉降显著促进了小叶章的碳、氮代谢水平。

Nitrogen can strongly limit wetland production and can affect community composition and biogeochemical cycles in different ways. Wetland ecosystems in the Sanjiang Plain, Northeast China may be particularly vul-nerable to current and predicted changes in nitrogen deposition and precipitation, and the responses to potential interactive effects of nitrogen deposition and water are not well understood. component of the wetland plant community, which is sensitive to the change of water and nitrogen conditions predicting the productivity and carbon sequestration environmental conditions is critical for potential of wetland ecosystems. Therefore, a pot culture experiment was conducted to determine the effects of nitrogen deposition on the ecophysiological indices of Calamagrostis angustifolia. Four N （equivalent to 0 g/（m^2 ·a）, 1 g/（m^2·a）, 3 g/（m^2·a） 5 g/（m^2·a） nitrogen dep-osition rate, respectively） and two water treatments （ W1：non-flooded, W2：flooded） were applied. The growth, chlorophyll content and nitrogen, carbon metabolism responses to nitrogen deposition were examined. The results showed that with the increasing of nitrogen deposition, plant growth was prompt, as leaf area, height, plant number and biomass （leaf, stem and root） under two water conditions both had an increasing trend; root biomass was particularly affected by the interaction between water condition and nitrogen deposition. The average contents of chlorophyll, soluble protein and amino acid were also enhanced by nitrogen deposition, which were 20.37%, 10.52% and 19.18% higher than those of control leaves, respectively. However, nitrogen addition reduced the soluble carbon concentration of both water conditions, the mean of which was 14.69% lower than that of control. The net assimilation rate of 1 g/（m^2·a） , 3 g/（m^2·a）,5 g/（m^2·a） nitrogen treatments were a-bout 1.10, 2.80 and der elevated nitrogen 3.81 times of the control, respectively, indicating that photosynthesis was strengthened undeposition. Compared with non -flooded water condition, the adaptation ability of Calamagrostis angustifolia was higher under flooded water condition, which means that the response of Calamagrostis angustifolia to nitrogen deposition would be affected by the change of water condition. Overall, these results suggest that the effects of nitrogen deposition on the growth of Calamagrostis angustifolia were enhanced under flooded water condition, and elevated nitrogen deposition may cause an inerease in the level of carbon and nitrogen metabolism as a result of their effects on the contents of chlorophyll and amino acid. No negative effects have been found under 5 g/（m^2·a） nitrogen treatment.