摘要
人类活动和气候变化导致的大气氮沉降急剧升高,将会影响高寒草原植物养分循环。为了研究氮沉降对高寒草原植物养分含量及生态化学计量学特征的影响。依托2009年在新疆天山巴音布鲁克高寒草原设置的长期氮沉降研究平台,于2017年7月和10月采集溚草(Koeleria cristata)、二裂委陵菜(Potentilla bifurca)和天山赖草(Leymus tianschanicus) 3种植物的成熟叶和老叶,分析3种植物叶片N、P元素生态化学计量对不同施氮水平的响应规律。结果表明:①3种植物养分浓度及其化学计量比在成熟叶和老叶之间存在较大差异,成熟叶和老叶的N、P含量分别为12. 78 mg·g~(-1)、0. 88 mg·g~(-1)和6. 88 mg·g~(-1)、0. 46 mg·g~(-1)。3种植物成熟叶和老叶的N元素含量均为:二裂委陵菜>天山赖草>溚草,P元素含量同N元素含量趋势一致;②氮添加增加了成熟叶和老叶N浓度,分别达12%和48%;成熟叶与老叶P浓度对氮添加的响应规律不一致,成熟叶P浓度对氮添加的响应与物种有关,而老叶P浓度呈一致的下降趋势;氮添加对成熟叶和老叶N∶P的比值影响亦不同,其中相对于成熟叶,老叶的N∶P呈显著增加趋势。③植物叶片的N元素、P元素和N∶P比三者之间的相关分析表明:N元素和N∶P之间呈显著正相关关系(P <0. 05),在生长旺盛期和枯黄期,溚草和天山赖草的N与P元素之间没有发现显著相关性(P>0. 05),而二裂委陵菜呈现一定的差异性,在生长旺盛期二裂委陵菜叶片N与P元素呈显著的正相关、枯黄期呈显著的负相关(P <0. 05)。表明长期氮的添加显著影响了3种植物叶片的养分含量和生态化学计量,不同物种间存在一定差异,未来氮沉降升高将会影响天山山地草原的植物养分循环。
Atmospheric nitrogen( N) deposition is rapidly increased due to the increase of human activities and climate change,which enhances the N availability and affects the nutrient cycling of plants in alpine grasslands.However,there is still much debate about how the change of nutrient availability affects P content in plants,therefore,the effects of N addition on N and P contents and N∶ P stoichiometry in mature and senesced leaves at plant organ level in the Bayinbuluk alpine grasslands in the northwest Tianshanin Mountains in China were examined based on a 10-year field experiment. The nitrogen and phosphorus contents in mature and senesced leaves of Potentilla bifurca,Leymus tianschanicus and Koeleria cristata were measured,and the values of foliar stoichiometry under N addition treatments at levels of 0,3,9 g·m~(-2)·a~(-1)) were estimated. Results showed that there were the significant differences of the values of nutrient concentration and foliar stoichiometry between the mature and senesced leaves.The N contents in mature and senesced leaves were 12. 78 mg·g~(-1) and 6. 88 mg·g~(-1),and the P contents were0. 88 mg·g~(-1) and 0. 46 mg·g~(-1),respectively. N and P concentrations in mature and senesced leaves were in an order of P. bifurca > L. tiansecalinus > K. cristata. After the N treatments for 10 years,the N contents in mature and senesced leaves were increased by 12% and 48% respectively. It was found that there was a divergent response of P content in leaves,the effect of N addition on foliar P content was different from different plant species,and the P content in senesced leaves was decreased by N addition. N∶ P in senesced leaves was increased significantly but not in mature leaves. In addition,the correlations between N and P elements and plant stoichiometry in mature and senesced leaves were different. There was a positive correlation between foliar N and P contents of P. bifurca in mature leaves( P < 0. 05),but a negative correlation in senesced leaves. Our finds revealed that nitrogen addition affected significantly the nutrient content and stoichiometry in leaves of the three species,but there was a significant difference among species. The increase of N deposition would affect the nutrient cycling of plants in grasslands in the Tianshan Mountains.
引文
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