施氮对藏北垂穗披碱草人工草地叶片功能性状和种群特征的影响

摘要

于2015-2016年在藏北地区那曲县那曲镇的农业部农业环境科学观测实验站内进行,采取尿素均匀湿撒,施氮水平为0 g·m-2(CK)、7 g· m-2(N1)、15 g·m-2(N2)、30 g· m-2(N3)、40 g·m-2(N4)、50 g· m-2(N5),研究了藏北垂穗披碱草叶片功能性状和种群特征对不同施氮水平的响应.结果表明,1)施氮条件下垂穗披碱草叶面积、比叶面积都有一定提高;施氮显著促进分蘖数增加(P＜0.05),但对叶片光合速率影响不显著;2)不同施氮处理下,抽穗密度有不同程度的提高;生殖高度响应不显著,而营养高度显著升高(P＜0.05),N5最高,为32.87 cm,与对照比增幅达111.29％;盖度先迅速增加然后稳定在饱和状态,从43.67％上升到100％;随施氮量增加,生物量显著增加(P＜0.05),且施氮量越高生物量越高,最高增幅出现在N5处理,达到303.18％,从对照组的145.81 g·m-2增长到了587.89 g·m-2;3)相关性分析表明,氮肥单因子作用下生物量与营养高度、生殖高度以及盖度之间呈显著相关(P＜0.01),表明在施氮条件下,种群特征是影响垂穗披碱草人工草地生产力提高的关键因素,而非叶片功能性状.%Anitrogen addition experiment was performed at the Department of Agriculture Environmental Science Experiment Station in Nagqu town,Northern Tibet,from 2015 to 2016.Urea solution was sprayed on each replicated plot using five treatments:0 g· m-2(CK),7 g· m-2(N1),15 g· m-2(N2),30g· m-2(N3),40 g · m-2 (N4),50 g · m-2 (N5).The study focused on the response of Elymus nutans leaf functional traits and population characteristics to these different nitrogen application rates.The results showed:1) The leaf area and specific leaf area of E.nutans increased with nitrogen application.Nitrogen application also significantly increased tiller number (P＜0.05),while the leaf photosynthetic rate showed no significant response;2) Under different nitrogen treatments,tassel density increased to some extent but the reproductive height was not significantly impacted.The trophic height increased significantly (P＜0.05);the largest increase was 32.87 cm at N5,111.29％ higher than CK.Coverage increased rapidly at first and then stabilized in the saturated state,rising from 43.67％ to 100％.With increasing nitrogen rates,biomass increased significantly (P＜0.05),and the higher the nitrogen the higher the biomass,with the largest increase occurring in the N5 treatment,303.18％ (587.89 g · m 2) higher than the control group (145.81 g · m-2);3) Correlation analysis showed that there was a significant correlation between the biomass and reproductive height,trophic height,and coverage when loaded on nitrogen application as a single factor (P＜0.01).These results indicate that population characteristics rather than leaf functional traits are the key factors to improve the productivity of E.nutans grassland undergoing nitrogen application.