黄土丘陵区白羊草群落光谱特征对氮磷添加的响应

Spectral Characteristics of Bothriochloa ischaemum Community in Response to Nitrogen and Phosphorus Addition at Loess Hilly-gully Region

为利用草地群落光谱参数来评价氮磷施肥效应,本研究以安塞纸坊沟流域内白羊草(Bothriochloa ischaemum)群落为研究对象,测定计算不同氮磷添加[N处理:0(N_(0)),25(N_(25)),50(N_(50))和100(N_(100))kg N·hm^(-2)·a^(-1);P处理(以P_(2)O_(5)计):0(P_(0)),20(P_(20)),40(P_(40))和80(P_(80))kg P_(2)O_(5)·hm^(-2)·a^(-1)]的草地群落光谱特征,同步测定草地群落地上生物量和盖度并计算群落多样性指数。结果表明:施氮显著增大群落地上生物量和盖度,施磷显著增加盖度,氮磷添加对群落多样性无显著影响;氮磷添加后,光谱在“蓝谷”,“绿峰”和“红谷”处的反射率均显著降低;单施氮对红边参数无显著影响,单施磷显著增大红边斜率及面积;植被指数在施氮或施磷后均显著增大,且磷添加的增幅大于氮。总体研究表明,施氮和施磷对草地生物量和盖度的影响不同,施磷能有效提高白羊草群落盖度和群体光合能力,N_(50)P_(40)处理提升群落光合能力最强。

Analyzing the spectral characteristics of Bothriochloa ischaemum community in response to nitrogen(N)and phosphorus(P)addition can provide scientific basis for evaluating fertilization effect on grassland.Four N addition treatments[0(N_(0)),25(N_(25)),50(N_(50))and 100(N_(100))kg N·hm^(-2)·a^(-1)]and four P addition treatments[0(P_(0)),20(P_(20)),40(P_(40))and 80(P_(80))kg P_(2)O_(5)·hm^(-2)·a^(-1)]were conducted in Zhifanggou watershed at Ansai District of Yan’an City,Shaanxi Province.Spectral characteristics of grassland community were obtained and calculated.The aboveground biomass production(AGB),community coverage(Cov)and community diversity index were also measured and analyzed.Results showed that AGB and Cov increased significantly after N addition,and Cov increased significantly under P addition,while diversity index showed no responses to N and/or P addition.The spectral reflectance of“blue-valley”,“green-peak”and“red-valley”decreased significantly after N and P addition,and the red edge-slope and red edge-area values increased significantly with P addition,while red edge-positon values had no response to N addition.Four vegetation indices increased significantly in response to N or P addition,and the increase of phosphorus addition was greater than that of nitrogen addition treatment.In summary,N or P addition differently influenced the aboveground biomass and canopy coverage of B.ischaemum community.P addition would efficiently improve community coverage and photosynthetic capacity of B.ischaemum,and the community photosynthetic capacity was the highest under 50 kg N·hm^(-2)·a^(-1)and 40 kg P_(2)O_(5)·hm^(-2)·a^(-1) combined application treatment.