曹文侠，刘皓栋，李文，徐长林，李小龙，师尚礼

(甘肃农业大学草业学院, 草业生态系统教育部重点实验室, 中-美草地畜牧业可持续发展研究中心, 甘肃 兰州 730070)

连续两年施氮对15龄混作禾草草地的改良效果研究

曹文侠，刘皓栋，李文，徐长林，李小龙，师尚礼

(甘肃农业大学草业学院, 草业生态系统教育部重点实验室, 中-美草地畜牧业可持续发展研究中心, 甘肃 兰州 730070)

摘要：以1999年建植的5个不同禾草组合混作草地为对象，研究连续两年不同施氮量75 kg/hm2(N1)，150 kg/hm2(N2)，225 kg/hm2(N3)和0 kg/hm2(CK)对草地生产力的提升及群落特征的综合影响。结果表明，连续2年施氮均可不同程度提升高寒地区人工禾草草地的生产力和草层高度，但一定程度降低了草地群落的物种多样性和丰富度。N2梯度可在有效提高草地生产力的同时，更好维持建植禾草的优势地位和物种的多样性水平，是该地区15龄人工草地改良的最佳施氮量。不同的禾草混作组合样地及不同施氮年份对施氮的响应存在一定差异，垂穗披碱草比重较大的样地对氮肥的响应较其他禾草更为敏感。研究也证明，过量施氮或单纯连续施氮对高寒地区多年生禾草混作草地群落的稳定性会造成一定影响。

关键词：人工草地；多年生禾草；混作；施氮；改良

Nitrogen fertilizer effects on a 15 year old mixed species alpine pasture after two years

CAO Wen-Xia, LIU Hao-Dong, LI Wen, XU Chang-Lin, LI Xiao-Long, SHI Shang-Li

GrasslandScienceCollegeofGansuAgriculturalUniversity,GrasslandEcosystemKeyLaboratoryofMinistryofEducation,Sino-U.S.ResearchCentersforSustainableGrasslandandLivestockManagement,Lanzhou730070,China

Abstract:Five different gramineous mixed pastures planted in 1999 were studied, and pasture productivity and plant community characteristics were recorded during two consecutive years of N fertilization at 75 kg N/ha (N1), 150 kg N/ha (N2), 225 kg N/ha (N3), or 0 kg N/ha (CK). N fertilization enhanced the pasture productivity and height of these alpine pastures, but reduced plant species richness and diversity to some extent. The optimal fertilization rate for these 15 year old pastures was 150 kg N/ha per year, as this application rate improved pasture productivity and maintained the dominance of gramineous species in the plant communities. The nitrogen response differed between years and pasture with a large proportion of Elymus nutans was more responsive to N fertilizer than other pasture types. This experiment also demonstrated that single N fertilizer applications may enhance community stability or productivity of these alpine, perennial, mixed cropping cultivated grasslands.

Key words:cultivated grassland; perennial grass; mixed cropping; nitrogen fertilization; improvement

长期以来，受过度放牧等因素的影响，天然草地退化严重[1]，饲草的供给能力减弱。随着国家“退牧还草”、“草原生态补奖”等草原生态工程和政策的实施，草原生态治理区生态得到明显恢复。……