高寒山区混播草地燕麦和毛苕子种间竞争对密度的响应

混播草地种内与种间竞争的强弱和转化受混播牧草相对密度的制约。2010年6-9月采用取代系列实验方法,在石羊河上游建立燕麦(Avena sativa)和毛苕子(Vicia villo-sa)混播草地,按燕麦与毛苕子相对密度设置1∶0(KY)、8∶2(A)、6∶4(B)、5∶5(C)、4∶6(D)、2∶8(E)和0∶1(KM)7个处理,研究了密度制约下混播草地一年生牧草种间竞争的变化。结果表明:混播草地在密度影响下各物候期的种内与种间竞争发生不同程度的转化,所有混播处理中燕麦相对产量(RYy)随牧草的生长逐渐增加;混播处理A、B和C中毛苕子相对产量(RYm)随牧草的生长逐渐减小,混播处理D和E中逐渐增加;在燕麦出苗期和分蘖期除混播处理A外其余混播处理中两牧草为敌对关系(RYT<1),在牧草生长后期所有混播处理中两牧草转化为共生关系(RYT!1),且燕麦的竞争能力强于毛苕子(RCCy!1、RCCm"1);所有混播处理在牧草整个生长阶段的竞争偏利于燕麦(AG<1)。混播草地内种间竞争在各物候期表现出明显的密度制约现象,实现了资源协同利用目标。

Inter-specific competition between Avena sativa and Vicia villosa in mixed sowing grassland in alpine region of the Qilian Mountain in response to grass density

The intensity and transformation of intra-and inter-specific competitions in mixed sowing grassland is affected by the relative density of mixed sowing grass species.From June to September 2010,a replacement series experiment was conducted to establish an Avena sativaVicia villosa mixed sowing grassland in the upper reaches of Shiyang River.Seven treatments with the relative density of A.sativa and V.villosa being 1:0(KY),8:2(A),6:4(B),5:5(C),4:6(D),2:8(E),and 0:1(KM) were designed to study the changes of the interspecific competition between annual grass species in mixed sowing grassland under effects of the grasses densities.Affected by the relative density of A.sativa and V.villosa,the intra-and interspecific competitions of the grass species in different phonological periods were transformed in different degrees.In all mixed sowing treatments,the relative yield of A.sativa(RYy) increased with its growth,while the relative yield of V.villosa(RYm) decreased with its growth in treatments A,B,and C but increased in treatments D and E.At the seeding and tillering stages of A.sativa,the two grass species were in a hostile relationship(RYT < 1) in all mixed sowing treatments except A,but at later growth stages of A.sativa,the relationship transformed to symbiotic(RYT>1) in all mixed sowing treatments,and the competition of A.sativa was stronger than that of V.villosa(RCCy>1,RCCm<1).The competition in all mixed sowing treatments was beneficial to A.sativa(AG < 1) in its whole growth period.It was suggested that the intra-and inter-specific competitions in mixed sowing grassland in each phonological period showed an obvious density-dependent phenomenon,realizing the cooperative use of resources between the mixed sowing grass species.