刈割扰动下半干旱区豆科牧草种间关系的反应

Response to cutting treatment of interspecific relationships of leguminous forages in semiarid regions

以苜蓿和沙打旺根据生物替代设计组成的简单混播种群为对象,通过调查2种牧草在刈割扰动下的生长反应,比较了单混播处理条件下3种播种密度刈割处理的种间关系和补偿性反应特点,探讨了种群稳定与演替的可能机制。结果表明苜蓿和沙打旺在刈割条件下,土壤水分利用竞争空间上移20 cm,并且水分利用呈增加趋势,土壤平均水分为15%。刈割诱导低密度混播处理和高密度苜蓿单播处理土壤水分最高,分别达15.6%和15.8%。单播下,刈割可诱导中高密度单播沙打旺处理产量分别增加33%和29%,而混播方式下,刈割均导致沙打旺和苜蓿株高、分枝数和地上部生物量小于对照。在刈割干扰下,相比对照,苜蓿与沙打旺两者仍然为资源共享关系,但互利共生程度下降了21%,而混播种群中苜蓿对沙打旺的相对竞争力增加了17%。不论单播还是混播,刈割均可引发2种牧草显著的补偿机制。同时发现刈割干扰可激发更强的自疏作用。2种牧草的生长指标呈下降趋势可能是干旱、刈割和种间竞争或化感协同胁迫作用的结果,但共存与补偿机制有利于减缓这种负面效应。沙打旺和苜蓿的更新补偿时间上的异质性,实现资源利用生态位的分离,从而调控着2种牧草组成的种群稳定性,这对理解生物多样性维持机制具有重要的参考意义。

The growth response of simple and artifical communities of Astragalus adsurgens and Medic va to cutting treatments based on a biological specific relationships and compensative effects rep of acement method was investigated. A relative study ago satzof interboth leguminous forages was done at three sowing densities for monoculture and mixtures and compared with cutting grass. The possible mechanisms for communities maintaining stable and successive status is discussed. Compared with the control, the cutting treatment led to a compet ducible itively spatial increase of about 20 cm in soil water effect increased soil moisture absor ly enhanced water use of mixtures by 15.6 pt % ion by about 1 utili 5%. zation by A. adsurgens and M. sativa. This in In particular, the cutting treatment significant in low density sowings and by 33% for monocultures of M. sativa in high density sowings. In addition, cutting treatment induced an aerial biomass increase of 29% in A. adsurgens monoculture in the middle and high density sowings. However, plant height, branch numbers per plant, and aboveground biomass declined under the cutting treatment compared with the control. A. adsurgens and M. sativa showed weak resources-sharing with a decline of the relative competition of M. sativa to A. adsurgens was mixture, cutting would increase the compensatory effect of nearly 21% if artificially regulated by cutting and increased by 17 %. Whether in monoculture or in a both forages. It was also found that cutting caused drastic density-limiting effects. The low productivity from additional cutting resulted from the synergistic effect of pressures such as arid circumstances, interspecific competition and allelopathic potential, which can be alleviated by coexistence and compensat resulting from cutting can indicate the sustainable development of the In the present study, the growth response and interspecific relationship some potent mechanisms for maintaining the biodiversity of communities and forage industry.