刈割、施肥和浇水对垂穗披碱草补偿生长的影响

Effects of clipping,fertilizing,and watering on compensatory growth of Elymus nutans

植物的补偿生长特性受放牧强度和生境资源获得性的影响。通过为期2年的野外控制实验,研究了刈割高度(留茬1cm、3cm及不刈割)、施肥(施、不施)和浇水(浇、不浇)处理对垂穗披碱草(Elymus natans)补偿生长的影响,并结合对各处理分株密度、比叶面积、净光合速率和相对生长率的变化研究,探讨了其补偿生长机制。结果表明:刈割后垂穗披碱草分株种群密度显著增加,补偿生长高度显著降低,比叶面积和相对生长率随刈割强度增加而呈上升趋势,叶片净光合速率变化不显著;施肥能显著增加垂穗披碱草的补偿生长高度、比叶面积、叶片净光合速率和相对生长率;浇水处理以及刈割、浇水、施肥处理之间的交互作用均不显著。可见,在刈割条件下,垂穗披碱草具有一定的密度补偿机制,但由于刈割抑制补偿性高生长,导致分株高度出现低补偿。因此,即使刈割后比叶面积和株高相对生长率显著增加,也不一定必然引起株高的超补偿;但施肥可显著提高垂穗披碱草的补偿能力,增加耐牧性,证实了改进后的限制资源模型的预测。

Grazing intensity and resource availability can affect the compensatory growth of defoliated plants. In this paper, a 2-year field manipulative experiment was conducted to study the effects of clipping （stubbled 1 cm, stubbled 3 cm, and unclipped）, fertilizing （fertilized and unfertilized）, and watering （watered and non-watered） on the compensatory growth of Elymus natans. The compensatory height （CH）, specific leaf area （SLA）, net photosynthesis rate （NPR）, and relative growth rate （RGR） were measured, aimed to approach the compensatory mechanism of the species. With increasing clipping intensity, the ramet density, SLA, and RGR of E. nutans increased significantly, while the CH decreased. No significant difference was observed in the leaf NPR among different clipping treatments. Fertilizing greatly promoted the CH, SLA, NPR and RGR of the species. Watering and the interaction among clipping, watering, and fertilizing had no significant effects on the species. These results suggested that E. nutans had certain density compensation mechanism, but the undercompensation in plant height resulting from the CH was restrained by clipping. An appreciable increase in SLA and RGR after defoliated was not enough to induce overcompensation in plant height. However, fertilizing could enhance the compensation ability, and promote the plant species tolerance against defoliation. Our results confirmed the improved limiting resource model （LRM）.