土壤水分动态对胡杨幼苗生长分配策略的影响

Effect of soil moisture dynamics on growth and allocation strategy of Populus euphratica seedlings

分析土壤水分对幼苗地上及地下部分生长及其分配策略是阐明自然生境中胡杨种子更新困难以及人工培育成活率低的重要途径。本文以2年生胡杨幼苗为研究材料,采用不同土壤水分处理试验,监测幼苗地上部分生长指标（地径、冠幅、株高、叶片数）以及地下部分生长指标（总根长、总根表面积、单位平方米土壤总根长、总根体积）,分析不同水分处理及水分梯度对幼苗生长的影响。结果表明：对于胡杨幼苗地上部分的生长,在连续给水处理时,25%含水量更有利于地上部分的生长;而断续给水处理时,最适土壤含水量为30%;胡杨幼苗地下部分生长在不同给水处理下存在显著差别,而25%的含水量要显著区别于其他水分梯度,更有利于根系的生长。一定程度的干旱胁迫后,断续给水比连续给水更有利于根系的生长,且水分梯度在20%~25%之间最有利于根系生物量的积累,地下生物量的积累大于地上生物量,这种地上与地下生长权衡作用有利于幼苗纵向生长的养分、水分获取。在根系构型方面,在土壤水分条件好的情况下则有利于幼苗根系的横向扩展。

Understanding the effect of soil moisture on the growth of Populus euphratica seedlings＇ aboveground part and underground part is important to explain why its seed regeneration is difficult in natural conditions,and furthermore to increase the survival rate of seedlings. An experiment with two different watering treatments was carried out on the biennial seedlings of P. euphratica. The seedlings ＇aboveground growth indices（ basal diameter,crown width,height,number of leaves） and underground growth indices（ total root length,total root surface area per unit square meter of soil total root length,total root volume） were monitored to analyze the effect of different watering treatments and water gradient on growth tradeoff of the seedlings. The results showed that,for the growth of aboveground parts of seedlings,a soil moisture content of 25% was optimum water condition under continuous watering,but under the intermittent watering treatment,a soil moisture content of 30% was most suitable. There was a significant difference in seedlings＇ underground growth under different watering treatments,and a soil moisture content of 25% was significantly different from other levels and more beneficial to root growth.After drought stress,the intermittent water supply was more favorable to root growth than the continuous water supply,and soil moisture content of 20% to 25% was more suitable to root biomass accumulation.When seedlings were subjected to drought stress,the accumulation of underground part biomass was more than that of aboveground parts,and the trade-off effect between the underground and aboveground growth was more conducive to the nutrients and water allocation to the longitudinal growth,but the lateral growth of roots was increased more with enough water supply.