不同土壤水分状况对刺槐的生长及水分利用特征的影响

在适宜土壤水分、中度干旱和严重干旱 3种土壤水分条件下研究了刺槐苗木生长及水分利用特征。结果表明 :随着土壤含水量的下降 ,刺槐叶水势、叶含水量、生长速率、光合速率及单叶水分利用效率 (WUE)均显著下降 ;在整个生长季中刺槐枝条快速生长和干物质增加主要集中在 4— 6月份 ;适宜水分下总耗水量和总生物量均为最高 ,但总水分利用效率在中度干旱时为最高 ;刺槐最高耗水月、最高耗水日和一天中最高耗水时间段在 3种土壤水分下均有差异 ,在中度干旱和严重干旱下的最高耗水日出现的时间比适宜水分下的最高耗水日滞后一个月以上。刺槐的最大耗水月在 3种土壤水分下均在 7月份 ;刺槐日耗水进程在生长季多数月份呈单峰曲线 ,7月份多呈双峰曲线。刺槐属于耐旱性强的高耗水树种。根据刺槐的生长及耗水特点 ,刺槐不适宜大面积栽植在黄土高原缺水地区 ,仅适合栽植在阴坡、沟渠等土壤水分条件较好的立地上。

Characteristics of Growth and Water Use of Robinia pseudoacacia under Different Soil Water Conditions

Pot culture experiments were conducted to investigate the characteristics of growth and water use of Robinia pseu~doacacia under different soil water conditions,which were suitable soil water condition, medium soil water stress and serious soil water stress. The results showed that R. pseudoacacia leaf water potential, leaf relative water content, mean rate of shoot growth, photosynthetic rate and water use efficiency (WUE) of single leaf all decreased significantly with decreasing of soil moisture. In whole growth season, R. pseudoacacia shoot grew and yielded quickly mainly from April to June. Total water consumption and biomass of R. pseudoacacia under suitable soil water condition were all the highest, yet water use efficiency was the highest under medium soil water stress. The monthly highest water consumption, the daily highest water consumption and the time that the daily highest water consumption appeared of R. pseudoacacia were different under the three soil water conditions. The date of the daily highest water consumption under medium and serious soil water stress was about a month later than that under suitable soil water condition, and the monthly water consumption of R. pseudoacacia all reached its peak in July under three soil water conditions.In growth season, R. pseudoacacia showed a single peak in photosynthetic rate and transpiration rate in the diurnal variation, except a pronounced midday depression in July. R. pseudoacacia had characteristics of high water consumption and high drought resistance, and was not fit to be massively planted over vast area in some water shorten regions in Loess Plateau, but only fit for some slope condition such as shady slopes and gaps, where soil water condition was more favorable.