黄河三角洲人工林地土壤的水盐动态变化

Dynamic Changes of Water and Salt in Soils of Different Plantations in the Yellow River Delta

在调查林分长期生长特征的基础上,以未造林荒地为对照,系统研究黄河三角洲不同退化程度刺槐林、刺槐白蜡混交林和白蜡纯林等人工林地土壤的水盐动态变化特征。结果表明:人工刺槐林的退化程度越高,其林地表层土壤含水量越低,深层土壤盐分含量则越高。与刺槐、白蜡纯林相比,混交林土壤含水量相对较高、土壤盐分则较低。春、秋、冬三季,严重退化刺槐林土壤含水量随土层深度增加而升高,而轻度退化刺槐林土壤含水量季节变化较复杂。春、冬两季随土层深度增加土壤含水量呈现出先升高后降低的趋势,夏季则相反,而秋季逐渐降低。混交林及相应纯林的土壤含水量在春季随土层深度增加均表现出先降后升的趋势;夏季有很大程度的降低,但混交林高于纯林;秋、冬季时纯林土壤含水量由表层向深层递减,混交林则先下降后上升。轻度退化刺槐林的土壤含盐量在全年中均较低,而严重退化刺槐林深层土壤含盐量较高。相比之下,混交林降低土壤含盐量的能力最强,刺槐纯林次之,白蜡纯林最弱。总之,在滨海盐碱地区营造人工林,能在一定程度上改善土壤含水量和含盐量,明显影响土壤中水分、盐分的时空分布。

Based on the growth investigation of different plantations including 3pure plantations of black locust（Robinia pseudoacacia）with variable degree of degradation,1pure plantation of velvet ash（Fraxinus velutina）and 1 mixed plantation of black locust and velvet ash,the seasonal changes of water and salt contents in the soils of these plantations were studied with the control of the unplanted land in the Yellow River delta.The results showed that soil moisture content in the soil surface layer decreased and soil salt content in the deeper soil layer increased with increasing degree of degradation.Compared with pure planatations of Robinia pseudoacaciaand Fraxinus velutina,the mixed plantations of Robinia pseudoacaciaand Fraxinus velutina had higher soil moisture content and lower soil salt content.For severely degraded stands,soil moisture content increased with increasing soil depth except in summer,while the slightly one had complicated tendency.Soil moisture content first increased and then decreased with increasing soil depth in spring and winter,but that was opposite in summer,and gradually reduced in autumn.However,in mixed plantation of Robiniapseudoacaciaand Fraxinus velutina and corresponding pure plantations,soil moisture content first decreased and then increased with increasing soil depth in spring,with the peak in the soil layer of 40-60 cm.In autumn,soil moisture content descended from the soil surface layer to the deeper ones,but soil moisture content of mixed plantation was higher than that of pure ones.Furthermore,when soil moisture content of pure stands declined from the surface to the deep in autumn and winter,it first decreased and then increased with increasing soil depth in mixed stand.For soil salinity,the change in soil profile was obvious for different plantations.Soil salt content was lower during the whole year in slightly degraded plantation,while that was higher in soil layers of below 60cm in severly degraded plantation.In contrast,the mixed plantation of Robinia pseudoacacia and Fraxinus velutina had strong ability to reduce soil salt content,Robinia pseudoacaciatook the second place,and Fraxinus velutina was the weakest.In a word,afforestation in the saline-alkali soil of coastal region could improve soil moisture content and soil salt content to some extent,and significantly affect its spatial and temporal distribution.