黄河三角洲林草复合系统土壤水盐分布特征及其边界效应

Distribution characteristics and edge effect of soil water and salt in silvopastoral system of the Yellow River Delta, China

以国土部土地利用山东无棣科学观测野外基地白蜡-香花槐混交林×紫花苜蓿林草复合系统为对象,研究了0~40 cm土层土壤的水盐分布特征,并通过游动分割窗技术分析了系统内水盐边界效应.结果表明:白蜡-香花槐混交林×紫花苜蓿林草复合系统内土壤水盐含量在水平方向上分布不均衡,越靠近表层,水平方向土壤含水量变异程度越大,而土壤含盐量变异程度越小.以混交林带为分界线,其两侧土壤水盐含量均有相同变化规律:随离林带距离的推近,在0~10 cm土层,含水量先降低再升高,含盐量平缓波动;在10~ 20 cm土层,含水量下降-平缓-下降,含盐量先上升后下降;在20~40 cm土层,含水量平缓波动,含盐量持续升高.林草复合系统内土壤水盐含量均随土层深度的增加而显著升高.林草复合系统土壤中除HCO3^-、K^+外,其余各离子含量与总盐含量呈相同变化规律,相关性大小为Na^+>Cl^->SO4^2->Mg2+>Ca^2+.游动分割窗技术表明,南北走向林草复合系统中,土壤水分的主要竞争区域为林带东侧2.5至林带西侧2m区域;土壤盐分在距林带1.0 m范围内受林带主导影响,距林带1.0~3.0 m范围内受林带及紫花苜蓿的共同影响.

We measured soil water and salt distribution characteristics at 0-40 cm soil depth in a silvopastoral system of Fraxinus chinensis and Robinia pseudoacacia mixed forest × Medicago sativa, which is located in Land Use Scientific Observation Field Base of Ministry of Land and Resource in Wudi, Shandong Province, China. The moving split-window technique was used to analyze the internal-system edge effect. The results showed that both soil water and salt contents in this system heterogeneously distributed in the horizontal direction. The variation of soil water was greater and that of soil salt contents was the smaller when closer to the soil surface. With the mixed forest tree row as the boundary line, the contents of soil water and salt on both sides showed similar change trend. With the decreases of distance to the tree row, soil water content reduced first and then increased but the salt contents had a stable fluctuation at 0-10 cm soil layer. Soil water content showed a trend of decrease-flat-decrease but the salt contents first enhanced and then reduced at 10-20 cm soil layer, respectively. At the deeper soil layer (20-40 cm), the water content fluctuated stably but the salt content continued increasing. Both the contents of soil water and salt in the vertical direction increased significantly with soil depth. Except HCO3- and K+, there was a similar change trend between ions and total salt content in the soil of silvopastoral system, and the correlation between these ions and total salt content was Na^+>Cl^->SO4^2->Mg^2+>Ca^2+. Based on the technique of moving split-window, the edge effect zone of soil water in the silvopastoral system was 2.5 m from the east side of the tree row to 2 m from the west side. Soil salinity in the silvopastoral system was mainly affected by the tree row within the range of 1.0 m, and by both of the tree row and M. sativa within the range of 1.0-3.0 m.