滨海盐碱地不同林龄白蜡人工林根系分布及土壤特性变化

Root Distribution and Soil Properties of Fraxinus Plantations with Different Forest Stand Ages in the Coastal Saline-alkali Land

采用空间代替时间的方法,选取黄河三角洲滨海盐碱地典型白蜡人工林,研究了不同林龄间(5、12、18 a)根系分布特征、土壤团聚体组成及养分变化规律。结果表明:3种林龄白蜡根系生物量均随林龄的增加而增大,不同林龄间根系生物总量差异显著,根系构成均以D>5 mm径级的粗根为主,约占不同径级根系生物总量的77.04%~81.24%,而D<2 mm的细根生物总量最小,仅占根系生物总量的8.31%~10.21%。3种林龄人工林约80%以上的根系分布在0≤H<40 cm土层,不足5%的根系分布在深层土,不同径级根系均具有明显的表聚现象;3种林龄土壤湿筛团聚组成主要以<0.25 mm粒径为主,含量在70.51%~84.35%之间,>0.25 mm水稳性团聚体以18 a林地含量最高,5 a林龄最低。水稳性团聚体平均质量直径(D MW)随着林龄的增加而增大,林龄越大土壤团聚体稳定性越强,且影响以表层土最为明显;土壤养分与根系分布规律类似,也表现出明显的表聚现象,且随林龄的增加各土层养分含量也逐步累加;根系生物量与D MW及土壤特性间的显著和极显著相关表明,根系对盐碱地土壤质量的提升有明显的改善作用。

Adopting the concept of space as a substitute for time, with the typical Fraxinus plantations in the coastal saline-alkali land of Yellow River Delta, we studied the characteristics of root distribution, soil aggregate composition and the variation of nutrient of different forest stand ages (5, 12 and 18 a). The root biomass increased with the increase of forest stand age, and there were significant differences in the total root biomass of different forest stand ages. Root composition was mainly coarse roots with diameter greater than 5 mm, accounting for 77.04% to 81.24% of total root biomass at different diameter levels, and the total biomass of fine root ( D <2 mm) was the least with the proportion of 8.31%-10.21% in the total root biomass. More than 80% of root was distributed in the soil of 0≤ H <40 cm, and less than 5% in the deep soil. The root of different diameters had obvious surface accumulation. The main components of soil aggregate with wet sieving of 3 kinds of forest stand age were the <0.25 mm aggregate, with the proportion of 70.51%-84.35%. The content of >0.25 mm aggregate of the 18-a forest was the highest, and it was the lowest in the 5-a forest. The mean weight diameter (MWD) of water-stable aggregate increased and the stability of soil aggregates became stronger with the increase of forest stand age, and the top soil was influenced mostly. Soil nutrients also had obvious surface accumulation similar to the root, and increased gradually with the increase of forest stand age. The great significant correlations among root biomass, the MWD of water-stable aggregate and soil properties showed that the root system made great contributions to the improvement of saline-alkali land of forest.