不同林龄杉木人工林土壤C:N:P化学计量特征及其与土壤理化性质的关系

为了阐明林龄对杉木人工林土壤理化性质及碳氮磷(C∶N∶P)生态化学计量特征的影响,在福建农林大学三明莘口林场选取4个林龄(4, 20, 24, 33a)的杉木人工林为研究对象,测定0—20,20—40,40—60 cm深度土壤的水分-物理性质、pH、总碳(TC)、全氮(TN)、全磷(TP)、全钾(TK),探讨它们随林龄的变化及其与C∶N∶P化学计量比之间的关系,为杉木人工林持续经营管理提供科学依据。结果表明:(1)随着林龄的增加,质量含水量、田间持水量和毛管孔隙度先减小后增加,在20 a达到最小,TN和TP也有相似的变化趋势,但在24 a林分的深层土壤达到最小,TC和TK保持不变;(2)随着林龄的增加,C∶N保持不变,C∶P和N∶P在24 a成熟林达到最大,但只在20—60 cm达到显著差异;(3)TC与多数水分-物理性质及3个生态化学计量比显著相关,质量含水量和孔隙度与C∶N∶P生态化学计量比均显著相关,TP与C∶P和N∶P显著负相关。土壤物理性质与土壤养分循环存在一定关联,有机质与土壤结构及养分平衡的调节有关,研究区杉木林发育过程中土壤腐殖质化进程较缓慢,24 a成熟林杉木的生长受到土壤磷的限制,在杉木速生阶段适当增施磷肥,保证林木的良好生长,促进土壤与植物的良性养分循环。

Soil C: N: P stoichiometry and its relationship with the soil physicochemical properties of different aged Chinese fir (Cunninghamia lanceolata) plantations

To investigate the effect of stand age on soil physicochemical properties and C:N:P stoichiometry in Cunninghamia lanceolata plantations, an age sequence of Cunninghamia lanceolata stands (4 years old, 20 years old, 24 years old, and 33 years old) were selected in the Xinkou Experimental Forestry Centre of Fujian Agricultural and Forestry University, Sanming, Fujian. Soil water content, porosity, pH, total carbon (TC), total nitrogen (TN), total phosphorus (TP), total potassium (TK), and soil C:N:P stoichiometry at soil depths of 0-20, 20-40, 40-60 cm were measured during stand development. The results showed that the soil gravimetric water content, water field capacity, and capillary porosity were lowest at 20 years old, and then increased thereafter. There was a similar trend in changes of TN and TP, which had the lowest values in deep soil of the 24 year old stand. Stand age did not significantly affect TC, TK, or C:N. C:P and N:P were higher in the 24 year old mature stand; however, significant differences were only detected at soil depths of 20-60 cm. The majority of soil physicochemical variables showed significantly correlations with TC. Gravimetric water content and capillary porosity showed significant correlations with C:N, C:P, and N:P. TP correlated negatively with C:P and N:P, indicating a firm linkage between soil physical properties and nutrient cycling in Chinese fir plantations. The regulation of soil structure and nutrient balance may be influenced by soil organic matter. Humification in our study area was slow during the development of Cunninghamia lanceolata plantations. The growth of the 24-year-old mature stand was limited by soil phosphorus. Therefore, P fertilization during the rapid growth period of Cunninghamia lanceolata may be important to sustain the growth of Cunninghamia lanceolata and to improve nutrient cycling between plant and soil.