Abstract:

In order to reveal the water-holding function of Tianshan spruce forests and to investigate the characteristics of hydrological effects of the litter layer and soil layer of Tianshan spruce forests. The Tianshan spruce forest in the middle part of the northern foothills of the Tianshan Mountains was used as the study object, and a series of sample plots was deployed along the altitude gradient (1500−2300 m), and quantitative analyses of the water-holding capacity of the litter layer and soil layer of the Tianshan spruce forests were carried out by using the sample survey method and the indoor immersion method, so as to clarify the characteristics of the differences in their differentiation along the elevation gradient. The results showed that 1) the thickness (2.50−3.38 cm) and volume (13.6−21.7 t•hm⁻²) of the litter layer in Tianshan spruce forests both decreased significantly with elevation (P< 0.05); the maximum water holding capacity (50.9−65.0 t•hm⁻²) and effective storage capacity (21.6−25.8 t•hm⁻²) of the litter layer in Tianshan spruce forests showed an increasing trend followed by a decreasing trend as elevation increased; comparison of the water-holding process of different altitudinal gradients found that the water-holding capacity increased rapidly within 1h of immersion, during which the rate of water absorption was the greatest; during the same time, the water-holding capacity of the semi-decomposed layer of litter was greater than that of the undecomposed layer. 2) In the four altitude bands from 1500−1700, 1700−1900, 1900−2100, and 2100−2300 m, soil bulk density (0.481, 0.621, 0.643, and 0.452 g•cm⁻³), capillary porosity (72.6%, 77.5%, 70.5%, and 75.8%), and total porosity (76.1%, 81.0%, 73.4%, and 78.8%) showed an increasing tendency and then decreased with the increase of elevation; the order of soil saturated water holding capacity and capillary water holding capacity at each altitude gradient was as follows: 1700−1900 m>1500−1700 m>2100−2300 m>1900−2100 m; the order of effective soil water holding capacity was as follows: 1700−1900 m>1500−1700 m>1900−2100 m>2100−2300 m, all of which increased and then decreased with the increase of altitude. 3) The total effective water holding capacity (83.4−95.9 t•hm⁻²) and the maximum water holding capacity (1390−1662 t•hm⁻²) of the litter layer and soil layer both showed an increase and then a decrease as elevation increased, and there was no significant difference between elevations (P> 0.05). It was found that the water-holding capacity of Tianshan spruce forest ecosystem showed a general increasing trend followed by decreases along the altitudinal gradient, and the water-holding capacity was better in the middle and low altitude areas (1500−1900 m).

Key words: Tianshan spruce forest, water retention, elevation gradient, litter layer, soil layer

摘要：

为揭示天山云杉森林的水源涵养功能，探究天山云杉林枯落物层和土壤层水文效应特征。以天山北麓中段的天山云杉森林为研究对象，沿海拔梯度（1500－2300 m）布设系列样地，采用样地调查法和室内浸泡法对天山云杉森林枯落物层和土壤层的水源涵养能力进行定量分析，明确其在海拔梯度上的分异特征。结果表明，1）天山云杉森林枯落物层厚度（2.50－3.38 cm）和蓄积量（13.6－21.7 t•hm⁻²），两者均随海拔的升高而显著减小（P<0.05）；天山云杉森林枯落物层最大持水量（50.9－65.0 t•hm⁻²）和有效拦蓄量（21.6－25.8 t•hm⁻²）均随海拔升高先增大后减小；对比不同海拔梯度枯落物的持水过程发现，其在浸水1h内持水量迅速增加，此时吸水速率最大；相同时间内，半分解层枯落物持水量均大于未分解层。2）在1500－1700、1700－1900、1900－2100、2100－2300 m 4个海拔段的土壤容重（0.481、0.621、0.643、0.452 g•cm⁻³）、毛管孔隙度（72.6%、77.5%、70.5%、75.8%）和总孔隙度（76.1%、81.0%、73.4%、78.8%）均表现为随海拔升高先增大后减小的趋势；各海拔梯度土壤饱和持水量与毛管持水量排序为1700－1900 m>1500－1700 m>2100－2300 m>1900－2100 m，土壤有效持水量排序为：1700－1900 m>1500－1700 m>1900－2100 m>2100－2300 m，均随海拔的升高表现为先增大后减小。3）枯落物层和土壤层总的有效持水量（83.4－95.9 t•hm⁻²）和总最大持水量（1390－1662 t•hm⁻²）均随海拔的升高先增大后减小，在各海拔段间无显著差异（P>0.05）。通过研究发现天山云杉森林生态系统的水源涵养能力总体呈现沿海拔梯度先增大后减小的趋势，中低海拔区域（1500－1900 m）水源涵养能力较好。

关键词: 天山云杉森林, 水源涵养, 海拔梯度, 枯落物层, 土壤层