Objective “Planting conifer and preserving broadleaved tree” (PCPBT) is an effective way to restore broadleaved Korean pine forest of temperate zone climax vegetation in northeastern China. Release cutting can speed up the succession process, however the impact on its hydrological and ecological functions is still unclear. The purpose of this paper is to explore the influence of release cutting intensity on the two key hydrological and ecological processes of litter interception and soil water storage in stand by PCPBT.
Method The litter accumulation, composition structure, litter water holding process, maximum water storage capacity, maximum interception capacity and effective interception capacity were measured by field monthly sampling method and indoor soaking method in stand by PCPBT (42 years of planting Korean pine in secondary forest and 26 years of release cutting) under different release cutting intensities (control, low-intensity release cutting, moderate-intensity release cutting, heavy-intensity release cutting, and full release cutting) during the growing season in Changbai Mountain of northeastern China, to explore the law and mechanism of the influence of release cutting intensity on monthly dynamic process of litter interception and soil water storage in the growing season.
Result (1) After 26 years of release cutting, moderate-intensity release cutting and full release cutting significantly increased the monthly average litter accumulation (3.80−5.41 t/ha) by 27.7%−42.4% (p < 0.05) during growing season. Only full release cutting had changed litter composition, in which the ratio of undecomposed layer and semi-decomposed layer was converted from 3∶2 in control to 1∶1, and the main component of litter was changed from broadleaved (53.5%) to coniferous (56.1%). In addition, moderate-intensity release cutting and low-intensity release cutting obviously weakened the fluctuation of litter accumulation between different months of the growing season. (2) Full release cutting significantly increased the average monthly maximum water storage capacity (12.91−17.83 t/ha), maximum interception capacity (6.37−8.46 t/ha), effective interception capacity (4.43−5.80 t/ha) and soil water storage capacity of litter by 22.8%, 22.8%, 17.5% and 17.9%, respectively, low-intensity release cutting significantly increased litter effective interception capacity by 17.9%. (3) The dynamic process of the maximum water storage capacity of litter in the growing season was not changed by each release cutting intensities (bimodal pattern with the peaks in June and October). However, Full release cutting had increased its maximum water storage capacity (37.3% to 45.7%) during rainfall (July to August). However, low-intensity release cutting and moderate-intensity release cutting tended to be constant from July to September. The maximum and effective interception capacity of litter were increased by each release cutting intensities in May/June, and the monthly dynamic process of the both was transformed from unimodal pattern to bimodal pattern during growing season. The overall regularity of dynamic process of soil water storage during the growing season was changed by each release cutting intensities (double peaks transformed into three peaks), and the size of its peak value was changed (full release cutting increased by about 1/3 in July; low-intensity release cutting increased the October peak by about 1/4). (4) The maximum water storage capacity of litter was mainly promoted by accumulation of litter during the growing season. The maximum interception capacity was mainly promoted by litter accumulation and inhibited by natural water content. The effective interception capacity was inhibited only by the natural moisture content. While soil water storage was only promoted by the maximum water storage capacity of litter.
Conclusion Therefore, after 26 years of release cutting, full release cutting increased litter accumulation, changed litter composition structure, and enhanced litter interception ability (about 1/6−1/5) and soil water storage ability (about 1/6) in the growing season, thus enhancing its function of precipitation regulation and soil water conservation. So full release cutting is a more suitable management mode of temperate zone climax vegetation in northeastern China restoration.
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