关键词: 蒙古栎, 红松, 光合能力, 林隙大小, 林隙内位置, 小兴安岭

Abstract:

【Objective】 The objective of this study was to determine the suitable forest gap area and position in the gaps for the growth of Pinus koraiensis saplings in secondary forests and provide a scientific basis for the restoration of temperate zonal climate vegetation and broad-leaved P. koraiensis forests. Simultaneously, the findings could provide a theoretical support for optimizing management practices. 【Method】P. koraiensis saplings (15 a) from Xiaoxing’an Mountains were used as the test material. Photosynthetic parameters (maximum net photosynthesis rate, light saturation point, light compensation point, and transpiration rate), chlorophyll content, and micro-environmental factors (light transmittance, temperature) of P. koraiensis saplings grown in three locations (central area, transition area, and edge area) in four gaps[large gap (206.1 m²), medium gap (116.9 m²), small gap (52.4 m²), understory (control, 12.6 m²)]in secondary Quercus mongolica forests were measured using a CIRAS-2 photosynthesis instrument. A Nikon CoolPix 4500 digital camera with a 180° fisheye lens was used to collect photographs of the gaps and obtain the light transmittance at various plots. By comparing the differences in the photosynthetic capacity of P. koraiensis saplings in different gap sizes and within-gap positions, we explored the effects of gap sizes and within-gap positions on the photosynthetic capacity of P. koraiensis saplings.【Result】(1) The photosynthetic capacity of the P. koraiensis saplings was significantly higher in medium and small gaps. Specifically, the medium and small gaps increased the maximum net photosynthetic rate by 20.0%-60.7% compared with that in understory, and the rate within the medium gap was higher than that of the small gap by 9.2%-15.1%. However, the large gap had no significant effect on the photosynthetic rate. (2) The maximum net photosynthetic rate of P. koraiensis saplings in various gaps decreased along the micro-habitat gradient of the center, transition and edge areas of the gaps (92.7%-22.5%). (3) In the medium and small gaps, the light saturation point of P. koraiensis saplings was higher than that for the forest understory, and the light compensation point was lower than that in the forest understory. However, the transpiration rate, stomatal conductance, and intercellular CO₂ concentration in the medium gap were higher than those in the forest understory, and the chlorophyll content was lower than that in the forest understory. The micro-habitat gradient from the central area to the edge area of the gaps reduced the light saturation point of the P. koraiensis saplings, and increased the light compensation point, and decreased the transpiration rate and stomatal conductance, and increased the chlorophyll content.【Conclusion】P. koraiensis saplings in the secondary Q. mongolica forest had a strong photosynthetic capacity in the central area of the medium gaps (116.9 m²). Therefore, to restore P. koraiensis forests rapidly, suitable gaps should be created, and full use of the central position in the gaps should be made.

Key words: Quercus mongolica, Pinus koraiensis, photosynthetic capacity, gap size, within-gap position, Xiaoxing’an Mountains