Photosynthesis adaption in Korean pine to gap size and position within Populus davidiana forests in Xiaoxing’anling, China

Abstract

Forest gaps restrict the restoration of temperate secondary forest to broad-leaved Korean pine forest in zonal climax vegetation by affecting the growth of Korean pine (Pinus koraiensis). However, the photosynthetic adaptability of Korean pine to gap size and position within the gap is unclear. In order to explore the adaptability of young Korean pine (35 years) to different gap sizes in Xiaoxing’anling, photosynthetic capacity and microenvironmental factors (leaf temperature, light transmittance) of Korean pine needles in three positions in the gap (central, transition, and edge areas) were investigated. Three gaps were identified in the secondary Populus davidiana forest: a large 201 m² gap, a middle 112 m² gap, and a small 50 m² gap; 12 m² of the understory was sampled as a control. The results show that: (1) maximum net photosynthetic rate (P _max) in needles of Korean pine growing in the large gap was higher than in the small gap, and P_max in the centre in the same gap was higher than in the transition and edge areas; (2) light saturation point (LSP) and photosynthetic quantum yield (AQY) of needles in the large gap were higher than in the small gap, while the light compensation point (LCP) and chlorophyll contents of needles were lower in the small gap; and, (3) P _max had a significant positive correlation with temperature and light transmittance. It is suggested that the larger the gap in secondary Populus davidiana forests, the greater the change in light intensity and temperatures, the stronger the light adaption of Korean pine needles and the higher the photosynthetic capacity. Therefore, in the recovery of broad-leaved/Korean pine forests, suitable gaps should be created and gap microhabitats fully utilized to accelerate the restoration process.

Keywords

Pinus koraiensis / Gap size / Position in the gap / Maximum net photosynthetic rate