Heterogeneity of soil surface temperature and shallow soil temperature in different size gaps of broadleaved Pinus koraiensis forest

Objective Exploring the dynamic changes of surface temperature and shallow soil temperature in different gaps aims to provide theoretical basis for seedling regeneration, biodiversity maintenance and ecological environment restoration of broadleaved Korean pine mixed forest.

Method Taking the gaps and small gaps in broadleaved Pinus koraiensis forest in Xiaoxing’an Mountains, northeastern China as research object, the ground temperature meter and the shallow soil thermometer observation points were respectively arranged by grid method and cross line method to measure the ground temperature, ground minimum and maximum temperature, and shallow (5, 10, 15 and 20 cm) soil temperatures with their spatiotemporal heterogeneity in the gaps during growth season, analyzed by the classic statistics and geostatistical methods from June to September in 2010.

Result (1) The diurnal variation of surface temperature from June to September presents a single-peak curve, which increased firstly and then decreased, and reached its maximum in July. The increase of surface temperature was faster than that of cooling, and the range of temperature rising was larger than that of cooling. (2) From June to September, the change of ground temperature was as follows: middle gap > small gap > canopy stand, and the change of maximum ground temperature between plots was consistent with that of ground temperature, while the lowest temperature was opposite. (3) The spatial variability of soil temperature was different in each month. The variability of soil temperature was weak in July and August, moderate in June and September, and decreased with the increase of soil depth. (4) The daily mean surface temperature and soil temperature of gaps were higher than those of canopy stands, and the maximum area of gap soil temperature changed with time. The diurnal variation of surface temperature and soil temperature in gap center was higher than that in canopy stand. There was no significant difference between different soil layers in medium and small gaps. (5) The soil temperature showed weak variation in July and August, and moderate variation in June and September.

Conclusion Spatial heterogeneity of surface temperature and shallow soil temperature may directly affect seed germination and seedling growth, or indirectly affect seed bank and renewal by affecting the activities of soil microorganisms.