ABSTRACT
The aims of this study were to clarify the regeneration characteristics and dominant factors affecting the regeneration of three natural Juniperus forests in the Three-River Headwater Region of Qinghai Province, and thus to provide a reference for the protection and management of natural forests. We evaluated the natural regeneration levels of Juniperus forests, and the effects of stand factors and soil factors on natural regeneration. The results showed that three natural Juniperus forests were poorly regenerated, with insufficient regeneration potential. The average regeneration density of J. tibetica forest, J. przewalskii forest and J. convallium forest was 332, 279 and 202 ind·hm-2, respectively. The height range of regenerate individuals was concentrated in 1-3 m. Only a few seedlings (12 ind·hm-2) were found under the J. tibetica forest, and no seedlings were found under the J. convallium and J. przewalskii forests. The regeneration density of J. tibetica forest was significantly positively correlated with stand density, soil organic matter and available phosphorus, and negatively correlated with shrub coverage. The regeneration density of J. convallium forest was significantly negatively correlated with herb coverage, human disturbance degree, woodland slope and soil total nitrogen, and positively correlated with soil water content. The regeneration density of J. przewalskii forest was significantly positively correlated with stand density, soil available potassium and available phosphorus, but negatively correlated with herb coverage. Results of multiple regression analysis showed that the regeneration of J. tibetica forest was mainly affected by understory shrub coverage and soil available phosphorus, that of J. convallium forest was mainly affected by understory herb coverage, soil total nitrogen and human disturbance, and that of J. przewalskii forest was mainly affected by understory herb coverage and soil available potassium. It was necessary to strengthen forest enclosure, management and protection, rationally regu-late the coverage of understory vegetation, increase soil fertility and improve biotope in the forest, which would promote the protection and natural regeneration of natural Juniperus forests in the Three-River Headwater Region.
