巴山冷杉-牛皮桦混交林乔木更新及土壤化学性质对更新的影响

调查太白山巴山冷杉-牛皮桦混交林林下与林隙乔木更新及土壤化学性质,分析林隙及土壤化学性质对乔木更新的影响.结果表明:巴山冷杉-牛皮桦混交林乔木更新苗密度较小,为0.059株·m-2,但林下与林隙均以巴山冷杉更新苗为主；林下与林隙乔木更新苗密度差异不显著(P=0.160),但巴山冷杉幼苗密度表现为林隙内显著高于林下(P =0.012)；相关分析表明,小林隙更利于巴山冷杉更新(r=- 0.397,P=0.030),而林隙大小对牛皮桦更新没有显著影响(r=0.125,P=0.511)；在林下,土壤碱解N、全P含量和pH值与牛皮桦更新苗密度呈显著正相关；在林隙内,土壤全P和有效P含量与巴山冷杉更新苗密度呈显著负相关,全P含量与牛皮桦幼树密度呈显著负相关；林下土壤有机质含量、全N含量和有效P含量及林隙土壤pH值、有机质含量、全N含量和碱解N含量与牛皮桦和巴山冷杉更新苗密度均没有显著相关关系；林下土壤pH值显著高于林隙,而有机质、全N、碱解N、全P和有效P含量显著低于林隙.

Tree Regeneration in an Abies fargesii-Betula utilis Mixed Forest and Effects of the Soil Chemical Properties on Regeneration

Tree regeneration understory and in gaps of an Abies fargesii-Betula utilis mixed forest and the soil chemical properties were investigated in Taibai Mountain, China, and the effects of gaps and the soil chemical properties on tree regeneration were analyzed. The results showed that there was low tree regeneration density in the Abies fargesii-Betula utilis mixed forest (0.059 trees·m-2), but the regeneration amount of Abies fargesii was dominant no matter in gap or understory. The difference of tree regeneration densities was not significant between understory and in gap (P=0.160), however, the seedling density of Abies fargesii in gap was significantly higher than in understory (P=0.012). Correlation analysis indicated that small gaps were more conducive to the regeneration of Abies fargesii (r=-0.397,P=0.030), while gap size had no significant effect on the regeneration of Betula utilis (r=0.125,P=0.511). In understory, the regeneration density of Betula utilis was significantly positively correlated with soil alkali-hydrolyzable N content, total P content and pH. In gap, the regeneration density of Abies fargesii was significantly negatively correlated with soil total P content and available P content, and the sapling density of Betula utilis was significantly negatively correlated with soil total P. The other soil chemical properties understory (organic matter content, total N content and available P content) and in gaps (pH, organic matter content, total N content and alkali-hydrolyzable N content) had no significant correlation with the regeneration densities of Betula utilis and Abies fargesii. Soil pH was significantly higher in understory than in gaps, whereas organic matter content, total N content, alkali-hydrolyzable N content, total P content and available P content were significantly lower than in gaps.