吉林蛟河针阔混交林乔木幼苗组成与月际动态

以吉林省蛟河42 hm²针阔混交林动态监测样地为平台, 在样地内选取224个1 m × 1 m幼苗监测小样方, 基于2013年6至8月每月中旬的幼苗监测数据, 对乔木幼苗物种组成、数量特征、月际动态及幼苗与同种大树之间的关系进行分析。结果表明: (1)该群落共调查到乔木树种幼苗16种。物种组成在6月和7月间变化不大, 但与8月差异较大。物种组成在各样方间表现出极大的差异性, 不同种幼苗出现的样方数为1-159。(2) 6月至8月, 幼苗个体从1722株减少到1214株, 降幅达29.5%。不同种幼苗在个体数量上变异较大, 个体数超过100的幼苗有色木槭(Acer mono)、水曲柳(Fraxinus mandschurica)、紫椴(Tilia amurensis)和东北槭(Acer mandshuricum), 四者个体数之和占所有物种个体总数的84.26%; 不同种幼苗密度变异性较大, 只有色木槭、水曲柳、紫椴和东北槭密度大于1株·m^-2, 其他种幼苗密度均较低。(3)新生幼苗更新、死亡格局表现出明显的种间差异与月际间差异, 7月新生幼苗总体死亡率(48.9%)显著高于8月(28.3%); 整个调查季(6-8月), 新生幼苗总体死亡率(40.56%)明显高于多年生幼苗(7.34%)。就幼苗更新情况而言, 该研究群落一年中更新主要集中在6月。(4)色木槭、紫椴、杉松(Abies holophylla)幼苗的密度与同种成年个体的胸高断面积之和之间存在显著的正相关关系(p = 0.006、0.013、0.037), 表明三者幼苗密度随周围母树多度的增加而增加, 其他物种幼苗密度与同种个体数目或同种胸高断面积之和未表现出显著的相关关系。

Composition and monthly dynamics of tree seedlings in a coniferous and broad-leaved mixed forest in Jiaohe,Jilin Province,China

The objective of this paper is to quantify the composition and dynamics of tree seedlings in the coniferous and broad-leaved mixed forest in north-eastern China. We installed 224 sampling quadrats (1 m × 1 m) at the Jiaohe Experimental Forest in Jilin Province of northeastern China. All seedlings in the quadrats were tagged and measured by species. Based on three consecutive sampling from mid-June to mid-August in 2013, we studied the species composition and dynamics of tree seedlings by month. Multiple linear regression was used to quantify the relationship between seedlings and the neighboring trees with the diameter at breast height (DBH) of 1 cm. A total of 16 species were recorded. There was no significant difference in species composition between June and July, but a great variation in the seedling composition in August. From June to August 2013, 1214 out of 1722 individual seedlings survived. There were significant differences in the total number and the number of individual species in the quadrats. The death and recruitment pattern of newborn seedlings showed significant differences among species and by month. The mortality rate in June was 48.9%, which was significantly higher than that in August (28.3%). The mortality rate of perennial seedlings during the observation period was 7.34%, which was significantly less than the mortality rate of new seedlings (40.56%). We found that the recruitment rate of the dominant species in July was higher than that in August. The recruitment occurred mostly in June. Multiple linear regression was used to analyze the relationship between the seedling abundance of eight species and the number of conspecifics, as well as the sum of conspecific basal areas within 20 m distance from a station. Factors influencing seedling abundance differed among species. For Acer mono, Tilia amurensis and Abies holophylla, significant partial regression coefficients appeared positive (p = 0.006, 0.013, 0.037, respectively), indicating that the seedling abundance increased with basal area. Other species did not show this correlation.