Kondo Katsushiko, Inouye David W, Segawa Michihara, Seki Tarou
Faculty of Integrated Arts and Sciences, Hiroshima University, Higashi-Senda-Machi, Naka-Ku, 730, Hiroshima, Japan.
Dept of Zoology, University of Maryland, 20742, College Park, MD, USA.
Oecologia. 1986 Sep;68(3):321-326. doi: 10.1007/BF01036733.
Demographic characteristics were examined in 51 study sites in naturally occurring pine populations in the Seto Inland Sea-side. The pine forests consisted on average of 51.4% Japanese red pine,Pinus densiflora, 28.9% Japanese black pine,Pinus thunbergii, and 19.7% hybrids of the two species, and occurred along an elevatinal gradient from denser, younger secondary forest regrowing after disturbance, to more mature stands at higher elevations. The proportion of dead trees did not vary much among taxa (range 24-31%). Mortality was caused primarily by the introduced pine wood nematodeBursaphelenchus xylophilus, and secondarily by its vector, the Japanese pine sawyer beetleMonochamus alternatus. While the nematode attacked individuals of all three pine taxa with equal frequency (3-8% mortality), the beetle caused the greatest proportional mortality inP. thunbergii (35%), less inP. densiflora (20%), and the least in hybrids (18%). Mortality caused by both the nematode and beetle was significantly correlated with the mean tree age, height and diameter of the dead trees.The majority (70.2%) of individuals in populations on Miyajima Island that had lived 60 or more years and survived without severe damage by nematodes and beetles were hybrids, although the proportion of hybrids in the seedlings (found only in seven out of the fifty-one study sites) was quite low (1.9%). Thus it seems that hybrids could be more long-lived and better adapted than their parental species to resist both the nematode and the beetle. IfB. xylophilus andM. alternatus populations continue to increase at their current levels they may have a drastic effect on the gene pools ofP. densiflora andP. thunbergii and on the structure and composition of Japanese pine forests.
对濑户内海沿岸天然松树林的51个研究地点的人口统计学特征进行了调查。这些松树林平均由51.4%的日本赤松（Pinus densiflora）、28.9%的日本黑松（Pinus thunbergii）和19.7%的这两个物种的杂交种组成，分布在一个海拔梯度上，从受干扰后重新生长的较密集、较年轻的次生林，到海拔较高处更成熟的林分。不同分类群中死树的比例变化不大（范围为24%-31%）。死亡主要由引入的松材线虫（Bursaphelenchus xylophilus）引起，其次由其传播媒介日本松墨天牛（Monochamus alternatus）引起。虽然线虫以相同频率攻击所有三种松树分类群的个体（死亡率为3%-8%），但天牛在黑松（P. thunbergii）中造成的比例死亡率最高（35%），在赤松（P. densiflora）中较低（20%），在杂交种中最低（18%）。线虫和天牛造成的死亡与死树的平均树龄、高度和直径显著相关。宫岛岛上存活60年或更长时间且未受到线虫和天牛严重损害的种群中，大多数个体（70.2%）是杂交种，尽管杂交种在幼苗中的比例相当低（仅在51个研究地点中的7个地点发现）（1.9%）。因此，杂交种似乎比其亲本物种更长寿，更能适应抵抗线虫和天牛。如果松材线虫和日本松墨天牛的种群继续以目前的水平增长，它们可能会对赤松和黑松的基因库以及日本松树林的结构和组成产生巨大影响。
