森林立地学会誌 森林立地 51(1),2009,27〜37
Jpn.J.For.Environment 51(1),27―37
2009
日本における常緑カシ類2種の個体および優占林の分布を規定する気候条件
中尾勝洋1・松井哲哉2・田中信行2・福嶋 司1
1東京農工大学連合農学研究科・2森林総合研究所
アカガシとウラジロガシの分布を規定する気候要因と閾値を分類樹解析を用いて明らかにした。種ごとに(1)個体の分布(SP-model)と(2)優占林の分布(DO-model)の2つをそれぞれ従属変数とし,暖かさの指数(WI),最寒月最低気温(TMC),夏期降水量(PRS),冬期降水量(PRW)の気候要因を独立変数とした。その結果,個体ではTMC,優占林ではWIが分布を規定する主要な要因であった。個体分布では2種ともにTMC約−5℃以上で分布適域となり,この閾値は常緑広葉樹林の耐性限界温度とされる最寒月平均気温−1℃とほぼ一致した。2種ともに優占林の分布適域のWIは個体に比べて狭く,寒冷な条件に偏っていた。個体と優占林とも,アカガシがPRS約1,500 mm以上の多雨な太平洋側で,ウラジロガシがPRS1,034 mm以上の太平洋側と日本海側で出現確率が高くなっていた。PRWは,ウラジロガシで著しく出現確率を低下させないが,アカガシではPRWの多い地域で出現確率を低下させていた。
キーワード:アカガシ,ウラジロガシ,分類樹解析,適域,最寒月最低気温
Katsuhiro
Nakao, Tetsuya Matsui, Nobuyuki Tanaka and Tukasa Hukusima:Climatic
controls of the distribution and abundance of two evergreen Quercus species in Japan. Japanese Journal of Forest Environment
51:27−37, 2009.
We developed statistical distribution models for two
evergreen Quercus species(Q. acuta
and
Q. salicina)by using classification tree
analyses with phytosociological relevè data, in Japan. Two different models
were constructed for each of the two species:(1)species at least present(SP-model)and (2)species dominant in the
canopy layer(DO-model). Four climate variables:warmth index(WI), temperature of the coldest month(TMC), summer precipitation(PRS)and winter precipitation(PRW), were used as predictor
variables. WI and TMC were the most influential factors for each of the two
species. The lower temperature range of each species was generally coincided
with the averaged minimum temperature of the coldest month warmer than or equal
to −1℃ The DO-models for the
two species were mainly contributed by WI, and the predicted optimal habitats
were narrower than those of the SP-models. The predicted distributions for the
two species were similar to the geographical patterns of PRS. Specifically, Q. acuta was mainly predicted to occur under high precipitation
conditions, such as on the western part of the Kanto region on the Pacific Ocean
side. On the other hand, Q. salicina was predicted to occur both on the
Pacific Ocean side and the Sea of Japan side. PRW was influential factors for
the DO-models. Q. acuta was predicted to occur under low PRW
conditions.