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Spatial pattern of post-fire forest succession in Central Kamchatka, Russia
Ishii, Hiroaki;Homma, Kosuke;Dolezal, Jiri;Hara, Toshihiko;Sumida, Akihiro;Vetrova, Valentina;Vyatkina, Marina;Hotta, Kana
Permalink : http://hdl.handle.net/2115/59059
JaLCDOI : 10.14943/lowtemsci.73.1
Abstract
北方林において森林火災は重要な自然かく乱であるが,極東ロシアにおいては,ソ連邦崩壊後の社会経済情勢に変化により,人為的な森林火災が増加している.本研究では,カムチャッカ半島中央部において火災後の植生回復年数が異なる３か所の林分で調査を行い,構成種による生存率と更新様式の違いが火災後の植生遷移にどのように影響するかを考察した.火災後２年目の林分では,Populus tremulaとBetula platyphyllaがそれぞれの更新様式（根萌芽および幹萌芽）に応じて,3mおよび0.5mのスケールで集中分布していた.火災後40年目の林分では,種子由来のLarix cajanderiが8 mのスケールで集中分布していた.火災後200年目の林分では,B.platyphyllaの株とL.cajanderiがともにランダム分布しており,B.platyphyllaの萌芽は個体群の更新・成長ではなく株の維持を担っていた.Bray-Curtis法による解析の結果から,火災後のP.tremulaおよびB.platyphyllaの相対的な生存率の違いによって,二次遷移の方向性が異なる可能性が示唆された.今後,カムチャッカ半島において人為による火災頻度が高くなれば,P.tremulaおよびB.platyphyllaが優占する遷移初期の森林が拡大し,L.cajanderiの個体群は減少すると考えられる.一方,火災が抑制されれば,L.cajanderiおよびB.platyphyllaが優占する遷移後期林が拡大するだろう.
Fire is a natural component of vegetation dynamics in boreal forests. However, in Far East Russia, socio-economic changes following the dissolution of the Soviet Union have resulted in increased incidences of human-caused forest fires. Here,we compared the species composition and stand structure among three forest stands at various stages of recovery after fires in Central Kamchatka, to infer how intraspecific differences in regeneration strategies and subsequent patterns of survival affect post-fire forest succession. At 2 years after a fire, sprouted stems of Populus tremula and Betula platyphylla were clustered according to their modes of sprouting;root suckers at the 3-m scale, and stump sprouts at the 0.5-m scale, respectively. At 40 years after a fire,stems of Larix cajanderi originating from seeds were clustered at an 8-m scale. At 200 years after a fire, clumps of B. platyphylla and L. cajanderi were both randomly distributed and the clumps of B. platyphylla were maintained by sprouting. Bray-Curtis ordination analyses suggested that there may be multiple pathways of post-fire succession depending on the relative survival rates of P. tremula and B. platyphylla. If fire-return intervals become shorter in Central Kamchatka because of more frequent human-caused fires,the population size of L. cajanderi will decrease and early successional forests comprising P. tremula and B. platyphylla will dominate the landscape. On the other hand,if fires are suppressed,late-successional forests comprising L. cajanderi and B. platyphylla will dominate the landscape.
Fire is a natural component of vegetation dynamics in boreal forests. However, in Far East Russia, socio-economic changes following the dissolution of the Soviet Union have resulted in increased incidences of human-caused forest fires. Here,we compared the species composition and stand structure among three forest stands at various stages of recovery after fires in Central Kamchatka, to infer how intraspecific differences in regeneration strategies and subsequent patterns of survival affect post-fire forest succession. At 2 years after a fire, sprouted stems of Populus tremula and Betula platyphylla were clustered according to their modes of sprouting;root suckers at the 3-m scale, and stump sprouts at the 0.5-m scale, respectively. At 40 years after a fire,stems of Larix cajanderi originating from seeds were clustered at an 8-m scale. At 200 years after a fire, clumps of B. platyphylla and L. cajanderi were both randomly distributed and the clumps of B. platyphylla were maintained by sprouting. Bray-Curtis ordination analyses suggested that there may be multiple pathways of post-fire succession depending on the relative survival rates of P. tremula and B. platyphylla. If fire-return intervals become shorter in Central Kamchatka because of more frequent human-caused fires,the population size of L. cajanderi will decrease and early successional forests comprising P. tremula and B. platyphylla will dominate the landscape. On the other hand,if fires are suppressed,late-successional forests comprising L. cajanderi and B. platyphylla will dominate the landscape.
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