Ecological Indicators 18(2012) 559-566 Circular distributions of fallen logs as an indicator of forest disturbance regime Toshihiro Abe, Yasuhiro Kubota, Kenichiro Shimatani, Tuomas Aakala, Timo Kuuluvainen Ecological Indicators 18(2012) 559-566

どんな内容か・・・？ やること 倒木の方向をはかります しりたいこと 倒木の方向は、過去の森林撹乱体制の指標に用いることができるのか？ Measuring directions of fallen logs しりたいこと 倒木の方向は、過去の森林撹乱体制の指標に用いることができるのか？ Can Directional distributions of fallen logs be an indicator of past forest disturbance regimes？

背景 windthrow is important component of natural disturbance regime. (in the absence of severe disturbances...) senescene-related mortality of individual trees or small groups make small-scale gap dynamics. the functioning and role of wind as a disturbance factor may vary from case to case

背景 Forest structural attributes (tree species, size, spatial pattern…) are affected by the occurrence of wind-induced disturbances. to understand the mechanisms of forest dynamics...evaluate the vulnerability of forests against wind, and the magnitude and the ecological impact of windthrows.

背景 the vulnerability of forests against wind, and the magnitude and the ecological impact of windthrows. This information is also essential for developing ecosystem-based forest management (Natural Disturbance Emulation)

背景 Forest monitoring and wind damage monitoring can provide direct information of wind-caused disturbance. Retrospective studies using dendroecology may be used to infer longer-term disturbance regimes.

背景 Use of another type of data… The directions of fallen logs as an indicator of forest disturbance regimes, with special emphasis on the role of wind. Using measurements of log start and end points, or directions.

研究の意図 Examine the use of directional distributions of fallen logs as an indicator of past forest disturbance regimes. To do this we used data from three areas of primeval Picea abies-dominated boreal forests with contrasting disturbance histories.

調査地 Area 1: in the Pallas-Ylläs National Park Area 2: in the Kazkim river valley Area 3: in the Dvina-Pinega area 40m×400m plots Area 1: Plots 1-5 Area 2: Plots 7-11 Area 3: Plots 12-16

調査地

調査項目 all living and dead tree(DBH:10cm≦) ⇒mapped Tree species, DBH, Height dead tree⇒based decay classes The directions of fallen logs ⇒every 5°

調査項目

統計手法 circular statistics     The unit is radian, 0=east, π/2=north, π=west, 3/2π=south

統計手法 VM WC SSVM SSWC Symmetric circular distribution If the symmetry is rejected Skewed circular distribution SSVM SSWC

結果 Plot 7-11 in area 2 Plot 1-5 in area 1 Plot 12-17 in area 3

結果

考察

考察 Five curves of distributions of log directions within each are were similar Whereas, there appeared significant contrasts between the areas Between study areas> within study areas

考察 The results from the analyses of fall directions support the hypothesized differences in the role of wind in the disturbance regimes of the three areas. Area1: heart-rot fungi in combination with wind were the main causes of tree death Area2: single events can then have strong impact over the entire area Area3:tree mortality and intermediate disturbances

結論 Differences in the circular distribution patterns of fallen logs can be meaningfully related to essential characteristics of forest disturbance regimes. Directions of fallen logs can provide a new approach for making retrospective inferences about past forest disturbance regimes.