差分表示
#freeze
https://www.facebook.com/yunikayama/posts/10215094616148631
https://en.wikipedia.org/wiki/Continuous_cover_forestry
http%3A%2F%2Fforestry.oxfordjournals.org%2Fcontent%2F77%2F1%2F27.full.pdf&h=ATN-70IM9KOeOBEoIDvStKJSdKaw8oTqvO5MNVbTLI3LfizigCmjVepcxusbI9zKA806rXdaQs4r-U93fD8HXS5LwwZpCq-C9ztp6TBPHBk2eY2VNCO9hR6KGteS8QlPC2HpKHIReqauOUnfp8jRIVNE2XPtJjNxw8Z0A5yiPJYQTKXgk4MTMs-2gl41R0OzXS2dVdPy-hGzPfLKXMgLigfylw8oLtnjos-rBQt82t4U7nyG3eXEnxZYCUK_tU6E7tvdVJWrQ0T4_iHIP2oQ8dbxL8ou4jKkBE-LHzClNCs
http://forestry.oxfordjournals.org/content/77/1/27.full.pdf
https://de.wikipedia.org/wiki/Dauerwald