(Japanese Journal of Conservation Ecology) 17 : 185-197 (2012) 1, * 1 2 3 4 5 1 2 3 4 5 Changes in the understory vegetation due to the decrease in sika deer density in Akan National Park, eastern Hokkaido, Japan Yoshihiro Inatomi 1, *, Hiroyuki Uno 1, Yachiyo Takashima 2, Kazuyuki Onimaru 3, Masami Miyaki 4 and Koichi Kaji 5 1 Institute of Environmental Sciences, Hokkaido Research Organization, 2 Hokkaido University of Education Kushiro Campus, 3 Bihoro Museum, 4 Rakuno Gakuen University, 5 Faculity of Agriculture, Tokyo University of Agriculture and Technology 1993 2009 1995 2010 1993 27.1 ± 10.7 /km 2 2009 9.5 ± 2.5 /km 2 1994 1998 1999 9 15 2 Abstract: We conducted aerial surveys of the sika deer (Cervus nippon yesoensis) population in Akan National Park, eastern Hokkaido, Japan, between 1993 and 2009 to assess the effects of doe hunting and managed culls on deer density. We also surveyed the cover and height of understory plants in exclosure and control sites between 1995 and 2010 to examine changes in the understory vegetation in response to decreasing deer density. The aerial survey showed that deer density decreased from 27.1 ± 10.7 deer/km 2 in 1993 to 9.5 ± 2.5 deer/km 2 in 2009. The data suggest that hunting females and culling herds caused the decrease in deer density, as the population began to decline after doe hunting was allowed in 1994, decreased sharply in response to the deregulation of doe hunting in 1998, and was maintained at a low level after 1999 when managed culls were begun. We analyzed the cover and height of 15 palatable and two unpalatable plants in the understory vegetation. In the sites where hunting and culls were conducted, the cover or height of three palatable plants (Sasa senanensis, Thalictrum ssp., and Trillium ssp.) increased, and an unpalatable plant (Senecio cannabifolius) disappeared in parallel with decreasing deer density. This suggests that management of deer density has allowed understory vegetation to recover by reducing browsing pressure. We conclude that population control of sika deer is an effective measure to foster recovery of understory vegetation damaged by high browsing pressure from deer. Keywords: aerial survey, cull, female hunting, palatable plants, unpalatable plants * 085-8588 2 2-54 Eastern Hokkaido Wildlife Research Station, Institute of Environmental Sciences, Hokkaido Research Organization, 2-54, Urami 2, Kushiro, Hokkaido 085-8588, Japan e-mail: inatomi@hro.or.jp 2011 12 27 2012 7 25 185
Rooney 2001 Rooney and Waller 2003 Cervus nippon Akashi and Nakashizuka 1999 Yokoyama et al. 2001Yokoyama and Shibata 1998 Nomiya et al. 2002 2011 2005 2007 2011 2010 C. nippon yesoensis 2007 2004 Empetrum nigrum L. var. japonicum K. Koch 2003 2010 Sasa borealis (Hack.) Makino et Shibata 2005 2007, 2008 Sasa nipponica (Makino) Makino et Shibata Itô and Hino 2005 Kumar et al. 2006 1994 Uno and Kaji 2000 1995 2011 1994 Kaji et al. 2010 1999 9 1 2011 1993 2002 Uno et al. 2006 2003 2004 2008 2009 1995 2010 調査地域の概要 87.1 km 2 1 43.43 144.09 430 m 1995 2010 4.1 1228 mm 129.1 cm http://www.jma.go.jp/jma/index.html 2011 8 24 186
Abies sachalinensis (F.Schmidt) Mast. Picea jezoensis (Siebold et Zucc.) Carrière Ulmus davidiana Planch. var. japonica (Rehder) Nakai Quercus crispula Blume Acer pictum Thunb. ex Murray ssp. mono (Maxim.) Ohashi Tilia japonica (Miq.) Simonk. 1994 64 728 792 1994 1999 9 2010 3 3563 2011 1994 1996 10 1996 8 10 1997 61 31 1998 92 1 1 2 2007 Kaji et al. 2010 航空機調査 Uno et al. 20061993 1994 1997 2002 2 3 2003 2004 2008 2009 2 3 Uno et al. 2006 87.1 km 2 7.2 km 2 11.4 km 2 9 1 137.1 km 2 80 km/h 100 m 1 km 2 3 2 6 /km 2 2003 2004 2008 2009 SCF 0 Gasaway et al. 1986 Uno et al. 2006 n 0 w k k v k 9 1 林床植生調査 1995 8 3 A B D 3 E F G 1 C 1 10m 20m 1995 2009 B C E F G 3 m 2 /ha 1 1995 E G 2009 A C B 1 2m 2m 1m 1m cm 0.10.1 1995 2002 2004 2005 2007 2010 7 187
1 1995 2009 m 2 /ha 1995 2009 1995 2009 A 20.3 23.1 30.4 38.9 5.0 4.9 48.8 54.9 B 51.4 70.3 11.0 11.7 40.3 49.3 12.8 15.9 C 0.0 0.0 0.0 0.1 0.0 0.0 5.4 10.0 D 5.5 6.9 35.6 38.7 6.3 9.1 21.2 23.9 E 0.0 0.0 42.7 32.3 0.5 2.6 38.8 40.7 F 0.0 0.0 26.3 18.5 2.7 1.5 34.4 43.2 G 0.0 0.1 31.6 22.9 0.0 0.6 55.4 36.2 8 1981 6 10 101995 2007 Senecio cannabifolius Less. Pteridium aquilinum (L.) Kuhn 2007 Thalictrum minus L. var. hypoleucum (Siebold et Zucc.) Miq. Trillium camschatcense Ker Gawl. Thalictrum baicalense Turcz. ex Ledeb. Thalictrum sachalinense Lecoy. Trillium tschonoskii Maxim. Thalictrum spp. Trillium spp. I 1995 1999 II 2000 2005 7 III 2006 2010 3 エゾシカ生息密度の推移 1.3952 2.0580 2 1993 27.1 ± 10.7 /km 2 ± 1999 9.2 ± 5.0 /km 2 2 2000 22.4 ± 8.8 /km 2 2001 2004 12.2 /km 2 13.4 /km 2 2008 2009 6.6 ± 2.0 /km 2 9.5 ± 2.5 /km 2 林床植生の変化 Sasa senanensis (Franch. et Sav.) Rehder 3 1995 A 3.8 2 F 18.0 I A I II 5 III 2009 4 I II A Carex sachalinensis F. Schmidt var. sachalinensis I III 50 4 188
22002 Uno et al. 2006 n 0 SCF 0 v k w k k=1 k=2 k=3 k=4 k=5 k=6 k=7 k=8 k=9 k=1 k=2 k=3 k=4 k=5 k=6 k=7 k=8 k=9 1993/94 5 1.3952 49 22 59 80 111 66 40 81 140 126 1997 0-1998 2-34 38 71 95 1999 5 1.7733 8 60 45 25 13 10 128 59 42 25 2000 7 1.7632 54 26 56 53 35 23 18 75 26 122 96 67 55 25 2001 9 2.0216 43 40 28 37 44 55 41 21 26 91 91 72 70 114 76 77 48 40 2002 8 1.6570 60 15 24 32 36 22 32 46 93 27 53 48 74 56 44 51 2003 7 1.9869 107 4 28 21 2 11 32 216 25 48 35 12 16 57 2004 6 1.3922 144 25 16 44 19 63 186 51 34 62 26 84 2008 5 2.0580 22 23 6 8 7 52 23 18 8 42 2009 8 1.5162 49 89 23 28 57 20 53 21 105 89 51 62 97 44 56 21 2 D E I F I B D E III 5 B D II B D Pachysandra terminalis Siebold et Zucc. Carex pilosa Scop. C I II Petasites japonicus (Siebold et Zucc.) Maxim. subsp. giganteus (G.Nicholson) Kitam. 50 II I G 1981 19952007 15 2 3 F G A Impatiens nolitangere L. E Cirsium kamtschaticum Ledeb. ex DC. C E F 5 5 6 F G C E A I A II II 2005 G A II III 189
3 I 1995 1999 II 2000 2005 III 7 2006 2010 190
シカ密度の低下に伴う林床植生の変化 図 4 A 区の対照区における林床植生の変化 a クマイザサ とオシダが優占し 全体の植被率は低かった 1995 年 8 月 撮影 b サハリンイトスゲが高い被度で優占する林床 に推移し クマイザサは消失した また トドマツの稚樹 もみられた 2009 年 8 月撮影 図 5 E 区の対照区における林床植生の変化 a エゾイラク サや不嗜好性植物のハンゴンソウが優占していた 1998 年 8 月撮影 b クサソテツとクマイザサが増加し ハンゴ ンソウは消失した 2009 年 8 月撮影 向を示したものの シカ排除区より増加の開始時期は遅 考 かった また I 期の対照区とシカ排除区におけるカラ 察 マツソウ属 F 区 の被度 III 期の対照区と I 期のシカ メスジカ狩猟の解禁と個体数調整がエゾシカの生息密度 排除区におけるエンレイソウ属 A 区 の植物高の増加 に与えた影響 幅は 対照区に比べてシカ排除区で大きかった 対照区 航空機調査の結果 阿寒国立公園における 2008 年と におけるエンレイソウ属 A 区 は III 期に植物高が 2009 年におけるエゾシカの生息密度は 2001 年 2004 増加傾向を示した一方で 被度に顕著な変化はみられな 年より低い傾向を示した 図 2 電波発信機を用いた かった エゾシカのテレメトリ調査では 積雪条件によって越冬 対照区とシカ排除区の双方に出現し どちらかの最大 地を変える個体の存在が確認されている Uno and Kaji 被度が 5 以上を示した不嗜好性植物の被度及び植物高 2000 が 2008 年の阿寒湖アメダス観測所における最 の推移を図 7 に示す ハンゴンソウ E 区 は シカ排 深積雪深は 1993 年以降で最も少ない 75 cm 気象庁ホ 除区の被度が非常に小さかったのに対し 対照区では ームページ http://www.jma.go.jp/jma/index.html 2011 年 1996 年に 22.5 に達した後 減少傾向を示し 2000 年 8 月 24 日確認 だったため 多くの個体が越冬地を変え に消失した 図 5 ハンゴンソウ F 区 は シカ排除 生息密度が低くなった可能性が考えられる その一方で 区で 2002 年 対照区で 2001 年に消失した 2000 年の生息密度は 前後年に比べて極端に高かった 191
3 5 A B C D E F G Thalictrum ssp. 3.5 0.8 4.0 10.0 0.6 0.1 10.8 20.0 Cardamine leucantha 1.1 2.1 1.0 Trifolium repens 0.1 Impatiens noli-tangere 2.3 0.1 0.1 0.5 0.3 1.0 0.8 0.3 0.1 17.0 0.5 Angelica sachalinensis var. sachalinensis 0.3 8.8 Pleurospermum uralense 1.3 Sanicula chinensis 0.3 1.3 3.3 0.3 Artemisia montana 0.1 11.8 Cirsium kamtschaticum 0.3 1.3 0.3 1.5 5.0 7.5 0.3 7.5 Picris hieracioides subsp. japonica 0.3 0.1 0.1 0.1 Cardiocrinum cordatum var. glehnii 0.3 Polygonatum odoratum var. maximowiczii 0.5 0.3 0.8 0.8 Trillium ssp. 0.3 0.1 0.5 1.5 14.8 1.0 1.3 2.6 1.3 Calamagrostis langsdorffii 3.0 Sasa senanensis 4.5 57.5 60.0 72.5 22.5 77.5 82.5 46.3 50.0 68.8 70.0 66.3 68.8 78.8 Cynanchum caudatum 3.5 0.1 0.5 Senecio cannabifolius 0.5 2.5 2.5 22.5 5.0 3.0 0.3 2.5 192
6 5 2Uno and Kaji 2000 2000 1993 2 107 cm http://www.jma.go.jp/jma/index.html 2012 5 6 31000 km 2 1997 2002 Kaji et al. 2010 1993 27.1 /km 2 1999 9.2 /km 2 2001 2004 12.2 /km 2 13.4 / km 2 2009 9.5 ± 2.5 /km 2 2002 Uno and Kaji 2006 1994 1998 193
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