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本帖最后由 细胞海洋 于 2013-2-8 21:28 编辑
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) V* I9 v0 Z( l4 v# W7 g8 ]About the
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Stretches of oak savanna
6 \1 W- r! Q1 x6 X2 `9 ]5 P% Y$ Din the Pacific Northwest of North America have been subject to fire-prevention
+ z! y9 j! w1 `; Emeasures since the mid-nineteenth century. The resulting grassland has lost
2 N, W6 [7 j# f3 h! Uplant species but achieves stable high-yield annual production — rather like a 9 i$ ^( G6 I8 N! f" X1 k( N( ?
high-yield agricultural system — and remains resilient to invasive species and " _4 n* M/ V' A2 b% b. d
climate fluctuation. A long-term study in which 5 o) }+ i0 r5 H
selected grassland plots were periodically burned and allowed to recover now
' }7 C) G8 ^& Z1 l" T9 Q- A" x9 f4 rdemonstrates the critical value of biodiversity when ecosystems experience
: W0 t2 U! [& d( Gdisturbance. Grasslands were able to recover from burning only in areas that had
- x! `7 s4 M7 Sa relatively high diversity of native plants. This work demonstrates how $ ]5 o) `, S1 m& Y7 B, P
persistent human activity can homogenize both structure and function of an
3 _2 ]2 x/ R% q$ D6 }0 w/ q5 F& i! Wecological system, while weakening the diversity-related mechanisms needed to ( e* ?" t- [! K4 D* a
compensate for sudden disturbance. There are many terrestrial systems today that [% G: j+ m- {! m1 `; W
have become homogenized by persistent human activity that may be similarly
" r% L7 P5 Y& O; W+ ^6 m. f: {vulnerable to sudden environmental change that will be only evident after the ! T8 q( a2 q9 I8 M& ^! U
collapse occurs. On the cover 'grass fire' (Dariush
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发表于 2013-2-8 19:38
发表于 2013-2-15 22:45
