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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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7 G5 R3 l w {! A0 `- `. X" I+ @About the
: T) E u! I( M% f" [; ~/ Y n5 bCover" f* y3 ?8 D! N) C. X- c/ w2 F, W
Stretches of oak savanna
O3 {- n: \+ l: uin the Pacific Northwest of North America have been subject to fire-prevention
( |4 ~5 y6 N; a) e8 }5 cmeasures since the mid-nineteenth century. The resulting grassland has lost
7 E) R/ P" T4 ^3 z6 [plant species but achieves stable high-yield annual production — rather like a
8 k C" o) w7 B# lhigh-yield agricultural system — and remains resilient to invasive species and
{7 J6 i x6 `1 Oclimate fluctuation. A long-term study in which
- Q5 C, f: \- i O9 q- \2 i6 uselected grassland plots were periodically burned and allowed to recover now
- p: e7 Q7 E! h3 c6 V5 _& qdemonstrates the critical value of biodiversity when ecosystems experience
6 p) A8 T# N& I9 Y5 b: ^disturbance. Grasslands were able to recover from burning only in areas that had * t. {! s2 A4 F" g$ U. ]% g1 H
a relatively high diversity of native plants. This work demonstrates how
3 y& K; |0 @. f# Dpersistent human activity can homogenize both structure and function of an 2 i* E& f1 h) c+ P
ecological system, while weakening the diversity-related mechanisms needed to ' |( j( O4 I6 @1 g; H
compensate for sudden disturbance. There are many terrestrial systems today that
3 H" @, Z" Y9 p m9 Dhave become homogenized by persistent human activity that may be similarly - ?) }8 Y) S9 e; [4 s \
vulnerable to sudden environmental change that will be only evident after the ) E5 o7 @2 u/ \& e! b
collapse occurs. On the cover 'grass fire' (Dariush
! y( X5 s8 o- I) ~4 [6 IM/Shutterstock).
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发表于 2013-2-8 19:38
发表于 2013-2-15 22:45
