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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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& R3 ] Y1 K S% g. TAbout the 6 v) @8 F& m3 N, F" n7 P
Cover
3 T6 q2 L" H s% Z( h' LStretches of oak savanna 1 D8 w# T3 p, c0 _2 g6 r+ f! J
in the Pacific Northwest of North America have been subject to fire-prevention
+ c& w! B+ H7 Q; l* A5 Nmeasures since the mid-nineteenth century. The resulting grassland has lost
; f/ w4 ~: t+ |/ k, o% Uplant species but achieves stable high-yield annual production — rather like a
( R0 V0 e& r! h4 H% H/ [high-yield agricultural system — and remains resilient to invasive species and ) |1 n7 o' y' ^: D& o6 T+ M
climate fluctuation. A long-term study in which 9 j8 C' C( r; q# `$ R! I3 Z/ ~
selected grassland plots were periodically burned and allowed to recover now
+ ^% [1 x/ r) W8 Zdemonstrates the critical value of biodiversity when ecosystems experience 7 E P* @* w/ ~& g2 G" C/ i3 M4 p- c
disturbance. Grasslands were able to recover from burning only in areas that had
0 h" r( E) n( B, i/ X1 D9 ca relatively high diversity of native plants. This work demonstrates how , I3 j! V! ?9 G7 U. k; T0 g
persistent human activity can homogenize both structure and function of an
7 `; d% w! m+ ~8 j2 Pecological system, while weakening the diversity-related mechanisms needed to
" \; H/ u1 }" W( x% X1 {8 ucompensate for sudden disturbance. There are many terrestrial systems today that
3 M/ o8 E. I1 Y6 W7 Vhave become homogenized by persistent human activity that may be similarly % x9 B3 A" h8 Y* a) s" Q; G
vulnerable to sudden environmental change that will be only evident after the " s% o- X# [; g3 }/ r) w
collapse occurs. On the cover 'grass fire' (Dariush 3 h# ^/ ?2 F9 r I
M/Shutterstock).
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7 Z7 z5 D2 X! k& _" M4 q9 J, e1 J
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发表于 2013-2-8 19:38
发表于 2013-2-15 22:45
