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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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% Q: _7 p0 w" f* _" E4 r, h6 o! f; QAbout the 6 M- S/ m. e: R7 \* ?/ N
Cover
1 L8 P) C- X) s8 h6 b# j4 IStretches of oak savanna % ]) n, G' z/ h, v; _6 H
in the Pacific Northwest of North America have been subject to fire-prevention # E6 y. q- } R& `
measures since the mid-nineteenth century. The resulting grassland has lost 2 f6 B- \, H# w% v. }) X2 i) z" s8 Q
plant species but achieves stable high-yield annual production — rather like a 8 U2 O5 g" K! b7 k& L
high-yield agricultural system — and remains resilient to invasive species and - x' A! _5 P( s, a1 ], y. K
climate fluctuation. A long-term study in which
; s) w5 q! ^( Z& fselected grassland plots were periodically burned and allowed to recover now
. H+ j) [2 Y, K# Gdemonstrates the critical value of biodiversity when ecosystems experience " E# @6 N* K( x) F
disturbance. Grasslands were able to recover from burning only in areas that had - I2 f5 n$ O5 L
a relatively high diversity of native plants. This work demonstrates how
% w/ J3 \& D2 d2 h. ^3 r3 X* `: F1 @persistent human activity can homogenize both structure and function of an
. O6 z8 ~6 A9 J1 l% Y2 D/ {ecological system, while weakening the diversity-related mechanisms needed to
7 n7 _* v- Z2 B) k2 Ncompensate for sudden disturbance. There are many terrestrial systems today that
4 z/ {/ L( ]8 f2 K, I, u1 p- Ehave become homogenized by persistent human activity that may be similarly
* i$ `( Z: q% y' b8 ^" c9 Ovulnerable to sudden environmental change that will be only evident after the w9 t- D* q2 |5 E) ?: @
collapse occurs. On the cover 'grass fire' (Dariush
1 W1 Y+ W1 i# eM/Shutterstock).
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发表于 2013-2-8 19:38
