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本帖最后由 细胞海洋 于 2013-2-8 21:28 编辑 ( G% S' ]3 L1 u7 \
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# a3 k, A- z& |2 xAbout the
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Stretches of oak savanna
- O7 U# H2 `2 f" a) y; t/ s0 Z" D7 U- zin the Pacific Northwest of North America have been subject to fire-prevention
, J6 U3 p( l+ j7 Y6 P( J/ Wmeasures since the mid-nineteenth century. The resulting grassland has lost ! H- Z' X! @; p2 a
plant species but achieves stable high-yield annual production — rather like a
7 ?$ {3 y7 s5 \4 i. o, W( Ehigh-yield agricultural system — and remains resilient to invasive species and ; B$ A" x4 d$ |2 F( I, u
climate fluctuation. A long-term study in which $ ]& f; N3 a; v1 Z; O* [7 @
selected grassland plots were periodically burned and allowed to recover now
1 `% A" n! ^. p7 B( M% ademonstrates the critical value of biodiversity when ecosystems experience # q. j9 L# k# t$ F& A+ T
disturbance. Grasslands were able to recover from burning only in areas that had 9 G1 P" Z/ l( t
a relatively high diversity of native plants. This work demonstrates how ) N7 G, e j. K1 U
persistent human activity can homogenize both structure and function of an : ` {6 V0 j( l3 j7 C
ecological system, while weakening the diversity-related mechanisms needed to 7 e- }3 X0 p, ~8 w# J [
compensate for sudden disturbance. There are many terrestrial systems today that * P, V" o7 A V9 w7 S3 {
have become homogenized by persistent human activity that may be similarly
$ v# }- K" S f! U0 L. Bvulnerable to sudden environmental change that will be only evident after the . m' b& d4 d- |" g: l v. A- d
collapse occurs. On the cover 'grass fire' (Dariush - ?5 y5 h7 n+ a, O# M& w
M/Shutterstock).
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