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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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About the
5 X" R$ n& I. [* ]2 N5 s9 I" @& u5 NCover
' D" y, ?. Z0 v6 AStretches of oak savanna
# h9 H e' z" U1 X Bin the Pacific Northwest of North America have been subject to fire-prevention
8 T# ~9 Y& N7 S! N1 R$ f& h6 mmeasures since the mid-nineteenth century. The resulting grassland has lost
9 t9 g' T. A- v5 G: Y/ Dplant species but achieves stable high-yield annual production — rather like a
7 K6 H1 r$ ~: A/ Whigh-yield agricultural system — and remains resilient to invasive species and 5 H2 b( p% f' H* C
climate fluctuation. A long-term study in which
$ l a. z1 n$ c) B$ T/ ?selected grassland plots were periodically burned and allowed to recover now
* h2 ?; b' K M# P; l/ v* bdemonstrates the critical value of biodiversity when ecosystems experience
5 J4 s4 A0 s# o% L: jdisturbance. Grasslands were able to recover from burning only in areas that had . n7 w T# d2 ?2 d; w; g9 H% Y
a relatively high diversity of native plants. This work demonstrates how
" s' q! l0 L+ b% X% i/ z' vpersistent human activity can homogenize both structure and function of an
: d% w+ q4 g# Y1 r: Y+ z% i" Tecological system, while weakening the diversity-related mechanisms needed to
1 _ |! u& s5 C: j7 Xcompensate for sudden disturbance. There are many terrestrial systems today that
o8 Q8 o; P, t9 _8 I2 n7 W4 [have become homogenized by persistent human activity that may be similarly ( i4 L+ y- X- L6 M3 J2 }: _
vulnerable to sudden environmental change that will be only evident after the & O e/ \' s4 X& s4 z4 B. \
collapse occurs. On the cover 'grass fire' (Dariush
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