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本帖最后由 细胞海洋 于 2013-2-8 21:28 编辑 0 c0 L, T3 m4 E4 H3 L& J
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) `% L3 e- [- a3 k5 `2 MAbout the
, J8 ?8 m$ F$ l' G' _0 D/ ECover
" o/ s9 w. i; O1 |Stretches of oak savanna + S* Y: c5 p( d. B$ e% u
in the Pacific Northwest of North America have been subject to fire-prevention
$ n4 h. G' [& o0 A c: Jmeasures since the mid-nineteenth century. The resulting grassland has lost
+ F- k& o: m Wplant species but achieves stable high-yield annual production — rather like a `/ q7 B }6 |+ [5 S/ ]3 f( f# B
high-yield agricultural system — and remains resilient to invasive species and
. D5 J- z( {4 Q2 p& r& C9 `: C6 P Yclimate fluctuation. A long-term study in which 6 L/ I: G- V4 [. D/ }
selected grassland plots were periodically burned and allowed to recover now 8 S$ b) s+ W- J) Y* W4 I$ d$ H0 i
demonstrates the critical value of biodiversity when ecosystems experience
) P! r, r0 { u- ]* U' b1 E/ Kdisturbance. Grasslands were able to recover from burning only in areas that had
& n% q% |8 q, T3 N! U' K$ ^a relatively high diversity of native plants. This work demonstrates how
: x4 g$ P- A/ {0 Gpersistent human activity can homogenize both structure and function of an
/ f' Z; [, { v, Q" V$ Y+ N Qecological system, while weakening the diversity-related mechanisms needed to e3 l/ Q0 [- B# F- M6 d2 Q7 B
compensate for sudden disturbance. There are many terrestrial systems today that 8 _: L' Q6 I' l, T, C7 g
have become homogenized by persistent human activity that may be similarly & q3 ]% k9 @9 B6 m$ J* A: _
vulnerable to sudden environmental change that will be only evident after the
1 ~- d" }$ y* f, z% wcollapse occurs. On the cover 'grass fire' (Dariush
@$ N+ A0 y8 {- h6 T' V# e* UM/Shutterstock).
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7 D+ e# F" F/ a9 V! p& s3 B. U, I, B H, {
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发表于 2013-2-8 19:38
发表于 2013-2-15 22:45
