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本帖最后由 细胞海洋 于 2013-2-8 21:28 编辑 + X, s4 c; ~; m# D0 F' d
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* E3 Q+ q8 e( q$ y, R( yAbout the 5 K; ^- }2 q$ N. O# r4 `# W
Cover
5 {; w0 d: X+ Q: a7 m( G" dStretches of oak savanna
& {1 p+ W, Q/ h# k, zin the Pacific Northwest of North America have been subject to fire-prevention
9 f. Y ~, ]9 }9 F/ x- \measures since the mid-nineteenth century. The resulting grassland has lost 9 i( {! t& w8 E" h \; \
plant species but achieves stable high-yield annual production — rather like a 5 g ]- o+ T M3 ], K" R
high-yield agricultural system — and remains resilient to invasive species and
Z. Z2 q+ W7 C5 U" Y! ]! E2 ^climate fluctuation. A long-term study in which 7 g, t* ]1 x* F0 D( _0 y
selected grassland plots were periodically burned and allowed to recover now + l: I7 g1 f2 ~; }5 @
demonstrates the critical value of biodiversity when ecosystems experience ) B/ p# V! p& t. ?
disturbance. Grasslands were able to recover from burning only in areas that had
+ s" M5 K3 U+ na relatively high diversity of native plants. This work demonstrates how
( q# c2 c- G- rpersistent human activity can homogenize both structure and function of an
& s4 x. n! f9 Necological system, while weakening the diversity-related mechanisms needed to
" ^! n4 S" ?) |5 scompensate for sudden disturbance. There are many terrestrial systems today that 0 z2 A7 l8 Y1 Q% S) I
have become homogenized by persistent human activity that may be similarly 8 o2 \/ J: S* G1 T* l n e- C# B3 _
vulnerable to sudden environmental change that will be only evident after the
% U" s* W9 u- scollapse occurs. On the cover 'grass fire' (Dariush ) n5 s% V7 E j4 W2 s/ K. | E
M/Shutterstock).
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