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本帖最后由 细胞海洋 于 2013-2-8 21:28 编辑 8 Y/ E, ~' R# f! `' J8 T
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+ A0 s6 n/ U1 l5 y3 n* \About the
e* I: n: @6 C/ r, |$ KCover
% a7 Y4 [1 \7 T* l9 EStretches of oak savanna
& h3 Y) X+ U4 v) v6 ]% hin the Pacific Northwest of North America have been subject to fire-prevention 6 O& l5 d$ n! S$ K, z- p7 z. a+ ^4 `/ u
measures since the mid-nineteenth century. The resulting grassland has lost
, E ^* }/ `8 K+ M6 T6 dplant species but achieves stable high-yield annual production — rather like a
: {* M! c6 S B+ \/ ~! N2 r1 Yhigh-yield agricultural system — and remains resilient to invasive species and - f6 ]: t" A' s
climate fluctuation. A long-term study in which 0 O1 O6 z/ A d
selected grassland plots were periodically burned and allowed to recover now
& m: ]! G8 x+ z/ ademonstrates the critical value of biodiversity when ecosystems experience
2 D/ V" }: I0 ?) ?, `' c4 q/ L7 idisturbance. Grasslands were able to recover from burning only in areas that had
+ Y, I# k, v4 C+ m0 j' k$ wa relatively high diversity of native plants. This work demonstrates how + @* i+ d) a: Y4 E4 h% F
persistent human activity can homogenize both structure and function of an
9 H3 S9 U: X$ j0 B3 Y" Wecological system, while weakening the diversity-related mechanisms needed to
9 E. o; x( @8 B* u& J! lcompensate for sudden disturbance. There are many terrestrial systems today that + Y7 k, p. x5 R
have become homogenized by persistent human activity that may be similarly
9 L" q" B$ @9 S( X2 rvulnerable to sudden environmental change that will be only evident after the & ?5 r/ c$ o' a, L" n) [: f
collapse occurs. On the cover 'grass fire' (Dariush % l7 D4 u6 t- Y* \ {
M/Shutterstock).+ n# q" B" l% o: s
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发表于 2013-2-8 19:38
发表于 2013-2-15 22:45
