本帖最后由 细胞海洋 于 2013-2-8 21:28 编辑 U$ F0 \ }) |6 c1 p+ @' v# _) a, `+ B$ [' w2 v# n5 H 0 x- V2 {! w/ {+ L About the " Q/ t. \9 }% b: HCover1 M/ A, j7 i( ~: }0 i( q) U: `
Stretches of oak savanna & h; i, g5 d1 F( c* Jin the Pacific Northwest of North America have been subject to fire-prevention 7 Z+ X8 u5 L# Q7 b) P( fmeasures since the mid-nineteenth century. The resulting grassland has lost ) v3 Z3 ?# G& w# |1 |
plant species but achieves stable high-yield annual production — rather like a 1 r F0 P# h8 ^6 I$ V4 uhigh-yield agricultural system — and remains resilient to invasive species and # b' C1 J: G4 f+ S' Q* G- l; W/ M4 G7 [3 o
climate fluctuation. A long-term study in which 7 K* i2 R) f3 @' b: Sselected grassland plots were periodically burned and allowed to recover now ! k7 ?: ~5 j# u! }5 ^demonstrates the critical value of biodiversity when ecosystems experience 0 K( T0 ~) s3 g9 T2 D4 c0 p
disturbance. Grasslands were able to recover from burning only in areas that had ( Y0 {: m, s0 u, b# @0 a
a relatively high diversity of native plants. This work demonstrates how ) s% a; }4 \' N, Q3 |
persistent human activity can homogenize both structure and function of an ! I9 L( W% I6 d, m/ g) b5 f, fecological system, while weakening the diversity-related mechanisms needed to 7 }' C: v, Z* B' u- ^% T
compensate for sudden disturbance. There are many terrestrial systems today that # Y$ R# S9 u3 j# C6 k5 j! h z
have become homogenized by persistent human activity that may be similarly 7 K6 Q. q( ~, m
vulnerable to sudden environmental change that will be only evident after the 5 M- s& Y- w: Y' Acollapse occurs. On the cover 'grass fire' (Dariush - R& v2 a6 M) o+ J. h2 BM/Shutterstock). # X* P8 M' B& X' I) n 6 Q4 P( ?( J' P7 l- K* C8 V- x6 a/ m, H) l: r7 V; }
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3 x2 Y2 D2 y' \( r) { 作者: exin11 时间: 2013-2-15 22:45
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