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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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7 c3 [, h6 e( \$ g2 o: \About the / E! I& }' p: f0 e- K o
Cover
' A* V' v$ t; OStretches of oak savanna
/ R8 Z, l# I, N2 b# E" n" ?1 m+ Q( Nin the Pacific Northwest of North America have been subject to fire-prevention
* H: @& P2 s; `+ t# Rmeasures since the mid-nineteenth century. The resulting grassland has lost
( Q( @6 Q7 _& B0 M: A: ^/ y# j; Pplant species but achieves stable high-yield annual production — rather like a
& _- U# @# F8 |4 V, c" ]high-yield agricultural system — and remains resilient to invasive species and
a6 S+ J5 c4 i/ O3 t) w+ {2 b; p; Bclimate fluctuation. A long-term study in which 9 E! |4 m8 l7 ^8 `( S) f
selected grassland plots were periodically burned and allowed to recover now
8 a/ K. A1 h0 ^6 ]3 odemonstrates the critical value of biodiversity when ecosystems experience u9 `/ p6 k2 p( _& q! G
disturbance. Grasslands were able to recover from burning only in areas that had
( j9 f# X- F% sa relatively high diversity of native plants. This work demonstrates how
# {- \) p" N- `2 b. |' y, spersistent human activity can homogenize both structure and function of an
' D- G- ^$ w. w$ p# t0 [ecological system, while weakening the diversity-related mechanisms needed to / c) [6 e& z8 Q0 |
compensate for sudden disturbance. There are many terrestrial systems today that
. t* V# n4 a. U7 shave become homogenized by persistent human activity that may be similarly
6 |* j; i h2 ~2 p' d) }7 Xvulnerable to sudden environmental change that will be only evident after the
" l6 a3 D$ n y5 T, D: ~, N. b0 xcollapse occurs. On the cover 'grass fire' (Dariush & ^! S% G8 d$ @# h
M/Shutterstock).
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