|
- 积分
- 17983
- 威望
- 17983
- 包包
- 26159
|
本帖最后由 细胞海洋 于 2013-2-8 21:28 编辑 6 w/ W7 ]2 R9 x9 Z- x
" @7 L3 u( K( J5 k
# ~; \; j( l, JAbout the 6 u; C) W. o4 K* D [
Cover7 B. A0 a. R6 W+ c, W
Stretches of oak savanna 5 S4 J2 \0 n i3 k0 G$ o
in the Pacific Northwest of North America have been subject to fire-prevention 5 p- e- |- S9 c4 k
measures since the mid-nineteenth century. The resulting grassland has lost
) G$ ?0 M% \! d9 @- G4 M$ b3 Mplant species but achieves stable high-yield annual production — rather like a
0 J( F) r$ |5 i1 {) Dhigh-yield agricultural system — and remains resilient to invasive species and $ S$ |. d2 U% E! F E4 Z
climate fluctuation. A long-term study in which
, z9 t7 g4 C Y5 Z/ G* Gselected grassland plots were periodically burned and allowed to recover now 1 F6 s* p3 F! y- B7 U
demonstrates the critical value of biodiversity when ecosystems experience + l7 O4 J: B) y5 E2 _7 ~5 L
disturbance. Grasslands were able to recover from burning only in areas that had
0 Y# N! [/ t7 Ka relatively high diversity of native plants. This work demonstrates how " C- f) m6 R; q8 ~, j: N' z( Y
persistent human activity can homogenize both structure and function of an
; F! ]3 H/ W$ r/ [% [2 Uecological system, while weakening the diversity-related mechanisms needed to
. V) d. u: f9 Q6 x. u" I" x: f. Wcompensate for sudden disturbance. There are many terrestrial systems today that / @0 T* \) k# M
have become homogenized by persistent human activity that may be similarly - P& W0 t3 L0 M9 v: o: s7 m
vulnerable to sudden environmental change that will be only evident after the
. ?6 q% M! S+ \; f. M% R6 B Ucollapse occurs. On the cover 'grass fire' (Dariush
- F6 t! J t7 a) A& X" E% xM/Shutterstock).- Z. Y9 V. x) p/ q
% W, P- G5 _' `* h- f; h. L2 A* l9 ^' ~% a; z3 }
, g# ^( _6 I: G4 i% O$ W2 ?) g5 z b/ c7 g
|
附件: 你需要登录才可以下载或查看附件。没有帐号？注册
-
总评分: 威望 + 20
包包 + 20
查看全部评分
|
发表于 2013-2-8 19:38
发表于 2013-2-15 22:45
