Murray K J, Tenhunen J D, Kummerow J
Systems Ecology Research Group, San Diego State University, 92182, San Diego, CA, USA.
Biology Department, San Diego State University, 92182, San Diego, CA, USA.
Oecologia. 1989 Aug;80(2):256-262. doi: 10.1007/BF00380160.
In the foothills of the Philip Smith Mountains, Brooks Range, Alaska, tussock tundra occurs on rolling hills and in valleys that were shaped by Pleistocene glaciations. During the 1986 and 1987 summer seasons, Sphagnum growth and production were determined in "water tracks" on tundra slopes that acted to channel water flow to the valley bottom stream and in "intertrack tundra" areas that were relatively homogeneous with respect to downslope drainage. Measurements were made under ambient environmental conditions and on mosses receiving supplemental irrigation in each area. Growth rate for Sphagnum spp. (cm shoot length increase/day) was low and relatively constant in intertrack tundra and highest but quite variable in water tracks. A strong negative correlation was found between Sphagnum spp. growth rate and solar irradiance in the shady environment below Salix canopies in the water tracks. Estimates of net annual dry weight (DW) production for Sphagnum spp. ranged from 0.10 g DW dm yr in intertrack tundra vegetation to 1.64 g DW dm yr in well-shaded water tracks. Experimental water additions had little effect on growth and production in intertrack tundra and well-developed water tracks, but significantly increased growth in a weakly-developed water track community. Low production over large areas of tundra slopes may occur due to presence of slow growing species resistant to dessication in intertrack tundra as opposed to rapidly growing less compact species within the limited extent of water tracks. We hypothesize that species capable of rapid growth occur also in weakly-developed water tracks, and that these are water-limited more often than plants occurring in well-developed water track situations. Where experienced, high light intensity may additionally limit growth due to photoinhibition.
在阿拉斯加布鲁克斯山脉菲利普·史密斯山的山麓地带，起伏的山丘以及由更新世冰川作用形成的山谷中生长着丘状苔原。在1986年和1987年的夏季，对苔原斜坡上引导水流至谷底溪流的“水道”以及下坡排水相对均匀的“水道间苔原”区域的泥炭藓生长和产量进行了测定。测量是在自然环境条件下以及每个区域接受补充灌溉的苔藓上进行的。泥炭藓属植物的生长速率（茎长度增加厘米/天）在水道间苔原较低且相对恒定，在水道中最高但变化很大。在水道中柳树树冠下的阴凉环境中，泥炭藓属植物的生长速率与太阳辐照度之间存在很强的负相关。泥炭藓属植物的年净干重（DW）产量估计值范围从水道间苔原植被中的0.10克DW/平方分米/年到光照良好的水道中的1.64克DW/平方分米/年。实验性加水对水道间苔原和发育良好的水道中的生长和产量影响不大，但显著增加了发育较弱的水道群落中的生长。苔原斜坡大面积区域产量较低可能是由于水道间苔原中存在抗干燥的生长缓慢物种，而不是水道有限范围内生长迅速、结构较疏松的物种。我们推测，能够快速生长的物种也出现在发育较弱的水道中，而且这些水道比发育良好的水道中的植物更常受到水分限制。在有光照的地方，高光强可能还会因光抑制而限制生长。
