4月5日的爱思唯尔期刊《森林生态与管理》（Forest Ecology and Management）刊登了美国科学家的一项最新研究，他们发现一种可以使夏威夷相思木生长更快的方法。大面积的夏威夷相思木林在提供美丽的自然景观的同时，还对水土保持、维护生物多样性及通过碳的储存和多价螯合减缓气候变化等起着积极的作用。
夏威夷相思木即夏威夷洋槐，是一种非常珍贵的木材，一直被用来制作高档的家具和乐器。随着农业占地的扩张和大面积的砍伐，其覆盖率越来越低。早在2002年，科学家就开始对夏威夷相思木进行研究，他们对于肥料以及疏伐（间伐）对相思木的影响做了系统的研究，疏伐是为了缓和树木间的生存竞争和促进其生长而采取砍伐一部分树木的措施。
经过多年的试验，研究人员找到了一种新的适合夏威夷相思木的培育方法。结果显示，用新培育方法的试验林生长很快，树木的直径每年增加1.2倍。此外，他们还发现采用该方法并不对周围草木以及植被长生不利的影响，同时研究表明采取新培育措施对于鸟类栖息也没有负面影响。
研究人员认为对夏威夷相思木幼苗采用新的培育措施不仅可以增加了树木的成活率，增加其生长速度，同时还兼顾维持了本土健康而完整的生态环境。（科学网 于乃森/编译）
生物谷推荐原始出处：
（Forest Ecology and Management），doi:10.1016/j.foreco.2007.11.019，Paul G. Scowcroft, Janis E. Haraguchi and David M. Fujii
Understory structure in a 23-year-old Acacia koa forest and 2-year growth responses to silvicultural treatments
Paul G. Scowcroft, a, , Janis E. Haraguchia and David M. Fujiia
Abstract
Restoration of degraded Acacia koa forests in Hawaii often involves mechanical scarification to stimulate germination of seed buried in the soil and to suppress vegetation that competes with shade intolerant A. koa. Resulting even-age stands are gradually colonized by other plant species, but understory structure is poorly quantified, and the effects of management on understory vegetation are unknown. We examined the structure of the dominant understory species 23 years after stand initiation and determined their subsequent 2-year growth responses to silvicultural treatments prescribed to improve growth of koa. Release thinning, chemical control of introduced grasses, and phosphorus fertilization were applied in a split-plot experimental design. Results for DBH and height class distributions indicated that recruitment for most tree species began within a few years of stand initiation. By 23 years understory trees made up only 14% of total stand basal area, but they added greatly to native plant biodiversity. Alien grasses covered 92% of the forest floor and averaged 1.35 Mg ha−1. Of the four most abundant native understory tree species, only shade intolerant Myoporum sandwicense grew faster in response to the treatments. P-fertilizer combined with grass control significantly increased production of the native shrub, Rubus hawaiiensis. Notably, alien grass biomass did not increase in response to thinning, and actually declined in P-fertilized plots. Only, where P-fertilizer was applied were P concentrations of understory leaves elevated. Foliar concentrations of other nutrients were generally unaffected by treatments. Our findings suggest that the conservative silvicultural treatments we used can be applied without adversely impacting the capacity of aggrading A. koa forests to support a diversity of native understory plants. Lack of an increase in alien grass biomass, and in the case of P fertilization, a reduction in grass biomass, indicates that treatments should not increase competition with native species.
