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首页> 美国卫生研究院文献>Annals of Botany >Root biomass turnover and net primary productivity of a coffee agroforestry system in Costa Rica: effects of soil depth shade trees distance to row and coffee age
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Root biomass turnover and net primary productivity of a coffee agroforestry system in Costa Rica: effects of soil depth shade trees distance to row and coffee age

机译：哥斯达黎加咖啡农林业系统的根生物量周转量和净初级生产力：土壤深度遮荫树行距和咖啡龄的影响

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>Background and Aims In Costa Rica, coffee (Coffea arabica) plants are often grown in agroforests. However, it is not known if shade-inducing trees reduce coffee plant biomass through root competition, and hence alter overall net primary productivity (NPP). We estimated biomass and NPP at the stand level, taking into account deep roots and the position of plants with regard to trees.>Methods Stem growth and root biomass, turnover and decomposition were measured in mixed coffee/tree (Erythrina poeppigiana) plantations. Growth ring width and number at the stem base were estimated along with stem basal area on a range of plant sizes. Root biomass and fine root density were measured in trenches to a depth of 4 m. To take into account the below-ground heterogeneity of the agroforestry system, fine root turnover was measured by sequential soil coring (to a depth of 30 cm) over 1 year and at different locations (in full sun or under trees and in rows/inter-rows). Allometric relationships were used to calculate NPP of perennial components, which was then scaled up to the stand level. >Key Results Annual ring width at the stem base increased up to 2·5 mm yr−1 with plant age (over a 44-year period). Nearly all (92 %) coffee root biomass was located in the top 1·5 m, and only 8 % from 1·5 m to a depth of 4 m. Perennial woody root biomass was 16 t ha−1 and NPP of perennial roots was 1·3 t ha−1 yr−1. Fine root biomass (0–30 cm) was two-fold higher in the row compared with between rows. Fine root biomass was 2·29 t ha−1 (12 % of total root biomass) and NPP of fine roots was 2·96 t ha−1 yr−1 (69 % of total root NPP). Fine root turnover was 1·3 yr−1 and lifespan was 0·8 years.>Conclusions Coffee root systems comprised 49 % of the total plant biomass; such a high ratio is possibly a consequence of shoot pruning. There was no significant effect of trees on coffee fine root biomass, suggesting that coffee root systems are very competitive in the topsoil.
机译：>背景和目标在哥斯达黎加，咖啡（阿拉伯咖啡）植物通常种植在农林中。但是，尚不清楚诱导阴凉的树木是否通过根竞争减少咖啡植物的生物量，从而改变了总体净初级生产力（NPP）。我们考虑了根深处和植物在树木上的位置，估算了林分水平上的生物量和NPP。>方法在混合咖啡/树木中测量茎生长和根生物量，周转和分解（ Erythrina poeppigiana）人工林。估算了一系列植物大小上茎环的年轮宽度和数量以及茎基面积。在沟中测量深度为4 m的根生物量和细根密度。考虑到农林业系统地下的异质性，通过在一年中和在不同位置（在阳光充足或树木下以及行/行间）对土壤进行连续取芯（深度为30厘米）来测量细根周转-行）。异形关系用于计算多年生植物的NPP，然后将其按比例放大至展位水平。 >主要结果：随着株龄的增加（44年以上），茎基的年轮宽度增加到2·5 mm yr -1 。几乎所有咖啡根生物量（92％）都位于顶部1·5m，从1·5m到4m的深度只有8％。多年生木本根生物量为16 t ha -1 ，多年生根的NPP为1·3 t ha -1 yr -1 。与行之间相比，行中的细根生物量（0–30µcm）高出两倍。细根生物量为2·29 t ha -1 （占根总生物量的12％），细根NPP为2·96 t ha -1 yr -1 （占总根NPP的69％）。细根周转时间为1·3 yr −1 ，寿命为0·8年。>结论咖啡根系统占植物生物量的49％；如此高的比例可能是芽修剪的结果。树木对咖啡细根生物量没有显着影响，表明咖啡根系在表层土壤中竞争非常激烈。

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