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首页> 外文期刊>Agroforestry Systems >Tree-root systems and herbaceous species-characteristics under tree species introduced into grazing lands in subhumid Cameroon
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Tree-root systems and herbaceous species-characteristics under tree species introduced into grazing lands in subhumid Cameroon

机译：喀麦隆半湿润地区放牧地带树种下的树根系统和草本物种特征

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摘要

The effect of tree species on the characteristics of the herbaceous stratum, during the first five years of a fallow, was evaluated in the North of Cameroon (average annual temperature 28.2 °C, total annual rainfall 1050 mm). Treatments included a natural grazed herbaceous fallow, a natural ungrazed herbaceous fallow and three planted tree fallows (Acacia polyacantha Willd. ssp. campylacantha (Hochst. ex A. Rich.), Senna siamea Lam. and Eucalyptus camaldulensis Dehnh.), which were protected against grazing. Because tree species influenced light interception in different ways, as well as having different root patterns, they had different effects on the herbaceous stratum in terms of species composition and biomass. The grazed herbaceous fallow maintained the greatest species richness. Protection against grazing or the introduction of tree species associated with the absence of grazing induced both a progressive evolution to a particular species composition. The ungrazed herbaceous fallow consisted mainly of Andropogon gayanus Kunth, which provided the greatest biomass (8 t dry matter ha–1 at the end of the fallow period). E. camaldulensis provided little shade and the lowest fine root mass in the top layer allowing the growth of A. gayanus and thus a greater herbaceous biomass (3.5 t DM ha–1) than that found under the other tree species. Under the heavy shade of A. polyacantha, the herbaceous stratum consisted mainly of annual Pennisetum spp. (2.2 t DM ha–1) and showed the greatest N concentration (1.3%), probably due to N2 fixation by the tree species. After the fourth year, despite the relatively open tree canopy, S. siamea, which showed the highest fine root mass, had a strong depressive effect on the herbaceous stratum.
机译：在喀麦隆北部（平均年温度28.2°C，年总降雨量1050 mm）评估了休耕的前五年树木种类对草本地层特征的影响。处理方法包括天然放牧的草地休闲草，天然未磨牙的草地休闲草和三棵种植的树木休闲草（Acacia polyacantha Willd。ssp。campylacantha（Hochst。ex A. Rich。），Senna siamea Lam。和Eucalyptus camaldulensis Dehnh。）。反对放牧。由于树种以不同的方式影响光的截获，并且具有不同的根系，因此它们对草本层的物种组成和生物量具有不同的影响。放牧的草场休耕地保持了最大的物种丰富度。防止放牧或引入与没有放牧相关的树种，既可以逐步进化为特定的物种组成。未软化的休耕地主要由Andropogon gayanus Kunth组成，提供最大的生物量（休耕期末干物质为8 t干物质ha-1 ）。 E. camaldulensis几乎没有遮荫，顶层的细根质量最低，从而允许A. gayanus的生长，因此比其他树种具有更大的草本生物量（3.5 t DM ha-1 ）。在重叶草的浓荫下，草本层主要由一年生的狼尾草属组成。 （2.2 t DM ha–1 ）并显示出最大的N浓度（1.3％），这可能是由于树木对N2 的固定所致。第四年后，尽管树冠相对开放，但S. siamea表现出最高的细根质量，对草本层具有强烈的抑制作用。

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