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首页> 美国卫生研究院文献>Frontiers in Plant Science >Seasonal Patterns of Fine Root Production and Turnover in a Mature Rubber Tree (Hevea brasiliensis Müll. Arg.) Stand- Differentiation with Soil Depth and Implications for Soil Carbon Stocks
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Seasonal Patterns of Fine Root Production and Turnover in a Mature Rubber Tree (Hevea brasiliensis Müll. Arg.) Stand- Differentiation with Soil Depth and Implications for Soil Carbon Stocks

机译：一棵成熟橡胶树（巴西橡胶树）的细根产生和周转的季节性模式与土壤深度的分异及其对土壤碳储量的影响

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Fine root dynamics is a main driver of soil carbon stocks, particularly in tropical forests, yet major uncertainties still surround estimates of fine root production and turnover. This lack of knowledge is largely due to the fact that studying root dynamics in situ, particularly deep in the soil, remains highly challenging. We explored the interactions between fine root dynamics, soil depth, and rainfall in mature rubber trees (Hevea brasiliensis Müll. Arg.) exposed to sub-optimal edaphic and climatic conditions. A root observation access well was installed in northern Thailand to monitor root dynamics along a 4.5 m deep soil profile. Image-based measurements of root elongation and lifespan of individual roots were carried out at monthly intervals over 3 years. Soil depth was found to have a significant effect on root turnover. Surprisingly, root turnover increased with soil depth and root half-life was 16, 6–8, and only 4 months at 0.5, 1.0, 2.5, and 3.0 m deep, respectively (with the exception of roots at 4.5 m which had a half-life similar to that found between depths of 1.0 and 2.5 m). Within the first two meters of the soil profile, the highest rates of root emergence occurred about 3 months after the onset of the rainy season, while deeper in the soil, root emergence was not linked to the rainfall pattern. Root emergence was limited during leaf flushing (between March and May), particularly within the first two meters of the profile. Between soil depths of 0.5 and 2.0 m, root mortality appeared independent of variations in root emergence, but below 2.0 m, peaks in root emergence and death were synchronized. Shallow parts of the root system were more responsive to rainfall than their deeper counterparts. Increased root emergence in deep soil toward the onset of the dry season could correspond to a drought acclimation mechanism, with the relative importance of deep water capture increasing once rainfall ceased. The considerable soil depth regularly explored by fine roots, even though significantly less than in surface layers in terms of root length density and biomass, will impact strongly the evaluation of soil carbon stocks.
机译：细根动态是土壤碳储量的主要驱动力，尤其是在热带森林中，但是主要不确定性仍然围绕着细根生产和周转的估计。缺乏知识的主要原因在于，就地研究根系动力学（尤其是在土壤深处）仍然充满挑战。我们探索了处于次优气候和气候条件下的成熟橡胶树（巴西橡胶树）的细根动力学，土壤深度和降雨之间的相互作用。在泰国北部安装了根系观察通道，以监测沿4.5 m深土壤剖面的根系动态。在3年内每月进行一次基于图像的根部伸长率和根部寿命测量。发现土壤深度对根的周转有显着影响。出人意料的是，根部周转随土壤深度增加而增加，根部半衰期分别为0.5、1.0、2.5和3.0 m处分别为16个月，6–8和4个月（4.5m处的根只有一半）寿命类似于在1.0至2.5 m的深度之间发现的寿命）。在土壤剖面的前两米内，根系出苗率最高，发生在雨季开始后约三个月，而在土壤深处，根系出苗与降雨模式无关。在冲洗期间（3月至5月之间），尤其是在剖面的前两米之内，根的出现受到限制。在0.5至2.0 m的土壤深度之间，根系死亡率似乎与根系出苗的变化无关，但在2.0 m以下，根系出苗和死亡的峰值同步。根部系统的浅部分比深部的对降雨的响应更大。在干旱季节开始时，深层土壤中根系出苗增加可能与干旱适应机制相对应，一旦降雨停止，深水捕获的相对重要性就会增加。尽管就根长密度和生物量而言明显小于表层，但细根定期探索的相当大的土壤深度将极大地影响土壤碳储量的评估。

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