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An improved method for quantifying total fine root decomposition in plantation forests combining measurements of soil coring and minirhizotrons with a mass balance model.
Tree Physiology ( IF 4 ) Pub Date : 2020-06-05 , DOI: 10.1093/treephys/tpaa074 Xuefeng Li 1, 2 , Kevan J Minick 1 , Tonghua Li 1 , James C Williamson 1 , Michael Gavazzi 3 , Steven McNulty 3 , John S King 1
中文翻译:
一种用于量化人工林中总细根分解的改进方法,该方法结合了土壤取心和微型根茎的测量与质量平衡模型。
更新日期:2020-10-27
Tree Physiology ( IF 4 ) Pub Date : 2020-06-05 , DOI: 10.1093/treephys/tpaa074 Xuefeng Li 1, 2 , Kevan J Minick 1 , Tonghua Li 1 , James C Williamson 1 , Michael Gavazzi 3 , Steven McNulty 3 , John S King 1
Affiliation
Abstract
Accurate measurement of total fine root decomposition (the amount of dead fine roots decomposed per unit soil volume) is essential for constructing a soil carbon budget. However, the ingrowth/soil core-based models are dependent on the assumptions that fine roots in litterbags/intact cores have the same relative decomposition rate as those in intact soils and that fine root growth and death rates remain constant over time, while minirhizotrons cannot quantify the total fine root decomposition. To improve the accuracy of estimates for total fine root decomposition, we propose a new method (balanced hybrid) with two models that integrate measurements of soil coring and minirhizotrons into a mass balance model. Model input parameters were fine root biomass, necromass and turnover rate for Model 1, and fine root biomass, necromass and death rate for Model 2. We tested the balanced hybrid method in a loblolly pine plantation forest in coastal North Carolina, USA. The total decomposition rate of absorptive fine roots (ARs) (a combination of first- and second-order fine roots) using Models 1 and 2 was 107 ± 13 g m−2 year−1 and 129 ± 12 g m−2 year−1, respectively. Monthly total AR decomposition was highest from August to November, which corresponded with the highest monthly total ARs mortality. The ARs imaged by minirhizotrons well represent those growing in intact soils, evident by a significant and positive relationship between the standing biomass and the standing length. The total decomposition estimate in both models was sensitive to changes in fine root biomass, turnover rate and death rate but not to change in necromass. Compared with Model 2, Model 1 can avoid the technical difficulty of deciding dead time of individual fine roots but requires greater time and effort to accurately measure fine root biomass dynamics. The balanced hybrid method is an improved technique for measuring total fine root decomposition in plantation forests in which the estimates are based on empirical data from soil coring and minirhizotrons, moving beyond assumptions of traditional approaches.
中文翻译:
一种用于量化人工林中总细根分解的改进方法,该方法结合了土壤取心和微型根茎的测量与质量平衡模型。
摘要
准确测量总细根分解量(每单位土壤体积分解的死细根的数量)对于构建土壤碳收支至关重要。但是,基于向内生长/土壤核心的模型取决于以下假设:小袋/完整核心中的细根具有与完整土壤中的细根相同的相对分解速率,细根的生长和死亡率随时间保持恒定,而小型根尖虫不能量化总细根分解。为了提高估计的总细根分解的准确性,我们提出了一种新的方法(平衡混合),该方法具有两个模型,这些模型将土壤取心和小型根茎的测量结果整合到质量平衡模型中。模型输入参数为模型1的细根生物量,坏死和周转率,以及细根生物量,模型2的坏死和死亡率。我们在美国北卡罗来纳州沿海的火炬松人工林中测试了平衡杂交方法。使用模型1和2的吸收性细根(ARs)(一阶和二阶细根的组合)的总分解率为107±13 g m−2 年−1和129±12 g m − 2 年−1, 分别。从8月到11月,每月总AR分解最高,这与AR总每月死亡率最高相对应。小型根部回旋管成像的AR很好地代表了在完整土壤中生长的AR,这一点可以通过站立生物量和站立长度之间的显着正相关来证明。在两个模型中,总分解估计值对细根生物量,周转率和死亡率的变化敏感,但对坏死的变化不敏感。与模型2相比,模型1可以避免确定单个细根死区时间的技术难题,但需要更多的时间和精力来精确测量细根生物量动态。