Root respiration (R_r) plays a crucial role in the global carbon balance, because R_r accounts for about a half of soil respiration in typical forest ecosystems. Plant roots are different in metabolism and functions according to size. Fine roots, which are typically defined as roots < 2 mm in diameter, perform important ecosystem functions and consequently govern belowground carbon cycles mainly because of their high turnover rates. However, the phenological variation of fine root functions is not well understood yet. To quantitatively examine the fine root functions, we adopted an approach to partition R_r into growth respiration (R_g) and maintenance respiration (R_m) using a modified traditional model, in which R_g was proportional to root production, and R_m was proportional to root biomass and exponentially related to soil temperature. We conducted a field experiment on soil respiration and fine root biomass and production over a year in a larch‑dominated young forest developing on the bare ground after removing surface organic soil to parameterize the model. The model was significantly parameterized using the field data measured in such simplified field conditions, because we could control spatial variation in heterotrophic respiration and contamination from roots other than fine roots. The annual R_r of all roots was 94 g C m^‑2 yr^‑1 and accounted for 25% of total soil respiration on average. The annual R_r was partitioned into fine root R_g, fine root R_m and coarse root R_m by 30, 44 and 26%, respectively; coarse root R_g was presumed to be negligible. Fine root R_g and R_m varied according to the seasonal variations of fine root production and soil temperature, respectively; the contribution of fine root biomass was minor because of its small seasonality. The contribution of R_g to total fine root respiration was lower in the cold season with low production.

中文翻译：

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落叶松幼林细根生物量、产量和呼吸作用的变化

根呼吸（R _r）在全球碳平衡中起着至关重要的作用，因为在典型的森林生态系统中，R _r约占土壤呼吸的一半。植物根系根据大小的不同，其代谢和功能也不同。细根通常定义为直径小于 2 毫米的根，执行重要的生态系统功能并因此控制地下碳循环，主要是因为它们的周转率高。然而，细根功能的物候变化尚不清楚。为了定量检查细根函数，我们采用了一种方法将R _r划分为生长呼吸（R _g）和维持呼吸（R_m ) 使用改进的传统模型，其中R _g与根生产成正比，R _m与根生物量成正比，并与土壤温度呈指数相关。我们在去除表层有机土壤后在裸地生长的落叶松占主导地位的幼林中对土壤呼吸和细根生物量和产量进行了一年多的田间试验，以参数化模型。该模型使用在这种简化的田间条件下测量的田间数据进行了显着参数化，因为我们可以控制异养呼吸的空间变化和来自细根以外的根的污染。所有根的年R _r为 94 g C m ^‑2 yr^‑1平均占土壤总呼吸的 25%。一年生R _r分别按30%、44%和26%划分为细根R _g、细根R _m和粗根R _m；粗根R _g被认为可以忽略不计。细根R _g和R _{m 分别}随细根产量和土壤温度的季节变化而变化；细根生物量的贡献很小，因为它的季节性很小。R _g的贡献 在低产的寒冷季节，细根呼吸总量较低。