Depth Distributions of Belowground Production, Biomass and Decomposition in Restored Tallgrass Prairie

Adam C.VON HADEN; Mathew E.DORNBUSH

摘要

Grasslands store large stocks of soil organic carbon (SOC) in the subsoil,but our knowledge of belowground processes becomes less robust with depth.Vertically explicit SOC models typically assume that the depth distribution of belowground production follows the depth distribution of belowground biomass,but this assumption has not been tested.In addition to the effects of soil temperature and moisture on decomposition,some vertically explicit SOC models implement an intrinsic decrease in belowground decomposition with depth,yet this effect has rarely been observed empirically.We simultaneously measured the depth distributions of belowground biomass,production,and litter decomposition to assess whether belowground biomass depth distributions were suitable predictors of belowground production and whether belowground decomposition decreased with soil profile depth.We found that live and total (live + dead) belowground biomass was distributed relatively more shallowly than total belowground production,and thus total belowground biomass was a biased predictor of the vertical distribution of belowground production.The depth distribution of live roots ＜ 2 mm in diameter was found to be the best predictor of total belowground production depth distribution.Using an intact decay core method,we found that belowground litter decomposition decreased by 49％ from 0-10 to 30-40 cm depth,and model-simulated effects of soil temperature and moisture accounted for only 9％ of the observed decrease with depth.Vertically explicit SOC models can be improved with more accurate empirical belowground production depth distribution estimates,but depth-specific decomposition rates currently implemented in SOC models are necessary to explain observed decreases in belowground litter decay with depth.

机译：草原在地下土壤中储存了大量的土壤有机碳（SOC），但是我们对地下过程的了解随着深度的增加而减弱。垂直显式SOC模型通常假定地下生产的深度分布遵循地下生物量的深度分布，但这除了土壤温度和水分对分解的影响外，一些垂直显式SOC模型还实现了地下分解随深度的内在减小，但这种现象很少凭经验观察到。地下生物量，产量和凋落物分解，以评估地下生物量深度分布是否适合预测地下产量，以及地下分解量是否随土壤剖面深度而降低。总地下地下总生物量是地下产量垂直分布的有偏预测指标。直径小于2 mm的活根深度分布是地下总产量深度分布的最佳预测指标。采用完整的衰变核方法，我们发现地下凋落物分解从0-10 cm深度减少了49％，而土壤温度和水分的模拟影响仅占观察到的深度随深度减少的9％。垂直显式SOC模型可以可以通过更准确的经验性地下开采深度分布估计值进行改进，但目前在SOC模型中实现的特定于深度的分解率对于解释地下随深度衰减的凋落物的减少是必要的。

Depth Distributions of Belowground Production, Biomass and Decomposition in Restored Tallgrass Prairie

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