Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Nishiku, Fukuoka, Japan.
Research Institute for Sustainable Humanosphere, Uji, Kyoto, Japan.
PLoS One. 2022 Mar 24;17(3):e0266131. doi: 10.1371/journal.pone.0266131. eCollection 2022.
Exudation by fine roots generally varies with their morphological traits, but the effect of belowground resource availability on the root exudation via root morphological traits and biomass remains unknown. We aimed to determine the effects of morphological and physiological traits on root exudation rates and to estimate stand-scale exudation (Estand) by measuring the mass, length, and surface area of fine roots in a Moso bamboo forest. We measured root exudation as well as morphological and physiological traits in upper and lower plots on a slope with different belowground resource availability. The mean (± S.D.) root exudation rates per mass in the upper and lower slope were 0.049 ± 0.047 and 0.040 ± 0.059 mg C g-1 h-1, respectively, which were in the range of exudation found in woody forest ecosystems. We observed significant relationships between root exudation per mass and root respiration, as well as specific root length and surface area. In contrast, exudation per length and area did not correlate with morphological traits. The morphological traits did not differ between slope positions, resulting in no significant difference in root exudation per mass. Fine root biomass, length, and surface area on a unit ground basis were much higher in the lower than those in the upper slope positions. Estand was higher when estimated by mass than by length and area because the morphological effect on exudation was ignored when scaled using mass. Estand was 1.4-2.0-fold higher in the lower than that in upper slope positions, suggesting that the scaling parameters of mass, length, and area determined the Estand estimate more than the exudation rate per mass, length, and area. Regardless of scaling, Estand was much higher in the Moso bamboo forest than in other forest ecosystems because of a large fine-root biomass.
细根的渗出通常随其形态特征而变化，但地下资源可用性对通过根形态特征和生物量的根渗出的影响尚不清楚。我们旨在通过测量毛竹林中细根的质量、长度和表面积来确定形态和生理特征对根渗出率的影响，并估计林分尺度的渗出（Estand）。我们在地下资源可用性不同的斜坡上下地段测量了根渗出以及形态和生理特征。上、下坡段的根渗出率分别为 0.049±0.047 和 0.040±0.059mg C g-1 h-1，处于木质林生态系统中发现的渗出范围之内。我们观察到根渗出与根呼吸之间，以及比根长和比根表面积之间存在显著的关系。相比之下，单位长度和面积的根渗出与形态特征之间没有相关性。形态特征在坡位之间没有差异，因此单位质量的根渗出没有差异。单位地面上的细根生物量、长度和表面积在下部明显高于上部。由于在按质量进行缩放时忽略了形态对渗出的影响，因此按质量估计的 Estand 高于按长度和面积估计的 Estand。下部的 Estand 比上部高 1.4-2.0 倍，这表明质量、长度和面积的缩放参数比单位质量、长度和面积的渗出率更能确定 Estand 的估计值。无论采用哪种方法，由于细根生物量较大，毛竹林的 Estand 都远高于其他森林生态系统。
