Tree mortality by self-thinning is an inevitable consequence of the long residence times of standing trees in unmanaged coniferous plantations. Stemflow (SF) is an important localized input of rainwater into the soil in forest ecosystems. However, little information is available on how tree mortality affects SF yields. We took weekly measurements from 16 trees in a 20 × 10 m plot containing 50 trees in a dense unmanaged Japanese cypress plantation from April to October 2017. These 16 trees were classified into two groups: standing-live SF trees (n = 11, tree height [H]: 13.4 ± 1.1 m, DBH: 18.5 ± 3.8 cm, crown projection area [CPA]: 5.4 ± 0.8 m², average ± standard deviation) and standing-dead SF trees (n = 5, H: 7.9 ± 1.4 m, DBH: 10.0 ± 1.9 cm, CPA: 0.0 ± 0.0 m²). Because the smaller standing-dead trees with no crown were all positioned under the canopy of standing-live trees, the mean tree-scale SF volume (SFV_tree) of standing-dead trees was approximately 10.3 times smaller than that of standing-live trees. The much smaller SFV_tree of standing-dead trees was also explained by the basal area (3.5-fold smaller) and the tree-scale SF funnelling ratio (FR_tree, 2.9-fold smaller). SFV_tree of standing-dead trees was so small that the ratio of stand-scale SF (SF_stand) to gross rainfall (GR) (SF_stand/GR) was similar regardless of whether standing-dead trees were excluded or included (21.4% vs. 21.6%) in SF_stand calculations, indicating that SF_stand/GR could be reliably estimated using only standing-live trees.

中文翻译：

---

树木死亡率对自疏针叶林茎流产量估算的影响

因自体间伐导致的树木死亡是未经管理的针叶林中立木长期滞留的必然结果。茎流 ( SF ) 是雨水向森林生态系统土壤中的重要局部输入。然而，关于树木死亡率如何影响SF产量的信息很少。从 2017 年 4 月到 10 月，我们每周对一个包含 50 棵树的 20 × 10 m 地块中的 16 棵树进行测量。这 16 棵树被分为两组：立生SF树（n  = 11，树高度 [ H ]: 13.4 ± 1.1 m, DBH : 18.5 ± 3.8 cm, 冠部投影面积 [ CPA ]: 5.4 ± 0.8 m ², 平均值 ± 标准偏差) 和立死SF树 ( n  = 5, H : 7.9 ± 1.4 m, DBH : 10.0 ± 1.9 cm, CPA : 0.0 ± 0.0 m ² )。由于较小的无冠立枯树均位于活树树冠下，因此立枯树的平均树尺度SF体积（SFV_树）比活树小约10.3倍。 . 立枯树的SFV_树小得多也可以用基面积（小 3.5 倍）和树尺度SF漏斗比（FR_{树）来解释}，小 2.9 倍）。立_枯树的SFV_树非常小，以至于无论是否排除或包括立枯树，林分规模SF ( SF_林分) 与总降雨量 ( GR ) ( SF_林分/ GR ) 的比率都相似 (21.4%)与 21.6%) 在SF_林分计算中，表明SF_林分/ GR可以可靠地估计仅使用站立的活树。