Determining deep root water uptake patterns with tree age in the Chinese loess area
Determining deep root water uptake patterns with tree age in the Chinese loess area
复制标题
确定中国黄土地区根深部吸水模式随树龄的变化
DOI：
10.1016/j.agwat.2021.106810
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发表时间：
2021
影响因子：
6.7
通讯作者：
Si Bingcheng
中科院分区：
文献类型：
--
作者：
Tao Ze;Neil Eric;Si Bingcheng
深层土壤水分对树木抗旱十分重要，因此也是评估植树造林可持续性的一个重要考虑因素。然而，树木在多大程度上依赖深层土壤进行根系吸水（RWU）仍然知之甚少。在黄土高原选择了2008、2005、2001、1998和1994年种植的5个苹果园（分别命名为A2008、A2005、A2001、A1998和A1994），测定了23 m深处树木木质部和土壤的水同位素。然后，我们使用具有双同位素（2 H，18 O）的贝叶斯混合模型MixSIAR来量化每个土层（0-0.4 m，0.4-2 m，2-5 m和5 m到最大生根深度）在正常年份2017年，2018年和湿润年份2019年对RWU的季节贡献率。结果表明，随着果园龄的增加，根深由10.2 m增加到23.2 m，导致深层（5 m以下）累积水分亏缺量由9年果园的74.5 mm增加到25年果园的1191.8 mm。5 m以下的深层土壤水分对整个果园RWU的贡献率为9-39%。尽管老果园A1998和A1994中0-2 m土壤中的细根仅占整个剖面中细根的20%，但这些根在2017-2019年平均占总吸收水量的64%。相对于正常年份，丰水年苹果树对深层土壤水分的依赖程度较低。研究结果对黄土高原生态恢复具有重要意义。
Deep soil water is important for trees to combat droughts and thus is an important consideration for assessing sustainability of afforestation. However, the extent to which trees could depend on deep soil for root water uptake (RWU), remains poorly understood. Here we selected five apple orchards, planted in 2008, 2005, 2001, 1998 and 1994 (named A2008, A2005, A2001, A1998, and A1994, respectively) from the Chinese Loess Plateau and measured water isotopes from tree xylem and soil to the depth up to 23 m. We then used the Bayesian mixing model MixSIAR with dual isotopes (2H,18O) to quantify the seasonal contribution ratio of each soil layer (0–0.4 m, 0.4–2 m, 2–5 m, and 5 m to maximum rooting depth) to RWU in normal years 2017, 2018 and wet year 2019. Results showed that with increasing orchard age, rooting depth increased from 10.2 m to 23.2 m, resulting in cumulative deep soil (below 5 m) water deficits from 74.5 mm in 9-year-old orchard to 1191.8 mm in 25-year-old orchard. And annual deep soil water below 5 m contributed 9–39% to the total RWU over the orchard lifetime. Although fine roots in shallow 0–2 m soils in old orchards A1998 and A1994 only accounted for 20% of that in the entire profiles, these roots contributed, on average, 64% of the total absorbed water in 2017–2019. Relative to the normal year, apple trees relied less on deep soil water in wet year. Our findings is of particular significance to the ongoing eco-restoration on the Chinese Loess Plateau (CLP).