Long-term Research Station of Alpine Forest Ecosystems, Key Laboratory of Ecological Forestry Engineering, Institute of Ecology and Forestry, Sichuan Agricultural University, Chengdu, 611130, China.
Sci Rep. 2018 Jun 19;8(1):9373. doi: 10.1038/s41598-018-27675-9.
Canopy exchange is one of the most important processes involved in the internal transfer of elements in forest ecosystems. However, little information is available on how canopy exchange influences the input of base cations in subalpine forests. Therefore, the concentrations and fluxes of base cations in throughfall and stemflow were investigated from August 2015 to July 2016 (except for the frozen season) in a representative subalpine spruce plantation in the eastern Tibet Plateau. Our results showed that the mean concentrations of K, Ca, Na and Mg were higher in the stemflow than in the throughfall and precipitation. The total input fluxes of K, Ca, Na and Mg in the internal forest were lower than those in the non-forest. Moreover, the results from the canopy budget model indicated that the canopy exchange fluxes of K, Ca and Mg were higher than the dry deposition fluxes, and Ca and Mg were uptaken, whereas K was leached when precipitation passed through the canopy. Therefore, the results suggested that the input of base cations is mainly controlled by canopy exchange during precipitation in subalpine forest ecosystems, and the canopy could alter the sinks and sources of base cations from precipitation.
林冠交换是森林生态系统内部元素转移的最重要过程之一。然而，关于林冠交换如何影响亚高山森林中碱基阳离子输入的信息却很少。因此，我们于 2015 年 8 月至 2016 年 7 月（除冰冻季节外）调查了青藏高原东部一个典型的亚高山云杉人工林的穿透雨和茎流中的碱基阳离子浓度和通量。结果表明，K、Ca、Na 和 Mg 的平均浓度在茎流中高于穿透雨和降水。内部森林的 K、Ca、Na 和 Mg 的总输入通量低于非森林。此外，林冠预算模型的结果表明，K、Ca 和 Mg 的林冠交换通量高于干沉降通量，并且 Ca 和 Mg 被吸收，而 K 在降水穿过林冠时被淋失。因此，结果表明，在亚高山森林生态系统中，降水过程中的林冠交换是碱基阳离子输入的主要控制因素，林冠可以改变降水对碱基阳离子的汇源。
