Rainfall interception in temperate evergreen broadleaved forest and Japanese cypress plantation with abundant lower-layer vegetation in south-west Japan

The interception of rainfall in conifer plantations has been intensively studied. However, research on broadleaved forests is limited, although the broadleaved forests dominate approximately half of forest area in Japan. Here, we compared the throughfall and stemflow of each vegetation layer to clarify interception in a naturally regenerated temperate evergreen broadleaved forest (lucidophyllous forest) and a Japanese cypress plantation over a three-year period. Both forests were approximately 100 years old and had abundant lower-layer vegetation. We found that approximately a quarter of rainfall was intercepted in both forests, although the half of that interception in the Japanese cypress plantation was owing to the abundant lower-layer vegetation. This indicated that the interception in the evergreen broadleaved forest was twice that of the Japanese cypress upper canopy. The well-developed layer structure in the evergreen broadleaved forest efficiently intercepted rainfall. From the point of view of water resource management, this study implies that both evergreen broadleaved forests and Japanese cypress plantations with abundant lower-layer vegetation can decrease the amount of water infiltrating soils.

针叶人工林的降雨截留已得到广泛深入的研究。然而，尽管阔叶林约占日本森林总面积的一半，针对阔叶林的相关研究仍较为有限。本研究为期三年，对比了天然更新的温带常绿阔叶林（lucidophyllous forest，常绿叶林）与日本扁柏人工林各植被层的穿透雨（throughfall）与树干茎流（stemflow），以明确二者的降雨截留特征。两处林分的树龄均约为100年，且下层植被均较为繁茂。研究发现，两处林分的降雨截留量均约占总降雨量的四分之一，但日本扁柏人工林的截留量中有一半源于其繁茂的下层植被。这表明，常绿阔叶林的降雨截留量是日本扁柏上层林冠截留量的两倍。常绿阔叶林发达的层状结构可高效截留降雨。从水资源管理的视角来看，本研究表明，无论是常绿阔叶林，还是下层植被繁茂的日本扁柏人工林，均会减少土壤入渗水量。