The Effect of Forest Floor Cutting and Fertilizing on Producing Blooms of Rhododendron Reticulatum

27 Mar The Effect of Forest Floor Cutting and Fertilizing on Producing Blooms of Rhododendron Reticulatum

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Abstract

二次林林床に自生するコバノミツバツツジは, 林内の光条件を改良すると翌春には良好な着花が達成されるが, その効果は1年のみで, 再び急激な着花不良を生じた. 施肥により良好な着花が得られたことから, 着花不良は腐植の流亡により土壌養分が欠乏したためと推察され, 傾斜地での施業には単に光条件の改良だけでなく, 土壌保全も不可欠であると結論づけられた. また本種の萌芽更新は, 着花を著しく遅らせることが明らかとなった.

English Abstract

In a previous report, it became apparent that Rhododendron reticulatum, a type of wild rhododendrons, can produce many blooms when thinning increases light level on the floor of abandoned secondary woodlands, or coppices. However, the effect of the improvement was not retained. It was suggested this result was due to the fact that since the experimental stands had been a slope, the cleared floor could not effectively hold fallen leaves and this had led to humus erosion. Therefore, experimental work was conducted to test the hypothesis that soil-nutrition shortage is the cause of few blooms.
The results of the study are as follows: The fertilized R. reticulatum produced many blooms in both light and dark stands, whereas previously it had been difficult to produce enough blooms in relative light intensity below 20%. Furthermore, in the case of non-fertilizing, R. reticulatum had few blooms even in the light stand. Judging from these results, it is believed that light condition is not a sufficient or necessary factor for flower formation. Therefore, our research points to the important role of soil conservation in improving woods for flowering of wild rhododendrons.
In another study of sprouts regenerated on stumps of R. reticulatum, it was concluded that good strub forms at about one meter in height could be produced three years after cutting. However, since these plants produced few blooms even five years after cutting, the aprout system is considered to be unsuitable for R. reticulatum.