The natural vegetation process and the effect of afforestation work were studied on the pumice plain of Komagatake volcano, southern Hokkaido, Japan. The barren land, newly formed after a huge eruption in 1929, was mainly revegetated naturally by willows (Salix reinii and Salix integra), birches (Betula platyphylla), poplars (Populus sieboldii and Populus maximowiczii), and larch (Larix leptolepis). All the trees had extremely low growthrates attaining less than 3 m in height over 60 years ; low water and nutrient availability probably limited growth.Tree ring analysis demonstrated that willow, poplar and birch have steadily invaded over the first 40 years, butthat the non-native larch has remarkably increased within the past ten years. The forests have been changingfrom early successional deciduous trees to larch. The tree plantation work to promote earlier forest establishmentwas also carried out for the past 30 years. Four species were planted: larch, alder, pine and birch. The plantedlarch had the highest growth rate, followed by alder and pine. These planted trees reached 5 m to 8 m in heightwith the exception of birch. Soil condition on the understory of the plantations were remarkably improvedcompared to natural sites with a well-developed A-horizon and high nitrogen content. Plantations are successfulfor rapidly establishing forest and accelerating succession process on land devastated by volcanic activity.

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In order to study the effect of roadside planting in filtering atmospheric pollutant, wind tunnel experiment andfield study were conducted. Leaves of four species of trees were exposured in the tunnel at different windvelocities and their adsorption of particles were measured. In the road side of highway, adsorption of metal (Zn, Ca, Mn, Fe) by leaves of two tree species (Pasania edulis Makino and Ilex rotunda Thunb.) were also measured.
As results of tunnel experiment, we found adsorption of particles by leaves decreased in the order Pinus thunbergii Parl, Neriurn indicum Mill, Pasania edulis, Quercus rnyrsinaefolia Blume. The volume of adsorbedparticles were influenced by the nature of leaf surface where hairy leaves, rough and sticky leaves being moreefficient at adsorption of particles than smooth one. The volume of adsorbed particles increased with windvelocities and the increasing rate was the highest on Pinus thunbergii.
From the field studies, we found that the adsorption of metal by old leaves were higher than new one. Itprobably due to old leaves being exposured to atmosphere longer than new one. Seasonal variation of metaladsorption were influenced strongly by rainfall rather than concentration of suspended particulate matter.Generally, the volume of adsorbed particles tended to increase when it was small rainfall.

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The stem-top diameter and the basal branch diameter of each Salix matsudana, directly planted by large cuttings in the Mu Us Shamo Desert, Inner Mongolia of China, was measured in order to estimate the amount of harvest of fodder in winter. The shelterbelts for studies were located in the western side of the Mu Us Shamo Desert Research Center and the Eastern Experimental Field.
The results may be summarized as follows: 1) The normal-distribution pattern of individual stem-top diameters measured at the eastern shelterbelt was nearly normal. Otherwise, the distribution pattern at the middle shelterbelt was wider than at the eastern one. 2) The stem-top diameter of individuals with first sproutingbranches was shorter than that of one with second sprouting branches. 3) The relationship between the stem-top diameter and the number of branches was varied with branch orders. The relationship between stem-top area and total basal area of branches was varied with branch order, similarly. The ratio between total basal area of branches and the stem-top area was calculated. The distribution class of ratio of cuttings with second order branches was lower than that of cuttings with first order branch. As mentioned above, the number of branches and branch order were closely associated with stem diameter growth.

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[in Japanese]

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