The works of shelterbelt establishment in Hokkaido for a quarter century have not shown good results, because of the easy dependence on planting exotic pines and on wind fences, instead of land-preparation and indigenous trees and shrubs. More green belts are required urgently by present human societies. Therefore, we must investigate natural forests in invasion and growing, and create sound methods and engineering of belt establishing. Natural forests develop uniformally on the bare, immovable and suitably moistured soil surfaces which are caused by some of topographic changes- landslide, rupture of surface soil, ash fall, etc. Topographic changes in nature destroy pre-existing vegetation and give the places without competition for trees' invasion. Of environmental conditions around shelterbelts, soil is improved remarkably by our land-preparation. Land-preparation is artificial topographic changes for tree planting and composed of drainage, uprooting pre-existing vegetation, transporting soils for better rooting medium, and cultivation for weed control. Without competitions and with better soil in physical properties, pioneer trees and shrubs, planted by seedlings, wood-cuttings or direct sowing, can grow freely against anti-growing factors and form bushy belts which give better environment to proper trees. And hedge planting with machines will cause us a systematic engineering in shelterbelt establishment from land-preparation, pioneer bush, proper trees, weeding, until regeneration.(Fig.1)

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i)トドマツ林と同等の成長をしているアカエゾマツ林の養分の現存量はトドマツ林よりすくなく,また最近の年吸収量もすくなくないと推定され,これらの事からアカエゾマツはトドマツより要分の要求度はすくないと考えた。ii)森林生態系の養分分布をみるとA_0層の乾物重や養分含有量はトドマツ林よりアカエゾマツ林で多い。このことからアカエゾマツ林はトドマツ林より落葉分解の段階で養分循環が停滞していると考えた。

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Two individuals with special flowering habit were found in a plantation for experiment of Kurile larch (Larix gmelinii var. japonica, from the Kurile and Saghalien) and named as V-544 and V-545 in 1968. They are very similar to ASFL-1 of Japanese larch (L. Ieptolepis) selected by Mr. MOMOSE in the district of Mt. Asama, Pref. Nagano (Table 2), in the habit of bearing only female strobili nearly exclusively on the annotinous growth of shoots, almost annually, and from early (younger) age (9 years of age in V-544), with a few minor differences among them. The clones of these two trees came to bear female strobili in 1〜2 years when budded on adult trees of Japanese larch in the crowns, while in 4〜5 years when budded on two-or three-year-old seedlings. In artificial crossings of inter-and intraspecific combination they produced moderate amounts of seeds. And the seedlings from these seeds grew as well as those of ordinary combinations (Table. 5). Therefore, these precocious trees can be utilized as temporary seed trees before the mass production of seeds of improved quality is realized, upon condition that their progenies will never serve as seed suppliers for practical silviculture. In the survey of the seed stand, in which the above-mentioned plantation has its seed source, at Numakawa, Wakkanai, in the spring of 1968, several trees were also marked by the similar flowering habit, and one of them (V-1481) was supposed as the mother tree of these precocious trees.

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17,15年生トドマツ植栽本数試験地4ヵ所(表-1)の密度と生長の関係を調べた。その結果 1) 17年生の試験地の1ヵ所(No.1試験地)では5,000本区が11年時に閉鎖を始め,13年時には3,000本区以上が閉鎖状態になり,4,000本区と5,000本区との間で密度の影響が直径に現われた(図-3)(3,000本区は地位の影響があるため除外;図-4参照)。15年時には各区とも完全に閉鎖し,4,000本区と5,000本区の直径差が更に大きくなった。閉鎖の進行状態を樹冠率(表-2・3)で表現して見たところ,17年時の5,000本区は69.2%(下枝の枯れ上り率30.8%)になったので利用最小径級も考慮に入れて,この中に間伐試験区を設定した。2) 17年生試験地のうちもう1ヵ所(No.2試験地)は唯1回の調査であるが,3,000本区以上が閉鎖直前か或いは閉鎖していて(表-2)直径生長にも密度の影響が現われていた(図-3)。樹冠率はやや高かったが5,000本区の中に間伐試験区を設けた。3) 15年生試験地のうち1ヵ所(No.3試験地)では6,000本区が10年時に閉鎖を始め,13年時には4,000本区が閉鎖を開始し,6,000本区は完全に閉鎖した(表-5)。15年現在4,000本,6,000本区が完全に閉鎖し,3,000本区が閉鎖に近づきつつあり,2,000本区は未だ閉鎖していない。密度の直径生長への影響は閉鎖の一番強い6,000本区に現われ始めている(図-5)。4) 15年生のもう1ヵ所(No.4試験地)の試験地は樹冠の巾が非常に広く,15年現在全密度区が閉鎖状態で,その影響が直径に僅かに現われ始めている(図-7)。

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昭和42〜45年の4年間,カラマツのツギキクローン(樹令10〜14年生)及び実生親木(12〜14年生)を用い,親木の個体別に空中トリキと一部サシキ試験を行った。(1)NAA5〜20mgTalc処理によって多くの親木個体で容易に発根させることが出来た。ホルモン濃度は6月トリキでは低濃度,7月では高濃度処理がやや良かった。剥皮については完全剥皮の場合はホルモンの濃度間に違いが少なかったが,半剥皮,長さ3cm2ケ所,無剥皮では高濃度処理が良く効いた(図-3)。(2)剥皮処理では半剥皮がよく,完全剥皮よりも(図-2)枯死がなかった。さらに簡単な方法として「長さ3cm2ケ所」及び無剥皮処理でも発根することがわかった。(3)樹種別の発根率をみると,ツギキ親木では朝鮮カラマツ.日本カラマツ,グイマツの順によく発根したが,実生親木では,産地や樹種の特性によるのかグイマツ,朝鮮カラマツ,日本カラマツと発根順位に違いがみられた。(4)根は短枝から出やすく(48.3〜53.3%),完全剥皮より半剥皮の場合やや多かった。切り口からの発根は逆に完全剥皮で多かった(表-3)。(5)4〜7月上旬頃まで良く発根したが,それ以後は急激に低下した。(図-5)更に得苗率の向上等を考えると5・6月頃の早い時期のトリキが良いと考えられる。(6)樹高6〜8mの親木に対するトリキ位置は,高さ1〜1.5mの下部よりは3〜4mの上部で,光のよく当る枝の方が発根率が良かった(図-6)。(7)44〜45年のトリキで発根しやすい個体としにくい個体のあることが確かめられた(図-7)。(8)4年間の短かい期間でも,年令の増加と共に発根率の低下する傾向がみられた(表-4)。(9)トリキ苗の養苗に於ける得苗率は一般に悪く,ツギキ親木でこの傾向が著しかった。しかし,活着した苗木の生育は1〜2年間は思わしくなかったが,3年目には非常によく生長した。(10)サシキはトリキに比べ発根率が悪く,両老の発根性を比較検討出来なかった。(11)サシキはツギキ親木より,実生親木の方が発根しやすい傾向を示した(図-2)。(12)サシキで良く発根した個体でも,トリキで発根しやすいとは限らず発根性は一致しなかった。

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It was mentioned in the previous paper on the basis of the investigation on pollen density in the air in May 1971, that pollen dispersal of larch was more vigorous under the condion of higher temperature and lower relative humidity, and that the dispersal from a stand to others in some distances was smaller than expected. The germination test of the seed lots obtained from these stands in the autumn of 1971 shows that the germination percentage is higher in the stands of higher pollen density while lower in those of lower density. The records of the flower density in the crowns and seed germination of all or several trees within a stand and the number of pollen grains caught by traps settled at different heights in the same stand, for the period from 1968 till 1972, were also compared (Fig.2 and 3). According to this comparison. the dispersal of pollen within a stand is restricted in rather narrow range ; and consequently the frequency of crossing of a tree seems to be the highest between it and the contiguous trees while reducing rapidly between it and the second, third and further. The direction of prevailing or constant wind also seeme to give a large influence on this frequency. In another pollination test with various amounts, the injection of 20mg of pollen into an isolation bag showed a pollen density of 2477 (represented by the number on 1cm^2 of slide) which was nearly the same as that caught by tie trap (2359/cm^2) in the year of the highest germination percentage. Any larger amount may not be necessary for the artificial pollination.

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A snow blight fungus on Abies sachalinensis and Picea jezoensis, Phacidium abietis (DEARN.) REID and CAIN, was reported by the authors in 1968. This fungus is known as a pathogen of various species in Abies, Picea and Pseudotsuga in Canada and the U. S. A.. Phacidium. infestans KARST., another species attacking Pinus, is reported in Europe. As there are no reports on the exact host ranges of those fungi, inoculation experiments of Phacidium abietis were made at the Tokyo University Forest in Hokkaido, Japan in December, 1968. Potted seedlings of 12 species of conifers were placed on the ground and diseased needles of Abies sachalinensis were put on them. Then, all of seedlings and diseased needles were covered by snow. After the treatment, they were kept under the natural condition through the winter. The observations on inoculated seedlings were made in the next year. The results showed that the most susceptible species were Abies sachalinensis, Abies balsamea, Picea jezoensis and Picea polita. The medium susceptible species were Pciea abies, Picea pungens, Pinus koraiensis, Pinus strobus, Pinus tabulaeformis and Pseudotsuga menziesii. Picea glehnii and Pinus resinosa were resistant. Apothecia of this fungus were observed on needles of Abies sachalinensis, Abies balsamea, Picea jezoensis, Pinus koraiensis and Pinus strobus in autumn of the year. The heavy defoliation of diseased needles were recognized in Picea abies, Picea glehnii, Picea polita and Pseudotsuga menziesii. Among them, a few needles of Picea glehnii were affected but most of them were difoliated. By the results of the field observations and collections, apothecia of this fungus were found on Picea glehnii and Pines pumila at the natural forest in Hokkaido, Japan.

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