Light energy gain and carbon balance of the seedlings of Quercus serrata in natural reproduction sites by the shelterwood method

以锯栎为主的落叶灌木林广泛分布在日本的城市和农村。在20世纪50年代至70年代，这里积极进行针叶树造林。但近年来，充分利用本土阔叶树种进行自然繁殖的新趋势在人们中逐渐兴起。母树法和防护木法具有许多优点；例如易于执行，能够缩短再生周期等。进行了各种基础研究和技术试验，以检验这些自然繁殖方法对塞拉塔的适用性。冠层乔木几乎每两年出产一次好种子，每隔6或8年出产一次大丰收。在树木结籽较多的年份，提供了较多的成熟种子。大部分种子落在树冠下或树冠附近，主要在地表较低的地方收集。落籽之后是落叶，也以同样的方式收集叶子来覆盖种子。因此种子可以避免干燥损害。幼苗在当年期已经表现出较高的叶片光合能力，60% ~ 70%的幼树没有发现光合作用的光抑制现象。即使在夏季无雨期，当年幼苗日间气孔导度也保持较高，这可能与根系发育明显有关。第二年，杂草和灌木开始茂盛生长，抑制了幼苗的某些部分。然而，如果能人为地限制竹草的旺盛生长，那么锯齿木的再生最终是成功的。挖土机对于清除地下的竹草等杂草极为有效。虽然使用这种重型机械压实土壤，但对幼苗光合性能和生长反应的影响可以忽略不计。

Deciduous coppice forests dominated by Quercus serrata are widely distributed around cities and farm and mountain villages in Japan. Afforestation by conifers was actively made there during 1950's to 1970'. But recently the new trend towards natural reproduction by making full use of native broad-leaved tree species have been growing among people. The mother tree method and the shelterwood method have a number of advantages ; e.g. easily performed, enable to shorten the regeneration period and so on. Various fundamental studies and technical tests were carried out in order to examine applicability of these natural reproduction methods for Q.serrata. The canopy trees produced good seed crop almost every two years, bumper seed crop at intervals of 6 or 8 years. Larger number of mature seeds were supplied at years when the trees bore more seeds. Most of seeds fell right under tree crowns or near around them and collected mainly at low spots on the ground surface. The seed fall was followed by leaf fall and the leaves also collected in the same manner to cover seeds. So seeds could avoid desiccation damage. Seedlings showed , already at current year stage, high photosynthetic ability in leaves, 60 to 70 % of young trees, and the photoinhibition of photosynthesis was not observed. Daytime stomatal conductance of current year seedlings was kept relatively high even in non rain fall periods in summer, probably due to marked development of their root system. At the following year weeds and shrubs started to grow thick and suppressed certain parts of the seedlings. It appeared, however, that the regeneration of Q.serrata would succeed finally, if vigorous growth of bamboo grasses could be restricted artificially. Use of backhoe was extremely effective for removing under-ground system of bamboo grasses etc. Although soils were compacted by using such heavy machinery, the influence on photosynthetic performance and growth reaction of the seedlings was negligible.