Litter Fall and its Annual and Monthly Fluctuations in Young : Thrift Loblolly Pine, Pinus taeda L., Stands over Seventeen Years

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  • テーダマツ幼－壮齢林のリターフオールについて
  • テーダマツ幼-壮齢林のリターフォールについて
  • テーダマツ ヨウ ソウレイリン ノ リターフォール ニ ツイテ

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The annual and seasonal fluctuations of litter fall and the grazing loss of leaves by the herbivorous insects were investigated in three Loblolly pine, Pinus taeda L., stands at Sirahama Experiment Station of Kyoto University Forest, Wakayama prefecture. The study sites were three experimental stands of Loblolly pine which planted at 2, 500 (A stand), 5, 000 (B stand) and 10, 000 (C stand) trees per hectare in March, 1961. Mixed fertilizer which contains nitrogen (15), phosphorus (8) and potassium (8) had been manured 100 grams per a tree in each stand for three years after planting annually. Four traps (from April in 1968 to April in 1975), each having surface of one square meter (1.0 m×1.0 m) and five traps (from April in 1975 to April in 1985), each having surface of one fourth square meter (50 cm × 50 cm), were set up in each pine stand. Fallen litters in each trap were collected twelve times for a year of one month interval from April 21 in 1968 to April 20 in 1985. Collected litters were divided into the components by hand sorting, i.e. leaves, branches including bark and sexual organs of Loblolly pine, feces of herbivorous insects, dead bodies or residues of insects and others. Annual leaf litter were collected from 3.00 ton/ha･yr to 6.47 ton/ha･yr (A stand), 3.23-7.13 ton/ha･yr (B stand) and 3.76-7.95 ton/ha･yr (C stand), and in the early years of investigation, there were a great deal of leaf litter particularly. The amount of leaf litter was on the decrease yearly, and the minimum leaf litter was weighed in 1977 each stand. Annual branch litter were collected 217.1-1, 239.0 kg/ha･yr (A stand), 92.3-1, 838.0kg/ha･yr (B stand) and 367.5-1, 404.0 kg/ha･yr (C stand), branch fall tend to increase with the growth of Loblolly pine in each stand. Sexual organs collected were a little in each stand. The feces of the herbivorous insects were collected 27.0-69.0 kg/ha･yr (A stand), 22.7-64.4 kg/ha･yr (B stand) and 24.2-59.5 kg/ha･yr (C stand), the range of these annual fluctuations were narrow in each stand. The feces of the striated chafer occurred in every other year were sometimes equivalent to 50% of annual feces. Total litter falls were collected 3.90-6.83 ton/ha･yr (A stand, 5.28±0.77 ton/ha･yr in average), 4.44-7.69 ton/ha･yr (B stand, 5.82±1.00 ton/ha･yr) and 4.53-8.48 ton/ha･yr (C stand, 6.44±0.98 ton/ha･yr), total litter in C stand consisted of high density were large compared with A and B stand. The annual loss of canopies by grazing of the herbivorous insects were estimated 49.9-239.7 kg/ha･yr. These grazing losses were equivalent to 1-8% of annual leaf falls and were negligible to the growth of Loblolly pine stands. [Table omitted]

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