Litter Fall, Leaf Production and the Effects of Defoliation by Tortrix Viridana in a Sessile Oak (Quercus Petraea) Woodland

Abstract

A mature Quercus petraea woodland on a siliceous site in a high rainfall (171.4 cm/annum) area in North Lancashire produced in the 1961-64 period an average of 23.60 x 106 leaves/ha/annum with a mean dry weight (seasonal maximum) of 3820 kg/ha and a mean area of 4.87 ha/ha. The leaf area index was lower in the summer following defoliation by Tortrix viridana L. than in years of low Tortrix activity, but defoliation had little effect upon total annual leaf production in terms of dry weight. The dry weight of the total litter fall (leaves, twigs, flowers, acorns, etc.) was 3858 kg/ha/annum; the autumn leaf litter fall averaged 2206 kg/ha/annum. The total litter fall per annum contained 41.06 kg/ha N, 2.19 kg/ha P, 10.51 kg/ha K 23.83 kg/haCa, 3.87kg/ha Mg, 1.67 kg/ha Na, 117.38 kg/ha ash, 1959.61 kg/ha C and 18.63 x 106 kcal/ha of energy. The N content of the litter was high compared with that of other woodlands. Although the small non-leafy material such as male flowers, bud scales, insect frass, etc., accounted for only 14.7% of the dry weight of the litter, they contained 29.9% of the N, 40.2% of the P and 25.1% of the K in all types of litter. Most of these small materials fall in the spring and early summer and should be taken into account in investigations of seasonal variations in soil micro-organism activity.