Relationships of condensed tannin content in larch needles with larch stand age and its family

In order to study the effects of larch stand age,its family,and growth period on the constitutive resistance of larch needles,the needles of Larix olgensis 73-26,L. olgensis 73-28,L. kaempferi 5×L. gmelinii 9,and L. kaempferi 3×L. gmelinii 2 in different stand age groups were collected in July and August,with their condensed tannin content analyzed. The condensed tannin content in larch needles differed significantly under the interactive effects of stand age × family and of stand age × family × growth period,being significantly higher in young than in middle-aged and near-matured stands,in L. kaempferi 5×L. gmelinii 9 and L. kaempferi 3×L. gmelinii 2 than in L. olgensis 73-26 and 73-28,and in July (fast growth period) than in August (slow growth period). It was suggested that more hybrid larch with stronger constitutive resistance should be planted,and the pest control for middle-aged and near-matured larch stands should be strengthened after August.