Vertical distribution and seasonal changes of fine and coarse root mass in Pinus kesiya Royle Ex.Gordon forest of three different ages

Abstract

Abstract Seasonal changes and vertical distribution of fine ( Pinus kesiya and fine root and rhizome mass of herbaceous species, and root production were studied in the 6-, 15- and 23-year old Pinus kesiya forest stands at Shillong, in the Meghalaya state of north-east India. Maximum fine and coarse root mass of P. kesiya, and fine root and rhizome mass of the ground vegetation were recorded during the rainy season. The contribution of the tree fine roots in 0-10 cm soil layer declined from 51% in the 6-year old stand to about 33% in the older stands. The major proportion (63-88%) of herbaceous fine root and rhizome mass was concentrated in this soil layer in all the three stands. The majority (36-57%) of tree coarse roots were present in the 10-20 cm layer in all the stands. The biomass and necromass values in the case of fine roots were more or less equal in a given stand, but the coarse roots had 5 to 9 times more live than the dead mass. The proportion of herbaceous fine root mass to the total fine root mass declined from 54% in the 6-year old stand to 30-32% in the 15- and 23-year old stands. The mean total fine root mass (pine + herbaceous species) decreased from 417 g m –2 in the 6-year old stand to 302 in 15-year and 322 g m –2 in the 23-year old stand. Annual fine root production showed a marked decrease from 1055 g m –2 in the 6-year old stand to 743 g m –2 in the 23-year old stand, but coarse root production increased from 169 g m –2 in the 6-year to 466 g m –2 in the 23-year old stand; the total root production thus remained approximately constant.