Effects of density on growth and diameter distribution of young coppice stands of Mytilaria laosensis

ObjectiveReserved density of the stump sprouts is the key technology in coppice cultivation. It is very important to explore the effects of density on growth and diameter distribution of coppice stands of Mytilaria laosensis in order to get reasonable density for cultivating technology with the stands.

MethodUsing single factor randomized block designs, the experiment with the stump sprouts of Mytilaria laosensis in the clear-cut land of Mytilaria laosensis plantation, in three different levels of T_CA(reserved 1 sprout each stump), T_CB(reserved 2 sprouts each stump), T_CC(reserved 3 sprouts each stump) and repeated three times, was conducted with 5 years continuous observation data in 9 fixed plots to study the growth and diameter distribution of the coppice stands affected by density.

Result(1) During 1-3.5 years after sprouting thinning, total growth of the average diameter at breast height (DBH), average height, and average individual volume of coppices in the stands were not significantly affected by density. The growth of tree height for dominant trees of the sprout stands was not significantly affected by density. The total growth of individual volume for dominant trees of sprout stands was significantly affected by the density (P < 0.05), the annual increment of individual volume and the DBH growth of dominant trees were very significantly affected by density(P < 0.01). (2)All the peak values of annual increment of average DBH of stands, average tree height of stands, average DBH of top tree, and average tree height of the stands occurred in the second year, the intersected times of the average growth and annual growth of the stand DBH were during third year to fourth year, but the intersected times to the average tree height of the stands were during second year to fifth year. For the dominant trees, both intersected time of average growth and annual increment growth of DBH and tree height were very similar to the growth of stands. (3) After the second year, both annual increment growth of tree height with the dominant tree and the average tree obviously decreased. (4)All diameter distributions of coppices in the stands were part mountain shape distribution, which indicated that they were located in the late competition period. It had excellent fitting effects using the Weibull function to fit diameter distribution of coppices in the stands.

ConclusionIt is fast growth period for the radial and height growth of the stands before 5 years old, reasonable density and tending are extremely vital to the stands. Thinning measures within two sprouts in each stump can drastically increase the proportion of superior trees in coppices in the stands.