Effect of site factors on the growth of Cunninghamia lanceolata (Lamb.) Hook plantations in northeast of Vietnam

Abstract

The results of analyzing the effects of some site factors on the growth of
Cunninghamia lanceolata plantations in the Northeast shows: Growth DBH
was most influenced by the planting density (26.11%) and temperature
(24.91%), soil bulk density (10.79%), slope (8.34%), rainfall (6.29%) and
total nitrogen (3.8%). With tree height growth, the intrinsic factor is the age of the tree with the highest effect, accounting for 30.73%; site factors such
as temperature account for 23.50%; altitude 12.32%; slope 10.93%, soil
bulk density 7.41% and total nitrogen in soil affects 3.02%.
There are 7 out of 16 factors, representing 77.27% of the impact on the
volume of Cunninghamia lanceolata plantations. The slope has the most
influence on 24.36%, temperature affects 22.28%, forest age affected
8.39%, sandy element 7.24%, CEC 4.81% and total nitrogen influence
4.36%.
Seven out of 16 factors account for 70.47% of the relationship between
these factors and the overall average growth of the stock, which is most
affected by the annual temperature (23.93%)., slope (14.79%), sand
element (14.61%), forest age (4.37%), total nitrogen (1.88%), clay element
(7.32%) and soil bulk density (3.57%).
Analyzing total 20 variables, including 16 site variables and 4 intrinsic
variables, determining the model of the correlation between forest stand
reserves with 11 variables: M = 605,037 - 9,08654 * dbh + 1,19292 * do
doc + 51,9202 * dtrong + 6,6255 * G + 8,76694 * Hvn + 0,203093 * limon -268,909 * log (nhiet do) - 3,39487 * log (om) + 8,21362 * log (p) +
5,37673 * log (age) + 74,1257 * log (dt).