Abstract:
Objective To explore the dominant ecological environment factors and stand control factors for the formation of large-diameter wood of Cunninghamia lanceolata in Nanling Mountains, investigate their influence rule and provide a theoretical guidance for cultivation and management of large-diameter wood stands of C. lanceolata in Guangdong Province.
Method Based on the investigation of the existing large-diameter wood stands of C. lanceolata in Nanling Mountains, the site index (SI), soil integrated fertility index (I), micro-topography index (M) and geographical index (G) were extracted and the index evaluation system was established. The relationships of large-diameter wood volume (Vl), output (Ol), proportion (ND≥26), outturn percentage (Yl) with each index were analyzed.
Result There were significant positive correlations of each index of large-diameter wood with SI,
M (
P<0.01), the correlation coefficients were 0.37−0.44 and 0.22−0.33 respectively.
Vl、
Ol and
ND≥26 had significant positive correlations with
I(
P<0.05), the correlation coefficients were 0.24−0.39.
Vl and
Ol showed a gentle quadratic curve trend of slowly increasing first and then slowly decreasing with the increase of reserved density (
D), the correlations were significant (
P<0.05). There were no significant correlations of
G, stand age (
A) with each index of large-diameter wood. The large-diameter wood output at the age of 20−30 was predicted by a quantitative model:
Ol=
\rme^\rm5\rm.781 + 0\rm.004\;\rmSI + 5\rm.004A^\rm - 1\rm + 0\rm.261\ln D\rm - 45\rm.151S\rmI^\rm - 1 (
R=0.62,
P<0.01).
Conclusion SI, I, M and D are the dominant impact factors for growth of large-diameter wood in Nanling Mountains. It is benefitial for large-diameter wood formation when SI is above 18, the soil has higher porosity, moisture and nutrient contents, the micro-topography condition is a shady and concave slope below 35° in the lower part, and the reserved density is 1 100−1 300 plants·hm−2.