EFFECTS OF FOUR DIFFERENT THINNING INTENSITIES ON THE STOICHIOMETRIC CHARACTERISTICS OF SOIL CARBON, NITROGEN AND PHOSPHORUS IN CYCLOBALANOPSIS GLAUCA COPPICE

Abstract:

In order to understand the effects of different thinning intensities on the content and stoichiometric ratios of C, N, P in the soil of Cyclobalanopsis glauca coppice, the completely crown closure Cyclobalanopsis glauca coppice, which was in the western of Hu’nan Province in China, was chosen. According to the randomized block design method, a total of 12 plots with four thinning intensities (CK, 15%, 30% and 50%) were set up, and the size of each plot was 1000 ㎡ (25 m x 40 m). The soil samples of 0-10 cm, 10-20 cm and 20-30 cm after thinning for 1 year were collected to determine the content of TC, TN and TP and calculate the ratio of C, N, P. Two-way ANOVA with Duncan’s post hoc multiple comparisons were performed to examine the effect of the different intensities on the C, N, and P and test the differences in the soil layers of each treatment, respectively. The results showed that: (1) Except for the stand with 30% thinning intensity, the contents of TC, TN and TP in soil decreased with the increase of soil depth; while the soil contents of TC, TN and TP in the stand with thinning intensity of 30% decreased first and then increased. (2) In each soil layer, there was no significant difference between TC and TN content under different thinning intensities (p > 0.05), but the soil TP content under 30% thinning intensity was the lowest and significantly different from the other three thinning intensities (p < 0.05). In addition, in soil layer of 0-30 cm, the order of average TC and TN content under different thinning intensities was CK >30% >15% >50% , and the order of average TP content was 15% > CK > 50% > 30%. (3) Under the same thinning intensity, the ratios of C:N, C:P and N:P between the topsoil (0-10 cm) and other soil layers were significantly different (p < 0.05). In the same soil layer, the ratios of C:N and C:P between the stand with 30% thinning intensity and that with 50% thinning intensity were significantly different (p < 0.05), while the N:P ratios in the stand with different thinning intensity were not significantly different (p > 0.05). Additionally, the ratio of C:N:P under different thinning intensities decreased with the increase of soil depth, and the order of the ratios of C:N:P in the same soil layer under different thinning intensities was: 30% > CK >15% > 50%. We proposed that 30% thinning intensity and CK were more favorable to the content of carbon, nitrogen and phosphorus in the soil of Cyclobalanopsis glauca coppice.