3.2. Contribution of soil CO2 flux in deep
profile to soil-atmosphere interface
In the growing season, the average proportion of CO2flux at deep layers (80-200 cm) to the total CO2 flux at
the soil-atmosphere interface in Robinia pseudoacacia (CH10a,
CH20a, CH30a, CH40a) and crop land was
11.14%、21.71%、27.43%、23.42% and 24.00%, respectively. while that
was 8.50%、13.17%、23.83%、12.67% and 19.33% in non-growing
seasons. The proportion in the growing season was discrete, but the
proportion in non-growth season is relatively concentrated. This
indicated that the proportion of CO2 flux at deep layers
fluctuated greatly ( Fig. 3A).
It is a dynamic process for the CO2 emission from each
section of the profils to the soil-atmosphere interface. Therefore,the
static assessment method which take the average proportion of
CO2 fluxes at deep layers as index system may
overestimate or underestimate contribution of CO2 flux
in deep layers to soil-atmosphere interface. In order to accurately
assessment contribution of CO2 flux in deep layers to
soil-atmosphere interface, we took accumulated variance contribution of
proportions as index system dynamic assessment. During the whole
season,accumulated variance contribution of proportions at the deep
layer (80-200cm) in Robinia pseudoacacia (CH10a, CH20a, CH30a,
CH40a) and crop land was 9.74%, 23.61%, 21.81 %, 22.92% and
24.42%,respectively (Fig. 3B). The contribution of CO2flux at deep layers to the total CO2 flux at
soil-atmosphere interface increased with with the increase of
restoration time.