To study the disturbance effect of forest fire on the carbon cycle of coastal sandy forest ecosystem

taking Eucalyptus urophylla × Eucalyptus grandis plantation and Casuarina equisetifolia plantation as research objects

the LI-8100 soil CO

2

flux automatic measurement system was used to measure the soil CO

2

flux of burned and control plots in different plantations. A

t the same time

soil temperature and moisture

soil pH

total carbon

total nitrogen and mineral nitrogen contents in the sample plots were measured. The relationship between soil CO

2

flux and water and heat factors as well as the changes of soil physical and chemical properties were analyzed. The results showed that the soil CO

2

fluxes in the burnt plots were significantly lower than those in control plots

the monthly average of soil CO

2

fluxes in the E. urophylla × E. grandis forest burned plots and the control plots was 2.47 and 3.32 μmol/(m

2

·s)

respectively

and that in C. equisetifolia forest was 2.48 and 3.28 μmol/(m

2

·s)

respectively. After the forest fire disturbance

the soil temperature and moisture of the two shelterbelt forests were higher than those of the control plots

in the exponential function model

soil temperature at 10 cm of E. urophylla × E. grandis and C. equisetifolia forest explained 10.4%~21.4% of the total soil respiration. In the binomial function model

soil moisture at 10 cm in E. urophylla × E. grandis forest and C. equisetifolia forest explained 15.8%~29.4% of the total soil respiration. In the bivariate regression model

soil temperature and humidity and their interaction together explained 33.1%~66.8% of the total soil respiration. Mild fire disturbance had little effect on soil pH

total carbon

total nitrogen and mineral nitrogen content in E. urophylla × E. grandis and C. equisetifolia forest

the soil pH of the burned area in the two types of forest both increased

and the contents of NH

4

+

-N and NO

3

-

-N decreased. In summary

forest fire disturbance would significantly reduce soil carbon emission of two shelterbelt forests in the study area. The fitting effects of the bivariate model of soil temperature and humidity in different plots were all better than those of the single factor-model

indicating that soil carbon emission was affected by both

which could provide reference

data and theoretical support for the research on the impact of forest fire disturbance on the soil carbon balance of coastal sandy shelter forests under the background of climate warming.