Effects Of Soil Compaction On Soil Respiration In Forest Site

Soil respiration (SR), Including the root and the foundation respiration, is an important part of carbon cycling in terrestrial ecosystems.In forest operations, the soil compaction caused by people, livestock, machinery, as well as the interference and compaction of different cutting intensity to the forestry soil, both have corresponding effects on the soil respiration, and thus affects the absorption of nutrients of plants. This thesis, from the microcosmic perspective, makes further and detailed expatiation of the change of soil respiration after the soil compaction on the basis of differential calculus, and established the mathematical model. In this study, it measures the soil respiration speed and CO₂ density, as well as the physical properties, of the selected terra in Dongfanghong experimental forest field of Dailing forestry bureau and NEFU experimental forest field by using the infrared gas exchange analyzer (LI-8100). It also measures the rigidity of the soil of the selected terra in NEFU experimental forest field by the soil rigidity tester.It analyzes the influencing factors of soil respiration speed of the after-operation forest ground by using Multiple linear regression analysis and SPSS software. It makes the computerized emulational analysis of the influencing situation of the soil respiration of the field ground of various compaction degrees. By comparing the measured value and the theoretical value, it verifies the mathematical model.The soil compaction level, which is the increase of soil rigidity, can decrease the soil porosity and percentage of moisture, and increase the soil bulk density and saturation, especially the CO₂ density and initial flux, which has the same law with the model emulational results. However, in the model validation, it is found that there is error between the theoretical value and real measured value, and it analyzes the cause for the error.There is obvious positive correlativity between the pervasion distance, soil compaction, soil saturation percentage of moisture, soil humidity, soil temperature of CO₂ gas molecule and soil respiration velocity, and can be used as the explanation variable of soil respiration speed. The compaction index is the ratio of soil porosity variable and the soil-endured outside force variable, and relates to the nature of soil; while the atmospheric pressure is the environmental elements, and doesn't directly influence the soil respiration speed.To make the emulational value analysis for the built math model with the Matlab software. The result shows that: on the same ground conditions, the obvious negative correlativity between the compaction index A and the outside force side P, the obvious positive correlativity between carbon dioxide density value and pressure P, the parabola-shape relationship between the pressure P and survey depth. There is a trend of increase in CO₂ density with the increase in the soil depth; the more serious it is stirred, the greater the increase degree is. That is, the CO₂ density increases and then goes to be flat with the increase of the soil compaction degree.