三、 The movement of soil air (一)、 Convection( Mass flow) Convection -The soil air is transferred from higher pressure area to lower pressure area. D q -(k nVp Where gv is the volume convective flux of air; k is the permeability of the air-filled pore space; n is the viscosity of soil air; vis the pressure gradient in soil air
二、 The movement of soil air （一）、Convection (Mass Flow) Convection –The soil air is transferred from higher pressure area to lower pressure area. Where qv is the volume convective flux of air; k is the permeability of the air-filled pore space; is the viscosity of soil air; is the pressure gradient in soil air. qv = −(k /)p
(二)、 Soil air diffusion .a difference in the concentration of a particular gas in one zone compared with any other zone in the soil can result in the movement of that gas by a process called diffusion The process of diffusion can be represented by a flow equation in which the driving force is the gas concentration gradient (Fick’sLaw) gd==D x .where qd is the diffusive flux(mass diffusing across a unit area per unit time), d is the gas diffusion coefficient, and dc/dx is the concentration gradient of the gas Soil respiration
（二）、Soil air diffusion • The process of diffusion can be represented by a flow equation in which the driving force is the gas concentration gradient (Fick’s Law). dx dc qd = −D •where qd is the diffusive flux (mass diffusing across a unit area per unit time), D is the gas diffusion coefficient, and dc/dx is the concentration gradient of the gas. •A difference in the concentration of a particular gas in one zone compared with any other zone in the soil can result in the movement of that gas by a process called diffusion. Soil respiration:
Section Soil hea
Section 2 Soil heat
一、 The source of soil heat 太阳人 云层散射 大气散射 大气吸收 (-- Solar radiation Solar radiation is the 太 primary source of energy to heat soils But clouds ad dust particles intercept the sun's 达辐射 rays and absorb, scatter, or reflect most of the energy. E 图62地面辐射平衡示意图
一、The source of soil heat （一）Solar radiation Solar radiation is the primary source of energy to heat soils. But clouds ad dust particles intercept the sun’s rays and absorb, scatter, or reflect most of the energy. H I E a
(二) Biologicalheat Organic matter is decomposed y microorganism. (-) Heat inside the earth
（二）Biological heat Organic matter is decomposed by microorganism. （三）Heat inside the earth