AimsThis　study　experimentally　investigated　the　short-term　(about　6　months)　effects　of　roots　of　Cynodon　dactylon　on　the　gas　permeability　and　gas　diffusion　coefficient　of　soils　with　different　degrees　of　compaction.MethodsCompacted　soil　planted　with　Cynodon　dactylon　were　left　outdoors　for　about　6　months　for　plant　growth.　The　measurements　of　rooted　and　bare　soils　included　gas　permeability,　gas　diffusion　coefficient,　root　characteristics　and　soil　microstructure.　The　relative　effects　of　different　root　characteristic　parameters　on　gas　permeability　and　gas　diffusion　coefficient　were　compared　through　grey　relational　analysis.ResultsThe　root　volume　ratio　had　a　greater　effect　on　gas　permeability　and　gas　diffusion　coefficient,　compared　with　root　area　index,　root　area　ratio,　root　length　density,　and　root　biomass　ratio.　When　the　degree　of　compaction　&　GE;　85%　(porosity　&　LE;　0.41,　bulk　density　&　GE;　1.56　g　cm(-3)),　the　macro-pores　at　the　root-soil　interface　increased　gas　permeability　and　gas　diffusion　coefficient,　while　negligible　effects　of　roots　on　gas　movement　existed　under　degree　of　compaction　of　80%.　The　increase　in　gas　permeability　by　roots　was　more　significant　than　that　in　gas　diffusion　coefficient.　However,　roots＇　increase　of　gas　movement　generally　decreased　at　higher　root　volume　ratio　due　to　roots-occupied　soil　pores.　Finally,　gas　permeability　and　gas　diffusion　coefficient　of　rooted　soil　were　well　predicted　by　newly-developed　empirical　models　considering　the　effect　of　root　volume　ratio.ConclusionsMacro-pores　at　the　root-soil　interface　tended　to　increase　gas　permeability　and　gas　diffusion　coefficient　of　soil　with　a　degree　of　compaction　&　GE;　85%,　while　it　is　the　opposite　for　root　volume　ratio.