Litter Dynamics And Decomposition Of Four Plantations In Coastal Sandy Land

Coastal sandy land is a transitional zone between land and ocean where human activities are frequent,soil nitrogen and phosphorus nutrients are scarce,seasonal drought is serious,and the ecological environment is fragile.As an important shelter forest along the Southeast coast,coastal sandy land plantation is experiencing structural and functional degradation due to global warming.The coastal shelterbelts in southeast coastal areas are mainly Casuarina equisetifolia,Pinuselliottii,Acacia aulacocarpa and Eucalyptus urophylla X E.grandis.Acacia aulacocarpa is best growing in Acacia species.We studied Acacia aulacocarpa,Pinuselliottii,Casuarina equisetifolia and Eucalyptus urophylla × E.grandis plantations in the coastal sandy land of Fuzhou city,measured the annual litter amount,litter stock and litter decomposition rate of four plantations by litter frame collection method,sample harvesting method and net bag decomposition method,and explored the monthly dynamics,annual yield and decomposition mechanism of litter in different tree species plantations on sandy land.It provides a theoretical reference for the selection and protection of dominant shelter forest species in coastal sandy land and the improvement of ecosystem stability of coastal shelter forest.The main findings are as follows:(1)The annual litter amount of Casuarina equisetifolia(16.31 t·hm-2·a-1)was significantly higher than that of Pinuselliottii(11.22 t hm-2·a-1),Eucalyptus urophylla × E.grandis(10.26 t·hm-2·a-1)and Acacia aulacocarpa(7.43 t·hm-2·a-1),and there was no significant difference between the annual litter amount of Pinuselliottii and that of Eucalyptus urophylla × E.grandis.(2)The monthly dynamic change trend of litterfall of 4 plantations in coastal sandy land is similar,with multi-peak curves.The maximum values of monthly litterfall in 4 plantations appeared in August.The litterfall was significantly higher in summer than in winter,and was dominated by litter and branchlets(Casuarina equisetifolia),accounting for 66.08%?84.39%of the total litter,followed by branches,accounting for 3.21%?18.03%of the total litter.(3)The litter stock of Casuarina equisetifolia(19.12 t·hm-2).and Pinuselliottii(17.51 t·hm-2)was significantly higher than that of Eucalyptus urophylla × E.grandis(10.90 t hm-2)and Acacia aulacocarpa(10.13 t·hm-2).The highest proportion of 4 plantations was litter leaves,accounting for more than 84%(except for Eucalyptus urophylla × E.grandis,the litter leaves of Eucalyptus urophylla × E.grandis account for 48%).Litter branches of Acacia aulacocarpa,Casuarina equisetifolia and Eucalyptus urophylla × E.grandis accounted for more than 12%,while litter fruit of Pinuselliottii accounted for 10%.The litter biomass in the semi decomposition layer was higher than that in the undecomposed layer.(4)The decomposition coefficient of litter of Acacia aulacocarpa was 0.687 a-1,and the estimated time for decomposition of 50%and 95%was 1.009 a and 4.361 a respectively.The decomposition coefficient of litter of Pinuselliottii was 0.579 a-1,and the estimated time for decomposition of 50%and 95%was 1.680 a and 4.937 a respectively.The decomposition coefficient of litterfall branch of Casuarina equisetifolia was 0.801 a-1,and the estimated time for decomposition of 50%and 95%was 0.865 a and 3.740 a respectively.The decomposition coefficient of litter of Eucalyptus urophylla x E.grandis was 0.897 a-1,and the estimated time for decomposition of 50%and 95%was 0.773 a and 3.340 a respectively.