Effects Of Leachates From Medicinal Plants On Decomposition Of Litter Decomposition Of Broad-leaved Tree Species In Compound Forest-medicinal Plant System Of Qinling Mountains

Forest litter decomposition is an important factor affecting nutrient cycle and ecosystem stability.In compound system of forest-medicinal,leachate from understory medicinal plants enriched in plant secondary metabolites,which may inhibit the forest litter decomposition and soil enzyme activity.Thus,inspection whether or not exit this phenomenon is one important basis for choosing understory medicinal plants.In this paper,the sampling area in this experiment is the Houzhenzi Forest Farm of Zhouzhi County in the Qinling Mountains of Shaanxi,the typical five broad-leaved species(Betula albo-sinensis,Eucommia ulmoides,Populus purdomii,Catalpa fargesiiand Acer mono)in the Qinling Mountains and nine species of medicinal plants(Taraxacum mongolicum,Corydalis bungeana,Mentha haplocalyx,Houttuynia cordata,Asarum sieboldii,Lonicera japonica,Nepeta cataria,Gynostemma pentaphyllum and Prunella vulgaris)common in the area were cited as objects in the study,the decomposing bag method was used in the indoors litter decomposition experiment with constant temperature and humidity,a simulation experiment was carried out on litter decomposition by spraying leachate in water-extraction solution from stems and leaves of the medicinal plants.The experiment lasted for six months,during the experiment,leachate from the litter of medicinal plants was sprayed once every two weeks,and the decomposing bags were retrieved five times(in the first,second,third,fifth and sixth month after the start of the decomposition experiment),soil samples were collected three times(in the first,third and sixth month after the start of the decomposition experiment),to determine decomposition rate,nutrient release and soil enzyme activity,at the same time,GC-MS was used to analyze chemical substances in the medicinal plants leachate,to study effects of the leachates on litter decomposition,nutrient release and soil enzyme activity.The result showed that:For litter of B.albo-sinensis,turnover period and half-life was extended by 4.3 times and 76%,respectively,in the treatment using H.cordataleachate,turnover period and half-life was extended by 2.7timesand35%in the treatment using G.pentaphyllum leachate,half-life period was extended by 16%~63%in the treatment using T.mongolicum,C.bungeana,M.haplocalyx,A.sieboldii,L.japonica,N.cataria and P.vulgaris leachate,it means that leachate fromH.cordataandG.pentaphyllum all displayed significant inhibitory effects on the early and late period of litter decomposition,leachate fromother seven species only displayed significant inhibitory effects on the early period of litter decomposition;leachate from C.bungeana,H.cordata,G.pentaphyllum and P.vulgarisdisplayed strong inhibitory effects on nutrient release in litter decomposition;leachate from H.cordataandG.pentaphyllum all displayed significant inhibitory effects onseven kinds of soil enzyme activities in litter decomposition.It was suggested that the leachate fromH.cordataandG.pentaphyllum had significant inhibitory effects on the litter decomposition,nutrient release and soil enzymes activity of B.albo-sinensis,therefore,it is suggested that H.cordataandG.pentaphyllum should not be planted as understory in B.albo-sinensis forests,or interplanting density of these plants should be kept lower to reduce the inhibitory effects.For litter of E.ulmoides,turnover period and half-life was extended by 4.2 times and 1.7 times,respectively,in the treatment using H.cordataleachate,turnover period and half-life was extended by 9timesand98%,in the treatment using G.pentaphyllum leachate,it means that leachate fromH.cordataandG.pentaphyllum all displayed significant inhibitory effects on the early and late period of litter decomposition;leachate from T.mongolicum,H.cordata,A.sieboldiiandG.pentaphyllumdisplayed strong inhibitory effects on nutrient release in litter decomposition;leachate from H.cordataandG.pentaphyllum all displayed significant inhibitory effects onseven kinds of soil enzyme activities in litter decomposition.It was suggested that the leachate fromH.cordataandG.pentaphyllum had significant inhibitory effects on the litter decomposition,nutrient release and soil enzymes activity of E.ulmoides,therefore,it is suggested that H.cordataandG.pentaphyllum should not be planted as understory in E.ulmoides forests,or interplanting density of these plants should be kept lower to reduce the inhibitory effects.For litter of P.purdomii,turnover period and half-life was extended by 2.3 times and 29%,respectively,in the treatment using T.mongolicumleachate,turnover period and half-life was extended by 67%and23% in the treatment using M.haplocalyx leachate,turnover period and half-life was extended by 1.2 timesand34%in the treatment using H.cordata leachate,half-life period was extended by 21%in the treatment using L.japonicaleachate,turnover period was extended by 81% in the treatment using G.pentaphyllumleachate,turnover period and half-life was extended by 51%and43%in the treatment using P.vulgarisleachate,it means that leachate fromT.mongolicum,M.haplocalyx,H.cordataandP.vulgaris all displayed significant inhibitory effects on the early and late period of litter decomposition,leachate from L.japonica only displayed significant inhibitory effects on the early period of litter decomposition,leachate fromG.pentaphyllumonly displayed significant inhibitory effects on the late period of litter decomposition;leachate from T.mongolicum,M.haplocalyx,H.cordataand A.sieboldii displayed strong inhibitory effects on nutrient release in litter decomposition;leachate fromT.mongolicum,M.haplocalyx,H.cordataandP.vulgaris all displayed significant inhibitory effects onseven kinds of soil enzyme activities in litter decomposition.It was suggested that the leachate fromT.mongolicum,M.haplocalyxand H.cordata had significant inhibitory effects on the litter decomposition,nutrient release and soil enzymes activity of P.purdomii,therefore,it is suggested that T.mongolicum,M.haplocalyxand H.cordata should not be planted as understory in P.purdomii forests,or interplanting density of these plants should be kept lower to reduce the inhibitory effects.For litter of C.fargesii,turnover period and half-life was extended by 48% and 44%,respectively,in the treatment using M.haplocalyxleachate,half-life period was extended by 43%in the treatment using H.cordata leachate,turnover period was extended by 55% in the treatment using N.catarialeachate,turnover period and half-life was extended by 1.6 times and 54%in the treatment using G.pentaphyllum leachate,turnover period and half-life was extended by 2.7 times and27%in the treatment using P.vulgaris leachate,it means that leachate fromM.haplocalyx,G.pentaphyllumand P.vulgarisall displayed significant inhibitory effects on the early and late period of litter decomposition,leachate from H.cordata only displayed significant inhibitory effects on the early period of litter decomposition,leachate from N.catariaonly displayed significant inhibitory effects on the late period of litter decomposition;leachate from M.haplocalyx,H.cordata,A.sieboldii,G.pentaphyllum and P.vulgaris displayed strong inhibitory effects on nutrient release in litter decomposition;leachate fromM.haplocalyx,H.cordata,G.pentaphyllum and P.vulgarisdisplayed strong inhibitory effects onsoil enzyme activities in litter decomposition.It was suggested that the leachate fromM.haplocalyx,H.cordata,G.pentaphyllum and P.vulgaris had significant inhibitory effects on the litter decomposition,nutrient release and soil enzymes activity of C.fargesii,therefore,it is suggested that M.haplocalyx,H.cordata,G.pentaphyllum and P.vulgaris should not be planted as understory in C.fargesii forests,or interplanting density of these plants should be kept lower to reduce the inhibitory effects.For litter of A.mono,turnover period and half-life was reduced by 80%~88% and 48%~65%,respectively,in the treatment using leachate from all these nine species of medicinal plants,it means that none of leachate fromnine species of medicinal plantsdisplayed significant inhibitory effects on the early or late period of litter decomposition;leachate from C.bungeana,H.cordata,L.japonicaandN.cataria displayed inhibitory effects on nutrient release in litter decomposition;leachate fromall these nine species of medicinal plantsdisplayed inhibitory effects on soil enzyme activities in litter decomposition were weak.It was suggested that,in nine species of medicinal plants,none of leachate fromthem had significant inhibitory effects on the litter decomposition,nutrient release and soil enzymes activity of A.mono,therefore,it is suggested that T.mongolicum,C.bungeana,M.haplocalyx,H.cordata,A.sieboldii,L.japonica,N.cataria,G.pentaphyllum and P.vulgarisall could be planted as understory in A.monoforests.