Allelopathic Effects Of Understory Medicinal Plants On Conifer Litters Decomposition In Qinling Mountains

Planting medicinal plants under the forests can make full use of space and enhance the economic income,with avoiding the damage of the pure forest structure.However,leachate from understory medicinal plants,which enriched in secondary metabolites,were reported to be able to affect the soil environment and soil microbial activity,which may inhibit the forest litter decomposition and soil enzymatic activity.Thus,it is important to check out whether or not this phenomenon exists to choose understory medicinal plants.In this paper,five typical forest species of Pinus tabulaeformis,Platycladus orientalis,Pinus armandii,Larix gmelinii,Picea asperata and 9 species of common medicinal plants in Qinling area were taken as objects,the litter decomposition experiment was carried out by spraying the leachate(water-extraction solution)from the stems and leaves of the medicinal materials,to study the effects of leachate on forests litter decomposition,nutrient release and soil enzymatic activities.The consequence turned out to be:(1)The leachates of Taraxacum mongolicum,Corydalis bungeana,Mentha haplocalyx,Houttuynia cordata,Lonicera japonica and Nepeta cataria made significant effect to the litter of Pinus tabulaeformis.They all significantly prolonged the turn-over period of the litter and significantly inhibited the general nutrient(including C,N,P,K,Cu,Zn and Mn)releasing,except that the leachate of Lonicera japonica showed no significant effect on N releasing,the leachate of Nepeta cataria show no significant effect on N and P releasing.The leachates of Taraxacum mongolicum,Corydalis bungeana,Mentha haplocalyx,Houttuynia cordata and Lonicera japonica significantly inhibited the activity of polyphenol oxidase,the leachates of Lonicera japonica and Nepeta cataria significantly inhibited the activity of carboxymethyl cellulose and β-glucosidase.(2)The leachates of Lonicera japonica,Nepeta cataria and Prunella vulgaris significantly inhibit the decomposition of litter of Platycladus orientalis.The leachates all significantly prolonged the turn-over period of the litter.Till the end of the experiment,the leachate of Lonicera japonica significantly inhibited the release of C,N,P,K,and it also inhibited the activity of polyphenol oxidase of the soil.The leachates of Nepeta cataria and Prunella vulgaris significantly inhibit the release of N,P,K,and the activity of the carboxymethyl cellulose and β-glucosidase of soil.(3)The leachates of Nepeta cataria and Gynostemma pentaphyllum significantly inhibitthe decomposition of litter of Pinus armandii and prolonged the time of the decomposition.The leachates significantly inhibited the release of C,N,K,Cu,Mn of the litter.Besides that,the leachates of the former have significant inhibition to the release of Zn.The two leachates significantly inhibited the activity of polyphenol oxidase and carboxymethyl cellulose.(4)The leachate of Houttuynia cordata significantly prolonged the half-life period and the turnover period,and inhibited the release of C,N,P,Cu,Zn,Mn,it also inhibited the activity of polyphenol oxidase and protease.The leachate of Houttuynia cordata significantly prolonged the half-life period and the turnover period,inhibited the release of P,Cu and inhibited the activity of polyphenol oxidase.(5)The leachates of Houttuynia cordata,Nepeta cataria and Prunella vulgaris significantly prolonged the turnover period of the decomposition of the litter of Picea asperata.The leachate of Houttuynia cordata significantly inhibited the release of K and the activity of polyphenol oxidase and protease.The leachate of Nepeta cataria inhibited the release of P,Cu and the activity of polyphenol oxidase and carboxymethyl cellulose.The leachate of Prunella vulgaris significantly inhibited the release of C,P,Cu and the activity of carboxymethyl cellulose.As the result presented,different coniferous trees had various reaction to different treatment of the leachates of medicinal plants,which may have negative influence to the litter decomposition.As a conclusion,the typical medicinal plants mentioned above are not recommended to plant under the special coniferous forest.