Allelopathic Effects Of Broad-leaf Litter On Coniferous Litter Decomposition In Coniferous And Broadleaved Mixed Forest

Forest litter decomposition is the main source of forest nutrients and the key link of nutrient cycling,and it is of great significance for the stability and sustainable development of forest ecosystem.In the coniferous and broad-leaved mixed forests,whether the leaching of broad-leaved tree species will affect soil properties and thus inhibit or promote the decomposition of coniferous leaves is one of the basis for the selection of mixed forest coniferous and broadleaved vegetation development models.In this paper,10 kinds of artificial afforestation species of Qinling Mountainous Area of Shaanxi Province(including 5 kinds of coniferous species: Pinus tabulaeformis,Pinus armandii,larix kaempferi,Picea asperata,Platycladus orientalis and5 kinds of broadleaf species: Catalpa fargesii,Betula albosinensis,Acer truncatum,Eucommia ulmoides,Populus davidiana)were studied.The litter of the broadleaf species was extracted by water to simulate the leaching process of natural precipitation and to obtain the allelochemicals contained in them.Five kinds of coniferous litter and its decomposition medium(soil)were sprayed with different leaching materials(extracts),and a litter decomposition experiment was carried out for 6 months under the condition of room temperature and humidity,and the quality loss and nutrient release(C,N,P,K,Cu,Zn and Mn)of coniforus litter were simulated.The effects of decomposition rate and nutrient release of coniferous species were studied under the treatment of allelochemicals from different broadleaf litters.At the same time,the changes of enzyme activity(protease,polyphenol oxidase,phosphatase,?-glucosidase,cellulase and invertase)in the decomposition medium(soil)were tracked to explain the potential mechanism how the allelochemicals affects the litter decomposition processes.(1)When the P.tabulaeformis litter was mixed with that from the five broadleaved species,its decay rates were significantly improved by the treatments of the extracts from B.albosinensis,E.ulmoides and A.truncatum litters,while it was significantly inhibited by P.davidiana litter extracts.The release of N,K,Cu,Zn and Mn of P.tabulaeformis litter was significantly enhanced by the extracts of B.albosinensis,E.ulmoides and A.truncatum litter.The release of N,Cu,Zn and Mn was significantly enhanced by the extracted of E.ulmoides litter.The release of N,K,Cu and Mn was significantly enhanced by the extracts of A.truncatum litter.The release of C,N,and P was significantly inhibited by the extracts of P.davidiana litter.(2)When the P.orientalis litter was mixed with that from the five broadleaved species,its decay rates were significantly improved by the treatments of the extracts from P.davidiana litters,while it was significantly inhibited by B.albosinensis litter extracts.The release of N,P,Cu,Zn and Mn of P.orientalis litter was significantly enhanced by the extracts of B.albo-sinensis litter.The release of C,N,P and Cu was significantly enhanced by the extracted of P.davidiana litter.(3)When the P.armandii litter was mixed with that from the five broadleaved species,its decay rates were significantly improved by the treatments of the extracts from C.fargesii,P.davidiana and A.truncatum litters,while it nutrients release were significantly inhibited by all of 5 kinds of extracts of broadleaf litter.(4)When the L.kaempferi litter was mixed with that from the five broadleaved species,its decay rates were significantly improved by the treatments of the extracts from B.albo-sinensis,C.fargesii and E.ulmoides litters,and the decomposition rate of P.davidiana litter extract have an inhibitory effect.The release of C,N,P,Cu,Zn and Mn of L.kaempferi litter was significantly enhanced by the extracts of P.davidiana litter.The release of C,N,K and Zn were significantly enhanced by the extracted of B.albo-sinensis,C.fargesii and E.ulmoides litters and other broad-leaved species had no significant effect.(5)When the P.asperata litter was mixed with that from the five broadleaved species,its decay rates were significantly improved by the treatments of the extracts from C.fargesii,P.davidiana litters,while it was significantly inhibited by A.truncatum litter extracts.The release of C,P,Zn and Mn of P.asperata litter was significantly enhanced by the extracts of C.fargesii and P.davidiana litter.The release of C,P,K and Cu were significantly enhanced by the extracts of A.truncatum litters.Therefore,the combination of P.davidiana ×P.tabulaeformis,B.albosinensis ×P.orientalis,P.davidiana ×L.kaempferi,A.truncatum × P.asperata should be avoid to be used in the mixed afforestation of coniferous and broadleaved species.