| Litter is an important ecological interface linking aboveground and underground ecosystems,and its decomposition rate will directly affect soil fertility and productivity.Eucalyptus urophylla is a fast-growing tree species widely planted in South China.It was found that there were a lot of litter bark difficult to decompose in Eucalyptus urophylla plantations.How to promote rapid decomposition of Eucalyptus urophylla plantations has become an important part of efficient management of Eucalyptus urophylla plantations.A field study was conducted to determine litter quality and its nutrients'content of Eucalyptus bark at different stages of decomposition under different treatments.The purpose is to reveal the mechanism that how different types of litter,forest tands and nitrogen application rates affect the decomposition of Eucalyptus bark litter.The results can is expected to provide a theoretical basis for nutrient management and soil fertility maintenance of Eucalyptus plantation.The following is a summary of research conclusions:(1)Effects of litter mixing of other tree species on decomposition of Eucalyptus bark littertreatments including eucalyptus bark(DK),eucalyptus bark+Fujian cymbidium litter(ab),eucalyptus bark+Chinese fir litter(as),and eucalyptus bark+Fujian cymbidium litter+Chinese fir litter(asb)were set.It was found that the mixed decomposition of litter of other tree species significantly accelerated the decomposition of eucalyptus bark,and the effect of ab in promoting the decomposition of eucalyptus bark was stronger than that of as(P<0.05).The decomposition rate of C and N elements of ab,As and asb was significantly higher than that of DK(P<0.05),and the release rate of C and N elements of ab,as and asb was significantly higher than that of Eucalyptus bark decomposition(P<0.05)in the early stage,while the decomposition of P,lignin and cellulose was only slightly promoted bymixed litter.(2)The effects of mixed planting of eucalyptus and other species on the decomposition of eucalyptus bark litterEucalyptus bark litter alone was placed in artificial pure forest of eucalyptus(DK),eucalyptus and fokienia hodginsii mixed forests(AB),eucalyptus and cunninghamia lanceolata mixed forest(AS),eucalyptus and cunninghamia lanceolata and fokienia hodginsii three tree species mixed forests(ASB)four artificial forests to carry out decomposition experiment.The results showed that eucalyptusbark litter under the mixed decomposition can significantly promote the litter decomposition of eucalyptus skin(P<0.05).However,there was no significant difference between AB,AS and AB mixed forests.The enrichment of N was oberserved twice during the N release process of Ab,As and ASB,but no significant enrichment was found in DK.This indicated that stand mixing changed the N release pattern during the decomposition of eucalyptus bark.(3)Effects of nitrogen addition on decomposition of Eucalyptus barkThrough different addition treatments(including DK(0g/(m~2·a)),LN(5g/(m~2·a))and HN(10g/(m~2·a))of pure Eucalyptus bark litter placed under eucalyptus plantation,the results showed that high N significantly promoted the decomposition of eucalyptus bark,while low N had no significant effect on the decomposition of eucalyptus bark.In addition,both low and high nitrogen addition significantly inhibited the release of N and cellulose decomposition,but significantly promoted the decomposition of lignin(P<0.05).(4)Effects of mixed litters and tree species on the decomposition of eucalyptus barkTo conducted decomposition under different types of litter and forest stands,Eucalyptus bark litter solely was placedin eucalyptus artificial forests(DK),eucalyptus leather+fokienia hodginsii litter leaves placed on eucalyptus and fokienia hodginsii under mixed forest(ABab),eucalyptus leather+Chinese fir litter leaves placed on eucalyptus(ASas)under and cunninghamia lanceolata mixed forest,eucalyptus leather+fir fokienia hodginsii litter leaf litter leaves placed on eucalyptus and fir fokienia hodginsii and three tree species mixed forests(ASBasb)It was found that the dry weight residual rate after 540 days of decomposition was DK>ASas>ABab>ASBasb,and the decomposition rate of ASas,ASBasb and ABab was significantly higher than that of DK(P<0.05).And different types of litter+different stand significantly promoted the faded leather release of C and N elements of the decomposition,but inhibited the release of P(P<0.05),which suggests that different litter+mixed forest could significantly promote the litter decomposition of eucalyptus bark.Three kinds of litter mixed+mixed stimulative effect to three tree species better premoted the decomposition of eucalyptus bark than two kinds of litter mixed+mixed two tree species,and ABab is superior to ASab.(5)Differences in the effects of four treatments on the decomposition of eucalyptus barkThe mixed litter(DL),mixed tree species(DF),mixed litter(DN),mixed litter+mixed tree species(DLDF)were compared with the decomposed eucalyptus bark(DK)in eucalyptus forest.It was found that the C residual rate of eucalyptus litters after decomposition was significantly reduced by the mixed treatment of litters and stands,which was mainly influenced by the stoichiometry elements of eucalyptus litters,lignin and cellulose on nitrogen addition.In the N residual rate,DK-DL,DK-DLDF and DK-DF had significant differences,and DN increased the N residual rate.Compared with DK,DL significantly increased and DF significantly decreased in P residual rate.In other words,DL inhibited P release from eucalyptus bark,while DF promoted P release from eucalyptus bark.In conclusion,the effects of nitrogen addition on the decomposition of eucalyptus bark were the least among the four treatments.The promotion effect of litter mixing on the decomposition of eucalyptus bark was stronger than that of tree species mixing,and the promotion effect of litter+tree species mixing was the strongest.Further studies asscoiating litters with soil and decomposers are warranted to explore the response mechanism of litters to different treatments. |
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