| In subtropical China,continuous cultivation of Cunninghamia lanceolata plantation will cause soil fertility degradation and biodiversity decline,so it is very important to consider replacing Cunninghamia lanceolata forest with natural secondary forest.Understanding the effect of natural and artificial restoration on forest litter production and litter decomposition are of great significance for studying the productivity and material cycle of subtropical forest ecosystems.Therefore,this study was conducted to compare the difference of forest litter production and litter decomposition between natural secondary forest and Cunninghamia lanceolata forest at different stand ages after unified logging,which represents natural and artificial restoration.The results showed that:(1)The annual litterfall production of natural secondary forest after natural restoration is 5.1±0.7—8.2±0.7 t·ha-1,which showed a trend of rising with the increase of stand age.The annual litterfall production of Cunninghamia lanceolata forest after artificial restoration is 2.0±0.2—3.1±0.2 t·ha-1,which showed a trend of rising with the increase of stand age,but not significantly.The linear mixed model found that the annual litterfall production and its constituents were significantly affected by the stand age and type of forest restoration.The litterfall production of natural secondary forest was significantly higher than Cunninghamia lanceolata forest in each recovery period,the natural restoration type is more conducive to the increase of litterfall productivity.(2)After natural and artificial restoration,the leaves dominated litter in each stand age,accounted for 48.2-69.3%and 45.3-51.6%respectively.Under the two restoration,the proportion of litter components was leaf>fruit>branch,and the proportion of litter components in natural secondary forest was significantly higher than Cunninghamia lanceolata forest.The patterns of monthly variation of litter production were multi-modal in natural secondary forest and Cunninghamia lanceolata forest,which were consistent with different stand age.The peak of litter production appeared in 1?3-4?7 and 9-10 month in natural secondary forest,and appeared in 1?5?7-8 and 11 month in Cunninghamia lanceolata forest.(3)After natural and artificial restoration,the litter decomposition rate increased with the increase of stand age,but not significantly.The litter mass remaining rate?C remaining rate?C/N?lignin and cellulose content of natural secondary forest were significantly smaller than Cunninghamia lanceolata forest.The litter decomposition rate of natural secondary forest was significantly faster than Cunninghamia lanceolata forest.The litter N remaining rate of Cunninghamia lanceolata forest increased significantly with the increase of stand age,and the litter C/N of early restoration decreased significantly.The correlation analysis showed that litter decomposition rate was significant negatively correlated with litter mass remaining rate,C remaining rate,C/N,lignin and cellulose.The redundancy analysis showed that lignin/N?Mineral N and lignin were important factors affecting changes in decomposition rate of litter.(4)After natural and artificial restoration,there was no obvious change trend of litter hydrolase activity with the increase of stand age.The activity of oxidase decreased with the increase of stand age,which had a significant effect on the activity of polyphenol oxidase.The forest restoration type had a significant effect on litter enzyme activity,the litter enzyme activitiy in natural secondary forest were significantly higher than Cunninghamia lanceolata forest.The correlation analysis showed that the activity of polyphenol oxidase(PPO)and peroxidase(PER)had significant or very significant negative correlation with C?N remaining rate.Cellulose had significant negative correlation with cellulolytic enzyme(CBH)and PER,lignin had significant negative correlation with PPO?PER.It is suggested that compared with artificial restoration,the natural restoration on forest was more beneficial to improve productivity of the litterfall,accelerated the decomposition and nutrient release of litter,was more beneficial to facilitate the survival and reproduction of soil and litter microorganisms,and improved the enzyme activity of microorganisms. |
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