Study On The Nutrient And Enzyme Activity And Microorganism Property For The Soil Of Three Forests Types In Mountainous Region From Eastern Liaoning Province

There is growing concern about the problem of soil degradation in the artificial pure forest of Larch.To explore the difference and change regulation of soil under different silvicultural measures,three forest types of Larix olgensis forest?LF?and the mixed forest of Larix olgensis and Fraxinus mandschurica?MF?and the secondary forest?SF?from eastern Liaoning Province were selected.The item of the soil physical and chemical properties,enzyme activity,microorganism content,and the relationship between each other from the surface layer?0-10cm?,sub-surface?10-20 cm?and the under layer?20-30 cm?was investigated.Results mainly showed that:?1?The percentage of large macroaggregates decreased with the soil layer deepened,while the microaggregates increased.The large macroaggregates,ranged from 29.44%to 39.42%,display the sequence of SF>MF>LF,while the microaggregates ranged from 6.02%to 12.00%,changed with a contrary tendency.The soil pH value in average for Larch forest?LF?decreased by 5.4%and 4.5%for secondary forest?SF?and mixed forest?MF?,respectively.The soil of Larch plantation had presented the tendency of acidification phenomenon.In the surface,the contents of soil organic C,total N,microbial biomass C and the ratio of C to N were 41.16 g·kg^-1-61.52 g·kg^-1,4.15 g·kg^-1-5.59 g·kg^-1,5.11 g·kg^-1-9.06 g·kg^-1,9.91-11.00 with the sequence of SF>MF>LF,which indicated significant difference?P<0.05?.Meanwhile,they all decreased with the increasing of depth of soil layer.?2?Soil enzyme activities included catalase activity,urease activity,and invertase activity significantly decreased with the soil layer deepened?P<0.05?.And acid phosphatase activity shares the same tendency only without the significance.All of the 4 kind of enzyme have the same sequences of SF>MF>LF,especially in the surface it becomed significant?P<0.05?.Soil catalase activity,urease activity,acid phosphatase activity and invertase activity ranged of 45.64ml·g^-1·30min^-1-47.91ml·g^-1·30min^-1,1.82 mg·g^-1·d^-1-2.04 mg·g^-1·d^-1,1.39 mg·g^-1·d^-1-1.75mg·g^-1·d^-1 and 3.45 mg·g^-1·d^-1-5.55 mg·g^-1·d^-1,respectively.Besides,there were significant differences for soil enzyme activities among different soil layers of 0-10cm,10-20cm and 20-30cm,with the except of soil invertase activity.?3?There were significant?P<0.05?differences of soil microorganism among the soil layers.Soil microorganism mainly existed in the surface,among them,the content of bacteria ranged from 19.09 nmol·g-1 to 29.68 nmol·g-1,fungi from 2.47 nmol·g-1 to 3.71 nmol·g-1,and actinomycetes from 5.59 nmol·g-1 to 7.68 nmol·g-1.In the surface,the contents of bacteria and actinomycetes in the secondary forest significantly increased from that of larch plantation?P<0.05?.The ratio of bacteria to fungi?B/F?and of gram-positive bacteria and gram-negative bacteria?G+/G-?varied significantly with the forest type?P<0.05?.It indicated highly significant positive relationship between the total microbial content and the catalase activity?P<0.01?and invertase activity and significant positive relationship between soil microbial content,bacteria content and actinomycetes content and urease activity?P<0.05?.Avalible nitrogen was the most important factor of soil microorganism?P<0.01?and pH value,large macroaggregates,microaggregates,total phosphorus,the ratio of nitrogen and phosphorus were important factors of soil microorganism?P<0.05?.?4?There were 47 phyla,171 classes,326 orders,506 families,844 genera detected in the test.The dominant bacterial community,actinobacteria,proteobacteria,acidobacteria contain the relative abundance of 22.98%-37.67%,19.00%-32.85%,9.57%-16.53%,respectively.The relative abundance appeared the sequence of SF>MF>LF,and decrease when soil layer was deepened.The soil in the surface was far different from other layers.It indicated positive relationship between the total organic carbon,microbial biomass carbon,total nitrogen,available nitrogen and actinobacteria,proteobacteria while negative relationship between those nutrient content and acidobacteria.Total nitrogen was the most important factor of soil microorganism?P<0.01?and pH value,microaggregates are important factors of soil microorganism?P<0.05?.