| Tree species interact with soil biota to impact soil organic carbon(C)pools,but it is unclear how this interaction is shaped by various ecological factors.So we con-ducted field surveys in Fujian province of Xiayang forest farm(26°48'N,117°58 'E),Xiqin forestry farm(26°56N,118°11'E),Xiamen Tingxi forest farm(24°49'N,118°07'E)on the subtropical of China.The forest soils are acidic red soil.We estab-lished a sampling plot(20 m×20 m)in each of thirteen different species of the Ex-perimental Forest.The plots were located on relative forest floors and separated by 100 m.Forests in the plots were dominated by Natural forest,Phyllostachys heterocy-cla,Pinus elliottii,Fokienia hodginsii,Cunninghamia lanceolata,Acacia confuse,Acacia mangium,Mytilaria laosensis,Michelia maclurei,Phoebe bournei,Schi-ma superba,Castanopsis kawakamii,Castanopsis fissa.At the same time,this study were conducted in Changle Dahe State-owned Protection Froest Farm(119°68'E,25°96'N)and Dongshan County Froest Farm(23°40'N?117°18'E)in Fujian province of subtropical China.We selected Natural forest,Eucalyptus,Pinus elliottii,Aula coarpa,Casuarina equisetifolia.The forest soils are aeolian soil.We established a sampling plot(20 m×20 m)in each different species of the experimental forest.The goal of this study is to evaluate how species affect soil quality,including pH,ex-changeable calcium concentration,exchangeable magnesium concentration,Cations Exchangeable Capacity(CEC),Base Saturation(BS),organic carbon,and nitrogen,soil microbial community and structure,and to examine the magnitude of these changes regionally where species are high.We also examine potential mechanisms to maintain long-term productivity.(1)There were significant differences in Ca content of different tree species of litter leaves.At acidic red soil,Ca content of litter leaves was 0.95-8.53 g/kg,the or-der was as follows:Michelia macclurei>Natural forest>Phyllostachys pubescens>Cunninghamia lanceolata>Phoebe bournei>Castanopsis kawakamii>Mytilaria laosensis>Fokienia hodginsii>Castanopsis fissa>Acacia confusa>Schima su-perba>Acacia mangium>Pinus elliottii.In coastal sandy land,Ca content of litter leaves was 2.4-3 1.8 g/kg,the order was as follows:Natural forest? Casuarina equi-setifolia>Eucalyptus>Aula coarpa>Pinus elliottii.(2)There were significant differences in Mg content of different tree species of litter leaves.On acidic red soil,Mg content of litter leaves was 0.63-1.70 g/kg,the order was as follows:Mytilaria laosensis>Fokienia hodginsii>Natural forest>Schima superba>Michelia macclurei>Acacia confusa>Cunninghamia lanceola-ta>Castanopsis kawakamii>Acacia mangium>Castanopsis fissa>Phoe-be bournei>Phyllostachys heterocycla>Pinus elliottii.In coastal sandy land,Mg content of litter leaves was 1.4-3.6 g·kg-1,the order was as follows:Natural forest>A ula coarpa>Eucalyptus>Casuarina equisetifolia>Pinus elliottii.(3)There were differences in soil physical and chemical properties of different forest types.The soil pH of different forest types on red soil was between 4.25-4.76,while at coastal sandy land which was 5.0-6.1.CEC varied from 9.5 nmol·kg-1 to 21.0 nmol·kg-1 on red soil,Castanopsis fissa was the highest,Acacia mangium was the lowest,CEC varied from 1.5 nmol·kg-1 to 4.5 nmol·kg-1 on coastal sandy land,which Natural forest was the highest,Casuarina equisetifolia was the lowes.Soil ex-changeable Ca2+on red soil heterocycla plantation was the highest,the lowest was Mytilaria laosensis plantation,on coastal sandy land the highest in Natural forest,Aula coarpa plantation was the lowest;Soil exchangeable Mg2+on the red soil Natural forest was the highest,and the lowest in Acacia mangata,on the coastal sandy land the highest in Natural forest,and the lowest in Casuarina equiseti-folia;The base saturation(BS)of soil was 6.3-23.2%on red soil area,the highest BS was Phyllostachys heterocycla plantation,the lowest in the plantation of Castanopsis fissa,and the BS of different forest types on coastal sandy land was 77.8-91.4%,which the highest in Aula coarpa plantation,while natural forest soil was the lowest.(4)Not only on red soil the soil microbial biomass and phospholipid fatty acid in broadleaved plantations was higher than in coniferous plantations but also on coastal sandy land.(5)The relationship between leaf nutrient,stoichiometry of nutrients and soil physical-chemical properties.On red soil area the relationship between Mn of litter leaves and soil properties were not significant and there was a significant positive correlation between Ca of litter leaves and soil properties,such as pH,exchangeable Ca,exchangeable Mg,BS,however,cellulose/N and lignin/N of litter leaves were significantly negatively correlated with soil physical-chemical properties.On coastal sandy land the rusults were similar to which were on red soil area,Ca,Mg of litter leaves of different tree species had a significantly positive relationship with soil phys-ical-chemical properties,while carbon,cellulose/N ratio,lignin/N ratio of litter leaves were significantly negatively correlated with soil physical-chemical properties,(6)The Characteristics of litter leaf greatly affected soil microbial community structure.On red soil region,C?N?C/N?N/P?Mg?Mn?cellulose/N and lignin/N of different litter leaves had significantly relationship with gram positive bacteria(GP)and gram negative bacteria(GN),actinomycetes,fungi and arbuscular mycorrhizal fungi of soil microbial community structure.On coastal sandy land there were signif-icant correlation between C,N,Ca,Mg of litter leaves and soil microbial community structure,and the ralationship between fungus and Ca of litter leaves showed signifi-cantly positive correlation,which indicated that the litter leaves with high content of Ca could be more conducive to the decomposition of refractory matter.(7)The physical and chemical properties of soil have great effects on soil micro-bial community structure.the soil pH,C/N,ammonium nitrogen,mineral nitrogen,DOC,DON,available P and CEC are obviously correlated with soil microbial com-munity on red soil,while on coastal sandy land the soil properties had certain correla-tionship with soil microbial community structure except soil C/N ratio.(8)The contents of Ca and Mg of litter leaves were significantly positively cor-related with soil pH,which indicated that high Ca and Mg content in litter leaves of tree species can buffer soil acidification.At the same time,the ratio of fungi to bacte-ria in soil microbial community decreased with the increase of soil pH.Differences in litter Ca,Mg concentrations among tree species resulted in profound changes in soil acidity and fertility that were similar within and among tree groups.Tree species rich in Ca,Mg were associated with increased soil microbial abundance and diversity,as well as increased soil pH,exchangeable calcium,percent base saturation and forest floor turnover rate. |
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