| Application of organic and inorganic fertilizers and understory removal are important plantation managements,which are beneficial for prompting the stand productivity.The abundance and diversity of soil arthropods can reflect changes in soil quality.However,the extent to which intensive forest management serves to alter soil arthropod communities remains elusive.In this study,we examined the effect of applying organic(two levels: OM1,OM2),inorganic fertilizer(two levels: NPK1,NPK2)and removing understory vegetation on the community abundance,diversity index(richness,evenness and Shannon's index)and assemblage composition of litter and soil dwelling fauna across three aged poplar plantations(5-,10-and 21-yr-old)during one year four sampling dates(March,June,September and December)in the coastal area of Northern Jiangsu Province,China.Results were as follows:1.The dominant soil fauna groups were Oribatida and Prostigmata mites in the poplar plantations.At litterfloor level: the total abundance and diversity index of soil fauna increased with the stand development.At soil level: diversity index of soil fauna increased with stand development,while soil fauna abundance increased from 5-yr to 10-yr,and kept the same in 21-yr-old age.The total abundance of soil fauna was significantly affected by stand ages and sampling date,and their interactions.The highest total abundance was in June.Total abundance showed strong age-dependent in September and December,and was higher in 10-yr and 21-yr-old,respectively.At soil level: total abundance was the highest in the 10-yr-old stands and the lowest in the 5-yr-old stands,and was higher in June and September,than December and March.Total abundance showed strong age-dependent trends in June and September;however,not in March or December.The vertical distribution was consistent,and which 0-10 cm was higher than in the 10-20 cm soil.2.At litterfloor level,fertilizer treatment,stand age and their interaction had significant effect on soil faunal abundance,order evenness and Shannon's index.Compared with the control treatment,fertilizer application increased the total abundance of soil fauna.Total abundance was also increased with stand development.Shannon's index was increased in 5-yr and 10-yr-old age with fertilizer application,while was decreased in 21-yr-old age.At soil level,fertilizer application did not change the trend of total abundance among stand ages.The highest was still in 10-yr-old age.Fertilizer treatment and stand age had significant effect on the soil fauna abundance,order richness,order evenness and Shannon's index.Compared with the control treatment,fertilizer treatment increased the total abundance except the low dose of treatments of organic and inorganic fertilizer in 5-yr-old age.Fertilizer application decreased the evenness in the 21-yr-old age stand,which may be associated with the abundance of Prostigmatid and Oribaitd.Changes in soil fauna were strongly associated with changes in microbial biomass carbon,available phosphorus and potassium.Our findings suggest that the responses of soil fauna to fertilizer may be mediated through the fertilization effects on soil nutrient availability.3.Understory removal had no significant effect on community abundance,order abundance,diversity and community composition,but depended on stand age and sampling time.It had significant interaction with sampling time on the community abundance and evenness.Compared with the control treatment,understory removal strongly decreased total faunal abundance in December in the 5-yr-old age.But understory removal increased the total abundance in March in the 21-yr-old age stand.Understory removal decreased the evenness index in 21-yr-old age in March due to increased abundance of dominant groups.These results demonstrated that forest management can impact poplar plantation soil fauna community,but depend on stand age.Our study suggests that(1)the lowest abundance of soil fauna was in 5-yr-old age.(2)Compared with the control treatment,high dose treatments of organic and inorganic fertilizer increased the soil fauna abundance in 5-yr-old age.Both organic and inorganic fertilizer treatment can increase the total abundance in 10 and 21-yr-old stands,and was higher with organic fertilizer treatment.(3)understory removal had no significant influence on soil fauna community abundance and diversity.Our results suggested that organic fertilizer application is a preferable management practice in order to elevate the abundance of soil arthropods while promoting poplar plantation productivity. |
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