Effects of nitrogen-fixing tree species Acacia mangium on particle size distribution and stability of soil aggregates in Eucalyptus grandis×urophylla plantations
Effects of nitrogen-fixing tree species Acacia mangium on particle size distribution and stability of soil aggregates in Eucalyptus grandis×urophylla plantations
Soil aggregates are the basic unit of soil structure.The stability of soil aggregates is an important indicator for evaluating soil structure and soil fertility.In order to explore the effects of Acacia mangium on particle size distribution and stability of soil aggregates of Eucalyptus grandis×urophylla plantations,we measured the distribution and stability of aggregates indicators such as mean weight diameter(MWD),geometric mean diameter(GMD),mass fractal dimension(Dm),water stable aggregates(WSA),percentage of aggregates destruction(PAD)and aggregates stability index(ASI)in the 0-10 cm and 10-20 cm soil layers by the dry sieving method and the wet sieving method,and a pure plantation of E.grandis×urophylla(PP)and a mixed plantation containing E.grandis×urophylla and Acacia mangium(nitrogen-fixing tree species)(MP)were selected as the research objects.The results were as follows:(1)Compared with PP,the soil physicochemical properties of MP were improved in varying degrees,especially soil pH,organic carbon(SOC)and total nitrogen(TN).(2)The particle size distribution of soil aggregates in MP was better than that of PP,and the differences mainly in the particle sizes of>2.00 mm and<0.25 mm,but both were dominated by large aggregates(>0.25 mm).Compared with PP,the mechanical stability of aggregates in MP only increased significantly at 0-10 cm soil layer,but the water stability of aggregates in MP increased significantly at 0-10 cm and 10-20 cm soil layer.The mechanical stability and water stability of soil aggregates tended to decrease with the deepening of soil layer.(3)Mantel analysis showed that the stability of aggregates was significantly correlated with pH,SOC,TN,TP,BD and SP,and the stability of aggregates had the strongest correlation with TN.RDA analysis indicated that TN was the most critical factor driving the variation of stability aggregates.Our findings suggest that nitrogen-fixing tree species A.mangium can significantly improve proportion of macroaggregates(>0.25 mm)and the stability of soil aggregates in Eucalyptus plantations.This study can provide a theoretical reference for soil and water conservation,soil nutrient management and sustainable management of Eucalyptus plantations in the South Asian tropics.
关键词
土壤团聚体/机械稳定性/水稳定性/桉树人工林/固氮树种
Key words
soil aggregates/mechanical stability/water stability/Eucalyptus plantations/nitrogen-fixing tree species
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