Dynamics Characteristic Of Litterfall Production And Nutrient Of E.grandis × E.urophylla Plantation In Southwest Of Guangxi

Due to its adaptability,rapid growth and strong germination ability,Eucalyptus.grandis×E.urophylla become one of the most popular hybrid varieties(lines)of eucalyptus in South China.In order to understand the dynamics of litter composition and nutrient dynamics during the growth of Eucalyptus.grandis×E.urophylla plantation,it provides a scientific basis for rationally developing the management measures of Eucalyptus.grandis×E.urophylla plantation and promoting the sustainable management and development of Eucalyptus.grandis×E.urophylla plantation.This paper conducted a five-year localization monitoring and analysis of the 2-6 year old Eucalyptus.grandis×E.urophylla plantation in Ningming County,Guangxi.The research results are as follows:(1)After planted 2~6 years,the annual litter productions of E.grandis×E.urophylla plantation were 2332.6 kg/hm~2,3533.8 kg/hm~2,4011.6 kg/hm~2,3751.4 kg/hm~2?3458.0kg/hm~2,respectively.The litter components included leaves,branches,flowers and fruits.Among all the litter components,leaves litter production accounted for more than 49%of the whole litter production.The litter production of seasonal variation tendency was changed significantly,the seasonal variation tendency in sequence of autumn>summer>spring>winter.Different year monthly variation of leaves litter showed patterns of change,but the overall showing a bimodal pattern.The highest peak was appeared at July(589.2kg/hm~2),October(557.8 kg/hm~2),August(788.8 kg/hm~2),September(408.0 kg/hm~2)and September(450.6 kg/hm~2)during 2008 to 2012.(2)After planted 2~6 years,the annual five nutrient elements which including N,P,P,Ca and Mg return through leaves litter of E.grandis×E.urophylla plantation were 46.449 kg/hm~2,81.835 kg/hm~2,70.418 kg/hm~2,44.354 kg/hm~2,and 32.702 kg/hm~2,respectively.Ca was the highest nutrient return of each litter components and P was the lowest.The sequence of the five macro-elements return was Ca(125.361kg/hm~2)>N(95.123 kg/hm~2)>K(28.376 kg/hm~2)>Mg(22.557kg/hm~2)>P(4.340 kg/hm~2).(3)Compared with that before afforestation,,the soil bulk density of at 0-20 cm and 20-40 cm of 6-year-old E.grandis×E.urophylla plantation showed a decreasing trend,while the total soil porosity increased slightly,and the content of soil organic matter and main nutrients mostly increased.