| Pinus massoniana,important native coniferous tree specie in southern China,was one of the main afforestation tree species of timber forests in subtropical areas,with the characteristics of wide distribution range,fast growth,barren drought resistance and strong adaptability.In order to reveal the biological productivity and nutrient characteristics of the Pinus massoniana plantation,it provides a scientific basis for the management of the P.massoniana plantations.In this study,5,10 and 15-year-old P.massoniana plantations in Ningming County,Guangxi Province were taken as the research objects,the biomass,productivity,nutrient accumulation and annual net accumulation of P.massoniana plantations at different stand ages(5,10,15 and 20-year-old)were studied through sample plot investigation and biomass measurement.The main research results are as follows:(1)The average biomass of 5,10,and 15-year-old P.massoniana plantations is 22.56,67.78,and 122.70 kg/plant,and the biomass of tree layer was 34.07,93.54,and 162.16 t/hm~2,respectively.Among them the proportion of stem biomass raises with the increase of stand age,while leaves and branches has the opposite trend,and the proportion of roots and bark fluctuated little.(2)The net productivity of 5,10,and 15-year-old P.massoniana plantations were 6.81,9.35,and 10.81t/(hm~2·a),respectively.What was more,stem(2.64～6.09 t/(hm~2·a))has the fastest accumulation rate of different organs,followed by branches(1.96～2.31 t/(hm~2·a)),roots(0.79～1.29 t/(hm~2·a))and leaves(0.50～0.86 t),and the slowest was stem(0.58～0.92 t/(hm~2·a)).(3)Ten nutrient elements(N,P,K,Ca,Mg,Fe,Mn,Zn,Cu,B)in different organs of P.massoniana plantation at different ages were as follows from large to small:leaves,bark,branches,roots and dry wood.In addition,the content of macronutrient elements in different organs was highest in N,followed by K and Ca,and lowest in P and Mg.Micronutrient elements were the highest in Mn and Fe,followed by Zn and B,and Cuwas the lowest.(4)The accumulation of nutrient elements in 5-,10-,and 15-year-old P.massoniana plantation were 525.45,846.45,and 1149.33 kg/hm~2respectively,among which the tree layer were 454.39,739.71,and 1004.34 kg/hm~2respectively,and the shrub and herb layer was 40.36,57.96,and 75.13 kg/hm~2respectively.The litter layers were 30.70,48.78 and 69.86 kg/hm~2respectively.While the accumulation of micronutrients in stand was 9.70,25.91 and 41.15kg/hm~2,among which the accumulation of micronutrients in arbor layer were7.64,22.13 and 35.90 kg/hm~2respectively,and that in shrub and herb layer was1.00,1.50 and 2.04 kg/hm~2.The litter layer was 1.05 kg/hm~2,2.25 kg/hm2 and3.22 kg/hm~2respectively.(5)The annual net accumulation of macronutrients in tree layers of 5,10 and15-year-old P massoniana plantations were 90.87,73.95 and 69.00 kg/(hm~2·a),and the annual net accumulation of micronutrients were 1.53,2.21 and 2.39kg/(hm~2·a),among which branches,roots or dry wood have the largest the annual net accumulation,and the annual net accumulation of bark was the smallest.(6)5,10 and 15 P massoniana plantations need 13.34 kg of N,7.91 kg of P,7.91 kg of Ca and 6.38 kg of Mg,and 0.2243 kg of Fe,0.2442 kg of Cu,0.2215kg of Zn and B for each ton of dry matter accumulated.In conclusion,P.massoniana plantation was characterized by high biological productivity and rapid accumulation rate of nutrient elements.For this reason,fertilization should be carried out in forest land according to the soil nutrient level of forest land and the demand of nutrient elements for forest growth,so as to meet its growth and development needs and improve the biological productivity in the management process of P.massoniana plantation. |
