| birch (Betula alnoides Buch.-Ham. ex D. Don) belongs to the Betulaceae, strong positive broad-leaved trees, natural distribution in the northeast of Burma, India Peninsula, India Peninsula countries and southwest china. With fast growth, strong adaptability, straight trunk, excellent material, birch is a valuable timber tree species. In this study,12year old Betula alnoides plantation (20m*20m, triplicate) of Guangxi Gaofeng forestry farm were selected, and the biomass, nutrient content and the C&N allocation pattern were systematically studied, which provided the scientific management and technical support for Betula alnoides plantation.the research results showed as:(1) Stand growth characteristics:12year old Betula alnoidesplantation tree height, DBH and individual wood volume were21.3m,18.5cm,0.28892m3, respectively; the maximum annual increment of tree height in the five and eighth year peak, DBH were in the two year peak, individual volume in the eleventh years.(2) Stand biomass, biomass productivity:the biomass of12years in various organs of Betula alnoides plantation were as the order of:trunk> Branch> root> bark> leaves; the average annual productivity of9.981·hm-2·a-1.(3) Nutrient content,accumulation and distribution:The nutrient content of tree layer were as the order of:leaf> bark> Branch> bark> root> root> root> stem> root thick root; nutrient elements as the order of:N>Ca>K>P>Mg. Contents of litter layer of nutrient elements in the order:N>Ca>K>Mg>P. Compared with the nutrient elements in various organs of tree layer, the majority of the content of nutrient elements in litter layer was higher than that of other nutrient elements.The12year old Betula alnoides plantation of tree layer of nutrient elements N, P, K, Ca, Mg accumulation sum to955.51kg·hm-2, annual net accumulation of79.64kg·hm-2·a-1; litter nutrient accumulation was81.44kg·hm-2. per It dry matter accumulation of Betula alnoides plantation required for7.98kg nutrient of N, P, K, Ca, Mg. Nutrient use efficiency of Betula alnoides was the highest in P, followed by Mg, the lowest as N.(4) Carbon and nitrogen storage allocation pattern:between the average carbon content ranging from470.76-513.44g·kg-1. The average nitrogen content between1.76-17.40g· kg-1. All organs of C/N ratio, the maximum in tree trunks, minimum in leaves, showed that the C/N ratio of aged organs was generally larger than in young organs. The carbon content of shrub grass layer (449.90g·kg-1) was slightly lower than that of the litter layer (476.96g· kg-1). While the nitrogen content of shrub grass layer (15.00g kg-1) is higher than that of litter layer (16.67g kg-1).The carbon and nitrogen content decreased with the increase of soil depth, the highest in0-20cm, soil carbon and nitrogen content in the layers of0-20cm were16.46g·kg-1and1.24g·kg-1, respectively.The ecosystem carbon reserves of the12year old Betula alnoides plantation were157.08t.hm-2, total nitrogen reserves as9.81t·hm-2. The annual net production was9.997t· hm-2·a-1, annual net carbon sequestration4.871t·hm-2·a-1, the net amount of nitrogen fixation of34.714kg·hm-2·a-1. |
PDF Full Text Request