| Betula alnoides is a fast-growing and precious tree species,mainly distributed in tropical and subtropical regions of China.It can produce more value for the ecological environment and social economy.It is the main tree species for water conservation in the forest areas of southwest China.In addition,it has a fast growth speed and excellent wood properties.At present,the cultivated area of B.alnoides plantations in Southwest China of Dehong Prefecture has been gradually expanded.However,due to the lack of studies on the growth rules,leaf and soil nutrient status of the plantations,the quality and efficiency of B.alnoides plantations in this region have been restricted to some extent.Therefore,this study investigated the growth rules of tree height,DBH(diameter breast height),volume and leaf and soil nutrient levels of B.alnoides plantations in Dehong Prefterecture,providing certain theoretical basis and practical guidance for improving the quality of B.alnoides plantations in Dehong Prefecture and even similar areas.The main results of this study were as followed:(1)The growth rules of volume,DBH and height of B.alnoides plantations in Dehong Prefecture were summarized.From the general trend of change,the growth curves of tree height,DBH and volume of B.alnoides plantation under high,middle and low stand sites were similar.The heights of tree at low,middle and high sites were 24.7m,28.6m and 32.3m,the total growth of DBH was 23.32 cm,24.37 cm and 30.95 cm,and the total growth of volume was 0.485m3,0.574m3 and 0.949m3.The higher the site index,the better the tree height,DBH and volume growth.The rapid growth periods of height,DBH and volume were 1～5a,1～6a and 1～10a.The timber volume did not intersect with the average growth at 21 a in successive years,that is,the timber volume did not reach the quantitative maturity age at 21 a.(2)The leaf nutritional of B.alnoides plantation in Dehong Prefecture was diagnosed.The optimal contents of N,P,K,Ca and Mg in the leaves of B.alnoides plantation were7.78±1.76g/kg,1.07±0.24g/kg,8.07±1.59g/kg,8.88±2.11g/kg,2.98±0.95g/kg.The concentration ratios of N,P and K were N/P=7.67±2.70g/kg,N/K=0.99±0.26g/kg and P/K=0.14±0.05g/kg.The order of fertilizer requirement of low,middle and high yield plots of B.alnoides plantations was Mg > Ca > K > N > P,Mg > Ca > K > P > N,and Mg > Ca > K >P > N.The most scarce elements are Mg and Ca,followed by K and P,and N is the least scarce.The optimal nutrient ranges of N,P,K,Ca and Mg in B.alnoides plantation were10.13-5.43 g/kg,1.39-0.75 g/kg,10.19-5.95 g/kg,11.69-6.07 g/kg and 4.25-1.71 g/kg.(3)The soil nutrient of B.alnoides in Dehong Prefecture of Yunnan Province was evaluated.The variation of available P in the soil of B.alnoides plot was the strongest,followed by exchangable Ca and Mg.The soil of B.alnoides plantation sample plot in Southwest Dehong Prefecture was mostly acid soil.Soil organic matter,alkali-hydrolyzable N,total N,total K,available K content is sufficient,available P,exchangeable Mg content is insufficient.ECa,high-yield site with low content of EMg,there were significant differences between the middle site,TN,TK content site with medium and low yield significant difference between high site,the rest of the element content in low,medium and high yield were significant differences between site,different site of B.alnoides plantation forest land soil nutrient content comparison results verify the accuracy of the classification of the site by site fares.Soil organic matter content was the main source of N and K elements in leaves.The average annual growth of tree height,DBH and volume was significantly positively correlated with leaf total K content,leaf total K content,soil organic matter content,soil available K content,and leaf total K content,soil organic matter content and available K content. |
