Studied On The Above-ground Biomass And Productivity And Its Contents And Distribution Of Major Nutrient Elements Of The Short Rotation Eucalyptus Grandis Plantation

Using the design of quadratic common rotation including four factors and five levels, the basic model of efficiency was established between density, N, P, K and the above-ground biomass of single tree of five year old Eucalyptus Grandis plantation in Lai Fu Forest Managing Post of Yi Bin Gao county. Studied on the above-ground biomass and productivity and four regression models which include the parameter of biomass, diameter and height with equations w=a (D2H) b, w=a+bD+cD2, w=a+bD, w=aDb were built up. Dealt with the contents of major nutrient elements (N, P, K, Ca, Mg) in tree organs and the accumulated amount of nutrient elements. The results showed:1 The biomass of single tree and its distribution of above-ground tissues were arranged in the order of bole > bark > branch > leaf. The larger density, the smaller above-ground biomass of single tree. The tissue productivity was arranged in the order of bole > bark > branch > leaf. The results showed that it was beneficial to improve the productivity of stand with 1665~2070 trees/hm2 of the density .2 The basic model of efficiency was established between density, N, P, K and the above-ground biomass of single tree of five year old Eucalyptus Grandis:Y=15. 1441-3. 4049x1+1. 9547x2-1. 3514x4-0.4844x1x2-0. 6581x3x14+0.6053x12+0. 9340x22 By the testing, it conformed to the precision. So, the model might be used to estimate the above-ground biomass of single tree of five year, old Eucalyptus Grandis as long as the site factors were similar.3 By the principal effects analysis of density, N, P, K, when the other factors were within -2~+2 level limits, the relationship of density and the above-ground biomass of single tree was sharply negative.When the other factors were within lower level limits, a positive interaction existed between N fertilizer and P fertilizer, the positive interaction of N fertilizer was more than that of P fertilizer. When the other factors were within higher level limits, a negative interaction existed between N fertilizer and P fertilizer.When the other factors were within lower level limits, the interaction of K fertilizer and the other factors was not obvious. When the other factors were within higher level limits, the interaction of K fertilizer and the other factors was negative. The possible reason was that there were excess K fertilizer in the land soil which caused unbalanced between the K fertilizer and the other ones.4 When the other two factors were within 0 level limits, two factors curve equtations were established, the results showed: N fertilizer was beneficial to the above-ground biomass of single tree within it any level limits. The effect of P fertilizer was positive when the density was higher. The effect of K fertilizer was negative within the density any level limits. So the practical and first combination was low density, high N fertilizer, high P fertilizer, low K fertilizer.5 When the other two factors were within 0 level limits, two factors curve equtations were established, the results showed: The effect between N fertilizer and P fertilizer was positive. The effect between N fertilizer and K fertilizer was positive within N fertilizer or K fertilizer lower level limits, the effect between N fertilizer and K fertilizer was negative within N fertilizer or K fertilizer higher level limits. The effect between P fertilizer and K fertilizer was the same as that of between N fertilizer andK fertilizer.6 When the four factors of density, N ,P, K fertilizer were in the confidence limit of 95% , the combination high yield cultivated pattern was the following plantation density 1860—1935 trees/ hm2, N fertilizer 56 — 64 g/tree, P2O5 fertilizer 47—56 g/tree, K2O fertilizer 37~46 g/tree.7 The estimating precisions of four regression models which included the -parameter of biomass, diameter and height were over critical minimum. So it could be used to forecast the biomass of single tree and its distribution of above-ground tissues when culturing Eucalyptus grandis plantations. As to the practice, the equitation w=a+bD+cD2 was better than the others.8 the contents of major nutrient elements in tree organs were different. Their ranking was K (or Ca) >N> (or Mg) >P.9 With the increase of the density, the accumulated amount of nutrient elements of single tree decreased, the accumulated amount of nutrient elements of single tree in the lowest density was 1. 78 times to that of single tree in the highest one.10 The accumulated law of different nutrient elements was not influenced by the density, the order was: Ca > K > N > Mg > P. The total accumulated amount of nutrient elements in different tissues was influenced in some degree by the density. Excluding the density 1860 trees/ hm2, the ranking was bark > leaf > bole > root > branch, the other density stand' ranking was bark > bole > leaf > root > branch. The results were got for one time, which could only stand for the accumulated total amount of nutrient elements at that time.11 The total accumulated amount order of different nutrient elements in five densities was Ca > K> (N > Mg or Mg > N) > P. The impossible reason which resulted in most contents was Ca was easy to be fixed comparing with the other elements.12 With the increase of the density, the per year accumulated amountof nutrient elements increased, the percentage in bole was 18. 26%~21. 30%. The percentage of the total accumulated amount of nutrient elements in the bole was less than that in the branch and the bark as well as the leaf. On the contrary, the accumulation of the biomass in the bole was more than that in the other tissues, because the nutrient elements of leaf were produced and returned in the same year, when cutting up the forest and only making the bole be out from the stand, that is to say 78. 70%~81. 74% nutrient elements would be returned to the stand, so it was good to maintain the land capability of the stand.