桉树+粗果相思混交林模式及其效益

Study on the Benifit of Several Mixed Forest Models of Eucalyptus+Acacia crassicarpa

在各种混交模式中，桉树高生长以行间混交模式高于带状混交和纯林模式；胸径生长因受到密度效应作用，行间与带状混交模式均低于纯林模式；单株材积以纯林最高，行间混交次之，带状混交模式最小；林木树冠长度以混交模式大于纯林模式．各模式中粗果相思的生长，以雷林３３ 号行间混交模式的单株材积最大，达到０－１０２ １ ｍ３ ，粗果相思的群体蓄积为带状混交＜ 雷林３３ 号行间混交＜ ＭＬＡ（尾叶桉无性系） 行间混交；从粗果相思的群体保存率看，ＭＬＡ行间混交模式最高（９０－４％ ） ，远大于雷林３３ 号（４７－１ ％ ） 行间混交和ＭＬＡ的（４３－９％ ） 带状混交模式；从群体总产量来看，ＭＬＡ行间混交模式最高，其它模式依次为ＭＬＡ 纯林＞ 雷林３３ 号行间混交模式＞ ＭＬＡ带状混交模式＞ Ｗ５ 纯林模式＞ 雷林１ 号桉与大叶相思混交模式；从生物量测定结果看，纯林ＭＬＡ 单株生物量高于混交模式；群体生物量则以行间混交模式最高，达到７１ ４１４－１ ｋｇ／ｈｍ２ ，ＭＬＡ带状混交与纯林模式分别为３６ ５０１－４ ｋｇ／ｈｍ２ 和６３ ４３４－３ ｋｇ／ｈｍ２ ；各模式枯落物现存量以带状模式最高（９ ７９４．０ ｋｇ／ｈｍ２） ，ＭＬＡ行间混交模式次之（９ ２６２．０

Among every model,the height growth of MLA in the row mixed forest model is higher than that in the strip mixed forest model or in the pure forest model;affected by density effect,the DBH (diameter at breast height) of MLA in the row and strip mixed forest model are both lower than that in the pure forest model;the individual volume growth is model e >model a >model b ;the crown length of model a is higher than that of model e .About Acacia crassicarpa growth of every model,the individual volume-growth of model c is the highest (reachs to 0.102 1 m 3),and the growing stock is model b >modelc>model a ,and the preservation percentage is model a (90.4%)>model c (47.1%)>model b (43.9%) ;the total growing stock is model a >model e >model c >mode b >model f >model d ;the total biomass is model a (71 414.1 kg/hm 2)>model e (63 434.3 kg/hm 2)>model b (36 501.4 kg/hm 2);the present yield of litter fall also is b>a>e and its CON(content of nutrient) of 5 elements is N>Ca>Mg>K>P.For the total nutrient of litter fall,there is not significant difference between model a and model b ,but both model a and model b are higher(57.3%) than model e .The physical properties of soil are not promoted after Eucalyptus and Acacia crassicarpa are mixedly planted on the soil and there is a trend to become worse temporarily.Among the chemical properties of soil,pH increased a little in mixed plantation.The nutrient storage of 0～60 cm soil layer is higher than pure plantation’s and the di fference between them is not significant.This research indicates that the nutrient storage of the mixed forest is higher than that of pure plantation.Although its ratio of return by litter fall is relatively high,yet the uptake of the mixed forest is largely higher than that of pure plantation.If the manager neglects to protect the return nutrient by litter fall and to input artificial nutrient,it will be difficult to sustain the long term site productivity of the mixed forest in the future.