Study On The Function Group Of Plant And The Structure Complexity Of Different Foresrt Communities

Currently,Eucalyptus plantation is developing fastly at a large scale in our country.The ecosystem of Eucalyptus plantation and the problem of persistent management have become an academic and social concern. We set three sort of plots,including E.grandis×E.urophylla plantation, open pinus massoniana forest and secondary mountain rain forest,in south Qinzhou,Guangxi in this paper.The variety of the structure complexity in different forest communities,the function group of plant were studied by using the index signs of the important value,Species richness,diversity,biomass,leaf area index,life form spectrum and life size spectrum etc.The Eucalyptus plantation's biological integrity was evaluated.The results were as follows:(1)On average of 100m~2 covariances, the numbers of understory plant species in the secondary mountain rain forest was 33.53±7.16,while in the open pinus massoniana forest was 20.22±3.30.The numbers of understory plant species in Eucalyptus plantation was 27.00±4.42 on average of 100m~2 covariances,which was 29.00%smaller than that in the secondary mountain rain forest and 33.53%larger than that in the open pinus massoniana.The index of Shannon-Wiener was 2.54±0.35 in the secondary mountain rain forest and 0.40±0.27 in the open pinus massoniana forest.The index was 0.85±0.47 in the Eucalyptus plantation.The index mentioned above reduced 198.82%and raised 112.50%compared to the secondary mountain rain forest and the open pinus massoniana forest.The evenness index was 0.72±0.08 in the secondary mountain rain forest,and was 0.13±0.08 in the open pinus massoniana forest.In the Eucalyptus plantation was 0.26±0.14,its evenness index reduced 176.92%and raised 100.00%compared to the other two forests.(2)The dominant species composition of shrub layer and herb layer plants has significantly changed.The important value of Alyxia sinensis and Osmanthus didymopetalus in seconday mountain rain forest were 41.11 and 35.17 which was the biggest two in the shrub layer.The important value of Baeckea frutescens and Rhodomyrtus tomentosa which were the dominant species in the open pinus massoniana forest were 96.16 and 48.97.The dominant species of herb layer plants in the Eucalyptus plantation were Phyllanthus reticulata and Rhodomyrtus tomentosa,their important value were 67.21 and 29.70.(3)The biomass of secondary mountain rain forest was obviously higher than the other two kinds of forest communities,it was 1.5 times more than the Eucalyptus plantation and 64.06 times more than the open pinus massoniana.However,the understory plants biomass of open pinus massoniana was higher than the one of the Eucalyptus plantation.(4)The compositional proportion of plant growth form in different forest communities made comparatively large changes.The main compositional proportion of plant growth form was trees in the secondary mountain rain forest,but to the other two forest communities,it is shrub plant;the high buds plants was absolute predominance for the compositional proportion of plant life form in three different forest communities,but the proportion of high buds plant in plant species changed little;among these three forest communities, medium-sized leaf plant shared a main position,the compositional of leaf scale spectrum transit from medium-sized leaf＞small scaled leaf＞large leaf＞miniature leaf for secondary mountain rain forest and Eucalyptus plantation to small scaled leaf＞medium sized leaf＞miniature leaf＞large leaf＞scale type leaf for open pinus massoniana.(5)Compared to the secondary mountain rain.forest,biological integrity of open pinus massoniana's belonged to the not complete grade(classⅣ)and Eucalyptus plantation's biological integrity belonged to the basic complete grade(classⅢ);In comparison with open pinus massoniana,the Eucalyptus plantation' s biological integrity is very complete(classⅠ). (6)The complexity of different forest community structure and variability of plant functional group structure were influenced by both of the environmental conditions and human element interference.