| For a long time,the main species of afforestation in southern China are mostly Chinese fir and Pinus massoniana.The management of large area pure plantation of this two species causes serious problems,such as unitary tree species,simple stand structure,far-flung plant diseases and insect pests and decline of soil fertility,which seriously affected the growth of plantation and sustainable management.Therefore,finding other good tree species to an improve the tree species composition of the current plantation in South China has become an important issue to be solved urgently in forestry production.Taiwania flousiana Gaussen is an evergreen tree of Taiwania fir genus,with tall tree,fast growth and high yield.It is one of the better plantation species to replace the Chinese fir plantation.However,due to the lack of domestic research on the artificial cultivation of Taiwania flousiana,especially lake of studies on the environmental factors that affect the growth of Taiwania flousiana plantation,it is difficult to guide the artificial production of Taiwania flousiana forest management.In view of this,on the basis of the 34-year preliminary study of Taiwania flousiana plantation established by Youxi State-owned forest farm in Fujian province in 1983,we selected 3 different levels of Taiwania flousiana plantation(downhill,mid-slope and uphill)with 20mx20m standard,a total of nine standard.The effects of slope position on productivity and ecological function of Taiwania flousiana plantation were studied by comprehensively investigating the growth,biomass,undergrowth vegetation,water conservation and soil fertility function.The main findings are as follows:1.The productivity of the plantations of Tiwania fousiana had a great difference in different slopes.The DBH,the tree height,the volume of individual tree and the growth of the stand showed the characteristics of downhill>middle slope>uphill,and the difference between different slope positions reached very significant level(p<0.01).The mean DBH of in downhill was 128.1%and 164.8%of the mid-slope and uphill respectively;the average tree height was 138.0%and 154.8%of the mid-slope and uphill respectively;the average single plant volume was 210.1%and 366.4%of the mid-slope and uphill respectively.The stand volume was 188.4%and 296.4%of the mid-slope and uphill respectively.2.The DBH,tree height and volume growth of Taiwania flousiana plantation showed the same pattern under different slope positions.The average annual growth of DBH,tree height and volume showed downhill>middle slope>uphill.At downhill slope,the tree height increased quickly with an average annual growth rate of 0.65m,and researched the maximum in the 10th year and the average growth rate reached the maximum in the 14th year.The DBH and volume increased rapidly at the later stage,the growth volume was 0.91cm,and annual growth rate maintained aa high level during the period of 15-20 years.The average annual volume growth is 0.0212m3,and annual growth rate maintained a high level during 11-25 years.The average annual growth of tree height at middle slope was 0.48m,the average annual growth of DBH was 0.71cm,and the average annual volume growth was 0.0102m3.The tree height and DBH at uphill slope growth slowly at late growth stage,and the annual growth of volume is also low.3.The biomass of Taiwania flousiana plantation showed a great difference under different slope positions,which showed that downhill slope>mid-slope>uphill slope.The individual biomass at the downhill slope is respectively 182.5%and 255.2%of the mid-slope and uphill slope,which performed a significant difference(p<0.01)among different slopes.The stand biomass at downhill slope is respectively 163.8%and 206.5%of the mid-slope and uphill slope(p<0.01).4.The biomass of undergrowth vegetation of the Taiwania flousiana plantations in different slopes showed uphill slope>mid-slope>downhill slope,but the differences were small.The biomass of shrub layer at all levels showed uphill uphill slope>mid-slope>downhill slope,and the difference among different slopes did not reach significant level.The biomass of herbaceous layer showed uphill slope>mid-slope>downhill slope(p<0.05).The biomass of the litter layer shows downhill slope>mid-slope>uphill slope,and there were significant differences between different slope positions(p<0.05).5.There are differences in the water conservation functions of Taiwania flousiana plantations in different slope positions,which was downhill slope>mid-slope>uphill slope.The downhill slope was respectively 108.3%and 122.7%of the mid-slope and uphill slope.The arborous layer showed downhill slope>mid-slope>uphill slope,the undergrowth vegetation layer showed uphill slope>mid-slope>downhill slope,litter layer showed downhill slope>mid-slope>uphill slope.The soil layer showed downhill slope>mid-slope>uphill slope,in which the water-holding capacity of the soil layers in different slope positions accounted for more than 90%of the total water holding capacity.6.The soil fertility of the Taiwania flousiana plantations in different slopes was quite different,showed downhill slope>mid-slope>uphill slope.In the 0-20cm layer,the more than 0.25cm aggregates showed the downhill slope are respectively 102.8%and 105.7%of the uphill and mid-slopes.The total soil porosity of the downhill slope was respectively 108.8%and 120.1%of the mid-slope and uphill slope.The maximum water holding capacity of the downhill slope was respectively 112.9%and 132.7%of the mid-slope and uphill slope.The soil total N content in downhill slope is respectively 108.3%and 116.7%of the mid-slope and uphill slope.The soil total P content in downhill slope is respectively 117.0%and 130.9%of the mid-slope and uphill slope.The soil total K content in downhill slope is respectively 108.6%and 117.4%of the mid-slope and uphill slope.In conclusion,the slope position had a significant effect on the productivity and ecological function of the 34-year Taiwania flousiana plantation.The productivity and ecological function showed the following aspects:downhill slope>mid-slope>uphill slope,and there is an obvious difference between the downhill slope and the middle and uphill slope,while small difference between the middle and the uphill slope.Therefore,the afforestation of Taiwania flousiana plantation should choose in mid-slope and downhill slope,which will showed higher growth rate,stand biomass,water conservation and soil fertilization function. |
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