| In recent years,with the large-scale promotion of eucalyptus plantations,especially the large-scale afforestation of single saplings of eucalyptus single tree species,the impact of farming,tending methods and multi-generational continuous management on the site conditions and ecological environment of forest land has become a society.The focus,especially the eucalyptus plantation,has been sustainable development for many generations.In this paper,the spatial and temporal sequences were combined to analyze the differences in growth characteristics,biomass and soil physical and chemical properties of eucalyptus plantations,second-generation forests and third-generation forests in Hengxian County,Guangxi,respectively.The growth of different eucalyptus trees was analyzed,the biomass of the forest was analyzed by the harvesting method,and the soil physicochemical properties of three different eucalyptus plantations were studied by soil profile method and laboratory analysis.The research results are as follows:(1)The average DBH of different generations of Eucalyptus forests is the largest in the 2nd generation forest(13.8cm),followed by the 1st generation forest(12.0cm),the 3rd generation forest minimum(11.3cm);the average tree height is the 2nd generation forest maximum(20.7)m,followed by 1 generation forest(18.1m),3 generation forest minimum(16.0m);output volume 2 generation forest highest(11.48m3k/mu),followed by 3 generation forest(8.51m3/mu),1 generation The forest is the smallest(8.31m3/mu);the successive cultivation of eucalyptus plantations has not experienced a decline.The coefficient of variation of DBH of different Eucalyptus plantations was between 0.205 and 0.246,among which the coefficient of variation of the second generation Eucalyptus plantation was the lowest(0.205),followed by the first generation forest(0.242),and finally the third generation forest(0.246).The coefficient of variation was negatively correlated with the average breast diameter of the stand.(2)The biomass of different eucalyptus plantations in 5a was:2nd generation bud(129.527t/hm~2)>3rd germination(110.741t/hm~2)>1 generation seedling(104.462t/hm~2).The total biomass of the 2nd generation sprouting forest and the 3rd generation sprouting forest increased by 22.99%and 6.01%,respectively,compared with the first generation planting forest.(3)The biomass distribution of different generations of eucalyptus plantations with right-level distribution showed a right-biased normal distribution.The diameter of the biomass peak was increased by 1 to 2 diameters than the average diameter of the forest,and the average breast diameter was above(including The average DBH)forest biomass accounted for 74.54-86.96%of the total biomass of the forest.(4)The total soil porosity of different eucalyptus plantations was 20.10?45.08%,the capillary porosity was 14.94?31.60%,and the non-capillary porosity was 6.08?15.00%.There is a significant.difference in soil non-capillary porosity between different generations of forest land,and non-capillary porosity increases with the increase of operational algebra.There is a significant difference in soil porosity in the vertical direction,which decreases with the increase of soil depth.(5)The maximum soil water holding capacity,capillary water holding capacity and minimum water holding capacity of different generations of eucalyptus plantations were 22.17?31.22%,14.32?18.74%,3.64-10.94%.The minimum water holding capacity of the soil is significantly different between different forest stands.The maximum soil water holding capacity,capillary water holding capacity and minimum water holding capacity were significantly different between different soil layers,and decreased with the increase of soil layer depth.The maximum water holding capacity difference is extremely significant,from 29.00%to 40%in the 0?20cm layer.19.38%of the 60 cm soil layer.(6)The contents of total nitrogen,total phosphorus and total potassium in different generations of eucalyptus plantations were 1.04?1.65g/kg,0.29?0.51g/kg,19.90?27.50g/kg,and soil total nitrogen,total phosphorus and total potassium in plantation forest.The content of soil is higher than that of budding forest;soil hydrolyzable nitrogen content(91.86?173.60mg/kg),available phosphorus content(0.35?0.5 lmg/kg)and available potassium content(47.96?101.12mg/kg)are obviously different,hydrolyzable nitrogen And the content of available potassium in plantation forest was significantly higher than that of 2nd and 3rd generation sprouting forest;copper content was 0.17?0.27mg/kg,zinc content was 0.69?1.73mg/kg,boron content was between 0.52?0.55mg/kg The addition of copper,zinc and boron to the special fertilizer of eucalyptus is the main reason for the stable or even enrichment of these three trace elements in the eucalyptus plantation.(7)The total nutrient reserves of 11 kinds of nutrients such as hydrolyzable nitrogen,available phosphorus,available potassium,calcium,magnesium,iron,copper,zinc,boron,manganese and sulfur in different generations of eucalyptus plantations were between 2,358.12 and 3791.97 kg/hm~2.Among them,the planting forest has the highest nutrient(3791.97kg/hm~2),and the second generation sprouting forest is the smallest(2358.12kg/hm~2).The total reserves of hydrolyzable nitrogen,available phosphorus and available potassium in different generations of Eucalyptus forests accounted for 45.15?50.81%of the total nutrient reserves of forest land. |
PDF Full Text Request