| Metasequoia glyptostroboides is a rare and relic tree species in China, which has widespread adaptability. Although there were many researches on the cultivation of Metasequoia glyptostroboides in plain area for agricultural protection, there was few study on the cultivation of Metasequoia glyptostroboides in mountain area for the timber purpose. Therefore, the community character, growth, biomass, litter product, and nutrient cycling of the Metasequoia glyptostroboides plantations were investigated in mountain area of South China in this project. This researchs are to determine the regularity of productivity and nutrient cycling of Metasequoia glyptostroboides plantations of different aged. The main results were as follows:1. The investigation on cultivating biological characteristics of Metasequoia glyptostroboides showed that Metasequoia glyptostroboides grew fast and adapted broadly. As its habitat implying, Metasequoia glyptostroboides grew well in the thick soil, fertile land and soil wetted.2. There were only 42 kinds of species in the understorey of Metasequoia glyptostroboides plantations, There were significant difference between the community characteristics of different aged plantations. There were 27 families,38 genus and 28 species in the 27-age plantation of Metasequoia glyptostroboides which higher than those of the 32-age plantation. The results showed that 22 kinds of species such as sapium discolor, liquidambar formosana, alniphyllum fortunei were distributed in the 27-age plantation; while 6 kinds of species could be found in the 32-age plantation, such as tea, Gahnia tristis, lophatherum gracile. The seed plants genus in undergrowth which were mainly distributed in tropical was the 27-age>the 32-age. The amount of species composition in undergrowth was shrub>herbage>arbor, stand structure was simpler but it had distinct levels which benefit for stand nutrient cycling. According to analysis of a-diversity index, the diversity index of undergrowth in the 27-age such as abundant degree index, evenness index and ecological dominance were all higher than the 32-age, diversity of undergrowth in different levels was shrub>herbage>climbing.3. There were singnificant differences from annual growth of diameter at breast height bwteen different aged Metasequoia glyptostroboides. The DBH of the 32-age could reach the fast-growing period in 12 a and could be last for 6 a (12-17a); The maximum of annual growth of diameter at breast height appeared in 27a. While the 27-age Metasequoia glyptostroboides could reach the fast-growing period in 5a, and would be last for 8a (5-12a) which 4a earlier than the 32-age.There were significant differences of average annual growth of trees height between different aged Metasequoia glyptostroboides. Height gowth of the 32-age reached fast-growing in 15a, and it could last for 6a. The 27-age reached fast-growing in 4a, andlla earlier than the 32-age.Significant difference was found between the 32-age and the 27-age. The maximum growth of annual was appeared in 25a, which was 4a later than the 27-age.The plantation stocks of the 27-age was 1.4075m3 more than the 32-age, and average volume was the 32-age< the 27-age.4. There was obvious difference on the stand biomass of Metasequoia glyptostroboides. It was in the sequence of the 32-age> the 27-age. Tree layer biomass of the 32-age was 83.46 t/hm2, which was higher than the 27-age. Distribution ratio of stem biomass was the 27-age>the 32-age. The annual average net growth of leaves, branch, stem, the bark appeared increasing as age increased. The distribution ratio of annual net growth was arranged in the order: stem>root>branch>bark>fallen>leaf; biomass of undervegetation of the 27-age was upper slope>middle slope>lower slope; litter was middle slope>upper slope>lower slope.5. There were significant differences of total biaomass of ecological system between different habitats and aged. The total biomass of the 32-age Metasequoia glyptostroboides was 1.44 times as much as the 27-age. The trees layer biomass was the 32-age> the 27-age, but the ground cover layer biomass was the 27-age>the 32-age. The nutrient accumulated amount was arranged in the order the 32-age>the 27-age; but nutrient accumulated amount of vegetation of the 27-age was 1.65 times as much as the 32-age.6. There were no significant differences of nutrient content in various organs in different aged forests. N, P, K content in organs was arranged in the order:leaf>branch>bark>stem; The content in understorey coverage was the 27-age>the 32-age; N, P, K content in shrub and herbage were higher than understorey coverage; The nutrient content in undervegetation of the 27-age was upper slope>middle slop>lower slope.7. The nutrient accumulation of different aged Metasequoia glyptostroboides was quite different. N, P, K accumulated amount in tree layer of the 32-age were increased by 116.09%,13.04%,19.19% respectively compared with the 27-age.The nutrient accumulated amount in undervegetation of the 27-age was arranged in the order:upper slope>middle slop>lower slope; nutrient accumulation of litter was lower slope>middle slop>upper slope.The difference of nutrient using efficiency of tree layer of different aged Metasequoia glyptostroboides forests was evident. The nutrient using efficiency in tree layer was the 27-age>the 32-age, as same as the nutrient using efficiency II of the stem; the nutrient using efficiency I of the stem was the 32-age>the 27-age.8. Nutrient accumulation regulation of ecological system in different conditions appeared as the same as biomass. The nutrient using efficiency of trees layer of Metasequoia glyptostroboides forests of different habitats and aged was the 27-age>the 32-age, as well as the stem nutrient using coefficient. Nutrient using efficiency of understorey vegetations was the 32-age> the 27-age.9. There were no significant different of litter between the 27-age and the 32-age, as well as the annual average accumulation. Retention of nutrient elements of Metasequoia glyptostroboides forests in different habitats and aged was the 32-age> the 27-age; and in all nutrient N>K>P. The nutrient return of the 27-age was 1.15kg/(hm2·a), which was 1.67 times as much as the 32-age. Annual nutrient uptake of Metasequoia glyptostroboides forests was the 32-age>the 27-age. The annual nutrient uptake of the 32-age was 41.64 kg/(hm2·a), which was 1.48 times higher than the 27-age. |
PDF Full Text Request