| Today,planting Eucalyptus Robusta Smith cause a lot of ecological problems, much attention has been paid to explore scientific and rational management rotation is particularly important.3 kinds of rotation(7a,10a,13a.) of E.grandis×E.urophylla Plantations are selected by this article to research on biomass and carbon storage. The purpose is to reveal different rotation of E.grandis × E.urophylla plantations of biomass and carbon carbon storage distribution rules, and providing the scientific basis to explore the E.grandis ×E.urophylla Plantations under the system of ecological mature age (plantations restored the front of the disturbed state age). Goal is made of Eucalyptus plantation in meet economic benefits at the same time, as far as possible to reduce their impact on the ecological environment, and look for the balance of economic benefits and ecological protection, promote sustainable management of Eucalyptus plantation. The results of the study are as follows:(1) Vegetation layer biomass:The results show that, Significant differences of biomass in different rotation vegetation layer (including tree layer, shrub layer, herb layer, litter layer), the forest biomass of 13a (370.92 t/hm2) is significantly higher than 10a(254.25 t/hm2) and 7a (172.52 t/hm2), respectively higher than 45.89% and 115.00%; biomass of 10a was also 47.37% significantly higher than 7a. With the extension of rotation, the tree layer biomass increased gradually, biomass of 13a is 1.55 times of 10a,2.32 times of 7a;and biomass of 10a is 1.49 times of 7a.The numerical value of crown/trunk and root/trunk are decreasing with the extension of rotation, The numerical value of crown/trunk of 7a,10a and 13a is 14.34%, 10.41% and 9.10% is 14.34%, respectively, and the numerical value of root/trunk is 24.41%, 19.46%,14.92%.(2) he distribution of the vegetation layer biomass:The ratio of tree layer biomass increased with the extension of rotation, by 7a,10a of 87.38%,88.54%,13a increased to 94.25%; The biomass proportion of shrub layer increase after decreases first,7a is increased from 5.26% to 7.03% of 10a, and, and then fell to 3.39% of 13a; There are similar changes obout the biomass proportion of herbaceous layer and litter layer with age increasing, all with the extension of rotation and decreasing, Where the herbaceous layer biomass ratio from 2.43% of 7a fell to 0.61% of 13a, while the litter biomass was 4.93% fell to 1.74% accordingly.(3) Productivity of vegetation layer:Different rotation own different levels of productivity and stand productivity increases with the growth of the age, stand productivity of 7a,10a and 13a are 36.42,45.70 and 47.51 t/hm2·a, respectively. There are similar rule about the productivity pf tree layer, the descending order is 13a (36.65t/hm2·a)> 10a (29.78t/hm2·a)> 7a (26.38 t/hm2·a),the understory vegetation of E.grandis×E.urophylla plantations also maintained a high productivity, respectively,6.45 t/hm2·a (7a),10.88 t/ hm2·a (10a) and 7.86t/hm2·a (13a).(4)Soil microbial biomass at 0-10cm:The variation with the growth of the age about Soil microbial biomass (PLFAs) at 0-10cm soil depth in E.grandis×E.urophylla plantations with different rotation is that:10a stand up to (21.89 ± 0.89 mmol/g), followed by the old stand 13a (18.62 ± 2.67 nmol/g),7a students stand a minimum (10.81 ± 3.54nmol/g). The ratio of bacteria/fungi with the extension of the rotation are 34.86%,37.36%,21.75%.The maximum of Soil microbial PLFAs and bacterial PLFAs at 0-10cm soil depth is in 10a. Along with the increasing of age, the microbial biomass carbon content increased significantly,10 a (739.25 mg/kg) is more than 7 a (238.46 mg/kg) and 13 a (496.82 mg/kg), and there is significant difference (p<0.05).(5) Ecosystem carbon storage:The total ecosystem carbon storage in descending order of three rotations:13a (250.44 tC/hm2)> 10a (187.07tC/hm2)> 7a (166.03 tC/hm2), the ratio of 10a increased 12.68% compared 7a, and the ratio of 13a increase of 50.84% compared 7a, increase of 33.87% compared 10a. The total carbon storage of tree layer exists a significant difference between three rotations, and with the extension of the rotation, the total carbon storage increases.10a tree layer of carbon stocks (102.42 tC/hm2) is 1.49 times of 7a,13a (161.15 tC/hm2)is 2.34 times. Of 7a, and 1.57 times of 10a. The contribution of shrub layer and litter layer carbon storage changes with age is not much difference. Soil carbon storage in descending order are:7a (89.99tC/hm2)> 13a (81.07 tC/hm2)> 10a (73.63 tC/hm2). |
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