| This study was based on 24 typical shrubs of 12 counties in Hainan Island, the distribution characteristics of organic carbon and nitrogen in shrub ecosystem of Hainan Island were studied by studying the contents, density and reserves of organic carbon and nitrogen in soil, litter and vegetation, and the organic carbon and nitrogen reserves. Hoping to fill the gaps in the study of marine shrub ecosystem in Hainan Island and provide the basic data for studying the present situation, rate and potential of carbon sequestration and nitrogen fixation, and provide the theoretical basis for evaluating its important ecological value. The main results are as follows:(1) The average organic carbon content of the soil was (6.20 ± 0.61) g/kg and the average organic carbon density was 5.94 kg/m2;The soil organic carbon content decreased with the increase of soil depth in the vertical distribution, After the organic carbon density was uniform to 10cm thickness,the same trend was also observed;The soil organic carbon content decreased with the increase of soil depth. The difference of soil carbon density between 0-30cm and 0-50cm soil respectively, 46.15% and 65.28%, with a strong table polymerization.(2) The average soil total nitrogen content (0.60 ± 0.32) g/kg,the average nitrogen density of 0.82kg/m2; 6 average soil nitrogen content of soil layers were (0.87 ± 0.48),(0.71 ± 0.43),( 0.61 ± 0.34),(0.51 ± 0.25),(0.46 ± 0.23) and (0.41 ± 0.26)g/kg,showing a decreasing trend,smaller differences between soil; soil layers unify the thickness compared to 10cm, The proportion of 0-30cm and 0-50cm is 40.79% and 58.39%, respectively, and it has strong table polymerization; Soil carbon / nitrogen ratio was (9.59 ±1.87).(3) Shrub litter biomass between 96.19-323.35g/m2, an average of 221.56g/m2; litter nitrogen, organic carbon content of between 0.33-1.51% and 40.75-46.84%, respectively,the average 0.83% and 43.76%; litter nitrogen density between 0.44-3.72g/m2, with an average of 1.83g/m2; organic carbon density 41.23-142.71g/m2, with an average of 96.93 g/m2.(4) The biomass of herbs was between 252.99-665.24g/m2,the average was 438.20 g/m2; the aboveground biomass of herbaceous plants was between 81.63-483.66g/m2, the average was 241.59g/m2, The average nitrogen content was 0.34-2.40%, the average was 1.22%,the underground part was 0.28-1.06%,the average value was 0.59%,and the herbaceous ground was Part of the organic carbon content of 27.08-45.19%, an average of 40.73%, the underground part of 11.00-44.21%, an average of 32.23%.(5) The dominant species of shrub root nitrogen content between 0.25-1.16%, with an average of 0.60%; stem nitrogen content of 0.28-1.21%, with an average of 0.59%;nitrogen content in leaves between 0.93-5.99% , The average value was 2.32%; the content of organic carbon in shrub was very small, with an average value of 44.52%.(6) The sum of biomass and litter stock in shrub vegetation between 1213.18-6336.21g/m2, the average is 2438.08g/m2; the average biomass of shrub layer is 1778.33g/m2, the herb layer is 438.20g/m2, litter was 221.56g/m2. The biomass of each part of vegetation was shrub layer (73%)> herb layer (18%)> litter layer (9%).(7) The biomass equation was obtained in 10 kinds of shrubs dominant species are:Rhodomyrtus tomentosa W = 791.02 + 92.34Cv, R2 = 0.56; Baeckea frutescens W = 435.97+ 298.40D, R2 = 0.85; Flacourtia W = 299.31 + 2739.25D, R2 = 0.81; Leucaena leucocephala W = -566.26 + 1462.97H, R2 = 0.91; Crotalaria pallida W = 58.27 +710.50Cv, R2 = 0.90; Pterospermum heterophyllum Hance W = -6.02 + 255.45H, R2 =0.70; Ficus heterophylla W = 353.45 + 55.74D, R2 = 0.93; Pandanus tectorius W = 283.20+ 55.42D, R2 = 0.85; Syzygium tephrodes W = 1127.88 + 111.44Cv, R2 = 0.90; Alchornea trewioides W = -1046.98 + 850.51D, R2 = 0.95; these biomass estimation equations were statistically significant (P <0.01).(8) The average organic carbon density of shrub layer was 791.71g/m2, the herb layer was 160.25g/m2, the litter layer was 96.93g/m2, the soil layer was 5.92kg/m2, the shrub organic carbon density was 6.97kg/m2 The order of the organic carbon density of each component is: soil layer>shrub layer>herb layer>litter layer.(9) The average nitrogen density of the shrub layer was 23.25 g/m2, the herb layer was 3.93 g/m2, the litter layer was 1.83 g/m2, the soil layer was 0.58 kg/m2, the shrub nitrogen density was 0.61 kg/m2, The order of the nitrogen density of the constituent parts is: soil layer> shrub layer> herb layer> litter layer.(10) The total nitrogen reserves of shrub community in Hainan Island were 2.80 ×105t, and the four parts of nitrogen storage were sorted by: soil> shrub> herbaceous> litter;soil layer Shrub community had 95.25% of total nitrogen reserves, 3.81% of shrub layer,0.64% of herbaceous layer and 0.30% of litter.(11) The organic carbon storage of shrub community in Hainan Island was 3.32 × 106t,and the four parts of organic carbon storage were as follows: soil> shrub> herbaceous>litter; soil organic carbon storage was 2.57× 106t, 85.09% organic carbon reserves, shrubs,herbs and litter were 11.22%, 2.30%, 1.39%. |
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