| In the rock-desertification region,the forest vegetation recovery has become key point and emphasis of rocky desertification in Southwest Guangxi karst region,based on the fragile ecology and complex topography.Delavaya toxocarpa Franch. as karst native common pioneer species and fuelwood forest species has a great development potential,and that choosing afforestation and silvicultural technology to development D. toxocarpa has the extremely vital significance to ecological restoration and economic development in Southwest Guangxi.The 12-year-old D. toxocarpa plantation in Southwest Guangxi karst region were carried to investigate its growth regularity,biomass,carbon storage and nutrient use efficiency, which can provide a scientific management and technical support and provide a scientific reference for vegetation restoration in southwest Guangxi karst area. The results showed that:(1)Growth pattern:The average tree height of 12-year-old D. toxocarpa plantation was 6.4 m,the average diameter at breast height(DBH) was 7.8 cm;DBH was almost in 6 and 8 diameter class; there was 3-5 D. toxocarpa sprouts in every stump, which showed higher sprouting ability.(2)Biomass and biomass productivity:The total biomass of D. toxocarpa plantation ecosystem was 75.74 t·hm-2,the biomass of tree layer was 71.27 t·hm-2,the order of different tree layer organs was:trunk>branch>root pocket> bark>leaf>lateral root; the tree layer annual average net primary productivity was 5.94 t·hm-2·a-1.(3)Carbon content and carbon storage:The average carbon content changing range of Delavaya toxocarpa plantation in different plant organs was between 447.77～495.07 g·kg-1, the order of average carbon content in tree layer different organs was:trunk>root pocket>branch>leaf>lateral root> bark. The total carbon storage of D. toxocarpa plantation ecosystem was 72.74t·m-2,the carbon storage of vegetation layer was 36.86 t·hm-2,the carbon storage of soil layer was 35.87t·hm-2,the order of tree layer carbon storage was:trunk>branch>root pocket>trunk bark>leaf>lateral root.(4)Characteristics of soil nutrient:The soil organic matter, total nitrogen, total phosphorus and total potassium content of 0-20 soil layer in D. toxocarpa plantation were 91.61 g·kg-1,5.12 g·kg-1,2.99g·kg-1 and 4.44g·kg-1 respectively, while the available calcium and magnesium contents were relatively low.(5) Accumulation and distribution of plant nutrient elements:the order of five nutrient elements total content in various D. toxocarpa tree layer organs was: bark>leaf>branch>lateral root>root pocket>tree trunk, the order of the nutrient elements content was N>Ca>K>Mg>P, the order of the nutrient elements in litter layer was Ca>N>Mg>K>P, the order of understory vegetation nutrient elements was Ca>N>K>Mg>P. The total storage of nutrient elements such as N、P、K、Ca、Mg in D. toxocarpa tree layer organs was 1662.76 kg·hm-2,the order of nutrient elements storage in different organs was tree trunk>branch>root pocket> bark>leaf>lateral root. The order of different nutrient elements storage was Ca>N>K>P>Mg. The Annual net accumulation of nutrients of tree layer was 138.56kg·hm-2·a-1.(6)Nutrients use efficiency:Production of It dry matter of D. toxocarpa plantation needed 23.33kg macro-elements(N、P、K、Ca、Mg). The order of element nutrients use efficiency of every nutrient was Ca>N>K>P>Mg. |
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