| Caesalpinia sappan is resistant to poverty and adaptability,it is an excellent tree species for afforestation in karst areas,at the same time it has a high medicinal value.With 5 years old of C.aesalpinia sappan plantation ecosystem as the research object,Studied on biomass and productivity,carbon content and reserves,nutrient content and accumulation,stoichiometric.;characteristics of carbon and nutrients of C.aesalpinia sappan plantation ecosystem.Aims to provide scientific theoretical reference for afforestation and tending management of Sumu plantation in karst area of Guangxi.The results show that:(1)The biomass per plant of Caesalpinia sappan plantation is 6.23 kg/plant.the total amount of biomass of Caesalpinia sappan plantation ecosystem is 17.46 t/hm2,each component behaves as arbor layer(14.01 t/hm2)>litter layer(1.89t/hm2)>understory shrub grass layer(1.56t/hm2).The biomass of each organ in the arbor layer is ranked as stem>branch>root tip>leaf>lateral root>fruit.(2)The net productivity of Caesalpinia sappan plantation was 3.50 t·hm-2·a-1,each component behaves as arbor layer(2.81 t·hm-2·a-1)>litter layer(0.38 t·hm-2·a-1)>understory shrub grass layer(0.31 t·hm-2·a-1).(3)The average carbon content of the arbor layer of C.aesalpinia sappan plantation is 495.06 g/kg,it ranged from 394.31?506.39 g/kg,each organs behaves as branch>leaf>stem>root tip>fruit>lateral root.Carbon content of understory shrub grass layer litter layer and soil layer were 423.00 g/kg,487.77 g/kg,56.13 g/kg,respectively.The soil layer has a high carbon content level.(4)The total carbon storage of C.aesalpinia sappan plantation ecosystem was 135.36 t/hm2,The carbon storage of arbor layer,shrub layer,litter layer and soil layer were 6.93 t/hm2,0.66 t/hm2,0.92 t/hm2,126.85 t/hm2,respectively.The soil layer is the most important carbon pool of the Caesalpinia sappan plantation ecosystem.the annual net carbon sequestration of tree layer was 2.14 t·hm-2·a-1,and annual net carbon accumulation was 1.39 t.hm-2.a-1.(5)Average total content of nutrients element of N,P,K,Ca in arbor layer,shrub layer,litter layer and soil layer were 27.02 g/kg,17.62 g/kg,18.53 g/kg?4.74 g/kg,sort by size were Ca>N>K>P,N>Ca>K>P,Ca>N>K>P,K>Ca>N>P,respectively.Total accumulation of nutrients in ecosystems was 43.34 t/hm2,each component behaves as soil layer(42.85 t/hm2)>arbor layer(378.50 kg/hm2)>litter layer(66.22 kg/hm2)>shrub layer(42.87 kg/hm2).(6)Total annual net accumulation of nutrients in the arbor layer was 75.69 kg·hm-2m·a-1,accumulation of each element behaves as Ca>N>K>P.Caesalpinia sappan plantation averagely product It dry biomass required the total amount of nutrient elements was 27.01kg,utilization efficiency behaves as P>K>N>Ca.Low utilization of Ca and N elements during the growth of Caesalpinia sappan,so,appropriate elements can be added during the artificial cultivation process.(7)The ratio of C:N,C:P,C:K,C:Ca in arbor layer were 60.07,299.74,131.57,36.99,respectively.The higher degree of lignification,the higher nutrient utilization rate.C has a strong coupling relationship with Ca in arbor layer(p<0.01),equations can be modeled as Y=Y-=0.0232X+4.425(R2=0.9526).P is significantly positively correlated with K(p<0.01),equations can be modeled as Y=3.6469X0.612(R2=0.9136).The ratio of C:N?C:P?C:K?C:Ca in soil layer were 4.65,17.42,2.07,4.08,respectively.Soil carbon source,organic matter decomposition and mineralization rate are relatively high,ti have a good nutrient supply level. |
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