Effect Of Slope Aspect On Biomass And Carbon Storage Of Vitex Negundo Var.heterophylla Shrub In Low Mountains And Hilly Area Of Taihang Mountains

The study of shrub biomass and carbon storage is prime important to calculate carbon sink and carbon sequestration potential of terrestrial ecosystems.The Vitex negundo var.heterophylla shrub is a main vegetation type in the low mountains and hilly area of Taihang mountains in Hebei Province,which plays an important role in biodiversity,soil and water conservation and regional ecological security.In this study,the Vitex negundo var.heterophylla shrub at different slope aspects in the low mountains and hilly area of Taihang mountains in Hebei Province was taken as the research object.Individual sample(whole cluster)was harvested,the characteristics of plant and biomass distribution of Vitex negundo var.heterophylla shrub in diferent slope aspects were analyzed.In addition,the trade-off of paired traits and allometric growth relationship of Vitex negundo var.heterophylla shrub at different slope aspects were studied.Effect of slope aspect on biomass and carbon storage were revealed,providing scientific basis for the calculation of biomass and carbon storage,management of the Vitex negundo var.heterophylla shrub in this area.The main results are as follows:(1)Individuals with height(59.67 cm),main stem length(43.11 cm),base diameter(0.68 cm)and crown diameter(1006.75 cm2)of the Vitex negundo var.heterophylla at sunny slope were the smallest at all slope aspects,while their main root length(22.34 cm)were the largest.The characters of the Vitex negundo var.heterophylla were not significant different between the same organs in different slope aspects.All characters of the Ziziphus jujuba var.spinosa individuals were the biggest in the sunny slope.All the characters of the Ailanthus altissima individuals were significantly higher at the shady slope than the other slope aspects.(2)The biomass was not significant different in biomass between the same organs at different slope aspects.The root biomass of the Vitex negundo var.heterophylla clustered samples were significantly higher at sunny slope(61.55 g)than that in semi-shady slope(28.94 g)and shady slope(25.86 g).The biomass of aboveground,underground and entire individuals of Ziziphus jujuba var.spinosa individual were the largest at the sunny slope and the semi-shady slope.The ratio of leaf biomass and fruit biomass increased and then decreased from sunny slope to shady slope.The total biomass and the biomass of each organ of the Ailanthus altissima individuals were significantly higher at the shady slope than the other slope aspects.The biomass distribution proportion at slope aspects was leaf>stem>root,except that Ailanthus altissima in the shady slope showed the largest proportion of stem biomass(45.8%).The biomass of herb layer gradually increased along the gradient of sunny slope,semi-sunny slope,semi-shady slope and shady slope.The biomass of herb layer at the shady slope(120.42 g/m2)was 1.70 times greater than at the sunny slope(70.76 g/m2).The biomass of litter layer at the semi-shady slope was the largest(97.97 g/m2),and he lowest was 80.46 g/m2 at semi-sunny slope.(3)There is a trade-off between the paired characters of the dominant specie Vitex negundo var.heterophylla at different slope aspects.In the trade-off between the main root length-main stem length and the root biomass-stem biomass among the individuals,shady slope improved growth of main root length and root biomass,and the length of main root and main stem in semi-sunny slope is 57.1%higher than that of sunny slope.At the stem biomass-main stem length and root biomass-main root length,stem biomass and main root length in sunny slope and stem biomass and root biomass in semi-sunny slope presented great.The stem biomass-main stem length at semi-sunny slope was 69.3%higher than that at sunny slope.The biomass of each organ of the Vitex negundo var.heterophylla individual was in allometric growth,and there was a trade-off between biomass distribution in different organs.Between the main root length-main stem length and the root biomass-stem biomass among the Vitex negundo var.heterophylla clustered samples,except the sunny slope whose trade-off value was close to 0,preferred to improve the main stem length.The sunny slope and the semi-shady slope preferred to accumulate more root biomass than stem biomass,which was 59.2%higher at sunny slope than that at semi-shady slope.In the root biomass-main root length,most of the slopes preferred to improve root biomass.The biomass of Vitex negundo var.heterophylla clustered samples changed from allometric growth to isokinetic growth,and there were optimal distributions of biomass in different organs.(4)The carbon content and carbon storage of different slopes in Vitex negundo var.heterophylla shrub are different.The carbon content of Vitex negundo var.heterophylla(40.3%)and Ziziphus jujuba var.spinosa(25.7%)individual sample were the largest at the sunny slope,the carbon storage of Vitex negundo var.heteroophylla single plant was relatively small at the sunny slope(0.140 t/hm2).The carbon content of the Vitex negundo var.heterophylla clustered samples at the sunny slope(32.3%)was smaller,but the carbon storage at the sunny slope was the largest(1.130 t/hm2).The carbon content of herb in semi-shady slope was the largest(32.6%).The carbon storage of herb at shady slope(0.253 t/hm2)is significantly higher than that at sunny slope(0.143 t/hm2).There was no significant difference in carbon content and carbon storage among different slope aspects in litter layer.There was significant negative correlation between soil carbon content and slope aspect,soil depth and soil porosity.Simultaneously,soil organic carbon storage exists"Aggregation surface phenomenon”,having significant negative correlation with slope aspect,soil depth and soil stone content.(5)The carbon storage of the Vitex negundo var.heterophylla shrub showed a trend that semi shady slope(41.664 t/hm2)>sunny slope(35.873 t/hm2?semi sunny slope(26.934 t/hm2)>shady slope(22.696 t/hm2).Soil carbon storage were mainly composed of Vitex negundo var.heterophylla shrub at four slope aspects.The slope aspect influenced the light,temperature,air humidity and the physical and chemical properties of soil,thus affecting the distribution pattern of biomass and carbon storage of Vitex negundo var.heterophylla shrub.