Eco-physiological Study On High-efficiency Cultivation Of Salix Integra Raw Material Forest Along Huaihe River

Salix integra Thunb. is perennial fascicular deciduous shrub with wide adaptabilityunder adverse growth conditions （e.g. coldweather and waterlogging）. S. integra iswidely distributed in China along riparian zone. It is used for willow handicraft due to itscharacteristics of high sprouting rate and long-flexible stem. S. integra not only has higheconomic value, but also has the function of sand-fixing, water and soil conservation, andriverbank protection. Plantation of S. integra in the low-land areas can effectively avoidthe risk of natural disasters and reduce the damage and adverse effect on agriculturalproduction. Therefore, promotion of S. integra enterprise can enhance sustainabledevelopment of regional economic society, and improve the utilization of land resourceand maintain ecological balance.The researches on S. integra worldwide preliminarily concentrated in high-yieldcultivation and inter-overlapping plantation. This study conducted at Huanggang of Funanand Bangang of yingshang. The study was designed to investigate the stand biomass, soilorganic carbon pool, nutrient management and waterlogging resistance of S. integraplantations on the lowland areas along the Huaihe River. The objective of the study is toprovide a systematic techniques for sustainable management of S. integra plantation. Theresults were as follows.The mean base diameter （MBD） and mean height （MH） were, respectively,0.46-0.99cm and130.44^-187.61cm for the two cultivation patterns, which the pure stands hadhigher MBD and MH than the mixed stand did at the same age. The average total biomassof pure and mixed stands were17.55t·hm^-2and17.03t·hm^-2, respectively. The foliarbiomass was higher in the pure stand than in the mixed stand. However, the root biomasswas adverse. The biomass partitioning ranked in order as root (7.51t·hm^-2)> peeled stem（6.32）> bark （2.42）> leaf （1.16）. The contents of organic matter, total nitrogen and totalpotassium decreased with the soil depth, with no significant difference in the same soillayer for all sampling stands between the pure and mixed. The result from correlationanalysis demonstrated that the mean base diameter was significantly and positivelycorrelated with mean height. The total biomass of S. integra stand was significantly andpositively correlated with available phosphorus in all soil layers, and organic matter in10-30cm soil layer.Total biomass of the different aged S. integra stands ranked in order as10a (27.76t·hm^-2)>18a （24.98）>5a （24.47）>1a （15.06）. The biomass partitioning changed with theages. The biomass components of1a S. integra cv. qingpi ranked as peeled stem (9.29 t·hm^-2)＞root （4.11）＞bark （3.10）＞leaf （2.11）. For1a S. integra cv. hongpi, peeledstem (6.32t·hm^-2)＞root （4.11）＞bark （2.57）＞leaf （2.06）. The biomasscomponents of5a S. integra cv. hongpi ranked as peeled stem (9.84t·hm^-2)＞root （9.04）＞leaf （2.32）＞bark （3.27）; for the10a S. integra cv. hongpi as root (12.62t·hm^-2)＞peeledstem （9.87）＞bark （3.55）＞leaf （1.72）; for the18a S. integra cv. hongpi as root (12.01t·hm^-2)＞peeled stem （7.39）＞bark （2.47）＞leaf （1.31）.The contents of soil nutrients decreased with the soil depth. The contents of totalnitrogen, soil organic carbon and dissolved organic carbon （DOC） were0.97-3.32g·kg^-1,5.37^-22.62g·kg^-1, and36.96^-131.71mg·kg^-1, respectively. The contents were1.52^-2.61g·kg^-1for total phosphorous,1.69-6.94mg·kg^-1for available phosphorous,107.87-185.03mg·kg^-1for total potassium,11.40^-23.06g·kg^-1for total calcium and74.60-89.70mg·kg^-1for total magnesium.Fertilization experiments were conducted in S. integra stands under6levels: T1(30gN·m^-2), T2(20g N·m^-2+15g P·m^-2), T3(30g N·m^-2+15g P·m^-2), T4(45g N·m^-2+15gP·m^-2), T5(60g N·m^-2+15g P·m^-2), T6(15g P·m^-2), and CK （the control）. The mean basediameter, height and biomass of S. integra under the different treatments were increasedcompared with the control. The biomass of stem, root and cutting under T5treatment hadthe biggest increase compared with other treatment. The total biomass under the differenttreatments were ranked as: CK (20.42t·hm^-2)<T2（21.76）<T1（22.67）≈T3（22.95）=T6（22.96）<T4（30.20）<T5（37.64）。During the75-day simulated flooding period, the survival rates of seedlings of the twotypes of S. integra were100%. The seedlings of both types developed hypertrophiedlenticels and adventitious roots at their stem base with the different formation time （S.integra cv. hongpi was10d later than S. integra cv. qingpi）. The growth andphotosynthesis of S. integra cv. qingpi were promoted under the waterlogging stress, whilethe growth and photosynthetic properties （chlorophyll content, net photosynthetic rateand stomatal conductance） of S. integra cv. qingpi under waterlogging stress and slightflooding stress were all significantly lower than those of the control. Significant increasesof non-photochemical quenching （NPQ） and reductions of maximal quantum efficiency ofPSⅡ photochemistry （Fv/Fm） in the flooded seedlings were observed for S. integra cv.hongpi. For S. integra cv. qingpi, however, the value of Fv/Fmwas fluctuated from0.80to0.85. There were no significant differences in NPQ and Fv/Fmbetween the treatments andthe control.The soil organic carbon （SOC） concentrations in0-30cm soil layer were6.80g·kg^-1 for the pure willow plantation （WP）,8.50g·kg^-1for the willow-poplar mixed plantation（WPP） and7.71g·kg^-1for the poplar plantation （PP）. The mean SOC density was2.88,3.26and2.95kg·m^-2for the above-mentioned three land use types, respectively.Correlation analysis showed that SOC was significantly and positively correlated withmoisture, NO3--N and total N. Under the same land use type, the concentration and densityof SOC decreased with soil depth. Soil DOC, DON contents in WPP were higher than thatin WP and PP. Soil DOC, DON contents fluctuated obviously with the seasons. DOC andDON contents under the different land use types were higher in summer and spring, whilerelatively lower in autumn and winter.In0-30cm soil, the contents of soil microbial biomass carbon （MBC） and nitrogen（MBN） under the different land use types were ranked as WPP> WP> PP. Seasonalvariations of soil MBC and MBN contents were similar to those of DOC、DON contents,with higher contents in spring and summer and lower contents in winter.The correlation analysis showed that MBC was significantly and positively correlatedwith MBN, DON, DOC, soil moisture （p<0.01）, while negatively correlated with NO3--N,pH and soil bulk density. MBN was significantly and positively correlated with DOC（p<0.01）, while negatively correlated with NH4+-N, pH. DOC was significantly andpositively correlated with NO3--N, total N, total P, available P （p<0.01）, while negativelycorrelated with pH, EC. DON was significantly and positively correlated with total N andtotal P （p<0.01）, while negatively correlated with pH.The annual average rate of soil respiration was1.68μmol·m^-2·s^-1for WP,2.33μmol·m^-2·s^-1for WPP,1.61μmol·m^-2·s^-1for PP, respectively. The maximum daily rate ofsoil respiration appeared in summer (6.64μmol·m^-2·s^-1), and the minimum in winter (0.13μmol·m^-2·s^-1). The result from regression analysis demonstrated that there was exponentialrelationship between soil respiration rate and surface air temperature. The value of R2was0.71for WP,0.62for WPP,0.54for PP, respectively. The WPP was beneficial to thecarbon sequestration in soil compared to WP. The lower SOC storage in WP was related tothe extensive management. It was suggested that in the future forest management,reasonable tillage and fertilization should be taken to improve soil fertility and enhancesoil carbon sequestration.