Study On Response Characteristics Of Underground Whip Root System And Ground Growth Of Phyllostachys Edulis Forests Under Different Strip Cutting

Moso bamboo（Phyllostachys edulis）is an important forest resource in China,and the technical and economic feasibility of scientific cutting is crucial to the sustainable utilization of bamboo resources.Strip cutting has changed the labor-intensive cultivation and could realize the mechanized management of bamboo forests.It has become one of the hotspots of scientific research on bamboo forest cutting and cultivation.However,the current strip cutting focuses on the habitat and bamboo forest restoration characteristics,and there is no systematic and in-depth study on the autonomous regulation process of the bamboo forest.For this reason,the bamboo forests in southern Jiangsu was took as the research object.The 4 kinds of cutting widths（CK（Selective cutting operation,strip cutting was not carried out）,3 M,9 M,15 M）)and the growth characteristics of moso bamboo included the sprouting period,the swelling period of winter bamboo shoots,the growth stage of the bamboo shoots,the bamboo leaf display period,and the and whip growth period were investigated and analyzed.The phenotypic plasticity changed under the clonal integration characteristics of the moso bamboo forest after strip cutting was clarified,and the interaction mechanism between the underground whip root system and the ground-growing bamboos of the moso bamboo forest was revealed,so as to provide a theoretical basis for the scientific management of the moso bamboo forest strip cutting.The main results are as follows:1.The abundance of dominant bacteria in the rhizosphere soil of the moso bamboo forest was increased,soil enzyme activity was increased,and the rate of available nutrient decomposition was accelerated after strip cutting,and it was increased first and then decreased with the growth of new bamboo,and the spring bamboo shoots peaked in the peak period.Strip cutting reduced the number of bacterial groups in the rhizosphere soil,but increased the abundance of dominant bacteria such as Proteobacteria,Actinobacteria,Firmicutes,etc.The difference in the composition of soil bacterial communities between the medium and small intensity cutting and the control plots gradually decreased with bamboo growth.Carbohydrate and amino acid metabolism were the main functions in the microbial metabolism pathway;After harvesting,the activities of soil invertase,urease and acid phosphatase are enhanced;The activities of soil invertase,urease and acid phosphatase were enhanced after strip cutting;The soil nutrient index of the 9 M plot was the best,The content of soil organic matter,available nitrogen,available phosphorus and available potassium were increased by 6.82%,11.62%,9.83%,and 13.61%respectively compared with the control plot;The grey correlation analysis showed that the soil bacterial diversity,enzyme activity and alkaline hydrolysis nitrogen had a significant correlation with the DBH of new bamboo.2.The content of soluble sugar,soluble protein and endogenous hormones of new bamboo after strip cutting were increased,which would help break the dormancy of whip buds,improve stress resistance,and promote growth and development.The contents of gibberellin,auxin,soluble protein,IAA/ABA,and GA₃/ABA were all increased first and then decreased with new bamboo growth,and the peak of spring bamboo shoots was the largest.The soluble sugar content continued to rise,and the abscisic acid content continued to decrease with new bamboo growth.The contents of gibberellin and soluble protein in the strip cutting plots were all 9 M>15 M>3 M>CK,and the average gibberellin and soluble protein contents of cutting plots were 0.97μg·g^-1 and 33.28 mg·g^-1,which were higher than those in the control plot(0.71μg·g^-1,26.41mg·g^-1)36.6%and 26.0%.The content of auxin and soluble sugar before the expansion stage of winter bamboo shoots was 15 M>9 M>3 M>CK,and the soluble sugar content of the control plot increased after the peak of the spring bamboo shoots,and the maximum soluble sugar content was 86.77 mg·g^-1during the bamboo leaf development stage,which was significantly higher than that of the cutting plot at 52.06 mg·g^-1.The auxin content was 9 M>15M>3 M>CK,and the average auxin content between the strip cutting plots was 0.075μg·g^-1,which was higher than that of the control(0.055μg·g^-1)increased by 36.4%.3.The bamboo shoot stage of the bamboo forest was advanced,the number of shoots increased,the number of finished bamboos increased,and the distribution pattern of above-ground biomass changed after strip cutting.C:N and C:P decreased during the spring bamboo shoots peak period and the bamboo leaf development period,the root growth period was significantly improved after strip cutting.The number of shoots and new bamboo was 9 M>15M>3 M>CK with the increases of cutting width.The maximum number of shoots in the 9 M plot was 4038/hm²,and the number of new bamboos was 2482/hm²,which was 2.8 times of the control plot.The height of new bamboo was decreased,the diameter at breast height was decreased,and the biomass of each component was significantly reduced after strip cutting.However,the relative growth rate of branch-total biomass and leaf-total biomass had changed from allometric growth relationship to constant growth relationship.The leaf emergence intensity of new bamboo increased significantly,the distribution ratio of bamboo leaves increased significantly,and the relative leaf biomass increased with the increase of strip cutting width.C:N and C:P were lower than the global average level during the spring bamboo shoot peak period and the mature bamboo leaf development period,N:P<14,while the whip root growth period C:N and C:P increased,which was higher than the global level,14<N:P<16.4.The morphological structure and biomass distribution pattern of the underground whip roots of the moso bamboo forest changed after strip cutting.The total shoot amount of whip roots increased,and the proportion of new shoots and shoots increased significantly.The number of new whip nodes,whip root thickness and number of whip were increased compared with the control plot,and the difference between the plots was not significant.The proportion of capillary root biomass was increased after strip cutting.The proportion of capillary root biomass in the3M plot was slightly higher than that of the control（50%）.The proportion of capillary root biomass in the 9 M plot was 69%,and the proportion of capillary root biomass distribution increased,and the plot was dominated by fine root growth.As a result,the ratio of thickness/fineness dropped to 0.46,which was 54.5%lower than 1.01 in the control plot,and the proportion of capillary root biomass in the 15 M plot increased to 57%.The average total bud volume,new bud ratio,and shoot rate of the bamboo forest after cutting were 118,800 pieces/hm²,54.66%,and 3.04%,which was an increase of 16.7%,7.72%and 1.59%compared with the control plot（101,900 pieces/hm²,46.94%,1.45%）.In summary,strip cutting caused the increase in the concentration of gibberellin in the whip buds of moso bamboo,which helped to break the dormancy of whip buds and increase the number of shoots and new bamboos.The resource allocation of various components were reallocated by moso bamboo through physiological integration after strip cutting.Nutrients such as carbon and nitrogen are the limiting factors for the recovery of new bamboo after strip cutting in the bamboo forest,which directly affects the number of bamboo shoots withdrawn and the quality of bamboo shoots.Therefore,it is recommended to strengthen the application of nitrogen and organic fertilizers during the shoot stage,the new bamboo development stage,and the whip growth stage during the forest management process in order to reduce retreat bamboo shoots,improve the quality of new bamboo,accelerat the recovery process of moso bamboo forest after strip cutting.