Effects Of Density Regulation And Compound Fertilizer Application On Soil Nutrient And Bamboo Shoot Yield In Chimonobambusa Utilis Forest,Gulin County

Scientific and suitable forest management measures can effectively improve forest soil quality and stand structure,and significantly increase forest productivity.Density control and fertilization are common afforestation measures in forest management.They have the characteristics of strong controllability,obvious effect,simple technology,and wide application.Chimonobambusa utilis bamboo shoots are favored by consumers because of its excellent quality.Planting Chimonobambusa utilis is an important way for farmers in the bamboo suitable area to acquire wealth.At present,the development of the Chimonobambusa utilis bamboo industry lags,and the mode of operation is still farmers'operation and production.Excessive bamboo shoots harvesting,neglected management,and low-level of forest management are still the main factors limiting the development of bamboo forests.Adopting scientific forest management measures to improve forest productivity and bamboo shoots yield is a scientific problem to be solved urgently in bamboo forest management.From June 2017 to November 2019,an experiment was carried out in the pure bamboo forest of Chimonobambusa utilis in Gulin County,southern margin of the Sichuan Basin.Two management measures,density control and compound fertilizer application were adopted,and a two-factor cross-group experimental design was used to complete the study.This study set five density levels of bamboo forest,namely control check(D₀),40,000 culm hm^-2(D₁),50,000 culm hm^-2(D₂),60,000 culm hm^-2(D₃)and 70,000 culm hm^-2(D₄));4 compound fertilizer application levels,namely the control check(F₀),"nitrogen+phosphorus+potassium"(460+60+300 kg hm^-2 a^-1,F₁),"nitrogen+phosphorus+potassium"(920+120+600 kg hm^-2 a^-1,F₂)and"nitrogen+phosphorus+potassium"(1380+180+900 kg hm^-2 a^-1,F₃).In this study,a total of 20 combinations of density and fertilization were set,and each treatment was repeated 3 times.Linear mixed effect-model was used to analyze the effects of density control and compound fertilizer application on soil nutrients,bamboo shoots period,bamboo shoots yield,and bamboo shoots net profit.Pearson correlation was used to analyze the relationship between bamboo shoots period and bamboo shoots yield and soil nutrients.Multivariate linear stepwise regression analysis was used to find the main controlling factors in soil physicochemical properties for the bamboo shoots period and bamboo shoots yield variation.The results suggested that:(1)Density control,compound fertilizer application and their interaction significantly changed the soil nutrients.The results of the linear mixed effect-model showed that with the increasing of bamboo forest density,the soil p H,organic matter,alkaline nitrogen,and Olson-P content increased the first and then decrease,the soil total nitrogen,total phosphorus,and available potassium content were increasing trend,the soil total potassium content was a downward trend.The application of compound fertilizer lowered the soil p H and increased the contents of soil organic matter,total nitrogen,alkali-decomposed nitrogen,total phosphorus,Olson-P,total potassium,and available potassium.Overall,the soil organic matter and nutrient availability were improved with the increase in the amount of fertilization,and as the density of the bamboo forest increased,it showed the law of the first improvement and then degradation.(2)The Chimonobambusa utilis forest bamboo shoots periods of different treatments range from25 days to 39 days,the bamboo shoots yields range from 2614.43 kg hm^-2 to4812.40 kg hm^-2.Density control,compound fertilizer application and their interaction significantly changed the bamboo shoots periods and yields.The parameter estimation results of the maximum likelihood method show that with the increase of the bamboo forest density,the bamboo shoots periods and yields of bamboo forest both increase and then decrease.When bamboo forest density was D₃,the estimated average value of the bamboo forest shoot period was 37.00 d,and the estimated average bamboo shoots yield was 4264.75kg hm^-2,which reached the maximum value.The period and yield of bamboo shoots in Chimonobambusa utilis forest increased with the increase in the amount of fertilization.When the amount of fertilization was F₃,the estimated average value of bamboo shoots period was 35.40 d,and the estimated average yield of bamboo shoots was 3866.63 kg hm^-2,which reached the maximum value.(3)Economic benefit analysis showed that D₁F₀,D₁F₁,D₂F₀,and D₂F₁ treatments reduced the values of bamboo shoots,with a decrease of between 0.43%and 16.09%,and the remaining treatments increased the values of bamboo shoots,with an increase between0.71%and 33.01%.The value of bamboo shoots treated with D₃F₃ was the highest at74,527.33 yuan hm^-2.D₁F₀,D₁F₁,D₁F₂,D₁F₃,D₂F₀,D₂F₁,D₂F₂,and D₂F₃ treatments reduced the net profit of bamboo shoots,with a decrease of between 8.00%and 24.31%,and the remaining treatments had increased the net profit of bamboo shoots,with an increase of between 1.80%and 32.03%.The net profit with D₃F₂ treatment was the highest at 65,921.31yuan hm^-2.The recommended net profit bamboo density of the largest bamboo shoots in Chimonobambusa utilis forest was 60,000 hm^-2,and the recommended compound fertilizer application amount was nitrogen(920 kg hm^-2 a^-1)+phosphorus(120 kg hm^-2 a^-1)+potassium(600 kg hm^-2 a^-1).(4)Correlation analysis showed that there was an extremely significant positive correlation between bamboo shoots period and soil p H,organic matter,total nitrogen,alkaline nitrogen,total phosphorus,Olson-P,and available potassium content.Bamboo shoots yield was an extremely significant positive correlation with soil organic matter,total nitrogen,alkali-decomposed nitrogen,total phosphorus,Olson-P,and available potassium,and there was an extremely significant positive correlation between bamboo shoots period and yield.(5)Regression analysis showed that soil Olson-P,available potassium,alkali-decomposed nitrogen,p H,and total phosphorus can jointly explain 68.40%of the variability in bamboo shoots period,which was the dominant factors of variability in bamboo shoots period.Soil Olson-P,alkaline nitrogen,organic matter,and available potassium can jointly explain 61.57%of the variation in bamboo shoots yield,which was the dominant factors of variability in bamboo shoots yield.To sum up,suitable density control and fertilization measures can significantly improve the nutrients of the soil in Chimonobambusa utilis forest,extend the bamboo shoots period,increase the bamboo shoots yield,and increase the economic benefits of bamboo forests.The supply of soil nutrients is the basis for the high bamboo shoots yield of bamboo forests,and the content of soil available nutrients is the main control factor that affects the bamboo shoots period and yield.When the density was 60,000 culm hm^-2 and the fertilization was nitrogen(920 kg hm^-2 a^-1)+phosphorus(120 kg hm^-2 a^-1)+potassium(600 kg hm^-2 a^-1),the economic benefits of bamboo shoots in Chimonobambusa utilis forest can achieve the maximum net profit at 65,921.31 yuan hm^-2.This research will contribute to the management of the Chimonobambusa utilis forest and increase the bamboo shoots yield,and provide a theoretical reference for the sustainable management of Chimonobambusa utilis forest in the southern margin of the Sichuan Basin.