Study On Soil Respiration And Components Of Different Pinus Massoniana Plantations In Guangxi

This study used different ages,different management models and different climatic conditions of P.massoniana plantations in Huashan Forest Farm in Guangxi?Central Subtropical Climate Conditions?,Zhenlong Forest Farm?Southern Subtropical Climate Conditions?and Paiyangshan Forest Farm?Northern Tropical Climate Conditions?.Subject,used the LI-8100A soil respiration measurement system and Em50 soil temperature and humidity measurement system to determine the soil respiration rate and 0-5cm soil temperature and humidity.At the same time,the average wood-soil column method and the ring knife method were used to determine the environmental factors such as root biomass,existing litter amount and soil physical and chemical properties of different types of P.massoniana plantations,and to analyzed the horsetails of different forest ages,different management models and different climatic conditions.The characteristics of soil respiration and composition of pine plantations,and the relationship between environmental factors and soil respiration and composition of different types of P.massoniana plantations,and the used of Em50 to determine the soil temperature.The continuous monitoring data of humidity calculates soil carbon emissions to realized dynamic monitoring of soil respiration carbon emissions of different P.massoniana plantations,and provides theoretical support for scientific estimation of soil respiration and soil carbon emissions monitoring of P.massoniana plantations.The conclusion of the study were as follows:?1?Differences in forest age,management model and climatic conditions had significantly changed the soil respiration rate of P.massoniana plantation,but had little effect on the seasonal variation of soil respiration;the increase in forest age has increased the total soil respiration?Rtot?and heterotrophic breath?RH?,but litter layer respiration?RL?and mineral soil respiration?RM?increased first with the forest age The trend of decreasing and decreasing first and then increasing;the Rtot,RH,RR and RM of M2_SSS mixed forest of P.massoniana and Phoebe brazifolia mixed forest were significantly higher than that of pure P.massoniana forest,but the change of stand density in pure P.massoniana forest did not significantly change the Rtot and RM;the increase in latitude generally reduces the Rtot and RH of P.massoniana plantation;soil respiration and composition had a significant exponential positive correlation with soil temperature,and the correlation with soil moisture was relatively low;forest age vs.soil temperature The effect of the sensitivity index Q₁₀0 value was not significant,but the Rtot temperature sensitivity index Q₁₀0 value in the M2_SSS of P.massoniana and Phoebe brazifolia mixed forest was higher than that of pure P.massoniana forest,but relatively higher density(planting density 2500 plants·hm-2,reserved Density 1156 plants·hm^-2)The temperature sensitivity Q₁₀0 values of RH and RM of D1_SSS in pure P.massoniana forest were also relatively highest;the maximum values of soil respiration temperature sensitivity index of P.massoniana plantation also appear in relatively low latitudes in South Asia Among the tropical and northern tropical forest stands,the young sub-tropical forest Y_SS?3.127?,the northern tropical mid-age forest M_NT?5.812?and the northern tropical over-mature forest O_NT?3.633?,in the young forest and over-mature forest,the temperature With the increase of latitude,the sensitivity index Q₁₀0 value showed a significant downward trend.?2?In general,the root biomass and litter stock of different diameter grades of P.massoniana plantation showed an increasing trend with the growth of forest age.The management model also has a significant effect on root biomass and litter stock.The root biomass of mixed forests was significantly higher than that of pure P.massoniana forest.The D1_SSS root biomass and litter stock of relatively higher density forests were also higher than D2_SS.The influence of climatic conditions on root biomass was as follows:With the increase of latitude,the root biomass of young P.massoniana forest was increasing,and the root biomass of middle-age forest and overmature forest was decreasing;The total present amount of surface litter in young forests and middle-aged forests showed a decreasing trend with increasing latitude,while overmature forests showed an increasing trend with increasing latitude.Among them,the total root biomass,coarse root biomass,root biomass in 0-20cm soil layer,and the litter content and proportion in the litter litter showed a significant or extremely significant positive correlation with Rtot.?3?The physical and chemical properties of soil had a significant effect on soil respiration.The Rtot and RH of P.massoniana plantations at different ages had a significantly negative correlation with total P,available P and soil bulk density,and were related to soil organic carbon,soil saturated water holding capacity,and soil penetration The rate has a very significant positive correlation;Rtot,RH and soil C,soil N,soil organic carbon,soil 0-20cm soil pH,soil field water holding capacity,saturated water holding capacity,non-capillary porosity,total porosity and infiltration of P.massoniana plantations with different management modes There was a significant negative correlation between the rate and a very significant positive correlation with the soil bulk density;The Rtot and RR of P.massoniana plantation under different climatic conditions were significantly negatively correlated with soil total P,total soil porosity,pH value of 0-20cm soil layer,and significantly positively correlated with soil organic carbon content,RH was0-20cm The pH value of the soil layer was significantly negatively correlated with soil C and organic carbon content,while RR was significantly negatively correlated with soil total P and total porosity.?4?The soil respiration carbon emissions were significantly affected by forest age,management model and climatic conditions.The Rtot soil respiration carbon emissions of P.massoniana plantation increased with the age of the forest,at 809.34gC·m^-2-1284.63gC·m^-2.In addition to RL,the annual carbon emissions of Rtot and other respiratory components showed that M2_SSS was significantly higher than that of pure forest.The annual carbon emissions of Rtot and RH of P.massoniana plantation under different climatic conditions showed a downward trend with increasing latitude.Comparing the estimation results of the annual carbon emissions of soil respiration and components by the monthly accumulation method and the equation simulation method,it was found that the results of the two methods for calculating the carbon emissions of soil respiration and components in P.massoniana plantation in the southern subtropics The difference was small,ranging from 0.95%to 32.75%.Among them,the difference in the estimation results of total soil respiration was between 0.96%and 4.72%.The daily carbon emissions of the equation simulated Rtot in each forest stand generally showed a single peak curve that increased from January to August and decreased from September to October,and the Rtot difference between the forest stands was from June to August.The most significant.