Nutrient Distribution Of Pinus Massoniana And Its Relationship With Soil Nutrients

Pinus massoniana is a pioneer tree species in community succession in low mountain and hilly areas of southern China,accounting for 20% of the total afforestation area in China.Systematic study of nutrients in Pinus massoniana forest can not only reveal the material cycle mechanism of the ecosystem,but also play an important role in guiding forestry production,regulating and improving the environment for tree growth,improving the nutrient utilization rate of the system and improving the productivity of forest land.In this paper,a 45-year-old mature masson pine forest was selected as the research object.Twenty-three masson pine trees were covered with 20×20m experimental plots.In January 2018,samples of organs and soil layers under each masson pine tree were collected to determine the nutrient content and estimate the nutrient reserves.Mason pine litter was collected regularly every month to collect the litter.Categories(according to leaves,branches,propagules,other classifications)were dried and weighed to determine the nutrient content and calculate the amount of nutrient returned.In order to clarify the distribution characteristics of soil nutrients under masson pine forest,the distribution,demand and return status of soil nutrients under masson pine forest,the relationship between growth of Masson Pine and soil nutrients under forest,and the sustainable utilization time of soil under masson pine forest.In order to provide a theoretical basis for the sustainable management of Pinus massoniana forest,the regularity of nutrient distribution of Pinus massoniana and its relationship with soil nutrients were systematically and thoroughly understood.The main results are as follows:(1)the pinus massoniana forest land the forest of pinus massoniana forest land in the study area soil nutrient overall is in poor or very poor level(except total P,trace element),soil organic matter content in the medium level,total N,available N content at a lower level,total P content at high levels,available P,total K and available K content in a very low level.Soil nutrient content follows: organic matter >Fe>Ca> all P> all N> all K>Mg>Mn>Cu> fast acting N>Zn >fast acting K >fast acting P;Soil nutrient reserves follow: organic matter >Fe>Ca> all P> all N>Mg> all K>Mn>Cu>Zn> fast acting N >fast acting K > fast acting P.With the deepening of the soil layer,the nutrient content and reserves decreased gradually and increased in the soil layer of 60-70 cm.The vertical distribution of the contents of organic matter,total N,rapidly available N,rapidly available K,Mg,Fe,Mn,Zn and other nutrients in soil has obvious heterogeneity,while the vertical distribution of the contents of all P,fully available K,rapidly available P,Ca and Cu has no obvious heterogeneity.Horizontal distribution of each nutrient showed moderate intensity variation(50 to 60 cm soil layer of 60-70 cm soil available P,available K present a strong variability),organic matter,available P,available K,Ca,Mg and other elements in the horizontal direction of strong heterogeneity,followed by total N,available N,Cu and zinc,and total P,total K,Fe,Mn in horizontal heterogeneity is weak;The heterogeneity of organic matter,all P,all K,available N,available P,available K,Ca,Mg,Fe and other elements in the horizontal direction gradually decreases with the deepening of soil layer,while the heterogeneity of available P is on the contrary,and there is no obvious rule for all N,Cu and Zn.The distribution of organic matter,total N,and quick effect N had surface polymerization.The content of P in soil is not low,but the available P that can be absorbed and utilized by masson pine is very little.N,P,K,Ca,Cu,Zn and other elements are more likely to be leached to low-lying areas than other nutrients.(2)the contents of nutrients in different organs of masson pine reached extremely significant differences,with the largest difference being the content of N and the smallest being Cu.The contents and reserves of nutrient elements in the body follow: N>,Ca>,K>,Mg>,Fe>,P>,Mn>,Zn>,Cu.The contents of N,P,K,Mg,Mn and Zn were the highest in leaves,Ca and Cu in branches and Fe in roots.All nutrients in masson's pine were positively correlated(except N and Fe),and reached a significant or extremely significant correlation(except Fe and P,K,Ca,Mn).The nutrients in masson's pine basically promoted each other for absorption,reflecting the adaptation mechanism of masson's pine to barren soil.The growth of masson's pine is the result of the comprehensive effect of various nutrient elements.The content of P,K,Fe and other elements directly and significantly affects the growth of masson's pine,and the nutrient elements in masson's pine are all positively correlated(except N and Fe),and the correlation is significant or extremely significant(except Fe and P,K,Ca,Mn).(3)the litter amount of masson's pine was in the following order: leaf >,other > branches and > propagators.The litters were mainly leaves,accounting for 60.47% of the total litters.The main litters were from April to may,July to August and October to November,accounting for 51.9% of the total annual litters.From October to November,leaves have the largest amount of litter,which is 893.20 kg/hm2.From April to may,the branches had the largest litter,358.80 kg/hm2.The maximum amount of litters was 121.86 kg/hm2 in july-august.Other sundries,including bark,had the largest litter from July to August,which was 194.54 kg /hm2.These periods were also the main periods for nutrient return.K returned the most from April to may,mainly from fallen branches and other sundries.N,Ca,Fe and Cu returned the most in july-august,mainly from litters and other sundries including bark.P,Mg,Mn and Zn were returned most in October and November,mainly from pine needles.The sequence of nutrient content and amount returned of litter in masson pine was the same as that of all nutrients in masson pine,but the nutrient content in masson pine was higher than that of litter,which reflected the process of nutrient transport and migration from aging tissue to living tissue,and was a competitive strategy for masson pine to adapt to barren environment and utilize nutrients.The content of nutrient elements in each component follows the following pattern: other > leaves,> branches and > propagates,but the nutrient restitution is mainly in leaves and branches.The highest amount of Ca was returned from branches,leaves and other organs,and the highest amount of N was returned from propagates.There was also a difference in the time of concentrated return of nutrients in each component.For example,all nutrients in leaves were returned the most in October to November,while N,P,K,Mg,Fe and Mn in branches were returned the most in April to may,and Ca,Cu and Zn were returned the most in July to August.(4)in the next 300 years or so,Ca and K will be scarce in the forest land of masson's pine,and Mg and N will be scarce in the forest land in the next 600 years or so.The reasons for the deficiency of these nutrient elements are one or more of the reasons for the high growth demand,low nutrient return and low atmospheric nutrient input of masson's pine.Correlation analysis showed that the main factors affecting the DBH growth of masson's pine in soil nutrients were quick effect P,and the main factors influencing the height growth of masson's pine were soil organic matter,soil thickness,soil quick effect N,soil quick effect P,and soil Mg.Fe in soil is negatively correlated with organic matter,available N and available P,so high Fe content in soil is also a factor limiting the growth of masson's pine.(5)growth curve and nutrient demand curve of masson's pine can be seen that when the growth of tree height and DBH almost reaches a stable state,masson's pine still needs to continue to absorb nutrients from the soil for various physiological and biochemical activities.In about 70 years,the nutrients in masson's pine tend to balance.With the increase of tree age,DBH,growth of tree height and net nutrient reserve of masson pine showed an overall trend of rapid increase at first and then slow increase.At the stage of 0-25,soil fertility can maintain the growth of masson pine and the forest grows well.With the increase of pinus massoniana growth demand for nutrients,soil nutrient gradually decrease,affect the physical and chemical properties of soil of pinus massoniana forests and the changes of microbial community of pinus massoniana growth fell,but the growth rate is still faster,for nutrient demand is still on the rise,a decline in soil fertility,nutrient management is very important to the period of time.If masson pine continues to grow,the nutrients in the body gradually tend to balance,and the aboveground parts continuously return to the woodland,so as to alleviate the decline of soil fertility.If the mature masson pine forest is not felled and renewed,the soil in the forest land can basically maintain the existing fertility status.If the next generation of masson pine plantation forest is cultivated,the forest land will decline.(6)the higher the content of N,P,K and Ca in soil,the higher the content of corresponding nutrients in masson's pine.The higher the content of Mg,Fe,Mn,Cu and Zn in soil,the lower the content of corresponding nutrients in masson's pine.High content of N,P,K,Ca and Mg in masson pine would be more beneficial to the growth of masson pine.The growth of masson's pine is not only affected by soil nutrition,but also related to the size of the growth space.The smaller the space of nutrition,the worse the soil fertility,resulting in more intense intra-species competition,the worse the overall growth of masson's pine,and the more serious the polarization.