Internal Circulation Of Nutrient Elements In Chinese Fir Of Different Stand Ages

Nutrient cycling in plants is an important part of nutrient cycling in forests.In this paper,we take Cunninghamia lanceolata as the research object,and use the biomass and nutrient data of Cunninghamia lanceolata located in a Chinese fir forest for 25 consecutive years.In this paper,the biomass of tree organs alive at the beginning of a stand age and alive at the end of this stand age is called "alive organs" biomass.The biomass of"surviving organs" in a stand age segment was calculated according to the biomass of living tree organs at the beginning of a stand age segment and the growth cycle of the organs.The nutrient reabsorbed or transferred from"surviving organs" of a stand age segment was estimated according to the biomass of "surviving organs" of a stand age segment and the difference in nutrient concentration of tree organs at the beginning and end of a stand age segment.Different forest age at the time of branches and leaves to live before dying organ of a component with different forest age branches and leaves of water quantity and the different forest age living branches and leaves and dead branches and leaves of nutrient concentration difference estimation and other research methods,studied in conjunction with fir branches before dying to live organ metastasis and nutrient organs "still alive" nutrient transfer within two growing objects in nutrient cycle and the process of change with old rule,The results are as follows.(1)Most of the nutrients transferred from branches and leaves of Cunninghamia lanceolata forest before dieback were transferred from leaves.Before 20 years old,nutrient transfer increased with age and decreased with age after 20 years old.The translocation of N,K,P and Ca before shoot and leaf death increased with stand age,and the translocation of Mg increased first and then decreased with stand age.The amount of N and K transferred before leaf death was much more than P,Ca and Mg.(2)Nutrient transfer rates of 1-25 years old Cunninghamia lanceolata before leaf death ranged from 22.99%to 26.06%.The nutrient transfer rate before shoot death ranged from 21.64%to 22.59%,which all increased with the increase of stand age.The nutrient transfer rate of leaves is higher than that of branches in the same stand age section.Except for 1-7 years of age,there was no significant difference in the nutrient transfer rate of branches(or leaves)in each age section(P>0.05),and stand age had little effect on the nutrient preservation capacity of branches and leaves of C.The nutrient transfer rate of leaves before 16 years of stand growth was K>P>N>Mg>Ca.After 16 years of birth,P>K>N>Ca>Mg.Nutrient element transfer rate K bB0 P bB1 N bB2 Mg bB3 Ca at 8 to 25 years of age in different stand stages before branch death.The transfer rate of P was higher than that of N,which indicated that P was the main nutrient limiting the growth of C.(3)From young forest to rapid growth stage,nutrients were transferred to "surviving organs";When the tree reaches the mature stage,the nutrients of the "surviving organs" are transferred outwards.Transferred into"surviving organs" trophic components:leaves>branches>bark>trunks>roots;The amount of elements transferred into:N>Ca>K>Mg>P.Transferred trophic weight of "surviving organs":trunk>branches>roots>leaves>bark;The amount of elements transferred:Ca>N>K>Mg>P.The amount of nutrients(elements)transferred into the "still alive organs" was greater than that transferred out of the corresponding "still alive organs".At the same stand age,there were significant differences in the amount of nutrient elements transferred into or out of the "still alive organs"(P<0.05).(4)Nutrient transfer from each organ changed with stand age,and the nutrient transfer amount of "surviving leaves" decreased with stand age.Before 20 years old,the number of surviving trunks,bark,branches and roots increased with the increase of stand age,and the increasing rate was as follows:bark>trunk>branch>root;After 20 years of growth,it decreased with the increase of stand age,and the rate of decline was:branch>,root>,bark>trunk.Before 20 years of stand growth,nutrient element transfer increased with the increase of stand age,and the increasing rate was P>Ca>N>K>Mg.The rate of decrease was Mg>,P>,K>,N>,Ca.The amount of nutrient elements transferred from surviving leaves decreased with the increase of stand age.The element transfer of "surviving branches" increased with the increase of stand age before 20 years,but decreased with the increase of stand age after 20 years.The translocation of N,Ca in "surviving trunk" and P,Mg in "surviving bark" increased with the increase of stand age.The K and Mg translocations of "surviving roots" and"surviving bark" decreased with the increase of stand age.The translocations of P,K,Mg in the surviving trunks and N,P,Ca in the surviving roots increased first and then decreased with the increase of stand age.(5)Nutrient transfer rate into the "still alive organs":leaf>,branch>,bark>,trunk>,root.Nutrient transfer rate from "surviving organs":trunk>,root>,branch>,leaf>,bark.The rate of nutrient transfer to "surviving leaves,branches and bark" was higher than that of nutrient transfer from these organs.The rate of nutrient transfer into "surviving trunks and roots"was lower than the rate of nutrient transfer out of these organs.The rate of nutrient transfer from the surviving organs decreased with the age of the stand,the rate of nutrient transfer from the living trunks,bark and roots increased with the age of the stand,and the rate of nutrient transfer from living leaves and branches decreased with the age of the stand.The transfer rate of nutrient elements into the "surviving organs":P>Mg>N>K>Ca;The order of the transfer rate of elements from the surviving organs was:P>Mg>Ca>K>N.The transfer rates of N,P,Ca and Mg from surviving branches,leaves and bark decreased with the increase of stand age.The number of "surviving trunks and roots" increased first and then decreased with the increase of stand age.The transfer rate of K in "surviving branches,trunks and roots" increased first and then decreased with the increase of stand age.In the "surviving leaves,bark" decreased with the increase of stand age.(6)At any stage of stand age,the amount of nutrient transferred from branches and leaves before death was much more than that transferred to or from the "surviving organs".The amount of each element transferred was somewhat different between the two types of nutrient internal circulation.The amount of N and K transferred out(or into)of the"surviving organs" was less than that transferred before the death of the branches and leaves.The amount of Mg transferred out(or into)from the"surviving organs" was greater than that transferred before the death of branches and leaves.The amount of Ca and P transferred from 8 to 11 years old stand to "surviving organs" was greater than that transferred from before the death of branches,and the amount of Ca and P transferred from"surviving organs" from 12 to 25 years old stand was less than that transferred from"surviving organs" before the death of branches.At any age,the rate of nutrient transfer into or out of the surviving organs was much less than that before leaf death.In terms of nutrient protection and utilization and nutrient cycling function of plant organs,the nutrient transfer before death of plant organs is much more than that of "still alive organs".(7)Nutrient transfer amount(element transfer rate)and its change with stand age were mainly controlled by physiological characteristics of branches and leaves(growth cycle),growth characteristics of trees at different growth and development stages(yield of branches and leaves),and nutrient concentration difference before and after branch and leaves death at different age stages.The nutrient(element)transfer amount(or transfer rate)of "surviving organs" varies with stand age,which is not only affected by the physiological function of each organ of trees,but also controlled by the developmental characteristics of trees at different growth stages and the nutrient demand of each organ productivity,as well as the difference of nutrient con centration in the body of trees at different age stages.And the mobility of elements in plants and their compactness in organic structures.