杉木伐桩活细根活力、非结构性碳含量及其碳氮磷化学计量变化特征

Changes of activity,non-structural carbon content,and carbon,nitrogen,and phosphorus stoichiometry in live fine roots of Chinese fir stumps

伐桩(stump)是森林经营过程中人工采伐剩余物,长期存在于森林生态系统中,其在水土保持、碳(C)吸收以及森林更新方面发挥的生态功能已受到关注,但伐桩活细根的活力,以及非结构性碳水化合物(NSC)和C、氮(N)、磷(P)含量随时间的如何变化尚不清楚.以湖南省临武县2014-2022年国家储备林建设期间产生的杉木(Cunninghamia lanceolata)伐桩为研究对象,采用空间换时间的方法,分析活细根的活力、NSC以及C、N、P含量随时间的变化规律,探讨其产生原因.结果显示:(1)随伐桩存留时间的延长,细根C含量在第一年显著上升,之后整体呈现下降趋势,从采伐第一年(2022年)到第9年(2014年)下降了10.06%;而N和P含量在第一年有所下降,随后逐年上升,直到第9年(2022年)分别增加了70.06%和103.03%;(2)杉木伐桩细根根系活力在采伐后的9年内仍较强,活力值介于92.34-113.22μg g^(-1)h^(-1)之间,整体呈现缓慢下降趋势;(3)杉木伐桩活细根NSC含量变化不显著,维持在228.59-267.65 mg/g之间.本研究表明杉木采伐9年后,伐桩活细根仍然保持较强的活力,能够持续从土壤中吸收N和P并将其储存于细根内,导致这些元素含量逐年上升;NSC总含量的稳定性可能暗示杉木伐桩细根NSC含量需要保持在一定阈值范围内,以维持根系的活力并使其在土壤中存活更长时间.(图3表1参50)

As residues of artificial harvesting during forest management,stumps have existed in forest ecosystems for a long time,and their ecological functions in soil and water conservation,carbon sequestration,and forest regeneration have received considerable attention.However,it is not clear how the activity of live fine roots in logged stumps,as well as non-structural carbon(NSC),carbon(C),nitrogen(N),and phosphorus(P)content change over time.In this study,we took the Chinese fir stumps generated during the construction of the national reserve forest from 2014 to 2022 in Linwu County,Hunan Province,as the research object,and analyzed the variation rules of the activity,NSC,and C,N,and P contents of living fine roots over time by adopting the method of space-for-time to explore the reasons for their generation.The results showed that(1)fine root-C content increased significantly in the first year with the prolonged survival time of the logged piles and then showed an overall decreasing trend,decreasing by 10.06% from the first year(2022)to the 9th year(2014)of logging,while N and P content decreased in the first year and then increased year by year until the 9th year(2022),increasing by 70.06% and 103.03%,respectively;(2)Root activity of fine roots of Chinese fir stumps was still strong 9 years after felling,and its activity value ranged between 92.34 to 113.22μg g^(-1) h^(-1),showing a slow decline trend.(3)There was no significant change in the NSC content of live fine roots of Chinese fir stumps,which remained between 228.59 to 267.65 mg/g.This study showed that nine years after harvesting,the active fine roots of Chinese fir maintained strong vitality and continuously absorbed N and P from the soil and store them in the fine roots,resulting in an annual increase in the content of these elements.The stability of the total NSC content suggests that the NSC content of fine roots of Chinese fir stump posts needs to be maintained within a certain threshold range to maintain the vitality of the roots and allow them to survive for extended periods of time in the soil.