Determination of seasonal dynamics of leaf area index in the Pinus massoniana forest
[Objective]Evaluate the accuracy of the leaf area index(LAI)of Pinus massoniana by optical instrumentation to provide technical support for accurately monitoring the LAI seasonal dynamics of P.massoniana forest.[Method]We evaluated the seasonal dynamics of LAI estimated by leaf-spreading surveys,the anisotropic growth equation method,the apomictic method,and optical instrumental methods(hemispherical photography and the LAI-2200 plant canopy analyser)in the P.massoniana forest by using the apomictic method measured values as representative of the true LAI values of P.massoniana forest,and we considered the sources of error of the LAI determined by the optical instrumental methods(clumping index(ΩE),woody-to-total area ratio(α),and needle-cluster ratio(γE)).[Result]The mean leaf lifespan of the major species within the P.massoniana forest ranged from 1.53 to 1.94,and SLA varied widely(99.15 cm2/g-278.33 cm2/g).The seasonal dynamics of LAI in P.massoniana forests determined by different methods showed a single-peak change pattern,and reached a peak in July.In each period,there was no significant difference between the value determined by litterfall method and allometry method.During the entire investigation period,the effective leaf area index(Le)measured by DHP was underestimated by 49%-64%and 47%-61%,respectively,compared with the values measured by litterfall method and allometry method.Le measured by LAI-2200 underestimates 25%-44%and 20%-42%,respectively.The accuracy of Le measured by DHP was obviously improved after corrected by automatic exposure,α,ΩE and γE.Compared with litterfall method and allometry method,the accuracy was average underestimated by 8%and 5%.Generally speaking,after corrected by α,ΩE and γE,the accuracy of LAI-2200 was greatly improved,compared with litterfall method and allometry method,it was underestimated by an average of 6%and 2%,respectively.[Conclusion]After considering the factors that affect the determination of LAI by optical instrument method,the accuracy of LAI measured by DHP and LAI-2200 methods had been significantly improved,indicating that both optical instrument methods can accurately determine the seasonal dynamics of LAI in P.massoniana forest and can provide a methodological reference for the study of seasonal dynamics of LAI in P.massoniana forests in different regions.
NETL
NSTL
万方数据
