| Variations in tree’s heartwood and sapwood, mainly including circumferential and axial variations, affect physiological and mechanical functions of the trunk. We harvested all the trees within a 15 m × 20 m plot of a 48-year-old Larix gmelinii plantation with the aim of quantifying the spatial variation in stem and branch heartwood and sapwood influenced by the differentiation of stand individuals, and exploring the relationship between the variation and other tree traits. We used a hierarchical clustering analysis to divide the differentiation into three classes, e.g. dominant, intermediate and suppressed trees. The result were followed.(1) Differentiation class, direction, and disc height had a significant impact on the spatial variation in heartwood radius (HR) and sapwood width (SW; P< 0.001). The HR and SW and their absolute variations increased significantly from the suppressed to the intermediate and to the dominant. The maximum value of heartwood to sapwood ratio (HSR) occurred most frequently in the north direction (17.65%), while the minimum value occurred in south direction (17.68%), reflecting the difference in the microsite. The absolute variation in HR decreased with increasing relative height, while that in SW remained relatively constant up to the height of the first living branch after which it declined. The relative variations in HR and SW did not change axially. The absolute axial variations in HR or SW were the greatest for the dominant trees, followed by the intermediate, and the least for the suppressed, while the relative variations exhibited non-consistent patterns. The absolute variation in HR or SW was positively correlated with the diameter at breast height. The area of heartwood or sapwood was positively correlated with the projected area of crown or root, branch biomass, foliage biomass, or root biomass, among which is correlated most tightly with the branch or foliage biomass.(2) Differentiation class, direction, and crown position had a significant impact on the spatial variation in branch HR and SW (P< 0.001). The HR and SW and their absolute variations in DB10 and DBS increased significantly from the suppressed to the intermediate and to the dominant. The maximum variation occurred in west direction,reflecting the difference in the microsite.Except for the DB10 of the suppressed, HRAV and SWAV decreased with increasing crown position. HRRV and SWRV did not change axially. The absolute axial variations in HR or SW were the greatest for the dominant trees, followed by the intermediate, and the least for the suppressed, while the relative variations exhibited non-consistent patterns. The absolute variation and width in HR or SW was positively correlated with the branch biomass,foliage biomass, branch base diameter, branch length and so on. Among these patters which is correlated most tightly is the branch base diameter.We concluded that the heartwood and sapwood of the larch showed significant variations both circumferentially and axially, of which the absolute variation was significantly influenced by stand tree differentiation, but the relative variation was insensitive to the differentiation. In this study, two levels from single trees and tree-like trees circumferential and axial elaborate on its heartwood and sapwood spatial variability, and to study the impact of the main factors, summarized the law of variation. In this study, biomass carbon stocks, productivity, carbon allocation evaluation and estimation, trees transpiration water consumption as well as to evaluate and estimate reveals growth characteristics and physiological functions of trees and their impact factors provide an important basis for scientific management and utilization of mountain cap children the main tree species in the forest area of larch provided a scientific basis and the data base. |
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