Complex branching and irregular foliage distribution render the quantitative description of tree crowns a scientific and technological challenge. This study explores the use of fractal geometry to describe crowns. Based on the derivation of a classical model-the Sierpinski tetrahedron-a new method we call comprehensive structural relationships (CSR) is described for estimating fractal dimensions in 3-D space. All possible structural relationships were examined under the scale transformation and space expansion modes, resulting in 15 structural relationships. The method was applied to a deciduous species to describe structural characteristics of branching and foliage distribution. Results demonstrate that it is practical to estimate fractal dimensions of tree crowns in the field.Keywords: fractal geometry, branching, foliage distribution, structural relationships RÉSUMÉ L' étalement complexe des branches et la distribution irrégulière du feuillage font en sorte que la description quantitative de la cime des arbres devient un défi scientifique et technologique. Cette étude explore l'utilisation de la géométrie fractale pour effectuer la description des cimes. À partir de la dérivation d'un modèle classique -le tétraèdre de Sierpinski -une nouvelle méthode que nous intitulons les relations structurelles globales (RSG) est définie pour estimer les dimensions fractales dans un espace à trois dimensions. Toutes les relations structurelles possibles ont été étudiées en fonction du changement d' échelle et de l'agrandissement de l' espace, ce qui a permis la création de 15 relations structurelles. La méthode a été appliquée dans le cas d' espèces feuillues afin de décrire les caractéristiques structurelles de l' étalement des branches et de la distribution du feuillage. Les résultats indiquent qu'il est possible d'estimer les dimensions fractales de la cime des arbres sur le terrain.

To understand carbon source characteristics of soil respiration, a trench method was used to control carbon inputs (control treatment: CK, no litter treatment: NL, no root treatment: NR, and no litter and no root treatment: NLNR) in a Platycladus orientalis (L.) Franco plantation, so that soil respiration, temperatures and moisture content could be analyzed. Results indicate that different carbon inputs created no significant variance in soil temperatures and moisture content (P>0.05), whereas soil respiration was significantly influenced (P<0.01). During the measurement period, mean soil respiration of CK, NL, NR and NLNR were 3.69, 1.41, 3.11, and 1.99 μmol/m 2 /s, respectively. Soil respiration was reduced by 36.28 ±5.79%, 15.25 ±2.62% and 25.53 ±4.95% in the NL, NR and NLNR treatments, respectively. The proportions of mineral soil, litter and root respirations were 40.95%, 46.91% and 12.14%, respectively. Different carbon inputs caused no significant R 2 variance in the temperature index model or in the temperature-water combined model. These results provide guidelines for investigating Platycladus orientalis ecosystem carbon emissions, as well as carbon input and output balance, and the role of soil respiration in the carbon cycle.