Cheng Song
Department of Biology, Groupe de Recherche en Ecologie Forestière Interuniversitaire (GREFi), Concordia University, 7141 Sherebrooke Street West, Montréal, Québec, Canada H4B 1R6.
J Theor Biol. 2007 May 21;246(2):309-22. doi: 10.1016/j.jtbi.2006.12.026. Epub 2006 Dec 28.
Total 66 small (<50m(2)), 24 medium (101-200m(2)) and 36 large (201-500m(2)) canopy gaps at the three sites of yellow birch (Betula alleghaniensis Britton) and sugar maple (Acer saccharum Marsh) forests were established in southern Québec, Canada. Half of the gaps were covered by 8x8m(2) shading cloths to mimic a closed canopy. From these gaps, 46 understory yellow birch and 46 sugar maple saplings with different tree ages and sizes were sampled. Single- and multi-variable linear and nonlinear models of root biomass and traits (root surface area, volume, length and endings) were developed and examined. Lorentzian model as a multi-variable nonlinear model was firstly applied to the simulations using both base diameter and height, and performed the best fit to total root biomass in both species with the highest correlation coefficients (R(2)=0.96 and 0.98) and smallest root mean squared deviations (RMSD=7.85 and 7.02) among all the examined models. The model also accurately simulated small fine root (2.0mm in diameter), coarse fine root (>2.0-5.0mm) and coarse root (>5.0mm) biomass (R(2)=0.87-0.99; RMSD=2.24-6.41), and the root traits (R(2)=0.71-0.99; RMSD=0.19-19.38). The study showed yellow birch roots were longer, larger, had more endings (tips) and grew faster than sugar maple roots. The root traits were largely distributed to small fine roots, sharply decreased from small fine roots to coarse fine roots, the fewest in coarse roots except for root volume. When trees were large, coarse root biomass increased more rapidly than fine root biomass, but vise versa when the trees were small.
在加拿大魁北克省南部的黄桦（Betula alleghaniensis Britton）和糖枫林三个地点，建立了66个小（<50平方米）、24个中（101 - 200平方米）和36个大（201 - 500平方米）的林冠空隙。一半的空隙用8×8平方米的遮阳布覆盖，以模拟封闭的林冠。从这些空隙中，选取了46株不同树龄和大小的林下黄桦和46株糖枫树苗。建立并检验了根生物量和性状（根表面积、体积、长度和末梢）的单变量和多变量线性及非线性模型。洛伦兹模型作为多变量非线性模型，首次用于同时使用基径和树高的模拟，在所有检验模型中，与两个物种的总根生物量拟合最佳，相关系数最高（R² = 0.96和0.98），根均方根偏差最小（RMSD = 7.85和7.02）。该模型还准确模拟了细根（直径2.0毫米）、粗细根（>2.0 - 5.0毫米）和粗根（>5.0毫米）的生物量（R² = 0.87 - 0.99；RMSD = 2.24 - 6.41）以及根性状（R² = 0.71 - 0.99；RMSD = 0.19 - 19.38）。研究表明，黄桦的根更长、更大，末梢更多，生长速度比糖枫的根快。根性状主要分布在细根上，从细根到粗细根急剧减少，粗根中除根体积外最少。当树木较大时，粗根生物量比细根生物量增加得更快，但树木较小时则相反。
