基于根系发育分级的砂壤土下成熟林木根系构型分析

doi:10.17521/cjpe.2018.0269

摘要/Abstract

摘要：

基于根系发育分级标准分析不同等级根系的形态特征和各级根系的生长发育策略, 可以为未来成熟林木根系预测和模型构建提供参考。该研究以30多年生的两个毛白杨(Populus tomentosa)和一个刺槐(Robinia pseudoacacia)的根系系统为研究对象, 通过全挖法获取研究材料, 以Rose (1983)提出的发育分级标准作为根系分级标准, 分析了不同等级根系的基径、根长、连结长度、根系数量等形态特征以及不同等级根系间的拓扑关系。研究结果表明: 1) 3个根系系统的修正拓扑指数q_a、q_b均接近于0, 拓扑指数TI均接近于0.5, 说明3个根系系统均呈现叉状分支; 3个根系系统垂直分布最深达到5.7-6.4 m, 水平分布最长达到7.6-13.5 m; 同一树种根系存在连生关系。2) 3个根系系统能够分支到7-8级根; 一级根基径和长度显著高于后几级根, 一级根基径是后几级根的5.79-36.92倍, 一级根长度是后几级根的1.45-9.11倍; 根系数量随着根系等级增加先增后减, 在三级根上达到最大值。3)在前三级根中, 各级根上的连结长度从根基到根尖变化不大, 说明子级根在母级根上分布均匀, 能够充分高效地吸收土壤资源。4)母级根对子级根的基径拟合线性方程斜率, 一级根最小(平均斜率0.15), 二级根和三级根的斜率相差不大(平均斜率0.34、0.35), 说明一级根优先发育自身直径, 达到锚固和支撑的作用, 二、三级根则会优先发育子级根, 通过不断增强子级根以达到高效占领土壤空间的目的。5)基径对长度的拟合线性方程斜率随着根系等级增加而增加(平均斜率从10.46增长至90.43), 说明高级别根系会倾向于发展根系长度来达到探索资源、拓展空间的目的。

关键词: 发育分级标准, 根系分级, 根系构型, 成熟林木, 砂壤土

Abstract: Aims

Understanding the differences in root architectural strategies among the species and the differences in morphological characteristics among different root orders will facilitate our understanding root growth and development strategies, and thus provide a basis for predicting and modeling the root systems for mature trees. In this study, we analyzed the morphological characteristics and topological relationships for the root systems of two Populus tomentosa trees and one Robinia pseudoacacia tree.

Methods

A method combining both excavation and analysis was applied to extract and quantify root architectural characteristics of the three root systems. The morphological characteristics such as root basal diameter, root length, link length, and root number of different root orders were described using the developmental analysis method of Rose (1983), and their topological relationships were analyzed.

Important findings

1) The modified topological indices q_a and q_b were close to 0, and the topological index TI was close to 0.5 for all three root systems, indicating their dichotomous structure. The depth and width of the systems ranged from 5.7 to 6.4 m and from 7.6 to 13.5 m, respectively. Root grafts occurred in the same species. 2) The root systems could have the seventh or eighth order roots. The basal root diameter and root length significantly decreased with increasing root order. The first order roots had 5.79-36.92 times the basal diameter and 1.45-9.11 times the length of higher order roots. With increasing root order, the root number increased, and reached a maximum value for the third order roots, and then decreased. 3) In roots of each of the first three orders, the link length varied little from the root base towards its tip, indicating that the child roots were distributed evenly on their parent roots and thus help trees absorb soil resources more efficiently. 4) The regression of basal diameters of child roots on basal diameters of their mother roots showed that the smallest slope for the first order roots (average slope 0.15) and no big difference in the slope between the second and third order roots (0.34 versus 0.35). This suggested that the first order roots developed their own diameter first for anchoring and supporting the tree, while the second and third order roots developed their child roots to facilitate nutrient uptake from the soil. 5) The regression of root length on root basal diameter suggested that the slope increased from 10.46 to 90.43 with increasing root order, which implies that the higher order roots tended to develop their length to explore resources and expand their space.

Key words: developmental classification standard, root system classification, root architecture, mature tree, sandy loam soil

祝维, 余立璇, 赵德海, 贾黎明. 基于根系发育分级的砂壤土下成熟林木根系构型分析. 植物生态学报, 2019, 43(2): 119-130. DOI: 10.17521/cjpe.2018.0269

ZHU Wei, YU Li-Xuan, ZHAO De-Hai, JIA Li-Ming. Architectural analysis of root systems of mature trees in sandy loam soils using the root development classification. Chinese Journal of Plant Ecology, 2019, 43(2): 119-130. DOI: 10.17521/cjpe.2018.0269

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2018.0269

https://www.plant-ecology.com/CN/Y2019/V43/I2/119

图/表 9

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林型 Stand type	树种 Tree species	平均胸径 Average DBH (cm)	平均树高 Average tree height (m)	株行距 Plant & row spacing (m)	平均冠幅 Average crown width (m)	间伐措施 Thinning treatment
毛白杨纯林 Populus tomentosa stand	毛白杨 P. tomentosa	36.1	35.5	6 × 6	7.0	造林后第十年间伐除去刺槐, 以前的混交林成为现有纯林 All R. pseudoacacia trees were removed from mixed-species stand after 10 years of planting, resulting in P. tomentosa pure stand
毛白杨×刺槐混交林 Mixtures with P. tomentosa and Robinia pseudoacacia	毛白杨 P. tomentosa	37.0	26.4	3 × 6	6.6	无 None
毛白杨×刺槐混交林 Mixtures with P. tomentosa and R. pseudoacacia	刺槐 R. pseudoacacia	25.1	21.1	3 × 6	8.6	无 None

林型 Stand type	树种 Tree species	平均胸径 Average DBH (cm)	平均树高 Average tree height (m)	株行距 Plant & row spacing (m)	平均冠幅 Average crown width (m)	间伐措施 Thinning treatment
毛白杨纯林 Populus tomentosa stand	毛白杨 P. tomentosa	36.1	35.5	6 × 6	7.0	造林后第十年间伐除去刺槐, 以前的混交林成为现有纯林 All R. pseudoacacia trees were removed from mixed-species stand after 10 years of planting, resulting in P. tomentosa pure stand
毛白杨×刺槐混交林 Mixtures with P. tomentosa and Robinia pseudoacacia	毛白杨 P. tomentosa	37.0	26.4	3 × 6	6.6	无 None
毛白杨×刺槐混交林 Mixtures with P. tomentosa and R. pseudoacacia	刺槐 R. pseudoacacia	25.1	21.1	3 × 6	8.6	无 None

		纯林毛白杨 Populus tomentosa in pure stand		混交林毛白杨 P. tomentosa in mixed stand		混交林刺槐 Robinia pseudoacacia in mixed stand
	追踪根系编号 Code of the tracked roots	距离/深度 Distance/ depth (m)	终点状态 End state	距离/深度 Distance/ depth (m)	终点状态 End state	距离/深度 Distance/ depth (m)	终点状态 End state
水平根 Lateral root	1	3.3	萌生幼树 Sapling from root sprouting	8.6	与邻株连生 Root grafted with neighbor tree	6.5	垂直向下生长 Vertically downward growth
	2	5.1	与邻株连生 Root grafted with neighbor tree	11.1	分叉 Branching	8.2	分叉 Branching
	3	6.1	垂直向下生长 Vertically downward growth	13.5	垂直向下生长 Vertically downward growth	8.5	垂直向下生长 Vertically downward growth
	4	6.4	垂直向下生长 Vertically downward growth
	5	7.6	垂直向下生长 Vertically downward growth
垂直根 Vertical root	1	3.1	到头, 末端直径0.3 mm To the end, root tip diameter 0.3 mm	4.0	到头, 末端长瘤 To the end, with tumor	2.7	竖直向上生长 Vertically upward growth
	2	4.3	到头, 末端直径0.3 mm To the end, root tip diameter 0.3 mm	4.3	到头, 末端直径0.5 mm To the end, root tip diameter 0.5 mm	3.7	到头, 末端直径0.3 mm To the end, root tip diameter 0.3 mm
	3	5.7	到头, 末端直径0.25 mm To the end, root tip diameter 0.25 mm	4.3	到头, 末端直径0.76 mm To the end, root tip diameter 0.76 mm	5.9	到头, 末端直径0.02 mm To the end, root tip diameter 0.02 mm
	4			6.4	向西转弯 Bend to the west

		纯林毛白杨 Populus tomentosa in pure stand		混交林毛白杨 P. tomentosa in mixed stand		混交林刺槐 Robinia pseudoacacia in mixed stand
	追踪根系编号 Code of the tracked roots	距离/深度 Distance/ depth (m)	终点状态 End state	距离/深度 Distance/ depth (m)	终点状态 End state	距离/深度 Distance/ depth (m)	终点状态 End state
水平根 Lateral root	1	3.3	萌生幼树 Sapling from root sprouting	8.6	与邻株连生 Root grafted with neighbor tree	6.5	垂直向下生长 Vertically downward growth
	2	5.1	与邻株连生 Root grafted with neighbor tree	11.1	分叉 Branching	8.2	分叉 Branching
	3	6.1	垂直向下生长 Vertically downward growth	13.5	垂直向下生长 Vertically downward growth	8.5	垂直向下生长 Vertically downward growth
	4	6.4	垂直向下生长 Vertically downward growth
	5	7.6	垂直向下生长 Vertically downward growth
垂直根 Vertical root	1	3.1	到头, 末端直径0.3 mm To the end, root tip diameter 0.3 mm	4.0	到头, 末端长瘤 To the end, with tumor	2.7	竖直向上生长 Vertically upward growth
	2	4.3	到头, 末端直径0.3 mm To the end, root tip diameter 0.3 mm	4.3	到头, 末端直径0.5 mm To the end, root tip diameter 0.5 mm	3.7	到头, 末端直径0.3 mm To the end, root tip diameter 0.3 mm
	3	5.7	到头, 末端直径0.25 mm To the end, root tip diameter 0.25 mm	4.3	到头, 末端直径0.76 mm To the end, root tip diameter 0.76 mm	5.9	到头, 末端直径0.02 mm To the end, root tip diameter 0.02 mm
	4			6.4	向西转弯 Bend to the west

根系系统 Root system	a (A)	P_e	V₀ (M)	b	q_a	q_b	TI
纯林毛白杨 Populus tomentosa in pure forest	29	8 367	793	10.551	0.02	-0.000 2	0.50
混交林毛白杨 P. tomentosa in mixed forest	61	21 322	1 456	14.644	0.03	0.004 0	0.56
混交林刺槐 Robinia pseudoacacia in mixed forest	21	3 990	465	8.581	0.02	-0.006 0	0.50