植物根系水力再分配模型参数分析与尺度转换

doi:10.17521/cjpe.2006.0124

摘要/Abstract

摘要：

植物根系水力再分配(Hydraulic redistribution)是近几年提出的对植物根系水力提升现象一种更准确的描述。Ryel等(2002)建立的根系水力再分配模型(以下简称Ryel模型)模拟结果表明根系水力再分配是土壤水分动态的一个重要组成部分。该文基于Ryel模型,对模型中涉及的重要参数进行敏感性分析,更准确地阐述参数变化下根系水力再分配模型的行为动态,从而定量分析环境及植物自身等因素对根系水力再分配的影响。Ryel模型时间尺度和土层厚度的设定限制了模型的应用,该文通过参数调整,将模型从时间尺度为小时、土层厚度均一转换到时间尺度为天、土层厚度不等,并应用到内蒙古皇甫川流域。

关键词: 根系水力再分配, 蒸腾, 根系分布, 尺度转换

Abstract:

Background and Aims Hydraulic redistribution (HR) is an extension of hydraulic lift. The simulation of hydraulic redistribution done by Ryel et al. (2002) indicated that HR is beneficial for transpiration.

Methods Based on the Ryel Model, we first conducted a sensitivity analysis by varying critical parameters of the model. We scaled the model for time steps of 1 hour to 1 day and soil from 10 cm to greater thicknesses by adjusting the necessary parameters. The scaled model was then applied to field observations of Caragana intermedia in Huangfuchuan Watershed of Inner Mongolia to simulate transpiration with and without HR. Daily changes in transpiration were simulated from April to October in 1998 and 1999.

Key Results and Conclusions The ratio of water redistributed by root to transpiration was strongly negative to soil hydraulic conductivity. The ratio also increased when root hydraulic conductivity increased, but gradually approached a limit. Total transpiration with HR increased when root hydraulic conductivity increased <1 cm·MPa ^-1·h^-1 and decreased when it increased >1 cm·MPa ^-1·h^-1. The result of the scaling indicates that it provides a useful approach to incorporating HR into larger models of soil processes. Total transpiration with HR increased 4.4% more than without HR in 1998, in contrast to total transpiration without HR having increased 2.1% more than with HR. This may be related to high precipitation in 1998.

Key words: Hydraulic redistribution, Transpiration, Root distribution, Scaling

王昆, 刘颖慧, 高琼, 莫兴国. 植物根系水力再分配模型参数分析与尺度转换. 植物生态学报, 2006, 30(6): 969-975. DOI: 10.17521/cjpe.2006.0124

WANG Kun, LIU Ying-Hui, GAO Qiong, MO Xing-Guo. PARAMETER ANALYSIS AND SCALING OF PLANT ROOT HYDRAULIC REDISTRIBUTION MODEL. Chinese Journal of Plant Ecology, 2006, 30(6): 969-975. DOI: 10.17521/cjpe.2006.0124

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2006.0124

https://www.plant-ecology.com/CN/Y2006/V30/I6/969

图/表 8

表1 模型中的参数

Table 1 Parameters of the model

参数名称 Parameters	符号 Symbol	数值 Value	单位 Unit
饱和容积含水量 Volumetric soil water content at saturation	θ_s	0.5	cm³·cm^-3
剩余容积含水量 Residual volumetric soil water content	θ_r	0.02	cm³·cm^-3
土壤饱和导水率 Soil hydraulic conductivity	K_s	0.247	cm·h^-1
全部活跃根系的最大径向导度 Root conductivity for water for all roots	C_RT	0.097	cm·MPa^-1·h^-1
根系导度降至50%时的土壤水势 Soil ψ/water potential where root conductivity reduced by 50%	ψ₅₀	-1.0	MPa
最大蒸腾速率 Maximum transpiration rate	E_RT_,max	1	cm·d^-1
形状指数 Shaping parameter	b	3.22
土壤水分特征曲线拟合参数 Fitting parameter for soil water retention curve	a	0.001 851	cm^-1
土壤水分特征曲线拟合参数 Fitting parameter for soil water retention curve	n	1.429 2

图1 100 d内日蒸腾变化模拟 a图摘自Ryel等(2002), b图是本文的结果

Fig.1 Daily transpiration simulated for 100-day a cited from Ryel et al.2002), b is the results of paper

图2 100 d内总蒸腾量以及水力再分配水量与总蒸腾量比值随根系导水率的变化

Fig.2 Total transpiration and ratio of water redistributed by roots to total transpiration for 100-day with root water conductance

图3 100 d内总蒸腾量以及水力再分配水量与总蒸腾量比值随根系导水率的变化

Fig.3 Total transpiration and ratio of water redistributed by roots to total transpiration for 100-day with root water conductance

表2 模型尺度转换时参数变化

Table 2 Parameter changes when scaling

参数名称 Parameters	原模型 Model	尺度转换后 Scaling
饱和水分导度 Soil hydraulic conductivity	0.247 cm·h^-1	0.247×24 cm·h^-1
根系的最大水分导度 Root conductivity for water for all roots	0.097 cm·MPa^-1·h^-1	0.097×24 cm·MPa^-1·h^-1
最大蒸腾速率 Maximum transpiration rate	1/24 cm·d^-1	1 cm·d^-1
根系水力再分配调节系数 Multiplier for day (1) or night (0)	1(10 h)~0(14 h)	10/24

图4 以天为时间尺度、不同厚度4个土层100 d的容积含水量、土壤水势与日蒸腾对比

Fig.4 Daily volume water content, soil water potential and daily transpiration for four different thicknesses of soil layers

图5 1998和1999年生长季模拟与实测月蒸腾量

Fig.5 Simulated monthly transpiration in 1998's and 1999's growing season

图6 模型模拟1998和1999年4到10月蒸腾日变化

Fig.6 Simulated daily transpiration from April to October in 1998 and 1999

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