Modelling Soil Water Retention for Weed Seed Germination Sensitivity to Water Potential

Table 2

Average fitted parameter and AIC values for the soil water retention models across hillslopes.

Hillslope position		Average parameter values (SE)						AIC^g
𝜃𝑟  derivation	Model	𝜃𝑠^a	𝜃𝑟^b	𝑃1^c	𝑃2^d	𝑃3^e	𝑃4^f
		(cm^3/cm^3)		(MPa)		(dimensionless)
Summit		0.379
Absent	CA		0.000 (—)	−0.0022 (0.0006)	—	3.29 (0.34)	—	−27.6
Measured	BC		0.065 (—)	−0.0042 (0.0006)	—	0.60 (0.05)	—	−28.5
	VG5		0.065 (—)	—	−0.0042 (0.0006)	11.14 (0.04)	0.054 (0.005)	−26.5
	VG4		0.065 (—)	—	−0.0053 (0.0010)	1.65 (0.07)	—	−28.1
	TA		0.065 (—)	—	−0.0115 (0.0035)	—	—	−11.1
	RU		0.065 (—)	−0.0011 (<.0001)	—	16.66 (5.07)	—	−13.5
Modified	BC		0.064 (0.011)	−0.0042 (0.0008)	—	0.69 (0.16)	—	−30.1
	VG5		0.064 (0.008)	—	−0.0042 (<.0001)	11.83 (<.01)	0.059 (0.006)	−28.1
	VG4		0.066 (0.011)	—	−0.0053 (0.0012)	1.79 (0.20)	—	−29.4
	TA		0.088 (0.005)	—	−0.0055 (0.0007)	—	—	−24.1
	RU		0.087 (0.005)	−0.0011 (<.0001)	—	5.43 (1.40)	—	−24.5
Estimated	BC		0.051 (0.015)	−0.0037 (0.0007)	—	0.51 (0.10)	—	−29.4
	VG5		0.051 (0.011)	—	−0.0037 (<.0001)	11.05 (<.01)	0.046 (0.004)	−27.4
	VG4		0.055 (0.015)	—	−0.0048 (0.0012)	1.58 (0.13)	—	−28.5
	TA		0.106 (0.014)	—	−0.0070 (0.0019)	—	—	−15.6
	RU		0.098 (0.015)	−0.0011 (<.0001)	—	9.93 (4.11)	—	−16.8
Backslope		0.391
Absent	CA		0.000 (—)	−0.0023 (0.0004)	—	3.61 (0.23)	—	−32.1
Measured	BC		0.073 (—)	−0.0040 (0.0006)	—	0.54 (0.04)	—	−28.8
	VG5		0.073 (—)	—	−0.0040 (0.0006)	21.21 (0.05)	0.025 (0.002)	−26.8
	VG4		0.073 (—)	—	−0.0053 (0.0009)	1.59 (0.06)	—	−29.4
	TA		0.073 (—)	—	−0.0140 (0.0008)	—	—	−10.2
	RU		0.073 (—)	−0.0011 (<.0001)	—	20.87 (6.05)	—	−12.8
Modified	BC		0.061 (0.014)	−0.0034 (0.0006)	—	0.51 (0.10)	—	−33.6
	VG5		0.061 (0.010)	—	−0.0034 (<.0001)	9.68 (<.01)	0.052 (0.005)	−31.6
	VG4		0.066 (0.009)	—	−0.0044 (<.0001)	1.58 (0.06)	—	−32.9
	TA		0.102 (0.006)	—	−0.0055 (0.0009)	—	—	−21.9
	RU		0.100 (0.007)	−0.0011 (<.0001)	—	5.57 (1.94)	—	−22.5
Estimated	BC		0.042 (0.015)	−0.0032 (0.0005)	—	0.39 (0.06)	—	−33.3
	VG5		0.042 (0.011)	—	−0.0032 (<.0001)	9.38 (<.01)	0.042 (0.003)	−31.3
	VG4		0.049 (0.011)	—	−0.0042 (<.0001)	1.45 (0.03)	—	−32.3
	TA		0.120 (0.018)	—	−0.0078 (0.0031)	—	—	−13.6
	RU		0.108 (0.019)	−0.0011 (<.0001)	—	13.00 (5.66)	—	−15.4
Toeslope		0.417
Absent	CA		0.000 (—)	−0.0014 (0.0003)	—	5.63 (0.30)	—	−34.5
Measured	BC		0.120 (—)	−0.0030 (0.0009)	—	0.41 (0.06)	—	−23.3
	VG5		0.120 (—)	—	−0.0030 (0.0009)	19.63 (0.33)	0.021 (0.003)	−21.3
	VG4		0.120 (—)	—	−0.0039 (0.0013)	1.44 (0.07)	—	−24.0
	TA		0.120 (—)	—	−0.0177 (0.0057)	—	—	−8.1
	RU		0.120 (—)	−0.0011 (<.0001)	—	29.02 (10.26)	—	−10.5
Modified	BC		0.000 (—)	−0.0014 (0.0003)	—	0.18 (0.01)	—	−32.5
	VG5		0.000 (—)	—	−0.0014 (<.0001)	14.34 (0.24)	0.012 (<.001)	−30.5
	VG4		0.000 (—)	—	−0.0016 (<.0001)	1.18 (<.01)	—	−32.8
	TA		0.149 (0.005)	—	−0.0039 (0.0008)	—	—	−23.4
	RU		0.149 (0.005)	−0.0011 (<.0001)	—	2.35 (1.23)	—	−23.4
Estimated	BC		0.000 (—)	−0.0014 (0.0003)	—	0.18 (0.01)	—	−32.5
	VG5		0.000 (—)	—	−0.0014 (<.0001)	14.45 (1.64)	0.012 (0.001)	−30.5
	VG4		0.000 (—)	—	−0.0016 (<.0001)	1.18 (<.01)	—	−32.8
	TA		0.182 (0.020)	—	−0.0065 (0.0019)	—	—	−11.3
	RU		0.162 (0.028)	−0.0011 (<.0001)	—	15.39 (10.95)	—	−12.4

^a𝜃_𝑠 is measured saturation water content.
^b𝜃_𝑟 is residual water content.
^c𝑃₁ is the air entry matric suction (𝜓_𝑒,𝜓_𝑒, and 𝛼⁻¹ of the CA, BC, and RU models, resp.).
^d𝑃₂ is the capillary pressure at the inflection point on the water retention curve (𝛼⁻¹, 𝛼⁻¹, and 𝜓_𝑜  of the VG₅, VG₄, and TA models, resp.).
^e𝑃₃ is a dimensionless parameter (𝛽,𝜆,𝑛,𝑛, and 𝑚 of the CA, BC, VG₅, VG₄, and RU models, resp.).
^f𝑃₄ is a dimensionless parameter (𝑚 of the VG₅ model).
^gA lower value of Akaike Information Criterion (AIC) indicates a better model fit.