Comparing Formula Methods of Tree Appraisal

Article Figures & Data

Table 1.

Species and characteristics of trees appraised.

Species	Species selection criteria^{^z}	Species (CTLA)^{^y}	Dbh (cm/in.) (CTLA)	Crown size (Helliwell)	Crown size (STEM)	Volume (m³) (Burnley)	Value factor^{^x} (Norma Granada)
Pin oak (Quercus palustris)	High species quality	0.7	84 (33)	3	3	877	738
American elm (Ulmus americana)	Low species quality	0.2	79 (31)	3	3	731	444
Linden (Tilia spp.)	Large trunk diameter	0.7	119 (47)	3	3	1,062	989
Kentucky coffeetree (Gymnocladus dioica)	Small tree	0.8	15 (6)	1.5	1	35	23
European beech (Fagus sylvatica)	Prominent landscape position; large crown	0.7	94 (37)	4	3	966	985
European ash (Fraxinus europea)	Obscure landscape position; large crown	0.6	94 (37)	4	3	1,253	871

Table 2.

Nursery tree purchase and planting costs used for formulas, in U.S. dollars.

	Pin oak (Quercus palustris)	Amer ican elm (Ulmus americana)	Linden (Tilia spp.)	Kentucky coffeetree (Gymnocladus dioica)	European beech (Fagus sylvatica)	European ash (Fraxinus excelsior)
CTLA
Basic price/in²	36	36	36	36	36	36
CTLA
Installed tree cost	570	570	570	570	570	570
STEM
6-cm tree wholesale	167	167	167	167	167	167
STEM
Planting cost	283	283	283	283	283	283
Burnley
1-m³^* tree retail	204	170	170	200	254	190
Norma Granada
6-cm tree wholesale	102	85	85	100	127	95

↵* A 1 m³ tree = 1.5-in. caliper, 10 to 12 ft tall, 2.5 to 3.5 ft wide as per ANSI Z60.1 standard.

Table 3.

Median appraised values of trees, in U.S. dollars, using the five different formula methods.

Appraisal method	Pin oak (Quercus palustris)	American elm (Ulmus americana)	Linden (Tilia spp.)	Kentucky coffeetree (Gymnocladus dioica)	European beech (Fagus sylvatica)	European ash (Fraxinus excelsior)
CTLA^{^z}	10,700 a^{^y}	2,000 a	17,300 b	600 a	13,900 a	5,700 a
Helliwell	5,313 a	2,361 a	3,985 a	2,361 b	25,190 b	4,723 a
STEM	46,485 b	37,812 b	48,402 c	37,760 d^{^x}	60,461 c	42,822 b
Burnley	78,898 b	26,096 b	64,994 c	4,460 c	122,950 d	46,661 b
Norma Granada	59,935 b	40,360 b	109,928 d	3,322 b	167,212 e	87,068 c

↵z CTLA method calls for rounding formula values to the nearest $100.
↵y Values followed by the same letter are not significantly different at P = 0.05.
↵x STEM is not intended for use on small trees.

Table 4.

Coefficient of variation.

Appraisal method	Pin oak (Quercus palustris)	American elm (Ulmus americana)	Linden (Tilia spp.)	Kentucky coffeetree (Gymnocladus dioica)	European beech (Fagus sylvatica)	European ash (Fraxinus excelsior)
CTLA	37	36	31	29	38	49
Helliwell	84	108	109	157	98	85
STEM	13	11	15	26	18	12
Burnley	49	42	37	22	48	58
Norma Granada	27	38	29	29	28	51

Table 5.

Differences in appraised values between two appraisers.

Appraisal method	Pin oak (Quercus palustris)		American elm (Ulmus americana)		Linden (Tilia spp.)		Kentucky coffeetree (Gymnocladus dioica)		European beech (Fagus sylvatica)		European ash (Fraxinus excelsior)
Appraisal method	Avg^{^z}	Range^{^y}	Avg	Range	Avg	Range	Avg	Range	Avg	Range	Avg	Range
CTLA	45	109	42	105	38	95	35	93	46	107	57	125
Helliwell	88	275	107	332	112	349	129	491	112	294	96	252
STEM	15	39	12	33	18	49	28	86	21	61	14	39
Burnley	58	130	50	121	44	120	24	76	57	140	68	153
Norma Granada	33	79	45	103	34	92	33	101	33	71	56	166

↵z Average difference in appraised values between all possible combinations of two appraisers/mean appraised value × 100.
↵y Difference between highest and lowest appraised values by nine individual appraisers for each method/mean appraised value × 100.