The Effect of Trenching on Growth and Plant Health of Selected Species of Shade Trees

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Figure 1.
Trenching alongside hackberry trees on the University of Illinois campus in 1987.

Table 1:

Mean incremental growth of four shade tree species on the campus of the University of Illinois at Urbana-Champaign, 1987-1991.

Tree species	Mean dbh¹ (cm)	Trench distance² (m)	Treatment	Mean incremental growth (cm)⁴
				1987	1988	1989	1990	1991
Hackberry	26.2	0.5	T	1.12	0.38a	0.96a	0.69a	0.66a
	23.4	—	C	—³	0.74b	1.72b	1.32b	1.12b
Sweetgum	28.2	2.6	T	1.73a	0.61a	1.45a	1.83a	1.04a
	28.4	—	C	1.96a	0.91a	1.55a	1.83a	1.34b
Sugar Maple	29.5	0.9	T	0.58a	0.36a	0.94a	1.09a	0.69a
	29.0	—	C	0.91b	0.23a	0.94a	0.84a	0.74a
Honeylocust	44.9	1.8	T	0.79a	0.51a	0.83a	0.76a	0.74a
(Site#l) 47.7	—		C	1.04a	0.53a	0.74a	0.76a	0.81a
Honeylocust	36.6	3.3	T	1.12a	0.96a	0.74a	0.96a	0.51a
(Site #2) 31.8	—		C	1.04a	0.69b	0.81a	0.71b	0.69a

↵^1. Mean dbh measurements of all four tree species for trenched and control trees taken prior to the 1987 growing season.
↵^2. Linear distance from the center of the trunk of the affected tree to the center of the trench.
↵^3. No data available due to the replacement of the original control set with a new control set. (Refer to Materials and Methods for details).
↵^4. Paired treatment values for each tree species for each growing season followed by the same letter are not significantly different.(p<0.05; Two-Tailed T-test).