Comparison of estimators of variance for forest inventories with systematic sampling - results from artificial populations

Forest Ecosystems

Table 2 Estimated variances in populations with spatial autocorrelation and a strong, a moderate, and a weak global linear trend. All table entries are means across 30 realizations of a super-population with autocorrelation and a linear trend, and the K possible sample for a given sampling interval (d). Variances in parentheses are relative variances with the DES variance fixed at 100. τ_{i, j} is the trend component for unit in row i and column j (i, j = 0.5, 1.5, …, 239.5)

Trend	Trend variance (%)	Site effect variance (%)	Sample size (units)	Sample interval (units)	Variance estimator × 10³
Trend	Trend variance (%)	Site effect variance (%)	Sample size (units)	Sample interval (units)	DES	SRS	MAT	SDR	RIP	DOR
Strong τ_{i, j} = (i + j − 241)/120	45	25	400	12	0.88 (100)	2.52 (288)	1.04 (119)	1.15 (131)	1.58 (180)	1.20 (137)
Strong τ_{i, j} = (i + j − 241)/120			1600	6	0.24 (100)	0.62 (262)	0.25 (104)	0.26 (107)	0.21 (88)	0.26 (110)
Moderate τ_{i, j} = (i + j − 241)/240	16	35	400	12	1.50 (100)	2.56 (171)	1.51 (101)	1.64 (109)	2.06 (138)	1.65 (110)
Moderate τ_{i, j} = (i + j − 241)/240			1600	6	0.34 (100)	0.62 (182)	0.34 (101)	0.35 (104)	0.35 (105)	0.36 (106)
Weak τ_{i, j} = (i + j − 241)/480	4	40	400	12	1.71 (100)	2.56 (150)	1.67 (98)	1.81 (106)	2.20 (129)	1.81 (106)
Weak τ_{i, j} = (i + j − 241)/480			1600	6	0.38 (100)	0.62 (162)	0.38 (100)	0.39 (105)	0.40 (103)	0.39 (103)