Thinning-caused change in reflectance of ground vegetation in boreal forest

Ground reflectances were measured in the blue, green, red and near infrared (NIR) regions of the spectrum in a set of recently thinned pine- and spruc e-dominated stands near Umea, Sweden. Compared with the untouched reference stands, the change in ground reflectance of the thinned stands was approxi mately linearly related to the thinning grade and to the coverage of the cu tting waste left on the ground. Typically, thinning resulted in a reflectan ce increase in the red and decrease in the NIR band. The major effects of t he presence of cutting waste on the ground reflectance can be simulated fol lowing a rather simple theoretical analysis. It appeared to be more difficu lt to quantitatively describe the effects on reflectance caused by the succ essional changes in the ground and field layer vegetation.