Analysis of diameter-density relationships and self-thinning in non-thinned even-aged Scots pine stands

Self-thinning and size-density relationships in non-thinned even-aged Scots pine stands in Spain were studied. Data from nine thinning experimental areas located in natural and artificial stands were used with a total of 23 untreated or control permanent plots. Three different diameter-density expressions were fitted and compared: the Reineke's equation, the modification of this expressions proposed by Zeide [Zeide, B.. 1995. For. Ecol. Manage. 72, 265-272], and the self-thinning model developed by Tang et al. [Tang S., Meng. C.H., Wang, Y.H., 1994. For. Ecol. Manage. 70, 67-73]. Results indicate that self-thinning in Pinus sylvestris L, follows a concave down line whose slope increases with stand density until it takes as its asymptote the straight line of maximum density. The slope of this straight line obtained for Scots pine stands in Spain is -1.75. (C) 2001 Elsevier Science B.V. All rights reserved.