There are sound ecological and cultural arguments supporting the interest and importance in mixed-species stands silviculture, and its potential increase in production has not generally been included into forestry practice.
A "substitutive" randomized block design of twenty one permanent research plots was installed in 1981, in an experimental mixed stand of Castanea sativa and Pseudotsuga menziesii, in an adequate ecological region, Subatlantic and Submediterranic (SA x SM), for both species timber production, in Bemlhevai, Vila Flor, Portugal.
Seven types of consociation are tested, ranging from pure Castanea sativa (Cs) to pure Pseudotsuga menziesii (Pm), as well as: 1 Cs, 3 Pm, in the row; 1 Cs, 2 Pm, in the row; 1Cs, 1 Pm, in the row; 1 row of Cs, 1 row of Pm and, 1 row of Cs, 2 rows of Pm.
The research plots were observed and intensively measured yearly, In 1992, the Pseudotsuga menziesii trees were submitted to a penetration pruning and the Castanea sativa trees were classified, under a three item criteria, in order to select the crop trees which were pruned.
The 1992 height, diameter, h/d ration and top height, as well as the cumulative basal area, volume, weight and revenue figures, for the different mixtures are analyzed, in order to detect a possible mixtures differentiation.
The interest and importance of the mixed compositions is discussed, and a comparison for the observed weight and revenue figures, between monocultures and mixed-species stands is developed, based on the pure and mixed-species relative proportion approach.
The Castanea sativa and Pseudotsuga menziesii show resources use complementarity, due either to significant niche separation or direct beneficial relationship among the species, once the total relative proportion is, in most cases, greater than 1.0.
Key words: mixed stands, Castanea sativa, Pseudotsuga menziesii, species relative proportion.
Correspondence: Maria do Loreto Monteiro, Instituto Politecnico de Braganca, 5300 Braganca, Portugal
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