Genetic analysis of intensively thinned young stands at pre-mature age | Intensīvi izretināto jaunaudžu ģenētiskās savdabības briestaudžu vecumā

Recently, as a result of a better understanding about the development of forest stands, and due to a sharp reduction in the proportion of overgrown young stands, it is necessary to significantly modify the current regulations governing commercial thinning activities. Data from repeated measurement of sample plots show that leaving 1500-2000 trees per hectare during early pre-commercial thinning, does not influence the dominant stand tree number up to 18-20 m in height, and that all remaining trees continue to be productive. In these types of stands, the basal area of the dominant stand considerably surpasses the 1985 thinning regulations governing the size of the remaining basal area. Therefore the use of these regulations when planning commercial thinning in these pre-thinned young stands would be incorrect. However, even in appropriately managed stands, an intermediate stand develops, and considerations about the usefulness of removing this are primarily economic. Currently, there is insufficient data available to predict when these intermediate stands will develop, what the parameters of the trees found in these intermediate stands are, and what is the most efficient commercial thinning regime for modern managed forest stands. Starting thinning from below in 30-40 year old spruce stands, every removed tree must have commercial value. Therefore the advantageousness of pre-commercial thinning is determined by projected stand parameters - average diameter, average height, tree number and calculated yield. The yield of thinned young stands up to 15 m height is often slightly lower than of unmanaged stands. During further growth, the yield indices gradually equalise, and in stands over 20 m in height, the yield of thinned stands significantly surpasses that of unmanaged stands. Yield differences have been noted between thinned stands of similar height in different a/s “Latvijas valsts meži” (Latvian State Forests) forestry's, which cannot be explained by differences in growth habitat.