Growth and increase of a Pinuspatula plantation with fertilization and thinning treatments
Abstract
Thinning and fertilization of forest plantations are forestry practices that are necessary to obtain an increase in the annual volume growth, mean increment and periodic increment (AMI and API) which allow shortening the commercial shift maintaining the same volumes at the time of harvest. In this study, the effect of thinning and fertilization on the growth and increase in Pinuspatula plantations was evaluated, which were established in 1998 in Huayacocotla, Veracruz, Mexico. A 22 factorial experiment was set up in the plantation in order to evaluate the thinning and fertilization factors with two levels each. The experimental unit was a 10x10 m plot. Three repetitions were established per treatment. An residual basal area of 21m2 ha-1was obtained in the thinned plots of the plantation. The average basal area in the unthinned plots was 42 m2 ha-1. The fertilization doses were: 1.4; 0.4; 8.34 kg of urea, calcium triple superphosphate and potassium sulfate, respectively. Fertilization (treatment 3) increased the volume and the AMI 2012, 2013 and 2014. Thinning (treatment 2) tended to increase the API slightly.
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Introduction
Growth is defined as the integral and gradual increase in biomass, product of the individual’s biological activity. The growth of a tree is influenced by its genetic constitution and the environment that it develops in. The genetic information determines the tree’s response to the different environments, controlling its manifestations. The environment provides nutrients, water and illumination, and therefore, the tree’s growth is the response to the joint action of its genetic information and the environmental factors (Hocker, 1984).
Thinning is forestry tool that when applied selectively favors the best trees, and it is useful in old and young stands. After thinning, the remnant (residual) trees react by increasing their growth rate and reducing the length of their tracheids, they also acquire tolerance to bark beetles (Dendroctonusadjunctus) and more resistance to fires, decrease the level of leaf infestation caused by fungi, and also change the biomass distribution between foliage and stem(Gajardo-Caviedes, 2005).
The objective of thinning applied to a forest mass is to produce a higher commercial wood volume per surface unit. This is achieved because when reducing the density of the plantation, the residual trees obtain greater growth space and can grow more in diameter, with which the proportion of timber-yielding products with sawmill and plywood quality of large dimensions extracted, can be increased (Rodríguez et al., 2011).
Fertilization is another forestry practice, which, according to Lázaro et al. (2012), has the objective of attaining high yields in harvesting wood of good quality. Its action consists in improving the soil as nutritional substrate as well as complementing the natural supply of nutritional elements, in some cases deficient, and restoring the nutritional elements that have been extracted by the crop itself or that have disappeared because of other reasons.
The same authors indicate that the application of fertilizers is necessary for the survival of many tropical and temperate plantations, since the fertilizers increase the diameter of the tree more than the height and therefore increase the tapering of the lumber, reducing the shape factor. They also reduce the variability of the diameter of trees in plantations.
The combination of thinning and fertilization in forest plantations improves the properties and quality of the wood. Based on this, the objective of this study is to evaluate growth in two Pinuspatula plantations treated with thinning and fertilization.
Conclusion
Treatments: 2, with fertilization and with thinning, and 4, with fertilization and without thinning, significantly affected the volume and the API 2012, 2013 and 2014in the plantation under study. The treatment that increased the volume and the AMI 2012, 2013 and 2014 in the plantation was treatment 3: with fertilization and without thinning. Thinning tended to increase the API 2012 -2014. However, it is necessary to perform more intense thinning on the plantation 1998 for there to be differences and for the results on volume and AMI to be noticeable, since the density is high despite the light thinning that was performed.
