Alfredo Alvarado

Factors affecting site productivity of a Costa Rican secondary rain forest in relation to Vochysia ferruginea, a commercially valuable canopy tree species

We estimated site productivity and its variation in a 28-year-old secondary rain forest in Florencia, San Carlos, Costa Rica, in relation to the dominant tree species, the commercially important Vochysia ferruginea. Thirty-six sample plots (2020 m 2 ) were installed in such a way as to cover the whole range of substrate variation at the site. The stand was assumed to be evenaged and of dominant height, estimated as the mean total height of the four tallest Vochysia trees in each plot, used as a measure of site productivity. Intra-plot coefficients of variation of total height of these four trees were <20%, indicating homogeneous conditions within plots in terms of site productivity and phytosanitary state. Of the dominant trees, however, 8% were found to have partially shaded crowns, which could lead to a subestimation of dominant height. For this reason, estimations of dominant height using two of the four trees per plot (these having fully illuminated crowns) were also developed. Dominant height of Vochysia was significantly correlated with mean plot canopy height and basal area of all species, and with its own basal area. Soil variables significantly correlated with dominant height were, at soil depth 0‐12 cm, clay(%), organic matter(%), P, Fe (all negatively correlated) and Cu (positively correlated). Adjusted multiple regression models of dominant height on soil variables were fitted by stepwise regression (Forward method). For four trees per plot, the best fit was obtained using P, Mn, percent organic matter and percent clay as independent variables (R 2 a79.5%, S.D. 1.8 m). For two trees with fully illuminated crowns, best fit was obtained from a model using the same variables except P. R 2 was lower for this latter model (74.4%), but the S.D. was also lower (1.2 m). Dominant height appears to be a potentially useful indicator of site productivity in neotropical secondary forests of similar ages, although it appears important, in mixed forests, to use crown variables to aid in the definition of dominant trees. There may be an important effect of site quality on production of timber in such forests, and such effects should be taken into account in the development of models of stand dynamics, growth and yield. # 1999 Elsevier Science B.V. All rights reserved.

Properties, Geographic Distribution, and Management of Major Soil Orders of Costa Rica

Publisher Summary Soils are the most important of the earths resources for humans. The soils of an entire nation are proportionately more complex, and need to be understood in their complexity in order to understand their sustainability. The chapter provides an overview of soils at the national level, including their types, patterns of use, and conservation status. It examines particular Costa Rican soils in much more detail, including their origin, physical and chemical nature, and management needs. The Costa Rican economy has been dependent historically on its agricultural soils. Since before colonial times natural vegetation growing in fertile lands nourished the local population, and subsequently sustained the European settlers. The agriculturally based economy has expanded to include many nontraditional crop production systems and even government sponsored reforestation. These are all part of a more diversified economy that includes the expansion of industry and tourism, and were the richness of Costa Ricas soils that has provided nutrients and maintained their physical properties through time. Costa Rica has extraordinary soil diversity in a very limited area, greatly enhancing vegetation diversity and thus possibilities for any kind of agricultural operations. The reason for this diversity is the highly variable parental material, a heterogeneous relief, and the action of a greatly variable climate and biota.

Soil fertility characterisation of teak (Tectona grandis L.f.) plantations in Central America

Teak (Tectona grandis L.f.) is an important species in the worldwide quality tropical hardwood sector, which has gained significance in Central America since the first large plantations were established in the 1980s. The present work is a descriptive study that aims to: (1) analyse and characterise the general soil patterns which may be influencing teak plantations in Central America; (2) assess differences between countries and sub-regions; (3) create a global framework to help contextualise the soil fertility analyses conducted at sub-regional or farm level, and (4) determine the main problems associated with soil fertility in the region. Soil fertility was measured at 684 sites in Costa Rica, Guatemala and Panama. Although teak is considered to be a species with high soil nutrient requirements, and high fertility is usually assumed in teak plantations, the results show that this species has been planted in a wide variety of soils, including many with serious fertility problems (e.g. Ultisols and perhaps Oxisols) or with added difficulties due to their physical properties (e.g. Vertisols). The present analysis reveals a general K deficiency in the Central American teak plantations, where P deficiency and acidity toxicity are also relatively common problems. These soil fertility problems probably stem from poor site selection by forest managers in the 80s and 90s. Hence, although soil fertility is carefully evaluated when most teak plantations are established today, managers have to deal with soil fertility deficiencies in many sites where teak was established some years ago.

N-P-K fertilisation of teak (Tectona grandis) plantations: a case study in Costa Rica

The global importance of short rotation, intensively managed planted forests has increased over recent years due to the growing need for timber and other goods. In this kind of system, nutrient management is a key issue and fertilisation plays a double role: a) improving productivity and b) compensating nutrient output in order to attain sustainability and maintain productivity for further rotations. The need to replace nutrients, taken up by the growing forest or removed during timber extraction, has long been recognised (Rennie 1955). However, Fölster & Khanna (1997) stated that conventional forest management has shown a general lack of concern with regard to this problem. Several authors have recommended the application of fertiliser to sustain productivity in short-cycle plantations (FSC 2004, Rennie 1955, Gonçalves et al. 1997, Worrel & Hampson 1997). This is especially important in tropical forests where nutrient dynamics and tree growth take place more rapidly than temperate zones. Teak (Tectona grandis) is an important species worldwide in the quality tropical N-P-K FERTILISATION OF TEAK (TECTONA GRANDIS) PLANTATIONS: A CASE STUDY IN COSTA RICA