0388-B4

Environmental services and productivity of native species plantations in Central America

Florencia Montagnini, Daniel Piotto and Luis Ugalde ¹

Abstract

The Central American wood market has traditionally relied on natural forests. With the advance of deforestation in recent years, several countries have supported the establishment of plantations. In addition to supplying the growing demand for wood, plantations provide environmental services such as carbon sequestration. This paper presents experiences with native species plantations, in pure and mixed designs over the past ten years in Costa Rica. Data on volume, biomass production and recuperation of biodiversity are presented. We recommend the establishment of government incentives for reforestation with native-species plantations.

Introduction

Tropical plantations provide a variety of environmental services, including wood production, carbon sequestration, and acceleration of forest succesional proceses (Parrotta 1992, Lamb 1998). With relatively high yields, tropical and subtropical plantations have the potential to contribute substantially to global wood production (Evans 1999, Wadsworth 1997). In addition, plantations are also a source of income for farmers (Chambers and Leach 1990).

In Central America, results of experiments started in the 1980s have helped to identify native and exotic species promising for reforestation. For example, the Proyecto Madeleña of CATIE (Tropical Agriculture Research and Higher Education Center) focused on 6 countries: Panama, Guatemala, Nicaragua, Costa Rica, El Salvador and Honduras (Ugalde 1997). CATIE and other institutions like the Organization for Tropical Studies (OTS), and the Instituto Tecnológico de Costa Rica (ITCR) have generated valuable information about growth, productivity, biomass and financial aspects for native and exotic trees in pure and mixed-species plantations of the humid tropics. The species studied have been estimated to have rotation periods of 12-25 years and projected yields of 250-300 m³/ha (González and Fisher 1994, Butterfield and Espinoza 1995, Montagnini et al. 1995, Montagnini and Mendelsohn 1997, Haggar et al. 1998).

Planting the studied tree species is an attractive alternative for farmers. Firewood from thinnings are an additional source of income. Recently interest in establishing mixed plantations has grown among small farmers in Central America (Montagnini et al. 1995, Montagnini and Mendelsohn 1997).

In Costa Rica, the forestry legislation includes incentives for establishment and management of plantations, especially on derelict pastures and other deforested lands. Because of these incentives interest in establishing plantations has grown among farmers. Nonetheless, farmers and entrepreneurs need better information about silviculture of native species to increase commercial value of plantations. More information would be especially valuable for improved plantation planning and management.

This paper presents results of native tree plantations in Costa Rica, including growth in mixed and pure-species plantations, carbon sequestration, and recuperation of biodiversity. Government incentives for native-species plantations are recommended for countries with conditions similar to those in Costa Rica.

Development of plantations in Costa Rica

In Costa Rica there are approximately 2.4 million hectares of pastureland, of which more than 400,000 hectares are abandoned and have grown secondary vegetation to varying stages of succession (Russo 1998). These abandoned lands could be recuperated with reforestation projects using native species.

Historically, the wood market in Costa Rica has been reliant on the exploitation of natural forests. Commercially, wood has primarily been used for furniture, doors for export, and housing. Reforestation using native species has begun over the past two decades. In Costa Rica various government incentives exist for the establishment and management of plantations. Incentives include Payment for Environmental Services (PES), and advanced purchase of timber. In 1996 with Forestry Law #7575, Costa Rica officially recognized environmental services provided by natural forests and plantations. Methods of payment for these services were also established (Campos and Ortíz 1999). This law allows for payments to owners of forested land and/or plantations because of the environmental services provided. The incentives programs are primarily financed by the government through selective gasoline taxes.

PES are made to owners of 2-300 hectares for conservation, management and regeneration of natural forest. Owners of >1 ha are paid for reforestation or plantation establishment. Applications are made at regional offices through the National Fund for Forest Finance (FONAFIFO), which manages funds and issues certificates for PES. Payments are dispersed over 5 years at different proportions depending on the type of forestry activity (Table 1).

Table 1. Payments forEnvironmental Services in Costa Rica for forestry (Campos and Ortíz 1999).

PES is highest for reforestation (establishing of new plantations, generally on abandoned lands from agriculture or cattle), with payments almost twice those payments made for conservation of natural forests. PES could therefore greatly encourage reforestation projects.

PES for plantations that are already established is relatively low, almost one-third that of reforestation. Nonetheless, PES for plantation establishment could be complemented with other avenues, such as advanced purchase of timber. Advanced purchase of timber is common for plantations over three years old, with average payments to land owners approximately $75/ha per year for up to 15 years. Land-owners receive $75 per hectare per year, plus 80% of the profit from the final timber sale.

PES and advanced purchase of timber eliminate or diminish one of the primary bottlenecks of reforestation: the high cost of plantation establishment and management.

Selection of species for plantations and agrosilvopastoril systems

Incorporation of forestry into production systems provides forest products (wood, firewood, mulch) and ecological benefits, especially improved nutrient cycling. Species selection depends on the possibility of achieving environmental benefits within the same system, or in some cases, of achieving a specific environmental function.

For example, recent experiments have tested growth and agroforestry potential of several native species, including Terminalia amazonia, Virola koschnyi, Dipteryx panamensis, Vochysia ferruginea, Vochysia guatemalensis, Hieronyma alchorneoides and Calophyllum brasiliense (Montagnini et al. 1995, Montagnini and Porras 1998, Byard et al. 1996, Kershnar and Montagnini 1998, Horn and Montagnini 1999, Piotto et al. 2002a, 2002b). All these species are frequently grown by farmers in the Atlantic humid lowlands of Costa Rica, often using the government incentives shown above (Piotto et al. 2002a). Table 2 shows estimated rotations, exptected timber volume and wood densities for these native species.

Table 2. Estimated rotation times, timber volume and specific gravity of wood for six native species commonly grown by farmers in the Atlantic lowlands of Costa Rica.

Growth and biomass on mixed and pure-species plantations

Well planned mixed-species plantations provide more diverse products than pure-species plantations. Mixed-species plantations diminish market-risk, reduce incidence and severity of certain pathogen attacks, and complement ecosystem resource use (Wormald 1992, Montagnini et al. 1995). For 10 years, growth and biomass production of 12 native species on three experimental plantations have been measured. Mixed and pure-species plots were located at La Selva Biological Station in the humid Atlantic lowlands of Costa Rica. The 12 native species studied were: Plantation 1: Jacaranda copaia (Aubl.) D.Don, Vochysia guatemalensis D.Sm., Calophyllum brasiliense Cambess and Stryphnodendron microstachyum Poepp. et Endl.; Plantation 2: Terminalia amazonia (Gmell.) Exell., Dipteryx panamensis (Pittier) Record & Mell, Virola koschnyi Warb and Albizia guachapele (H.B.K.) Little; Plantation 3: Hyeronima alchorneoides Fr. Allemao, Balizia elegans (D.C.) Benth., Genipa americana L.and Vochysia ferruginea Mart. Three plantations with four species each were designed based on species growth, form, economic value, farmer preference, and potential impact on recuperation of soil fertility (Montagnini et al. 1995). Plantations were designed in completely randomized blocks with four replications and five treatments: four pure-species plots per species, and one mixed-species plot with all four species. Initial spacing was at 2m x 2m and each plot was 32m x 32m with a total of 256 trees per plot, with thinnings at years 3 and 6 to leave trees at 4 m x 4 m spacing. In each mixed-species plot a systematic design was used to maximize species interactions (Montagnini et al. 1995). In each plot, individuals from the four species were alternated by row.

In Plantation 1, at 10 years of age, mixed-species plantations had the highest productivity of volume, statistically superior to pure-species plantations. This high productivity was directly related to the higher number of trees per hectare and to good height and diameter growth of trees on mixed-species plantations. Among the pure-species plantations, the highest growth recorded was for Vochysia guatemalensis and Jacaranda copaia. (Fig. 1). In Plantation 2, Virola koschnyi, Terminalia amazonia and mixed-species plantations had highest increment in volume. Plots with highest productivity at 9 years on plantation 3 were Vochysia ferruginea, followed by the mixed-species plantations, Balizia elegans, Hieronyma alchorneoides and Genipa americana (Piotto et al. 2002 b).

Measurements of biomass from thinnings at 6 years of age on Plantation 1 showed that pure plantations of Vochysia guatemalensis had highest biomass (91.2 Mg ha^-1), followed by the mixed-species plantation (90.1 Mg ha^-1), Jacaranda copaia and Calophyllum brasiliensis (Fig. 2) (Shepherd and Montagnini 2001).

On Plantation 2, highest biomass per hectare was measured on the mixed-species plantation, followed by Dipteryx panamensis, Terminalia amazonia, and Virola koschnyi (Shepherd and Montagnini 2001). On Plantation 3, Hyeronima alchorneoides in mixed plantations had the highest biomass, followed by Vochysia ferruginea. Apparently, trees in this study had more growing space for diameter growth in mixed-species condition, where there was less intra-specific competition (Montagnini et al. 1995, Montagnini and Porras 1998).

Mixed plantations, if planned according to the characteristics of each species, can produce more wood than pure-species plantations. Mixtures of fast-growing species and slower-growing species produce harvestable wood at different rotation times, with faster growing species producing timber of less value (e.g., Jacaranda copaia) and slower growing species (e.g., C. brasiliense, V. ferruginea) producting more valuable wood. The more valuable wood also constitutes a longer-term sink for fixed carbon (e.g., construction timber, furniture, wood crafts) than timber of less value, whose uses may be relatively shorter-lived (e.g., boxes, poles, fuelwood). Additionally, in a mixture, because the different species have different rotation times, the land is in use for a longer period of time than if planted with just one fast-growing, short rotation species. This diminishes incentives for changing to other land uses, keeps a vegetative cover that protects the soil, and serves other environmental services such as biodiversity conservation as well (Montagnini and Porras 1998).

Contribution of plantations to conservation and recuperation of biodiversity

At La Selva Biological Station, studies of understory plant diversity suggest that plantations can accelerate the recuperation of biodiversity (Guariguata et al. 1995, Powers et al.1997, Montagnini et al. 1999, Carnevale and Montagnini 2002).

In plantation 1, at 7 years of age, Vochysia guatemalensis, mixed-species plantations, and Calophyllum brasiliense, had the highest abundance of understory plant growth. These results are similar to those of a study by Powers et al. (1997) at La Selva, which found that plantations of Vochysia guatemalensis and V. ferruginea attracted dispersers and shaded out grasses quickly, allowing the establishment of native species.

In plantation 2, Terminalia amazonia, Virola koschnyi and the mixed-species plantation had the highest diversity of species regenerating in the understory. In plantation 3, the highest number of woody species was under the mixed-species plantation, followed by Hieronyma alchorneoides and Vochysia ferruginea. Species selection in reforestation projects influences the proportion of regeneration in each phase (colonization, establishment, growth and survival) (Carnevale and Montagnini 2002).

Use of monetary incentives to promote reforestation with native species

The studies discussed here indicate that native-species plantations have social and economic functions, including the provision of forest products, carbon sequestration, and recuperation of biodiversity. Government policies which promote reforestation through incentives or other means are necessary for the successful reforestation of degraded areas. It is recommended that incentives promoting reforestation through plantation establishment and management follow the models which have been successful. Specifically, it is recommended that countries follow the Costa Rican model of reforestation with government incentives.

It is also recommended that, in adition to establishment of new plantations, owners of existing plantations be allocated incentives on a yearly basis to continue proper management. The Forest Service of each country should control the payment of incentives. Non-governmental organizations should assist land owners with species selection and technical aspects of plantation establishment and management.

Finally, use of native species should be emphasized in reforestation projects. Also, regional experience with local species should be applied to reforestation projects.

CONCLUSIONS

Information about species growth rates, soil chemistry, biomass and leaf-litter nutrient content is necessary for the rehabilitation of humid tropical ecosystems. Such information must be employed for long-term, sustainable management plans.

Mixed-species plantations, if planned according to species characteristics, can produce higher wood volume than pure-species plantations. Fast and slow-growing species in the same plantations varies rotation length, and yields short and long term products.

In the plantations studied, understory regeneration was most successful on plantations than in abandoned pastures. Mixed-species plantations demonstrated good results for recuperating understory biodiversity. The results of these studies imply that native-species plantations have social and economic functions, provide forest products, contribute to the rehabilitation of degraded areas, promote atmospheric carbon sequestration, and restore biodiversity.

Government incentives or other methods are needed to promote reforestation of degraded lands. It is recommended that incentives for the establishment and management of native-species plantations follow the successful Costa Rica model discussed in this paper.

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¹ Yale University, School of Forestry and Environmental Studies, 370 Prospect St., New Haven, CT 06511, USA. [email protected]