- Email: [email protected]
Attempting restoration of wet tropical forests in Costa Rica
Forest Ecology and Management 142 (2001) 243±249
Attempting restoration of wet tropical forests in Costa Rica A. Carl Leopolda,*, R. Andrusb, A. Finkeldeyc, D. Knowlesd a
Boyce Thompson Institute for Plant Research, Tropical Forestry Initiative, Cornell University, Ithaca, NY 14853, USA b Department of Biology, Binghamton University, Binghamton, NY 13902, USA c 7 Fiddlers Green, Lansing, NY 14882, USA d Department of Biology, East Carolina University, Greenville, NC 27858, USA Received 26 October 1999; accepted 26 January 2000
Abstract In southwestern Costa Rica, where the wet tropical forests have been seriously degraded to make way for pasture, many pasturelands are now idle or are coming up in scrub. Plantations of exotic species of trees in monocultures are the usual methods at obtaining forest cover. This report describes progress in an effort to show that restoration of wet native forest can be stimulated by planting mixed stands of native hardwoods. On a private reserve of 145 ha of abandoned pastureland, mixed stands have been established, involving up to 41 native species in the period since 1993. Sunloving species are growing as much as 3.1 m/year in height, and have exceeded 10 cm dbh in 5 years. Mixed stands of indigenous species are proposed as an alternative to monocultures, providing a possible source of income for small farmers, stabilizing the soil and stimulating the restoration of biodiversity. # 2001 Elsevier Science B.V. All rights reserved. Keywords: Costa Rica; Restoration; Tropical forest; Forest restoration
1. Introduction It is estimated that tropical forests originally covered between 96 and 99% of the land in Costa Rica. This was an enormous resource in terms of useful materials, bene®ts through stabilization of climate, and supportive biodiversity. In recent decades, an estimated 90% of the original forests have been destroyed, and some 46% of the total land has been converted into cattle pasture (Koll et al., 1995; Bryant et al., 1997; Mattoon, 1998). Deforestation continues at an estimated rate of 3.1% per year. Since much of the original timber-producing forests are gone, Costa *
Corresponding author. Tel.: 1-607-254-1327; fax: 1-607-254-2958. E-mail address: [email protected] (A.C. Leopold).
Rica is now experiencing a negative balance of trade in timber, and it imports more than US$ 500 million of wood per year (Bryant et al., 1997). Changes in the international market for lean beef, and deterioration of soils under grazing conditions, have caused many farmers to decrease or abandon cattle production. Consequently in some areas, scrub growth has begun, and there is a great need for restoration forestry. It is an appropriate time to consider the options for real reforestation. 2. The problem of forest restoration A problem of major importance, then, is how to foster forest recovery. Plantation forestry is being utilized world-wide on formerly forested tropical land.
0378-1127/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 - 1 1 2 7 ( 0 0 ) 0 0 3 5 4 - 6
244
A.C. Leopold et al. / Forest Ecology and Management 142 (2001) 243±249
In most instances, this has involved the planting of monocultures, usually of exotic tree species which have rapid growth rates. In Costa Rica, such plantations have mostly utilized such exotic species as Gmelina arborea (Gmelina), Eucalyptus deglupta (Eucalyptus), or Tectona grandis (Teak), the former two being used for chipping and paper production, the latter for ¯ooring. Monoculture plantations of exotic species may provide a cash crop, but they have come under considerable criticism in recent years for their tendency towards long-term ecosystem decline (Maser, 1994), depletions of water tables, and the need to employ pesticide use (Carrere and Lohman, 1996). Such monocultures are ordinarily established by large landholders, and are less appropriate for local farmers, as they usually require considerable technical management; they provide essentially no return to the local farmers. The sustainability of monocultures has been questioned from both economic and ecological viewpoints (Mattoon, 1998), and the large-scale production of wood-chip biomass is considered a poor contribution to the need for sustainable development (Carrere and Lohman, 1996). The use of native species in reforestation work has been proposed by numerous authors (Nichols and Gonzalez, 1992; Parrotta, 1993; Richter and Calvo, 1993; Butter®eld and Fisher, 1994; Calvo et al., 1997; Haggar et al., 1997). And probable extra bene®ts of native species in mixed stands have been pointed out many times (Matthews, 1989; Panayotou and Ashton, 1992; Lamb and Lawrence, 1993; Brown and Lugo, 1994; Ball et al., 1995; Keenan et al., 1995; Knowles and Parrotta, 1995; Montagnini et al., 1995; Parrotta et al., 1997). Nevertheless, there are singularly few data on the performance of mixed stands in Latin America. 3. New concepts of plantation Two changes in assessment of the reforestation problem have been offered in the past decade: (1) plantation of native tree species in monocultures has been given some considerable attention (Nichols and Gonzalez, 1992; Butter®eld and Fisher, 1994) and (2) the concept of using plantations as a `catalytic technique' to `jump-start' succession towards native forests has been demonstrated by Lugo (1997) and Parrotta et al. (1997).
The logic of the Nichols/Butter®eld scheme is simply that native species can provide wood which is of higher value than the chips obtained from fastgrowing exotic trees. The logic of the Lugo scheme is that the planting of rapidly-growing species can drastically modify the microclimate at the ground level, markedly improving conditions for the natural establishment of native tree seedlings. The modi®cation of the microclimate can stimulate succession towards the native tropical forests. The effectiveness of such a jump-start towards tropical forest development has been clearly documented (Powers et al., 1997). We are attempting to measure the success of planting mixed stands of native species for forest restoration in the pasturelands of Costa Rica. 4. Methods The reforestation work described here is an effort by the Tropical Forestry Initiative, a not-for-pro®t group of seven persons with a deep concern about the depletion of tropical forest resources (Leopold and Finkeldey, 1995). Beginning in 1992, it has purchased 145 ha of land on steep slopes in southwestern Costa Rica, approximately 10 km east of Dominical. This was land which had been cut over in the 1950s and has been used as pasture for about 45 years. Approximately equal amounts of the land were in grass pasture, and in partial scrub growth. A nursery was constructed, with a nylon screen for partial shade. In the ®rst year, seeds of seven quality native hardwood species (Table 1) were collected from the near neighborhood. After germination in a seed-bed, the seedlings were transferred to soil in plastic bags (10 cm25 cm). After 3 months in the nursery, the seedlings were about knee-high, and approximately 5000 were planted out in the pasturelands as mixed stands. For each seedling, the plastic bag was cut away, and the saplings were planted into open pasture at spacings of approximately 3 m3 m; enrichment plantings into partially developed scrub were at spacings of approximately 4 m4 m or more (Table 2). In the subsequent 5 years the mixed plantations have been expanded by 3000 or 5000 trees each year, and the range of species planted has gradually expanded to include a total of 41 species (Table 3).
A.C. Leopold et al. / Forest Ecology and Management 142 (2001) 243±249
245
Table 1 Growth performance of seven species planted in mixed stands after 5 years and two volunteer species Species Gallinazo Amarillon Cenicero Cristobal Guanacaste Iguano Cedro Mayo colorado Lechoso
Schizolobium parahybum Terminalia amazonia Albizzia longepedata Platymiscium pinnatum Enterolobium cyclocarpum Pithocolobium arboreum Cedrella odorata Vochysia ferruginea Brosimum utile
Number
Survival (%)
Average height (m) HT/year (m/year)
dbh (cm)
24 28 30 25 48 55 24 30 18
100 100 93 96 88 98 40 100 100
Est. 9 Est. 9 6.3/ÿ2.5 4.5/ÿ2.1 4.5/ÿ2.1 3.4/ÿ1.8
12.7/ÿ3.6 10.1/ÿ2.0 7.0/ÿ3.0 4.4/ÿ2.1 5.1/ÿ3.4 3.5/ÿ1.4
Maintenance of the seedlings in the ®eld has involved clearing competition with machete for about a meter around each tree for the ®rst four years. Transects totaling 750 m in length were established in which to sample growth performance of at least 24 of each of the species planted originally. Trees for measurement were each marked with aluminium tags. Measurements of height of the ®rst year's plantings has continued on a yearly basis and dbh has been recorded for those species exceeding 10 cm after 5 years.
2.2 3.1 1.7 1.3 1.3 1.6
14.3/ÿ3.9
3.7/ÿ1.9
To assess the recovery of species complexity after planting, a long-term monitoring program has been implemented. The centerpiece of this program is a set of permanent plots in aforestation sites at the TFI ®eld station. The permanent plot design and monitoring program follow methods modi®ed from the Smithsonian Institution's `Man and the Biosphere Biodiversity Program' (Dallmier, 1992). Permanent plots (20 m20 m) were established in representative areas of plantings. Each planted seedling as well as naturally colonizing seedlings and coppice or small trees were
Table 2 Composition and size of trees in 20 m20 m plots after 5 years
Guarumo Amarillon Chaperno Guaba Guayaba Cristobal Melastomaceae sp. Sura Mayo colorado Ceiba Corteza Vainilla Guanacaste Cedro amargo Ron ron Iguano Cocobolo Cenicero Jocate
Cecropia peltata Terminalia amazonia Lonchocarpus guatemalensis Inga coruscans Psidium guajava Platymiscium pinnatum Terminalia oblonga Vochysia ferrruginea Ceiba pentandra Tabebuia chrysantha Tecoma stans Enterolobium cyclocarpum Cedrela odorata Astronium graveolens Pithecolobium arboreum Dalbergia retusa Albizzia longipedata Spondias purpurea
Number
Height (m)
2 77 7 10 48 9 5 36 14 3 4 6 21 15 4 18 4 3 4
9.5/ÿ2.1 9.5/ÿ2.1 7.4/ÿ3.4 7.2/ÿ2.2 5.9/ÿ1.3 5.7/ÿ1.4 5.4/ÿ1.5 5.7/ÿ2.4 6.3/ÿ2.8 5.0/ÿ0.5 4.0/ÿ2.0 4.2/ÿ2.6 4.4/ÿ1.4 3.7/ÿ1.9 3.9/ÿ1.5 3.4/ÿ1.2 3.3/ÿ0.5 6.7/ÿ0.6 4.0/ÿ3.7
Planted
*
* * * * * * * * *
246
A.C. Leopold et al. / Forest Ecology and Management 142 (2001) 243±249
Table 3 Species of native trees planted in mixed stands in Costa Rica 1993±1998 No.
Common name
Species
Family
1540 100 40 3630 450 145 30 2840 980 325 425 830 98 440 440 350 155 50 390 300 260 90 670 55 810 560 430 1090 1050 640 50 55 195 100 595 200 245 820 40 50 75
Aceituno Ajillo Alazan Amarillon Anonillo Barrigon Cacao silvestre Cedro amargo Cedro Santa Maria Ceiba Cenicero macho Corteza Caoba Cenizaro Cristobal Cedro bateo Cocobolo Colorado Cuajada Espavel Faveira Fruta dorada Gallinazo Gavilan Guanacaste Guapinol Guayabon Iguano Jabillo Lechoso Manglillo Manu negro Mayo colorado Nene Palomo Pocora Roble sabana Ronron Vainilla Zapatero Zapaton
Simarouba glauca Caryocar costaricensis Tachigalia versicolor Terminalia amazonia Rollinia jimenezii Bombax barrigon Theobroma angustifolium Cedrela odorata Calophyllum braziliense Ceiba pentandra Albizzia longepedata Tabebuia chrysantha Swietenia macrophylla Pithecolobium saman Platymiscium pinnatum Carapa slateri Dalbergia retusa Callycophyllum candidissimum Vitex cooperi Anacardium excelsum Vatairea lundelii Virola koschnyi Schizolobium parahybum Oreamunoa pterocarpa Enterolobium cyclocarpum Hymenaea courbaril Terminalia oblonga Pithecollobium arboreum Hura crepitans Brosimum utile Aspidosperma creuten Minquartia guianensis Vochisia ferruginea Ormosia velutina Lafoensia punicifolia Guarea rhopalacarpa Tabebuiia rosea Ostronium graveolens Stryphnodendron microstachyum Hieronema alchorneoides Bombaxspp.
Simaroubaceae Cariocaraceae Leguminoseae Combretaceae Annonaceae Bombaceae Sterculaceae Meliaceae Guttiferae Bombacaceae Mimosaceae Bignoniaceae Meliaceae Leguminoseae Papilionatae Meliaceae Pipilionoideae Rubiaceae Verbenaceae Anacardiaceae Papillionatae Myristicaceae Caesalpinaceae Juglandaceae Mimosaceae Caesalpiniaceae Combretaceae Mimosaceae Euphorbiaceae Moraceae Apocynaceae Olacaceae Vochysiaceae Papilionaceae Lythraceae Meliaceae Bignoniaceae Anacardiaceae Mimosaceae Euphorbiaceae Bombacaceae
identi®ed, mapped, and measured (height and dbh). Additionally, canopy coverage was estimated using a canopy densiometer. To date seven plots have been established on replanted pastures. For comparative purposes, forest composition and structure have been measured on nearby old-growth forests using pointquarter transect methods.
5. Results In an effort to test the effectiveness of planting mixed stands of native hardwoods, approximately 5 ha of old pasturelands have been planted in southwestern Costa Rica. Growth rates for the 1993 plantings of native species in mixed stands have been calculated
A.C. Leopold et al. / Forest Ecology and Management 142 (2001) 243±249
247
Fig. 1. Height development of four native tree species planted in mixed stands: Gallinazo (Schizolobium parahybum), Cedro (Cedrela odorata), Guanacaste (Enterolobium cyclocarpum), and Iguano (Pithecollobium arboreum).
Fig. 2. Height development of four other native species: Amarillon (Terminalia amazonia), Mayo colorado (Vochysia ferruginea), Cenizaro (Pithecolobium saman), and Cristobal (Platymiscium pinnatum). The Mayo colorado trees were volunteers, seeded naturally from nearby primary forest remnants.
from the transect samples . The data in Figs. 1 and 2 indicate that the most rapid growth rates were achieved by Schizolobium parahybum (Gallinazo) and Terminalia amazonia (Amarillon), each of which achieved between 2 and 3 m increase in height per year. Cumulative dbh values exceeded 10 cm for both of these species, as well as for naturally occurring seedlings of Vochysia ferruginea (Mayo colorado) (Table 1). Slowest rates were recorded for Pithecelobium arboreum (Iguano) and Platymiscium pinnatum (Cristobal); the preference of Iguano for partial shade is consistent with its slower growth rate. Two of the planted species provided less than optimal growth records. Such was the case for Enterolobium cyclocarpum (Guanacaste) because of browsing by herbivores and for Cedrela odorata (Cedro) because of attack by the boring insect Hypsipyla. Records of Cedro growth in the transects were discontinued after 4 years. In the enrichment plantings, naturally occurring seedlings of V. ferruginea (Mayo colorado) and Brosimum utile (Lechoso) were tagged and monitored for comparison with the planted seedlings. As the seedlings approached 5 years of growth, dbh data were taken as shown in Table 1. The dbh values exceeded 10 cm for Amarillon and Gallinazo, as well as for the volunteer trees of Mayo colorado. In the course of 5 years, plantings have expanded to a total of 41 species of native trees (Table 3).
Even within 5 years after planting, there occurred a notable increase in complexity of species composition. The quadrats established in 1997 for measurements of changes in complexity showed an average of 46% of the ground cover taken over by volunteer scrub and tree species. Principal among these volunteers were 10 species of early-succession trees as listed in Table 2. On other pastures in the same farm we have found volunteer native hardwoods of 15 other species that have seeded in naturally from nearby remnants of primary forest. Most notable among these are the seedlings of Mayo Colorado, which are abundant enough to have formed an effective stand on a slope downwind from a primary forest remnant. 6. Discussion The work reported here was undertaken to demonstrate the merits of planting mixed stands of native hardwood species, in an effort to reestablish wet tropical forest in Costa Rica. Three years after planting into former pastures, some stands were nearing crown closure (Fig. 3). Five years after planting, the mixed stands of native species showed remarkably good survival, all showing better than 90% survival except for one species browsed by herbivores and one species attacked by Hypsipyla (Table 1). Growth rates
248
A.C. Leopold et al. / Forest Ecology and Management 142 (2001) 243±249
Fig. 3. Partial closure of mixed stand canopy at 4 years after planting.
ranged from 1.2 to 3.1 m/year, and the fastest growers exceeded 10 cm dbh after 5 years. In several stands crown closure had been achieved or nearly so. In spite of the degraded quality of the pastureland before the trees were planted, the growth parameters of sunloving species compare favorably with the 3 m/year growth rates of exotic species such as G. arborea, reported by Nichols and Gonzalez (1992). The rapid growth rates of the native species suggest that such mixed plantings could provide attractive opportunities for use on worn out pastures, especially on a small scale for individual farmers. In addition to bene®ts that can be obtained from plantations of popular exotic species in terms of soil retention, and stabilization of water supplies, mixed stands could provide a more valuable quality of wood (Calvo et al., 1997), a less technical management, as well as nurturing a gradual escalation of biodiversity. They should
provide the `catalytic effect' on succession described by Lugo (1997). Of course they provide a more natural stand of trees, they avoid the clear-cutting harvest, and perhaps most of all, they are more consonant with the development of complexity, stability, and biodiversity. Mixed stands do not concentrate the root system in one sector of the soil, but exploit the entire soil pro®le naturally (Harwood, 1993). They provide some protection from insect or disease attacks due to the spacing out of vulnerable individuals (Lamb and Lawrence, 1993; Ball et al., 1995). And they can have a lesser dependency on technical management. Collectively, these features should make them more appropriate for reforestation by local farmers. Mixed stands will limit harvesting to selective cutting. However, they will have the counter-characteristic of avoiding the ultimate clear-cut, which causes any monoculture to return to point zero with naked soils and depleted conditions. And the mixed stand should require less intensive management as well as more effectively promote regeneration of biodiversity (Haggar et al., 1997). Brown and Lugo (1994) point out that the literature provides many suggestions for successful rehabilitation of natural forests, but almost no examples of ®eld experience at such rehabilitation. We suggest that the program described here can provide evidence for the success of mixed stands to stimulate the restoration of wet tropical forests. The growth performance of the native tree species we have planted, and the early evidences of beginning biological complexity, indicate that real bene®ts can be achieved from planting mixed stands of native species for promoting the local restoration of wet tropical forests, and achieving the values associated with their biodiversity.
References Ball, J.B., Wormald, T.J., Russo, L., 1995. Experience with mixed and single species plantations. Comm. For. Rev. 74, 301±305. Brown, S., Lugo, A.E., 1994. Rehabilitation of tropical lands: a key to sustaining development. Restor. Ecol. 2, 97±111. Bryant, D., Nielsen, D., Tangley, L., 1997. The last frontier forests: ecosystems and economies on the edge. World Resources Institute, Washinton, DC. Butterfield, R.P., Fisher, R.F., 1994. Untapped potential: native species for reforestation. J. For. 92A, 37±40.
A.C. Leopold et al. / Forest Ecology and Management 142 (2001) 243±249 Carrere, R., Lohman, L., 1996. Pulping the South: Industrial Tree Plantations and the World Paper Economy. Zed Books, Atlantic Highland, NJ. Calvo, J.C., Arias, D., Sibaja,H., 1997. Resultados de un ensayo de eliminacion de 41 especies forestales en un suelo ultisol en Buenos Aires Buletin No. 7, Proyecto Especias Nativas Zona Sur, CR. Dallmier, F. (Ed.), 1992. Long-Term Monitoring of Biological Diversity in Tropical Areas: Methods For Establishment and Inventory of Permanent Plots .UNESCO, Paris, 72 pp. Haggar, J., Wightman, K., Fisher, R., 1997. The potential of plantations to foster woody regeneration in lowland Costa Rica. For. Ecol. Manage. 99, 55±64. Harwood, R.R., (Ed.), 1993. Sustainable Agriculture and Environment in the Humid Tropics. Nat. Acad. Sci. Press, Washington DC, 702 pp. Keenan, R., Lamb, D., Sexton, G., 1995. Experience with mixed species rainforest plantations in northern Queensland. Comm. For. Rev. 74, 315±321. Knowles, O.H., Parrotta, J.A., 1995. Amazonian forest restoration: an innovative system for native speicies selection. Comm. For. Rev. 74, 230±243. Koll, K.D., Daily, G.C., Ehrlich, P.R., 1995. Knowledge and perception in Costa Rica. Conserv. Biol. 9, 1548±1558. Lamb, D., Lawrence, P., 1993. Mixed species plantations using high-value rainforest trees in Australia. In: Leith, H., et al. (Eds.) Restoration of Tropical Forest Ecosystems. Kluwer, Netherlands, pp 101±108. Leopold, A.C., Finkeldey, A., 1995. Linking rainforest restoration with land stewardship in Costa Rica. Restor. Manage. Notes 13, 216±2125.
249
Lugo, A.E., 1997. The apparent paradox of reestablishing species richness with tree monocultures. For. Ecol. Manage. 99, 9±19. Maser, C., 1994. Sustainable Forestry: Philosophy, Science and Economics. St. Lucie Press, Delray Beach, FL. Matthews, J.D., 1989. Silvicultual Systems. Clarendon Press, Oxford. Mattoon, A.T., 1998. Paper profits. Worldwatch 11 (2), 20±28. Montagnini, F., Gonzalez, E., Porras, C., Rheingans, R., 1995. Mixed and pure forest plantations in the humid tropics. Comm. For. Rev. 74, 306±314. Nichols, D., Gonzalez, E., 1992. Especias Nativas y Exoticas para la Reforestacion en la Zona Sur de Costa Rica. Org. para Estudios Tropicales, San Jose, CR, 73 pp. Panayotou, T., Ashton, P.S., 1992. Not by Timber Alone. Island Press, Covelo, CA, 282 pp. Parrotta, J.A., 1993. Secondary forest regeneration on degraded tropical lands the role of plantations as foster ecosystems. In: Leith, H., et al. (Eds.), Restoration of Tropical Forest Ecosystems. Kluwer, The Netherlands, pp. 63±73. Parrotta, J.A., Turmbull, J.W., Jones, N., 1997. Catalyzing forest regeneration on degraded tropical lands. For. Ecol. Manage. 99, 1±7. Parrotta, J.A., Knowles, O.H., Wunderle, J.M., 1997. Floristic diversity in a 10-year old restoration forest on a bauxite site in Amazonia. For. Ecol. Manage. 99, 21±28. Powers, J.S., Haggar, J.P., Fisher, R.F., 1997. The effect of overstory composition on woody regeneration in plantations in Costa Rica. For. Ecol. Manage. 99, 43±54. Richter, D., Calvo, J., 1993. Reforestation of cutover lands with native trees in the Zona Sur of Costa Rica. Amigos Newsletter No. 38, O.T.S. San Jose, CR, pp. 8±10.
Attempting restoration of wet tropical forests in Costa Rica A. Carl Leopolda,*, R. Andrusb, A. Finkeldeyc, D. Knowlesd a
Boyce Thompson Institute for Plant Research, Tropical Forestry Initiative, Cornell University, Ithaca, NY 14853, USA b Department of Biology, Binghamton University, Binghamton, NY 13902, USA c 7 Fiddlers Green, Lansing, NY 14882, USA d Department of Biology, East Carolina University, Greenville, NC 27858, USA Received 26 October 1999; accepted 26 January 2000
Abstract In southwestern Costa Rica, where the wet tropical forests have been seriously degraded to make way for pasture, many pasturelands are now idle or are coming up in scrub. Plantations of exotic species of trees in monocultures are the usual methods at obtaining forest cover. This report describes progress in an effort to show that restoration of wet native forest can be stimulated by planting mixed stands of native hardwoods. On a private reserve of 145 ha of abandoned pastureland, mixed stands have been established, involving up to 41 native species in the period since 1993. Sunloving species are growing as much as 3.1 m/year in height, and have exceeded 10 cm dbh in 5 years. Mixed stands of indigenous species are proposed as an alternative to monocultures, providing a possible source of income for small farmers, stabilizing the soil and stimulating the restoration of biodiversity. # 2001 Elsevier Science B.V. All rights reserved. Keywords: Costa Rica; Restoration; Tropical forest; Forest restoration
1. Introduction It is estimated that tropical forests originally covered between 96 and 99% of the land in Costa Rica. This was an enormous resource in terms of useful materials, bene®ts through stabilization of climate, and supportive biodiversity. In recent decades, an estimated 90% of the original forests have been destroyed, and some 46% of the total land has been converted into cattle pasture (Koll et al., 1995; Bryant et al., 1997; Mattoon, 1998). Deforestation continues at an estimated rate of 3.1% per year. Since much of the original timber-producing forests are gone, Costa *
Corresponding author. Tel.: 1-607-254-1327; fax: 1-607-254-2958. E-mail address: [email protected] (A.C. Leopold).
Rica is now experiencing a negative balance of trade in timber, and it imports more than US$ 500 million of wood per year (Bryant et al., 1997). Changes in the international market for lean beef, and deterioration of soils under grazing conditions, have caused many farmers to decrease or abandon cattle production. Consequently in some areas, scrub growth has begun, and there is a great need for restoration forestry. It is an appropriate time to consider the options for real reforestation. 2. The problem of forest restoration A problem of major importance, then, is how to foster forest recovery. Plantation forestry is being utilized world-wide on formerly forested tropical land.
0378-1127/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 - 1 1 2 7 ( 0 0 ) 0 0 3 5 4 - 6
244
A.C. Leopold et al. / Forest Ecology and Management 142 (2001) 243±249
In most instances, this has involved the planting of monocultures, usually of exotic tree species which have rapid growth rates. In Costa Rica, such plantations have mostly utilized such exotic species as Gmelina arborea (Gmelina), Eucalyptus deglupta (Eucalyptus), or Tectona grandis (Teak), the former two being used for chipping and paper production, the latter for ¯ooring. Monoculture plantations of exotic species may provide a cash crop, but they have come under considerable criticism in recent years for their tendency towards long-term ecosystem decline (Maser, 1994), depletions of water tables, and the need to employ pesticide use (Carrere and Lohman, 1996). Such monocultures are ordinarily established by large landholders, and are less appropriate for local farmers, as they usually require considerable technical management; they provide essentially no return to the local farmers. The sustainability of monocultures has been questioned from both economic and ecological viewpoints (Mattoon, 1998), and the large-scale production of wood-chip biomass is considered a poor contribution to the need for sustainable development (Carrere and Lohman, 1996). The use of native species in reforestation work has been proposed by numerous authors (Nichols and Gonzalez, 1992; Parrotta, 1993; Richter and Calvo, 1993; Butter®eld and Fisher, 1994; Calvo et al., 1997; Haggar et al., 1997). And probable extra bene®ts of native species in mixed stands have been pointed out many times (Matthews, 1989; Panayotou and Ashton, 1992; Lamb and Lawrence, 1993; Brown and Lugo, 1994; Ball et al., 1995; Keenan et al., 1995; Knowles and Parrotta, 1995; Montagnini et al., 1995; Parrotta et al., 1997). Nevertheless, there are singularly few data on the performance of mixed stands in Latin America. 3. New concepts of plantation Two changes in assessment of the reforestation problem have been offered in the past decade: (1) plantation of native tree species in monocultures has been given some considerable attention (Nichols and Gonzalez, 1992; Butter®eld and Fisher, 1994) and (2) the concept of using plantations as a `catalytic technique' to `jump-start' succession towards native forests has been demonstrated by Lugo (1997) and Parrotta et al. (1997).
The logic of the Nichols/Butter®eld scheme is simply that native species can provide wood which is of higher value than the chips obtained from fastgrowing exotic trees. The logic of the Lugo scheme is that the planting of rapidly-growing species can drastically modify the microclimate at the ground level, markedly improving conditions for the natural establishment of native tree seedlings. The modi®cation of the microclimate can stimulate succession towards the native tropical forests. The effectiveness of such a jump-start towards tropical forest development has been clearly documented (Powers et al., 1997). We are attempting to measure the success of planting mixed stands of native species for forest restoration in the pasturelands of Costa Rica. 4. Methods The reforestation work described here is an effort by the Tropical Forestry Initiative, a not-for-pro®t group of seven persons with a deep concern about the depletion of tropical forest resources (Leopold and Finkeldey, 1995). Beginning in 1992, it has purchased 145 ha of land on steep slopes in southwestern Costa Rica, approximately 10 km east of Dominical. This was land which had been cut over in the 1950s and has been used as pasture for about 45 years. Approximately equal amounts of the land were in grass pasture, and in partial scrub growth. A nursery was constructed, with a nylon screen for partial shade. In the ®rst year, seeds of seven quality native hardwood species (Table 1) were collected from the near neighborhood. After germination in a seed-bed, the seedlings were transferred to soil in plastic bags (10 cm25 cm). After 3 months in the nursery, the seedlings were about knee-high, and approximately 5000 were planted out in the pasturelands as mixed stands. For each seedling, the plastic bag was cut away, and the saplings were planted into open pasture at spacings of approximately 3 m3 m; enrichment plantings into partially developed scrub were at spacings of approximately 4 m4 m or more (Table 2). In the subsequent 5 years the mixed plantations have been expanded by 3000 or 5000 trees each year, and the range of species planted has gradually expanded to include a total of 41 species (Table 3).
A.C. Leopold et al. / Forest Ecology and Management 142 (2001) 243±249
245
Table 1 Growth performance of seven species planted in mixed stands after 5 years and two volunteer species Species Gallinazo Amarillon Cenicero Cristobal Guanacaste Iguano Cedro Mayo colorado Lechoso
Schizolobium parahybum Terminalia amazonia Albizzia longepedata Platymiscium pinnatum Enterolobium cyclocarpum Pithocolobium arboreum Cedrella odorata Vochysia ferruginea Brosimum utile
Number
Survival (%)
Average height (m) HT/year (m/year)
dbh (cm)
24 28 30 25 48 55 24 30 18
100 100 93 96 88 98 40 100 100
Est. 9 Est. 9 6.3/ÿ2.5 4.5/ÿ2.1 4.5/ÿ2.1 3.4/ÿ1.8
12.7/ÿ3.6 10.1/ÿ2.0 7.0/ÿ3.0 4.4/ÿ2.1 5.1/ÿ3.4 3.5/ÿ1.4
Maintenance of the seedlings in the ®eld has involved clearing competition with machete for about a meter around each tree for the ®rst four years. Transects totaling 750 m in length were established in which to sample growth performance of at least 24 of each of the species planted originally. Trees for measurement were each marked with aluminium tags. Measurements of height of the ®rst year's plantings has continued on a yearly basis and dbh has been recorded for those species exceeding 10 cm after 5 years.
2.2 3.1 1.7 1.3 1.3 1.6
14.3/ÿ3.9
3.7/ÿ1.9
To assess the recovery of species complexity after planting, a long-term monitoring program has been implemented. The centerpiece of this program is a set of permanent plots in aforestation sites at the TFI ®eld station. The permanent plot design and monitoring program follow methods modi®ed from the Smithsonian Institution's `Man and the Biosphere Biodiversity Program' (Dallmier, 1992). Permanent plots (20 m20 m) were established in representative areas of plantings. Each planted seedling as well as naturally colonizing seedlings and coppice or small trees were
Table 2 Composition and size of trees in 20 m20 m plots after 5 years
Guarumo Amarillon Chaperno Guaba Guayaba Cristobal Melastomaceae sp. Sura Mayo colorado Ceiba Corteza Vainilla Guanacaste Cedro amargo Ron ron Iguano Cocobolo Cenicero Jocate
Cecropia peltata Terminalia amazonia Lonchocarpus guatemalensis Inga coruscans Psidium guajava Platymiscium pinnatum Terminalia oblonga Vochysia ferrruginea Ceiba pentandra Tabebuia chrysantha Tecoma stans Enterolobium cyclocarpum Cedrela odorata Astronium graveolens Pithecolobium arboreum Dalbergia retusa Albizzia longipedata Spondias purpurea
Number
Height (m)
2 77 7 10 48 9 5 36 14 3 4 6 21 15 4 18 4 3 4
9.5/ÿ2.1 9.5/ÿ2.1 7.4/ÿ3.4 7.2/ÿ2.2 5.9/ÿ1.3 5.7/ÿ1.4 5.4/ÿ1.5 5.7/ÿ2.4 6.3/ÿ2.8 5.0/ÿ0.5 4.0/ÿ2.0 4.2/ÿ2.6 4.4/ÿ1.4 3.7/ÿ1.9 3.9/ÿ1.5 3.4/ÿ1.2 3.3/ÿ0.5 6.7/ÿ0.6 4.0/ÿ3.7
Planted
*
* * * * * * * * *
246
A.C. Leopold et al. / Forest Ecology and Management 142 (2001) 243±249
Table 3 Species of native trees planted in mixed stands in Costa Rica 1993±1998 No.
Common name
Species
Family
1540 100 40 3630 450 145 30 2840 980 325 425 830 98 440 440 350 155 50 390 300 260 90 670 55 810 560 430 1090 1050 640 50 55 195 100 595 200 245 820 40 50 75
Aceituno Ajillo Alazan Amarillon Anonillo Barrigon Cacao silvestre Cedro amargo Cedro Santa Maria Ceiba Cenicero macho Corteza Caoba Cenizaro Cristobal Cedro bateo Cocobolo Colorado Cuajada Espavel Faveira Fruta dorada Gallinazo Gavilan Guanacaste Guapinol Guayabon Iguano Jabillo Lechoso Manglillo Manu negro Mayo colorado Nene Palomo Pocora Roble sabana Ronron Vainilla Zapatero Zapaton
Simarouba glauca Caryocar costaricensis Tachigalia versicolor Terminalia amazonia Rollinia jimenezii Bombax barrigon Theobroma angustifolium Cedrela odorata Calophyllum braziliense Ceiba pentandra Albizzia longepedata Tabebuia chrysantha Swietenia macrophylla Pithecolobium saman Platymiscium pinnatum Carapa slateri Dalbergia retusa Callycophyllum candidissimum Vitex cooperi Anacardium excelsum Vatairea lundelii Virola koschnyi Schizolobium parahybum Oreamunoa pterocarpa Enterolobium cyclocarpum Hymenaea courbaril Terminalia oblonga Pithecollobium arboreum Hura crepitans Brosimum utile Aspidosperma creuten Minquartia guianensis Vochisia ferruginea Ormosia velutina Lafoensia punicifolia Guarea rhopalacarpa Tabebuiia rosea Ostronium graveolens Stryphnodendron microstachyum Hieronema alchorneoides Bombaxspp.
Simaroubaceae Cariocaraceae Leguminoseae Combretaceae Annonaceae Bombaceae Sterculaceae Meliaceae Guttiferae Bombacaceae Mimosaceae Bignoniaceae Meliaceae Leguminoseae Papilionatae Meliaceae Pipilionoideae Rubiaceae Verbenaceae Anacardiaceae Papillionatae Myristicaceae Caesalpinaceae Juglandaceae Mimosaceae Caesalpiniaceae Combretaceae Mimosaceae Euphorbiaceae Moraceae Apocynaceae Olacaceae Vochysiaceae Papilionaceae Lythraceae Meliaceae Bignoniaceae Anacardiaceae Mimosaceae Euphorbiaceae Bombacaceae
identi®ed, mapped, and measured (height and dbh). Additionally, canopy coverage was estimated using a canopy densiometer. To date seven plots have been established on replanted pastures. For comparative purposes, forest composition and structure have been measured on nearby old-growth forests using pointquarter transect methods.
5. Results In an effort to test the effectiveness of planting mixed stands of native hardwoods, approximately 5 ha of old pasturelands have been planted in southwestern Costa Rica. Growth rates for the 1993 plantings of native species in mixed stands have been calculated
A.C. Leopold et al. / Forest Ecology and Management 142 (2001) 243±249
247
Fig. 1. Height development of four native tree species planted in mixed stands: Gallinazo (Schizolobium parahybum), Cedro (Cedrela odorata), Guanacaste (Enterolobium cyclocarpum), and Iguano (Pithecollobium arboreum).
Fig. 2. Height development of four other native species: Amarillon (Terminalia amazonia), Mayo colorado (Vochysia ferruginea), Cenizaro (Pithecolobium saman), and Cristobal (Platymiscium pinnatum). The Mayo colorado trees were volunteers, seeded naturally from nearby primary forest remnants.
from the transect samples . The data in Figs. 1 and 2 indicate that the most rapid growth rates were achieved by Schizolobium parahybum (Gallinazo) and Terminalia amazonia (Amarillon), each of which achieved between 2 and 3 m increase in height per year. Cumulative dbh values exceeded 10 cm for both of these species, as well as for naturally occurring seedlings of Vochysia ferruginea (Mayo colorado) (Table 1). Slowest rates were recorded for Pithecelobium arboreum (Iguano) and Platymiscium pinnatum (Cristobal); the preference of Iguano for partial shade is consistent with its slower growth rate. Two of the planted species provided less than optimal growth records. Such was the case for Enterolobium cyclocarpum (Guanacaste) because of browsing by herbivores and for Cedrela odorata (Cedro) because of attack by the boring insect Hypsipyla. Records of Cedro growth in the transects were discontinued after 4 years. In the enrichment plantings, naturally occurring seedlings of V. ferruginea (Mayo colorado) and Brosimum utile (Lechoso) were tagged and monitored for comparison with the planted seedlings. As the seedlings approached 5 years of growth, dbh data were taken as shown in Table 1. The dbh values exceeded 10 cm for Amarillon and Gallinazo, as well as for the volunteer trees of Mayo colorado. In the course of 5 years, plantings have expanded to a total of 41 species of native trees (Table 3).
Even within 5 years after planting, there occurred a notable increase in complexity of species composition. The quadrats established in 1997 for measurements of changes in complexity showed an average of 46% of the ground cover taken over by volunteer scrub and tree species. Principal among these volunteers were 10 species of early-succession trees as listed in Table 2. On other pastures in the same farm we have found volunteer native hardwoods of 15 other species that have seeded in naturally from nearby remnants of primary forest. Most notable among these are the seedlings of Mayo Colorado, which are abundant enough to have formed an effective stand on a slope downwind from a primary forest remnant. 6. Discussion The work reported here was undertaken to demonstrate the merits of planting mixed stands of native hardwood species, in an effort to reestablish wet tropical forest in Costa Rica. Three years after planting into former pastures, some stands were nearing crown closure (Fig. 3). Five years after planting, the mixed stands of native species showed remarkably good survival, all showing better than 90% survival except for one species browsed by herbivores and one species attacked by Hypsipyla (Table 1). Growth rates
248
A.C. Leopold et al. / Forest Ecology and Management 142 (2001) 243±249
Fig. 3. Partial closure of mixed stand canopy at 4 years after planting.
ranged from 1.2 to 3.1 m/year, and the fastest growers exceeded 10 cm dbh after 5 years. In several stands crown closure had been achieved or nearly so. In spite of the degraded quality of the pastureland before the trees were planted, the growth parameters of sunloving species compare favorably with the 3 m/year growth rates of exotic species such as G. arborea, reported by Nichols and Gonzalez (1992). The rapid growth rates of the native species suggest that such mixed plantings could provide attractive opportunities for use on worn out pastures, especially on a small scale for individual farmers. In addition to bene®ts that can be obtained from plantations of popular exotic species in terms of soil retention, and stabilization of water supplies, mixed stands could provide a more valuable quality of wood (Calvo et al., 1997), a less technical management, as well as nurturing a gradual escalation of biodiversity. They should
provide the `catalytic effect' on succession described by Lugo (1997). Of course they provide a more natural stand of trees, they avoid the clear-cutting harvest, and perhaps most of all, they are more consonant with the development of complexity, stability, and biodiversity. Mixed stands do not concentrate the root system in one sector of the soil, but exploit the entire soil pro®le naturally (Harwood, 1993). They provide some protection from insect or disease attacks due to the spacing out of vulnerable individuals (Lamb and Lawrence, 1993; Ball et al., 1995). And they can have a lesser dependency on technical management. Collectively, these features should make them more appropriate for reforestation by local farmers. Mixed stands will limit harvesting to selective cutting. However, they will have the counter-characteristic of avoiding the ultimate clear-cut, which causes any monoculture to return to point zero with naked soils and depleted conditions. And the mixed stand should require less intensive management as well as more effectively promote regeneration of biodiversity (Haggar et al., 1997). Brown and Lugo (1994) point out that the literature provides many suggestions for successful rehabilitation of natural forests, but almost no examples of ®eld experience at such rehabilitation. We suggest that the program described here can provide evidence for the success of mixed stands to stimulate the restoration of wet tropical forests. The growth performance of the native tree species we have planted, and the early evidences of beginning biological complexity, indicate that real bene®ts can be achieved from planting mixed stands of native species for promoting the local restoration of wet tropical forests, and achieving the values associated with their biodiversity.
References Ball, J.B., Wormald, T.J., Russo, L., 1995. Experience with mixed and single species plantations. Comm. For. Rev. 74, 301±305. Brown, S., Lugo, A.E., 1994. Rehabilitation of tropical lands: a key to sustaining development. Restor. Ecol. 2, 97±111. Bryant, D., Nielsen, D., Tangley, L., 1997. The last frontier forests: ecosystems and economies on the edge. World Resources Institute, Washinton, DC. Butterfield, R.P., Fisher, R.F., 1994. Untapped potential: native species for reforestation. J. For. 92A, 37±40.
A.C. Leopold et al. / Forest Ecology and Management 142 (2001) 243±249 Carrere, R., Lohman, L., 1996. Pulping the South: Industrial Tree Plantations and the World Paper Economy. Zed Books, Atlantic Highland, NJ. Calvo, J.C., Arias, D., Sibaja,H., 1997. Resultados de un ensayo de eliminacion de 41 especies forestales en un suelo ultisol en Buenos Aires Buletin No. 7, Proyecto Especias Nativas Zona Sur, CR. Dallmier, F. (Ed.), 1992. Long-Term Monitoring of Biological Diversity in Tropical Areas: Methods For Establishment and Inventory of Permanent Plots .UNESCO, Paris, 72 pp. Haggar, J., Wightman, K., Fisher, R., 1997. The potential of plantations to foster woody regeneration in lowland Costa Rica. For. Ecol. Manage. 99, 55±64. Harwood, R.R., (Ed.), 1993. Sustainable Agriculture and Environment in the Humid Tropics. Nat. Acad. Sci. Press, Washington DC, 702 pp. Keenan, R., Lamb, D., Sexton, G., 1995. Experience with mixed species rainforest plantations in northern Queensland. Comm. For. Rev. 74, 315±321. Knowles, O.H., Parrotta, J.A., 1995. Amazonian forest restoration: an innovative system for native speicies selection. Comm. For. Rev. 74, 230±243. Koll, K.D., Daily, G.C., Ehrlich, P.R., 1995. Knowledge and perception in Costa Rica. Conserv. Biol. 9, 1548±1558. Lamb, D., Lawrence, P., 1993. Mixed species plantations using high-value rainforest trees in Australia. In: Leith, H., et al. (Eds.) Restoration of Tropical Forest Ecosystems. Kluwer, Netherlands, pp 101±108. Leopold, A.C., Finkeldey, A., 1995. Linking rainforest restoration with land stewardship in Costa Rica. Restor. Manage. Notes 13, 216±2125.
249
Lugo, A.E., 1997. The apparent paradox of reestablishing species richness with tree monocultures. For. Ecol. Manage. 99, 9±19. Maser, C., 1994. Sustainable Forestry: Philosophy, Science and Economics. St. Lucie Press, Delray Beach, FL. Matthews, J.D., 1989. Silvicultual Systems. Clarendon Press, Oxford. Mattoon, A.T., 1998. Paper profits. Worldwatch 11 (2), 20±28. Montagnini, F., Gonzalez, E., Porras, C., Rheingans, R., 1995. Mixed and pure forest plantations in the humid tropics. Comm. For. Rev. 74, 306±314. Nichols, D., Gonzalez, E., 1992. Especias Nativas y Exoticas para la Reforestacion en la Zona Sur de Costa Rica. Org. para Estudios Tropicales, San Jose, CR, 73 pp. Panayotou, T., Ashton, P.S., 1992. Not by Timber Alone. Island Press, Covelo, CA, 282 pp. Parrotta, J.A., 1993. Secondary forest regeneration on degraded tropical lands the role of plantations as foster ecosystems. In: Leith, H., et al. (Eds.), Restoration of Tropical Forest Ecosystems. Kluwer, The Netherlands, pp. 63±73. Parrotta, J.A., Turmbull, J.W., Jones, N., 1997. Catalyzing forest regeneration on degraded tropical lands. For. Ecol. Manage. 99, 1±7. Parrotta, J.A., Knowles, O.H., Wunderle, J.M., 1997. Floristic diversity in a 10-year old restoration forest on a bauxite site in Amazonia. For. Ecol. Manage. 99, 21±28. Powers, J.S., Haggar, J.P., Fisher, R.F., 1997. The effect of overstory composition on woody regeneration in plantations in Costa Rica. For. Ecol. Manage. 99, 43±54. Richter, D., Calvo, J., 1993. Reforestation of cutover lands with native trees in the Zona Sur of Costa Rica. Amigos Newsletter No. 38, O.T.S. San Jose, CR, pp. 8±10.