Reforestation Trials Research Articles

Pruebas de reforestación de mangle en una ciénaga costera semiárida de Yucatán, México

Como parte del Programa de Restauración Ambiental y Fortalecimiento al Desarrollo Regional en la microcuenca costera de Chabihau, Yucatán, México (2004-2006), se evaluó la sobrevivencia y el crecimiento de plántulas de Rhizophora mangle L. (mangle rojo) y Avicennia germinans ( L.) L. ( mangle negro), a través de diferentes pruebas de reforestación. Con las nuevas condiciones que se registran en la ciénaga, después de la construcción de puentes en la carretera costera, la sobrevivencia está regulada por el nivel de inundación, mientras que la salinidad del agua controla el crecimiento de las plántulas de manglar. El mangle rojo presentó una mayor sobrevivencia bajo condiciones de mayor inundación y un mayor desarrollo con baja salinidad intersticial (3,28 ups ± 0,32 ups), mientras que el mangle negro presentó una mayor sobrevivencia en áreas menos inundadas y un mayor desarrollo con más alta salinidad (45,5 ups ± 0,50 ups). La construcción de camas de sedimento para controlar el grado de inundación demostró ser una técnica útil para favorecer la sobrevivencia de mangle negro, mientras que el desazolve de manantiales y la disminución de la salinidad del agua, aseguran un mejor desarrollo de las plántulas de ambas especies. Se obtuvo una mayor sobrevivencia del mangle rojo producido en el vivero que de la siembra directa. La menor profundidad y mayor salinidad del agua registrados en la ciénaga en 2006, considerado como un año menos lluvioso, pueden estar relacionadas con una mayor repoblación natural de mangle negro. Para el diseño de programas de reforestación se debe contar con un monitoreo de parámetros hidrológicos superficiales y del suelo (particularmente nivel de inundación y salinidad), que permita la selección de las especies y los métodos adecuados para asegurar la mayor sobrevivencia y el mejor desarrollo de las plantas.

Use and cultivation of plants that yield products other than timber from South Asian tropical forests, and their potential in forest restoration

Rural communities have traditionally valued forests for a diversity of products and services, with timber serving a minor role. No-where has this diversity been greater than in tropical South Asia, and in particular south India and Sri Lanka. As economies advance towards full development and populations become increasingly urbanized, forests become increasingly valued for their services. National development generally occurs at differing rates in different regions, with rural forest dependent communities falling behind and pockets of poverty long remaining. The demand for ‘non-timber forest products’ (NTFPs) therefore changes from subsistence to monetary based values. Overall, though, forests have suffered an unprecedented decline with development in the tropics, especially in Asia. This necessitates restoration which takes account of the enrichment of economy, wellbeing and culture which forest products provide. Methods for such restoration, and the fundamental principles upon which these must rest, are presented for species yielding NTFP’s. In this paper we first review the history of NTFP species use within south India and Sri Lanka. Second we provide a description of the broad regional characterizations of the forest formations within this region in relation to their affiliated patterns of NTFP use and exploitation. We consider seven guilds as a way to categorize NTFP’s into autecological groups for application in restoration silviculture, and use it as a framework to suggest restoration protocols for South Asian forests. We use examples of scenarios based on experimental studies of NTFP’s in reforestation trials which take account of different social values and land tenures. We conclude with a call for further research.

How old is the human footprint in the world's largest alpine ecosystem? A review of multiproxy records from the Tibetan Plateau from the ecologists' viewpoint

The age at which a human environment was made is strongly debated in Quaternary science. The perception of the human footprint requires an understanding of the contrast between the present cultural environment and the natural vegetation. This is especially true for high altitude ecosystems, such as the world's largest alpine ecosystem, the 450,000 km2 of golf-course-like pastures dominating the southeastern Tibetan Plateau. This ecosystem is widely considered to be natural, but only because of the unawareness of the effects of grazing management and the incorrect assessment of human signals in palaeo proxies. Here we posit the hypothesis that this ecosystem is a human-induced replacement. To test our hypothesis against defined a priori criteria, we 1) monitored vegetation in grazing exclosures; 2) produced floristically complete vegetation records; 3) compared the vegetation records with data of the nearest climate stations; 4) surveyed forest and experimental reforestation trials with endemic tree species; 5) analyzed pollen and re-evaluated published pollen diagrams; and 6) integrated these results with palaeopedological and anthracological results of previous studies. The results of long-term grazing exclosure experiments, the prevalence of grazing-adapted plant functional types, the occurrence of isolated vigorous forests in “alpine” pastures, and the successful reforestation trials in presently treeless pastures together suggest that dominant pastures replaced forests in the montane belt and tall grassland in the alpine belt. The spatial and temporal coincidence of palaeosols and archaeological sites with tree species charcoal, the decline in forest pollen during the mid-Holocene climatic optimum, and the first appearance of human indicator pollen are most parsimoniously explained by the early presence of foragers and pastoralists. The onset of pastoralism in the Tibetan Highlands is presumed to date from the 8th millennium BP.

Growth performance of sixty tree species in smallholder reforestation trials on Leyte, Philippines

Although many reforestation projects have attempted to mitigate deforestation in the Philippines, most have focused on planting introduced trees, often with low success rates. A smallholder-based project in the Visayas region planted native species instead. This study assessed the growth performance of forty-four native and sixteen introduced species in 25 sites established by this project between 1995 and 2000. Diameter at breast height and total height were measured for 2,789 trees. Mean annual increments for diameter (MAID) at breast height and height (MAIH) were significantly higher for trees planted on limestone-influenced soils (MAID = 1.19 cm/year; MAIH = 1.05 m/year) than on purely volcanic soils (MAID = 0.81 cm/year; MAIH = 0.78 m/year). Growth of two native species, Melia dubia and Terminalia microcarpa, was higher than that of the widely planted exotic Swietenia macrophylla. The height increment for the highest-performing dipterocarp species, Shorea guiso, Shorea contorta, and Parashorea malaanonan, was not statistically different from the MAIH of S. macrophylla. A range of soil characteristics predicted performance, with organic matter predicting growth for six species, and percent nitrogen and percent clay predicting performance of five species. These findings show that certain native species can perform better than some exotic species when planted in open areas. They also disprove the widely held belief in the Philippines that Dipterocarpaceae cannot be planted in grasslands, and suggest that dipterocarps can be used successfully in reforestation. Finally, the findings show that more research is needed on species-site matching and on silvicultural management of native species plantations.

Early growth and survival of 49 tropical tree species across sites differing in soil fertility and rainfall in Panama

Reforestation in the tropics takes place across a wide variety of edaphic and climatic conditions. Reforestation trials have demonstrated that edaphic conditions may have a strong effect on species growth and survival. However it is unclear how the relative importance of soil conditions influences species survival and growth under varying amounts of rainfall and lengths of dry season. Two-year growth and mortality of 49 tree species were evaluated in four sites across Panama, representing a soil fertility–rainfall matrix. Despite strong contrasts in environmental conditions, 65% of individual species did not show consistent differences in growth between high- and low-fertility sites or between wet and dry sites. However, early growth and survival were more strongly affected by soil fertility than by rainfall patterns for the second-largest group; 30% of the species grew significantly better in both high-fertility sites than in both low-fertility sites, compared to 6% in both wet sites vs. both dry sites. In the two high-fertility sites, growth of 47% and 69% of the species was better than their across-site means. On the other hand, 55% and 73% of the species grew significantly slower than their across-site averages in the two low-fertility sites. Survival did not appear to be associated to either soil fertility or rainfall. In each site, only a few species had a significantly higher or lower within-site survival than across-site survival. Diversifying the choice of tree species increases the options for reforestation strategies that match species characteristics to local site conditions and to the objectives and management possibilities of landholders. Testing the performance of potential species under different site conditions in screening trials is paramount, both to inform selection from among the vast diversity of tree species in the tropics that show good growth and survival under different local site conditions and to filter out unsuitable species and avoid early failure of the reforestation effort.

An inventory of forest relicts in the pastures of Southern Tibet (Xizang A.R., China)

An inventory of isolated tree stands surrounded by desert pastures in Southern Tibet (A.R. Xizang, China) revealed more than 50 sites with vigorous trees of Juniperus convallium Rehder & E.H. Wilson and Juniperus tibetica Kom and additional more than 10 records where juniper trees had been destroyed between 1959-1976. The tree stands are not restricted to any specific habitat, and occur within an area stretching 650 km westwards from the current forest border of Southern Tibet. The trees are religious landmarks of the Tibetan Buddhists. The highest trees were found at an elevation of 4,860 m. Vegetation records, rainfall correlations and temperature data collected by local climate stations and successful reforestation trials since 1999 indicate that forest relicts fragmented through human interference could regenerate if current cattle grazing and deforestation practices are halted. The drought line of Juniperus forests in Southern Tibet is approximately 200-250 mm/a. A first pollen diagram from Lhasa shows forest decline associated with the presence of humans since at least 4,600 yr BP. The currently degraded commons developed in the last 600 yr. To date, no findings of remains of ancient forests in the Central Tibetan Highlands of the Changtang have been reported.

Pure and mixed forest plantations with native species of the dry tropics of Costa Rica: a comparison of growth and productivity

In Costa Rica, most reforestation trials with native species were established in the tropical humid regions. In the dry tropics, research on the performance of native species in forest plantations is incipient and trials comparing pure and mixed designs are limited. This paper presents the results of two experimental plantations with native trees in pure and mixed plots in the dry tropics of Costa Rica. The growth and productivity of 13 native species in pure and mixed plantations was compared with Tectona grandis (L.f.) Lam., an exotic species broadly used in the region. In a plantation of relatively slower growing species, measurements taken at 68 months of age resulted in Samanea saman (Jacq.) Merril. and Dalbergia retusa Hemsl. demonstrating the best growth, followed by Astronium graveolens Jacq. and Swietenia macrophylla King. Measurements in a plantation of relatively faster growing species, at 68 months of age, showed that growth of Schizolobium parahyba (Vell.) Blake was greatest in the pure and mixed plots, followed by Terminalia oblonga (Ruiz & Pav.) Steud., Anarcadium excelsum (Bert. & Balb. ex Kunth) Skeels and Pseudosamanea guachapele (Kunth) Harms. The native species grew better in the mixed plots. The pure plots of T. grandis (L.f.) Lam. were the most productive, compared to all species and the mixture of species. Plantations of T. grandis (L.f.) Lam. seem to be well adapted to the region and are certainly a commercially interesting alternative. Nevertheless, mixed plantations with native species would contribute more to sustainable management, because while single-species plantations do not provide a great range of goods and services when compared to the natural forest, mixed plantations are likely to increase this range of benefits.

98/03076 Hydrogen production from lignocellulosic materials by steam gasification using a reduced nickel catalyst

To screen for rapidly growing trees, lifetime growth histories of 160 species were estimated from data collected in a permanent 50 ha census plot in tropical moist forest in Panama. Most of the 160 species had never been studied before in detail, and newly encountered species with rapid growth might provide better techniques for reforesting degraded soils in Central America. To estimate lifetime growth, polynomial regressions were fitted to instantaneous growth rates expressed as a function of log-transformed diameter at breast height (dbh). These functions represent a differential equation in dbh, and explicit solutions for the equations provided dbh trajectories as a function of age (starting at 1 cm dbh, which was the smallest size included in the census). Dbh trajectories were calculated for 160 species, and full growth data are presented for the 28 species that ranked among the fastest 15 to reach a dbh of 10, 30, or 60 cm. Dbh trajectories based on growth of one standard deviation above the mean were also estimated for these species by fitting a polynomial regression to the residuals around the original regression. The fastest-growing tree in the 50 ha plot was the balsa, Ochroma pyramidale, which reached 10 cm in 5 years and 30 cm in 10. Cavanillesia platanifolia, Trema micrantha, Zanthoxylum belizense, and Vochysia ferruginea were the other top-ranking species. At mean growth, the top 15 ranking species required 5–25 years to reach 10 cm, 10–67 years to reach 30 cm, and 32–111 years to reach 60 cm, starting at 1 cm. At growth one standard deviation above the mean, the same species requried 4–18 years to reach 10 cm, 8–35 years to reach 30 cm, and 19–69 years to reach 60 cm dbh. We recommend that the little-known species from this list be further tested in reforestation trials.

Acclimation abilities of three tropical rainforest seedlings to an increase in light intensity

Current practices in many nurseries involve the germination of tropical rainforest seedlings in shaded conditions and transferral, at a later date, to environments with greater light intensities. Determination of the ability of these seedlings to acclimate to increased light intensities will allow seedling stock to be processed with maximum efficiency within the nursery. The acclimation abilities of three species, Agyrodendron actinophyllum, Cardwellia sublimis, and Flindersia brayleyana, commonly found in north Queensland's rainforests were investigated in this study. These particular species are highly valued for their cabinet timber qualities and are being reared in nurseries for use in reforestation trials and programs in north Queensland. Seedlings were initially raised in greenhouse conditions under two layers of shade cloth (16% of full sunlight) and then transferred into full sunlight at three different ages (3 weeks, 10 weeks, 14 weeks). Upon transfer, organ ratios and the direction of dry matter distribution was determined for each species and age group. Approximately 3 months after the seedlings were transferred, the acclimation ability of each species and age group was then determined. Dry matter distribution was found to change with age, irrespective of light environment. Individuals within a species with larger root systems and thicker or more dense leaves had a greater acclimation ability than those with smaller root systems and thinner or less dense leaves. Furthermore, individuals within a species whose dry matter distribution upon transfer was directed towards developing a large root system, and a small photosynthetic area and mass, had a greater acclimation ability than those whose dry matter distribution was directed away from such morphologies. Awareness of these relationships allows a better understanding of seedling response to gap formation in natural forests, and also allows plant nursery operators to make a more informed decision about when to move seedlings to environments with a higher light intensity.

Reforestation trials in the Khabarovsk Territory, Russia

Enormous areas of primary forest in Russia have been and continue to be destroyed by fire and harvesting. Almost all of these areas have been left to reforest naturally. Little reforestation by planting has been attempted and these efforts have met with limited success. Consequently vast areas are without forest cover and are unlikely to have a positive carbon balance. Weyerhaeuser Company initiated co-operative forest planting trials in the Khabarovsk Territory in 1989. Native seeds from this area were brought to the U.S. and used to produce high quality containerised seedlings. These seedlings were then used in research trials and small operational plantings in 1991 and 1992 near Vanino and Khabarovsk. In both 1993 and 1994, seedlings were provided for large-scale operational plantings in the Khabarovsk Territory. Seedling survival has generally been greater than 90% and growth has been excellent over a wide range of site conditions. The operational planting results demonstrate that contrary to local opinion, reforestation practices proven elsewhere can be used to successfully reforest sites that have been burned or harvested in this region. Key to the operational planting success were high quality seedlings, good logistical support and a well trained, organised and positively motivated work force.

Identifying fast-growing native trees from the neotropics using data from a large, permanent census plot

To screen for rapidly growing trees, lifetime growth histories of 160 species were estimated from data collected in a permanent 50 ha census plot in tropical moist forest in Panama. Most of the 160 species had never been studied before in detail, and newly encountered species with rapid growth might provide better techniques for reforesting degraded soils in Central America. To estimate lifetime growth, polynomial regressions were fitted to instantaneous growth rates expressed as a function of log-transformed diameter at breast height (dbh). These functions represent a differential equation in dbh, and explicit solutions for the equations provided dbh trajectories as a function of age (starting at 1 cm dbh, which was the smallest size included in the census). Dbh trajectories were calculated for 160 species, and full growth data are presented for the 28 species that ranked among the fastest 15 to reach a dbh of 10, 30, or 60 cm. Dbh trajectories based on growth of one standard deviation above the mean were also estimated for these species by fitting a polynomial regression to the residuals around the original regression. The fastest-growing tree in the 50 ha plot was the balsa, Ochroma pyramidale, which reached 10 cm in 5 years and 30 cm in 10. Cavanillesia platanifolia, Trema micrantha, Zanthoxylum belizense, and Vochysia ferruginea were the other top-ranking species. At mean growth, the top 15 ranking species required 5–25 years to reach 10 cm, 10–67 years to reach 30 cm, and 32–111 years to reach 60 cm, starting at 1 cm. At growth one standard deviation above the mean, the same species requried 4–18 years to reach 10 cm, 8–35 years to reach 30 cm, and 19–69 years to reach 60 cm dbh. We recommend that the little-known species from this list be further tested in reforestation trials.