Forest Restoration Plantations Research Articles

Potential native timber production in tropical forest restoration plantations

Restoring tropical forests still relies on expensive tree planting. Timber production from native trees offers a promising opportunity to make restoration financially viable, but species growth data are lacking. We assessed the potential of tropical forest restoration plantations for producing native timber in the Atlantic Forest. For that we inventoried a chronosequence of unmanaged restoration plantation sites with ten commercial native tree species. Then we developed growth models and used the Growth-Oriented Logging (GOL) method to inform targeted management decisions, including an optimized timber-focused scenario, based on growth and bole quality assessment. Usually, growth-rate classes for saw wood production would be defined according to the time necessary for achieving 35 cm in DBH. Harvesting age was markedly reduced using GOL for species of fast-growth (from <50 to <25 years), intermediate-growth (from 50 to 70 to 25–50 years), slow-growth (from >70 to 50–75 years). Following GOL, basal area was 42 ± 30% larger at harvest (taking 35 ± 23% more time) or 60 ± 16.5% smaller (taking 66 ± 16% less time). The optimized scenario speeded tree-size achievement and anticipated harvesting in an average of 58 years. Species selection, individualization, and silvicultural management are critical for producing timber in forest restoration programs.

SURVIVAL AND NATURAL REGENERATION OF FOREST ESSENCES CULTIVATED IN ALTERED AREAS THIRTY-FIVE YEARS AFTER PLANTING

The evaluation of the survival and natural regeneration of tree species in a 35-year-old plantation was carried out to identify the species established in the area, aiming at their recommendation in forest restoration plantations in the State of Acre. In the 1980s, 138 forest species were planted in two experimental units (EU), of 1.38 ha each, in the Zoobotanical Park (ZP) of the Federal University of Acre, Rio Branco campus. The main activities carried out in the area, prior to planting, were agriculture and cattle raising. Survival status was measured through a census of all individuals planted at the time, who were still alive. In addition, all regenerating individuals from planted species were surveyed in the effective planting area of the experimental units. At the time of evaluation, living individuals of 41 and 46 species were found in experimental units 1 (EU-1) and 2 (EU-2), respectively. The species Syagrus sancona, Talisia esculenta, Acacia polyphylla, Couepia bracteosa, Mangifera indica, Syzygium cumini and Copaifera multijuga showed survival rates above 90% in at least one of the experimental units. Only Syagrus sancona and Handroanthus serratifolius presented high survival rates in both experimental. Regenerating individuals of the species Aspidosperma vargasii, Couepia bracteosa, Euterpe precatoria, Handroanthus serratifolius, Oenocarpus mapora, Onychopetalum periquino and Stryphnodendron pulcherrimum were found in the two EU.

Silvicultural intensification has a limited impact on tree growth in forest restoration plantations in croplands

Investigating the impact of silvicultural practices on tropical forest restoration plantations is highly relevant, as there is a growing global demand for large-scale ecological restoration. The objective of this study was to test the hypothesis that native trees respond positively to the intensification of fertilization and weed control in a forest restoration plantation on a site previously used as cropland in the Atlantic Forest region of Brazil. We carried out a study with 22 native tree species, 11 of which were classified as shade species and the other 11 classified as diversity species. We implemented a randomized experimental design in a split-plot design, with six replicates of four treatments: intensive weed control (glyphosate spraying every 3 months) with and without fertilization, and non-intensive control (mechanical control every 6 months), with and without fertilization. We performed fertilization by supplying the site with 53 kg ha−1 of nitrogen, 35 kg ha−1 of phosphorus, and 51 kg ha−1 of potassium. We evaluated individual tree crown areas and increments in basal diameter and height 16 months after planting. In general, growth varied more among species than in weed control and fertilization treatments. Overall, the method of controlling weeds did not influence tree growth, but interacted with species for all growth variables. Fertilization increased tree diameter increment, and interacted with species, leading to diameter and height increments; however, most of the species did not respond to fertilization. Contrary to our expectations and previous findings, silvicultural intensification did not promote higher overall tree growth, probably because the restoration planting was conducted on a cropland with decades of intensive management, which increased soil fertility and reduced weed abundance through periodical maintenance prior to restoration planting. Our results highlight the importance of considering local and historical conditions to decide whether and when management intensification is required to accelerate tree growth in tropical forest restoration plantations.

Substrates for the production of Samanea saman (Jacq.) Merr seedlings inoculated with nitrogen-fixing bacteria and arbuscular mycorrhizal fungi

Samanea saman (Jacq.) Merr is a tree species widely used in forest restoration plantations and its symbiosis with nitrogen-fixing bacteria (NFB) and arbuscular mycorrhizal fungi (AMF) can promote seedling formation and establishment and growth in the field. The growth of S. saman seedlings inoculated with nitrogen-fixing bacteria and arbuscular mycorrhizal fungi grown on nine different substrates were evaluated in a greenhouse in this study. Seedling growth was promoted in substrates with lower bulk density and pH and higher total porosity, air-filled porosity and available Mg content. The nodulation of NFB was favored in the substrates with more available Mg, and AMF colonization and sporulation was favored in the substrates with a higher percentage of water buffering capacity. Seedlings produced on commercial substrates based on peat and pine bark showed superior growth. The peat-based “Carolina Soil™ electrical conductivity (EC) 0.7” favored nodulation, while the sewage sludge substrates and clayey subsoil mixture plus 10% poultry litter (V:V) promoted mycorrhizal colonization and sporulation.

Monitoring the structure of forest restoration plantations with a drone-lidar system

We are in an unprecedented moment for promoting forest restoration globally, with international and regional pledges to restore at least 350 million hectares by 2030. To achieve these ambitious goals, it is necessary to go beyond traditional plot-scale assessments and develop cost-effective technologies that can monitor the structure and function of restored forests at much broader scales. Lidar remote sensing in unmanned aerial vehicle (UAV) platforms can be an agile and autonomous method for monitoring forest restoration projects, especially under conditions when information updates are frequently needed in relatively small areas or, when using an airplane-borne lidar system may be not financially viable. Here, we explored the potential of an UAV-borne lidar system to assess the outcomes of a mixed-species restoration plantation experiment, designed to maximize aboveground biomass (AGB) accumulation. The experiment was established in Brazil’s Atlantic Forest, with 20 native tree species, by combining two levels of planting density and two management levels, totaling four treatment combinations and one control (plots left over for natural regeneration). We analyzed three structural variables from lidar data (canopy height, gap fraction and leaf area index) and one from field inventory data (AGB). Structural differences between the treatments and the control plots were reliably distinguished by the UAV-borne lidar system. AGB was strongly correlated with canopy height, allowing us to elaborate a predictive equation to use the UAV-borne lidar system for monitoring structural features in other restoration plantations in the region. UAV-borne lidar systems showed enormous potential for monitoring relatively broad-scale (thousands of hectares) forest restoration projects, providing an important tool to aid decision making and accountability in forest landscape restoration.

Seed and microsite limitations of large-seeded, zoochorous trees in tropical forest restoration plantations in northern Thailand

On deforested or degraded land, planting mixtures of native forest tree species facilitates establishment of incoming tree seedling species (species recruitment) by rapidly re-establishing canopy cover. However, delayed colonization of plantations by large-seeded, zoochorous (LSZ) tree species can affect the species composition, structure, and function of the developing forest. The objective of this study was to investigate whether microsites limit establishment (germination and early seedling survival) of LSZ tree species in three 13-year-old, seasonally dry, tropical forest restoration plantations in northern Thailand. We conducted a seed sowing experiment that combined five LSZ tree species with four microsite treatments in a split-plot design. All five tree species were previously absent from the understory of the plantations, despite seed sources being present in nearby natural forest. The four treatments simulated potential microsites that naturally-dispersed seeds may encounter. They included seed deposition on the surface of soil and on leaf litter, as well as seed burial beneath soil and beneath leaf litter. We fenced the experimental areas to prevent seed predation and focus on the environmental effects of microsites on the different stages of seedling establishment. Following seed sowing, we measured germination and seedling survival, mean height, and stem diameter over 26 months. The microsites treatments did not significantly affect germination and seedling survival, providing strong evidence that establishment of the tested species was not limited by the applied microsite environments. Furthermore, although there were significant differences in germination and survival among species, relatively high overall germination (37%) and 26-month seedling survival (58.5%), irrespective of microsite treatment, suggested that environmental conditions in the 13-year-old plantations generally met the requirements for germination and early seedling establishment. Microsite treatments also did not correlate with seedling height or stem diameter at 20 months, suggesting that initial germination microsites have no effect on seedling growth and robustness. Taken together, the results of this investigation support the hypothesis that seedlings of LSZ tree species are slow to colonize tropical forest restoration plantations because of seed limitations resulting from inadequate seed dispersal or low seed availability. The successful establishment of LSZ seedlings from sown seeds in this experiment suggests that direct seeding beneath the canopy of restoration plantations may be an effective way to offset seed dispersal limitations in restoration plantations. Furthermore, the absence of microsite treatment effects suggests broadcast sowing of seeds may be a simple way to recolonize closed-canopy restoration plantations with LSZ tree species.

How can my research paper be useful for future meta-analyses on forest restoration plantations?

Statistical meta-analysis is a powerful and useful tool to quantitatively synthesize the information conveyed in published studies on a particular topic. It allows identifying and quantifying overall patterns and exploring causes of variation. The inclusion of published works in meta-analyses requires, however, a minimum quality standard of the reported data and information on the methodology used. Our experience with conducting a meta-analysis on the relationship between seedling quality and field performance is that nearly one third of the apparently relevant publications had to be discarded because essential data, usually statistical dispersion parameters, were not properly reported. In addition, we encountered substantial difficulty to explore the effect of covariates due to the poor description of nursery cultivation methods, plantation location, and management in a significant proportion of the selected primary studies. Thus, we present guidelines for improving methodology detail and data presentation so that future forest restoration-oriented research can be more readily incorporated into meta-analyses. In general, research studies should report data on means, sample size, and any measure of variation even if they are not statistically significant. The online availability of raw data is the best practice to facilitate the inclusion of primary research on meta-analyses. Providing full information about the production of nursery seedlings, such as plant material and experimental conditions, is essential to test whether these procedures might have an effect on seedling quality. In addition, detailed information about field trials such as site climate, soil preparation techniques, previous land use, or post-plantation management, is needed to elucidate whether seedling quality is context-dependent. Thus, we provide a detailed checklist of important information that should be included when reporting forest restoration research involving the use of nursery-produced seedlings. All this will help to quantitatively synthetize current state-of-knowledge and thus contribute to the advancement of the forest restoration discipline.

Carbon and nutrient stocks of three Fabaceae trees used for forest restoration and subjected to fertilization in Amazonia.

Amazonia is crucial to global carbon cycle. Deforestation continues to be one of the main causes of the release of C into the atmosphere, but forest restoration plantations can reverse this scenario. However, there is still diffuse information about the C and nutrient stocks in the vegetation biomass. We investigated the carbon and nutrient stocks of Fabaceae trees (Inga edulis, Schizolobium amazonicum and Dipteryx odorata) subjected to fertilization treatments (T1 - no fertilization; T2 - chemical; T3 - organic; and T4 - organic and chemical fertilization) in a degraded area of the Balbina Hydroelectric Dam, AM - Brazil. As an early successional species, I. edulis stocked more C and nutrients than the other two species independent of the fertilization treatment, and S. amazonicum stocked more C than D. odorata under T1 and T4. The mixed species plantation had the potential to stock 4.1 Mg C ha-1 year-1, while I. edulis alone could stock 9.4 Mg C ha-1 year-1. Mixing species that rapidly assimilate C and are of significant ecological and commercial value (e.g., Fabaceae trees) represents a good way to restore degraded areas. Our results suggest that the tested species be used for forest restoration in Amazonia.

Recovery of genetic diversity levels of a Neotropical tree in Atlantic Forest restoration plantations

To support the long-term ecological viability of restoration projects, it is necessary to reach adequate levels of genetic diversity in spontaneously recolonizing and reintroduced populations. The importance of genetic diversity in the long-term viability of populations is acknowledged, but still poorly monitored in restoration projects. This study aimed to estimate the genetic diversity and inbreeding levels of populations of a tree species widely used in restoration projects in the Atlantic Forest of Brazil, Centrolobium tomentosum, exploring the potential of active restoration in successfully reestablishing populations with higher chances of long-term perpetuation in agricultural landscapes. We used both nuclear and chloroplast microsatellite markers to assess genetic parameters in juveniles and adult individuals in two high-diversity restoration plantations (28 and 60years old), one disturbed fragment, and one large and well conserved protected area. We observed similar levels of genetic diversity and inbreeding, for juveniles and adults, in both restored and natural populations. Surprisingly, haplotype diversity was higher in restoration sites. We also found private alleles in juveniles in both restoration areas, and this is evidence of gene flow between restored and neighboring natural populations. However, we observed negative effects of inbreeding on the effective population size of populations from the disturbed natural remnant and restoration areas. These results provide evidence of the capacity of restoration plantations for recovering high levels of genetic diversity and the importance of maintaining large and well-conserved forest remnants to be used as seed sources for restoration efforts.

Microsite determinants of variability in seedling and cutting establishment in tropical forest restoration plantations

AbstractPlantations are frequently established on abandoned pasture lands to speed forest recovery. This strategy requires matching a tree species mix with the prevailing microenvironmental conditions. In four degraded pastures of the Mexican Lacandon rainforest, we planted 2,400 trees of 6 species (Guazuma ulmifolia, Inga vera, Ochroma pyramidale, Trichospermum mexicanum, Bursera simaruba, and Spondias mombin) to (1) test survival, initial growth, and establishment costs; (2) evaluate whether vegetative cuttings outperform direct seeding or transplants of nursery‐raised seedlings; (3) determine tree response to herbaceous dominance and soil compaction; and (4) scrutinize the results' consistency across sites and sampling scales of tree–microenvironment interactions (individual tree vs. averaged plot responses). After 2 years, overall survival and growth rates were high for 2 of 3 nursery‐raised species. Contrary to expectations, all seedlings outperformed the cuttings while direct seeding resulted in a cost‐effective option of intermediate efficacy. The impact of soil resistance to root penetration on tree biomass accumulation was species dependent while bulk density was not relevant. Soil‐covering, herbaceous vegetation accelerated growth in 3 of 4 tested species during the dry season. At this initial stage of forest restoration in abandoned pastures, Guazuma and Trichospermum were the most restoration‐effective species. Costs can be reduced by using direct‐seeding Inga and avoiding weeding during the dry season. Finally, our results demonstrate how species selection trials can be misleading due to site variations in tree response and to sampling scales that fail to account for small‐scale environmental heterogeneity. We recommend ways to improve the design of restoration trials.

Animal-dispersed pioneer trees enhance the early regeneration in Atlantic Forest restoration plantations

Planting of native trees has been adopted in many tropical regions worldwide as a central forest restoration method, but little is known concerning the role that these planted species play in catalyzing forest regeneration beneath their canopies. We investigated the role of animal-dispersed tree species in catalyzing the regeneration of woody species in the understory of restoration plantings. We assessed both the density and richness of tree seedlings within plots located beneath the canopy of both animal-dispersed and abiotic-dispersed tree species planted in three riparian forest restoration sites with ages of five, six and eight years. The proportion of animal-dispersed tree seedlings increased with plantation age. The richness of animal-dispersed tree seedlings was higher beneath animal-dispersed trees in the eight-year-old planting. The density of animal-dispersed tree seedlings was higher under animal-dispersed trees when sites were analyzed altogether. The top three species in regeneration density beneath the canopy were animal-dispersed trees, and from the top ten, seven were animal-dispersed species. We suggest that animal-dispersed pioneer trees which facilitate natural regeneration and promote a high density and richness of woody species beneath their canopies should be considered as “framework” species for tropical forest restoration.