Improved tree height estimation of secondary forests in the Brazilian Amazon

This paper presents a novel approach for estimating the height of individual trees in secondary forests at two study sites: Manaus (central Amazon) and Santarém (eastern Amazon) in the Brazilian Amazon region. The approach consists of adjusting tree height-diameter at breast height (H:DBH) models in each study site by ecological species groups: pioneers, early secondary, and late secondary. Overall, the DBH and corresponding height (H) of 1,178 individual trees were measured during two field campaigns: August 2014 in Manaus and September 2015 in Santarém. We tested the five most commonly used log-linear and nonlinear H:DBH models, as determined by the available literature. The hyperbolic model: H = a.DBH/(b+DBH) was found to present the best fit when evaluated using validation data. Significant differences in the fitted parameters were found between pioneer and secondary species from Manaus and Santarém by F-test, meaning that site-specific and also ecological-group H:DBH models should be used to more accurately predict H as a function of DBH. This novel approach provides specific equations to estimate height of secondary forest trees for particular sites and ecological species groups. The presented set of equations will allow better biomass and carbon stock estimates in secondary forests of the Brazilian Amazon

TRY plant trait database – enhanced coverage and open access

Plant traits—the morphological, anatomical, physiological, biochemical and phenological characteristics of plants—determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait‐based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits—almost complete coverage for ‘plant growth form’. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait–environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives

Sprinting, climbing and persisting: Light interception and carbon gain in a secondary tropical forest succession

In the tropics human induced forest disturbance, i.e. timber extraction or forest slash and burn for agriculture is leading to an increase of secondary forest area. Therefore, people in the tropics, especially the poor, will rely on secondary forests for good and services. Pioneer trees (short-and long lived) and lianas are able to regenerate in forest fallows providing a variety of timber and non-timber products and environmental services. Information about the performance of pioneer trees and lianas under natural competition is crucial to understand the mechanism of canopy structure recovery and function and the patterns of species replacement during succession. Short-lived pioneers (SLPs) are able to rapidly dominate the canopy attaining an optimum in abundance during the first 4 years of succession. Long-lived pioneers (LLPs) remain in the understory and replace the SLPs later on. Lianas which are also abundant early in the succession, may play an important role in the regeneration process since they are thought to alter tree communities by suppressing slow-growing species, and thus indirectly promoting pioneer trees. Relatively few studies have addressed the characteristics that: enable SLPs to achieve early dominance, allow LLPs to persist below the short-lived ones early in succession, and enable lianas to successfully compete with trees. I studied the relationship of crown structure development and aboveground mass allocation to light interception and carbon gain of the ten most frequent species of trees and lianas found in naturally regenerating secondary tropical forest in Northern Bolivia. I applied a model approach to quantitatively assess the light requirements and use for species growth. The results showed that the disproportionate increase in size of SLPs and their consequent domination of the top of the canopy is associated to higher rates of carbon gain relative to the other species. These species showed also a high leaf turnover, thus as they get taller they may not be able to compensate their high biomass expenditure in leaves by their total carbon gain. The LLPs, due to their long leaf longevity had an advantage in terms of long term efficiency in light capture and carbon gain with respect to SLPs. This may enable them to persist for long periods in the understory and ultimately replace the SLPs as they die-off. Lianas showed similar characteristics to LLPs during their self-supporting juvenile phase, but once climbing, they had the advantage to convert mass more efficiently to height increment and leaf area production. This improved their chances to obtain light at lower mass investments in stems than LLPs but not SLPs trees. This suggests that lianas having similar leaf traits to LLPs are able to persist at lower light irradiances, but once they start climbing, they can successfully compete with the SLPs for a position in the higher layers of the canopy. The approach presented here can be extended to secondary forest management and restoration. The model makes it possible to match species light requirements with the light environment in which they are planted and this knowledge may increase the success of enrichment planting projects

Differences in biomass allocation, light interception and mechanical stability between lianas and trees in early secondary tropical forest

1. In early secondary successional forest, we analysed whether lianas convert mass more efficiently to height increment and leaf production, thus enabling them to capture more light per unit mass than trees. 2. Vertical biomass distribution, plant height, stem properties and crown structure were measured for individual plants of three short-lived pioneers (SLP), four long-lived pioneers (LLP) and three lianas in a 0.5 and 4-year-old secondary forest stand. Daily light interception per individual (Φp), and mean light interception per unit of leaf area (Φarea), leaf mass (Φleaf mass) and total above-ground mass (Φmass) were calculated with a canopy model. 3. In the 0.5-year-old stand lianas were mostly self-supporting and exhibited similar above-ground biomass allocation to height growth as trees. At this stage lianas were not more efficient in terms of light interception per unit mass (Φmass). In the fourth year lianas were mostly climbing and were taller relative to their mass, but exhibited lower buckling safety factors (BSFs). Their Φmass values became higher than those of the LLP, and equal to that of the SLP, Cecropia. The difference with the LLP was because the lianas captured more light per unit leaf area (Φarea) while they had a similar leaf area per unit mass (LAR: Φmass = LAR × Φarea). 4. These results show that as lianas go from being freestanding to climbing, they improve their chances to harvest light at lower mass investments in above-ground parts than the LLP but not SLP trees. At the same time, lianas have leaf traits similar to the LLP, which may enable them to persist at lower light availability.</p

Biomass allocation and leaf life span in relation to light interception by tropical forest plants during the first years of secondary succession

We related above-ground biomass allocation to light interception by trees and lianas growing in three tropical rain forest stands that were 0.5, 2 and 3-year-old regeneration stages after slash and burn agriculture. Stem height and diameter, leaf angle, the vertical distribution of total above-ground biomass and leaf longevity were measured in individuals of three short-lived pioneers (SLP), four later successional species (LS) and three lianas (L). Daily light capture per individual (¿d) was calculated with a canopy model. Mean daily light interception per unit leaf area (¿area), leaf mass (¿leaf mass) and above-ground mass (¿mass) were used as measures of instantaneous efficiency of biomass use for light capture. With increasing stand age, vegetation height and leaf area index increased while light at the forest floor declined from 34 to 5%. The SLP, Trema micanthra and Ochroma pyramidale, dominated the canopy early in succession and became three times taller than the other species. SLP had lower leaf mass fractions and leaf area ratios than the other groups and this difference increased with stand age. Over time, the SLP intercepted increasingly more light per unit leaf mass than the other species. Lianas, which in the earliest stage were self-supporting and started climbing later on, gradually became taller at a given mass and diameter than the trees. Yet, they were not more efficient than trees in light interception. SLP had at least three-fold shorter leaf life spans than LS and lianas. Consequently, total light interception calculated over the mean life span of leaves (¿leaf mass total = ¿area × SLAdeath leaves× leaf longevity) was considerably lower for the SLP than for the other groups. Synthesis. We suggest that early dominance in secondary forest is associated with a high rate of leaf turnover which in turn causes inefficient long-term use of biomass for light capture, whereas persistence in the shade is associated with long leaf life spans. This analysis shows how inherent tradeoffs in crown and leaf traits drive long-term competition for light, and it presents a conceptual tool to explain why early dominants are not also the long-term dominants

As espécies de tauari (Lecythidaceae) em florestas de terra firme da Amazônia: padrões de distribuição geográfica, abundâncias e implicações para a conservação "Tauari" species (Lecythidaceae) in non-flooded Amazon forest: patterns of geographic distribution, abundance, and implications for conservation

Conhecer a distribuição de uma espécie é essencial para o conhecimento de sua ecologia e conservação. Neste estudo, foram levantadas a composição, a abundância, a estrutura diamétrica e a distribuição geográfica das espécies de tauari (Lecythidaceae), um dos grupos de árvores mais explorados na Amazônia. Foram utilizados dados de herbários para definir a área de distribuição das espécies e inventários em seis áreas do bioma (totalizando 401,25 ha) para estimar abundâncias e estruturas diamétricas. Das 14 espécies ocorrentes na Amazônia, nove foram encontradas nos inventários. Couratari guianensis apresentou a maior área de distribuição contínua, porém sempre com densidades baixas. Couratari stellata apresentou a segunda maior área de distribuição, porém disjunta e, em geral, com densidades altas. Cariniana micrantha e Couratari multiflora apresentaram ampla distribuição e densidades variáveis, enquanto a maioria das demais espécies mostrou distribuição regional ou endêmica, e densidades menores que um indivíduo por hectare. A classificação das espécies em relação ao tipo de raridade divergiu daquelas descritas para Couratari guianensis e C. multiflora. Os resultados ressaltam a escassez de dados sobre espécies madeireiras nas regiões mais desmatadas da Amazônia, a necessidade do levantamento da abundância populacional local e regional para a melhor caracterização do seu padrão de distribuição e fornecem bases para a revisão das categorias e critérios de ameaças das espécies de Couratari na lista vermelha da IUCN.<br>Understanding the range of a species is essential to understanding its ecology and conservation. In this study we collected data on the composition, abundance, diametric structure, and geographic distribution of "tauari" species (Lecythidaceae), which are among the most exploited timber trees of the Amazonian forest. We used herbarium data to define the areas of distribution and inventories of 401.25 ha from six areas of Amazonia to list species for estimating abundance and diametric structure. Of the 14 species that occur in the biome, nine were sampled in the inventories. Couratari guianensis had the largest continuous area of distribution, but always at low densities. Couratari stellata had the second largest distribution, but it was discontinuous and usually at high densities. Cariniana micrantha and Couratari multiflora had wide distributions and variable densities, whereas most of the other species showed regional or restricted ranges and densities below one individual per hectare. The classification of species according to rarity type diverged from that described for Couratari guianensis and C. multiflora. These results point out the lack of data for timber species in the most deforested regions of Amazonia, the need for local and regional abundance investigation for better understanding of distribution patterns, and to provide support for reviewing the categories and criteria of threats of Couratari species on the IUCN Red List