Um novo ecossistema: florestas urbanas construídas pelo Estado e pelos ativistas

Historicamente, a expansão das cidades resultou na substituição da paisagem natural pela urbana, tendo como consequência a degradação ambiental por meio das mudanças na cobertura do solo, nos sistemas hidrológicos, nos ciclos biogeoquímicos, no clima e na biodiversidade, tornando as cidades especialmente vulneráveis às mudanças climáticas. A reversão desses processos é uma medida que visa a promoção da qualidade de vida nas cidades, na qual a arborização possui um papel fundamental por fornecer uma série de serviços ecossistêmicos valiosos para a promoção da biodiversidade, saúde e bem-estar social. Sendo direito de todos um meio ambiente equilibrado, saudável, de uso comum e essencial à qualidade de vida, o verde urbano é assunto interdisciplinar e de responsabilidade comum e generalizada. Cabe ao poder público a regularização, criação e manutenção dos plantios, promovendo o plantio de árvores a distâncias predeterminadas de acordo com o porte de cada espécie. Porém, os movimentos ativistas se desenvolveram no vácuo da morosidade do poder público seguindo, em geral, o método de adensamento de árvores pautado pelo conceito de sucessão ecológica. Ao promover a restauração dos serviços ecossistêmicos, as duas iniciativas de plantio arbóreo tendem a trazer grandes benefícios às grandes cidades, como São Paulo. Porém, a complexidade da paisagem urbana exige uma avaliação sistêmica dos plantios para definir a sua adequação espacial e otimizar os seus benefícios. O plantio das florestas urbanas não deve ter como objetivo recriar as condições naturais pré-urbanização, mas sim, desenvolver áreas verdes integradas à malha urbana que garantam um ambiente saudável e equilibrado, preservando as interações sociais. Ao visualizar o meio urbano como um ecossistema completo, é possível estabelecer critérios que otimizem os benefícios da arborização urbana. Estes critérios devem ser baseados em conhecimento técnico e científico, levando em conta necessidades sociais, para que o melhor método seja escolhido, caso a caso.Historically, the expansion of cities resulted in the replacement of natural landscape by urban environments, resulting in environmental degradation through changes in soil cover, hydrological systems, biogeochemical cycles, biodiversity, making cities particularly vulnerable to climate changes. Environmental restoration in cities is a measure to promote life quality, and urban forests play a key role in restoring the quality of the urban environment. They provide valuable ecosystem services for maintaining biodiversity, ensuring human health, and social well-being. As everyone has the right to live in a balanced, healthy and common use environment essential to suppor quality of life, urban green areas are an interdisciplinary issue of collective concern. It is the responsibility of the government to regulate, plant and manage urban trees in order to standardize urban afforestation by planting trees at predetermined distances according to the size of each species. However, the vacuum in the greening process left by the State is being filled by activists who, in general, use a different protocol that aims at higher tree density based on the notion of ecological succession. By promoting the restoration of ecosystem services, both initiatives tend to bring significant benefits to large cities such as São Paulo. However, the complexity of the urban landscape requires a systemic evaluation of tree planting to define spatial adequacy and optimize benefits. The planting of urban forests should not aim to recreate pre-urban natural conditions, but rather to develop green areas integrated to the urban network that guarantee a healthy and balanced environment while preserving social interactions. By perceiving the urban environment as a complete ecosystem, it is possible to establish criteria that optimize the benefits of urban afforestation. These criteria should be based on technical and scientific knowledge, and take into account social needs, so that the best method is chosen on a case-by-case basis

Intra-annual oxygen isotopes in the tree rings record precipitation extremes and water reservoir levels in the Metropolitan Area of São Paulo, Brazil

The impacts of climate change on precipitation and the growing demand for water have increased the water risks worldwide. Water scarcity is one of the main challenges of the 21st century, and the assessment of water risks is only possible from spatially distributed records of historical climate and levels of water reservoirs. One potential method to assess water supply is the reconstruction of oxygen isotopes in rainfall. We here investigated the use of tree-ring stable isotopes in urban trees to assess spatial/temporal variation in precipitation and level of water reservoirs. We analyzed the intra-annual variation of δ13C and δ18O in the tree rings of Tipuana tipu trees from northern and southern Metropolitan Area of São Paulo (MASP), Brazil. While variation in δ13C indicates low leaf-level enrichments from evapotranspiration, δ18O variation clearly reflects precipitation extremes. Tree-ring δ18O was highest during the 2014 drought, associated with the lowest historical reservoir levels in the city. The δ18O values from the middle of the tree rings have a strong association with the mid-summer precipitation (r = −0.71), similar to the association between the volume of precipitation and its δ18O signature (r = −0.76). These consistent results allowed us to test the association between tree-ring δ18O and water-level of the main reservoirs that supply the MASP. We observed a strong association between intra-annual tree-ring δ18O and the water-level of reservoirs in the northern and southern MASP (r = −0.94, r = −0.90, respectively). These results point to the potential use of high-resolution tree-ring stable isotopes to put precipitation extremes, and water supply, in a historical perspective assisting public policies related to water risks and climate change. The ability to record precipitation extremes, and previously reported capacity to record air pollution, place Tipuana tipu in a prominent position as a reliable environmental monitor for urban locations

Urban heat mitigation by green and blue infrastructure: drivers, effectiveness, and future needs

The combination of urbanisation and global warming leads to urban overheating and compounds the frequency and intensity of extreme heat events due to climate change. Yet, the risk of urban overheating can be mitigated by urban green-blue-grey infrastructures (GBGI), such as parks, wetlands, and engineered greening, which have the potential to effectively reduce summer air temperatures. Despite many reviews, the evidence bases on quantified GBGI cooling benefits remains partial and the practical recommendations for implementation are unclear. This systematic literature review synthesises the evidence base for heat mitigation and related co-benefits, identifies knowledge gaps, and proposes recommendations for their implementation to maximise their benefits. After screening 27,486 papers, 202 were reviewed, based on 51 GBGI types categorised under 10 main divisions. Certain GBGI (green walls, parks, street trees) have been well-researched for their urban cooling capabilities. However, several other GBGI have received negligible (zoological garden, golf course, estuary) or minimal (private garden, allotment) attention. The most efficient air cooling was observed in botanical gardens (5.0±3.5°C), wetlands (4.9±3.2°C), green walls (4.1±4.2°C), street trees (3.8±3.1°C), and vegetated balconies (3.8±2.7°C). Under changing climate conditions (2070-2100) with consideration of RCP8.5, there is a shift in climate subtypes, either within the same climate zone (e.g., Dfa to Dfb and Cfb to Cfa) or across other climate zones (e.g., Dfb (continental warm-summer humid) to BSk (dry, cold semi-arid) and Cwa (temperate) to Am (tropical)). These shifts may result in lower efficiency for the current GBGI in the future. Given the importance of multiple services, it is crucial to balance their functionality, cooling performance, and other related co-benefits when planning for the future GBGI. This global GBGI heat mitigation inventory can assist policymakers and urban planners in prioritising effective interventions to reduce the risk of urban overheating, filling research gaps, and promoting community resilience

Urban heat mitigation by green and blue infrastructure: drivers, effectiveness, and future needs

The combination of urbanisation and global warming leads to urban overheating and compounds the frequency and intensity of extreme heat events due to climate change. Yet, the risk of urban overheating can be mitigated by urban green-blue-grey infrastructures (GBGI), such as parks, wetlands, and engineered greening, which have the potential to effectively reduce summer air temperatures. Despite many reviews, the evidence bases on quantified GBGI cooling benefits remains partial and the practical recommendations for implementation are unclear. This systematic literature review synthesises the evidence base for heat mitigation and related co-benefits, identifies knowledge gaps, and proposes recommendations for their implementation to maximise their benefits. After screening 27,486 papers, 202 were reviewed, based on 51 GBGI types categorised under 10 main divisions. Certain GBGI (green walls, parks, street trees) have been well-researched for their urban cooling capabilities. However, several other GBGI have received negligible (zoological garden, golf course, estuary) or minimal (private garden, allotment) attention. The most efficient air cooling was observed in botanical gardens (5.0±3.5°C), wetlands (4.9±3.2°C), green walls (4.1±4.2°C), street trees (3.8±3.1°C), and vegetated balconies (3.8±2.7°C). Under changing climate conditions (2070-2100) with consideration of RCP8.5, there is a shift in climate subtypes, either within the same climate zone (e.g., Dfa to Dfb and Cfb to Cfa) or across other climate zones (e.g., Dfb (continental warm-summer humid) to BSk (dry, cold semi-arid) and Cwa (temperate) to Am (tropical)). These shifts may result in lower efficiency for the current GBGI in the future. Given the importance of multiple services, it is crucial to balance their functionality, cooling performance, and other related co-benefits when planning for the future GBGI. This global GBGI heat mitigation inventory can assist policymakers and urban planners in prioritising effective interventions to reduce the risk of urban overheating, filling research gaps, and promoting community resilience

Contrasting controls on tree ring isotope variation for Amazon floodplain and terra firme trees

Isotopes in tropical trees rings can improve our understanding of tree responses to climate. We assessed how climate and growing conditions affect tree-ring oxygen and carbon isotopes (δ18OTR and δ13CTR) in four Amazon trees. We analysed within-ring isotope variation for two terra firme (non-flooded) and two floodplain trees growing at sites with varying seasonality. We find distinct intra-annual patterns of δ18OTR and δ13CTR driven mostly by seasonal variation in weather and source water δ18O. Seasonal variation in isotopes was lowest for the tree growing under the wettest conditions. Tree ring cellulose isotope models based on existing theory reproduced well observed within-ring variation with possible contributions of both stomatal and mesophyll conductance to variation in δ13CTR. Climate analysis reveal that terra firme δ18OTR signals were related to basin-wide precipitation, indicating a source water δ18O influence, while floodplain trees recorded leaf enrichment effects related to local climate. Thus, intrinsically different processes (source water vs leaf enrichment) affect δ18OTR in the two different species analysed. These differences are likely a result of both species-specific traits and of the contrasting growing conditions in the floodplains and terra firme environments. Simultaneous analysis of δ13CTR and δ18OTR supports this interpretation as it shows strongly similar intra-annual patterns for both isotopes in the floodplain trees arising from a common control by leaf stomatal conductance, while terra firme trees showed less covariation between the two isotopes. Our results are interesting from a plant physiological perspective and have implications for climate reconstructions as trees record intrinsically different processes

Tropical tree growth driven by dry-season climate variability

Interannual variability in the global land carbon sink is strongly related to variations in tropical temperature and rainfall. This association suggests an important role for moisture-driven fluctuations in tropical vegetation productivity, but empirical evidence to quantify the responsible ecological processes is missing. Such evidence can be obtained from tree-ring data that quantify variability in a major vegetation productivity component: woody biomass growth. Here we compile a pantropical tree-ring network to show that annual woody biomass growth increases primarily with dry-season precipitation and decreases with dry-season maximum temperature. The strength of these dry-season climate responses varies among sites, as reflected in four robust and distinct climate response groups of tropical tree growth derived from clustering. Using cluster and regression analyses, we find that dry-season climate responses are amplified in regions that are drier, hotter and more climatically variable. These amplification patterns suggest that projected global warming will probably aggravate drought-induced declines in annual tropical vegetation productivity. Our study reveals a previously underappreciated role of dry-season climate variability in driving the dynamics of tropical vegetation productivity and consequently in influencing the land carbon sink.We acknowledge financial support to the co-authors provided by Agencia Nacional de Promoción Científica y Tecnológica, Argentina (PICT 2014-2797) to M.E.F.; Alberta Mennega Stichting to P.G.; BBVA Foundation to H.A.M. and J.J.C.; Belspo BRAIN project: BR/143/A3/HERBAXYLAREDD to H.B.; Confederação da Agricultura e Pecuária do Brasil - CNA to C.F.; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES, Brazil (PDSE 15011/13-5 to M.A.P.; 88881.135931/2016-01 to C.F.; 88887.199858/2018-00 to G.A.-P.; Finance Code 001 for all Brazilian collaborators); Conselho Nacional de Desenvolvimento Científico e Tecnológico - CNPq, Brazil (ENV 42 to O.D.; 1009/4785031-2 to G.C.; 311874/2017-7 to J.S.); CONACYT-CB-2016-283134 to J.V.-D.; CONICET to F.A.R.; CUOMO FOUNDATION (IPCC scholarship) to M.M.; Deutsche Forschungsgemeinschaft - DFG (BR 1895/15-1 to A.B.; BR 1895/23-1 to A.B.; BR 1895/29-1 to A.B.; BR 1895/24-1 to M.M.); DGD-RMCA PilotMAB to B.T.; Dirección General de Asuntos del Personal Académico of the UNAM (Mexico) to R.B.; Elsa-Neumann-Scholarship of the Federal State of Berlin to F.S.; EMBRAPA Brazilian Agricultural Research Corporation to C.F.; Equatorian Dirección de Investigación UNL (21-DI-FARNR-2019) to D.P.-C.; São Paulo Research Foundation FAPESP (2009/53951-7 to M.T.-F.; 2012/50457-4 to G.C.; 2018/01847‐0 to P.G.; 2018/24514-7 to J.R.V.A.; 2019/08783-0 to G.M.L.; 2019/27110-7 to C.F.); FAPESP-NERC 18/50080-4 to G.C.; FAPITEC/SE/FUNTEC no. 01/2011 to M.A.P.; Fulbright Fellowship to B.J.E.; German Academic Exchange Service (DAAD) to M.I. and M.R.; German Ministry of Education, Science, Research, and Technology (FRG 0339638) to O.D.; ICRAF through the Forests, Trees, and Agroforestry research programme of the CGIAR to M.M.; Inter-American Institute for Global Change Research (IAI-SGP-CRA 2047) to J.V.-D.; International Foundation for Science (D/5466-1) to M.I.; Lamont Climate Center to B.M.B.; Miquelfonds to P.G.; National Geographic Global Exploration Fund (GEFNE80-13) to I.R.; USA’s National Science Foundation NSF (IBN-9801287 to A.J.L.; GER 9553623 and a postdoctoral fellowship to B.J.E.); NSF P2C2 (AGS-1501321) to A.C.B., D.G.-S. and G.A.-P.; NSF-FAPESP PIRE 2017/50085-3 to M.T.-F., G.C. and G.M.L.; NUFFIC-NICHE programme (HEART project) to B.K., E.M., J.H.S., J.N. and R. Vinya; Peru ‘s CONCYTEC and World Bank (043-2019-FONDECYT-BM-INC.INV.) to J.G.I.; Peru’s Fondo Nacional de Desarrollo Científico, Tecnológico y de Innovación Tecnológica (FONDECYT-BM-INC.INV 039-2019) to E.J.R.-R. and M.E.F.; Programa Bosques Andinos - HELVETAS Swiss Intercooperation to M.E.F.; Programa Nacional de Becas y Crédito Educativo - PRONABEC to J.G.I.; Schlumberger Foundation Faculty for the Future to J.N.; Sigma Xi to A.J.L.; Smithsonian Tropical Research Institute to R. Alfaro-Sánchez.; Spanish Ministry of Foreign Affairs AECID (11-CAP2-1730) to H.A.M. and J.J.C.; UK NERC grant NE/K01353X/1 to E.G.Peer reviewe

Dendroecology of Hymenaea spp. and Podocarpus lambertii, the role of climate and environment on the growth of these tropical species

As árvores, por serem organismos sésseis, lidam com as variações ambientais, ao longo da vida, por meio de plasticidade tanto estrutural quanto funcional. As respostas a estas variações resultam em regimes de crescimento diferentes que podem ser reconstruídos por meio do estudo dos anéis de crescimento. As alterações ambientais, principalmente as alterações climáticas, têm o potencial de modular o crescimento e assim ficarem registradas nos anéis de crescimento. O estudo da interação entre a árvore e o ambiente é muito importante principalmente em um momento de transformações rápidas tanto no clima como na paisagem. O objetivo do presente estudo foi compreender como o clima e o ambiente modulam o crescimento de algumas espécies arbóreas tropicais. Neste estudo o crescimento é sinônimo de formação do lenho, o qual foi avaliado sob dois pontos de vista, o dos anéis de crescimento e o da formação do lenho com enfoque na deposição do cerne. Para isso, foram coletadas espécies de ampla distribuição, Hymenaea spp. (Leguminosaea) e Podocarpus lambertii (Podocarpaceae) que possuem anéis de crescimento visíveis. As populações de Hymenaea spp. foram coletadas em 10 localidades dentro de um gradiente latitudinal desde a linha do Equador até o Trópico de Capricórnio. A população de Podocarpus lambertii foi coletada num micro-refúgio no limite norte da distribuição desta espécie. Os resultados demonstram que tanto a precipitação quanto a temperatura influenciam o crescimento destas espécies. Estas relações entre o clima e o crescimento são dependentes do ambiente em que as árvores estão inseridas. As altas temperaturas se destacaram como um fator limitante do crescimento para as espécies estudadas. A temperatura também se destaca como um forte controlador da deposição do cerne em Hymenaea spp. Vale ressaltar que a deposição do cerne representa um alto custo para estas árvores e há um balanço entre a alocação de carbono para a formação da madeira produzida pelo câmbio e a deposição do cerne. A precipitação também é um fator importante para o crescimento destas espécies. Porém, a forma como as árvores respondem à variabilidade da precipitação parece ser dependente do ambiente em que estão inseridas. Por exemplo, árvores em ambientes de maior disponibilidade hídrica respondem melhor à precipitação da estação chuvosa, enquanto árvores em ambientes mais drenados, e menor disponibilidade hídrica, respondem à precipitação logo no início da estação chuvosa. Vale ressaltar que esta relação entre o crescimento das árvores e o clima pode ser enfraquecida pela fragmentação das florestas, tão comum nos ambientes tropicais. Conhecer como as árvores responderam a mudanças ambientais no passado é muito importante para tentar entender como elas responderão às rápidas mudanças ambientais e climáticas previstas para o futuro. De uma forma geral, um aumento na temperatura e uma diminuição na precipitação, ou uma concentração das chuvas em uma estação chuvosa mais curta, provavelmente terão um impacto negativo sobre o crescimento destas árvores. Entretanto, este efeito será dependente das condições ambientais nas quais as árvores estarão inseridas.Trees are sessile organisms that relate with constant environmental change through both structural and functional plasticity. Changes in the plasticity result in different growth rates through the life of trees that can be accessed by the study of tree rings. Environmental changes, especially climate, have the potential to modulate tree growth and, consequently, be recorded in the tree rings. The study of the interaction between trees and the environment is relevant in a time of fast changes in the landscape and climate. The aim of this study was to better understand how climate and landscape features modulate the growth of tropical tree species. In the present study, growth is analyzed as a synonym of wood formation. Additionally, it was analyzed under two points of view, the first one is the tree-ring analyzes and second one is the carbon allocation in the process of wood formation. To accomplish that, tree species with wide distribution were sampled, including Hymenaea spp. (Leguminosae) and Podocarpus lambertii (Podocarpaceae) both with distinct tree rings. The populations of Hymenaea spp. were sampled in ten sites across a latitudinal gradient from the Equator line to the Tropic of Capricorn. The population of P. lambertii was sampled in a micro refuge in the northern limit of this species distribution. Results show that both temperature and precipitation influence these species growth and that relation depends on the environment in which trees grow. High temperatures seem to be a key limiting factor for the studied specie growth. Moreover, temperature is also an important factor that controls the heartwood deposition in Hymenaea spp. It is important to note that the heartwood deposition represents a high carbon cost for these trees. Additionally, there is a trade-off between in the carbon allocation between the sapwood as produced by the cambium and the heartwood deposition. Precipitation is also a climate variable that influences these species growth. However, the precipitation influence seems to be more dependent on the environmental features of each population site. For instance, in sites higher water availability, trees\' growth is more dependent on the precipitation during the wet season, while in sites with lower water availability, and well-drained soils, trees\' growth is more dependent on the precipitation during the transition period between dry and wet seasons. It is important to highlight that forest fragmentation, commonly seem in tropical areas, has the potential to make this climate/growth relations weaker. Overall, an increase in air temperature and a decrease in the precipitation, or a concentration of it in a shorter wet season, will likely have a negative impact on trees growth. However, this effect will depend on the environmental characteristics of each population

Multi-proxy analysis on dendrocronology, anatomy and stable carbon isotopes of two species of jatobá (Hymenaea, Leguminosae) to identify possible atmospheric CO2 concentration and climate change effects

O desenvolvimento das atividades humanas está ocorrendo a um alto custo ambiental. A elevação das concentrações atmosféricas de CO2 e as mudanças no uso do solo estão desencadeando mudanças relevantes no clima global. O objetivo deste trabalho é determinar, por meio da largura dos anéis de crescimento, áreas de vasos e isótopos estáveis de carbono, como as espécies de jatobá: Hymenaea courbaril L. (de mata) e Hymenaea stigonocarpa Mart ex. Hayne (de cerrado) estão respondendo às mudanças do clima. Foram coletadas amostras do tronco principal de 12 indivíduos de H. stigonocarpa e 11 de H. courbaril. As amostras foram polidas e os anéis de crescimento foram identificados, datados e medidos. As cronologias foram construídas utilizando os programas COFECHA e ARSTAN. Com os anéis datados, foram medidas as áreas de vaso do lenho inicial de cada anel e também foram obtidas amostras de αcelulose dos anéis de crescimento para a análise de ∂13C e cálculo da eficiência intrínseca do uso da água (Wi). Os resultados mostram que, a largura dos anéis de H. courbaril sofre influencia positiva da precipitação, e negativa da temperatura, no final da estação de crescimento. Já as áreas de vaso são influenciadas positivamente pela precipitação do meio da estação de crescimento e negativamente pela temperatura da estação seca antes do início do crescimento. Para H. stigonocarpa, a largura do anel de crescimento sofre influência positiva da precipitação, e negativa da temperatura, durante a estação seca anterior ao início do crescimento. Já as áreas de vaso são influenciadas positivamente pela precipitação do início da estação seca anterior à estação de crescimento e negativamente pela temperatura no início do crescimento. Em relação ao ∂13C, as duas espécies mostraram uma influência do clima da estação de crescimento corrente e também da imediatamente anterior. Além disso, H. stigonocarpa possui uma tendência de elevação do Wi nas últimas cinco décadas que não foi encontrada em H. courbaril. Os resultados mostram que as espécies respondem a diferentes pressões ambientais, e isso levará a respostas diferentes em cenários de mudanças climáticas. Nesses cenários, as duas espécies podem ser prejudicadas, mas H. courbaril, possivelmente, sofrerá mais. Porém, existe outra pressão imediata sobre as espécies, que é o desmatamento. A análise das taxas de crescimento pode auxiliar as tomadas de decisão em projetos que envolvam supressão das matas e cerrados. Nesse contexto, H. stigonocarpa possui uma taxa de crescimento média 2.4x menor que a de H. courbaril, mostrando o maior tempo que essa espécie leva para atingir um tamanho maduro.The development of human activities is taking place at a high environmental cost. The increasing atmospheric CO2 concentrations and changes in land-use are unleashing relevant changes in global climatic. The objective of this study is to determinate how H. courbaril L. (from forest) and H. stigonocarpa Mart ex. Hayne (from cerrado) are responding to the climatic change through tree-ring width, vessel area and stable carbon isotope analysis. Twelve specimens of H. stigonocarpa and eleven of H. courbaril were sampled. Then, samples were polished and tree-rings were identified, dated, measured and chronologies were built using COFECHA and ARSTAN softwares. With tree-rings dated, early wood vessel areas were measured and α-celluloses were sampled from wood of each tree-ring to ∂13C analysis and intrinsic water-use efficiency estimation (Wi). The results shows that tree-ring width in H. courbaril are positively related with the precipitation, and negatively related to temperature, during the end of growth period. Also, vessel areas are positively related to precipitation during the middle growth period and negatively related with temperature during the dry season previous to growth period. Tree-rings width in H. stigonocarpa were positively related to precipitation during dry season previous to growth period and were negatively related to temperature during the same period. Also, vessel areas were positively related to precipitation during the beginning of dry season, previous to the current growth period, and negatively related to temperature during the beginning of growth period. In relation to ∂13C, climate signals were found during the current growth period and the previous one. Beyond that, H. stigonocarpa showed a clear increasing trend on i during the last five decades, that was not found in H. courbaril. The results indicate that these species respond to different environmental demands, and that shall lead to different responses regarding the climatic change scenarios. In these scenarios, both species shall be negatively influenced, which will be probably worse in H. courbaril. But, there is another immediate pressure on both species that is related with deforestation. The growth ratio analysis can help policy-makers in projects that have forest and cerrado suppression. In this context, H. stigonocarpa has a mean growth ratio 2.4x smaller than H. courbaril, what implicates longer time for those species reach a mature size

Climate/growth relations and teleconnections for a Hymenaea courbaril (Leguminosae) population inhabiting the dry forest on karst

Key message: Both water availability and temperature modulate the growth ofHymenaea courbarilon karst in Central Brazil. There is evidence of teleconnections between South Atlantic SST and tree growth. Abstract: Tropical dry forests have low annual precipitation and long dry seasons. Water availability, the main restrictive growth factor, becomes more pronounced in the shallow and highly porous soil of karst regions. Understanding how climate regulates tree growth in stressful environments is essential for predicting climate change impacts on trees. The aim of this study was to build a tree-ring chronology of Hymenaea courbaril growing in a karst dry forest and evaluate how local climate and teleconnections modulate its growth. To accomplish this, increment cores of 19 individuals were sampled in Terra Ronca State Park located in Goiás State, Central Brazil. After surface polishing, tree rings were identified, measured, dated, and a tree-ring chronology was built with 17 individuals. The chronology was correlated with local and regional climate data (temperature, precipitation, air humidity). We also tested teleconnections with sea surface temperature (SST) of the Equatorial Pacific and South Atlantic. Results show that air humidity, precipitation amount, and its distribution during the transition period between dry and wet seasons positively regulate this species growth. On the other hand, growth is negatively correlated with temperature during the middle of the previous year’s dry season. Additionally, growth is negatively correlated with SST of the Southern Atlantic, but not with Equatorial Pacific. These relationships between climate and growth indicate that predicted increases in regional temperature and decreases in water availability may limit the growth of H. courbaril in karst dry forests. © 2016, Springer-Verlag Berlin Heidelberg

A power-driven increment borer for sampling high-density tropical wood

High-density hardwood trees with large diameters have been found to damage manually operated increment borers, thus limiting their use in the tropics. Therefore, we herein report a new, low-cost gasoline-powered sampling system for high-density tropical hardwood trees with large diameters. This system provides increment cores 15 mm in diameter and up to 1.35 m in length, allowing minimally invasive sampling of tropical hardwood tree species, which, up to the present, could not be collected by conventional 5 or 10 mm increment borers. This system provides a single core sample with ample amount of wood for multidisciplinary analyses, including ring width, stable isotope and wood anatomical measurements. The borer never gets stuck inside stems, even in hollowed trees, cores will never twist during coring, and the gasoline drill gives ample flexibility in the field. It is anticipated that the dendrochronological community will find our technique very useful in the pursuit of tropical tree ring research