ESTRUTURA ARBÓREA E SAZONALIDADE DA COBERTURA DO DOSSEL EM VEGETAÇÃO FLORESTADA E ABERTA NO PARQUE NACIONAL SERRA DE ITABAIANA, SERGIPE, BRASIL

The forest formations on quartz white-sand are a kind of oligotrophic ecosystem and its  phytophysionomical characteristics are affected by the climate seasonality. The canopy is one of these characteristics, its variations may influence the spatial distribution of the energy in the environment. The objective of this research was to evaluate and compare the tree density and the seasonality change on the canopy openness on habitats of white-sand in Serra de Itabaiana National Park. The data were collected in two environments: gaping vegetation of white-sands strictu sensu (VA) and closed vegetation of riparian forest (MR). To estimate tree density, it was utilized the wandering-quarter, where trees with CAP > 5cm were sampled. To evaluate the canopy dynamics, the transects had 5 points equidistant 20m, ten per environment. Hemispherical pictures were taken in January (dry season) and June (wet season), utilizing a digital camera with a fisheye lens. The images were analyzed on the Gap Light Analyzer software. The results showed that riparian forest have higher tree density (498 ind ha-1) than the opened (296 ind ha-1). The letter do not showed variations in the canopy openness (t = -2,0052; p > 0,05) or in Leaf Area Index (t = -2,0052; p > 0.05) between wet (52,24% ± 18,13% e 0,68 ± 0,45)  and dry seasons (67,39% ± 15,38% e 0,36 ± 0,23). In riparian forest, the canopy openness (t = 7,1739; p < 0.05) and LAI values (t = -5,1609; p < 0.05) vary between wet (13,70% ± 2,24% e 2,13 ± 0,23) and dry (21,08% ± 2,36% e 1,63 ± 0,20) seasons showing the seasonality. Differences between the two habitats highlights the environmental heterogeneity in Serra de Itabaiana and show that forest formations on white-sand respond by different ways to the water seasonality of this ecosystem. Because it is located in an ecotone area between evergreen forest and forest Semideciduous, the riparian forest tends to lose some of their leaves during the dry season. Moreover, the distribution pattern of the plants can contribute to the differences between the studied habitats.As florestas de areias brancas quartzosas constituem um tipo de ecossistema oligotrófico, cujos caracteres fitofisionômicos são afetados pela sazonalidade climática. Entre tais características está a abertura do dossel, cujas variações influenciam na distribuição espacial da luz solar no ambiente. Este estudo avaliou e comparou a estrutura da vegetação e as alterações sazonais do dossel em habitat de areias brancas do Parque Nacional Serra de Itabaiana, Sergipe. Os dados foram coletados em dois ambientes: vegetação aberta de areias brancas strictu sensu (VA) e mata fechada de vegetação ripária (MR). Para estimar a densidade arbórea utilizou-se o método quadrante, no qual foram amostradas árvores com CAP ≥ 5 cm. Para avaliar a dinâmica do dossel foram estabelecidos, em cada área, dois transectos compostos por cinco pontos equidistantes 20 m, totalizando 10 pontos por ambiente. Em cada ponto foram obtidas fotografias hemisféricas do dossel nos meses de janeiro (seca) e junho (chuva). As imagens foram analisadas pelo software Gap Light Analyzer, sendo avaliadas as variáveis abertura do dossel e índice de área foliar (IAF). A vegetação ripária apresentou densidade arbórea de 498 ind ha-1 e a vegetação aberta 296 ind ha-1. Esta última, não evidenciou variações na abertura do dossel (t = 2,0146; p > 0,05) e no IAF (t = -2,0052; p > 0,05) entre os períodos de chuva (52,24% ± 18,13% e 0,68 ± 0,45) e seca (67,39% ± 15,38% e 0,36 ± 0,23). Na mata ripária, a abertura do dossel (t = 7,1739; p < 0,05) e o IAF (t = -5,1609; p < 0,05) variou entre os períodos de chuva (13,70% ± 2,24% e 2,13 ± 0,23) e seca (21,08% ± 2,36% e 1,63 ± 0,20). As diferenças observadas destacam a heterogeneidade ambiental na Serra de Itabaiana e demonstram que as formações florestais de areias bancas respondem de maneira distinta à sazonalidade hídrica deste ecossistema.  Por estar localizada em uma área de ecótono entre floresta perene e Floresta Estacional Semidecidual, a mata ripária tende a perder parte de suas folhas durante o período seco. Além disso, o padrão de distribuição das plantas pode contribuir para as diferenças entre os habitat estudados

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

Influence of regional rainfall and Atlantic sea surface temperature on tree-ring growth of Poincianella pyramidalis, semiarid forest from Brazil

A tree-ring width chronology was developed from samples of thirteen Poincianella pyramidalis trees from the Caatinga semiarid region of northeastern Brazil, where the climate is characterized by marked seasonality in precipitation levels. Although a thin continuous marginal parenchyma band represents the limit of seasonal xylem production, and in spite of the presence of false rings, cross-dating is possible. In this sense, an interseries correlation of 0.572 was found indicating a considerable degree of consistency in the variability found among trees. Precipitation between January and July has a direct influence on growth, while a five month dry season interrupts the active division of cambial cells. A significant positive correlation was also found between sea surface temperatures (SSTs) in the tropical Atlantic and tree growth, but with a lag of six months. As the rainfall regime of northeastern Brazil presents a great deal of inter-annual variability due to fluctuations in global factors such as the SSTs of the tropical Atlantic and the intertropical convergence zone, the close relationship observed between P. pyramidalis tree growth and regional climate fluctuations appears as a logical plant-environment interaction that can be used as a reliable parameter for dendroecological inferences on tree growth dynamics and the reconstructions of past droughts in the Caatinga region.Fil: Pagotto, Mariana Alves. Universidade Federal de Sergipe; BrasilFil: Roig Junent, Fidel Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: de Souza Ribeiro, Adauto. Universidade Federal de Sergipe; BrasilFil: Lisi, Claudio Sergio. Universidade Federal de Sergipe; Brasi

Responses of tree-ring growth in Schinopsis brasiliensis to climate factors in the dry forests of northeastern Brazil

Key message This paper aims to provide evidences of the influence of physical atmospheric parameters on the growth of the endemic tree Schinopsis brasiliensis, and their consequent teleconnection with large-scale modes of climate variability affecting rainfall in semi-arid region of the Brazilian Northeast. Abstract The Brazilian Northeast is a region of low rainfall and high temperatures and evaporation. The surface temperature of the Atlantic Ocean (STA) modulates the rains in the Northeast in association with El Niño and La Niña (ENSO) events. Tree species that grow in this region, forming the tropical Caatinga dry forests, are subjected to long periods of drought. This study investigated the influence of climatic events on the secondary growth of a typical Caatinga tree species. The analysis was based on 39 samples of Schinopsis brasiliensis, from which we derived a chronology of tree-ring growth between 1963 and 2015, with an inter-correlation of 0.56, mean sensitivity of 0.53, and mean growth rate of 3.33 mm per year. Our results indicate that growth ring chronology is related directly to the rainy season, in addition to peaks in humidity associated with isolated downpours occurring during the dry season. On the other hand, air temperature, insolation, and evaporation revealed an inverse relationship with the chronology. Inter-correlations with ENSO events, STA, and precipitation were negative, while those between ENSO events and temperature were positive. Growth in S. brasiliensis is associated with the climatic anomalies of the region. Leaf-fall and cambial shutdown occur during the dry season, while the plant is predisposed for potential growth spurts during the intermittent rains that may occur from December onwards.Fil: Nogueira, Francisco Carvalho Jr.. Federal Institute of Sergipe; BrasilFil: Alves Pagotto, Mariana. Federal University of Sergipe; BrasilFil: Roig Junent, Fidel Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Lisi, Claudio Sergio. Federal University of Sergipe; BrasilFil: de Souza Ribeiro, Adauto. Federal University of Sergipe; Brasi

The hydrological performance of Prosopis juliflora (Sw.) growth as an invasive alien tree species in the semiarid tropics of northeastern Brazil

The fast-growing tree Prosopis juliflora was introduced into the drought-prone region of Caatinga in Brazil northeast some decades ago, forming now extensive populations that threaten native biodiversity and disrupt the physiognomy of the local flora. Semiarid tropical forests, such as those that occur in the Caatinga, experience periods of seasonal drought which interrupt cambial activity in woody plants, leading to the formation of annual growth rings that can be used to analyze tree age, growth variability over time and its interactions with climate. We produce a tree-ring width chronology of P. juliflora, in order to establish how this plant is linked to local climate variability, which in turn supports its role as an invasive species in the Caatinga forest. Statistical analyses of the potential effects of climatic variables on this chronology is related directly to the wet season (March–July) and torrential downpours occurring during the dry season (January–February). Moreover, the chronology is inversely related to mean temperature and insolation, which could potentially be linked to rapid loss of moisture in soils due to high temperatures. These findings provide important insights into the growth dynamics of this invasive species, which should contribute to the decision-making of managers and environmental agencies on the development of effective exotic forest management practices in the Caatinga region.Fil: Nogueira, Francisco de Carvalho. Instituto Federal de Sergipe; BrasilFil: Pagotto, Mariana Alves. Universidade Federal de Sergipe; BrasilFil: Aragão, José Roberto Vieira. Universidade Federal de Sergipe; BrasilFil: Roig Junent, Fidel Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Ribeiro, Adauto de Souza. Universidade Federal de Sergipe; BrasilFil: Lisi, Claudio Sergio. Universidade Federal de Sergipe; Brasi

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