Floristics of floodplain 'murundus' of the Pantanal of Araguaia, Mato Grosso, Brazil

O presente estudo teve como objetivo determinar e comparar a riqueza e a composição de espécies de angiospermas entre campos de murundus (CM) do Parque Estadual do Araguaia (PEA), em uma das maiores planícies de inundação do Brasil. O PEA localiza-se em Novo Santo Antônio, Mato Grosso, sendo delimitado a leste pelo Rio Araguaia e a oeste pelo Rio das Mortes. Foram realizadas coletas intensivas da flora em 11 hectares, e áreas adjacentes, de CM distribuídos ao longo do PEA. Estudos do meio físico foram realizados através de descrições in situ. Os solos são do tipo Plintossolo, hidromórficos minerais, profundos, imperfeitamente a mal drenados, com baixa permeabilidade. No total foram coletadas 318 espécies, 193 gêneros e 66 famílias. Nos CM os valores variaram de 51 a 135 espécies, 42 a 107 gêneros e 27 a 52 famílias. Erythroxylum suberosum foi considerada uma espécie típica de CM brasileiros, Curatella americana típica de CM de Mato Grosso e Byrsonima cydoniifolia típica do PEA. O padrão físico e de distribuição espacial dos murundus pode ser um reflexo do pulso de inundação sazonal, visto que a composição florística dos campos de murundus variou entre as áreas de influência dos rios que delimitam o parque. Este foi o maior levantamento florístico já realizado em CM, permitindo relevante ampliação do conhecimento e registro de espécies típicas do Bioma Cerrado e que ocorrem nessa fitofisionomia.This study aimed to compare angiosperm species richness and composition between floodplain 'murundus' (FM) of Araguaia State Park (ASP) in one of Brazil´s largest floodplains. ASP is located in Novo Santo Antônio, Mato Grosso state, and is bordered on the east by the Araguaia River, and on the west by Das Mortes River. Intensive floristic inventories were made on 11 hectares, and adjacent areas, of FM distributed over ASP. Environmental studies were performed by in situ descriptions. The soils are deep, mineral hydromorphic plinthosols, imperfectly to poorly drained, with low permeability. A total of 318 species, 193 genera and 66 families were collected, and FM values ranged from 51 to 135 species, 42 to 107 genera and 27 to 52 families. Erythroxylum suberosum is a typical species of Brazilian FM, Curatella americana typical of Mato Grosso FM and Byrsonima cydoniifolia typical of the ASP. The physical and spatial distribution pattern of the "murundus" (earthmounds) may reflect the seasonal flood pulse, since the floristic composition of the FM varied between the areas under the influence of the rivers that border the park. This was the largest floristic inventory ever undertaken in FM, with a significant increase in our knowledge and recording of typical species of the Cerrado Biome which occur in this phytophysiognomy

Basin-wide variation in tree hydraulic safety margins predicts the carbon balance of Amazon forests

ests face increasing climate risk, yet our ability to predict their response to climate change is limited by poor understanding of their resistance to water stress. Although xylem embolism resistance thresholds (for example, Ψ50) and hydraulic safety margins (for example, HSM50) are important predictors of drought-induced mortality risk, little is known about how these vary across Earth’s largest tropical forest. Here, we present a pan-Amazon, fully standardized hydraulic traits dataset and use it to assess regional variation in drought sensitivity and hydraulic trait ability to predict species distributions and long-term forest biomass accumulation. Parameters Ψ50 and HSM50 vary markedly across the Amazon and are related to average long-term rainfall characteristics. Both Ψ50 and HSM50 influence the biogeographical distribution of Amazon tree species. However, HSM50 was the only significant predictor of observed decadal-scale changes in forest biomass. Old-growth forests with wide HSM50 are gaining more biomass than are low HSM50 forests. We propose that this may be associated with a growth–mortality trade-off whereby trees in forests consisting of fast-growing species take greater hydraulic risks and face greater mortality risk. Moreover, in regions of more pronounced climatic change, we find evidence that forests are losing biomass, suggesting that species in these regions may be operating beyond their hydraulic limits. Continued climate change is likely to further reduce HSM50 in the Amazon, with strong implications for the Amazon carbon sink

Soil water-holding capacity and monodominance in Southern Amazon tropical forests

Background and aims: We explored the hypothesis that low soil water-holding capacity is the main factor driving the monodominance of Brosimum rubescens in a monodominant forest in Southern Amazonia. Tropical monodominant forests are rare ecosystems with low diversity and high dominance of a single tree species. The causes of this atypical condition are still poorly understood. Some studies have shown a relationship between monodominance and waterlogging or soil attributes, while others have concluded that edaphic factors have little or no explanatory value, but none has accounted for soil-moisture variation other than waterlogging. This study is the first to explicitly explore how low soil water-holding capacity influences the monodominance of tropical forests. Methods: We conducted in situ measurements of vertical soil moisture using electrical resistance collected over 1 year at 0–5; 35–40 and 75–80 cm depths in a B. rubescens monodominant forest and in an adjacent mixed-species forest in the Amazon-Cerrado transition zone, Brazil. Minimum leaf water potential (Ψmin) of the seven most common species, including B. rubescens, and soil water-holding capacity for both forests were determined. Results: The vertical soil moisture decay pattern was similar in both forests for all depths. However, the slightly higher water availability in the monodominant forest and Ψmin similarity between B. rubescens and nearby mixed forest species indicate that low water-availability does not cause the monodominance. Conclusions: We reject the hypothesis that monodominance of B. rubescens is primarily determined by low soil water-holding capacity, reinforcing the idea that monodominance in tropical forests is not determined by a single factor

Basin-wide variation in tree hydraulic safety margins predicts the carbon balance of Amazon forests

Funding: Data collection was largely funded by the UK Natural Environment Research Council (NERC) project TREMOR (NE/N004655/1) to D.G., E.G. and O.P., with further funds from Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brasil (CAPES, finance code 001) to J.V.T. and a University of Leeds Climate Research Bursary Fund to J.V.T. D.G., E.G. and O.P. acknowledge further support from a NERC-funded consortium award (ARBOLES, NE/S011811/1). This paper is an outcome of J.V.T.’s doctoral thesis, which was sponsored by CAPES (GDE 99999.001293/2015-00). J.V.T. was previously supported by the NERC-funded ARBOLES project (NE/S011811/1) and is supported at present by the Swedish Research Council Vetenskapsrådet (grant no. 2019-03758 to R.M.). E.G., O.P. and D.G. acknowledge support from NERC-funded BIORED grant (NE/N012542/1). O.P. acknowledges support from an ERC Advanced Grant and a Royal Society Wolfson Research Merit Award. R.S.O. was supported by a CNPq productivity scholarship, the São Paulo Research Foundation (FAPESP-Microsoft 11/52072-0) and the US Department of Energy, project GoAmazon (FAPESP 2013/50531-2). M.M. acknowledges support from MINECO FUN2FUN (CGL2013-46808-R) and DRESS (CGL2017-89149-C2-1-R). C.S.-M., F.B.V. and P.R.L.B. were financed by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brasil (CAPES, finance code 001). C.S.-M. received a scholarship from the Brazilian National Council for Scientific and Technological Development (CNPq 140353/2017-8) and CAPES (science without borders 88881.135316/2016-01). Y.M. acknowledges the Gordon and Betty Moore Foundation and ERC Advanced Investigator Grant (GEM-TRAITS, 321131) for supporting the Global Ecosystems Monitoring (GEM) network (gem.tropicalforests.ox.ac.uk), within which some of the field sites (KEN, TAM and ALP) are nested. The authors thank Brazil–USA Collaborative Research GoAmazon DOE-FAPESP-FAPEAM (FAPESP 2013/50533-5 to L.A.) and National Science Foundation (award DEB-1753973 to L. Alves). They thank Serrapilheira Serra-1709-18983 (to M.H.) and CNPq-PELD/POPA-441443/2016-8 (to L.G.) (P.I. Albertina Lima). They thank all the colleagues and grants mentioned elsewhere [8,36] that established, identified and measured the Amazon forest plots in the RAINFOR network analysed here. The authors particularly thank J. Lyod, S. Almeida, F. Brown, B. Vicenti, N. Silva and L. Alves. This work is an outcome approved Research Project no. 19 from ForestPlots.net, a collaborative initiative developed at the University of Leeds that unites researchers and the monitoring of their permanent plots from the world’s tropical forests [61]. The authros thank A. Levesley, K. Melgaço Ladvocat and G. Pickavance for ForestPlots.net management. They thank Y. Wang and J. Baker, respectively, for their help with the map and with the climatic data. The authors acknowledge the invaluable help of M. Brum for kindly providing the comparison of vulnerability curves based on PAD and on PLC shown in this manuscript. They thank J. Martinez-Vilalta for his comments on an early version of this manuscript. The authors also thank V. Hilares and the Asociación para la Investigación y Desarrollo Integral (AIDER, Puerto Maldonado, Peru); V. Saldaña and Instituto de Investigaciones de la Amazonía Peruana (IIAP) for local field campaign support in Peru; E. Chavez and Noel Kempff Natural History Museum for local field campaign support in Bolivia; ICMBio, INPA/NAPPA/LBA COOMFLONA (Cooperativa mista da Flona Tapajós) and T. I. Bragança-Marituba for the research support.Tropical forests face increasing climate risk1,2, yet our ability to predict their response to climate change is limited by poor understanding of their resistance to water stress. Although xylem embolism resistance thresholds (for example, Ψ50) and hydraulic safety margins (for example, HSM50) are important predictors of drought-induced mortality risk3-5, little is known about how these vary across Earth's largest tropical forest. Here, we present a pan-Amazon, fully standardized hydraulic traits dataset and use it to assess regional variation in drought sensitivity and hydraulic trait ability to predict species distributions and long-term forest biomass accumulation. Parameters Ψ50 and HSM50 vary markedly across the Amazon and are related to average long-term rainfall characteristics. Both Ψ50 and HSM50 influence the biogeographical distribution of Amazon tree species. However, HSM50 was the only significant predictor of observed decadal-scale changes in forest biomass. Old-growth forests with wide HSM50 are gaining more biomass than are low HSM50 forests. We propose that this may be associated with a growth-mortality trade-off whereby trees in forests consisting of fast-growing species take greater hydraulic risks and face greater mortality risk. Moreover, in regions of more pronounced climatic change, we find evidence that forests are losing biomass, suggesting that species in these regions may be operating beyond their hydraulic limits. Continued climate change is likely to further reduce HSM50 in the Amazon6,7, with strong implications for the Amazon carbon sink.Publisher PDFPeer reviewe

Effects of fire on the woody and herbaceous vegetation presented In “Campos de Murundu” of the Parque Estadual do Araguaia (Pea) - MT

Dissertação (mestrado)—Universidade de Brasília, Departamento de Engenharia Florestal, 2010.Os campos de murundus (CMs) são formados por área plana ocupada pelo estrato herbáceo, inundável no período chuvoso, onde estão inseridos microrelevos ou murundus de terra cobertos por vegetação lenhosa típica do Cerrado. São encontrados principalmente no Brasil Central e ainda são pouco estudados. O estudo foi realizado em área amostral de 1 ha de CM no Parque Estadual do Araguaia (PEA), em Mo Grosso, com ocorrência de duas queimadas (2006 e 2007). Dois levantamentos foram realizados: antes da queimada (2005) e pós queimada (2008), com o intuito de analisar as mudanças florísticas e estruturais da vegetação herbácea e arbórea durante o período de três anos. Para avaliar o componente herbáceo-subarbustivo, a área de 1 ha foi dividida em 16 parcelas de 25 X 25 m cada. Para quantificar a vegetação herbáceo-subarbustiva utilizou-se um quadro de madeira (1 m X 1 m) lançado aleatoriamente duas vezes em cada parcela. Foram amostradas 35 espécies, 25 gêneros e 15 famílias. A diversidade foi de H’ = 2,38 nats. ind.-1em 2005 e H’ = 1,91 nats.ind. -1 em 2008. Os valores de H’ diferiram entre si entre os levantamentos (t = 4,86; p = 0,05). Para ambos o índice J’ foi de 0,91. As famílias com maior riqueza foram Poaceae (9 espécies) e Cyperaceae (5). Houve mudança na composição florística, na cobertura e na frequência da comunidade e das populações. A família que se destacou em cobertura e frequência foi Poaceae. Aristida pendula e Trachypogon plumosus foram as espécies que mais alteraram em cobertura e frequência relativa entre os levantamentos. Com relação ao componente arbustivo-arbóreo foi realizado o inventário da área de 1 ha, medindo-se todos os indivíduos com CAS ≥ 9 cm e suas alturas. Em 2008, foram avaliados todos os indivíduos sobreviventes de 2005, os indivíduos recrutas e também foram medidos CAS de todas as rebrotas ≤ 9 cm que apresentaram morte da parte aérea (top kill). Ocorreu mudança na estrutura e a composição florística do componente arbóreo se manteve, exceto para Protium unifoliolatum que não foi registrado na amostragem em 2008. Ao todo, foram amostrados 40 espécies, 34 gêneros e 23 famílias. A densidade diminuiu e a área basal aumentou no segundo levantamento. A frequência relativa foi o parâmetro que mais influenciou o IVI das espécies, seguida pela densidade relativa e dominância relativa. As dez espécies mais importantes em IVI mantiveram entre os levantamentos, mas em posições diferentes. Curatella americana e Andira cuyabensis foram as espécies com maior IVI, devido principalmente a dominância na área. As distribuições de diâmetros e de alturas apresentaram diferenças entre os dois levantamentos. Em 2008, surgiu uma nova classe de diâmetros (0 a 2,8 cm), devido ao decréscimo dos indivíduos que desenvolveram rebrotas com menores diâmetros após top kill. A taxa média anual de recrutamento (1,16%.ano-1 ) foi menor do que a taxa de mortalidade (2,95.ano-1), confirmando a diminuição da densidade. A mortalidade total foi de 9,3% e a taxa de caules destruídos foi de 33%. 70% dos indivíduos mortos apresentavam diâmetros entre 4,2 a 7,3 cm e 52% com altura entre 2 a 3 m. 35% dos indivíduos na área sofreram dano parcial com rebrota. Em 2008, foram quantificados 429 rebrotas contra 156 em 2005. 95% dos diâmetros das rebrotas em 2008 não ultrapassaram 2,22 cm. A interferência de queimadas na área durante os anos de estudo contribuiu para as mudanças na vegetação do CM. _______________________________________________________________________________ ABSTRACTThe ―Campos de Murundus‖ (CMs) are seasonally flooded landscapes of the Cerrado biome, characterized by many earthmounds covered by cerrado woody vegetation and scattered over a grassland surface. These kinds of landscapes are found especially in Central Brazil and there is a huge lack of works. The total area of CMs sampled in this work was one hectare (1 ha), that was burned in 2006 and 2007. The data were raised before and after two burnings events (2005 and 2008) in order to compare and analyze the floristic and structural changes of the vegetation in three years. To evaluate the herbaceous-shrub component, the total sampled area of one hectare was sub-divided in 16 plots of 25 X 25 m each. A 1 X 1m board was used surround a ball that was randomly launched twice for each plot to obtain the quantitative data. The sampling resulted in 35 species, 25 genera and 15 families. The species diversity calculated in 2005 was H’= 2.38 nats/individual and in 2008 was H’ = 1.91 nats/individual. The values calculated for diversity differed (t = 4.86; p = 0.05) between 2005 and 2008. For both sampled years the Pielou index (J’) calculated was 0.91. The families that presented higher values for richness in both sampled years were Poaceae (9 species) and Cyperaceae (5). There was a change between 2005 and 2008 in the floristic composition, coverage, and frequency of community and populations. The detached family in coverage and frequency was Poaceae. Aristida pendula and Trachypogon plumosus changed more in coverage and relative frequency. All individuals with a trunk circunference (at the height of the 30 cm above the soil surface) CAS ≥ 9 cm was measured. We also measured the resprouts with CAS ≤ 9 cm. In 2008 were evaluated all the survivors individuals from 2005, the recruits and those that presented death by top kill. During the studied period there was a change on the community structure and the maintenance of the floristic composition of the woody component, except Protium unifoliolatum that disappeared during the studied period. We registred 40 species, 34 genera and 23 families. The density decreased during the studied period while the basal area increased. The relative frequency was the parameter that most influenced the IVI of the species, followed by relative density and relative dominance. The 10 most important species in 2005 continued the same in 2008, but in different positions. Curatella americana and Andira cuyabensis were the species with the higher IVI, specially because of the dominance in the area. The diametric and heights distribution differed between the two samples. In 2008 a new diametric class appeared (0 to 2.8 cm), because of the decrease of individuals that manifested smaller diameter resprouts after top kill. The annual rate of recruitment (1.16%.year-1) was smaller than the mortality rate (2.95%.year-1), confirming the decrease of the density. The total mortality was 9,3% and the rate of destroyed trunk was 33%. 70% of the dead individuals presented diameters between 4.2 to 7.3 cm and 52% with height between 2 to 3 meters. 35% of all individuals of the area suffered partial damage with resprouts. In 2008 were quantified 429 resprouts against 156 in 2005. 95% of the diameter of the resprouts were smaller than 2.22 cm. The influence of the burnings can influenced the changes of the vegetation of the studied CMs

Woody vegetation dynamics in a floodplain campo de murundus in central Brazil

Campos de murundus (grasslands dotted with knolls that are covered with savanna-like woody vegetation) are a common landscape in central Brazil. In this study, we assessed for the first time the dynamics of the vegetation in a floodplain campo de murundus, describing changes in composition and structure of the woody vegetation. In 2005, we established 16 permanent 25 × 25 m plots, where we identified and mapped individuals with a trunk diameter at the base ≥ 2.86 cm, as well as measuring the height of those individuals. In 2008 (after two fire events), we resampled the plots. In 2005, we had registered 4.54 m² ha-1 of basal area, 430 individuals, 42 species, 36 genera and 24 families. In 2008, we found an increase in basal area (to 4.65 m² ha-1) and a decrease in numbers of individuals (to 399), species (to 41), genera (to 35) and families (to 23). Species diversity did not differ between the two surveys. Mortality exceeded recruitment (2.68% year-1 vs. 1.29% year-1). Nevertheless, the community showed a gain in basal area owing to the growth of surviving individuals and, particularly, to the rise in the number of basal sprouts. We argue that the small floristic turnover may be related to the great resilience of the woody vegetation, whereas the structural changes might reflect the effects of the burnings in the area

Woody vegetation dynamics in a floodplain campo de murundus in central Brazil

Campos de murundus (grasslands dotted with knolls that are covered with savanna-like woody vegetation) are a common landscape in central Brazil. In this study, we assessed for the first time the dynamics of the vegetation in a floodplain campo de murundus, describing changes in composition and structure of the woody vegetation. In 2005, we established 16 permanent 25 × 25 m plots, where we identified and mapped individuals with a trunk diameter at the base ≥ 2.86 cm, as well as measuring the height of those individuals. In 2008 (after two fire events), we resampled the plots. In 2005, we had registered 4.54 m2 ha-1 of basal area, 430 individuals, 42 species, 36 genera and 24 families. In 2008, we found an increase in basal area (to 4.65 m2 ha-1) and a decrease in numbers of individuals (to 399), species (to 41), genera (to 35) and families (to 23). Species diversity did not differ between the two surveys. Mortality exceeded recruitment (2.68% year-1 vs. 1.29% year-1 ). Nevertheless, the community showed a gain in basal area owing to the growth of surviving individuals and, particularly, to the rise in the number of basal sprouts. We argue that the small floristic turnover may be related to the great resilience of the woody vegetation, whereas the structural changes might reflect the effects of the burnings in the area

Distinct leaf water potential regulation of tree species and vegetation types across the Cerrado–Amazonia transition

International audienceThe Cerrado–Amazonia transition harbors forest and savanna formations under the influence of pronounced climate seasonality; however, the water use strategies of this key region is not yet well understood. This study aimed at deciphering in intra- and interspecific variability in leaf water potential regulation among species across three distinct vegetation types (typical cerrado, cerradão, and semideciduous seasonal forest) of the Cerrado–Amazonia transition region. We expected a variation across iso/anisohydric strategies driven by plant–environment interactions and by species attributes (phenology and wood density). We selected 21 dominant species (seven per vegetation type), recorded their phenological strategy and wood density, and measured leaf water potential (Ψl) during the dry and rainy seasons to analyze variations associated with minimum Ψl, predawn Ψl (ΔΨpd), and midday Ψl (ΔΨmd) under the effect of variable vapor pressure deficit (VPD). The variation in Ψl across species was higher in the dry season than in the rainy season for all vegetation types. Most species from typical cerrado and cerradão showed similar behavior patterns, with higher Ψl regulation under high VPD and lower ΔΨpd. In contrast, most forest species showed lower regulation under high VPD, and higher ΔΨpd. Total or partial deciduousness together with strong stomatal regulation seems to be common water regulation strategies in the dry season for cerrado species but not for forest species. Our results suggest that, if drought events become more intense and frequent as predicted, seasonal forest species may be more vulnerable due to their lower Ψl regulation