Significance of xylem water conductance for the compatibility of maté phenotypes (Ilex paraguarensis) for grafting

In this study the compatibility for grafting of root stocks and buds of three recognized leaf phenotypes of Ilex paraguarensis St. (mate) Hil. from south Brazil was investigated. Special regard was given to the anatomical structure and the sap flow in the secondary xylem of the grafted plants. Significant differences of the wood structure expressed in terms of vessel portion, vessel member length, and intervessel perforations were found in low compatible phenotypes, while highly compatible phenotypes had a very similar wood structure. In grafts of highly compatible phenotypes six months after grafting the water conducting system of root stocks and buds was strongly linked to each other, while in grafts of low compatible phenotypes the formation of connecting vessel elements was rare. In the first month after grafting the xylem sap flow in the buds of all grafts was significantly higher compared to their root stocks, while in the second month in grafts of highly compatible phenotypes, the water transport in the root stocks and in the buds was balanced. In contrast, in grafts of low compatible phenotypes even in the second month the water transport in the root stocks was lower compared to the buds causing the dieback of a high portion of these plants.

GAS EXCHANGE OF OIL PALMS TRESS SUBMITTED TO LEAFTEMPERATURE MODIFIED GROWN IN DIFFERENT PLANTATION SYSTEMS

Studies on the influence of leaf temperature rise on gas exchange in tropical tree species grown in plantations are rare. With regard to the predicted increase in air temperature in the future in the Central Amazon, we investigated the influence of increasing leave temperature on the gas exchange of oil palms cultivated in monocultures as well as in mixed plantations with cassava or banana. This study was carried out at the Embrapa Experimental Station in Presidente Figueiredo – AM – Brazil, 60 km north of Manaus. The net photosynthesis (Pn), transpiration (E), stomatal conductance (gs) and the water use efficiency (WUE) of the plants were quantified by a portable photosynthesis meter (CI-340). In all plantations increasing leaf temperatures caused a significant decrease of the net photosynthesis (Pn), stomatal conductance (gs), and the water use efficiency (WUE) of the oil palms. Maximum transpiration rates (E) were observed at leaf temperatures between 38 and 46°C. In addition to the influence of leaf temperature rise, the planting system also had a significant influence on the gas exchange of palm plants

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

Climate seasonality limits leaf carbon assimilation and wood productivity in tropical forests

The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is  < 2000 mm yr⁻¹ (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall  < 2000 mm yr⁻¹

Impact of Site Conditions Changes on the Tree Ring Records Suitability as Climate Proxies in the Brazilian Amazon

ABSTRACT The increment zones width in the xylem of Swietenia macrophylla King was investigated by dendrochronological methods in an undisturbed and a strongly disturbed tropical site near Aripuanã, Mato Grosso, Brazil (10°09&#8217; S, 59°26&#8217;W). The study aimed to assess the impact of forest disturbance on the relationship between precipitation and the cambial growth of this species. Tree-ring width chronologies were developed for both sites from cross-dated increment curves. Simple correlations were computed between monthly precipitation records and the annual increment of Swietenia for the period between 1870 and 2000. Logging activities and altered land use caused a significant decrease of the water supply of the Swietenia trees grown in the disturbed area compared to trees grown in the undisturbed area. Consequently, the precipitation of almost the total growing season had a significant influence on the tree ring width of Swietenia grown in the disturbed area, while in the undisturbed forest area the significant correlation between monthly precipitation and the tree ring width of Swietenia was restricted to the beginning of the growing season (November to January). However, the reconstruction of monthly precipitation data from the tree ring width records was more precise using the chronology developed from tree ring width records of undisturbed trees compared to the chronology developed from tree ring widths from the disturbed area. It was concluded that the use of the tree ring widths of Swietenia as climate proxies is restricted to certain months of the year and requires tree ring width chronologies developed from trees grown in undisturbed or only slightly disturbed forest areas without severe anthropogenic changes in microclimate

Chemical composition and natural durability of juvenile and mature heartwood of Robinia pseudoacacia L.

The aim of this study was to characterize the properties of juvenile and mature heartwood of Robinia pseudoacacia L. (black locust). The content, the composition, and subcellular localization of heartwood extractives were studied in 14 old-grown trees from forest sites in Germany and Hungary, as well as in 16 younger trees of four clone types. Heartwood extractives (methanol and acetone extraction) were analysed by HPLC-chromatography. UV microspectrophotometry was used to localize the extractives in the wood cell walls. The natural durability of juvenile and mature heartwood was analysed according to the European standard EN 350-1. Growth analyses, as well as the chemical analyses, showed that in Robinia the formation of juvenile wood is restricted to the first 10-15 years of cambial growth. In the heartwood high contents of phenolic compounds and flavonoids were present, which were in high concentrations in the cell walls of the axial parenchyma and of the vessels. In the juvenile heartwood, the content of these extractives is significantly lower than in the mature heartwood. In agree, the juvenile heartwood had a lower resistance to decay by Coniophora puteana (brown rot fungus) and Coriolus versicolor (white rot fungus) compared to the mature.<br>O objetivo deste estudo foi caracterizar as propriedades da região de cerne dos lenhos juvenis e adultos de Robinia pseudoacacia L. O conteúdo, a composição, bem como a localização subcelular dos extrativos foram estudados em 14 árvores de florestas de produção na Alemanha e na Hungria, assim como em 16 árvores de quatro tipos clone. Os extrativos (metanol e acetona extração) foram analisados por cromatografia-HPLC. O microespectrofotômetro de ultra violeta foi utilizado para localizar os extrativos nas paredes celulares da madeira. A durabilidade natural do lenho juvenil e adulto foi analisada de acordo com a norma europeia EN 350-1. Análises do incremento, bem como as análises químicas mostraram que, em Robinia a formação de lenho juvenil é limitada aos primeiros 10/15 anos de crescimento cambial. No cerne, elevados teores de compostos fenólicos e flavonóides foram encontrados e localizados em concentrações elevadas nas paredes celulares do parênquima axial e dos vasos. No cerno do lenho juvenil o conteúdo destes extrativos é significativamente menor do que no cerne do lenho adulto. o cerne do lenho juvenil apresentou menor resistência à degradação por Coniophora puteana (fungo de podridão parda) e Coriolus versicolor (fungo de podridão branca) em comparação com a madeira de lenho adulto

Impact of Site Conditions Changes on the Tree Ring Records Suitability as Climate Proxies in the Brazilian Amazon

ABSTRACT The increment zones width in the xylem of Swietenia macrophylla King was investigated by dendrochronological methods in an undisturbed and a strongly disturbed tropical site near Aripuanã, Mato Grosso, Brazil (10°09’ S, 59°26’W). The study aimed to assess the impact of forest disturbance on the relationship between precipitation and the cambial growth of this species. Tree-ring width chronologies were developed for both sites from cross-dated increment curves. Simple correlations were computed between monthly precipitation records and the annual increment of Swietenia for the period between 1870 and 2000. Logging activities and altered land use caused a significant decrease of the water supply of the Swietenia trees grown in the disturbed area compared to trees grown in the undisturbed area. Consequently, the precipitation of almost the total growing season had a significant influence on the tree ring width of Swietenia grown in the disturbed area, while in the undisturbed forest area the significant correlation between monthly precipitation and the tree ring width of Swietenia was restricted to the beginning of the growing season (November to January). However, the reconstruction of monthly precipitation data from the tree ring width records was more precise using the chronology developed from tree ring width records of undisturbed trees compared to the chronology developed from tree ring widths from the disturbed area. It was concluded that the use of the tree ring widths of Swietenia as climate proxies is restricted to certain months of the year and requires tree ring width chronologies developed from trees grown in undisturbed or only slightly disturbed forest areas without severe anthropogenic changes in microclimate