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A new species of Miconia belonging to a clade diagnosed by strongly four-lobed ovaries/hypanthia and elongated calyx teeth flattened parallel to the floral radii, i.e., the Calycogonium hispidulum complex, endemic to the Sierra Ma...
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A new species of Miconia belonging to a clade diagnosed by strongly four-lobed ovaries/hypanthia and elongated calyx teeth flattened parallel to the floral radii, i.e., the Calycogonium hispidulum complex, endemic to the Sierra Maestra of eastern Cuba, is described, illustrated, and compared with related Cuban species. The discovery of Miconia becqueri brings to 15 the number of recognized species of this complex, seven of which occur in Cuba (if Clidemia barbeyana is conspecific with C. wrightii).
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Background: Young saplings of Hopea odorata, a native dipterocarp in Vietnam, require shading to prevent photoinhibition but they must avoid competition that stagnates their growth.
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Understanding the consequences of changes in climatic and biological drivers on tree carbon and water fluxes is essential in forestry. Using a metamodeling approach, sensitivity and uncertainty analyses were carried out for a tree...
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Understanding the consequences of changes in climatic and biological drivers on tree carbon and water fluxes is essential in forestry. Using a metamodeling approach, sensitivity and uncertainty analyses were carried out for a tree-scale model (MAESPA) to isolate the effects of climate, morphological and physiological traits, and intertree competition on the absorption of photosynthetically active radiation (APAR), gross primary production (GPP), transpiration (TR), light use efficiency (LUE), and water use efficiency (WUE) in clonal Eucalyptus plantations. The metamodel predicting daily TR was validated using one year of sap flow measurements and showed close agreement with the measurements (mean percentage error = 11%, n = 2155). Simulations showed that APAR, GPP, and TR were very sensitive to the tree morphology and to a competition index representing its local environment. LUE and WUE were, in addition, very sensitive to the natural variability of the physiological leaf and root parameters. A maximum percentage error of 10% in these parameters leads to 18%, 17%, 16%, 9%, and 18% uncertainty for APAR, GPP, TR, LUE, and WUE, respectively. The uncertainties in TR were highest for the smallest trees. This study highlighted the need to take account of the spatial and temporal variability of tree traits and environmental conditions for simulations at the tree scale.
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In agroforestry systems (AFS), quantifying the competition for light is a prerequisite toward understanding the impact of shade trees on the productivity of the under-crop. Models for homogeneous canopies and shade/full-sun approa...
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In agroforestry systems (AFS), quantifying the competition for light is a prerequisite toward understanding the impact of shade trees on the productivity of the under-crop. Models for homogeneous canopies and shade/full-sun approaches do not address the intra-plot heterogeneity, typical of AFS. For the first time, MAESTRA, a 3D light absorption model, was fully parameterized in a heterogeneous 2-canopy layers AFS. We quantified competition for photosynthetic photon flux density (Q) between shade trees (Erythrina poepiggiana) and coffee (Coffea arabica), with a spatial resolution from the plant to the plot (2.7 ha) and a temporal resolution from half-hour to one full year. The predicted transmittance through the 2-canopy layers was verified against field measurements. The goodness of fit (R2 >0.75, RRMSE <26%) was comparable to the predictions from 10 other studies using 3D light models and mostly verified in one-layered systems (mean R2=0.89 and mean RRMSE=17%). Maps of absorbed Q showed that despite their low density in the plot (5.2 trees ha-1), the tall Erythrina trees reduced Q available for the coffee layer by 14% annually. Annual pruning of the oldest unproductive coffee resprouts maintained a large horizontal heterogeneity in coffee LAI, with direct impact on the Q absorption map. This management practice had a strong impact on seasonal variations of absorbed Q by the coffee canopy. We proposed also a simple approach to estimate Q absorbed yearly by the coffee plants in AFS of variable tree density, requiring only few measurements in the field. An extrapolation indicated that the amount of Q absorbed by the coffee canopy would display a negative exponential relationship (k=-0.34) when increasing shade tree density (from nil to 29 trees ha-1). The estimated k was similar to the shade tree extinction coefficient of diffuse radiation measured with a plant canopy analyzer. We showed that the presence of shade trees tends to reverse the diurnal time course of the fraction of Qa when compared to a plantation in the open. Overall, MAESTRA proved to successfully unlock the question of intra-plot heterogeneity for light absorption and to provide defensible light budgets as a continuous and mapped covariable, a crucial step for many field experimentations.
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Light-related interactions can increase productivity in tree-species mixtures compared with monocultures due to higher stand-level absorption of photosynthetically active radiation (APAR) or light-use efficiency (LUE). However, th...
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Light-related interactions can increase productivity in tree-species mixtures compared with monocultures due to higher stand-level absorption of photosynthetically active radiation (APAR) or light-use efficiency (LUE). However, the effects of different light-related interactions, and their relative importance, have rarely been quantified. Here, measurements of vertical leaf-area distributions, tree sizes, and stand density were combined with a tree-level light model (Maestra) to examine how crown architecture and vertical or horizontal canopy structure influence the APAR of 16 monocultures and eight different two-species mixtures with 16 different species in a Chinese subtropical tree diversity experiment. A higher proportion of crown leaf area occurred in the upper crowns of species with higher specific leaf areas. Tree-level APAR depended largely on tree leaf area and also, but to a lesser extent, on relative height (i.e., tree dominance) and leaf-area index (LAI). Stand-level APAR depended on LAI and canopy volume, but not on the vertical stratification or canopy leaf-area density. The mixing effects, in terms of relative differences between mixtures and monocultures, on stand-level APAR were correlated with the mixing effects on basal area growth, indicating that light-related interactions may have been responsible for part of the mixing effects on basal area growth. While species identity influences the vertical distributions of leaf area within tree crowns, this can have a relatively small effect on tree and stand APAR compared with the size and vertical positioning of the crowns, or the LAI and canopy volume.
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Predictive modeling and sensing based approaches to scheduling irrigation are increasingly being adopted by commercial nurseries due to their potential to automate irrigation and improve crop production. This study had two overarc...
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Predictive modeling and sensing based approaches to scheduling irrigation are increasingly being adopted by commercial nurseries due to their potential to automate irrigation and improve crop production. This study had two overarching objectives: first, to compare the irrigation scheduling performance of a substrate moisture sensing approach to that of a three-dimensional predictive transpiration modeling approach in five tree species grown in a containerized pot-in-pot production system. For comparison we measured tree growth (crown leaf area and stem caliper), volume of water applied and irrigation application efficiency (A(e)) for each method. The predictive method (i.e., a linked photosynthesis-stomatal conductance (A(n)-g(s)) scheme) applied 18-56% more water than the sensing-based method in four species and 6% less in the fifth. Mean A(e) was 80.1 and 89.5% for predictive and sensing-based treatments, respectively. Across species, predictive scheduling yielded 19-53% greater leaf area and 3.4-11% more caliper growth than sensing-based scheduling. Our second objective was to determine if the accuracy of the A(n)-g(s) scheme could be retained while using generalized multi-species means for key physiological input parameters instead of species-specific values. We found the accuracy of transpiration estimates to largely depend upon two parameters-g(0): the minimum g(s), and g(1): the marginal water cost per unit of carbon gain. When just these two parameters were characterized on a species-specific basis, transpiration estimates were within 10% error >65% of the time and within 20% error >95% of the time. We conclude that the predictive transpiration modeling approach to scheduling irrigation was a superior method for producing greater tree growth but at the cost of greater water use and slightly lower Ae. Furthermore, species-specific parameterization of g(0) and g(1) in the A(n)-g(s) scheme are critical to accurate species-specific transpiration estimates, whereas most other physiology parameters may be generalized circumventing the need for comprehensive An-gs parameterization. (C) 2015 Elsevier B.V. All rights reserved.
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Models seldom consider the effect of leaf-level biochemical acclimation to temperature when scaling forest water use. Therefore, the dependence of transpiration on temperature acclimation was investigated at the within-crown scale...
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Models seldom consider the effect of leaf-level biochemical acclimation to temperature when scaling forest water use. Therefore, the dependence of transpiration on temperature acclimation was investigated at the within-crown scale in climatically contrasting genotypes of Acer rubrum L., cv. October Glory (OG) and Summer Red (SR). The effects of temperature acclimation on intracanopy gradients in transpiration over a range of realistic forest growth temperatures were also assessed by simulation. Physiological parameters were applied, with or without adjustment for temperature acclimation, to account for transpiration responses to growth temperature. Both types of parameterization were scaled up to stand transpiration (expressed per unit leaf area) with an individual tree model (MAESTRA) to assess how transpiration might be affected by spatial and temporal distributions of foliage properties. The MAESTRA model performed well, but its reproducibility was dependent on physiological parameters acclimated to daytime temperature. Concordance correlation coefficients between measured and predicted transpiration were higher (0.95 and 0.98 versus 0.87 and 0.96) when model parameters reflected acclimated growth temperature. In response to temperature increases, the southern genotype (SR) transpiration responded more than the northern (OG). Conditions of elevated long-term temperature acclimation further separate their transpiration differences. Results demonstrate the importance of accounting for leaf-level physiological adjustments that are sensitive to microclimate changes and the use of provenance-, ecotype-, and/or genotype-specific parameter sets, two components likely to improve the accuracy of site-level and ecosystem-level estimates of transpiration flux.
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Aboveground tree growth is influenced by light availability, light capture, and the efficiency captured light is converted into growth. All three factors are influenced by neighborhood species composition and stand structure and c...
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Aboveground tree growth is influenced by light availability, light capture, and the efficiency captured light is converted into growth. All three factors are influenced by neighborhood species composition and stand structure and can be modified with silvicultural treatments. The objective was to examine the absorption of photosynthetically active radiation (APAR), light-use efficiency (LUE), and aboveground biomass growth of juvenile white spruce (Picea glauca (Moench) Voss) trees in plantations and planted in naturally regenerated stands with diverse species composition. Trees were sampled across a range of sizes, and measurements of white spruce and neighborhood trees were collected at ages seven and eight. Light absorption of individual trees was modeled with MAESTRA accounting for species-specific crown structures of neighboring trees. APAR increased linearly with leaf area in both treatments. The correlation was more influenced by neighborhood competition than self-shading, since self-shading was minimized by crown spread and height growth. Biomass growth increased with increasing APAR in both treatments, but growth for a given unit of APAR was greater in the natural stands, possibly due to greater below ground biomass allocation in plantations due to lower stand densities. LUE declined slightly across the range of tree size, which contrasts most other studies. The decline could be due to juvenile age of the trees and inherent slow growth of spruce species. (C) 2016 Elsevier B.V. All rights reserved.
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The El Cobre deposit, east of Cuba, lies in the intermediate volcanosedimentary sequence of the Sierra Maestra intraoceanic island arc. The structure of the deposit corresponds to that of a volcanogenic-hosted massive sulfide (VHM...
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The El Cobre deposit, east of Cuba, lies in the intermediate volcanosedimentary sequence of the Sierra Maestra intraoceanic island arc. The structure of the deposit corresponds to that of a volcanogenic-hosted massive sulfide (VHMS) model. It comprise (a) thick stratiform bodies (baryte and anhydride), (b) three stratabound bodies (formed by silicification and sulfidation of limestones or sulfate stata), (c) stockwork zones, an older anhydrite stockwork and a younger quartz-pyrite stockwork grading downwards to (d) simple veins (quartz with sulfide ores). Pyrite, chalcopyrite and sphalerite are the most abundant sulfides. Fluid inclusions from this deposit have a salinity between 2.3 and 5.7 wt.% NaCl eq., homogenization temperatures range between 177 and 300 deg C. Sulfur exhibits a range of delta~34S values from - 1.4 per thousand to + 7.3 per thousand for sulfides and from + 16 per thousand to + 21 per thousand for sulfates. Fluid inclusions and sulfur isotope data at El Cobre deposit indicate that the hydrothermal fluid from which the sulfide precipitated was seawater, modified by reaction with volcanic host rocks during hyrothermal circulation.
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There is great interest in how species interactions change along spatial gradients in resource availability and climatic conditions. Many studies have shown that facilitation or complementary effects increase as growing conditions...
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There is great interest in how species interactions change along spatial gradients in resource availability and climatic conditions. Many studies have shown that facilitation or complementary effects increase as growing conditions become harsher, however, several studies in forests have recently shown the opposite trend. Increasing complementary effects with improving growing conditions may result when species interactions influence light absorption or use. This hypothesis was tested in mixed-species forests of Abies alba Mill. and Picea abies (L.) Karst. in south-western Germany where complementary effects on growth increased as climatic conditions improved. The absorption of photosynthetically active radiation (APAR) by individual trees was predicted using a detailed light model. Light-use efficiency (LUE) of individual trees was estimated as basal area growth per unit APAR. APAR and LUE were modelled as functions of crown size, climatic variables and the species composition and density of the neighbourhood of individual trees. For a given tree size, APAR (for both species) and LUE (of A. alba trees) were greater for trees in mixed-species neighbourhoods than monospecific neighbourhoods and this complementary effect increased as climatic conditions improved and on sites with faster growing trees. Increases in APAR for A. alba probably resulted because shading from P. abies trees was less intense than that from other A. alba trees on the more productive site. The species composition of individual tree neighbourhoods did not influence relationships between stem diameter and crown diameter or height to the crown base, for either species. However, the height of each species, for a given stem diameter, increased as the proportion of a given tree's neighbourhood basal area that was composed of the same species increased. This change in crown architecture could also have contributed to the complementarity effects in these stands. Increasing complementary effects with improving growing conditions is consistent with the stress-gradient hypothesis if competition for light is considered to be the stressor. This study shows that such a spatial pattern in species interactions could be associated with increasing differences in APAR or LUE between mixtures and monocultures as climatic conditions become more favourable.
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