139 research outputs found

    Fuentes y dosis de fertilización potásica en el crecimiento, tuberización y calidad de fritura de la papa (Solanum tuberosum L.) variedad Única

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    Universidad Nacional Agraria La Molina. Facultad de Agronomía. Departamento Académico de FitotecniaEn el Perú, se ha incrementado el consumo de papa en hojuelas (papas chips) y a la francesa (papa frita). Esto ha producido una demanda de variedades con aptitud para fritura. Sin embargo, la oferta es insuficiente debido a la mayor concentración de azucares reductores que se encuentran en las papas producidas en la sierra a pesar de contar con variedades con buena aptitud para la fritura. Se considera que la fertilización potásica es una práctica agronómica importante para la producción y calidad de fritura de los tubérculos de papa. Sin embargo, no se dispone de suficiente información sobre el efecto de diferentes fuentes y dosis de fertilización potásica. El presente trabajo de investigación se realizó durante la campaña agrícola 2014-2015 en el Instituto Regional de Desarrollo (IRD) de Sierra se evaluaron los efectos de dos factores principales: Tres fuentes potásicas (cloruro de potasio, sulfato de potasio y sulpomag) y dos dosis (100 y 200 kg ha-1 de K2O) de fertilización potásica sobre el crecimiento, componentes del rendimiento, calidad de fritura y extracción de potasio utilizando como material vegetal papa (Solanum tuberosum L.) var. ÚNICA. Además, se empleó dos tratamientos adicionales (80-200-200 y 160 – 200 – 0 kg ha-1 de N - P2O5 - K2O). El diseño experimental fue Bloque Completamente al Azar con arreglo factorial de 3 x 2 con cuatro repeticiones. Las características evaluadas fueron la emergencia, altura de plantas, cobertura foliar, número de tallos, número de estolones, número tubérculos, peso fresco y seco de hojas y tubérculos por tallo; con los tubérculos cosechados se evaluó el rendimiento total y comercial, número y tamaño de tubérculos; en post cosecha se determinó el porcentaje de materia seca, calidad de fritura y la extracción de potasio. Los resultados obtenidos de acuerdo a las condiciones en las cuales se llevó a cabo la presente investigación muestran que el mayor ritmo de crecimiento de las plantas (0.97 cm día-1) se presentó a los 55 y 70 días; el máximo porte promedio de plantas (54.6 cm) se evidenció a los 127 días; el mayor incremento diario del porcentaje de cobertura foliar de planta (1.64 % día-1) también se presentó entre los 55 y 70 días alcanzándose el mayor porcentaje promedio a los 127 días con 87.6 %; el promedio de tallos principales (4.09) por planta se definió a los 55 días; el promedio máximo de estolones (8.02) por tallo alcanzó a los 70 días; el promedio de tubérculos por tallo en la cosecha (170 días) fue 3.02; la tuberización alcanzó la mayor ganancia de peso diario entre los 89 y 127 días con 4.86 g tallo-1 día-1 llegando al máximo peso promedio a los 170 días con 305.3 g tallo-1. El rendimiento total alcanzó en promedio 44.95 t ha-1 (1.21 kg planta-1) y el rendimiento comercial fue en promedio 39.7 t ha-1. En cuanto a características evaluadas en post cosecha, el porcentaje promedio de materia seca fue 22.53 %, la calidad de fritura en tiras presentó apariencia general buena y, la extracción promedio de potasio total de plantas a los 150 días por efecto de los factores en estudio fue 224.73 kg ha-1 de K2O; es decir 37.43 y 187.29 kg ha-1 de K2O en el follaje y tubérculos, respectivamente. De acuerdo a los resultados, es posible concluir que tanto los factores en estudio como la reducción de la dosis nitrogenada y la ausencia del potasio no mostraron efectos estadísticamente significativos en ninguna de las características del crecimiento y desarrollo de plantas, ni en los componentes del rendimiento de tubérculos ni en la calidad de fritura. Las plantas fertilizadas con sulfato de potasio extrajeron mayor cantidad de K2O respecto a las otras fuentes potásicas. Se encontró relación directa entre la dosis de fertilización potásica y la extracción total de K2O tanto en el follaje como en los tubérculos. Sin embargo, estas diferencias no se tradujeron en el rendimiento total, comercial ni en el contenido de materia seca de los tubérculos. Estos resultados sugieren que la cantidad de potasio contenido en el suelo (408 mg kg-1) habría sido suficiente para que no se manifiesten diferencias por efecto de los factores en estudio

    Increasing biomass in Amazonian forest plots

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    A previous study by Phillips et al. of changes in the biomass of permanent sample plots in Amazonian forests was used to infer the presence of a regional carbon sink. However, these results generated a vigorous debate about sampling and methodological issues. Therefore we present a new analysis of biomass change in old-growth Amazonian forest plots using updated inventory data. We find that across 59 sites, the above-ground dry biomass in trees that are more than 10 cm in diameter (AGB) has increased since plot establishment by 1.22 ± 0.43 Mg per hectare per year (ha-1 yr-1), where 1 ha = 104 m2), or 0.98 ± 0.38 Mg ha-1 yr-1 if individual plot values are weighted by the number of hectare years of monitoring. This significant increase is neither confounded by spatial or temporal variation in wood specific gravity, nor dependent on the allometric equation used to estimate AGB. The conclusion is also robust to uncertainty about diameter measurements for problematic trees: for 34 plots in western Amazon forests a significant increase in AGB is found even with a conservative assumption of zero growth for all trees where diameter measurements were made using optical methods and/or growth rates needed to be estimated following fieldwork. Overall, our results suggest a slightly greater rate of net stand-level change than was reported by Phillips et al. Considering the spatial and temporal scale of sampling and associated studies showing increases in forest growth and stem turnover, the results presented here suggest that the total biomass of these plots has on average increased and that there has been a regional-scale carbon sink in old-growth Amazonian forests during the previous two decades

    Increasing dominance of large lianas in Amazonian forests

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    Ecological orthodoxy suggests that old-growth forests should be close to dynamic equilibrium, but this view has been challenged by recent findings that neotropical forests are accumulating carbon and biomass, possibly in response to the increasing atmospheric concentrations of carbon dioxide. However, it is unclear whether the recent increase in tree biomass has been accompanied by a shift in community composition. Such changes could reduce or enhance the carbon storage potential of old-growth forests in the long term. Here we show that non-fragmented Amazon forests are experiencing a concerted increase in the density, basal area and mean size of woody climbing plants (lianas). Over the last two decades of the twentieth century the dominance of large lianas relative to trees has increased by 1.7–4.6% a year. Lianas enhance tree mortality and suppress tree growth, so their rapid increase implies that the tropical terrestrial carbon sink may shut down sooner than current models suggest. Predictions of future tropical carbon fluxes will need to account for the changing composition and dynamics of supposedly undisturbed forests

    Los habitantes arbóreos de Choquequirao: exploraciones que nos hablan

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    Las regiones montañosas como los Andes son un refugio para los árboles, en un mundo que se calienta. Choquequirao es un refugio para alrededor de 500 especies de árboles, incluidos los helechos arborescentes y las palmeras. Esta estimación la hacemos en base a miles de colecciones de árboles que se han realizado mediante esforzadas exploraciones botánicas particularmente en los últimos 40 años en las provincias de Anta y La Convención, que corresponde actualmente a las áreas núcleo del Área de Conservación Regional Choquequirao. A pesar de que tanto el área de estudio como el Santuario Histórico de Machupicchu presentan los mismos tipos de bosque, el potencial de diversidad arbórea de Choquequirao es mayor debido a: su extensión (más de 100 mil hectáreas) y a su mayor gradiente altitudinal básicamente en la parte baja, por lo se incluye en la contabilidad mayor número de especies de los bosques pre-montanos. Si bien el número de especies de árboles estimadas puede aumentar con mayores investigaciones, la presencia de 486 especies de árboles es representativo para los bosques pre-montanos y montanos particularmente entre los 1200 a 4200 m de altitud. La gradiente altitudinal viene a ser uno de los factores determinantes para el incremento de la diversidad de los árboles en esta región. Además, se debe considerar que aún hay cerca de 4000 especies de árboles aún no descritos por la ciencia, en América del Sur; muchas de estas, sin duda, están presentes en los diversos bosques del Área de Conservación Regional Choquequirao. Aún queda más para descubrir, enfatizando la importancia de mantener un mayor ritmo de investigación botánica

    Unraveling Amazon tree community assembly using Maximum Information Entropy: a quantitative analysis of tropical forest ecology

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    In a time of rapid global change, the question of what determines patterns in species abundance distribution remains a priority for understanding the complex dynamics of ecosystems. The constrained maximization of information entropy provides a framework for the understanding of such complex systems dynamics by a quantitative analysis of important constraints via predictions using least biased probability distributions. We apply it to over two thousand hectares of Amazonian tree inventories across seven forest types and thirteen functional traits, representing major global axes of plant strategies. Results show that constraints formed by regional relative abundances of genera explain eight times more of local relative abundances than constraints based on directional selection for specific functional traits, although the latter does show clear signals of environmental dependency. These results provide a quantitative insight by inference from large-scale data using cross-disciplinary methods, furthering our understanding of ecological dynamics

    Evolutionary Heritage Influences Amazon Tree Ecology

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    Lineages tend to retain ecological characteristics of their ancestors through time. However, for some traits, selection during evolutionary history may have also played a role in determining trait values. To address the relative importance of these processes requires large-scale quantification of traits and evolutionary relationships among species. The Amazonian tree flora comprises a high diversity of angiosperm lineages and species with widely differing life-history characteristics, providing an excellent system to investigate the combined influences of evolutionary heritage and selection in determining trait variation. We used trait data related to the major axes of life-history variation among tropical trees (e.g. growth and mortality rates) from 577 inventory plots in closed-canopy forest, mapped onto a phylogenetic hypothesis spanning more than 300 genera including all major angiosperm clades to test for evolutionary constraints on traits. We found significant phylogenetic signal (PS) for all traits, consistent with evolutionarily related genera having more similar characteristics than expected by chance. Although there is also evidence for repeated evolution of pioneer and shade tolerant life-history strategies within independent lineages, the existence of significant PS allows clearer predictions of the links between evolutionary diversity, ecosystem function and the response of tropical forests to global change

    Geographic patterns of tree dispersal modes in Amazonia and their ecological correlates

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    Unidad de excelencia María de Maeztu CEX2019-000940-MAim: To investigate the geographic patterns and ecological correlates in the geographic distribution of the most common tree dispersal modes in Amazonia (endozoochory, synzoochory, anemochory and hydrochory). We examined if the proportional abundance of these dispersal modes could be explained by the availability of dispersal agents (disperser-availability hypothesis) and/or the availability of resources for constructing zoochorous fruits (resource-availability hypothesis). Time period: Tree-inventory plots established between 1934 and 2019. Major taxa studied: Trees with a diameter at breast height (DBH) ≥ 9.55 cm. Location: Amazonia, here defined as the lowland rain forests of the Amazon River basin and the Guiana Shield. Methods: We assigned dispersal modes to a total of 5433 species and morphospecies within 1877 tree-inventory plots across terra-firme, seasonally flooded, and permanently flooded forests. We investigated geographic patterns in the proportional abundance of dispersal modes. We performed an abundance-weighted mean pairwise distance (MPD) test and fit generalized linear models (GLMs) to explain the geographic distribution of dispersal modes. Results: Anemochory was significantly, positively associated with mean annual wind speed, and hydrochory was significantly higher in flooded forests. Dispersal modes did not consistently show significant associations with the availability of resources for constructing zoochorous fruits. A lower dissimilarity in dispersal modes, resulting from a higher dominance of endozoochory, occurred in terra-firme forests (excluding podzols) compared to flooded forests. Main conclusions: The disperser-availability hypothesis was well supported for abiotic dispersal modes (anemochory and hydrochory). The availability of resources for constructing zoochorous fruits seems an unlikely explanation for the distribution of dispersal modes in Amazonia. The association between frugivores and the proportional abundance of zoochory requires further research, as tree recruitment not only depends on dispersal vectors but also on conditions that favour or limit seedling recruitment across forest types

    Local hydrological conditions influence tree diversity and composition across the Amazon basin

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    Tree diversity and composition in Amazonia are known to be strongly determined by the water supplied by precipitation. Nevertheless, within the same climatic regime, water availability is modulated by local topography and soil characteristics (hereafter referred to as local hydrological conditions), varying from saturated and poorly drained to well-drained and potentially dry areas. While these conditions may be expected to influence species distribution, the impacts of local hydrological conditions on tree diversity and composition remain poorly understood at the whole Amazon basin scale. Using a dataset of 443 1-ha non-flooded forest plots distributed across the basin, we investigate how local hydrological conditions influence 1) tree alpha diversity, 2) the community-weighted wood density mean (CWM-wd) – a proxy for hydraulic resistance and 3) tree species composition. We find that the effect of local hydrological conditions on tree diversity depends on climate, being more evident in wetter forests, where diversity increases towards locations with well-drained soils. CWM-wd increased towards better drained soils in Southern and Western Amazonia. Tree species composition changed along local soil hydrological gradients in Central-Eastern, Western and Southern Amazonia, and those changes were correlated with changes in the mean wood density of plots. Our results suggest that local hydrological gradients filter species, influencing the diversity and composition of Amazonian forests. Overall, this study shows that the effect of local hydrological conditions is pervasive, extending over wide Amazonian regions, and reinforces the importance of accounting for local topography and hydrology to better understand the likely response and resilience of forests to increased frequency of extreme climate events and rising temperatures
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