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

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

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

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

Rarity of monodominance in hyperdiverse Amazonian forests.

Tropical forests are known for their high diversity. Yet, forest patches do occur in the tropics where a single tree species is dominant. Such "monodominant" forests are known from all of the main tropical regions. For Amazonia, we sampled the occurrence of monodominance in a massive, basin-wide database of forest-inventory plots from the Amazon Tree Diversity Network (ATDN). Utilizing a simple defining metric of at least half of the trees ≥ 10 cm diameter belonging to one species, we found only a few occurrences of monodominance in Amazonia, and the phenomenon was not significantly linked to previously hypothesized life history traits such wood density, seed mass, ectomycorrhizal associations, or Rhizobium nodulation. In our analysis, coppicing (the formation of sprouts at the base of the tree or on roots) was the only trait significantly linked to monodominance. While at specific locales coppicing or ectomycorrhizal associations may confer a considerable advantage to a tree species and lead to its monodominance, very few species have these traits. Mining of the ATDN dataset suggests that monodominance is quite rare in Amazonia, and may be linked primarily to edaphic factors

Evolutionary Heritage Influences Amazon Tree Ecology

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

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

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

Estimating the global conservation status of more than 15,000 Amazonian tree species

Estimates of extinction risk for Amazonian plant and animal species are rare and not often incorporated into land-use policy and conservation planning. We overlay spatial distribution models with historical and projected deforestation to show that at least 36% and up to 57% of all Amazonian tree species are likely to qualify as globally threatened under International Union for Conservation of Nature (IUCN) Red List criteria. If confirmed, these results would increase the number of threatened plant species on Earth by 22%. We show that the trends observed in Amazonia apply to trees throughout the tropics, and we predict thatmost of the world’s >40,000 tropical tree species now qualify as globally threatened. A gap analysis suggests that existing Amazonian protected areas and indigenous territories will protect viable populations of most threatened species if these areas suffer no further degradation, highlighting the key roles that protected areas, indigenous peoples, and improved governance can play in preventing large-scale extinctions in the tropics in this century