Optical and radar remote sensing of land use and land cover change in the tropics: An assessment of deforestation and secondary vegetation

Quantification of the direct impact of land use in the tropics on net biotic carbon flux requires estimates of rates of deforestation, pre- and post-disturbance biomass, and fate of the cleared land. Synoptic observations of the extent, persistence, rates of secondary succession, and structure or biomass of regrowing forests would also help constrain estimates of net carbon flux due to tropical land use. While remote sensing applications can provide estimates of the rates of deforestation and the fate of the cleared land (pasture, croplands, or secondary vegetation), techniques for estimating persistence, rates of succession, and biomass of secondary vegetation are needed. We documented the spatial and inter-annual variability in the rates of forest clearing, formation rates and persistence of secondary vegetation for 3 sites in Amazonia and 4 sites in Southeast Asia using Landsat TM data from mid-1980s to late-1990s. Secondary vegetation was a large, rapidly changing pool. Variability in the observed annual rates of deforestation and secondary vegetation formation was high. The transition probabilities of both the formation and clearing of secondary vegetation decreased with age. Persistence of the secondary vegetation pool was also highly variable, likely indicating two distinct land use trajectories: rotational agriculture/pasture maintenance versus abandonment. We also evaluated the spatial, temporal, and noise constraints of JERS SAR data for mapping and monitoring biomass of secondary vegetation in Rondonia, Brazil. Results indicate that quantitative estimates of biomass using single date JERS-1 imagery is problematic because of temporal variability in backscatter due to intrinsic texture, system noise, and environmental effects. However, JERS-1 data are still useful for distinguishing of secondary vegetation stands at different stages of development. Multi-temporal analysis significantly improves biomass estimates to the point where it is possible to map changes in biomass. Slight reductions in the variability in estimates of normalized radar cross-section greatly improve biomass estimation. Merging JERS-1 SAR data with Landsat TM derived age estimates improved characterization of clearings and secondary vegetation in Rondonia by providing information on the relative differences in secondary vegetation development and residual slash with age

Tying knots in light fields

We construct a new family of null solutions to Maxwell's equations in free space whose field lines encode all torus knots and links. The evolution of these null fields, analogous to a compressible flow along the Poynting vector that is both geodesic and shear-free, preserves the topology of the knots and links. Our approach combines the Bateman and spinor formalisms for the construction of null fields with complex polynomials on $\mathbb{S}^3$. We examine and illustrate the geometry and evolution of the solutions, making manifest the structure of nested knotted tori filled by the field lines.Comment: 5 pages, 3 figure

Assessing Short‐Term Impacts of Management Practices on N2O Emissions From Diverse Mediterranean Agricultural Ecosystems Using a Biogeochemical Model

Croplands are important sources of nitrous oxide (N2O) emissions. The lack of both long‐term field measurements and reliable methods for extrapolating these measurements has resulted in a large uncertainty in quantifying and mitigating N2O emissions from croplands. This is especially relevant in regions where cropping systems and farming management practices (FMPs) are diverse. In this study, a process‐based biogeochemical model, DeNitrification‐DeComposition (DNDC), was tested against N2O measurements from five cropping systems (alfalfa, wheat, lettuce, vineyards, and almond orchards) representing diverse environmental conditions and FMPs. The model tests indicated that DNDC was capable of predicting seasonal and annual total N2O emissions from these cropping systems, and the model\u27s performance was better than the Intergovernmental Panel on Climate Change emission factor approach. DNDC also captured the impacts on N2O emissions of nitrogen fertilization for wheat and lettuce, of stand age for alfalfa, as well as the spatial variability of N2O fluxes in vineyards and orchards. DNDC overestimated N2O fluxes following some heavy rainfall events. To reduce the biases of simulating N2O fluxes following heavy rainfall, studies should focus on clarifying mechanisms controlling impacts of environmental factors on denitrification. DNDC was then applied to assess the impacts on N2O emissions of FMPs, including tillage, fertilization, irrigation, and management of cover crops. The practices that can mitigate N2O emissions include reduced or no tillage, reduced N application rates, low‐volume irrigation, and cultivation of nonleguminous cover crops. This study demonstrates the necessity and potential of utilizing process‐based models to quantify N2O emissions from regions with highly diverse cropping systems

Modeling impacts of farming management alternatives on CO2, CH4, and N2O emissions: A case study for water management of rice agriculture of China

Since the early 1980s, water management of rice paddies in China has changed substantially, with midseason drainage gradually replacing continuous flooding. This has provided an opportunity to estimate how a management alternative impacts greenhouse gas emissions at a large regional scale. We integrated a process-based model, DNDC, with a GIS database of paddy area, soil properties, and management factors. We simulated soil carbon sequestration (or net CO2 emission) and CH4 and N2O emissions from China\u27s rice paddies (30 million ha), based on 1990 climate and management conditions, with two water management scenarios: continuous flooding and midseason drainage. The results indicated that this change in water management has reduced aggregate CH4 emissions about 40%, or 5 Tg CH4 yr−1, roughly 5–10% of total global methane emissions from rice paddies. The mitigating effect of midseason drainage on CH4 flux was highly uneven across the country; the highest flux reductions (\u3e200 kg CH4-C ha−1 yr−1) were in Hainan, Sichuan, Hubei, and Guangdong provinces, with warmer weather and multiple-cropping rice systems. The smallest flux reductions (\u3c25 kg CH4-C ha−1 yr−1) occurred in Tianjin, Hebei, Ningxia, Liaoning, and Gansu Provinces, with relatively cool weather and single cropping systems. Shifting water management from continuous flooding to midseason drainage increased N2O emissions from Chinese rice paddies by 0.15 Tg N yr−1 (∼50% increase). This offset a large fraction of the greenhouse gas radiative forcing benefit gained by the decrease in CH4 emissions. Midseason drainage-induced N2O fluxes were high (\u3e8.0 kg N/ha) in Jilin, Liaoning, Heilongjiang, and Xinjiang provinces, where the paddy soils contained relatively high organic matter. Shifting water management from continuous flooding to midseason drainage reduced total net CO2emissions by 0.65 Tg CO2-C yr−1, which made a relatively small contribution to the net climate impact due to the low radiative potential of CO2. The change in water management had very different effects on net greenhouse gas mitigation when implemented across climatic zones, soil types, or cropping systems. Maximum CH4 reductions and minimum N2O increases were obtained when the mid-season draining was applied to rice paddies with warm weather, high soil clay content, and low soil organic matter content, for example, Sichuan, Hubei, Hunan, Guangdong, Guangxi, Anhui, and Jiangsu provinces, which have 60% of China\u27s rice paddies and produce 65% of China\u27s rice harvest

Reduced methane emissions from large-scale changes in water management of China’s rice paddies during 1980-2000

Decreased methane emissions from paddy rice may have contributed to the decline in the rate of increase of global atmospheric methane (CH4) concentration over the last 20 years. In China, midseason paddy drainage, which reduces growing season CH4 fluxes, was first implemented in the early 1980s, and has gradually replaced continuous flooding in much of the paddy area. We constructed a regional prediction for China\u27s rice paddy methane emissions using the DNDC biogeochemical model. Results of continuous flooding and midseason drainage simulations for all paddy fields in China were combined with regional scenarios for the timing of the transition from continuous flooding to predominantly mid-season drainage to generate estimates of total methane flux for 1980–2000. CH4 emissions from China\u27s paddy fields were reduced over that period by ∼5 Tg CH4 yr−1

El Programa de Producción y su Relación en la Gestión de Inventarios de Corporación ADC Sede Tacna, Periodo 2014-2016

La presente investigación, se encuentra relacionado a la gestión de inventarios con un adecuado programa de producción en Corporación ADC en la ciudad de Tacna, periodo 2014-2016. La presente investigación es no experimental porque se obtienen datos directamente de la realidad objeto de estudio, asimismo es descriptivo correlacionada de acuerdo con la finalidad de la investigación. El área de investigación se encuentra enmarcada en la contabilidad financiera, debido a que es una rama de la contabilidad la cual se encarga de recolectar, clasificar, registrar, resumir e informar sobre las operaciones de los centro de producción y como esta se relaciona con la gestión de inventarios, así como en los informes económicos financieros de Corporación ADC. Parte del problema que afronta la Corporación ADC, es que no cuenta con una sólida gestión de inventarios, debido a que su programa de producción no es adecuada, cada planta de producción proyecta según la capacidad máxima de la fábrica, mas no miden el nivel de ventas ni la proyección de las mismas, causando en cierta manera altos niveles de stock en los almacenes; lo que podría originar posibles contingencias financieras y gastos por abastecimiento. Para la realización de este trabajo de investigación los datos se recolectaron a través de la guía de análisis documental, que conforman los Estados Financieros, Reportes de Producción, y Análisis de cuentas de los años 2014 al 2016, obteniéndose una perspectiva clara de la situación del nivel de Producción y su relación con la Gestión de Inventarios de corporación ADC, pudiéndose detectar algunas deficiencias de las áreas relacionadas y proponer algunas soluciones.Tesi

Caracterización de marcadores moleculares de genes involucrados en la estructura y desarrollo de la fibra de alpaca y su potencial asociación con el diámetro de la fibra

Identifica y valida polimorfismos de nucleótidos únicos (SNP) en tres genes, dos de los cuales codifican para proteínas funcionales (EDAR y HOXC13) y uno para proteína estructural (KRT31) en fibra y, evalúa su posible asociación con el diámetro de fibra de alpaca. Un total de 96 alpacas reproductoras no emparentadas fueron elegidas a partir de la evaluación fenotípica mediante los principales indicadores raciales y textiles de un total de 800 alpacas. El análisis de diversidad genética basada en genotipificación de 10 microsatelites (YWLL08, YWLL29, YWLL36, YWLL40, YWLL44, LCA05, LCA08, LCA19, LCA37, LCA66) reporta un total de 128 alelos con niveles de variabilidad genética elevada y baja consanguinidad (HE>0.68, FIS0.3), los genes EDAR y KRT31 mostraron niveles de consanguinidad baja (FIS<0.02) en contraste con el gen HOXC13 (FIS = 0.108). Un análisis de asociación genética entre marcadores SNP de los genes EDAR, HOXC13, KRT31 y diámetro de fibra mediante regresión múltiple bajo modelo aditivo indican que no se detectó asociación con dicho carácter.Tesi