214 research outputs found
Future Smartphone: MIMO Antenna System for 5G Mobile Terminals
No full textIn this article, an inverted L-shaped monopole eight elements Multiple Input Multiple Output (MIMO) antenna system is presented. The multi-antenna system is designed on a low cost 0.8 mm thick FR4 substrate having dimensions of 136 x 68 mm(2) resonating at 3.5GHz with a 6dB measured bandwidth of 450MHz, and with inter element isolation greater than 15 dB and gain of 4 dBi. The proposed design consists of eight inverted L-shaped elements and parasitic L-shaped strips extending from the ground plane. These shorted stripes acted as tuning stubs for the four inverted L-shaped monopole elements on the side of chassis. This is done to achieve the desired frequency range by increasing the electrical length of the antennas. A prototype is fabricated, and the experimental results show good impedance matching with reasonable measured isolation within the desired frequency range. The MIMO performances, such as envelope correlation coefficient (ECC) and mean effective gain (MEG) are also calculated along with the channel capacity of 38.1bps/Hz approximately 2.6 times that of 4 x 4 MIMO system. Due to its simple shape and slim design, it may be a potential chassis for future handsets. Therefore, user hand scenarios, i.e. both single and dual hand are studied. Also, the effects of hand scenarios on various MIMO parameters are discussed along with the SAR. The performance of the proposed system in different scenarios suggests that the proposed structure holds promising future within the next generation radio smart phones
Turkey Point Flux Station 1989 Forest (TP2)
No full textThe ON-TP89 site, also known as the CA-TP2 on Global Fluxnet and ON-WPP89 in some of the Fluxnet-Canada Research Network (FCRN)/Canadian Carbon Program (CCP) publications. ON-TP89 is a young planted white pine (Pinus strobusL.) forest of the Turkey Point Flux Station. It was planted in 1989 (ON-TP89) on a former agricultural land. Meteorological and flux data collection was started in summer 1989. The data documented here includes carbon, water and energy fluxes and meteorological and
soil measurements. A unique aspect of Turkey Point Flux Station is its geographic location between the boreal and the broadleaf deciduous forest transition zone. It provides an excellent opportunity to investigate and quantify the strength of the carbon sink or source for planted temperate conifer forests, and its sensitivity to seasonal and annual climate variability. Also white pine is an important species in the North American landscape, because of its ability to adapt to dry enviro
nments. It grows efficiently on nutrient poor, dry, sandy soils. Generally, it is the first woody species to flourish after a disturbance such as fire or clearing and over longer time periods helps more native forest species to establish through succession. White pine trees can live for about 350–400 years and their height may reach up to 45–60 m. These characteristics make white pine a preferred plantation (afforestation) species in eastern North America.
Fluxes, meteorological and soil measurement conducted at this site help us to explore carbon sequestration potential of chronosequence of planted or afforested white pine stands in southern Ontario. The main objectives are (i) to make year-round measurements of energy, water vapour and carbon dioxide (CO2) fluxes and other meteorological variables over mature, middle-aged, young and seedling white pine plantation forests (established in 1939, 1974, 1989 and 2002) (ii) to relate gross ph
otosynthesis and respiration of this stand to environmental factors (iii) determine the effects of seasonal and inter-annual climate variability on net ecosystem productivity, and to better understand the processes of
production, storage and transport of soil CO2 and (iv) use these data to further improve process-based photosynthesis and respiration models.
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The impact of induced drought on transpiration and growth in a temperate pine plantation forest
No full textThe effects of early growing season droughts on water and carbon balances in conifer forests are poorly understood. In this study, the response of canopy transpiration (Ec) and growth rates to reduced precipitation input during the early growing season was evaluated in a 70-year old temperate white pine (Pinus strobus L.) plantation forest, in Southern Ontario, Canada. In order to induce the drought, a 20 x 20?m throughfall exclusion setup was established. Throughfall was excluded from 1 April to 3 July 2009. During this period, 270?mm of rainfall occurred (27% of annual precipitation), of which more than 90% was excluded. Sapflow, stem growth, soil moisture and soil temperature were measured in both drought and reference plots. Prior to the induced drought, both plots showed similar soil water content, transpiration rates and tree diameters. The primary control on forest water loss was vapour pressure deficit, whereas soil moisture had an effect when it reached below 0.068?m3?m-3 during the growing season. The rainfall exclusion did not negatively affect Ec until early June, approximately 54?days after drought initiation. Ec was 27% less in the drought plot compared to the reference plot when evaluated at the end of the growing season in November. Tree growth estimates at the end of the growing season indicated a 17% decrease in growth in the drought plot as compared to the reference plot. Because climate predictions foresee changes in precipitation pattern, drought spells similar to this artificial short-term rainfall manipulation may be more frequent in the future. Hence, although overall precipitation may remain the same, the short-term deficit in water supply may have important implications for forest ecosystems. The findings of this rainfall manipulation will help quantify the impacts of spring and early summer water deficit on forest ecosystems and evaluate their potential responses to future climate regimes. Copyright (C) 2012 John Wiley & Sons, Ltd
Turkey Point Flux Station 2002 Forest (TP1)
No full textThe ON-TP02 site, also known as the CA-TP1 on Global Fluxnet and ON-WPP02 in some of the Fluxnet-Canada Research Network (FCRN)/Canadian Carbon Program (CCP) publications. ON-TP02 is a recently planted white pine (Pinus strobusL.) forest of the Turkey Point Flux Station. It was planted in 2002 (ON-TP02) on a former agricultural land. Meteorological and flux data collection was started in summer 2002. The data set documented here includes carbon, water and energy fluxes and meteorologi
cal and soil measurements. A unique aspect of Turkey Point Flux Station is its geographic location between the boreal and the broadleaf deciduous forest transition zone. It provides an excellent opportunity to investigate and quantify the strength of the carbon sink or source for planted temperate conifer forests, and its sensitivity to seasonal and annual climate variability. Also white pine is an important species in the North American landscape, because of its ability to adapt to dry
environments. It grows efficiently on nutrient poor, dry, sandy soils. Generally, it is the first woody species to flourish after a disturbance such as fire or clearing and over longer time periods helps more native forest species to establish through succession. White pine trees can live for about 350–400 years and their height may reach up to 45–60 m. These characteristics make white pine a preferred plantation (afforestation) species in eastern North America.
Fluxes, meteorological and soil measurement conducted at this site help us to explore carbon sequestration potential of chronosequence of planted or afforested white pine stands in southern Ontario. The main objectives are (i) to make year-round measurements of energy, water vapour and carbon dioxide (CO2) fluxes and other meteorological variables over mature, middle-aged, young and seedling white pine plantation forests (established in 1939, 1974, 1989 and 2002) (ii) to relate gross ph
otosynthesis and respiration of this stand to environmental factors (iii) determine the effects of seasonal and inter-annual climate variability on net ecosystem productivity, and to better understand the processes of production, storage and transport of soil CO2 and (iv) use these data to further improve process-based photosynthesis and respiration models.
More information about the site and associated data can be found in the metadata documentation.</p
Analysis of nitrogen controls on carbon and water exchanges in a conifer forest using CLASS-CTEMᴺ⁺ model
No full textNitrogen (N) controls on carbon and water exchanges were analyzed in a 70-year old eastern temperate conifer forest in Ontario, Canada from 2003 to 2007 using a newly developed nitrogen (N) cycle coupled model -- CLASS-CTEMᴺ⁺. This process-based model incorporates sunlit and shaded big-leaves for C3 and C4 photosynthesis and semi-mechanistic canopy conductance formulation for dynamic plant-functional-types. Recently, key soil and plant N cycling algorithms have also been included (e.g., biological fixation, atmospheric N deposition, fertilization, mineralization, nitrification, denitrification, leaching, soil nitrous dioxide (N₂0) emissions, root N uptake, plant N allocation and N controls on plant photosynthesis capacity). The simulated values of soil-plant N contents and processes rates including N₂0 fluxes were generally in agreement with observations. Comparison of default non-N and C&N-coupled model simulations clearly revealed N controls on photosynthetic uptake and water loss. Predictions of daily gross ecosystem productivity (GEP), ecosystem respiration (Re), net ecosystem productivity (NEP) and evapotranspiration (ET) showed better agreement with eddy covariance (EC) flux measurements when using the N-coupled model (RMSE of 1.97, 0.73, 1.44, 0.92; and MAE of 1.48, 0.55, 1.01, 0.60 for GEP, Re, NEP, and ET, respectively; n=1825) as compared to the non-N model simulations (RMSE of2.95, 1.35, 1.93, 1.03; MAE of2.38, 1.15, 1.55,0.71 for GEP, Re, NEP, and ET, respectively; n=1825) over 5 years (2003-2007). Annual values of N-coupled model simulated NEP were 134, 195, 183, 225 and 255 g C m⁻² yr⁻¹ for 2003-2007, as compared to non-N model simulated annual NEP values, which were 535, 562, 507, 540, and 535 g C m⁻² yr⁻¹ for respective years. These values were compared to measured NEP values of 220±67, 126±67, 33±67, 142±67 and 102±67 g C m⁻² yr⁻¹ for the years 2003-2007, respectively. The difference between N-coupled model simulated and EC measured annual variations of carbon exchanges was largely due to specific extreme weather events (e.g. drought, spring warming) during certain years. Overall, the impacts of N limitations on carbon fluxes were more pronounced during early spring, late autumn and winter seasons. This newly developed model will help to evaluate the response of terrestrial vegetation ecosystems to N variations under different scenarios for future climate change.Master of Science (MS
Carbon dynamics and greenhouse gas exchanges in an age-sequence of temperate pine forests
No full text Forest ecosystems play an important role in the global carbon (C) cycle by exchanging large amounts of carbon dioxide (CO₂) with the atmosphere. Their potential to act as significant sink for atmospheric CO₂ has been recognized and is relevant to current efforts in reducing atmospheric CO₂ concentrations. Besides the most important greenhouse gas CO₂, forests also emit and consume methane (CH₄) and nitrous oxide (N₂O) as the two other important atmospheric greenhouse gases (GHGs). To date, few attempts have been made to quantify the net effect of forest GHG exchange on the global warming potential. Furthermore, a better understanding of successional and environmental effects on forest processes is required to improve large scale estimates of forest C and GHG exchange. This thesis examines C dynamics and the exchange of the three major greenhouse gases (CO₂, CH₄, and N₂O) in an age-sequence (7-, 20-, 35-, and 70-years-old as of 2009) of afforested pine forests, in southern Ontario, Canada. The impacts of environmental controls on these GHG exchanges were also evaluated. Forest C exchange was determined for 2003 to 2008 using the eddy-covariance (EC) technique and inventory-based biometric measurements. Soil CH₄ and N₂O measurements were conducted from 2006 to 2007 using the static closed-chamber method. In addition, concentrations and fluxes of dissolved organic carbon (DOC) throughout the vertical profile in forest canopy and soil were determined from 2004 to 2005 using throughfall buckets and lysimeters. During periods without climatic constraints, monthly gross ecosystem productivity (GEP) and ecosystem respiration (RE) corrected for differences in site index increased with stand age, whereas monthly net ecosystem productivity (NEP) peaked at the 35-year-old site. In contrast, during constrained periods (e.g. seasonal drought events), monthly GEP and NEP at the 20-year-old site were higher compared to the 35-year-old site because trees may have benefited from sustained availability of soil water in deeper layers. This study further demonstrates that differences in site quality may affect the interpretation of age-related C flux dynamics in chronosequence and synthesis studies (Chapter 2). The temperature-RE relationship was an important control on daily NEP anomalies under optimum growing conditions, whereas constrains on GEP primarily determined NEP during environmentally constrained periods. Furthermore, effects from single environmental variable constrains on NEP anomalies were enhanced as well as outbalanced under multiple environmental variable constrains. The results further indicate that future changes in temperature and precipitation patterns towards drier and warmer conditions as well as greater cloud cover may result in reduced C sequestration potentials in these temperate pine forests (Chapter 3). Early summer drought and heat events in 2005 caused NEP to decrease by approximately 100 g C m⁻² y⁻¹ at each site compared to the other years. This decrease was primarily driven by a decrease in photosynthesis, while the effect of these events on ecosystem respiration was small. Overall, for the years 2003-2007, annual NEP was 219, 155, 36, 148, and 120 g C m⁻² y⁻¹ at the 68-year-old site, 666, 318, 346, 511 and 366 g C m⁻² y⁻¹ at the 33-year-old site, 768, 885, 684, 708 and 826 g C m⁻² y⁻¹ at the 18-year-old site, and-18, 145, 125, 34 and 164 g C m⁻² y⁻¹ at the 5-year-old seedling site, respectively (negative numbers indicating net C source (Chapter 4). Four-year mean values of biometric NEP_(B) and EC-based NEP_(EC) were similar at the 7-year-old seedling (77 and 66 g C m⁻² y⁻¹) and the 70-year-old mature site (135 and 124 g C m⁻² y⁻¹), but differed considerably at the 20-year-old (439 and 736 g C m⁻² y⁻¹) and the 35-year-old sites (170 and 392 g C m⁻² y⁻¹). Integrating NEP across the age-sequence resulted in a total net C sequestration of 137 and 229 t C ha⁻¹ over the initial 70 years as estimated by the biometric and EC method, respectively. The total ecosystem C pool at the 70-year-old site suggested an accumulation of 160 t C ha⁻¹. These three estimates resulted in a mean C sequestration of 175 ± 48 t C ha⁻¹ (Chapter 5). For both CH₄ and N₂O, we observed uptake and emission ranging from -160 to 245 μg CH₄ m⁻² hour⁻¹ and -52 to 21 μg N₂O m⁻² hour⁻¹, respectively (negative values indicate net uptake). Mean N₂O fluxes from mid-April to mid-December across the 7-, 20-, 35-, 70-years old stands were -3.7, 1.5, -2.2, and-7.6 μg N₂O m⁻² hour⁻¹, without age-related pattern, whereas the uptake rates of CH₄ increased with stand age from 6.4 to -7.9, -10.8, and-23.3 μg CH₄ m⁻² hour⁻¹, respectively. For the same period, the combined contribution of CH₄ and N₂O exchanges to the global warming potential (GWP) calculated from net ecosystem exchange of CO₂ and aggregated forest floor exchanges of CH₄ and N₂O was on average DOC concentration in forest floor leachates was positively correlated to stand age, aboveground biomass and forest floor carbon pools. From the period of Mid-April to December, DOC fluxes via precipitation, throughfall, and leaching through forest floor and Ah-horizon were in the range of ~1 to 2, 2 to 4, 0.5 to 3.5, and 0.1 to 2 g DOC m⁻², respectively. DOC export from the forest ecosystem during that period through infiltration and groundwater discharge decreased with increasing stand age from ~7 to 4, 3, and 2 g DOC m⁻² (Chapter 7). This thesis improved our understanding of C and GHG exchange dynamics and their environmental, physical, and physiological controls in forest ecosystems. This study will also contribute to efforts being made to better predict future forest C and GHG dynamics and their feedbacks on climate under changing environmental conditions. ThesisDoctor of Philosophy (PhD
Turkey Point Flux Station 1939 Forest (TP4)
No full textThe ON-TP39 site, also known as the CA-TP4 on Global Fluxnet and ON-WPP39 in some of the Fluxnet-Canada Research Network (FCRN)/Canadian Carbon Program (CCP) publications. ON-TP39 is the mature eastern white pine (Pinus strobusL.) forest of the Turkey Point Flux Station. It was planted in 1939 (ON-TP39) on cleared oak-savannah land. Meteorological data collection was started in late autumn 2001 and flux measurements were started in June 2002. The data set documented here includes carb
on, water and energy fluxes and meteorological and soil measurements.
A unique aspect of Turkey Point Flux Station is its geographic location between the boreal and the broadleaf deciduous forest transition zone. It provides an excellent opportunity to investigate and quantify the strength of the carbon sink or source for planted temperate conifer forests, and its sensitivity to seasonal and annual climate variability. Also white pine is an important species in the North American landscape, because of its ability to adapt to dry environments. It grows eff
iciently on nutrient poor, dry, sandy soils. Generally, it is the first woody species to flourish after a disturbance such as fire or clearing and over longer time periods helps more native forest species to establish through succession. White pine trees can live for about 350–400 years and their height may reach up to 45–60 m. These characteristics make white pine a preferred plantation (afforestation) species in eastern North America.
Fluxes, meteorological and soil measurement conducted at this site help us to explore carbon sequestration potential of chronosequence of planted or afforested white pine stands in southern Ontario. The main objectives are (i) to make year-round measurements of energy, water vapour and carbon dioxide (CO2) fluxes and other meteorological variables over mature, middle-aged, young and seedling white pine plantation forests (established in 1939, 1974, 1989 and 2002) (ii) to relate gross ph
otosynthesis and respiration of this stand to environmental factors (iii) determine the effects of seasonal and inter-annual climate variability on net ecosystem produc
tivity, and to better understand the processes of production, storage and transport of soil CO2 and (iv) use these data to further improve process-based photosynthesis and respiration models.
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Dendroanatomy under an Eddy covariance tower. New perspectives for a better understanding of the link between climate, C uptake and biomass growth
No full textSoil CO2 Efflux from Temperate and Boreal Forests in Ontario
No full textForests play an important role in the net ecosystem exchange of CO2 in terrestrial ecosystems. Soil respiration is often the major source of CO2 in forests and is greatly influenced by climatic variability and management practices. Spatial and temporal variations of soil respiration have been examined in a chronosequence (60, 30, 15, and 1 year-old) of temperate, afforested, white pine (Pinus strobus) forest stands in Southern Ontario, Canada, in order to investigate any age related differences. Spatial and temporal variations of soil respiration in a 74 year-old boreal, mixed-wood forest in Central Ontario, was also studied and compared with results from the 60 year-old, temperate, white pine, forest stand, in order to investigate any climate related differences. Soil CO2 flux, temperature, and moisture were measured for one year (June 2003 to May 2004, inclusive, for the chronosequence study, and August 2003 to July 2004, inclusive, for the boreal-temperate study). In all stands, temporal variability of soil respiration followed the seasonal pattern of soil temperature, reaching a minimum in winter and maximum in summer. Temporal variability of soil temperature was able to explain 80 to 96% of the temporal variability in soil respiration at all stands. Spatial variability in soil respiration was also observed at all stands and the degree of this variability was seasonal, following the seasonal trend of mean daily soil respiration. Spatial variability of some soil chemical properties was highly correlated with the spatial variability of soil respiration, while litter thickness was not. The location of soil respiration measurement with respect to tree trunks may also help to explain some of the spatial variability in soil respiration. Across the chronosequence, the highest mean daily CO2 efflux was observed during the growing season for the 15 year-old-stand (5.2 ± 1.3 to 0.4 ± 0.2 μmol CO2 m^-2 s^-1), which was comparable to the 60 year-old-stand (4.9 ± 1.3 to 0.2 ±0.1 μmol CO2 m^-2 s^-1), but higher than the 30 year (3.8 ± 0.9 to 0.2 ± 0.0 μmol CO2 m^-2 s^-1) and 1 year (2.9 ± 0.9 to 0.3 ± 0.3 μmol CO2 m^-2 s^-1) old stands. From boreal-temperate comparison, it was observed that mean daily soil respiration rates for the boreal stand (6.9 ± 1.7 to 0.5 ±0.1 μmol CO2 m^-2 s^-1) were higher during the growing season compared to the 60 year-old temperate forest stand. Understanding temporal and spatial variability of soil respiration and how it is controlled is essential to improving forest ecosystem carbon budget assessments, and subsequently, the global carbon budget. This study will contribute direct observations necessary for improving and validating forest ecosystem CO2 exchange models.ThesisMaster of Science (MSc
Revealing how intra- and inter-annual variability of carbon uptake (GPP) affects wood cell biomass in an eastern white pine forest
No full textForests are major terrestrial carbon (C) sinks and play a crucial role in climate change mitigation. Despite extensive studies on forest C sequestration, the relationship between seasonal C uptake and its allocation to woody biomass is poorly understood. Here we used a novel dendro-anatomical approach to investigate the relationships between climate variability, C uptake, and woody biomass growth in an 80 year-old eastern white pine ( Pinus strobus ) plantation forest in Ontario, Canada. We used eddy covariance (EC) gross primary productivity (GPP) from 2003–2018 and woody biomass estimated from chronologies of cell wall area (CWA, a proxy for C storage in individual wood cells) and ring wall area (RWA) for earlywood (EW) and latewood (LW) from 1970–2018. Warm temperatures in early spring and high precipitation in mid-spring and summer positively and strongly affected GPP, while high temperature and high vapor pressure deficit in the summer had a negative effect. From 2003 to 2018, there was a steady increase in both GPP and woody cell biomass. Moreover, we found strong positive correlations between GPP and CWA both in EW (May—July GPP, r = 0.65) and LW (July—August GPP, r = 0.89). Strong positive correlations were also found between GPP and RWA both in EW and LW (April—September, r = ⩾ 0.79). All these associations were stronger than the association between annual GPP and tree-ring width ( r = 0.61) used in previous studies. By increasing the resolution of tree-ring analysis to xylem-cell level, we captured intra-annual variability in biomass accumulation. We demonstrated a strong control of seasonal C assimilation (source) over C accumulation in woody biomass at this site. Coupling high-resolution EC fluxes (GPP) and wood anatomical measurements can help to reduce existing uncertainties on C source-sink relationships, opening new perspectives in the study of the C cycle in forests
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