276 research outputs found
Long-term eddy covariance fluxes and xylem anatomy for understanding carbon fixation in white pine woody biomass
No full textImproving our understanding of the carbon cycle is key to addressing the challenges of climate change. In this study, we investigated the relationships between intra and inter-annual climate variations, carbon fluxes, and the xylem biomass in an 80-year plantation of Pinus strobus at Turkey Point, Ontario, Canada. From eddy covariance tower, we obtained daily Gross Primary Production (GPP), precipitation and air temperature for the period 2003-2018. To determine inter-and intra-annual xylem biomass we selected 12 trees and built wood anatomical trait chronologies (cell lumen area, cell wall thickness, cell number, cell wall area and ring wall area) over the past 50 years. Using moving windows, we correlated all chronologies with daily climate data and GPP to analyse their associations at intra-annual scale.
The analysis showed that cell lumen area and cell wall thickness were strongly influenced by spring and summer temperature and precipitation. For the first time, we observed strong positive and significant correlations between GPP in the growing season and the cell wall area (which estimates the amount of carbon in each xylem cell) both in earlywood (May 10 - Aug 4, r = 0.685) and latewood (Jul 3 – Sep 3, r = 0.885). Strong positive correlations were also found between GPP and cell number and ring wall area. These results suggest a direct linkage between CO2 fluxes and the accumulation of carbon in woody biomass. This work will help to reconcile two important techniques that are widely used to study carbon sequestration in forests. It will help to reduce uncertainty in woody carbon accumulation and will open new perspectives in the study of the forest carbon cycle
Revealing intra-annual carbon sequestration patterns through xylem anatomy and eddy covariance fluxes in eastern white pine
No full textForests are major terrestrial carbon sinks, playing a crucial role in climate change mitigation. Nonetheless, the long-term seasonal carbon sequestration dynamics are scarcely understood. Here, we investigated the relationships between climate variability, carbon fluxes, and the xylem biomass in an 80-year-old plantation of Pinus strobus in Ontario, Canada. From Eddy Covariance tower, we obtained daily Gross Primary Production (GPP), precipitation, VPD and air temperature for the period 2003-2018. To estimate inter-and intra-annual xylem biomass accumulation we selected 12 trees and built wood anatomical chronologies of cell number (CN), cell wall area (CWA) and overall wall area per ring (RWA). We used moving windows correlations of daily climate data and GPP with anatomical chronologies to analyse their associations at intra-annual scale.
Temperature in early spring and precipitation in mid-spring and summer strongly positively affected GPP, while summer VPD had a negative effect. For the first time, we observed strong positive correlations between GPP in the growing season and CWA (proxy for carbon quantity in each xylem cell) both in earlywood (May 10 – Aug 1, r = 0.652) and latewood (Jul 3 – Sep 3, r = 0.885). Strong positive correlations were also found between GPP and CN and RWA (r ≥ 0.724). Our results suggest a direct influence of CO2 fluxes on the accumulation of carbon in woody biomass. This work will help to reduce uncertainties in woody carbon accumulation dynamics, opening new perspectives in the study of forest carbon cycle
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
Atmospheric and soil water limitations on water flux components in a temperate pine forest
No full text Sap flow measurements scaled to represent canopy transpiration (Ec) and eddy covariance measurements of total forest water vapour flux (E) were compared with soil water, meteorological measurements and modelled interception estimates to quantify the above canopy flux of water to the atmosphere from a temperate White pine ecosystem located on the Norfolk sand plain at Turkey Point, Ontario, for the growing season of 2006. Hydraulic redistribution (HR) was found to have occurred at the site on 26 days during the study (growing season of 2006). During a drought period in June, the nightly increases in stored water (up to 0.50 mm) provided by HR reduced drought intensity in the root zone by maintaining soil water contents ( 0) at levels above the water content associated with the approximate wilting point(() of 0.07). Daily forest water fluxes (E) averaged 2.4 mm d-1 and reached maximums of 4 mm d-1 regularly. Canopy transpiration (Ec) averaged 1.2 mm d-1• Modelled interception accounted for 18% of gross precipitation over the study period. Ec and interception loss (EI) contribute the majority (81%) of the water vapour exchanged between the forest and the atmosphere. E1 accounted for 34% of E and Ec accounted for 47%. Ec was controlled linearly by atmospheric demand (VPD) until a variable transition point was reached, after which mid-day Ec rates remained relatively constant. Ec rates were limited to approximately 0.10 mm hh-1 through the study period. This limitation was sensitive to early morning VPD and soil water deficit. Increases in early morning VPD caused maximum Ec rates to arrive earlier in the day and to be reduced in magnitude. This shift in the timing and magnitude of Ec rates masked a relationship between Ec and soil water content that caused Ec to be strictly limited once root zone soil water content (Bo-25cm) reduced to ~0.07. This study illustrates that the water storage capacities of different site characteristics (particularly the canopy and soil) are an important factor to consider when investigating how changing precipitation characteristics might affect the hydrology of an ecosystem, and discusses the interrelationship between transpiration, soil water supply and atmospheric demand. ThesisMaster of Science (MSc
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.
</p
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
Biomass and Carbon Allocation in Chronosequence of White Pine (Pinus strobus L.) plantations in Southern Ontario, Canada
No full text This study assessed biomass and carbon (C) allocation in a chronosequence of four White pine (Pinus strobus L.) plantation forests planted in 2002 (WPP02), 1989
(WPP89), 1974 (WPP74), and in 1939 (WPP39), in southern Ontario, Canada. A plotbased inventory and destructive tree sampling were conducted in 2004 to assess
allocation of oiomass and C in ecosystem components, as well as allometry of tree
biomass. Seasonal and annual patterns of litter and branch fall were also determined. Individual tree biomass components as well as sapwood area have strong site specific allometric relationships with tree diameter. Except for foliage biomass, strong single allometric equations could also be obtained across all sites and stand ages. Whereas allometry of individual tree components may be affected by site conditions and stand age, total tree biomass solely depended on tree diameter. This suggests that total biomass of White pine may be predicted from single allometric equations with DBH as input variable across sites and even across regions. Relative partitioning of tree biomass components was strongly related to tree age. Stem biomass gains major importance with increasing tree age at the cost of all other components comprising 69% of total tree biomass after 65 years. Whereas site conditions influenced the absolute amount of biomass and allometry of individual tree components, they did not affect their relative partitioning Only biomass of trees, woody debris, and small roots (2-5mm) showed agerelated patterns by increasing with greater stand age. Increase in tree biomass was
highest during the early decades after establishment and after thinning practices. C storage in forest floor was 0.8, 7.5, 5.4, and 12.1 t C ha⁻¹ and C content in mineral soil was 37.2, 33.9, 39.1, and 36.7 t C ha⁻¹ at WPP02, WPP89, WPP74, and WPP39, respectively. Biomass of roots Thus, estimations of C storage in forest ecosystems should include all above and belowground C pools, and its accuracy may be improved by predicting total treebiomass with allometric equations related to stand age and tree diameter.ThesisMaster of Science (MSc
Biophysical and Economic Analysis of Black Spruce Regeneration in Eastern Canada using Global Climate Model Productivity Outputs
No full textThis study explores the biophysical potential and economic attractiveness of black spruce (Picea mariana) regeneration in eastern Canada under future climate changes. It integrates process-based ecosystem model simulated forest productivities from three major global climate models (GCMs), growth and yield formulations specific to black spruce and economic analyses to determine the overall investment value of black spruce, both including and excluding carbon sequestration benefits. Net present value (NPV) was estimated to represent the financial attractiveness of long-rotation forest plantations through time. It was assumed that stands would not be harvested at volumes less than 80 m3 ha-1. The price of stumpage was set to 500 ha-1, and the discount rate was considered at 4%, with sensitivity analyses conducted around these assumptions. The growth and yield of black spruce was simulated for an extreme future climate scenario – IPCC-RCP 8.5. The results suggested a general North-South gradient in forest productivity where gross merchantable wood volumes increased with decreasing latitudes. This pattern was also observed in NPVs, with higher values projected for the southern portion of the study area. Based on the base economic assumptions and sensitivity analyses, study results suggested that black spruce plantations are not economically attractive, unless carbon sequestration benefits of at least $5 ton-1 CO2 are realized. Further sensitivity analyses showed that discount rate plays a significant role in determining the optimal harvest age and value. Furthermore, the optimal harvest rotation age increases with increasing carbon price by approximately 9 to 18 years.ThesisMaster of Science (MSc
- …
