Thomas G. Pypker

• BSc., MSc., PhD
• Professor at Thompson Rivers University

In forest ecosystems, measurement of bark water storage capacity (BWSC) is required for determining the amount of rainfall interception and understanding throughfall and stemflow processes. We compared the bark roughness coefficient (BRC) and BWSC of even-aged, widely-planted, broad-leaved and needle-leaved species in the Chitgar Forest Park, near...

Abstract In this study, monthly meteorological parameters of temperature, precipitation, and wind speed recorded at 104 synoptic weather stations scattered across Iran were analyzed to construct annual time series of the meteorological data for a 30-year period (1988–2017) using the Mann–Kendall test and the Sen’s slope estimator. Based on the de M...

In this study, monthly meteorological parameters of temperature, precipitation, and wind speed recorded at 104 synoptic weather stations scattered across Iran were analyzed to construct annual time series of the meteorological data for a 30-year period (1988-2017) using the Mann-Kendall test and the Sen’s slope estimator. Based on the de Martonne a...

Northern peatlands are globally important long-term sinks of carbon due to their predominantly saturated conditions. However, these ecosystems are expected to become drier with climate change, potentially leading to shrubification. As such, the response of the shrubification–evapotranspiration (ET) feedback may be of critical importance to future p...

Continuous water level monitoring using absolute pressure transducers with onboard datalogging is common practice in hydrologic studies. While there has been some discussion and study of temperature-derived error (TDE), there has not been a systematic evaluation of the problem. We sought to answer three questions: 1) are current best practices enou...

Deposition of atmospheric pollution as particulate matter (PM) has become a serious issue in many urban areas. This study measured and estimated the amount of atmospheric PM deposition onto oriental plane (Platanus orientalis L.) trees located in Tehran Megapolis, Iran. PM deposited on the leaves of urban trees during spring and summer was estimate...

Background As sap flow research expands, new challenges such as fast sap flows or flows co-occurring with freeze/thaw cycles appear, which are not easily addressed with existing methods. In order to address these new challenges, sap flow methods capable of measuring bidirectional, high and slow sap flux densities ( F d , cm ³ cm ⁻² h ⁻¹ ), thermal...

Aim We explore long-term plant community responses 17 years after a one-time application of biosolids (0, 50, 100, 150, 200, 250 dry Mg∙ha⁻¹) to determine (1) whether the land application of biosolids on mine tailings, seeded with agronomic grass-legume mixture, affects long-term plant community responses, (2) how application rates and soil texture...

Mine tailings are nutrient deficient, contain no organic matter, and have high metal concentrations preventing the long term establishment of vegetation. The use of organic amendments, including biosolids, can help the revegetation of mine tailings by adding organic matter and nutrients but can increase metals in the receiving soil. There is also u...

Oil palm plantations are rapidly expanding in the Brazilian eastern Amazon. Further expansion of irrigated oil palm plantations may occur because they may improve productivity during drought events compared to rainfed-only plantations. To investigate the importance of irrigation to alleviate drought-induced stress on palm trees, and its potential a...

We assessed how climate change may impact the canopy hydrology of individual Pinus eldarica, Pinus brutia, and Cupressus arizonica trees planted in arid and semi-arid climates in Iran. Precipitation that reaches the forest floor as throughfall (TF) represents a significant portion of individual precipitation events (Pg ). We used a nondimensional r...

We studied the recovery of tree- and stand-level carbon (C) storage in a lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) forest in northern British Columbia that experienced substantial (∼83%) mortality in 2006–2007 (total loss by 2013 = 86%) during a severe mountain pine beetle (MPB; Dendroctonus ponderosae Hopkins, 1902) in...

The importance of forest canopy settings for the elemental chemistry of epiphytic lichens in undisturbed forests is poorly understood despite its impact on epiphytes, understory vegetation and microbial soil communities. Here, we examine the elemental composition in standardized thalli of the cephalolichen Lobaria pulmonaria transplanted to the low...

We investigated the effect of foliar application of potassium nitrate (KNO3) and zinc sulfate (ZnSO4) on the fruit quality of pomegranate (Punica granatum L. cv. Malas-E–Torsh in Saveh). Potassium was applied as KNO3 at concentrations of 0%, 0.25%, and 0.5% and zinc was applied as ZnSO4 at concentrations of 0%, 0.5%, and 1% in a completely randomiz...

Stemflow (SF) has been recognized as an important process which can exert considerable effects on the hydrology, biogeochemistry, and ecology of wooded ecosystems. The aim of this study was to quantify the relationship between SF (yields and funneling ratios, FR) of beech (F. orientalis) trees and rainfall characteristics, to evaluate the effects o...

Unpiloted aerial vehicles (UAVs) are transforming the field of ecohydrology as remote sensing platforms. UAV flight characteristics bring them closer to the land surface, further increasing the achievable spatial resolution of multi-/hyperspectral, thermal infrared (TIR) and light distancing and ranging (LiDAR) measurements and enabling measurement...

The spatial and temporal heterogeneity of throughfall (TF) have important ecological impacts in forest ecosystems. The aim of this study was to quantify spatio-temporal variability of TF and to evaluate the effects of canopy traits and gross rainfall (GR) characteristics on TF at the event scale. Event-based measurements were carried out from Septe...

Across all forest systems, the primary driver of throughfall (TF) amount is rainfall amount (Pg) though no work has addressed the sensitivity of the TF response to projected shifts in Pg due to climate change. We assessed how climate change may impact TF sensitivity to variability in Pg for eleven typical forest sites across the main climate types...

Understanding short- and long-term responses of forest nutrient cycling to disturbance is vital to predicting future forest function. Mortality of ash trees (Fraxinus spp.) due to emerald ash borer [EAB, Agrilus planipennis (Coleoptera: Buprestidae)] invasion is likely to alter ecosystem processes within infested stands throughout North America. In...

Abstract The Hyrcanian forests are typical deciduous broadleaf forests characterized by an important role in providing moisture to vegetation by fog precipitation (FP). The importance of FP on vegetated surfaces as a source of moisture has been acknowledged for a long time. The aim of this study was to quantify FP and water interception in a natura...

Natural wetlands constitute the largest and most uncertain source of methane (CH4) to the atmosphere and a large fraction of them are found in the northern latitudes. These emissions are typically estimated using process (“bottom-up”) or inversion (“top-down”) models. However, estimates from these two types of models are not independent of each oth...

Aim of study: To measure the nutrient leaching from canopy and the O layer in a natural oriental beech (Fagus orientalis Lipsky) forest and a Norway spruce (Picea abies) plantation. Materials and methods: From mid-July to early November, 2013, we measured throughfall (TF) (n=45), stemflow (SF) (n=12) and leaching from the O layer (n = 30) in a 0.5...

Abstract The spatial heterogeneity of throughfall (TF) is a critical component of the hydrological cycle. The aim of this study was to identify throughfall (TF) spatial pattern variability for leaf-out seasons in natural beech (Fagus orientalis L.) stand located in the Caspian forests using the geostatistical method. The rain-collectors used for me...

Biocontrol resistance in St. John's Wort

Natural wetlands constitute the largest and most uncertain source of methane (CH4) to the atmosphere and a large fraction of them are in the northern latitudes. These emissions are typically estimated using process (bottom-up) or inversion (top-down) models, yet the two are not independent of each other since the top-down estimates rely on the a pr...

The invasive emerald ash borer (EAB, Agrilus planipennis Fairmaire) causes widespread ash tree mortality in North America, and the CO2 efflux (respiration, F) from coarse dead wood (CDW) following the EAB infestation is unknown. We examined seasonal variations in CO2 fluxes from various types of CDW (cut ash stumps, downed logs, and standing girdle...

We assessed the effects of heater wattage on sap flux estimates from heat dissipation sensors and generated calibrated equations for 1-year-old Eucalyptus grandis Hill ex Maiden trees. We used a total of eight trees ranging from 3 to 6 cm in diameter. Our calibration experiment was performed with a modified tree-cut approach, which allowed us to es...

We assessed the effects of heater wattage on sap flux estimates from heat dissipation sensors and generated calibrated equations for one-year-old Eucalyptus grandis trees. We used a total of eight trees ranging from 3-6 cm in diameter. Our calibration experiment was performed with a modified tree-cut approach, which allowed us to estimate gravimetr...

In this study we assessed the effects of heater wattage on sap flux estimates from heat dissipation sensors. We used a total of eight trees ranging from 3-6 cm in diameter. Our calibration experiment was performed with a modified tree-cut approach, which allowed us to estimate gravimetric water use manually by weighing 20-L buckets every 15 min, wh...

Tree transpiration is important in the recycling of precipitation in the Amazon and might be negatively affected by El Niño–Southern Oscillation (ENSO)–induced droughts. To investigate the relative importance of soil moisture deficits versus increasing atmospheric demand (VPD) and determine if these drivers exert different controls over tree transp...

The rapid and extensive expansion of emerald ash borer (EAB) in North America since 2002 may eliminate most existing ash stands, likely affecting critical ecosystem services associated with water and carbon cycling. To our knowledge, no studies have evaluated the coupled response of black ash (Fraxinus nigra Marsh.) wetland water tables, soil tempe...

Atmospheric pollution is an important concern in urban environments. The impact of urban pollution on the physiological, biochemical and anatomical properties of leaves of oriental plane (Platanus orientalis L.) was studied. The leaves were collected from an urban site (Tehran, Iran) and a non-urban forest park (Chitgar Forest Park). Anatomical (st...

The emerald ash borer (EAB) is rapidly spreading throughout eastern North America and devastating ecosystems where ash is a component tree. This rapid and sustained loss of ash trees has already resulted in ecological impacts on both terrestrial and aquatic ecosystems and is projected to be even more severe as EAB invades black ash-dominated wetlan...

Emerald ash borer (EAB) continues to spread across North America, infesting native ash trees and changing the forested landscape. Black ash wetland forests are severely affected by EAB. As black ash wetland forests provide integral ecosystem services, alternative approaches to maintain forest cover on the landscape are needed. We implemented simula...

Black ash (Fraxinus nigra Marsh.) exhibits canopy dominance in regularly inundated wetlands, suggesting advantageous adaptation. Black ash mortality due to emerald ash borer (Agrilus planipennis Fairmaire) will alter canopy composition and site hydrology. Retention of these forested wetlands requires understanding black ash's ecohydrologic role. Ou...

The temporal dynamics of forest canopy rainfall partitioning are important to forest ecology and management as it influences all subsequent hydrological processes along the rainfall-to-discharge flow path. Despite a growing body of literature on the importance of coupled hydrological–ecological interactions during periodic forest life cycle events,...

The Persian oak, Quercus brantii, trees in the Zagros region of Western Iran have been in decline since 2000. The decline is assumed to be highly connected with changes in meteorological parameters. Our objectives were to quantify the long-term trends in meteorological parameters and reference evapotranspiration (ET0) in the Zagros region and estim...

The Persian oak, Quercus brantii, trees in the Zagros region of Western Iran have been in decline since 2000. The decline is assumed to be highly connected with changes in meteorological parameters. Our objectives were to quantify the long-term trends in meteorological parameters and reference evapotranspiration (ET0) in the Zagros region and estim...

Globally, peatlands store a large quantity of soil carbon that can be subsequently modified by hydrologic alterations from land-use change and climate change. However, there are many uncertainties in predicting how carbon cycling and greenhouse gas emissions are altered by long-term changes in hydrology. Therefore, the goal of this study was to qua...

Many mechanisms aid invasive plants' competitive interactions. Yet, the extent to which invasive plants alter canopy hydrometeorological mechanisms determining the quantity and distribution of rainwater resources to soils have never been assessed. We examine these mechanisms for a global invader, Ailanthus altissima, across an invasion chronosequen...

The women in Lupeta, Tanzania use fuelwood as the primary source of fuel. The choices and constraints women face in fuelwood collection was examined using walks with women and semi-structured interviews. Women primarily use fuelwood with limited charcoal use. They would prefer to use more charcoal but costs, limited income, competition and ownershi...

Forested wetlands dominated by black ash (Fraxinus nigra) are currently threatened by the rapid expansion of the exotic emerald ash borer (EAB) (Agrilus planipennis, Coleoptera: Buprestidae) in North America, and very little is known about the hydrology and ecology of black ash wetlands. The ecohydrological response of forested wetlands following a...

Graphic novella by artist Bagus Seta (Tyasseta) based on the scientific story told in Sadeghi et al. (2017), Agricultural and Forest Meteorology, 240, 10.

The invasive emerald ash borer (EAB) (Agrilus planipennis Fairmaire (Coleoptera: Buprestidae)) is a significant threat to biodiversity and ecosystem processes in North American forests. Of particular concern is the fate of Fraxinus nigra (black ash), which is frequently a dominant canopy species across much of its range. To investigate the potentia...

Our goal was to determine how epiphytic lichens and bryophytes affect canopy latent heat fluxes in an old-growth Douglas-fir forest when the canopy was dry. The epiphyte water content (WCe expressed as a percent of dry weight) of representative epiphytic foliose lichens, fruticose lichens and bryophytes was measured in the laboratory after 1 to12 h...

An experiment was initiated to study the effects of rubber benthic barriers vs. aggressive cutting on the invasive aquatic emergent plant, yellow flag iris. Treatments were compared against a control at two locations within British Columbia, Canada (Vaseux Lake and Dutch Lake). Yellow flag iris response was significantly different between the two s...

In semiarid and arid areas, it is important to understand the amount of rainfall reaching the ground in order to develop effective water plan strategies for the selection of the tree species for afforestation goals. We measured the rainfall interception and canopy storage capacity of individual trees of Pinus eldarica and Cupressus arizonica growin...

Presentation on the recent review article of the same name in Science of the Total Environment

Interactions between precipitation and forest canopy elements (bark, leaves, and epiphytes) control the quantity, spatiotemporal patterning, and the chemical concentration, character and constituency of precipitation to soils. Canopy epiphytes exert a range of hydrological and biogeochemical effects due to their diversity of morphological traits an...

Large-scale bioenergy production will affect the hydrologic cycle in multiple ways, including changes in canopy interception, evapotranspiration, infiltration, and the quantity and quality of surface runoff and groundwater recharge. As such, the water footprints of bioenergy sources vary significantly by type of feedstock, soil characteristics, cul...

We estimated the rainfall interception loss (I), canopy storage capacity (S), the ratio of mean evaporation rate from the wet canopy ( E ) over the mean rainfall intensity ( R ) (mm h-1) ( E / R ), and free throughfall coefficient (p) in a Fraxinus rotundifolia Mill. stand located in an afforested Park land in a semiarid region of Iran. For each st...

Seedlings of Artemisia herba-alba grown in glasshouse were watered with differing salinities (0, 150, 250 or 350 mM NaCl) and watering frequencies of 3, 7, 14 or 21 days for a period of 6 weeks. At the end of the study, plant survival, dry matter yield, biomass allocation (shoot and root), leaf area, relative growth rate (RGR), net assimilation rat...

The aim of this study was to estimate the individual tree-based 1) canopy water storage capacity (S), 2) ratio of mean evaporation rate from the wet canopy to the mean rainfall intensity (E / R) by the Pereira method, and 3) direct throughfall coefficient (p) for Cupressus arizonica trees. The trees were afforested in the Chitgar forest park in Teh...

From 30 January 2011 to 30 January 2012, we measured the rainfall interception (I) and canopy storage capacity (S) of individual trees of Pinus eldarica and Cupressus arizonica planted in the Chitgar Forest Park near Tehran, Iran. Gross rainfall (GR) in this semiarid region was measured using the mean of 6 plastic rain gauges placed in an open area...

Studies conducted across northern Europe and North America have shown increases in dissolved organic carbon (DOC) in aquatic systems in recent decades. While there is little consensus as to the exact mechanisms for the increases in DOC, hypotheses converge on such climate change factors as warming, increased precipitation variability, and changes i...

The main objectives of this study were to quantify the contribution of rainfall interception (I) and throughfall (TF), to gross rainfall (GR) and understand the role of GR amount in controlling I by the stand-based measurement of P. eldarica plantations, Tehran, Iran. GR was measured using the mean of 10 rain gauges placed in a near clearing area....

Canopy storage capacity (S) is the amount of water the canopy can hold while saturated. S is a key parameter of rainfall interception and other eco-hydrological processes. From 30 January 2011 to 30 January 2012, we measured the S of individual trees of Cupressus arizonica planted in the Chitgar Forest Park, Tehran, north of Iran. Cupressus arizoni...

It is necessary to consider the heterogeneity of rainfall interception (I) since it controls the water input to a forest plantation. The rainfall partitioning occurring in plantation forest ecosystems of the semiarid climate zone is suffering from insufficient information; especially information from individual tree measurements. We measured I of i...

Dissolved organic carbon (DOC) production, consumption, and quality displayed differences after long-term (~55 years) hydrological alterations in a poor fen peatland in northern Michigan. The construction of an earthen levee resulted in areas of a raised and lowered water table (WT) relative to an unaltered intermediate WT site. The lowered WT site...

Northern peatland water table position is tightly coupled to carbon (C) cycling dynamics and is predicted to change from shifts in temperature and precipitation patterns associated with global climate change. However, it is uncertain how long-term water table alterations will alter C dynamics in northern peatlands because most studies have focused...

We monitored CO2 and CH4 fluxes using eddy covariance from 19 May to 27 September 2011 in a poor fen located in northern Michigan. The objectives of this paper are to: (1) quantify the flux of CH4 from a sub-boreal peatland, and (2) determine which abiotic and biotic factors were the most correlated to the flux of CH4 over the measurement period. N...

Continuous measurements of ecosystem scale evapotranspiration (ET) were obtained using the eddy covariance method over the 2010 and 2011 growing seasons (May-September) at three adjacent peatlands that have undergone long-term water table manipulation. The three (wet, dry and intermediate) sites represent peatlands along a hydrological gradient, wi...

Forest canopy rainfall interception loss (I), canopy water storage (S), and the ratio of mean evaporation to mean rainfall intensity (E/R) are important components of the water balance in arid and semi-arid climate zones. The goal of this project was to quantify I and S and to evaluate the Gash interception model for rainfall interception in a matu...

Open top chambers (OTCs) and infrared (IR) lamps have been widely used for experimentally warming ecosystems, especially in high latitude and alpine regions. The efficacy of OTCs and IR lamps is variable, yet there has not been a direct, experimentally controlled comparison of these warming methods. We, therefore, implemented a factorial study in a...

A large wetland drainage project was initiated in 1912 near the town of Seney, Michigan, U.S.A. This project included the construction of a series of ditches through a large peatland to drain the land for agricultural use. The largest of these ditches was the 35 km long Walsh Ditch. Much of the drained wetland affected by the Walsh Ditch is now man...

While the hydrological balance of forest ecosystems has often been studied, quantitative studies on the seasonal variability of rainfall Interception (I) and Canopy Storage Capacity (S) by individual trees are less frequently reported. Hence, the effects of the seasonal variation in I and S by individual Persian oak trees(Quercus brantii var. Persi...

Interception loss (I) plays an important role in forest stand, but not well quantified in Iran. I and throughfall (TF) were measured over a four month period by a Fraxinus rotundifolia afforestation in the Chitgar Forest Park, near Tehran, Iran. Mean annual air temperature and precipitation are 17.1˚C and 269 mm, respectively. The gross rainfall (G...

Grassland degradation resulting from global climate change, overgrazing, and rodent damage is expected to influence the magnitude of canopy hydrological fluxes because of reduced vegetation biomass and changed species composition. The objectives of this study were to estimate herbaceous canopy rainfall storage capacity (S) along three different sta...

Forest canopy water storage (S), direct throughfall fraction (p) and mean evaporation rate to mean rainfall intensity ratio (E R) vary between storms and seasonally. Typically, researchers only quantify the mean growing and dormant season values of S, p and E R for deciduous forests, thereby ignoring seasonal changes S, p and E R . Past researchers...

Peatlands are a critical component in the global carbon (C) cycle because they have been slowly sequestering atmospheric greenhouse gases as peat since the last glaciation. Today, soil C stocks in peatlands are estimated to represent 224 to 455 Pg, equal to 12-30% of the global soil C pool. At present, peatlands are estimated to sequester 76 Tg C y...

Ammonia (NH3) is the most abundant alkaline gas in the atmosphere and forms secondary aerosol by neutralizing sulfuric and nitric acids that are released during combustion of fossil fuels. Ammonia is primarily emitted by cropping and livestock operations. However, C2 and C3 amines (pKb 3.3-3.4), which are stronger bases than NH3 (pKb 4.7) have been...

Widespread and intensive application of road deicers, primarily road salt (NaCl), in North America threatens water quality and the health of freshwater ecosystems. Intensive use of NaCl can be harmful to sensitive members of freshwater ecosystems such as amphibians. Detection of negative effects of NaCl application has prompted the search for alter...

Exotic ponderosa pine (Pinus ponderosa Doug. ex. Laws) is being planted for timber production in the natural distribution area of cordilleran cypress [Austrocedrus chilensis (D. Don) Pic. Serm. et Bizzarri] in the forest-steppe ecotone at the base of the Andes Mountains in northwest Patagonia. Our previous studies showed that transpiration of ponde...

The structure of forest canopies is highly heterogeneous at multiple scales. Leaves, twigs, and stems are not organized uniformly in space. For example, some plants have highly clustered leaves (e.g., conifers) while others are less clustered (e.g., Kira et al. 1969). Forest canopies contain gaps, but the size and distribution of these gaps is high...

Two species of alkaligrass, Nuttall's alkaligrass (Puccinellia nuttalliana [Schult.] Hitch.), a native, and weeping alkaligrass (Puccinella distans [Jacq.] Parl.), an introduced species from Eurasia, are found within semi-arid regions of the United States. Recently, land managers have become concerned over the ability of these two species to coloni...

The amount of biologically available water is arguably the central driver in plant processes. While many studies have examined the hydrological components of biologically available water, the role that vegetation water use plays within the forested ecosystem water balance is poorly understood. Fundamental questions of forests' effect on the hydrolo...

Studies conducted across northern Europe and North America have shown increases in dissolved organic carbon (DOC) in lake and stream water in recent decades. While there is little consensus as to the exact mechanisms for the increases in DOC, hypotheses converge on such climate change factors as warming, increased precipitation variability, and cha...

Patterns in the isotopic signal (stable C isotope composition; delta(13)C) of respiration (delta(13)C(R)) have led to important gains in understanding the C metabolism of many systems. Contained within delta(13)C(R) is a record of the C source mineralized, the metabolic pathway of C and the environmental conditions during which respiration occurred...

Patterns in the isotopie signal (stable isotope composition; δ¹³C) of respiration (δ¹³C R ) have led to important gains in understanding the metabolism of many systems. Contained within δ¹³C R is a record of the source mineralized, the metabolic pathway of and the environmental conditions during which respiration occurred. Because gas samples used...

Fiber-optic distributed temperature sensing (DTS) has great potential for spatial monitoring in hydrology and atmospheric science. DTS systems have an advantage over conventional individual temperature sensors in that thousands of quasi-concurrent temperature measurements may be made along the entire length of a fiber at 1 meter increments by a sin...