Charles P.-A. Bourque

Spatial mapping of growing degree days: an application of MODIS-based surface temperatures and enhanced vegetation index

Growing degree days (GDD) is a simple temperature-based index of biological development. In this paper we evaluated the potential of using 2003-2005 MODIS-based 8-day and 16-day composites of daytime surface temperature (TS) and enhanced vegetation index (EVI) values at 250 m resolution for mapping GDD. The work was applied to the Canadian Atlantic Maritime Ecozone as a demonstration of the methodology. The work proceeded by establishing an empirical relationship between mean tower-based estimates of TS for the MODIS-acquisition period of 10:30 am-12:00 pm and the daily mean TS calculated from half-hourly emitted infrared/longwave radiation measurements taken from four flux sites in southern commercial forests of Canada. The relationship revealed a strong correlation between variables (r2=98.4%) and was central to the calculation of daily mean TS from MODIS-based estimates of TS. Since seasonally-based estimates of GDD and EVI were strongly correlated (r2=87%), data fusion techniques were applied to enhance the GDD map originally produced at 1 km resolution (from infrared emission band data), to 250 m. In general, the MODIS-derived map of GDD showed a positive constant offset of about 511 degree days from calculated long-term averages (1971 2000) based on temperatures collected at 101 Environment Canada climate stations.

A Wetness Index Using Terrain-Corrected Surface Temperature and Normalized Difference Vegetation Index Derived from Standard MODIS Products: An Evaluation of Its Use in a Humid Forest-Dominated Region of Eastern Canada

In this paper we develop a method to estimate land-surface water content in a mostly forest-dominated (humid) and topographically-varied region of eastern Canada. The approach is centered on a temperature-vegetation wetness index (TVWI) that uses standard 8-day MODIS-based image composites of land surface temperature (TS) and surface reflectance as primary input. In an attempt to improve estimates of TVWI in high elevation areas, terrain-induced variations in TS are removed by applying grid, digital elevation model-based calculations of vertical atmospheric pressure to calculations of surface potential temperature (θS). Here, θS corrects TS to the temperature value to what it would be at mean sea level (i.e., ∼101.3 kPa) in a neutral atmosphere. The vegetation component of the TVWI uses 8-day composites of surface reflectance in the calculation of normalized difference vegetation index (NDVI) values. TVWI and corresponding wet and dry edges are based on an interpretation of scatterplots generated by plotting θS as a function of NDVI. A comparison of spatially-averaged field measurements of volumetric soil water content (VSWC) and TVWI for the 2003-2005 period revealed that variation with time to both was similar in magnitudes. Growing season, point mean measurements of VSWC and TVWI were 31.0% and 28.8% for 2003, 28.6% and 29.4% for 2004, and 40.0% and 38.4% for 2005, respectively. An evaluation of the long-term spatial distribution of land-surface wetness generated with the new θS-NDVI function and a process-based model of soil water content showed a strong relationship (i.e., r2 = 95.7%).

Simulations of pre- and post-harvest soil temperature, soil moisture, and snowpack for jack pine: comparison with field observations.

Quantifying temporal changes in soil temperature and moisture conditions is an important part of characterizing pre- and post-disturbance conditions that influence the health, productivity, and sustainability of forest ecosystems. In this paper, we present an experimental case study that was used to evaluate the ability of the forest hydrology model ForHyM2 to simulate field-observed changes in root-zone soil moisture and temperature, as well as snowpack depth, throughfall volume and forest floor percolate volume, for a jack pine (Pinus banksiana Lamb.) site in northeastern Ontario. The experiment refers to two post-harvest treatment factors, each involving two treatments: (a) blading (removing) or non-blading the forest floor and part of the mineral topsoil, (b) herbiciding or non-herbiciding. It was found that harvesting increased the average daily soil temperature by 4‐68C on all treatment plots during summer (5 cm soil depth). Blading increased the soil temperature further by 1‐28C. Herbiciding did not have significant effects on soil temperature. Eliminating competing forest vegetation significantly increased soil moisture level on the non-bladed treatment plots. The model simulations were based on daily precipitation (snow and rain), air temperature, and a few site descriptors such as longitude and latitude, soil depth, soil texture, and leaf area index. The resulting simulations compared well (graphically) with the pre- and post-harvest field observations regarding soil moisture, soil temperature, and snowpack water equivalents. Good graphical agreements suggest that the approach taken with this case study can be applied to the evaluation of soil moisture and temperature conditions to a variety of pre- and post-disturbance forest conditions. The results from the study would be useful for addressing below ground processes such as root growth, soil respiration, rate of organic matter decomposition, rate of soil weathering, nutrient cycling, etc., all of which strongly influence site productivity. # 2000 Elsevier Science B.V. All rights reserved.

Modeling acclimation of photosynthesis to temperature in evergreen conifer forests.

• In this study, we used a canopy photosynthesis model which describes changes in photosynthetic capacity with slow temperature-dependent acclimations. • A flux-partitioning algorithm was applied to fit the photosynthesis model to net ecosystem exchange data for 12 evergreen coniferous forests from northern temperate and boreal regions. • The model accounted for much of the variation in photosynthetic production, with modeling efficiencies (mean > 67%) similar to those of more complex models. The parameter describing the rate of acclimation was larger at the northern sites, leading to a slower acclimation of photosynthesis to temperature. The response of the rates of photosynthesis to air temperature in spring was delayed up to several days at the coldest sites. Overall photosynthesis acclimation processes were slower at colder, northern locations than at warmer, more southern, and more maritime sites. • Consequently, slow changes in photosynthetic capacity were essential to explaining variations of photosynthesis for colder boreal forests (i.e. where acclimation of photosynthesis to temperature was slower), whereas the importance of these processes was minor in warmer conifer evergreen forests.

Comparison of three simple field methods for ammonia volatilization from manure

Land application of swine manure can result in a loss of nitrogen (N) through ammonia (NH3) volatilization. Accurate NH3 loss assessments are essential to support the development of regional and global emission factors and identify best management strategies for reducing losses. The objectives of this study were to simultaneously assess the reliability and applicability of three simple NH3 flux measurement techniques and their effectiveness and usefulness for the measurement of emissions from surface-applied swine manure. Ammonia losses from two chamber systems were compared: (i) static and (ii) wind tunnel chamber, as well as the (iii) micrometeorological theoretical profile shape (TPS) method. A series of field tests was performed at the Agriculture and Agri-Food Canada (AAFC) Research Farm in Harrington, Prince Edward Island (PE) on a sandy loam, stubble field that was surface applied with 100 kg NH4-N ha-1 of liquid swine manure. After application the three NH3 emission techniques were established and...

A forest nutrient cycling and biomass model (ForNBM) based on year-round, monthly weather conditions, part I: assumption, structure and processing

A forest nutrient cycling and biomass growth model was developed to simulate nutrient cycling and NPP based on site and monthly mean weather conditions. A modular design was used to partition northern forest ecosystems into separate modules that address the following ecological variables: (1) hydrologic processes and temperatures to estimate moisture, percolation and temperature in forest floor, soil and subsoil; (2) soil acidity to estimate the H-ion balance in the soil, in the context of atmospheric deposition, nutrient uptake, weathering, and soil-ion retention; (3) cycling of N, S, Ca, Mg, and K to estimate nutrient uptake, mineralization, nitrification, immobilization, mineral soil weathering, nutrient exchange between soil exchange sites and solution, and nutrient leaching associated with atmospheric deposition; and (4) biomass to estimate NPP and its allocation to foliage, wood, and root, as well as litterfall and decomposition. After the model calibration, verification and validation, the model can be applied (1) to predict the rate of sustainable nutrient harvesting based on nutrient geochemical balance; (2) to determine limiting nutrients for forest growth; (3) to evaluate the effects of atmospheric acidic deposition on soil chemistry and growth; and (4) to evaluate the effects of forest harvesting on environmental issues, such as stream water quality.

Potential Species Distribution of Balsam Fir Based on the Integration of Biophysical Variables Derived with Remote Sensing and Process-Based Methods

Abstract: In this paper we present a framework for modelling potential species distribution (PSD) of balsam fir [bF; Abies balsamea (L.) Mill.] as a function of landscape-level descriptions of: (i) growing degree days (GDD: a temperature related index), (ii) land-surface wetness, (iii) incident photosynthetically active radiation (PAR), and (iv) tree habitat suitability. GDD and land-surface wetness are derived primarily from remote sensing data acquired with the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on the Terra satellite. PAR is calculated with an existing spatial model of solar radiation. Raster-based calculations of habitat suitability and PSD are obtained by multiplying normalized values of species environmental-response functions (one for each environmental variable) parameterized for balsam fir. As a demonstration of the procedure, we apply the calculations to a high bF-content area in northwest New Brunswick, Canada, at 250-m resolution. Location of medium-to-high habitat suitability values (i.e., >0.50) and actual forests, with >50% bF, matched on average 92% of the time.

Management strategies to simultaneously reduce ammonia, nitrous oxide and odour emissions from surface-applied swine manure

Surface-applied swine manure has the potential to generate ammonia (NH3), nitrous oxide (N2O) and odour. Field research was conducted in Prince Edward Island to measure the simultaneous emissions of NH3, N2O and odour following the surface-application of swine manure. Manure was applied to a grain stubble field consisting of a sandy loam soil low in pH (5.6–5.9). The effect of manure type (liquid and solid), application rate [conventional/typical rate (1 ×): 30 000-36 000 L ha-1, double (2 ×): 60 000-72 000 L ha-1 and five times (5 ×): 180 000 L ha-1] and rainfall (8–200 mm) before and after liquid manure application were examined. There was no relationship between odour emissions and manure type, application rate and rainfall before and after spreading, due to high variability. Liquid manure (dry matter (DM = 45 g kg-1) reduced NH3 emissions by 32% compared with solid (DM = 350 g kg-1). Increasing application rates enhanced NH3 emissions; increasing the rate by 2 × and 5 × the typical rate increased loss...

Application of Landsat-7 ETM+ and MODIS products in mapping seasonal accumulation of growing degree days at an enhanced resolution

This paper describes a procedure for mapping long-term average, growing season-accumulated growing degree days at an enhanced spatial resolution of 28.5 m. GDD-product enhancement is based on augmenting a previously developed 1 km resolution map of GDD described in Hassan et al. [J. Applied Remote Sens., 1, 013511, 12p (2007)] using data from a series of scene- and date-specific Landsat-7 ETM+ images (at 28.5 m resolution) from the 1999-2002 data collection period and a chronological series of standard MODIS 16-day composites of enhanced vegetation index (EVI; at 250 m resolution) spanning the 2003-2005 growing periods (April-October). Surface reflectances from the Landsat-7 ETM+ images are used to derive fine-scale estimates of EVI, which are then transformed into long-term averages by taking into account growing-season specific, temporal trends in the series of MODIS-EVI images. As values from the 8-day accumulated GDD and 16-day composites of EVI have been shown to be strongly correlated, a new data-fusion method based on the mean and instantaneous values of fine-grain long-term average EVI is used to augment the resolution of the initial GDD map. As a demonstration, we apply the procedure to satellite and climate station data for the Canadian Province of Nova Scotia.

Spatial prediction of tree and shrub succession in a small watershed in Northern Cape Breton Island, Nova Scotia, Canada

Abstract This paper describes the development of a spatially-explicit forest transition model for the Clyburn River Valley watershed in northern Cape Breton Island, Nova Scotia, Canada. The model links spatial quantities of available sunlight, degree-day accumulation and soil water content to the establishment and growth of individual tree and shrub species. Environment-species interactions are captured by way of an artificial neural network (ANN) trained to detect temporal patterns produced with a forest gap model (GIZELA) calibrated for environmental and forest species conditions encountered in northern Cape Breton Island. Impact of environmental conditions on forest succession is expressed through numerical adjustments of the ANN-produced forest-transition projections for several representative landscape types. The ANN-transition modelling approach used is largely automated, making it easy to apply at the species level. ANN calculations explain >95% of the variation present in all GIZELA simulations. Forest-transition calculations are subsequently applied to a representative area of the Cape Breton Highlands as a demonstration of the landscape application of the ANN. Forest-transition modelling can aid in the understanding and prediction of natural forest succession at the landscape level, facilitating the development of long-term conservation plans.