Modelling minimum air temperature in partially and clear felled forests (original) (raw)
Related papers
2010
The objective of this study is to describe winter and summer surface air and forest floor temperature patterns and diurnal fluctuations in high-elevation red spruce (Picea rubens Sarg.) forests with different levels of canopy cover. In 1988, a series of 10-x 10-meter plots (control, low nitrogen [N] addition, and high nitrogen addition) were established on Mount Ascutney, VT, to examine the influence of N fertilization on red spruce and balsam fir (Abies balsamea Mill.) forest N cycling, tree mortality, and forest growth. As a result of N addition to the plots, species mortality has occurred on the low N and high N plots with the control plots experiencing very little mortality. Consequently, the mortality experienced on the low N and high N plots reduced forest cover and created both patchy and open forest canopies. In 2002, we installed temperature probes on the existing high-elevation red spruce to begin describing surface air (2 cm above ground) and forest floor temperature (2 cm below ground) patterns under different levels of canopy cover. In June 2006 we established four new 10x 10-meter red spruce plots, girdling 50 percent of the trees in two plots and 100 percent in the other two plots to further test surface air and forest floor temperature ranges under an altered forest canopy. Summer diurnal fluctuations in surface air temperature were highest on the high N plots (9.5 °C to 12.8 °C) during all years except 2007, where the 100 percent girdled plots had the highest summer diurnal value, 19.7 °C. Winter diurnal fluctuations in surface air temperature were lowest on the high N plots for all years. Summer diurnal fluctuations in forest floor temperature were highest on the high N plots for all years, while the winter diurnal fluctuations in forest floor temperature showed little variability between plots. Summer mean maximum, mean minimum, and mean surface air and forest floor temperatures were higher on the high N and/or 100-percent girdled plots in any given year. Summer mean maximum air temperature was highly related to percent canopy cover (r 2 = 0.94, p=0.006). As a result of direct solar radiation and the hot air that reaches and heats the ground surface through gaps and open canopies, 1-or 2-year-old red spruce seedlings might be negatively affected.
Influence of canopy cover on surface temperature
Revista Brasileira de Geografia Física, 2020
Trees affect the microclimate, which influences thermal comfort and ecosystem processes. This study investigated the influence of the canopy cover on daily maximum and minimum temperatures. The data are from a collaborative database, and each measurement consists of the minimum and maximum temperatures under the canopy and in an open adjacent area over a 24-hour period. Paired sample t-tests indicated that the canopy decreased the maximum and minimum daily temperatures and narrowed the daily temperature range. Multiple regression showed that the canopy cover percentage decreased the maximum daily temperatures, and this effect was greater in rural areas than in urbanized areas. Another multiple regression indicated that the canopy cover percentage and the distance to the edge of the canopy decreased the daily temperature range. An independent sample t-test also indicated that the effect of the canopy on the daily temperature range was higher in rural areas when analysed by parametric and non-parametric tests but not when measured by a robust test. Other independent sample t-tests indicated that the distance from a light source also decreased the canopy effect on the minimum daily temperature and the daily temperature range. The main plausible underlying processes include the canopy shade and wind insulation, litter insulation of the ground surface, heat pumps through evapotranspiration and lateral heat fluxes from light bulbs and other anthropogenic sources, especially in urbanized areas. These results provide a greater understanding of the effects of arborization in rural and urban ecosystems, as well as their respective benefits to human communities.
Nocturnal cooling below a forest canopy: Model and evaluation
Agricultural and Forest Meteorology, 2011
Nocturnal cooling of air within a forest canopy and the resulting temperature profile may drive local thermally driven motions, such as drainage flows, which are believed to impact measurements of ecosystem-atmosphere exchange. To model such flows, it is necessary to accurately predict the rate of cooling. Cooling occurs primarily due to radiative heat loss. However, much of the radiative loss occurs at the surface of canopy elements (leaves, branches, and boles of trees), while radiative divergence in the canopy air space is small due to high transmissivity of air. Furthermore, sensible heat exchange between the canopy elements and the air space is slow relative to radiative fluxes. Therefore, canopy elements initially cool much more quickly than the canopy air space after the switch from radiative gain during the day to radiative loss during the night. Thus in modeling air cooling within a canopy, it is not appropriate to neglect the storage change of heat in the canopy elements or even to assume equal rates of cooling of the canopy air and canopy elements. Here a simple parameterization of radiatively driven cooling of air within the canopy is presented, which accounts implicitly for radiative cooling of the canopy volume, heat storage in the canopy elements, and heat transfer between the canopy elements and the air. Simulations using this parameterization are compared to temperature data from the Morgan-Monroe State Forest (IN, USA) FLUXNET site. While the model does not perfectly reproduce the measured rates of cooling, particularly near the top of the canopy, the simulated cooling rates are of the correct order of magnitude.
Agricultural and Forest Meteorology, 2004
A new model (soil temperature under forests-STUF) is described for predicting the seasonal variation of daily average temperature within surface soil layers under a range of forest types from the time of establishment through to harvesting. Daily air temperature for the period of simulation (greater than 1 year) was used to estimate the average annual air temperature, its amplitude, and daily fluctuations. Daily soil temperatures were then predicted from this information using empirical modifications to allow for the effects of canopies of trees, understorey and weeds, mass of the litter layer, and depth at which soil temperature is predicted. Measurements of soil temperature under a range of forest species, ages and management systems were available for 51 sites across southern Australia. The model was parameterised to 31 of these data sets, and the remainder used for validation. The model explained 85% of the variation in observed average daily soil temperature in the latter. Despite the wide range in observed canopy and litter cover, model performance was maintained. Sensitivity analysis indicated that the most important input data required were air temperature, leaf area index and soil depth. For less important inputs such as mass of litter and fraction of ground area covered by weeds or understorey, it may be adequate to use either default values or a scoring procedure for ground cover fractions. The model provides a simple and accurate means to predict daily temperatures in soil in any chosen depth increment. It can be used where accurate daily predictions of average soil temperature are required in a soil profile, for example to generate data to drive a model of organic matter decomposition and mineralisation of nutrients.
Hydrological Processes, 1999
Heat and water exchange in forest areas constitutes one of the most important hydro-meteorological systems. In this study, the energy balances above three forests were measured during winter. Two were evergreen conifer forests and the third was a lea¯ess deciduous forest. From this study, we gained the following new insights: there were no signi®cant dierences between the magnitudes of the net all-wave radiation and sensible heat, and the ratio of sensible heat to net all-wave radiation between the three experimental forests, despite the marked dierences in canopy conditions. The net short-wave radiation was larger above the evergreen forests than above the deciduous forest, because of the low albedo above the evergreen forest. The converse was true, however, for net long-wave radiation, especially in the daytime. This was due to the dierence in the upward long-wave radiation, because the deciduous forest canopy was quite sparse and some of the long-wave radiation emitted from the snow surface reached the atmosphere through the canopy. There was no clear dierence in the net all-wave radiation above the two types of canopy. Canopy conditions caused major dierences in roughness length and zero plane displacement. In the deciduous forest, the zero plane displacement was small and the roughness length was large, while in the evergreen forest the opposite was true. In the deciduous forest, the area in contact with the atmosphere increased because of the low position of the`active surface', and the roughness length was also high. Consequently, the sensible heat from the deciduous forest did not dier from that of the evergreen forests.
Patterns of maximum and minimum air and soil temperatures near a forest edge
Archiv für Meteorologie, Geophysik und Bioklimatologie Serie B, 1972
The patterns of maximum and minimum air and soil temperatures were investigated outward from a west facing forest edge, through a stand of pioneer shrub (broom) to an open field. The study included the period May-October t970. Summer maximum air temperatures were generally higher near, but not at, the forest edge; especially over the raised radiative surface of the broom. Minimum air temperatures were highest near the forest edge in both summer and fall and were lowest over the raised broom surface. Maximum soil temperatures were warmest near the open field where greater exposure to solar radiation was a major controlling factor. Summer minimum soil temperatures were highest in the open field, those of the fall under the protective broom cover. A cut through the broom produced some interesting effects and acted as a miniature frost pocket. Zusammenfassung Die Verteilung der Maxima und Minima der Luft-und Bodentemperaturen in der Niihe eines Waldrandes Es wird die Verteilung der Maxima und Minima der Luft-und Bodentemperatur yon einem Westrand eines Waldes fiber einen vorgelagerten Ginstergebiischstreifen bis ins Freiland untersucht. Die Untersuchung erstreckt sich auf die Periode Mai bis Oktober 1970. Die sommerlichen Maxima der Lufttemperatnr waren im allgemeinen nahe, jedoch nicht unmittelbar am Waldesrand, besonders fiber der im Gebiischstreifen gehobenen wirksamen Strahlungsfliiche h/Sher. Die Minima der Lufttemperatur waren im Sommer und im Herbst nahe dem Waldesrand am h6chsten und am niedrigsten fiber dem Gebiischstreifen. Die h6chsten Bodentemperaturen wurden im freien Feld erreicht, wo die gr6t~ere Exposition
The 1st International Electronic Conference on Forests—Forests for a Better Future: Sustainability, Innovation, Interdisciplinarity, 2020
In recent decades, relatively few experimental studies have been carried out in which the micrometeorological conditions have been studied over different small clearings plots of the forest. As these conditions can significantly affect many processes in the ecosystem, two questions arise: (1) whether and how the microclimatic conditions differ in the clear-cut and the gap, and (2) how heterogeneous the distribution of these conditions is on these plots. The aim of this study was to determine the spatial variation of air temperature on the clear-cut and gap as well as to compare the distribution of thermal and humidity conditions in both areas. The research was carried out in central Poland on a clear-cut with a width of 60 m and on a gap of an ellipsoid shape (40 × 70 m). The measurements were carried out in two series: spring-summer, during the period when the height of the sun during the day conditioned the inflow of direct solar radiation to any surface (May-August 2006), and autumn, when direct radiation was limited by neighbouring stands (October-November 2006). Average values of air temperature on the gap in the spring-summer period differed in individual parts of 2.2 °C, while on the clear-cut by 1.0 °C. In the autumn, thermal diversity on both research plots was similar (average 0.8 °C). The thermal diversity within the research areas was particularly marked in the case of extreme air temperature values. We found the modest spatial diversification of humidity parameters: vapour pressure, relative humidity, and humidity deficit. The particularly large diversification of relativity humidity and vapour pressure deficit occurred during the spring-summer period in the context of heat waves. The least beneficial thermal and humidity conditions for growing plants occurred in the northeastern (NE) parts of the clear-cut and gap, which is why it is necessary to take particular note of these locations when undertaking silviculture.
TIMBER v0.1: a conceptual framework for emulating temperature responses to tree cover change
Society is set to experience significant land cover changes in order to achieve the temperature goals agreed upon under the Paris Agreement. Such changes carry both global implications, pertaining to the biogeochemical effects of land cover change and thus the global carbon budget, and regional/local implications, pertaining to the biogeophysical effects arising within the immediate area of land cover change. Biogeophysical effects of land cover change are of high relevance to national policy-and decision-makers and their accountance is essential towards effective deployment of land cover practices that optimises between global and regional impacts. To this end, ESM outputs that isolate the biogeophysical responses of climate to land cover changes are key in informing impact assessments and supporting scenario development exercises. Generating multiple such ESM outputs, in a manner that allows comprehensive exploration of all plausible land cover scenarios however, is computationally untenable. This study proposes a framework to agilely explore the local biogeophysical responses of climate under different land cover scenarios by means of a computationally inexpensive emulator, TIMBER v0.1. The emulator is novel in that it solely represents the land cover forced, biogeophysical responses of climate, and can be used as either a standalone device or supplementary to existing climate model emulators that represent greenhouse gas (GHG)-or Global Mean Temperature (GMT)-forced climate responses. We start off by modelling local minimum, mean and maximum surface temperature responses to tree cover changes by means of a month-and Earth System Model (ESM)-specific Generalised Additive Model (GAM) trained over the whole globe. 2-m air temperature responses are then diagnosed from the modelled minimum and maximum surface temperature responses using observationally derived relationships. Such a two-step procedure accounts for the different physical representations of surface temperature responses to tree cover changes under different ESMs, whilst respecting a definition of 2-m air temperature that is more consistent across ESMs and with observational datasets. In exploring new tree cover change scenarios, we employ a parametric bootstrap sampling method to generate multiple possible 1
Ecological Modelling, 2009
A three-dimensional model Mixfor-3D of soil-vegetation-atmosphere transfer (SVAT) was developed and applied to estimate possible effects of tree clear-cutting on radiation and soil temperature regimes of a forest ecosystem. The Mixfor-3D model consists of several closely coupled 3D sub-models describing: forest stand structure; radiative transfer in a forest canopy; turbulent transfer of sensible heat, H 2 O and CO 2 between ground surface and the atmospheric surface layer; evapotranspiration of ground surface vegetation and soil; heat and moisture transfer in soil. The model operates with the horizontal grid resolution, 2 m × 2 m; vertical resolution, 1 m and primary time step, 1 h.