Changes in canopy cover alter surface air and forest floor temperature in a high-elevation red spruce (Picea rubens Sarg.) forest (original) (raw)
Related papers
Temperatures at the margins of a young spruce stand in relation to aboveground height
iForest - Biogeosciences and Forestry, 2013
Air temperature was monitored at a summit of the Jizerské hory Mountains (Czech Republic) in the vicinity of the northern and southern margins of a young Norway spruce stand (tree height approx. 4.5 m) at 30, 60, 90 and 140 cm aboveground. Temperature sensors were placed at height intervals selected to represent terminal shoot heights in the planting stock of different treeheight categories (seedlings, semi-saplings and saplings). As reference, a point 30 cm aboveground in an adjacent treeless gap between stands was monitored. Measurements were taken in two periods, from April to October 2010 and 2011. Differences were evaluated in terms of mean temperature characteristics of the ground air layer in the stand gap and in each station at the stand margins. Differences in temperature extremes (minimum, maximum, range) values showed more conspicuous fluctuations than differences in mean values. The observed difference in the course of daily temperature in the ground air layer (up to 30 cm aboveground) between the stand gap and the southern margin of the spruce stand was small. The ground layer of air at the northern margin was markedly colder and showed a more stable course of temperatures. Decreasing temperature fluctuations were observed as distance from the ground increases, and frequency and intensity of ground frosts also decreased with sensors' height. At 140 cm aboveground (i.e., at approximately one-third of the spruce stand's height), differences between daily temperature characteristics at the southern and northern stand margins were small over the growing period, and the occurrence of late or early frosts showed comparable frequencies. In conclusion, higher risk of damage to small-sized planting stock due to temperature stress was confirmed for higher mountain elevations. For the reconstitution of young coniferous stands, the choice of suitable planting sites within a small clear-cut area is relevant (in terms of temperatures near the terminal shoot) only when planting stocks of small dimensions are used.
Atmospheric Environment. Part A. …, 1992
Recent evidence suggests that the decline of red spruce in the northeastern United States is directly related to freezing injury during winter. As part of a study on the relationship between red spruce decline and winter conditions, within-canopy micrometeorological measurements were taken in a subalpine red spruce (Picea rubens Sarg.)-balsam fir (Abies balsamea (L) Mill.) forest on Mt Moosilauke in central New Hampshire during the winter and early spring of 1990 and during the late fall, winter and early spring of 1991. At 880-and 1010-m elevation in 1990 and at 880-m elevation in 1990-1991, solar radiation and relative humidity were recorded at one height within the canopy, and air temperature and wind speed were recorded at two heights within the canopy. Hourly mean and maximum temperatures were slightly greater in the upper canopy than in the lower canopy. Both the maximum (26.1°C) and minimum (-27.6°C) temperatures of the study were recorded in the upper canopy at the 1010-m elevation study site. The maximum temperature drop that occurred within one hour and also spanned freezing was 9°C. Temperature minima below -35°C and much greater rapid temperature drops are believed to be necessary to cause or induce red spruce freezing injury. It appears that conditions during the study period were not severe enough to cause freezing injury; this conclusion was supported by the relatively small amount of visible injury observed in the periods following the study. These data on winter microclimate in a spruce-fir forest should be of value to investigators studying freezing injury and to other forest scientists.
Midwinter needle temperature and winter injury of montane red spruce
Tree Physiology, 1993
To assess the role of solar warming and associated temperature fluctuations in the winter injury of sun-exposed red spruce foliage, we used fine wire thermocouples to monitor midwinter needle temperature in the upper canopy of mature red spruce trees over two winters. In 1989-1990, 15mm mean temperatures were recorded for six needles in a single tree. In 1990-l 99 1, 1 0-min mean temperatures of six needles in one tree, and 1-min mean temperatures of seven needles in a second tree were recorded during rapid temperature changes. Warming was more frequent and greatest on terminal shoots of branches with a south to southwest aspect. The maximum rise above ambient air temperature exceeded 20 "C, and the maximum one minute decrease in temperature was 9 'C, with maximum rates of 0.8 and 0.6 "C min-' sustained over lo-and 1%min intervals, respectively. These data demonstrate that red spruce is subject to rapid temperature fluctuations similar to those known to produce visible injury in American aborvitae, a much hardier species. We concluded that solar warming to temperatures above the freezing point was unlikely to result in dehardening and subsequent freezing injury, because warming was infrequent, of short duration, and did not always raise needle temperature above the freezing point. Parts of branches and some individual shoots were frequently covered by snow or rime that may have prevented injury by reducing the frequency or intensity of needle temperature fluctuations. Radiation load on exposed shoots may have been increased by reflection of short wave radiation from snow and rime deposits on surrounding surfaces, which would exacerbate temperature fluctuations.
Journal of Forest Science
Reduced air pollution load has allowed to use commercially oriented forestry in the Central European mountains since the 1990s. The goal is, however, to restore species-and age-diversified stable stands that are expected to cope with uncertain changes of the harsh mountain climate. The microclimate of current young forest stands can impact on growth and performance of underplanted seedlings. In the present study, aboveground (+10 cm), surface (0 cm) and belowground (-10 cm) temperatures were compared under Norway spruce and Carpathian birch canopies. Measurements were performed in 22-year-old Norway spruce and Carpathian birch stands and replicated three times. These measurements were compared with three adjacent gaps dominated by herbal vegetation. Temperatures were measured automatically during the growing periods 2011 and 2012. The research was conducted on Norway spruce on an acidic Spodosol forest site in the summit part of the Jizerské hory Mts., Czech Republic. Data were analysed using the Horn procedure of pivot measures. The highest variability of aboveground and soil surface temperatures was observed within the gaps during a spring time. The temperatures beneath the leafless birch were close to those within the gaps, whereas in the period of leaved trees the temperature extremes were reduced similarly like under the spruce stand canopy compared to the gaps. The differences between the plots were the smallest at the end of growing seasons.
THE EFFECT OF TREES ON TEMPERATURE
The objective of this study is to quantify the effects of trees in a Midwest urban area on air temperature and humidity to determine if the effects are significantly different for: different species of trees, trees of the same species in different environments, and whether the effects can be explained by physical characteristics of the individual trees. Replicate trees in each of five categories were studied: sugar maple, pin oak and walnut individuals overgrass, sugar maple individuals along streets over concrete, and sugar maple clumps over grass. All the trees show a consistent effect: temperatures are reduced and humidities are elevated under the canopies. The greatest cooling effect (0.7 -1.3°C) occurs in the early afternoon. The difference between species is insignificant, but street trees are significantly less effective in reducing temperature than either individual trees or clumps planted over grass. The clumps had no greater effect than the individual trees. The amount of cooling observed in this study was considerably less than that documented in many previous studies. No consistent linear relationships were determined between physical characteristics of the trees, such as leaf area index, and temperature reductions or humidity increases.
Dendrochronologia, 2004
This study explores the influence of temperature on the growth of six northern range margin (NRM) tree species in the Hudson River Valley (HRV). The HRV has excellent geographic and floristic qualities to study the influence of climate change on forested ecosystems. Indices of radial growth for three populations per species are developed and correlated against average minimum and maximum monthly temperatures from 1897 to 1994. Only positive correlations to temperature are considered for this analysis. Principal component analysis (PCA) is performed on chronologies over the entire HRV and at four subregions. PCA reveals a strong common signal among populations at subregional and regional scales. January temperatures most limit growth at the ecosystem level, supporting the hypothesis that winter temperatures may control vegetational ecotones. Surprisingly, growth of the oak-hickory ecosystem is most limited by January temperatures only in the southern half of the study region. Chestnut and white oak are the primary species driving the geographic pattern. As winter xylem embolism is a constant factor for ringporous species, snow cover and its interaction on fine root mortality may be the leading factors of the pattern of temperature sensitivity. Species-specific differences in temperature sensitivity are apparent. Atlantic white-cedar (AWC) and pitch pine are more sensitive to the entire winter season (December-March) while oak and hickory are most sensitive to January temperatures. AWC is most sensitive species to temperature. Chestnut and white oak in the HRV are more sensitive to winter temperature than red oak. Pignut hickory has the most unique response with significant relations to late growing season temperatures. Interestingly, AWC and pitch pine are sensitive to winter temperatures at their NRM while oak and hickory are not. Our results suggest that temperature limitations of growth may be species and phylogenetically specific. They also indicate that the influence of temperature on radial growth at species and ecosystem levels may operate differently at varying geographic scales. If these results apply broadly to other temperate regions, winter temperatures may play an important role in the terrestrial carbon cycle.
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.
The effect of growing season and summer greenness on northern forests
Geophysical Research Letters, 2004
We investigate the physiological effects of the elongation of the growing season and the increase in summer greenness on northern hemisphere forests by examining the relationship between NDVI and tree rings. These variables are correlated during June and July only. These results suggest that NDVI proxies the physiological status of trees and that the summer status of the canopy has a larger effect on tree vigor than the duration of the canopy.
Responses of white spruce (Picea glauca) to experimental warming at a subarctic alpine treeline
Global Change Biology, 2007
From 2001 to 2004 we experimentally warmed 40 large, naturally established, white spruce [Picea glauca (Moench) Voss] seedlings at alpine treeline in southwest Yukon, Canada, using passive open-top chambers (OTCs) distributed equally between opposing north and south-facing slopes. Our goal was to test the hypothesis that an increase in temperature consistent with global climate warming would elicit a positive growth response. OTCs increased growing season air temperatures by 1.8°C and annual growing degree-days by one-third. In response, warmed seedlings grew significantly taller and had higher photosynthetic rates compared with control seedlings. On the south aspect, soil temperatures averaged 1.0°C warmer and the snow-free period was nearly 1 month longer. These seedlings grew longer branches and wider annual rings than seedlings on the north aspect, but had reduced Photosystem-II efficiency and experienced higher winter needle mortality. The presence of OTCs tended to reduce winter dieback over the course of the experiment. These results indicate that climate warming will enhance vertical growth rates of young conifers, with implications for future changes to the structure and elevation of treeline contingent upon exposure-related differences. Our results suggest that the growth of seedlings on north-facing slopes is limited by low soil temperature in the presence of permafrost, while growth on south-facing slopes appears limited by winter desiccation and cold-induced photoinhibition.
Forest science, 2000
Soil temperature is very important in regulating ecosystem processes, yet it is often difficult and costly to measure. Most models that have endeavored to predict soil temperature have either a long time step or several complicated independent variables. Daily mean air and soil temperatures were measured from 1989-1997 in four northern hardwood sites along a 500 km latitudinal gradient in Michigan. These data were used to derive a simple method to predict daily mean soil temperature (depth of 15 cm) using the daily mean air temperature from the previous day and a cosine function of Julian date (R 2 = 0.93-0.96; SEM = 0.98-1.40øC). Predicted values were compared with actual recorded soil temperatures from 1997 at each of the sites, and the average difference between the observed and predicted values ranged from 0.11 to 0.39øC. Different coefficients were estimated for each of the sites; however, this general method of predicting soil temperature appears applicable to any site. Once calibrated for a given site, soil temperature may be simply estimated, thus reducing the need for extended monitoring efforts. This method also allows the reconstruction of soil temperature records beyond the monitoring period. Projecting long-term trends in soil temperature may help to further elucidate several ecosystem processes and also may provide more information on how a changing global climate will impact forest ecosystems. FOR. Sc•. 46(2):297-301.