| A unit of Lasting Forests
evolving since March 30, 1999 |
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A Total Forest Management Plan
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A sun and moon website for daily conditions is available.
Solar Radiation information for your forest is as follows (other material is under development):
An annual day-length table once in CAPS, is being re- developed.
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A "solar mountain" can be used in designing recreational and administrative buildings. It, with minimum and maximum lines drawn for perceived faunal extremes (rather than the 65-degree line) may provide insights into the difference in productivity or suitability of areas. Changing "elevation" on such mountains represents percentages of simultaneously-occurring daily solar radiation values (percent of possible sunshine on cloudless days) and mean daily temperature. Elevations left of the 65°F line show a potential for building overheating and thus the need for design options. Optimum conditions for a species can be marked on the solar mountain with a line or zones. |
Light (short-wave) for the forest comes from the solar disc and in addition blue light (long-wave) is received due to Rayleigh scattering of solar radiation by molecules and white light is received from scattering by cloud or duct particles. Errors in measuring net radiation are expected to be about 15%. Measurement devices must be carefully calibrated; location under canopies is critical; overcast skies supress differences. Understanding the light over and within forests is very difficult.
A Langley is a expression of energy sun light received and is equal to calories/cm2 / minute. or 4.184 x 104 joules per square meter . It is also equivalent to 1 gm. cal. cm-2
In this area the Langleys per day in January are about 175; in July 575.
For any locality and time, the sun's angular elevation (a) and its angular distance from geographical south (b) may be found by
sin a = sin K sin D + cos K cos D cos h
sin b = cos D sin h / cos a
where h is the hour angle of the sun which is the difference between the given time and the time of apparent noon, expressed in degrees where 1 h is 15 degrees. K is the latitude of the location. D is the sun's angle of declanation for that time of year, given in nautical and astronomical almanacs. Leaf interception of light is related to this angle, generally the more horizontal the better. Grace(1971) observed that the pattern of brightness in nature will often be modified by the presenece of topographical obstructions or by taller plants in a vicinity. Little is known of morphological responses of plants to skies of different brightness but most believe that the majority of plant orient their leaves in the direction of incident light. In well-lit situations the leaves are parallel to the incident light; in shady situations they are perpendicular to the brightest areas. Since chloroplast movement occurs, "...the prediction of canopy photosynthesis may be a more complex problem than has been supposed."
A table was once produced with the following headings
| Julian Day |
Standard Date |
Daylight | Twilight | Day Length |
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| Sunrise | Sunset | Morning | Evening | |||||||
| EST | DST | EST | DST | EST | DST | EST | DST | |||
| 1 | Jan 1 | 750 | 850 | 1705 | 1805 | 722 | 822 | 1732 | 1832 | 9.55 |
Only 1/10 to 1/5th of one percent of the net solar energy from radiation that enters any forest of the region is used by plants. Most of the energy (about 6 to 8 langleys per day) is tied up in leaf production rather than in wood production. In Ohio most of the state receives less than 350 Langleys; a small southern portion receives more
| Stand Number | Light Reaching the Forest Floor |
Percent of Light Intercepted by Forest Canopy |
| 1 2 3 4 |
18 15 15 18 |
82 85 85 82 |
The first line of the above small table can be read as meaning that about 18 percent of the light in the spring and summer reaches the floor of your forest.
This means that about 82 percent has been screened or filtered out by the tree and shrub canopy. The higher the percent removed, the more dense the vegetation above the ground. This percent is a strong index to how suitable the area is for forest bird species diversity. (Of course there are other factors.)
Smith et al. (1989) described umbra and penumbral effects of light penetration in forests. They provide specific technical definitions of sunfleck, sunpatch, gap, and clearing based of such sunlight.
Understory growth is greatest where light is greatest. Oak seedlings and sapl-ings, for example, as part of the understory, are strongly and positively related to the amount of light.
Certain seeds, like those of the sycamore, germinate much better in strong light. Dense forests exclude some species, provide very suitable conditions for others.
Under development: A solar radiation GIS map of the forest and region from the work of Klopfer:
Klopfer, S. D. 1998. Insolation, precipitation, and moisture maps for a
A landscape shade map.
BASIC program UF09 computes the amount of light reaching the forest floor in each forest stand. The analysis is based on the equations developed by Minckler (1961).
Plan: Study the relevance of f (in Linacre 1969), the "sunshine factor" for each day of the growing season and plot it for each alpha unitin the area. Ecologists speak of sunlight as being the profound ecological factor but rarely include it as an independent factor in their analyses. Linacre(1969) suggested that monthly mean net radiation intensity can be computed readily from the factors in a GIS for each alpha unit.
Sample format:
| Stand Number | Area | Proportion of Area |
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| Full Sun | |||
| Partial Sun | |||
| Full Shade |
The Modified Simpson Index, expressive of the diversity of these conditions, is XXX. When the area is evenly distributed (equal in all three classes), the index has a value of 100.
The sunlight and moisture pairs are:
| Moisture Class | Full Sun Area % | Partial Sun Area % | Full Shade Area % |
| Dry | |||
| Moist (Mesic) | |||
| Wet |
General Notes
I have been taught in many ways and for a very long time that the sun drives ecosystems and that the sun is the primary source of energy in all natural systems. I accepted this; it made sense. As it turns out, it is an inoperable concept, almost meaningless. Nevertheless, it is a very complicated concept and thus must for most of us be overgeneralized, aggregated, and ... as I have done for over 25 years ... assumed it away as "reflected within all aspects of the ecosystem, the things observed." I now think it wrong to avoid the hard work of understanding the role of the sun in the ecosystem and the harder work of using it. I had an excuse before ... the difficulty of the computations required. That excuse passed when the computer became readily available. It passed in the mid-1950s. I have suboptimed ever since. I am in distinguished company.
The first realization is that "the sun" or "solar" is an overly large collection of concepts for the ecologist. It is a basket containing factors known to be influential, such as energy, cumulative energy spectrum, intensity range, duration and periods, and reradiation. It is especially relevant for "the growing period," a temperature-related phenomenon.Shadows are evidently also related.
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| Annual distribution of bright sunlight will eventually have to be estimated. Here is one suggested pattern. 1 May to Oct 30 is shown as heavy dots, 1 November to 30 April as light dots.Adapted from Hadfield 1974. |
It plays different roles in different systems and parts of systems. It is dangerous to worry about "double counting" it in ecosystems, for it is many factors though conspicuously from one source. I'll get back to the analyses in a paragraph or so, but it is worth noting the general outline of analysis. The sun influences the biosphere, hydrosphere, atmosphere, and lithosphere. I've treated its analysis under the atmosphere, but it is a profound example of function so dominant it is rightfully considered a part of each of the major spheres.
The distance of sun from Earth is 150 million km (93 million miles). This distance causes measures of the width of the noosphere to appear inconsequential. The ratio of __ x __-__; yet the dominance of the factor must not be minimized. It is an extra-Earth factor, convincing in deciding that open-systems theory is most relevant for dealing with (analyzing, modeling, and manipulating) ecological systems.
It is the largest heat source for Earth, the heat from the interior core (volcanoes, etc.) being only 0.02 percent of the total heat flux (Halverson and Smith 1979:1). It drives the biotic systems in its major role in photosynthesis. It influences atmospheric systems as well as rock fracturing and soil formation by temperature changes. Cloud dynamics are evidently effected by winds as well as direct heating. Of course animals are directly warmed but also cooled by wind-related convective heat losses. It is a powerful, broadly influential factor.
The relative quantun efficiency and relative action of photosynthesis for crop plants is within the 370-730 nm waveband (only 0.05 outside). A span of 220-686nm or 400-700nm can be used to define the limits of the photosynthetically active waveband (PAR). Stanhill and Fuchs (1977) found that for within the accuracy with which it can be measured, the PAR fraction, the proportion of global radiation, can be taken to be the constant of 0.5 for periods of 30 minutes or longer when the solar elevation is greater than 10 degrees. The constant is independent of atmospheric conditions.(There is low accuracy of sunlight measurement when the sun angle is less than 10 degrees.)
Net radiation (RN) from forests and orchards has been found well related to incoming shortwave solar radiation (RS) (Landsberg et al. (1973)):
RN = 0.666 RS - 14.7
The solar constant (energy impinging on the outer layer of the atmosphere) is 2 calories per minute per square centimeter of surface (normal to the solar beam). In reality, only 0.5 calories impinges. A heavy overcast permits only 18 units to reach Earth's surface, 70 on a clear day.
Q = 0.024 H (1 - 0.07C)
where Q = cal/sq.cm./m
H = altitude of sun
C = cloud cover in tenths
Managerial Control
Because influential, significant aspects of sunlight or solar radiation must be controlled by the land manager or else the system is merely being observed; the manager has no significant influence on the system. Since it is so profound and influential, any control gained is likely to be very important because of the interactions. In fact, a solar model is of great importance so that the effects of gaining sun control can be evaluated (a) to determine the gains per unit investment in such control and the marginal cost, and (b) to avoid discontinuities, thresholds, limits, and counterintuitive situations.
"Control" may be a peculiar word when used with the sun. Preposterous; control the sun! The manager can gain conceptual mastery of the solar influences, thus "control" in the sense of organizing it and understanding it. Not being surprised; risks reduced; a reduction of mental entropy ... control includes these along with comprehension. Control is exercised in deciding on where to make investments, and where to avoid them because of the sunlight available...or not.
The manager may also know that sunlight is influenced by particulate air pollution. This knowledge is a type of control, for it allows prediction of what various parts of the system will do (e.g., plants) when such particulates increase. To have knowledge about the dynamics of a system is to have a type of control over it.
"Arrangements or rearrangements of the spatial distribution of tree boles and crowns can prevent or allow solar radiation reaching any spot of ground. Thus, timber harvest and tree planting can be managed to change the amount of solar radiation reaching the surface. This change in solar radiation amount can be used to increase heat to snowpacks to create melt, to prevent thermal pollution in trout streams [see _________________________], and in other ways" (Halverson and Smith 1979:2).
To manipulate sunlight received (to create shadows or to use spectral filters) is evident control of light, of course not the sun. It includes operations in greenhouses and lathe houses, but especially (1) the cutting, shaping, and planting of trees to influence shadows, (2) shaping of land forms to achieve desired long-term shadows (Giles' work on seterrain 1985), (3) and building form and placement to influence shadows (as in protecting solar system users' rights to sunlight).
Perhaps the sun or sunlight cannot be manipulated but decisions can be made in selecting areas with the most advantageous sunlight. It can be" controlled" (in a statistical sense) for study of it as different amounts, sequences, and durations cause differences. Grace(1971) presented equations including that for the "Standard Overcast Sky" that allow a GIS to display hourly changes seasonally over an area of probable or likely brightness in a standard year. (A "moving picture" might result. The cumulative light in an alpha unit during a growing season will surely be a measure (e.g., an independent variable in a regression) that will allow adjustments that reduce the variance in ecological data sets from plots in different areas.
Objective
It is rare that a solar objective is stated. "To obtain __ hours of __ langleys of insulation in period A" may be stated, but usually solar radiation is a means to ends otherwise stated, such as "profits from wood growing" or "reduced loss of life from snow avalanches".
Analysis
Kaufman and Weatherred (1982) said the solar constant was 1.95 cal o cm-2 o min-1 (1360 W o M-2). Kerr (1986) reported this "constant" is now known to be decreasing at 0.018 percent per year (with confidence interval of + 0.0024 percent per year). These sound small, but in 10 years a 0.18 percent decrease in irradiance can probably produce significant effects. (A 1 percent decrease in irradiance from 1500 to 1850 could have produced the 1degree C cooling that was the Little Ice Age of Europe and other regions (Kerr 1986).
In previous work with the CAPS a table was created showing the hours of light throughout the year for a particular area. This was a lengthy table, unique for the latitude. The julian date is provided first, then eastern standard time, and daylight saving time equivalents for sunrise and sunset, then twilight. Day length is the hours from sunrise to sunset. Total hours for a year is then given. This needs to be repeated for select periods such as growing periods. It offers difference in hours of legal hunting or in viewing-related recreation in different hours. It may have a role in court cases in which visibility is in question. Hours of darkness may be useful for studying night as "cover" and for relating moon light in areas during periods of darkness.
References
Grace, J. 1971. The directional distribution of light in natural and controlled environment conditions. J. Appl. Ecol. 8(1):155-164.
Hadfield, W. 1974. Shade in North-East India tea plantations. J. Appl. Ecol. 11(1):151-177.
Landsberg, J.J. , D.B.B. Powell, and D.R. Butler. 1973. Microclimate in an apple orchard. J. Appl. Ecol. 10(3): 881-896.
Linacre, E.T. 1969. Net radiation to various surfaces. J. Appl. Ecol 6(1):61-75.
Smith, W.K., A.K. Kamp, and W.A. Reiners. 1989. Penumbral effects on sunlight penetration in plant communities. Ecology 70(6): 1603-1609.
Stanhill, G and M. Fuchs. 1977. The relative flux density of photosynthetically active radiation. J. Appl. Ecol 14:317-322.
Robert H. Giles, Jr., 2001
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Last revision July 20, 2001.