Spatial and temporal variation in the Bight environment of developing Scots pine stands: the basis for a quick and efficient method of characterizing Bight

1995 ◽  
Vol 25 (2) ◽  
pp. 343-354 ◽  
Author(s):  
Christian Messier ◽  
Pasi Puttonen
Keyword(s):  
Scots Pine ◽  
Efficient Method ◽  
Spatial And Temporal Variation ◽  
Photon Flux ◽  
Photon Flux Density ◽  
The Mean ◽  
Pine Stands ◽  
Sky Conditions ◽  
Overcast Sky ◽  
Scots Pine Stands

Spatial and temporal variations in photosynthetic photon flux density (PPFD) at 1 m above the forest floor were measured under and between dominant pines and in 21- to 52-m2 gaps under developing Scots pine (Pinussylvestris L.) stands in southern Finland. For each stand, PPFD data were collected continuously every 10-s and then averaged for every 5-min period during 4-6 days under completely clear and overcast sky conditions. Measurements were made during 102 consecutive days within two different areas in each of 10 different Scots pine stands ranging in age from 7 to 105 years. Mean daily percent PPFD in the understory varied from 7.5% in the 20-year-old stands to 38% in the 7-year-old stands, and did not differ significantly between completely clear and overcast sky conditions. Mean daily percent PPFD did not vary significantly between the different sensor locations within closed pine stands, indicating that at high latitudes mean daily percent PPFD does not vary much spatially under closed Scots pine forests. Measurements of PPFD made at different periods during the day under clear sky conditions, one of the main approaches used in the literature, were not representative of the whole-day conditions. Two different results suggest that PPFD can be better characterized under completely overcast sky conditions. First, the 5-min percent PPFD in the understory was fairly constant between 06:00 and 20:00 for all stand ages under completely overcast sky conditions. Second, there was an almost perfect 1:1 relationship of the mean daily percent PPFD measured at 40 different locations in the 10 stands between clear and overcast sky conditions. These two results suggest that an instantaneous measure of percent PPFD obtained under completely overcast sky conditions is representative of the mean daily percent PPFD for both sky conditions. These results provide the basis for a quick and efficient method of estimating the mean daily percent PPFD in the understory of closed forests.

A simple and efficient method to estimate microsite light availability under a forest canopy

1996 ◽  
Vol 26 (1) ◽  
pp. 151-154 ◽  
Author(s):  
Sylvain Parent ◽  
Christian Messier
Keyword(s):  
Efficient Method ◽  
Forest Canopy ◽  
Light Availability ◽  
Photosynthetic Photon Flux Density ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Broadleaf Forest ◽  
The Mean ◽  
Sky Conditions ◽  
Overcast Sky

This study presents a new, simple, and efficient method for estimating microsite light availability in the understory of a forest. The percentage of above-canopy photosynthetic photon flux density (%PPFD) transmitted above 16 microsites in the understory of a mixed conifer–broadleaf forest was measured every minute between 07:00 and 19:00 for both a completely overcast and a cloudless day. Instantaneous measures of %PPFD were also taken at different times on 3 overcast days. The instantaneous measures of %PPFD were strongly and directly related (P < 0.001) among themselves and with mean daily %PPFD values. These results demonstrate the usefulness of using an instantaneous measure of %PPFD taken under overcast sky conditions for estimating the mean daily %PPFD at any microsite under a forest canopy.

Photosynthetic photon flux density, red:far-red ratio, and minimum light requirement for survival of Gaultheriashallon in western red cedar–western hemlock stands in coastal British Columbia

1989 ◽  
Vol 19 (11) ◽  
pp. 1470-1477 ◽  
Author(s):  
Christian Messier ◽  
Terry W. Honer ◽  
James P. Kimmins
Keyword(s):  
Forest Floor ◽  
Photosynthetic Photon Flux Density ◽  
Western Hemlock ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Photosynthetic Photon Flux ◽  
Light Requirement ◽  
Red Cedar ◽  
Sky Conditions ◽  
Overcast Sky

Measurements of photosynthetic photon flux density (PPFD; global, diffuse, and direct: 400–700 nm) and red:far-red ratio (660:730 nm) were made above and below an understory of salal (Gaultheriashallon Pursh) within three western red cedar (Thujaplicata Donn)–western hemlock (Tsugaheterophylla (Raf.) Sarg.) stands on the northern end of Vancouver Island, British Columbia. These stands were chosen to represent a wide range of canopy closure and understory salal cover. The measurements were repeated under both clear and overcast sky conditions. Within each stand, the percent cover, height, number of stems per hectare, and leaf morphology of the salal were measured. As expected, there was a decrease in both the salal cover and in the global PPFD and red:far-red ratio measured directly above salal as the percent tree cover increased. Salal leaf thickness and specific leaf weight decreased, whereas its leaf area increased, as global PPFD and red:far-red ratio decreased. The results indicate that the minimum light requirement for salal survival is between 3.9 and 11.1 μmol•m−2•s−1 (1.2 to 3.3% of global PPFD measured in an adjacent clearing) and 4.5 and 27.2 μmol•m−2•s−1 (0.3 to 1.8% of global PPFD measured in the clearing) under overcast and clear sky conditions, respectively. The global PPFD and red:far-red ratio measured 30 cm above the forest floor (beneath the salal) did not vary widely among the three stands. At this level, global PPFD values were very low, ranging from 0.15 to 0.35% and 0.58 to 0.75% of the global PPFD measured in the clearing under clear and overcast sky conditions, respectively. Red:far-red ratios at the forest floor level varied from 0.13 to 0.25 and 0.40 to 0.58 under clear and overcast sky conditions, respectively. The silvicultural implications of the results are discussed.

Typology of the natural regeneration in a middle-aged Scots pine forest

1988 ◽  
Vol 53 ◽  
Author(s):  
C. De Schepper
Keyword(s):  
Scots Pine ◽  
Natural Regeneration ◽  
Free Field ◽  
Sandy Soils ◽  
Structural Basis ◽  
Pedunculate Oak ◽  
Pine Stands ◽  
Scots Pine Forest ◽  
Forest Practice ◽  
Scots Pine Stands

The  study describes the natural regeneration state of a forest on coarse sandy  soils. The natural regeneration was studied in three different ecological  conditions: in 30 to 60 year old Scots pine stands, in a 62 year old mixed  stand of pedunculate oak and red oak, and on the free field.     The analysis of the regeneration groups revealed that the first settler  maintained a dominant social position during the following years after the  settlement. The structural basis is consequently laid out early. This means  that the forest practice has to consider the very first phase of the  regeneration as determining for the following evolution of the regeneration  groups.

An analysis of a spontaneous ingrowth of deciduous trees in 70 year old stands of Scots pine

1987 ◽  
Vol 52 ◽  
Author(s):  
N. Lust
Keyword(s):  
Scots Pine ◽  
Red Oak ◽  
Deciduous Trees ◽  
Pedunculate Oak ◽  
Black Cherry ◽  
Height Distribution ◽  
Stem Number ◽  
Pine Stands ◽  
Spontaneous Regeneration ◽  
Scots Pine Stands

In 70  years old homogeneous Scots pine stands, bordered by a hardwood belt, an  analysis was made about the spontaneous ingrowth of natural seedlings. The  analysis involved especially the following points: species and stem number,  influence of the hardwood belts, diameter and height distribution, age,  growth and structure. From the age of 30 years, a spontaneous regeneration of  hardwoods established in Scots pine stands. There are on average 7,000 plants  per ha, 80 % of which are black cherry and another fair number are red oak  and pedunculate oak. The regeneration has an average age of 25 to 30 years,  it is uneven aged, contains several diameter and height classes and has  already partially penetrated the upper stratum.     The spontaneous ingrowth allows to convert in a simple way the homogeneous  coniferous stands into mixed hardwood stands.

scholarly journals Bayesian calibration, comparison and averaging of six forest models, using data from Scots pine stands across Europe

2013 ◽  
Vol 289 ◽  
pp. 255-268 ◽  
Author(s):  
M. van Oijen ◽  
C. Reyer ◽  
F.J. Bohn ◽  
D.R. Cameron ◽  
G. Deckmyn ◽  
...  
Keyword(s):  
Scots Pine ◽  
Bayesian Calibration ◽  
Forest Models ◽  
Pine Stands ◽  
Using Data ◽  
Scots Pine Stands

scholarly journals Estimation of Global and Diffuse Photosynthetic Photon Flux Density under Various Sky Conditions Using Ground-Based Whole-Sky Images

2019 ◽  
Vol 11 (8) ◽  
pp. 932
Author(s):  
Megumi Yamashita ◽  
Mitsunori Yoshimura
Keyword(s):  
Flux Density ◽  
Photosynthetic Photon Flux Density ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Diffuse Component ◽  
Photosynthetic Photon Flux ◽  
Physiological Processes ◽  
Sky Conditions ◽  
Mean Square Errors ◽  
Relative Root

A knowledge of photosynthetic photon flux density (PPFD: μmol m−2 s−1) is crucial for understanding plant physiological processes in photosynthesis. The diffuse component of the global PPFD on a short timescale is required for the accurate modeling of photosynthesis. However, because the PPFD is difficult to determine, it is generally estimated from incident solar radiation (SR: W m−2), which is routinely observed worldwide. To estimate the PPFD from the SR, photosynthetically active radiation (PAR: W m−2) is separated from the SR using the PAR fraction (PF; PAR/SR: unitless), and the PAR is then converted into the PPFD using the quanta-to-energy ratio (Q/E: μmol J−1). In this procedure, PF and Q/E are considered constant values; however, it was reported recently that PF and Q/E vary under different sky conditions. Moreover, the diffuse ratio (DR) is needed to distinguish the diffuse component in the global PAR, and it is known that the DR varies depending on sky conditions. Ground-based whole-sky images can be used for sky-condition monitoring, instead of human-eye interpretation. This study developed a methodology for estimating the global and diffuse PPFD using whole-sky images. Sky-condition factors were derived through whole-sky image processing, and the effects of these factors on the PF, the Q/E of global and diffuse PAR, and the DR were examined. We estimated the global and diffuse PPFD with instantaneous values using the sky-condition factors under various sky conditions, based on which the detailed effects of the sky-condition factors on PF, Q/E, and DR were clarified. The results of the PPFD estimations had small bias errors of approximately +0.3% and +3.8% and relative root mean square errors of approximately 27% and 20% for the global and diffuse PPFD, respectively.

scholarly journals Belowground biomass models for young oligotrophic Scots pine stands in Latvia

2018 ◽  
Vol 11 (2) ◽  
pp. 206-211 ◽  
Author(s):  
L Kenina ◽  
A Bardulis ◽  
R Matisons ◽  
R Kapostins ◽  
A Jansons
Keyword(s):  
Scots Pine ◽  
Belowground Biomass ◽  
Biomass Models ◽  
Pine Stands ◽  
Scots Pine Stands
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