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1.
The relationships between climatic variables and Scots pine (Pinus sylvestris L.) growth and needle dynamics were studied in three stands in Estonia and in four stands located near the northern timberline
in Lapland. The trees sampled in Estonia had low correlations with the analysed climatic variables (air temperature, precipitation
and indices of atmospheric circulation). Moreover, the weak cross-correlation of the time-series of the Estonian sample trees
indicated that Scots pine is affected mainly by local factors in that region. In Lapland, however, height increment and needle
production correlated strongly among trees within a stand (mean r=0.45 and 0.46, respectively) and between stands (r=0.32 and 0.37). Radial increment also showed a high inter-correlation among the trees within a stand in Lapland (r=0.45). Both height increment and needle production were strongly influenced by the temperature regime of the previous summer
in Lapland (mean r=0.64 and 0.64, respectively). Radial increment was correlated with the mean July temperature of the current year (mean r=0.29). The correlations between the indices of atmospheric circulation and tree attributes were weak, while the strongest
correlation was between the Ponta Delgada NAO index (PD–NAO) and height increment and needle production in Lapland. Height
increment, needle production and radial increment have increased since the 1990s in the trees growing in Lapland. This may
indicate a positive effect of climate warming on tree growth in Lapland. In Estonia, where climatic conditions do not limit
tree growth, the climate warming seems not to directly influence the growth and needle dynamics of Scots pine. 相似文献
2.
G. G. Suvorova M. V. Oskorbina L. D. Kopytova L. S. Yan’kova E. V. Popova 《Contemporary Problems of Ecology》2011,4(6):626-633
The paper studies the seasonal changes in photosynthetic activity and concentration of chlorophylls in the needles of the
Scots pine Pinus sylvestris L. and Siberian spruce Picea obovata Ledeb. depending on the environmental factors. In drought, the daily peaks of photosynthesis are regulated by the level of
moisture in the needles and concentration of chlorophylls. The work of chlorophyll is 2–6 times more effective with optimal
moistening than in drought. 相似文献
3.
Yu. V. Ivanov Yu. V. Savochkin Vl. V. Kuznetsov 《Russian Journal of Plant Physiology》2011,58(5):871-878
Effects of zinc (50–150 μM ZnSO4) on seed germinability, morphometric and physiological characteristics of Scots pine (Pinus sylvestris L.) seedlings during first 6 weeks of their development were studied. Scots pine turned out to be rather sensitive to elevated
zinc concentrations. This was manifested in reduced seed germinability, root system growth retardation and suppression of
its development (primarily, reduction in the size of the zone of secondary root formation, their number, and total length),
a disturbance in the dynamics of biomass accumulation by various organs, primarily true needles, and also the content of main
photosynthetic pigments. A specificity of zinc accumulation in seedling organs was established; it depended on the degree
of root system development. A competition between cotyledons and needles for essential elements was observed. It was concluded
that Scots pine high sensitivity to relatively low zinc concentrations (50–150 μM) makes it a more convenient model than currently
used model plants (Arabidopsis thaliana L., Mesembryanthemum crystallinum L., Brassica napus L., and others) for studying physiological and molecular mechanisms of conifers adaptation to heavy metals and also for predictions
of possible ecological consequences of environment pollution with zinc for tree phytocenoses. 相似文献
4.
Johan Kroon Tore Ericsson Gunnar Jansson Bengt Andersson 《Tree Genetics & Genomes》2011,7(6):1099-1111
We reviewed the genetic parameter estimates carried out from 1992 to 2006 for height increment in genetic tests of Norway
spruce and Scots pine, to describe patterns of genetic variation, heritability, and genetic correlations. The material included
seedling and clonal tests in Sweden, aged between 5 and 20 years. Multiple regression was used to explore relationships between
parameter values and test environments. Results showed moderate narrow-sense heritabilities ([^(h)]2 {\hat{h}^2} : mean =0.29 in Norway spruce; mean =0.23 in Scots pine) that decreased with test site latitude for both species. In Norway
spruce, [^(h)]2 {\hat{h}^2} increased with better growth and decreased with tree age, while for Scots pine, [^(h)]2 {\hat{h}^2} increased with tree age and southward transfer. The additive genetic coefficient of variation (; mean 15%), in Norway spruce, decreased with growth as well as site latitude. in Scots pine (mean =8.5%) increased with southward transfer and more southerly test latitude. Additive and genotypic within-site
genetic age-age correlations in Norway spruce were high, with mean r
A
and r
G
of 0.92 and 0.85, respectively. Corresponding across-sites estimates were on average lower. Genetic parameters were better
expressed on favorable sites, at younger ages in Norway spruce and at older ages in Scots pine. The results imply that gain
calculations should be based on different parameters in the two species. For maximizing genetic gain in the Swedish breeding
program, testing times could be shorter for Norway spruce than for Scots pine. The investigation showed a large variation
in parameter estimates from different field experiments, highlighting the importance of testing over multiple sites. 相似文献
5.
The objective of this study was to assess the familial aggregation of heart rate variability (HRV), a readily measurable noninvasive
reflection of cardiac autonomic function. Familial correlations were analyzed in 451 kibbutz members aged 15–97 years belonging
to 80 kindreds. Five-minute duration Holter recordings made during silent supine spontaneous breathing and metronomic breathing
were analyzed in the time and frequency domains. The present analysis considers the familial correlations and the heritability
estimates of two time-domain indices, the standard deviation (SD) of the R-R interval (RR), reflecting total variability,
and the root mean square of successive differences in RR intervals (RMSSD), reflecting vagal (parasympathetic) tone. During
free breathing, age- and sex-adjusted correlations between parents and their children (r=0.24 for both indices) and between adult siblings above 30 years of age (r=0.24 and r=0.34 for SD and RMSSD, respectively) were statistically significant, whereas spouse correlations (r=–0.04, r=–0.02 for SD and RMSSD, respectively) and correlations in younger siblings (r=–0.22 and r=0.01, respectively) were not. Significant heritability estimates were demonstrated for the two indices (h
2=0.41 for SD and h
2=0.39 for RMSSD). These findings suggest that familial aggregation of HRV characteristics is determined mostly by genetic
factors and less so by environmental factors and provide a basis for continuing the investigation into the underlying genetic
influences on HRV.
Received: 26 August 1997 / Accepted: 15 March 1998 相似文献
6.
Soil samples from a forest nursery growing Scots pine were collected at monthly intervals at five different depths during 1975 and examined for Paralongidorus maximus: 49% occurred at the 10–19 cm depth. The fluctuation in the numbers of the larval stages suggested that a complete life cycle from egg to adult probably took more than 1 yr. Growth in the second year after planting and overall height of Scots pine seedlings was inversely related to the numbers of P. maximus. In a glasshouse experiment using varying numbers of P. maximus the growth of Scots pine and European larch but not of Sitka spruce were decreased by increasing numbers of nematodes. A possible relationship between P. maximus, Cylindro-carpon destructans and the death of small numbers of Scots pine is discussed. 相似文献
7.
Photosynthetic CO2 uptake, the photochemical efficiency of photosystem II, the contents of chlorophyll and chlorophyll-binding proteins, and
the degree of frost hardiness were determined in three-year-old Scots pine (Pinus sylvestris L.) trees growing in the open air but under controlled daylength. The following conditions were compared: 9-h light period
(short day), 16-h light period (long day), and natural daylength. Irrespective of induction by short-day photoperiods or by
subfreezing temperatures, frost hardening of the trees was accompanied by a long-lasting pronounced decrease in the photosynthetic
rates of one-year-old needles. Under moderate winter conditions, trees adapted to a long-day photoperiod, assimilated CO2 with higher rates than the short-day-treated trees. In the absence of strong frost, photochemical efficiency was lower under
short-day conditions than under a long-day photoperiod. Under the impact of strong frost, photochemical efficiency was strongly
inhibited in both sets of plants. The reduction in photosynthetic performance during winter was accompanied by a pronounced
decrease in the content of chlorophyll and of several chlorophyll-binding proteins [light-harvesting complex (LHC)IIb, LHC
Ib, and a chlorophyll-binding protein with MW 43 kDa (CP 43)]. This observed seasonal decrease in photosynthetic pigments
and in pigment-binding proteins was irrespective of the degree of frost hardiness and was apparantly under the control of
the length of the daily photoperiod. Under a constant 9-h daily photoperiod the chlorophyll content of the needles was considerably
lower than under long-day conditions. Transfer of the trees from short-day to long-day conditions resulted in a significantly
increased chlorophyll content, whereas the chlorophyll content decreased when trees were transferred from a long-day to a
short-day photoperiod. The observed changes in photosynthetic pigments and pigment-binding proteins in Scots pine needles
are interpreted as a reduction in the number of photosynthetic units induced by shortening of the daily light period during
autumn. This results in a reduction in the absorbing capacity during the frost-hardened state.
Received: 3 March 1997 / Accepted: 16 July 1997 相似文献
8.
Jukka Sakari Pumpanen Jussi Heinonsalo Terhi Rasilo Kaj-Roger Hurme Hannu Ilvesniemi 《Trees - Structure and Function》2009,23(3):611-621
Carbon dioxide is released from the soil to the atmosphere in heterotrophic respiration when the dead organic matter is used
for substrates for soil micro-organisms and soil animals. Respiration of roots and mycorrhiza is another major source of carbon
dioxide in soil CO2 efflux. The partitioning of these two fluxes is essential for understanding the carbon balance of forest ecosystems and for
modelling the carbon cycle within these ecosystems. In this study, we determined the carbon balance of three common tree species
in boreal forest zone, Scots pine, Norway spruce, and Silver birch with gas exchange measurements conducted in laboratory
in controlled temperature and light conditions. We also studied the allocation pattern of assimilated carbon with 14C pulse labelling experiment. The photosynthetic light responses of the tree species were substantially different. The maximum
photosynthetic capacity (P
max) was 2.21 μg CO2 s−1 g−1 in Scots pine, 1.22 μg CO2 s−1 g−1 in Norway spruce and 3.01 μg CO2 s−1 g−1 in Silver birch seedlings. According to the pulse labelling experiments, 43–75% of the assimilated carbon remained in the
aboveground parts of the seedlings. The amount of carbon allocated to root and rhizosphere respiration was about 9–26%, and
the amount of carbon allocated to root and ectomycorrhizal biomass about 13–21% of the total assimilated CO2. The 14CO2 pulse reached the root system within few hours after the labelling and most of the pulse had passed the root system after
48 h. The transport rate of carbon from shoot to roots was fastest in Silver birch seedlings. 相似文献
9.
HPLC chromatographic analyses of some phenolic acids in phloem of 1-year-old shoots sampled from 32 trees of eight Polish
provenances of Scots pine (Pinus sylvestris L.) growing under conditions of annosum root [Heterobasidion annosum (Fr.) Bref.] are discussed. Considerable quantitative and qualitative differentiation was found among individual trees. The
variability of trees was estimated with regard to the level of phenolic acids and correlations were established in order to
assess the character of their joint occurrence in shoot phloem. In view of pathogen presence, the content of phenolic acids
varies between individuals depending upon the genotype of pine, the stage of development of the disease and upon the effect
of tree growth conditions.
Received: 23 April 1997 / Accepted: 12 September 1997 相似文献
10.
Novikov I Kalter-Leibovici O Chetrit A Stav N Epstein Y 《International journal of biometeorology》2012,56(1):121-127
Global climate changes affect health and present new challenges to healthcare systems. The aim of the present study was to
analyze the pattern of visits to the medical wing of emergency rooms (ERs) in public hospitals during warm seasons, and to
develop a predictive model that will forecast the number of visits to ERs 2 days ahead. Data on daily visits to the ERs of
the four largest medical centers in the Tel-Aviv metropolitan area during the warm months of the year (April–October, 2001–2004),
the corresponding daily meteorological data, daily electrical power consumption (a surrogate marker for air-conditioning),
air-pollution parameters, and calendar information were obtained and used in the analyses. The predictive model employed a
time series analysis with transitional Poisson regression. The concise multivariable model was highly accurate (r
2 = 0.819). The contribution of mean daily temperature was small but significant: an increase of 1°C in ambient temperature
was associated with a 1.47% increase in the number of ER visits (P < 0.001). An increase in electrical power consumption significantly attenuated the effect of weather conditions on ER visits
by 4% per 1,000 MWh (P < 0.001). Higher daily mean SO2 concentrations were associated with a greater number of ER visits (1% per 1 ppb increment; P = 0.017). Calendar data were the main predictors of ER visits (r
2 = 0.794). The predictive model was highly accurate in forecasting the number of visits to ERs 2 days ahead. The marginal
effect of temperature on the number of ER visits can be attributed to behavioral adaptations, including the use of air-conditioning. 相似文献
11.
J. Oleksyn P.B. Reich L. Rachwal M.G. Tjoelker P. Karolewski 《Trees - Structure and Function》2000,14(7):415-421
On range-wide and regional scales, climate and site factors exert control over tree growth, masking the genetic basis of biomass
accumulation and allocation. To determine intrinsic population differences in productivity, aboveground net primary production
(ANPP) was measured in 16-year-old Scots pine from 19 geographically distinct populations grown in a common garden experiment
in central Poland (52°N). The populations originated from the northern (>55°N), central (54–47°N), and southern (<45°N) European
range of Scots pine. We calculated ANPP from aboveground growth components, using diameter-based allometric equations developed
for this site. Average foliage, aboveground woody and total ANPP differed significantly among populations and were greater
for central European populations than for the southern and northern ones. Stocking and total ANPP per tree were positively
correlated to stand aboveground biomass (r
2≥0.71). The relationship between the latitude of seed origin and ANPP was curvilinear and maximum for populations originating
near the planting site (52°N). ANPP declined in populations with increasing longitude eastward from the Atlantic Ocean towards
the center of the continent. This study underscores the potentially large genetic control of ANPP and biomass accumulation
among diverse Scots pine populations.
Received: 3 January 2000 / Accepted: 29 March 2000 相似文献
12.
Bohdan Konôpka Jorge Curiel Yuste Ivan A. Janssens Reinhart Ceulemans 《Plant and Soil》2005,276(1-2):33-45
In this study, we investigated the relationship between the seasonality of vegetation cover and that of fine root processes
in a man-made forest in northern Belgium. Due to their contrasting foliar development, we expected different seasonal patterns
of fine root growth and standing biomass between Pedunculate oak (Quercus robur L.), and Scots pine (Pinus sylvestris L.). Biomass and necromass of fine and small roots were estimated by repeated core sampling in February, April, June, August
and October 2003. Measurements showed that Pedunculate oaks maintained more live fine roots in winter than Scots pines. However,
Scots pines produced more than twice as much fine roots in spring, such that in summer both species had similar root mass.
Scots pine root production started before-, but declined during leaf unfolding. Pedunculate oak roots, in contrast, started
elongating only after bud break. For both species, fine root production peaked in JuneJuly, but was more than offset by drought-induced
mortality at the end of July and early August. Summer drought in 2003 was exceptionally long and intense, significantly reducing
leaf area, killing most new roots, and inhibiting root decomposition, such that the obtained results cannot be typical for
this forest. 相似文献
13.
Nucleotide variation at several cold candidate genes including seven members of the dehydrin gene family was surveyed in haplotypes
of Scots pine (Pinus sylvestris) sampled in populations showing divergence for cold tolerance in Europe. Patterns of nucleotide diversity, linkage disequilibrium,
and frequency spectrum of alleles were compared between north and south populations to search for signs of directional selection
potentially underlying adaptation to cold. Significant differentiation between populations in allelic frequency or haplotype
structure was detected at dhn1, dhn3, and abaH loci. Allelic dimorphism with no evidence of haplotype clustering by geographical distribution was found at dhn9. An excess of fixed non-synonymous mutations as compared to the outgroup P. pinaster pine species was found at dhn1. Differences in nucleotide polymorphisms were found between the members of the Kn class of dehydrin upregulated during cold
acclimation (average πsil = 0.004) as compared to the SKn class (average πsil = 0.024). The multilocus nucleotide diversity at silent sites (θ
W = 0.009) was moderate compared to other conifer species, but higher than previous estimates for Scots pine. There was an
excess of rare and high frequency derived variants as revealed by significantly negative multilocus value of Tajima’s D (D = −0.72, P < 0.01) and negative mean value of Fay and Wu H statistics (H = −0.50). The level of linkage disequilibrium decayed rapidly with an average expected r
2 of 0.2 at about 200 bp. Overall, there was a positive correlation between polymorphism and divergence at ten loci when outgroup
sequence was available. The discovered polymorphism will be used for further evaluation of the adaptive role of genes through
association mapping studies.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
14.
Vincenzo Saggiomo Immacolata Santarpia Maria Saggiomo Francesca Margiotta Olga Mangoni 《Polar Biology》2011,34(9):1255-1267
During the late austral summer and early autumn 1995 (March–April), an oceanographic cruise was conducted along the Strait
of Magellan in order to study the photosynthetic performance of phytoplankton assemblages. The high correlations between the
pico–nano fractions and both the total biomass concentrations (Chla) and primary production rates emphasized the role of these fractions in driving the primary production processes. Repeated
P versus E experiments were conducted in the most productive area of the Strait, Paso Ancho, in order to assess the influence of the
tidal currents on phytoplankton photosynthetic performance. These data were compared to those available from a previous cruise
(February–March, 1991) carried out along the Strait. In the Pacific–Andean sector, the primary production processes were highly
controlled by wind, land forcing, and irradiance availability. In the Paso Ancho, the observed highest photosynthetic capacity
P\textm\textB P_{\text{m}}^{\text{B}} (up to 6.5 mgC mgChla
−1 h−1) and the high primary production rates may due to the continuous mixing of the water column forced by the strong tidal currents
within the photic layer. The non-limiting, macro-nutrient concentrations in the Strait indicate that the available irradiance
and the depth of mixed layer are the main driving factors of the primary production processes. The photosynthetic performance
of the phytoplankton assemblages renders the Strait a unique ecosystem, which is more similar to those of the mid-latitudes
than to those of the periantarctic areas. 相似文献
15.
Tim J. Jones Corene D. Luton Louis S. Santiago Guillermo Goldstein 《Trees - Structure and Function》2010,24(3):471-478
The relationship between water transport and photosynthesis represents the trade-off between carbon gain and water loss and
was used to evaluate potential differences in water resource utilization among two dominant vegetation types of south Florida:
subtropical evergreen broad leaf forests (hardwood hammocks) and pine woodlands (pine rocklands). We found consistent linear
positive relationships between the quantum yield of photosystem II (ϕ
PSII), an index of photosynthetic capacity, and hydraulic conductivity per sapwood area (k
S) and per leaf area (k
L) across all species. The slope of the ϕ
PSII–k
S relationship was steeper for hardwood hammock than for pine rockland species. Mean ϕ
PSII was greater in pine rockland species and was greater for a given k
L than in hardwood hammock species. These results are consistent with previous observations demonstrating that pine rocklands
tend to have better access to stable water sources than hardwood hammocks. We also found greater photosynthetic carbon isotope
discrimination with increasing k
S and k
L in pine rockland species, but not in hardwood hammock species, suggesting increased stomatal conductance with increasing
k
S and k
L, consistent with greater water availability in pine rockland habitats. Our study thus utilizes relationships between water
transport and photosynthesis to evaluate hydraulic constraints on physiological function between two contrasting vegetation
types with contrasting stability of water sources. 相似文献
16.
J. Baar 《Mycorrhiza》1997,7(2):89-94
The effect on ectomycorrhizal root growth in a nitrogen-enriched planted stand of Scots pine (Pinus sylvestris L.) on podzolic sandy soil to manipulation of litter and humus layers (removal, doubling and control treatments) was examined,
and compared to ectomycorrhizal root growth in an untreated naturally established Scots pine stand on nutrient-poor non-podzolic
sandy soil. Half a year after manipulation of litter and humus layers in the planted stand, ingrowth-cores to a depth of 60 cm
were installed in both stands. Scots pine roots were sampled four times during two growing seasons. Ectomycorrhizal roots
were found at all sampled soil depths to 60 cm in all plots. Root growth and ectomycorrhizal development were greater in the
naturally established stand than in all plots in the planted stand. Numbers of ectomycorrhizal root tips in the litter and
humus removal plots were generally higher than in the control plots in the planted stand until May 1992. Doubling litter and
humus did not significantly affect root length or the numbers of ectomycorrhizal root tips. The N
dissolved
, NH4
+ and NO3
– concentrations and the organic matter content in the upper 5 cm of the mineral soil in the planted stand on podzolic sandy
soil were generally higher and the pH significantly lower than in the naturally established stand on non-podzolic sandy soil.
Root growth and ectomycorrhizal development in the secondary stand may have been negatively affected by the chemical composition
of the podzolic sandy soil.
Accepted: 19 March 1997 相似文献
17.
Annual height increments of 35 Scots pine (Pinus sylvestris L.) trees from the northern timberline (68°30′N, 27°30′E, 220 m a.s.l., Laanila, North Finland) and monthly climate data from two meteorological stations, Sodankylä (from 1908 to present) and Ivalo (from 1958 to present) were used in climate and growth comparisons. The measured growth series were standardized using 67% splines. A height-increment chronology was built by averaging the indices. This chronology was further divided into high- and low-frequency components using reciprocal filters. Among the temperature variables, mean July temperature of the previous year correlated most significantly with height growth. We compared several simple linear reconstruction models based on the three height-growth chronologies (the unfiltered, high-pass and low-pass filtered chronologies) individually as predictors of the mean July temperature. The high-frequency reconstruction showed superior model performance in calibrations. However, only calibrations using climate data from the nearest Ivalo station were time stable and showed reasonable reconstruction skill. The coefficient of determination (R2) in the final model during calibration period (1958–1998) is 0.67. 相似文献
18.
The recent warming trend, and associated shifts in growing season length, challenge the principle of uniformitarianism, i.e., that current relations are persistent over time, and complicates the uncritical inferences of past climate from tree-ring data. Here we conduct a comparison between tree-ring width chronologies of Pinus sylvestris L. (Scots pine), Picea abies (L.) Karst. (Norway spruce) and Betula pubescens Ehrh. (Downy birch) and phenological observations (budburst and leaf senescence) of Fagus sylvatica L. (European beech), Quercus robur L. (European oak), Betula sp. (Birch), Norway spruce and Scots pine) in Sweden to assess to what extent the tree-ring width–temperature relationship and the timing of phenological phases are affected by increased temperature. Daily meteorological observations confirm a prolongation of the thermal growing season, most consistently observed as an earlier onset of around 1–2 weeks since the beginning of the 20th century. Observations of budburst closely mimic this pattern, with budburst of the deciduous trees occurring 1–2.5 weeks earlier. In contrast to the changes seen in phenology and observational temperature data, the tree-ring width–temperature relationships remain surprisingly stable throughout the 20th century. Norway spruce, Scots pine and Downy birch all show consistently significant correlations with at least one 30 day-long window of temperature starting in late June–early July season. Norway spruce displays the largest degree of stability, with a consistent 60 day-long temperature window with significant correlation starting around Julian calendar day 150. Thus, our results suggest that the principle of uniformitarianism is not violated during the period covered by modern meteorological observations. Further research is needed to determine at what thresholds the temperature sensitivity of these species may alter or deteriorate as a consequence of the ongoing climate change. 相似文献
19.
To clarify the potential use of hydrophobicity-related traits of aerial conidia in formulation design of fungal biocontrol
agents, hydrophobicity rates (H
r) and surface areas (S
a) of aerial conidia were assessed with 48 strains of Beauveria bassiana,
Isaria fumosorosea and Metarhizium spp. Inter- or intra-specific variation was large in H
r (59.7–92.2%) and S
a (7.9–25.3 μm2 conidium−1) measurements, which were significantly correlated (r
2 = 0.55). Six isolates of the three fungi with distinguished H
r and S
a were further studied. Conidial wall proteins of these isolates were sequentially extracted with sodium dodecyl sulfate (SDS),
formic acid (FA) and trifluoroacetic acid (TFA). Their H
r values were significantly correlated to the contents (P
c) of TFA-soluble, but FA-insoluble, proteins (2.7–44.8 μg per 107 conidia; r
2 = 0.79) and reduced drastically by the FA/TFA treatments, which eliminated the hydrophobin-based rodlet layers of conidial
surfaces. However, the SDS treatments had no effect on either H
r or rodlet layers. The dispersancy of a tested emulsifier to oil formulations of the six isolates in water was adversely correlated
to their H
r (r
2 = 0.94). The results indicate that both P
c and S
a are inherent hydrophobicity-related traits and can be utilized to select fungal biocontrol candidates for improved formulation
and application. 相似文献
20.
Microsite variation in light availability and seedling growth ofQuercus serrata in a temperate pine forest 总被引:1,自引:0,他引:1
Spatial heterogeneity in light availability for tree seedlings under the canopy of a temperate pine forest was studied. Six-day
measurements at 10-s intervals revealed a great variety in the temporal patterns of photosynthetic photon flux density (PPFD)
and histograms among observation days and microsites; mean daily total PPFD relative to full sun varied from 1.5% to 10.4%
depending on the microsites. The occurrence and duration of PPFD above 80 μmol m−2 s−1, which might reflect sunfleck activity, varied greatly among the microsites. However, several simple empirical relationships
were found between some parameters characterizing microsite light availability and sunfleck activity; the diffuse site factor
was correlated well with other parameters, including daily total PPFD, daily totals and daily summed durations of high PPFD
above any examined threshold level, and its contribution to daily total PPFD. Diffuse site factors which were obtained for
700 microsites within an area of 28 m2 on three different occasions during the growing season showed high correlations within the microsite. Based on the regressed
relationship between the relative growth rate of current-year seedlings ofQuercus serrata and the microsite diffuse site factor and the results of area-survey measurement of the diffuse site factor, an estimation
was made of the abundance of potential ‘safe-sites’ for seedling growth of the species; the ‘safe sites’ were estimated to
cover 40% and 0% of the total area of the sunny and shady sites of the forest, respectively. 相似文献