Diffuse Site Factor Research Articles

Growth Characteristics of <i>Quercus serrata</i> and <i>Quercus glauca</i> Seedlings in a Restored Urban Forest After Approximately 20 Years Since Construction

To clarify the regeneration processes of two Quercus (Fagaceae) species, Quercus serrata, deciduous broad-leaved tree and Quercus glauca, evergreen broad-leaved tree in an urban forest, 163 research quadrats (163 m2) on the forest floor in a restored deciduous broad-leaved forest, "Inochi- No-Mori" in Kyoto city after approximately 20 years since construction were set up. Growth characteristics, recruitment, mortality and relative height growth rates of seedlings of these two species were investigated. As a result, the recruitment rate of Q. serrata seedlings tends to be higher than that of Q. glauca seedlings, when diffuse site factor was larger than 15.0%, particularly. The relative height growth rate of Q. serrata seedlings in the 15–50-cm height class was relatively high when diffuse site factor was larger than 15.0%. On the other hand, the mortality rate of Q. glauca seedlings in the 15–50-cm height class was very lower than that of Q. serrata seedlings. These results indicate that in order to promote the regeneration of Q. serrata in this site, it is necessary to maintain a light environment with a diffuse site factor amount of larger than 15.0% around the mature Q. serrata trees, by thinning the upper trees and to selectively remove Q. glauca seedlings.

Phorophyte specificity and environmental parameters versus stochasticity as determinants for species composition of corticolous crustose lichen communities in the Atlantic rain forest of northeastern Brazil

A transect of 47 mature trees was studied within an Atlantic rain-forest plot in northeastern Brazil to determinate effects of phorophyte specificity and environmental parameters vs. stochasticity on the structure of corticolous, crustose microlichen communities. A total of 150 lichen species was found, most being rare to extremely rare. Multivariate analysis of sample plots indicated subtle phorophyte preferences among certain lichen species, corresponding to differences in bark pH, degree of bark shedding, density and size of bark lenticels, and presence of milk sap. Individual and multiple regressions revealed correlations between lichen species richness; respectively, area cover and bark pH (negative); density and size of bark lenticels (negative); degree of bark shedding (negative); presence of milk sap (positive); and diffuse site factor (positive). No strongly delimited lichen communities were detected, but cluster analysis revealed three main groups and six subgroups with slightly different lichen species composition, each one with characteristic indicator species but with highly variable overall species composition. Beta diversity was high among samples and lacked spatial structure. However, beta diversity was significantly lower among samples belonging to the same tree species, independent of their spatial arrangement. It was concluded that community formation in tropical rain-forest understory lichens subtly correlates with two main environmental factor complexes—phorophyte bark characteristics and microclimate—but is to a large extent determined by the stochastic effects of species dispersal, especially of rare species.

Genetic diversity, spatial patterns, and growth of root sprouts in a temperate tree at the northern distribution limit

In many plant species, population persistence at the limit of their distribution relies on clonal growth, but little is known about the consequences for genetic diversity, spatial patterns, and growth of the offspring. The rare European tree Sorbus torminalis (Rosaceae) was chosen to explore the patterns and limitations of clonal growth. Offspring were mapped in 7 small populations at the northern limit of the species' distribution, their size was recorded in 2 consecutive years, and the degree of shading (diffuse site factor, DSF) was measured at the forest floor. A subsample of offspring and adults was genotyped with microsatellites to determine the frequency of vegetative reproduction, and another group of offspring was protected against browsing. Clonal origin was observed in 98% of the offspring, and thus they were classified as root sprouts. The fine-scale distribution of the root sprouts was mainly clumped, and variation of DSF explained some of this pattern. Mixed linear modeling of root sprout size, with DSF, sprout density, and distance to the nearest adult tree as explanatory variables, suggested inter-offspring competition, but there were significant interactions among the explanatory variables, In addition, browsing by deer reduced growth of the root sprouts. Root sprout mortality was 17% after 1 y, and highest for young, small, and isolated offspring growing in high-light microhabitats. Root sprout growth and mortality were not directly affected by distance to adult trees. We conclude that clonal growth is common in the northern populations of the study species, and that root sprout distribution and growth are controlled by complex interactions between light, browsing, distance to the parent tree, and sprout density.

Method of segmentation affects leaf inclination angle estimation in hemispherical photography

This paper deals with the issue of segmentation methods in hemispherical photography determining diffuse site factor (DIFFSF) and leaf inclination angle distribution in forest stands simultaneously. Field inclination angle distributions were sampled in pure stands of European beech, hornbeam, sessile oak and silver birch on sites where towers facilitated crown access. In the same stands leaf litter traps were placed from which LAI values were derived after autumn leaf fall. Analogue hemispherical photographs were taken in summer before leaf fall. We combined the ellipsoidal G-function and Markov–Poisson model to invert leaf inclination angle functions (LIDF). Field leaf inclination angle distributions were planophile for three species and plagiophile for birch. The planophile distributions were well represented by ellipsoidal as well as beta distribution while plagiophile distribution of birch was exclusively represented by beta distribution. When segmentation methods were varied, LIDF parameter predictions were more in correspondence with field values by using sub-pixel methods than by using binary methods. When integrating vignetting properties into the segmentation algorithm or when accounting for standard sky luminance distribution, the accuracy of LIDF predictions varied; it is assumed that this is due to variation in sky properties during photography. Thus, different segmentation techniques in hemispherical photography did not yield constancy in deriving different required variables, i.e. DIFFSF and LIDF. Rather, method of segmentation affects leaf inclination angle estimation.

Recruitment of fleshy‐fruited species under different shrub species: Control by under‐canopy environment

Seedling densities and the mortality of fleshy‐fruited species under 10 European tall‐shrub species and the tree Sorbus aria were analyzed in 10‐year‐old experimental scrub for one growing season. The mean total densities of seedlings of 18 fleshy‐fruited species differed under the different ‘hosts’, being highest under Crataegus monogyna, Viburnum opulus and Rosa canina (24–20 m−2); intermediate under Sorbus aria, Rhamnus catharticus, Cornus sanguinea, Ligustrum vulgare and Juniperus communis (17–12 m−2); and lowest under Euonymus europaeus, Viburnum lantana and Prunus spinosa (10–9 m−2). This ranking was similar for the 11 planted species and for nine bird‐dispersed, non‐planted species which invaded the site, notably Hedera helix and Solanum dulcamara. Within the experimental scrub as a whole mortality of seedlings differed significantly among species, being highest in those with the smallest number of recruits. Mortality ranged from 94% and 89% for Solanum dulcamara and Viburnum opulus to 26% for Hedera helix and Ligustrum vulgare. The mean mortality across all species of seedlings did not differ significantly between host species, although it was slightly higher under Juniperus and Cornus (56%, 53%) and lower under Viburnum lantana and Rhamnus (42%, 41%). In four species, the mortality of seedlings was significantly higher under conspecific adults. Mean topsoil water content after a dry spell was negatively correlated with the diffuse site factor (DSF). The mean density of accumulated seedlings of the most abundant seedling species (Hedera) was positively correlated with the topsoil water content. Densities of other species showed no strong correlations with either topsoil water content or DSF. The probable factors controlling recruitment are discussed.

Relations between the invasive Cinnamomum verum and the endemic Phoenicophorium borsigianum on Mané island, Seychelles

Abstract. In the Seychelles the endemic palm Phoenicophorium borsigianum and the aggressively invasive alien Cinnamomum verum are competitors in a series of habitats. The extent to which demographic variables (relative growth rates of leaf area (RGRAL) and height (RGRR) together with mortality and recruitment) were important determinants of the competitive ability of the above species was investigated.It was studied whether competitive relations between Cinnamomum and Phoenicophorium can change with light intensity as a result of different morphological responses and to what extent native plants such as Phoenicophorium can establish, regenerate and potentially outcompete Cinnamomum in important biodiversity sites in mountain mist forest and intermediate forest habitats. The light intensity in terms of diffuse site factors (DifSF) was estimated at 32 microsites from hemispherical photographs using a computerized image analysis system. A new plant growth analysis function, the so‐called leaf area height index (ALHI), has been introduced and a principal components analysis (PCA) was carried out to evaluate the seedling performance of Cinnamomum and Phoenicophorium. Competition between Cinnamomum and Phoenicophorium was greatly influenced by the amount of available photosynthetically active radiation (PAR). For both species there was a negative correlation between mean leaf area of seedlings and light levels. Phoenicophorium responded significantly better in terms of RGRAL and ALHI to low gap light levels than Cinnamomum. Both species showed no further response to direct sunlight with levels of 98.7 % diffuse site factor. Phoenicophorium and probably other palms endemic to the Seychelles such as Deckenia nobilis and Roscheria melanochaetes act as a filter affecting the distribution and abundance of establishing Cinnamomum seedlings. Mortality of Cinnamomum was strongly negatively correlated with levels of PAR while Phoenicophorium showed no such correlation. Unlike Phoenicophorium, Cinnamomum could establish and regenerate only in light levels of >7.5 % diffuse site factor.

Difference in Diffuse Site Factors Due to Spatial Distribution of Sky Luminance

Difference in Diffuse Site Factors Due to Spatial Distribution of Sky Luminance

Effects of potential PAR on shoot extension in juveniles of the main tree species in a Japanese temperate forest

We studied the relationship between potential photosynthetically active radiation (PAR), estimated from hemispherical photographs, and shoot extension rates of juveniles of 12 seral tree species. We distinguished between direct light site factor (DIR), diffuse light site factor (DIF), and gap light index (GLI). We used a log‐linear model to relate growth to DIR, DIF and GLI. Potential PAR explained shoot growth rates significantly in 33 cases out of 36 (12 species × 3 PAR). DIF explained the shoot extension rates better than DIR and GLI for 10 of the 12 species. The mean values of maximum shoot extension rates of the tolerant, the intermediate and the intolerant species were 52.4 cm year–1, 64.3 cm year–1 and 87.7 cm year–1, respectively. The maximum shoot extension rates of the tolerant and the intolerant species were recorded in about 50% DIF and more than 70% DIF, respectively. The minimum light level for seedling establishment of the intermediate and intolerant species was more than 20% DIF. We explained distribution characteristics and shoot extension of the species in relation to light in terms of shade tolerance. Predictions based on light‐growth curves and maximum growth curves were similar to field observations made elsewhere, suggesting that these models may be useful to predict extension growth of juvenile trees in mixed species stands.

Calibration of grey values of hemispherical photographs for image analysis

The hemispherical photography method is widely used for the estimation of solar radiation in forests or agricultural crops. However, calibration problems repeatedly arise concerning the grey-value information of the photographs. This article introduces a method which may help to solve these calibration problems. The method takes into consideration two information transport media (black-and-white film and digital image analysis). This method is based on the exposure of the photographs to the zenith luminance of an overcast sky and the determination of the gamma function of the film by means of an optical density wedge photograph. By taking these characteristics into account, it is possible to obtain reproducible and bias-free results from the diffuse site factor even with different film materials. Moreover, the modelling of penumbral effects is shown. Limitations are discussed.

Spatial distribution patterns of two predominant emergent trees in a tropical rainforest in Sarawak, Malaysia

Spatial distribution patterns of two emergent tropical rainforest tree species (Dryobalanops aromatica & D. lanceolata) were examined in where they were dominant (17–20% of total basal area of canopy trees) in Sarawak, East Malaysia. Newly established seedlings (< 2 years old) were restricted to areas < 40 m from mother trees for both species, suggesting a limited seed dispersal. Seedling (< 1 cm in dbh) density was highest around conspecific adults (≥ 30 cm in dbh). Negative spatial patterns were observed between larger juveniles (1–5 cm in dbh) and conspecific adults for both species; the most dense populations of sapling (1–5 cm in dbh) and poles (5–30 cm in dbh) were found at a distance of 15–20 m from the nearest conspecific adult. Seedlings of both species were distributed randomly with respect to light conditions evaluated by a forest floor diffuse site factor and a canopy closure index. Saplings of both species, and poles of D. lanceolata, were distributed under more open conditions than expected from spatially random distributions, and from average light conditions of all species of the same size classes. Possible mechanisms for the observed distribution patterns and intermediate canopy dominance of Dryobalanops were discussed from the viewpoints of gap-dynamics and distance-dependent mortality.

Spatial and seasonal patterns of microsite light availability in a remnant fragment of deciduous riparian forest and their implication in the conservation ofArisaema heterophyllum, a threatened plant species

Seasonal and spatial patterns of light availability were investigated in the understory of a small fragment (approximately 1300 m2) of a riparian deciduous forest of the Kokai River in central Japan dominated byQuercus acutissima Carruth., with the aim to understand the characteristics of microsite light availability forArisaema heterophyllum Blume, a threatened plant species uniquely associated with the riparian habitat. Diffuse site factor, which is the ratio of PFD (photon flux density, 400–700 nm) at a microsite to the open sky reference under diffuse light condition, was shown to be a satisfactory index for the evaluation of light availability for the understory plants in the habitat. Diffuse site factor 1,0 1,000 understory microsites along a 20 m transect from the edge to the interior of the forest, showed conspicuous seasonal changes in both mean and variation. Light availability decreased with seasonal tree canopy regeneration, with the highest spatial heterogeneity being recorded during the time of canopy closure. Auto-correlations of microsite light availability between different seasons were considerably high, suggesting the stability of relative light availability for individual microsites throughout the growing season ofA. heterophyllum. Fairly high light availability during summer season, which surpassed 20% of the open sky reference in most microsites, would be important for the growth and persistence of summer herbaceous plants likeA. heterophyllum.

Effects of light availability and tree size on the architecture of assimilative surface in the canopy of Picea abies: variation in needle morphology.

Needle dimensions, needle surface area, needle dry weight per area (LWA) and needle density (ND, needle weight per volume) were measured in terminal current-year shoots in a natural canopy of variably sized Picea abies (L.) Karst. trees growing along a light gradient. Needle shape was described as a rhomboid. Needle width (D(2)) increased with increasing diffuse site factor, a(d) (relative amount of penetrating diffuse solar radiation), whereas needle thickness (D(1)) remained nearly constant, resulting in an inverse relationship between D(1)/D(2) and a(d) and an increase in the ratio of total (TLA) to projected needle surface area (PLA) with increasing a(d). Because of the variations in needle morphology with respect to light availability, the shoot parameters used in present canopy models are also expected to be light-sensitive, and studies involving shoot morphology should also consider the variability in needle geometry. Needle dimensions and total tree height were not correlated. However, LWA increase with both increasing a(d) and total tree height. When LWA was expressed as the product of ND and needle height (NH, height of the rhomboidal transverse section of a needle), LWA appeared to increase with irradiance, because of changing NH, and with total tree height, because of changing needle density.

Light environments and floristic composition across an open forest‐rainforest boundary in northeastern Queensland

Abstract This paper demonstrates the changes in structure, floristics and forest floor light regimes across the boundary between open forest and rainforest at Kirrama in northeastern Queensland. Hemispherical photographs of the canopy were used to estimate spatial and temporal variations in potential (clear‐sky) direct and diffuse photosynthetic photon flux density (PPFD = 400–700 nm) across the boundary. Five vegetation zones were identified across the boundary: (A) open forest, (B) tall open forest, (C) tall open forest with a rainforest under‐storey, (D) young rainforest, and (E) mature rainforest. During the summer (September–March) direct PPFD declined semi‐exponentially across the boundary, while in the winter (April–August), the decline was more linear. However, the decline in diffuse PPFD across the boundary was linear throughout the year. Mean per cent grass cover was positively correlated and mean per cent shrub cover negatively correlated with annual average total PPFD across the boundary. Mean percentages of diffuse radiation relative to that above the forest (diffuse site factors) ranged from 9.8% in the mature rainforest to 66.4% in the open forest, while mean percentages of direct radiation relative to that above the forest (direct site factors) ranged from 2.9–38.3% at the same sites, respectively. Daily PPFD in the rainforest understorey is probably insufficient for the shade intolerant (pioneer) species which prefer the more open environments on the rainforest margin where light intensities and soil temperatures are higher. Towards the rainforest end of zone C, light conditions appear to be similar to those experienced within small treefall gaps in rainforests. Typically, such light conditions are preferred by shade tolerant (primary) tree species that are unable to grow and reproduce successfully in the adjacent shaded understorey and to compete with the fast growing pioneer tree species in the more open end of zone C.

Leaf carbon gain simulation for tree seedlings acclimatized to microsite light regimes of a temperate pine forest

AbstractLeaf carbon gain simulation was performed for Quercus serrata seedlings with previously reported 6 day photosynthetic photon flux density (PPFD) histograms from 20 understorey microsites of a pine forest (Washitani &amp; Tang 1991). This simulation was performed with or without an assumption of the acclimatization of photosynthetic capacity (Pmax) to microsite light availability. A constant ratio of respiration rate to Pmax, within, the range of 0.07–0.1, was assumed as a constraint. In relatively well illuminated microsites with a diffuse site factor above 0.1, predicted optimal Pmax was about 5 μmol m−2 s−1, with the predicted mean daily net carbon gain being about 50 mmol m−2 day−1. Each of the predicted optimal Pmax and the simulated mean daily net carbon gains with a constant Pmax (5 μmol m−2 s−1) or the predicted optimal Pmax was linearly related to the microsite light availability index, diffuse site factor. Simulated net carbon gain was negative at diffuse site factors below 0.04, if the constant of Pmax was assumed. The predicted linear relationship between net carbon gain and diffuse site factor could provide an ecophysiological basis for the observed linear dependency of the relative growth rate of biomass of Q. serrata seedlings on the microsite diffuse site factor (Washitani &amp; Tang 1991).

Understorey light environments in a north-east Australian rain forest before and after a tropical cyclone

ABSTRACTThis paper describes estimates of canopy openness and associated light availability in the understorey of a north-east Australian rain forest before and immediately after a tropical cyclone. On the basis of 20 hemispherical (fisheye) canopy photographs it was shown that direct, diffuse and total site factors increased significantly as a result of the slight-to-moderate canopy disturbance caused by the cyclone. In the understorey, median total site factors ranged from 2.5–3.4% before the cyclone and from 6.0–8.6% after the cyclone, representing a 2- to 3-fold increase in potential light availability. Following the cyclone, mean relative gap frequencies increased substantially at all altitudes but particularly at canopy positions more than 70° above the horizon. Cyclone-induced canopy disturbance not only reduced the complexity of the understorey light regime but may have also increased the seasonal variability of light within the understorey of the forest during the interval of canopy recovery. The implications of these results for the ecophysiology of understorey tree seedlings and saplings at several temporal scales are discussed.

Effects of microsite light availability on the survival and growth of oak seedlings within a grassland

Effects of microsite light availability on the growth and survival of transplantedQuercus serrata Thunb. seedlings in aMiscanthus sinensis Anderss. grass canopy were investigated by a “plant's eye view” approach. Diffuse site factors, i.e., the fractional transmissions of diffuse photosynthetic photon flux density, were estimated at 15 cm aboveground in 108 microsites where the seedlings grew. Microsite diffuse site factors were significantly different between surviving and dead seedlings during the experiment period from April to October (F[1,14]=10.9, P<0.01). Relative growth rate of dry weight for individual seedlings positively depended on the diffuse site factors (r2=0.482, P<0.001 in May; r2=0.312, P<0.001 in October). Only 16 seedlings produced their second stem flush within the grass canopy. The ratio of height to dry weight of the second stem flush was significantly higher for the seedlings grew in shady microsites than for those in less shady microsites (r2=0,471, P<0.01 in May). This study suggests that the microsite heterogeneity of light availability is one of the important factors affecting the establishment of tree seedlings in patchy grasslands.

Microsite variation in light availability and seedling growth of Quercus serrata in a temperate pine forest

AbstractSpatial 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 of Quercus 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.

Tree Seedling Growth and Survival in a Malaysian Rain Forest

Growth and survival of tree seedlings were observed in lowland, evergreen, tropical rain forest in Pantai Aceh Forest Reserve, Penang, Peninsular Malaysia. Four natural gaps and two closed-canopy sites were used. In each site twenty 1 m2 plots were laid out at random and all the seedlings in them were identified, tagged, mapped, and measured for height and basal stem diameter, and the number of leaves were counted. After six months four of the sites were revisited, and after 16 months they were all revisited. Hemispherical canopy photographs were taken to calculate diffuse and direct site factors. At the start of the observations 1287 seedlings of 116 species were tagged. Over 16 months 251 (19.5%) seedlings died. Mortality was inversely correlated with seedling height. Potential direct radiation had no affect on seedling mortality. For the five common species the mortalities were: Shorea multiflora 6.2 percent, Hopea pedicellata 6.8 percent, Shorea curtisii 13.4 percent, Hopea beccariana 14.1 percent and Gluta curtisii 22.7 percent. The mortality of recruits from seed was: Shorea multiflora 19.0 percent, Shorea curtisii 29.1 percent and Gluta curtisii 29.5 percent. The seedlings grew very little over the 16 months. Height growth was greater in gap sites. There was a significant relationship between direct site factor and plot maximum height growth (r, = 0.399, P < 0.01) but its predictive value was poor (r2 = 0. 188). Gluta curtisii was the only species to show a significant relationship between direct site factor and height growth. Shorea multiflora and Gluta curtisii showed a significantly greater rate of height growth in the plots with above-median direct site factor compared to plots with below-median values. Shorea multiflora is a

Analysis of forest light environments part I. Computerized estimation of solar radiation from hemispherical canopy photographs

A microcomputer based system for the semi-automatic analysis of hemispherical canopy photos is described and evaluated. Images are transferred from film by a video camera to a digitizer for processing. Our program calculates diffuse and direct site factors (proportions of unobstructed radiation) according to Anderson's methods. These factors are used to estimate absolute amounts of radiation on a horizontal, subcanopy surface from measured or estimated values in the open. Additional indices calculated include the proportion of open canopy in the entire image and in the solar band, the cardinal octants, and 20 concentric rings plus a frequency histogram of potential sunfleck duration. About 20 photos can be processed in an hour. The program was designed for large-scale studies correlating plant biology and distribution or animal behavior with radiation regimes where time scales of several weeks or longer are of interest. Consistency and accuracy of estimates of mean daily global radiation by different operators permit meaningful intersite comparisons.

Photographic estimation of photosynthetically active radiation: evaluation of a computerized technique.

We describe a computerized technique for the analysis of hemispherical photographs of sites within plant canopies. The analysis yields estimates of canopy openness, a summary of the spatial distribution of canopy openings, estimates of direct and diffuse site factors, predicted times and durations of sunflecks for any date, and predicted daily courses of photosynthetically active photon flux density (PFD) for any date and for horizontal as well as inclined surfaces. By comparing estimates from photographs with measured values in 32 tropical forest microsites, we evaluate this technique and assess its potential and limitations. In sites of widely varying light availability, and with predictions specific to leaves at various angles, measured daily PFD correlated strongly (r=0.908) with predictions from photographs. Measured daily PFD was also closely correlated with estimates, from the photographs, of diffuse and direct site factors (r>0.8). Differences between predictions and measurements were proportionately largest in heavily shaded sites. Under clear conditions, this technique reliably predicted both daily PFD and the temporal pattern of PFD including predicting suflecks lasting more than a few minutes. However, temporal patterns of PFD predicted from photographs differ in potentially important details from measured patterns.