Degree Of Canopy Closure Research Articles

Ambrosia Beetles Prefer Closed Canopies: A Case Study in Oak Forests in Central Europe

Research Highlights: The percentage of canopy closure was found to be the main factor associated with ambrosia beetle abundance and species richness. The latter two variables increased as canopy closure increased, probably because a high percentage of canopy closure provides a stable and humid environment suitable for the growth of ambrosia fungi. Objectives: Oak is a common host tree for ambrosia beetles (Coleoptera: Curculionidae: Scolytinae), which have independently evolved a nutritional mutualism with fungi. We suspected that ambrosia beetles might have specific habitat preferences that are different from those of other saproxylic beetles and that reflect the specific habitat preferences of their food, i.e., ambrosia fungi. Methods: We assessed ambrosia beetle abundance with ethanol-lured traps in five old-growth oak dominated forests and five managed oak dominated forests (one trap per forest) during the vegetation period in 2020. We determined whether ambrosia beetle abundance and species richness depend on forest type (managed vs. unmanaged), degree of canopy closure, abundance of oak trees, abundance of coarse deadwood, and abundance of dead oak branches. Results: In total, 4137 individuals of six species of ambrosia beetles associated with oaks were captured. The native ambrosia beetle Anisandrus dispar represented the majority of trapped ambrosia bark beetles. A. dispar along with another ambrosia beetle, Xyleborinus saxesenii, represented 99% of all captured beetles. Conclusions: In addition to canopy closure, the abundance of oak trees and the abundance of dead oak branches were significantly associated with ambrosia beetle abundance and species richness. The abundance of A. dispar was mainly correlated with dead oak branch abundance and the degree of canopy closure, whereas the abundances of X. saxesenii and of the invasive species Xyleborinus attenuatus and Cyclorhipidion bodoanum were mainly correlated with the net area occupied by oak trees.

Effects of forest roads on Ips sexdentatus infestation in black pine forest

Forest roads are important transportation equipment through forested areas in the rugged, mountainous terrain of northern Turkey. Forest roads harm forest ecosystems due to both the manner in which they are established and how they are used afterwards. Damage to trees that occur during road construction through forests stresses trees, which facilitates outbreaks of bark beetle populations. Bark beetles are significant risk to the health and productivity of Turkish pine forests and to pine forests worldwide. In particular, Ips sexdentatus (Boerner) (Coleoptera, Curculionidae, Scolytinae) is a particularly destructive species of bark beetle in Turkish forests. Their damage to coniferous trees threatens the sustainability of the forest ecosystems. This study primarily aims to assess the intensity of damage that I. sexdentatus inflicts on Pinus nigra J.F.Arnold stands relative to several parameters: the distance to the nearest forest road, aspect (shady - sunny), slope (0–15% or >15%), and other stand characteristics. In this study, we show how damage by an I. sexdentatus infestation in pure black pine stands varies with distance to forest roads and in situ edaphic factors. We sampled 45 plots (400 m2 each), slope, aspect and distances to the nearest forest road was determined using ArcGIS software and the region‘s road network overlays. Results showed that trees located within 100 m from the nearest forest road were the most severely damaged ones. The intensity of I. sexdentatus damage was about 16% in a hectare. Trees that were in 16–20 cm diameter class were damaged more often. I. sexdentatus damage did not show any significant correlation with the slope, aspect or degree of canopy closure.

The potential for RGB images obtained using unmanned aerial vehicle to assess and predict yield in sugarcane fields

ABSTRACTEstimating yield is a major challenge for the majority of agricultural crops. With the advancement of field technologies however, especially those related to the use of Unmanned Aerial Vehicles (UAV) or Drones, the quality of available information has increased, making it possible to overcome technological bottlenecks. However, drone technologies have advanced much faster than studies dealing with the treatment and analysis of information, which can represent an obstacle to the complete adoption of such technologies in sugarcane fields. The objective of the present study was to evaluate the potential for UAV images to assess the degree of canopy closure from different planting approaches and row-spacing treatments applied to sugarcane crop, in order to assess the potential of these tools to predict crop yield. The vegetative growth of the crop was evaluated and the images were obtained at the point of maximum tillering and the inflection point of the biomass accumulation curve. The evaluations included the index; LAI (Leaf Area Index) and GRVI (Green-Red Vegetation Index) obtained by field sensor and UAV, respectively. Because the images from UAV cover the total area, the results revealed that GRVI appears to be much better able to reflect the whole condition of the crop yield (R2 = 0.69) in the field when compared to LAI (R2 = 0.34); demonstrated convincingly by the high spatial resolution capacity of the technology. When integrated, these two indices were able to improve yield estimates by 10% (R2 = 0.79). Images obtained using UAV can represent a low-cost tool for obtaining high-precision remote data that can be used to estimate the agricultural yield of sugarcane fields; and in this way are an effective tool to aid decision making by growers.

Escape to the high canopy-thermal deficiency causes niche expansion in a forest-floor ant.

The small formicoxenine ant Temnothorax saxonicus was known from about 40 localities in Central Europe nesting in anorganic substrates on floor of xerothermous forests whereas investigations of 198 tree canopies in 19 forest sites of the same region provided no indication for arboreal nesting or foraging. We present the first evidence for canopy-nesting populations of T. saxonicus on old Quercus trees in 3 sites having maximum calibrated topsoil temperatures of 17.9 ± 0.3 °C which were significantly (P < 0.007) lower than 22.8 ± 2.0 °C measured in 5 sites with ground-nesting populations. The thermal deficit on forest floor inhibits brood development in ground nests and caused a moving to canopy were maximum calibrated temperatures of the, now wooden, substrates are at least 26.1 °C for the whole canopy and 30.8 °C in more sun-exposed spots. T. saxonicus competed here successfully with the obligatory canopy ants T. affinis and T. corticalis. The distributional data of this rope-climbing study support former results that highest nest densities of small arboreal ants occur in temperate climate over the entire canopy mantle of single trees situated in open land or in park-like environments but occur in the top of the canopy in tree stands with high degree of canopy closure.

The influences of biotic and abiotic factors on the occurrence and severity of poplar canker disease in Qingfeng County, China and the management implications

Landscape pathology is a research approach that can provide validation of the effectiveness of regional controls of forest disease at a landscape scale. In this paper, we analyzed the effects of stand features, management approaches, and geographical locations on poplar canker disease incidence (DI) and disease severity index (DSI) of individual trees at a 10 km × 10 km mesoscale landscape in Qingfeng County, China. DI varied significantly with stand age, tree densities, and the degree of canopy closure. DI in stands younger than 4 years old was significantly lower than that in the stands over 6 years old and reached the highest value at a stand age of 8–10 years. Overall, DI was positively correlated with stand age, stand density, and the degree of canopy closure. DI was significantly lower in agro-forest stand patches than in other three patch types, i.e. isolated patch, pure stand patch, and mixed stand patch. Poplar plantations distributed around and near to villages exhibited significantly higher DI mainly due to human activities and herbivores. Fragmentation or connectivity in this mesoscale landscape seemed not impact disease occurrence. DSI was not significantly correlated with stand density, but varied significantly with tree varieties and trees ages. DSI was highest in stands of 10–12 year trees for all poplar varieties we studied here. Plantation density and plantation age were thus critical factors in determining DI and DSI. A logistic predictive model of disease occurrence was developed for the study area, considering varieties, age, height, density, canopy cover, stand types, patch types, management status, and stand geographical locations. Our study here shows that adjustment of stand density by thinning at different plantation ages is an effective approach controlling the occurrence canker disease in short-rotation poplar plantations at the landscape scale.

The mean tree mass–stand density index relationship for forest stands in China

Most traditional studies of mean tree mass (MTM)– density relationships focus on crowded stands, without considering stands characterized with canopy gaps. We developed a model to estimate MTM of closed and unclosed forest stands based on stand density index (SDI). Data were obtained from eight forest stands in China to test the generality of this model. MTM was accurately expressed in terms of SDI by combining the equations for SDI and Yoda's model, and exponents of the MTM–SDI relationship ranged from –2.23 to 1.93. Compared with density, SDI is a better predictor of MTM, regardless of the degree of canopy closure in the stands.

Perceptions of parks and urban derelict land by landscape planners and residents

As urban green spaces are important for residential satisfaction, human preferences are a key criterion in their design. However, preferences may vary between landscape planners and residents, which may result in differences between residents’ demands and the actual design. With urban derelict land becoming an important part of the urban green infrastructure, information about the perception and acceptance by residents compared to formal urban parks is important for their planning and design. It was thus examined how different types of urban green spaces are perceived by landscape planners and residents. Criteria for the classification of green spaces used by both participant groups were compared, as were the criteria that influenced preference.Participants sorted and rated photographs of parks and urban derelict land in two different tasks. Hierarchical cluster analyses and multidimensional scaling analyses were used to characterize the participants’ perceptual space. By conducting multiple regression analyses the resulting perceptual dimensions were related to preference.The identified perceptual criteria used to distinguish green spaces were degree of canopy closure, artificiality vs. naturalness, prospect, physical accessibility, and beauty. For residents, the degree of canopy closure was the most important criterion for classification; for landscape planners, it was artificiality. Preferences varied between groups: whereas landscape planners preferred rather natural areas with low accessibility and high species richness, the residents showed a greater preference for formal parks.As a practical implication, the study suggests that residents generally accept urban derelict land as recreational areas if a minimum of maintenance and accessibility is provided. When designing green spaces, landscape planners may consider these differences in their preferences compared to residents.

Evaluation of GPS collar performance by stationary tests and fitting on free-ranging Japanese black bears

We evaluated the performance of two GPS collars as a tool for studying Japanese black bears (Ursus thibetanus japonicus) in the Kanto region, Japan. Collars were placed at five stationary points to test the effects of GPS antenna orientation and degree of canopy closure on the fix rate and the positional error, and collars were deployed on 16 free-ranging bears to examine the fix rate and the effects of fix interval on fix rate. In the stationary tests, the proportions of no fix and of 2D fix (vs. 3D fix) increased as canopy closure increased and antenna orientation was further from vertical; at an antenna angle ≥90° from the vertical and canopy closure of 76.2–79.1%, the fix rate was <50%. The positional error for 3D fixes (ranged from 6.84 to 16.43 m) was significantly lower than that for 2D fixes (ranged from 30.74 to 43.45 m), and the positional error for both was affected by canopy closure and GPS antenna angle. An expected multipath effect on positional errors by rain was not statistically significant. Mean fix rates on collared bears ranged from 23.6% to 56.4% and were significantly lower than those in the stationary test. The fix rates at 5-min intervals were significantly higher than those at 4-hr intervals. Although our tests revealed some limitations and biases, GPS collar appears suitable for studying the movement and behavior of the bears.

Influence of environmental parameters on small-scale distribution of soil-dwelling spiders in forests: What makes the difference, tree species or microhabitat?

We surveyed the soil-dwelling spider communities of four stand types of forests (pure stands: spruce, Douglas fir; mixed stands: beech-spruce, oak-beech) along a successional gradient (four age classes: 15–112 years) to show the effects of small-scale microhabitat heterogeneity on the composition of spider assemblages. The investigation was carried out in south Germany. Spiders were collected by pitfall traps ( n = 96) in 4-week intervals. To reveal key environmental factors that affect spider communities, abiotic and biotic habitat parameters (e.g., temperature, air humidity, soil characteristics, and vegetation parameters) were systematically assessed around each pitfall trap. Spider species showed a small-scale distribution pattern on the forest floor, significantly affected by litter type, degree of canopy closure, temperature and humidity parameters, as well as cover of grass, moss, herb, and natural regeneration according to discriminant analysis and ordinations. The relevance of habitat parameters changed with the growing season. While many species were correlated to litter type and canopy closure in spring, the influence of ground vegetation and humidity parameters prevailed during summer. In fall, the strength of correlations decreased besides ground vegetation and soil humidity. The species assemblages assessed in the four forest types of different age classes indicate that the covering tree species has a profound influence on the small-scale distribution of spider species. Nevertheless, the high similarity in the composition of spider assemblages from different stand types but with similar formations of ground vegetation, microclimatic parameter and canopy closure displayed a considerable impact of environmental factors not necessarily bound to the stand type itself.

The distribution and incidence of white pine blister rust in central and southeastern Wyoming and northern Colorado

A survey of limber pine ( Pinus flexilis James) to determine the geographic distribution, incidence, and severity of white pine blister rust (WPBR) throughout 13 study areas in central and southeastern Wyoming and northern Colorado was conducted from 2002 to 2004. The majority (81.1%) of the 18 719 surveyed limber pines &gt;1.37 m tall were classified as healthy, 13.5% were declining or dying from various causes, and 5.4% were dead. WPBR was present on 278 (55%) of the 504 survey plots. Incidence of the disease ranged from 0% to 100% and averaged 15.5% over all the plots and 28.0% on the infested plots. Likelihood of infection by WPBR was significantly greater for limber pines in larger diameter classes. Incidence was negatively correlated with elevation and positively correlated with geographic position, with more northerly and easterly plots having higher incidences of WPBR. Incidence varied by slope position and did not vary by aspect, slope configuration, or degree of canopy closure. The current level of infestation in central and southeastern Wyoming and northern Colorado has been attained within the past two to four decades. With time, the pathogen may spread to currently uninfested white pine populations and intensify throughout its current distribution impacting valuable ecosystems.

Habitat Availability and Density Estimations for the Japanese Hare by Fecal Pellet Counting

Abstract We aimed to clarify the factors that affect Japanese hare (Lepus brachyurus) densities and habitat availability in certain vegetation types. Using fecal pellet counts, we found that hare densities and habitat availability were higher in open–tree-canopy habitats with a dense ground cover of herbs and grasses, such as cleared areas in artificial forests. However, when we examined the relationships between fecal pellets as an indicator of hare density and various attributes of forest floor vegetation, no vegetation parameters had a significant correlation with fecal pellets among different plant communities. Thus, it is difficult to predict hare density based on forest floor vegetation, in general. However, in seven Japanese cedar (Cryptomeria japonica) plantation sites, high herb volume index and a low degree of canopy closure, calculated from fisheye-lens photographs, had a significant correlation with fecal pellet density (P = 0.029 and 0.006, respectively). Based on the relationships between fe...

Identifying factors related to the severity of mammalian browsing damage in eucalypt plantations

Several mammalian herbivores damage young eucalypts growing in commercial Tasmanian plantations. Damage severity varies between plantations and damage control programs could be improved if the factors influencing this spatial variation were identified. In this study, measures of damage, herbivore abundance, plantation characteristics and the characteristics of forest adjacent to plantation areas were collected at 32 Eucalyptus nitens plantations during the first year of growth. Two exploratory analyses were conducted on two separate suites of site descriptors. The first, which modelled damage as a function of vegetation cover and herbivore scat counts, explained 71% of the between-site variation in damage severity. Damage was positively related to scat deposition rate for the brushtail possum and grass cover, and negatively related to fern (mainly bracken) cover. The second analysis modelled damage as a function of plantation characteristics that could be measured before planting and which may, therefore, be useful to forestry managers as damage predictors. This model explained 47% of between-site variation. Damage was negatively related to area to perimeter ratio and the degree of canopy closure in forest adjacent to plantations. Damage was positively related to the proportion of the perimeter that adjoined forest. Our results suggest that the importance of the brushtail possum, as a contributor to variation in damage between plantations, needs to be reviewed and that several measures of plantation characteristics have potential for use in future development of risk assessment systems.

Spatial distribution and habitats of useful plants: an initial assessment for conservation on an indigenous territory, Panama

In order to examine the spatial distribution of forest resources on local territories and to understand the factors controlling such distributions, we studied the spatial patterns of a group of 23 useful plant species on the territory of a Kuna community in the province of Darien, Panama. A stratified random sampling scheme was used to survey the distribution and abundance of the species across a 3500 ha area around the village. Data on the physical environment as well as the geographic coordinates of the sample plots were also obtained. A series of canonical analyses was conducted to evaluate the species–environment relationships and to identify spatial structures in the species distributions left unexplained by the environmental variables. Four distinct distribution patterns were identified among the species; these were most strongly explained by land-use, the degree of canopy closure and topography. Significant spatial structures, independent of the measured environmental variables, were related to anthropogenic pressure and an edaphic gradient, and the habitat associations of the individual species were described. The results obtained from this case study suggest that land-use dynamics may play a predominant role in structuring inhabited landscapes, and that diversity in distribution patterns and habitat associations will require a combination of spatially explicit management strategies to ensure the local resource base.

Factors influencing vegetation gradients across ancient‐recent woodland borderlines in southern Sweden

Abstract. We studied gradients in field layer vegetation across ecotone‐type borderlines between 12 ancient woodlands and adjacent secondary deciduous woodlands on former arable land. The aim of the study was to determine how distance from the borderline influences species distributions as compared with soil factors and degree of canopy closure. Correspondence Analysis showed that distance from the borderline is closely related to the first ordination axis at all study sites. Canonical Correspondence Analysis with variation partitioning revealed that distance from the borderline was the single most important factor in explaining vegetation variation. In general, the results suggest the following order of decreasing importance: Distance from the borderline &lt; Soil reaction &lt; Soil nitrogen &lt; Soil moisture &lt; Canopy cover. However, the sum of soil variables, as estimated by weighted averages of Ellenberg indicator values for moisture, reaction and nitrogen, accounted for as much as ca. 50–70% of the total variation explained by environmental variables. Important gradients in field layer vegetation are due to a decrease in typical woodland species and an increase in other species with increasing distance from the ancient woodland. The results suggest dispersal limitation of woodland species as an important determinant of secondary forest succession. However, the importance of distance to species distributions decreases with increasing stand age as most woodland species gradually colonize the recent woodlands. After 70 yr, ca. 50 % of the woodland species present at a site showed complete colonization within 50 m from the ancient woodland border.

Impact of forest canopy on quality and accuracy of GPS measurements

Global Positioning System (GPS) technology has become an essential tool in the Earth observation field for georeferencing, classification and accuracy assessment activities. While it was developed to be employed primarily in the open, many users nowadays operate GPS receivers in less favourable conditions. We investigated the impact of varying types and degrees of forest cover overstorey on GPS data collection, accuracy and precision. While the occurrence of canopy overhead may degrade the positional precision by one order of magnitude, it is the presence of the foliage itself (leaf-on condition) that plays a major role in the signal reception and the positional accuracy. The relationship is inverse, with increasing relative canopy closure resulting in decreasing logging efficiency and accuracy. We also found that under larger forest canopy the Position Dilution of Precision (PDOP) values may improve signal reception without deteriorating accuracy. Moreover, the relationship between degree of canopy closure and the accuracy RMSE follows an exponential pattern with small increases in relative canopy closure leading to huge increases in positional error. Averaging proved to be a powerful way to diminish residual positional error under forest cover, 300 fixes being proposed as a good number for GPS data acquisition under mature canopy conditions. Ultimately, we judged that PDOP is not as good an indicator for positional accuracy under forest canopy as is universally acclaimed.

Impact of Narrow Row Production on Yield Recovery, Nitrogen Use Efficiency, and Weed Competition in Sweet Corn

The processing industry is beginning to adopt narrow row configurations for sweet corn production thinking that plants spaced more equidistant will compete less with each other and weeds, improving yield potential and production efficiency. However, empirical knowledge relating to whether these proposed benefits change with hybrid, N fertility, and planting date is lacking. Narrow row (56 cm apart) sweet corn production was evaluated for improved production efficiency over the “traditional” row configuration (76 cm apart) at identical plant populations (60,000/ha). Yield from seed planted in narrow rows on 1 May was significantly higher than traditional row configuration. Increasing N fertilizer rate (0, 68, 136 kg N/ha) also yielded a positive linear response in yield across the three hybrids. As planting date progressed later into the season (27 May and 19 June), narrow row configuration benefits observed earlier began to diminish. Although increased N fertilizer rates continued to show a positive yield response across all planting dates, the degree of the slope decreased as planting date was progressively delayed suggesting a greater rate of N mineralization from the soil. Plant leaf samples were collected from each plot at silking for N analysis and determination of N use efficiency. Degree of canopy closure was dependent on plant architecture of the hybrid and N fertilizer rate; and may be related to postemergence weed competition and yield potential. The decision to convert to narrow row production would require a significant capital investment in new equipment. An economic assessment of the equipment required in addition to more detailed information on yield response to the narrow row configuration will help the processor make an informed choice when considering conversion.

Patterns of seedling recruitment in West‐Mediterranean Quercus ilex forest influenced by canopy development

Abstract. Quercus ilex (holm oak) coppice forests belong to the most representative communities in the western part of the Iberian Peninsula. Due to the high sprouting potential of holm oak after coppicing, the dynamics of recruitment of new individuals in existing populations has been largely overlooked. In these forests, the density of seedlings increases in old stands, as a result of the remarkable increase in the recruitment of 1‐yr and 2‐yr old seedlings, probably due to better environmental conditions for germination. Older seedlings show a tendency towards increasing survival under some degree of canopy closure, since their density appears to be higher just before complete canopy closure takes place. Nevertheless, the reduced growth of seedlings in older stands due to low light levels causes age distributions of holm oak seedlings to change drastically, with saplings older than 15 yr becoming very unusual in these stands. Therefore, a bottleneck of recruitment appears at this sapling stage and prevents vigorous regeneration just before thinning. Present conditions of genet density and management tend to prevent population renewal. Dynamics of the seedling bank reinforce the role of gap formation through small or large scale perturbations in population turnover.

Vegetation Dynamics of the Forest Edge -- Trends in Space and Successional Time

Forest herbs, shrubs, and tree seedlings were censused at five distances from human-generated edges at 14 sites in south-eastern Pennsylvania and northern Delaware, USA. Forest edges varied in orientation and in the degree of canopy closure, allowing comparisons of vegetation by aspect and successional stage. Soil depth and pH were measured at vegetation sampling points at a subset of sites; microclimate data were available from a parallel study. Edge-related pattern was observed in overall species composition, and in distributions of 15 individual species. At recently created forest edges, species abundances were correlated with steep climatic gradients. Although most edge-orientated species were clustered ≤ 5 m from the edge, some species consistently reached peak densities at distances up to 40 m, the greatest distance surveyed (...)

FOREST FLOOR VARIABILITY AND FACTOR ANALYSIS: A CASE STUDY

A case study is presented to illustrate how factor analysis can be used to quantify probable causes of physical and chemical forest-floor variability. Twenty forest-floor variables were examined for a 30 × 30-m sampling plot located within a mature, naturally regenerated conifer stand. "Slough" (the degree of accumulation of decayed stumps, logs, branches, etc.), litter (hardwood- vs. softwood-type in terms of base-status) and insolation (degree of canopy closure) factors appeared to underlie the observed variability pattern. Factor identification was facilitated by the following variable association pattern: (i) total C with total Fe, Al, N, P, K; (ii) total C with LFH-mass and thickness; (iii) water-extractable P with 2 N potassium-chloride-extractable NH4-H; (iv) total and 1 N ammonium-acetate-extractable Ca with pH; and (v) ground cover vegetation density with forest floor moisture content and thickness. Key words: Forest floor, lateral variability, factor analysis