Canopy Area Research Articles

Reclamation promotes the succession of the soil and vegetation in opencast coal mine: A case study from Robinia pseudoacacia reclaimed forests, Pingshuo mine, China

Robinia pseudoacacia is the dominant tree species in opencast coal mine reclamation in the Loess Plateau, China. Nevertheless, the long-term changes of reclaimed mine soils (RMSs) and vegetation in the reclaimed sites under R. pseudoacacia monoculture forest have not been sufficiently elucidated. In this study, the RMSs physicochemical properties were measured and vegetation (including tree, herb and reserved litter) indexes were surveyed in R. pseudoacacia monoculture forests at 7 reclamation ages (8-, 10-, 13-, 15-, 18-, 23- and 30-year) in the Pingshuo opencast coal mine, China. Adjacent, unreclaimed plot (hereafter called 0-year reclamation plot) was selected as the base line to detect the dynamics of RMSs properties and undisturbed site was chosen to compare with the reclaimed ones. The results showed that, pH (varied from 8.72 to 8.07) and soil bulk density (BD) (ranged from 1.62 to 1.36 Mg m−3) decreased along reclamation chronosequence. In contrast, soil organic matter (SOM, differed from 3.97 to 35.17 g kg−1), total nitrogen (TN, differed from 0.23 to 1.19 g kg−1) and available potassium (AK, ranged from 62.87 to 233 mg kg−1) were found to increase sharply (P < 0.05) in the initial phase of reclamation and tended to be stagnant in the subsequent stage. Moreover, available nitrogen (AN, varied from 7.07 mg kg−1 to 82.20 mg kg−1) was observed to follow a concave curve along reclamation chonosequence. Total phosphorus (TP, differed from 0.48 g kg−1 to 0.60 g kg−1), available phosphorus (AP, varied from 4.33 mg kg−1 to 8.3 mg kg−1) and total potassium (TK, varied from 14.23 g kg−1 to 19.37 g kg−1), however, fluctuated at steady conditions after reclamation and remained the undisturbed levels throughout the reclamation stages. The duration required to attain the nutrient level in undisturbed soils was speculated 10 years of reclamation in the Pingshuo mine. Tree indexes (i.e., diameter at breast height, height, canopy area, biomass and biomass density) increased with the duration of reclamation. Herb indexes (including height, coverage percentage and biomass density), however, followed inversed U functions. Conversely, reserved litter biomass decreased progressively over time. Vegetation indexes were found significantly correlated with SOM, TN, AN and AK (P < 0.05). Overall, R. pseudoacacia monoculture forests markedly ameliorated both soil and vegetation succession in the Pinshuo dumps.

Quantitative Analysis of Cotton Canopy Size in Field Conditions Using a Consumer-Grade RGB-D Camera.

Plant canopy structure can strongly affect crop functions such as yield and stress tolerance, and canopy size is an important aspect of canopy structure. Manual assessment of canopy size is laborious and imprecise, and cannot measure multi-dimensional traits such as projected leaf area and canopy volume. Field-based high throughput phenotyping systems with imaging capabilities can rapidly acquire data about plants in field conditions, making it possible to quantify and monitor plant canopy development. The goal of this study was to develop a 3D imaging approach to quantitatively analyze cotton canopy development in field conditions. A cotton field was planted with 128 plots, including four genotypes of 32 plots each. The field was scanned by GPhenoVision (a customized field-based high throughput phenotyping system) to acquire color and depth images with GPS information in 2016 covering two growth stages: canopy development, and flowering and boll development. A data processing pipeline was developed, consisting of three steps: plot point cloud reconstruction, plant canopy segmentation, and trait extraction. Plot point clouds were reconstructed using color and depth images with GPS information. In colorized point clouds, vegetation was segmented from the background using an excess-green (ExG) color filter, and cotton canopies were further separated from weeds based on height, size, and position information. Static morphological traits were extracted on each day, including univariate traits (maximum and mean canopy height and width, projected canopy area, and concave and convex volumes) and a multivariate trait (cumulative height profile). Growth rates were calculated for univariate static traits, quantifying canopy growth and development. Linear regressions were performed between the traits and fiber yield to identify the best traits and measurement time for yield prediction. The results showed that fiber yield was correlated with static traits after the canopy development stage (R2 = 0.35–0.71) and growth rates in early canopy development stages (R2 = 0.29–0.52). Multi-dimensional traits (e.g., projected canopy area and volume) outperformed one-dimensional traits, and the multivariate trait (cumulative height profile) outperformed univariate traits. The proposed approach would be useful for identification of quantitative trait loci (QTLs) controlling canopy size in genetics/genomics studies or for fiber yield prediction in breeding programs and production environments.

In-field High Throughput Phenotyping and Cotton Plant Growth Analysis Using LiDAR.

Plant breeding programs and a wide range of plant science applications would greatly benefit from the development of in-field high throughput phenotyping technologies. In this study, a terrestrial LiDAR-based high throughput phenotyping system was developed. A 2D LiDAR was applied to scan plants from overhead in the field, and an RTK-GPS was used to provide spatial coordinates. Precise 3D models of scanned plants were reconstructed based on the LiDAR and RTK-GPS data. The ground plane of the 3D model was separated by RANSAC algorithm and a Euclidean clustering algorithm was applied to remove noise generated by weeds. After that, clean 3D surface models of cotton plants were obtained, from which three plot-level morphologic traits including canopy height, projected canopy area, and plant volume were derived. Canopy height ranging from 85th percentile to the maximum height were computed based on the histogram of the z coordinate for all measured points; projected canopy area was derived by projecting all points on a ground plane; and a Trapezoidal rule based algorithm was proposed to estimate plant volume. Results of validation experiments showed good agreement between LiDAR measurements and manual measurements for maximum canopy height, projected canopy area, and plant volume, with R2-values of 0.97, 0.97, and 0.98, respectively. The developed system was used to scan the whole field repeatedly over the period from 43 to 109 days after planting. Growth trends and growth rate curves for all three derived morphologic traits were established over the monitoring period for each cultivar. Overall, four different cultivars showed similar growth trends and growth rate patterns. Each cultivar continued to grow until ~88 days after planting, and from then on varied little. However, the actual values were cultivar specific. Correlation analysis between morphologic traits and final yield was conducted over the monitoring period. When considering each cultivar individually, the three traits showed the best correlations with final yield during the period between around 67 and 109 days after planting, with maximum R2-values of up to 0.84, 0.88, and 0.85, respectively. The developed system demonstrated relatively high throughput data collection and analysis.

Strong radiative effect induced by clouds and smoke on forest net ecosystem productivity in central Siberia

Aerosols produced by wildfires are a common phenomenon in boreal regions. For the Siberian taiga, it is still an open question if the effects of aerosols on atmospheric conditions increase net CO2 uptake or photosynthesis. We investigated the factors controlling forest net ecosystem productivity (NEP) and explored how clouds and smoke modulate radiation as a major factor controlling NEP during fire events in the years 2012 and 2013. To characterize the underlying mechanisms of the NEP response to environmental drivers, Artificial Neural Networks (ANNs) were trained by eddy covariance flux measurements nearby the Zotino Tall Tower Observatory (ZOTTO). Total photosynthetically active radiation, vapour pressure deficit, and diffuse fraction explain at about 54–58% of NEP variability. NEP shows a strong negative sensitivity to VPD, and a small positive to fdif. A strong diffuse radiation fertilization effect does not exist at ZOTTO forest due to the combined effects of low light intensity, sparse canopy and low leaf area index. Results suggests that light intensity and canopy structure are important factors of the overall diffuse radiation fertilization effect.

Riparian canopy expansion in an urban landscape: Multiple drivers of vegetation change along headwater streams near Sacramento, California

Urbanization is thought to decrease riparian tree canopy cover, but this outcome may vary depending on geographic context. We examined changes in land cover and riparian tree canopy near Sacramento, California, a Mediterranean climate region impacted by agriculture before urbanization. We used aerial imagery to quantify changes in land cover and the area, width, and density of riparian tree canopy between 1937 and 2014 for the 85-km2 Arcade Creek watershed. While watershed land cover shifted almost entirely from pasture and crops to urban development, riparian forested area increased by 38 percent. The median width of riparian tree canopy more than doubled, and the density along smaller streams increased significantly (p < 0.0001). We used multiple data sources to examine potential drivers of these changes. Stream gage data and field observations indicated that the formerly intermittent Arcade Creek stream network receives spatially and temporally variable dry-season flow subsidies from urban runoff, but widespread channel incision may limit the impact of subsidies on riparian vegetation. Accordingly, sampling of riparian woody plants showed few hydrophilic species growing along these streams. Instead we found evidence of native oak regeneration and a high density of escaped horticultural species. The increase in riparian forest cover was thus likely due to changes in vegetation management and species composition from land use conversion, possibly augmented by increased dry-season water availability. The changes in canopy cover we quantified stand in contrast to the accepted pattern of riparian forest decline with urbanization, and are expected to affect ecosystem services.

Intraspecific leaf shape at local scale determines offspring characteristics

Identifying the degree of adaptation to particular environmental constraints at small geographical scales (e.g., intra-population variability) is particularly valuable to select plant reproductive material in restoration projects. We analyzed possible differences among progeny characteristics of Quercus coccifera L. a species of interest in forest restoration under Mediterranean climates. The differences were tested among seeds and seedlings from two phenotypic groupings (small and large leaves) within one provenance under semi-arid climate. In addition, these seeds and seedlings were compared with those from a near population under contrasted climate (i.e., subhumid climate). We analyzed differences in germination, growth and seedling morphological traits (height, number of leaves and canopy area). We considered the different characteristics of the progeny across different parent individuals, intra- and inter-population levels. We found seed provenance effects on germination and seedling morphology at different scales. Progenies from semi-arid populations and from parent plants with a smaller leaf size showed lower germination rates and lower development of above-ground structures (shoots and leaves). Our results suggest that intrapopulation variability for phenotypic traits, such as leaf size, could influence offspring fitness. In addition, these morphological traits are easily identifiable by stakeholders and could be a useful tool to ensure early plant establishment in reforestation programs.

Estimation of variability parameters for certain quantitative traits in cocoa (Theobroma cacao L.) genotypes

Cocoa (Theobroma cacao L.) is an important plantation crop of Malvaceae family and its center of origin is Upper Amazon basin of South America. In India, it is grown as an intercrop in coconut and arecanut gardens especially in South India. Morpho-agronomic characters of pods and seeds can be used to evaluate the relationship between cocoa genotypes. In the present study, significant variations inthe mean performance of 20 genotypes for 13 traits were observed which revealed that the germplasm collections being maintained have high breeding value. The GCV and PCV ranged from moderate to high. Traits like plant height, first branching height, canopy area, leaf area, pod weight and single dry bean weight recorded high PCV and GCV indicating the high variability. High heritability ranging from 52.81 per cent for number of beans per pod to 99.84 per cent for first branching height was recorded. High genetic advance as per cent of mean was recorded for canopy area (89.33 per cent). High heritability coupled with high genetic advance for all the traits except pod girth, bean length and pod value indicated that all these traits are controlled by additive gene action and has least environmental influence. Further, correlation analysis revealed association of various traits which can be used as selection criteria for efficient planning of cocoa breeding program.

Droplet distribution of Unmanned Aerial Vehicle under several spray volumes and canopy heights in the cotton canopy

Abstract: The influences of the canopy height and the spray volume on the droplet distribution in the upper and bottom of the cotton canopy were discussed in this study. XAG P30 plant protection Unmanned Aerial Vehicle(UAV) was used as a spray tool and water sensitive paper was used as the droplet test card. The spray volumes by the UAV include 18.0 L/ha,22.5 L/ha, and 30.0 L/ha. The average planting heights of cotton in the test areas are 0.5 m,0.7m, and1.1m, respectively. The results show that the droplets are more well-distributed in the upper part of the canopy rather than the lower part. The spray volume has a significant effect on the droplet distribution in the canopy. The coverage, deposition, and droplet density will gradually increase with the increase of the application volume. The droplet distribution in the1.1m canopy area is poor, but it can be improved by increasing the spray volume. Keywords: unmanned aerial vehicle; droplet distribution; spray volume; canopy height DOI: 10.33440/j.ijpaa.20200304.136 Citation: Chen P C, Lan Y B, Douzals J, Ouyang F, Wang J, Xu W C. Droplet distribution of Unmanned Aerial Vehicle under several spray volumes and canopy heights in the cotton canopy. Int J Precis Agric Aviat, 2020; 3(4): 74–79.

Trait variation of a generalist tree species (Eremanthus erythropappus, Asteraceae) in two adjacent mountain habitats: savanna and cloud forest

Cloud forests and savannas differ in several environmental aspects, particularly in light irradiance and water availability. Such differences can be selective for specific sets of leaves and architectural strategies to capture light and use water. In the present study we evaluated functional traits variation in a generalist species in two adjacent habitats experiencing an abrupt change in resource availability (light and water availability). We collected several leaf, stem and architectural traits of the tree species Eremanthus erythropappus (DC.) MacLeish in shrubland savanna (habitat facing higher drought stress and wind exposure) and cloud forest (shaded environment). Trees in the shrubland savanna exhibited functional trait values that enhance drought tolerance (i.e. higher wood density and leaf thickness) whereas trees in the cloud forest exhibited functional trait values that enhance light capture (i.e. taller individuals with higher leaf area and specific leaf area). Additionally, the individuals in the shrubland savanna had wider and deeper crowns, pointing that the benefits of a larger canopy area to capture light during the day and humidity from condensation at night exceed the higher risk of mechanical damage by falling debris due to high wind exposure. For all traits, variation among the individuals was lower than variation among habitats. Our results indicate the strong role of the environment as a driver of intraspecific variation and that architectural traits (usually poorly studied compared with other traits) should be included as an important parameter of variation in functional analyses when evaluating the effect of environmental conditions on tree performance.

Extending the baseline of tropical dry forest loss in Ghana (1984–2015) reveals drivers of major deforestation inside a protected area

Tropical dry forests experience the highest deforestation rates on Earth, with major implications for the biodiversity of these ecosystems, as well as for its human occupants. Global remote sensing based forest cover data (2000−2012) point to the rapid loss of tropical dry forest in South America and Africa, also, if not foremost, inside formally protected areas. Here, we significantly extend the baseline of tropical dry forest loss inside a protected area in Ghana using a generalizable change detection technique. The forest cover change detection is based on the normalized difference vegetation index (NDVI) derived from historical Landsat data (1984–2015). Field measurements were carried out in dry semi-deciduous forest and in the adjacent savanna and woodland. Estimates of the canopy area index and above ground woody biomass were related to NDVI derived from Landsat 8 data. The change detection indicated significant NDVI decrease in a large area initially covered by tropical dry forest, associated with deforestation. The peak in deforestation was found to have occurred between 1990 and 2002, hereafter, the conservation status of the area was improved. A combination of remote sensing data corroborated by secondary data sources provides evidence for the almost complete clearance of a tropical dry forest inside a strictly protected area, attributable to logging and land clearing for arable farming. The NDVI change detection also revealed NDVI increase in the adjacent woodlands from 2002 to 2015, demonstrating woody encroachment. Historical fire data from the MODIS burned area product indicate that the deforested area experienced a high frequency of anthropogenic burning since 2004, which may have caused further degradation and largely prevents forest regeneration. The results show the ongoing destruction of tropical ecosystems even within ostensibly protected areas and ask for the revision of protection and management strategies of such areas.

Estimating Tree Height and Diameter at Breast Height (DBH) from Digital Surface Models and Orthophotos Obtained with an Unmanned Aerial System for a Japanese Cypress (Chamaecyparis obtusa) Forest

Methods for accurately measuring biophysical parameters are a key component for quantitative evaluation regarding to various forest applications. Conventional in situ measurements of these parameters take time and expense, encountering difficultness at locations with heterogeneous microtopography. To obtain precise biophysical data in such situations, we deployed an unmanned aerial system (UAS) multirotor drone in a cypress forest in a mountainous area of Japan. The structure from motion (SfM) method was used to construct a three-dimensional (3D) model of the forest (tree) structures from aerial photos. Tree height was estimated from the 3D model and compared to in situ ground data. We also analyzed the relationships between a biophysical parameter, diameter at breast height (DBH), of individual trees with canopy width and area measured from orthorectified images. Despite the constraints of ground exposure in a highly dense forest area, tree height was estimated at an accuracy of root mean square error = 1.712 m for observed tree heights ranging from 16 to 24 m. DBH was highly correlated with canopy width (R2 = 0.7786) and canopy area (R2 = 0.7923), where DBH ranged from 11 to 58 cm. The results of estimating forest parameters indicate that drone-based remote-sensing methods can be utilized to accurately analyze the spatial extent of forest structures.

Estimation of rice protein content before harvest using ground-based hyperspectral imaging and region of interest analysis

Protein content, which represents rice taste quality, must be estimated in order to create a harvesting plan as well as next year’s basal dressing fertilizer application plan. Ground-based hyperspectral imaging with high resolution (1 × 1 mm per pixel) was used for estimating the protein content of brown rice before harvest. This paper compares the estimation accuracy of rice protein content estimation models generated from the mean reflectances of five regions of interest (ROIs): the overall target area, dark area (less illuminated parts of the rice plants), canopy area (leaves, yellow leaves, and ears), leaf area, and ear and yellow leaf area. The size of the target sampling area was 0.85 × 0.85 m. An R + G + B histogram and a GNDVI–NDVI image were used to separate the target area into the individual ROIs. The values of the coefficient of determination R 2 and the root mean square error of prediction (RMSE) were similar for each model: R 2 ranged from 0.83 to 0.86 and RMSE ranged from 0.27 to 0.30% for all models except for the dark area model, where R 2 = 0.76 and RMSE = 0.35%. There were no significant differences in the magnitude of the estimation error among all models. This result indicates that it is not necessary to obtain an image with a ground resolution that is greater than 0.85 × 0.85 m per pixel to estimate rice protein content before harvest. This result should provide useful information when deciding the altitude of platforms for imaging rice fields.

High Throughput Phenotyping of Blueberry Bush Morphological Traits Using Unmanned Aerial Systems

Phenotyping morphological traits of blueberry bushes in the field is important for selecting genotypes that are easily harvested by mechanical harvesters. Morphological data can also be used to assess the effects of crop treatments such as plant growth regulators, fertilizers, and environmental conditions. This paper investigates the feasibility and accuracy of an inexpensive unmanned aerial system in determining the morphological characteristics of blueberry bushes. Color images collected by a quadcopter are processed into three-dimensional point clouds via structure from motion algorithms. Bush height, extents, canopy area, and volume, in addition to crown diameter and width, are derived and referenced to ground truth. In an experimental farm, twenty-five bushes were imaged by a quadcopter. Height and width dimensions achieved a mean absolute error of 9.85 cm before and 5.82 cm after systematic under-estimation correction. Strong correlation was found between manual and image derived bush volumes and their traditional growth indices. Hedgerows of three Southern Highbush varieties were imaged at a commercial farm to extract five morphological features (base angle, blockiness, crown percent height, crown ratio, and vegetation ratio) associated with cultivation and machine harvestability. The bushes were found to be partially separable by multivariate analysis. The methodology developed from this study is not only valuable for plant breeders to screen genotypes with bush morphological traits that are suitable for machine harvest, but can also aid producers in crop management such as pruning and plot layout organization.

Effects of isolation on ant assemblages depend on microhabitat

AbstractHow isolation affects biological communities is a fundamental question in ecology and conservation biology. Local diversity (α) and regional diversity (γ) are consistently lower in insular areas. The pattern of species turnover (β diversity) and the influence of isolation on competitive interactions are less predictable. Differences in communities across microhabitats within an isolated patch could contribute to the variability in patterns related to isolation. Trees form characteristically dense and sparse patches (low vs. high isolation) in floating marshes in coastal Louisiana, and canopy and root areas around these trees could support distinct ant communities. Consequently, trees in floating marshes provide an ideal environment to study the effects of isolation on community assemblages in different microhabitats. We sampled ant communities in 120 trees during the summer of 2016. We found ant α diversity was not different between the canopy and roots, and the magnitude and directional effects of isolation on ants were inconsistent between the canopy and root areas. In the roots of sparse sites, ant diversity (α, β, and γ) was lower, species composition was changed, and the signature of interspecific competition was more prominent compared to dense sites. In the canopy, however, significant differences between dense and sparse sites were only detected in α and γ diversity, and ant species co‐occurrence was not significantly different from a random distribution. The inconsistent responses of ants in canopy and root areas to isolation may be due to the differences of species pool size, environmental harshness, and species interactions between strata. In addition, these findings indicate that communities in distinct microenvironments can respond differentially to habitat isolation. We suggest incorporating organisms from different microhabitats into future research to better understand the influence of isolation on the assembly of biological communities.

Estimating increased fuel loading within the Cross Timbers forest matrix of Oklahoma, USA due to an encroaching conifer, Juniperus virginiana, using leaf-off satellite imagery

Abstract Encroachment of eastern redcedar (ERC; Juniperus virginiana) into the Quercus dominated Cross Timbers region of the Southern Great Plains is an ongoing management issue that affects ecosystem services and wildfire hazard. The location and density of ERC in the forest understory and midstory are important information for fire managers seeking to estimate the behavior of fires or anticipate resources and attack methods needed to contain wildland fires. We developed a method to use remotely sensed, 3-band, satellite imagery to determine ERC presence and abundance within the Cross Timbers forest on 90 Bureau of Indian Affairs Trust Land properties in Pawnee and Payne Counties Oklahoma, USA. We used 130 (0.04 ha) field verification plots to establish the accuracy of the technique and estimate the biomass of the highly flammable ERC to determine the additional fuel loading that ERC encroachment represents. Compared to the field measurements, the satellite imagery identified approximately 50% of the ERC canopy area ([Actual Canopy Area] = 1.9517 ∗ [Classified Canopy Area] + 13.093, r2 = 0.78, n = 124). The relationship between ERC canopy area and ERC aboveground biomass was also determined ([Biomass (kg)] = 4.1839 ∗ [Actual Canopy Area] − 72.206, r2 = 0.71 n = 124). Estimating the biomass of the 90 larger tracts (10–65 ha) based on ERC canopy area, we calculated that ERC canopy cover averaged 21% within the forest matrix and that ERC biomass averaged 6.3 Mg ha−1 which represents a 38% increase in available fuel loading due to ERC encroachment. The addition of the highly flammable, evergreen ERC to the fuel load of the Cross Timbers forest likely increases the potential of wildfire damage. Our results can be used throughout the Cross Timbers region of Texas, Oklahoma, and Kansas, in coordination with fuel and fire simulation models, to inform management related to wildfire and fuel reduction treatments.

Seasonal and canopy height variation in n-alkanes and their carbon isotopes in a temperate forest

The stable carbon isotopic composition (δ13C) of terrestrial leaf wax components, such as n-alkanes (δ13Calk), is used extensively to address questions about past changes in vegetation, climate and the carbon cycle. To interpret sedimentary δ13Calk values, characterization of the environmental and biological controls on carbon isotopic fractionation during plant metabolism is required, especially for fractionation that occurs during photosynthesis (ɛleaf-CO2 or Δleaf) and n-alkane biosynthesis (εalk-leaf). Although much is understood about controls on ɛleaf-CO2, little is known about seasonal or within canopy variation in n-alkane composition and εalk-leaf. To address the gap, we sampled 5 common tree species (Acer rubrum, Acer saccharum, Juniperus virginiana, Sassafras albidum and Ulmus americana) from buds to senescing leaves from within a single temperate forest in southwestern Ohio, USA. We measured n-alkane concentration, δ13Calk, leaf biomass δ13C (δ13Cleaf), δ13C of atmospheric CO2 within the canopy, luminous flux and specific leaf area (SLA). In angiosperms, δ13Calk values were low in the buds, increased substantially (4–6‰) to the highest values in young leaves and then decreased (1–3‰) in mature leaves. Seasonal variation in δ13Calk values generally tracked changes in δ13Cleaf, but the fractionation between leaf and n-alkanes (εalk-leaf) was variable, with lower values in buds (−6.7 ± 1.1‰) than in young leaves (−4.9 ± 2.3‰). Later in the growing season, εalk-leaf values stabilized and ranged between −2.5 and −6.5‰, with a mean of −4.3 ± 1.4‰ in angiosperms. Stabilization of δ13Calk values coincided with settling of SLA and increase in average chain length (ACL). For the conifer, temporal variation in δ13Calk values was smaller (ca. 2‰) compared with the angiosperms, and εalk-leaf values slightly increased when n-alkane production increased. Average εalk-leaf value in the conifer at the end of the growing season was −5.0 ± 0.7‰. We speculate that εalk-leaf variation in both angiosperms and the conifer reflects changes in the source of carbon for plant metabolism, as well as the timing of wax synthesis. We also tested canopy effects on n-alkane concentration and carbon isotopic fractionation at different heights and extent of canopy closure. n-Alkane concentrations were higher at the top of the canopy by 2–8 times than in the lower canopy. The εleaf-CO2 values were more negative at the lower two thirds of the canopy than the upper one third of the canopy by 2–4‰ in two species with closed canopies. The εalk-leaf values did not vary with height and extent of canopy closure. To further explore the link between canopy leaves and leaf litter, we compared δ13Calk values of mature canopy leaves with those in leaf litter collected during senescence, and the offsets were within ca. 1‰. The results confirm indications that leaf litter δ13Calk values reflect those of the upper canopy leaves due to not only high leaf biomass in the upper canopy but also to high n-alkane production.

Natural regeneration of oriental beech (Fagus orientalis Lipsky) trees in canopy gaps and under closed canopy in a forest in northern Iran

For developing nature-based silvicultural practices in a beech forest to promote, abundance, height, vitality, and preferred growth form, regenerated trees growing in gaps were compared with those under closed canopies. A systematic 50 × 50 m grid was plotted in a beech stand in the Kheyrud Experimental Forest for selecting trees to measure variables in gaps and under closed canopies. Abundance and mean height of regenerated beech trees were significantly higher in closed canopies than in canopy gaps. Beech seedlings with excurrent growth were significantly taller within regeneration patches under closed canopy. Moreover, regenerated trees with high vitality were more abundant in closed canopy areas than in gaps. Thus, beech regeneration should improve under closed canopies; hence, gaps in a near natural forest should be created only after adequate regeneration and appropriate growth under the parent tree in a closed canopy area is ensured. The results of this research have profound implications for the sustainable management of the forest and for ensuring sustainable beech regeneration. The presence of a closed canopy cover likely will reduce potential stresses on oriental beech regeneration.

Variation in leaf biomass and fruit output of Juniperus indica along an elevation gradient in north-central Nepal

Biomass and reproductive output are important functional traits that influence aspects of plant performance. Measurements of these attributes by harvesting plant parts are often destructive and impractical. Therefore, non-destructive methods, based on allometric relationships, have been recommended for measuring plant biomass and reproductive output, particularly in the ecosystems where plant harvesting is not very practical or feasible. Here, we assessed the variation in the traits related to vegetative and reproductive performance (including plant height, trunk diameter, canopy area, leaf biomass and number of fruits set) among populations of Juniperus indica distributed along an elevation gradient in Manang district of the north-central Nepal, and finally determined the allometric relationships addressing the leaf biomass and the fruit output. The distribution range of J. indica was divided into lower- (3,350–3,580 m), mid- (3,650–3,880 m) and higher- (3,950–4,250 m) elevation classes where we made 54 sample plots of 10 m × 10 m size. In each plot, we recorded the number of individuals of J. indica classifying into seedling, juvenile and mature classes, and measured their vegetative traits and fruit output. Trunk diameter, leaf dry-weight and fruits set parameters spatially varied within the same elevation class. The individuals at the lower-elevation were larger in vegetative size with larger- trunk, height and canopy area, and produced higher leaf biomass and greater number of fruits as compared to those produced by the individuals situated at the mid- and higher-elevations. The regression analysis showed the strongest relationship between the canopy area and the leaf biomass. Thus, the use of outer canopy dimension is found to be the best option for estimation of leaf biomass of J. indica using non-destructive method.Banko Janakari, Vol. 27, No. 1, 2017, page: 3-10

Radiation use efficiency and biomass partitioning to storage roots in fodder beet crops

Abstract Intercepted photosynthetic active radiation (IPAR), radiation use efficiency (RUE) and partitioning of dry matter (DM) to storage roots (proot, %) were quantified for fodder beet crops subjected to contrasting water (irrigated or rain-fed) and nitrogen (N; 0, 25, 50, 100 and 200 kg/ha) supply conditions in Canterbury, New Zealand. The objectives were to enhance the understanding of physiological processes controlling fodder beet response to abiotic stresses and also to estimate parameters for biophysical models that simulate crop growth. Data from three field experiments showed a wide range of fodder beet yield (14–29 t DM/ha) in response to water and N stress. These yield differences were mostly explained by the treatments effect on IPAR (650–1050 MJ PAR/ha), with relatively smaller responses in RUE and proot. For unconstrained (fully irrigated; ≥100 kg N/ha) growth conditions, maximum values were 3.6 g DM/MJ PAR for RUE and 78% for proot for total biomass at final harvest. The RUE for the rain-fed, 0 kg N/ha crops was reduced by up to 25%, while proot was only marginally reduced (∼3% in rain-fed crops) compared with crops under unconstrained growth conditions. While the RUE responded linearly to additional N supply in irrigated crops, rain-fed crops showed a more consistent decline in RUE across N fertiliser rates with 65–70% of unstressed values. High RUE values were observed across a wide range of crop N status (Nitrogen Nutrition Index [NNI] from 0.8 to 1.6) in irrigated crops. In contrast, RUE in rain-fed was low at high NNI estimates because of high N concentration in a smaller canopy area. The lower RUE in rain-fed crops was aligned with reduced leaf photosynthetic rates (Pnleaf) although there was a high variability in Pnleaf measurements. These results give a first quantification of IPAR, RUE, proot and Pnleaf in fodder beet. They provide insights on the relative sensitivity of fodder beet to water and N stresses. These results are valuable for the interpretation of crop responses and for setting parameters for biophysical models to simulate fodder beet growth.

Experimental and numerical analysis of the influence of inlet configuration on the performance of a roof top solar chimney

The Roof Top Solar Chimney system is a natural solar updraft technique utilizing the solar energy to generate wind stream within the system passage that has enough driving force to create stack effect. The influence of the inlet shape of the solar air collector on the solar chimney performance was investigated experimentally and numerically in the present paper. Four different inlet configurations have been modeled and ANSYS FLUENT software was used to simulate and visualize the 2-D aero-thermal flow field surrounding the inlet region. Experimental measurements of the four different inlets were conducted using a roof top solar chimney set up to validate the simulation results and to evaluate and compare the system performance at each inlet configuration. The experimental model has two identical transparent covers installed over the roof of a room model, opened at the top to allow air flow from both sides to a chimney pipe. It was found that when the inlet has vertical cross section, it offered the best performance as the velocity and mass flow rate of the air at the chimney was observed to be higher compared with the other three inlet configurations. When the inlet cross section was employed as horizontal, the performance of the collector was reduced by 84% compared to the vertical inlet setting, at 1.00pm. The CFD analysis demonstrated, interestingly, that most of the air flow in the collector was directed from upper region above the inlet, while small amount is flowing from the bottom side of the inlet. This justify the reason of very low performance of air solar collector with horizontal orientation. The results revealed the possibility of reducing the area of the transparent canopy of the solar chimney power plant and convert the outer region to open top absorber.