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Increasing the number of transmit antennas can improve the diversity gain of the system, and accordingly reduce the transmit power dissipation. However, the high circuit power dissipation incurred cannot be ignored. Generalised selection combining, which could provide a certain spatial diversity in the transmit diversity systems, performs a good balance between system performance and practical implementation cost. In this study, the authors propose an energy efficient generalised selection combining (EE-GSC) scheme which obtains improved transmitter energy efficiency (EE) by providing a best tradeoff between the diversity gain and the circuit power dissipation of multiple antennas. Based on the classical results of order statistics, a theoretical analysis of EE-GSC performance is carried out in detail over Rayleigh fading channels. Based on this analysis, the average number of active branches as well as the average power dissipation of the proposed scheme is also derived. Numerical results are also given to further illustrate the EE performance of the proposed scheme.

Trace metal pollution is a vital issue in ecological problems (air, soil, and water), and it threatens human health in many urban areas worldwide. The accumulation of heavy metals released from various sources can readily occur on plants and impairs their growth. Therefore, monitoring metal concentration is extremely important when released into the atmosphere from one place to another urban environment. Biomonitor is one of the passive methods used to track selected elements. Chromium (Cr) has adverse effects on plants when it is in high concentrations; therefore, the variation of its concentration in plants is important to be assessed. Another target element, zinc (Zn), has different essential metabolic functions in plants and is crucial in protein and carbohydrate synthesis. It directly affects the plant due to its protein and carbohydrate synthesis role. This study aimed to determine the variation of the Cr and Zn concentration ratio in the organs of Picea pungens Engelm. from Ankara, Türkiye. According to organ, age, washing status, and location, Picea pungens Engelm. showed significant differences (p < 0.05) for Cr and Zn pollution on the road shoulders. Their location on the tree can easily determine the age of the needles and branches. The total values of bark for Cr and Zn were calculated as 23,887 ppb and 672,012 ppb in barks in unwashed samples. The result of the Cr and Zn content was significantly evaluated using ANOVA and Duncan test. The P. pungens is an excellent passive sampler as a biomonitor for the Cr and Zn distribution in the local atmospheric environment.

Accurately quantifying fine-scale forest canopy-absorbed photosynthetically active radiation (APAR) is essential for monitoring forest growth and understanding ecological processes. The development of 3D radiative transfer models (3D RTMs) enables the precise simulation of canopy–light interactions, facilitating better quantification of forest canopy radiation dynamics. However, the complex parameters of 3D RTMs, particularly detailed 3D scene structures, pose challenges to the simulation of radiative information. While high-resolution LiDAR offers precise 3D structural data, the effectiveness of different tree crown reconstruction methods for APAR quantification using airborne laser scanning (ALS) data has not been fully investigated. In this study, we employed three ALS-based tree crown reconstruction methods: alphashape, ellipsoid, and voxel-based combined with the 3D RTM LESS to assess their effectiveness in simulating and quantifying 3D APAR distribution. Specifically, we used two distinct 3D forest scenes from the RAMI-V dataset to simulate ALS data, reconstruct virtual forest scenes, and compare their simulated 3D APAR distributions with the benchmark reference scenes using the 3D RTM LESS. Furthermore, we simulated branchless scenes to evaluate the impact of branches on APAR distribution across different reconstruction methods. Our findings indicate that the alphashape-based tree crown reconstruction method depicts 3D APAR distributions that closely align with those of the benchmark scenes. Specifically, in scenarios with sparse (HET09) and dense (HET51) canopy distributions, the APAR values from scenes reconstructed using this method exhibit the smallest discrepancies when compared to the benchmark scenes. For HET09, the branched scenario yields RMSE, MAE, and MAPE values of 33.58 kW, 33.18 kW, and 40.19%, respectively, while for HET51, these metrics are 12.74 kW, 12.97 kW, and 10.27%. In the branchless scenario, HET09′s metrics are 10.65 kW, 10.22 kW, and 9.79%, and for HET51, they are 2.99 kW, 2.65 kW, and 2.11%. However, differences remain between the branched and branchless scenarios, with the extent of these differences being dependent on the canopy structure. Our conclusion demonstrated that among the three tree crown reconstruction methods tested, the alphashape-based method has the potential for simulating and quantifying fine-scale APAR at a regional scale. It provides a convenient technical support for obtaining fine-scale 3D APAR distributions in complex forest environments at a regional scale. However, the impact of branches in quantifying APAR using ALS-reconstructed scenes also needs to be further considered.

Canopy architecture determines the light distribution and light interception in the canopy. Reasonable shaping and pruning can optimize tree structure; maximize the utilization of land, space and light energy; and lay the foundation for achieving early fruiting, high yield, health and longevity. Due to the complexity of loquat canopy architecture and the multi-year period of tree growth, the variables needed for experiments in canopy type training are hardly accessible through field measurements. In this paper, we concentrated on exploring the relationship between branching angle and light interception using a three-dimensional (3D) canopy model in loquat ( ). First, detailed 3D models of loquat trees were built by integrating branch and organ models. Second, the morphological models of different loquat trees were constructed by interactive editing. Third, the 3D individual-tree modeling software LSTree integrated with the OpenGL shadow technique, a radiosity model and a modified rectangular hyperbola model was used to calculate the silhouette to total area ratio, the distribution of photosynthetically active radiation within canopies and the net photosynthetic rate, respectively. Finally, the influence of loquat tree organ organization on the light interception of the trees was analyzed with different parameters. If the single branch angle between the level 2 scaffold branch and trunk is approximately 15° and the angles among the level 2 scaffold branches range from 60 to 90°, then a better light distribution can be obtained. The results showed that the branching angle has a significant impact on light interception, which is useful for grower manipulation of trees, e.g., shoot bending (scaffold branch angle). Based on this conclusion, a reasonable tree structure was selected for intercepting light. This quantitative simulation and analytical method provides a new digital and visual method that can aid in the design of tree architecture.

Key messageRepeated pruning modified non-structural carbohydrate distribution in different organs of Quercus mongolica seedlings. Depletion of non-structural carbohydrates in the local stem released active branches from apical control.The stored non-structural carbohydrates (NSC) (i.e. sugars and starch) in trees play an important role in metabolism and growth, but their relationship with plant architecture is poorly understood. Mongolian oak (Quercus mongolica) is an important economic hardwood species in northeast China, but a lack of apical control during the seedling stage may reduce the potential to grow quality timber. In this research, we quantified the effects of repeated pruning (RP) on morphology, biomass, and NSC dynamics in Mongolian oak seedlings. The RP treatment significantly promoted the growth of terminal shoot by increasing the length of the second flush; however, rapid recovery of lateral branch growth indicated that the capacity for apical control was not enhanced. The RP treatment significantly modified longitudinal NSC distribution pattern in different growth units (GUs) of the stem, with higher NSC reserves in the upper parts of the stem expected to enhance growth potential. The sustained total NSC storage of the whole seedling, together with starch depletion at GU1 of the stem, indicated that both the carbohydrate status of the whole seedling and the local costs of starch are the reasons for maintaining the active branch growth. The quantification of the temporal and spatial variation in sugars and starch concentrations in different tissues improved our understanding of NSC dynamics in Mongolian oak, revealing the potential relationships between carbohydrate status and plant apical dominance in trees.

Faidherbia albida tree is known for its positive influence on most crops due to reverse leafing phenology. This study aimed at investigating the impact of pollarding F. albida on tree growth, wheat physiological performance and soil conditions. The study was conducted from June 2015 to October 2016 in Ejerssa Joro, a semi-arid region of Ethiopia. Leaflet per twig were scored. Sap flow volume and radial cambium growth were measured. Experimental design was employed with 1m2 areas under non-pollarded and pollarded trees from three directions and from different distances. Soil moisture, photosynthetically Active Radiation (PAR), air temperature and relative humidity (RH) were measured. Soil physicochemical properties were analysed. Wheat growth and physiology were measured. Sap volume in non-pollarded was 4590 L month−1 in January 2016 when the tree was fully foliated. Despite the spatiotemporal differences in leaflet per twigs between and within the trees, complete reverse leaf phenology was not observed during the study periods. Cambium growth was affected by pollarding F. albida. The PAR level and midday air temperature under non-pollarded were reduced by 77% and 6%, respectively. On the other hand, RH in dry periods and soil moisture in July under non-pollarded were higher by 15% and 42%, respectively. Most of the soil macronutrients found under non-pollarded trees ranged from moderate to high. The SPAD reading, shoot height and number tillers were significantly (p < 0.05) higher under non-pollarded trees compared to under pollarded trees of same distances. Thus, Pollarding F. albida reduced tree growth, wheat productivity, and understory microclimate conditions.

(1) Pine wilt disease (PWD) is a devastating disease of pine forests caused by the pine wood nematode (PWN), Bursaphelenchus xylophilus. Control of the disease is a worldwide problem due to the impossibility of using chemical nematicides on a large scale and for long periods. (2) Based on preliminary tests of microemulsion quality and stability, the optimum formulation was selected from 14 formulated microemulsions. The median lethal concentration (LC50) of the selected formulation at 48 h after treatment of B. xylophilus was 31.45 μg/mL of emamectin benzoate. The active ingredient reached the apical branches of Pinus thunbergii within 90 days of injection. (3) P. thunbergii was inoculated with B. xylophilus at 100 days post-injection, and the trees treated with the formulation remained uninfected for 450 days. Trunk injection exerted substantial control over PWD. (4) These results indicate that this formulation has the advantages of good transportability and long persistence in pine trees after injection and that it effectively prevents PWD. Therefore, this emamectin benzoate formulation can effectively reduce PWD occurrence in pine forests.

Key messagePruning could significantly promote branch formation, root development, and leaf growth, especially, improve flavonol glycoside and terpene lactones accumulation in leaves of ginkgo seedlings.Ginkgo biloba, an economically important tree species, is used as a medicinal plant due to the various secondary metabolites in its leaves. Pruning is the process of cutting branches to facilitate vegetative or reproductive growth. However, little is known about the effects of pruning on active compound accumulation in medicinal plants. Here, we found that after pruning 2-year-old ginkgo seedlings, branch number, ground diameter, and root size increased significantly; in particular, leaf size and crack number increased dramatically. Importantly, after pruning, fresh and dry leaf weights increased. Meanwhile, the total flavonoid, flavonol glycoside, and isorhamnetin contents of the leaves increased significantly, by about 24%, 20%, and 22%, respectively, and the contents of terpene lactones in leaves and roots increased by 8% and 28%, respectively. Through quantitative real-time polymerase chain reaction (qRT-PCR) analysis, we detected upregulation of flavonoid synthesis-associated genes, including chalcone synthase (CHS), flavonoid 3′-hydroxylase (F3'H), flavonol synthase (FLS), flavanone 3-hydroxylase (F3H) and anthocyanin synthase (ANS), and the terpene lactone synthesis-related genes acetyl-CoA C-acetyltransferase (AACT) in leaves after pruning. These results indicate that pruning promotes leaf growth and bioactive compound accumulation in ginkgo seedlings.

We investigated soluble carbohydrate transport in trees that differed in their phloem loading strategies in order to better understand the transport of photosynthetic products into the roots and the rhizosphere as this knowledge is needed to better understand the respiratory processes in the rhizosphere. We compared beech, which is suggested to use mainly passive loading of transport sugars along a concentration gradient into the phloem, with ash that uses active loading and polymer trapping of raffinose family oligosaccharides (RFOs). We pulse-labeled 20 four-year old European beech and 20 four-year old ash trees with 13CO2 and tracked the fate of the label within different plant compartments. We extracted soluble carbohydrates from leaves, bark of stems and branches, and fine roots, measured their amount and isotopic content and calculated their turnover times. In beech one part of the sucrose was rapidly transported into sink tissues without major exchange with storage pools whereas another part of sucrose was strongly exchanged with unlabeled possibly stored sucrose. In contrast the storage and allocation patterns in ash depended on the identity of the transported sugars. RFO were the most important transport sugars that had highest turnover in all shoot compartments. However, the turnover of RFOs in the roots was uncoupled from the shoot. The only significant relation between sugars in the stem base and in the roots of ash was found for the amount (r2 = 0.50; p = 0.001) and isotopic content (r2 = 0.47; p = 0.01) of sucrose. The negative relation of the amounts suggested an active transport of sucrose into the roots of ash. Sucrose concentration in the root also best explained the concentration of RFOs in the roots suggesting that RFO in the roots of ash may be resynthesized from sucrose. Our results interestingly suggest that in both tree species only sucrose directly entered the fine root system and that in ash RFOs are transported indirectly into the fine roots only. The direct transport of sucrose might be passive in beech but active in ash (sustained active up- and unloading to co-cells), which would correspond to the phloem loading strategies. Our results give first hints that the transport of carbohydrates between shoot and root is not necessarily continuous and involves passive (beech) and active (ash) transport processes, which may be controlled by the phloem unloading.

Key message An LED spectrum containing blue light advanced bud burst in branches of Betula pendula, Alnus glutinosa and Quercus robur compared with a spectrum without blue light in a controlled environment. During spring, utilising multiple cues allow tree species from temperate and boreal regions to coordinate their bud burst and leaf out, at the right moment to capitalise on favourable conditions for photosynthesis. Whilst the effect of blue light (400–500 nm) has been shown to increase percentage bud burst of axillary shoots of Rosa sp., the effects of blue light on spring-time bud burst of deciduous tree species have not previously been reported. We tested the hypotheses that blue light would advance spring bud burst in tree species, and that late-successional species would respond more than early-successional species, whose bud burst is primarily determined by temperature. The bud development of Alnus glutinosa, Betula pendula , and Quercus robur branches, cut from dormant trees, was monitored under two light treatments of equal photosynthetically active radiation (PAR, 400–700 nm) and temperature, either with or without blue light, under controlled environmental conditions. In the presence of blue light, the mean time required to reach 50% bud burst was reduced by 3.3 days in Betula pendula , 6 days in Alnus glutinosa , and 6.3 days in Quercus robur . This result highlights the potential of the blue region of the solar spectrum to be used as an extra cue that could help plants to regulate their spring phenology, alongside photoperiod and temperature. Understanding how plants combine photoreceptor-mediated cues with other environmental cues such as temperature to control phenology is essential if we are to accurately predict how tree species might respond to climate change.