Shade-tolerant Research Articles

Overstory and understory resource competition variably influences conversion of introduced conifer plantations to native hardwoods

Restoration of native hardwood forests through tree planting may provide significant ecological and economic benefits, but reforestation in natural forests and afforestation on open field sites is challenging. Conversion of existing plantations of introduced conifers to hardwoods may provide an alternative opportunity for restoration. In the Midwest US, large areas of mature, introduced pine (Pinus spp.) plantations exist that have little economic and ecological value. These stands may provide ideal sites for planting of native hardwood species that have similar site preferences to pine. We sought to determine optimal management strategies for converting pine plantations by manipulating overstory canopy density and understory competition. We underplanted American chestnut (Castanea dentata (Marsh.) Borkh.) and northern red oak (Quercus rubra L.) seedlings in three overstory canopy treatments: control, shelterwood, and clearcut. Understory competition was either controlled or not through two growing seasons. After three growing seasons, oak performed best in the clearcut and chestnut in the shelterwood, reflecting variation in the species’ shade tolerance. Chestnut height and root collar diameter (RCD) were double that of oak, and chestnut leaf N content increased with light availability while oak did not, which can be explained by the species’ different adaptive strategies in biomass allocation. Both species had highest photosynthesis in the clearcut. Chestnut seedlings had significantly higher RCD in weeded clearcut and shelterwood plots, and oak in weeded clearcut plots. Weeding in the uncut control plots was ineffective because shade limited competition. Our results indicate that pine plantations offer suitable habitat for these hardwood species and provide insight regarding their growth strategies. Pine shelterwoods and clearcuts are each viable silvicultural conversion options for chestnut and oak if understory competition is controlled.

Effect of shade tree on nutrient concentration in coffee (Coffea arabica L.) leaves

Abstract Leaf tissue analysis is a measurement of the levels of elements contained in plant leaves. In this case, the leaves can describe the amount of absorption of a nutrient because most of the assimilation results are collected in them. The nutrients that can be absorbed by plant roots are the amount of nutrients available in the soil. The use of shade trees with different types of sunlight absorption intensity causes the conditions for leaf nutrient absorption in plants to also vary. This research was needed to determine the effect of shade type on the nutrient concentration of nitrogen, (N), phosphorus (P), and potassium (K) in the leaves of Arabica coffee plants. This research was carried out at the Koperasi Ribang Gayo Musara, Pantan Musara Village, Pegasing Subdistrict, Central Aceh District, Aceh, and the Agricultural Instrument Standardization Agency (BSIP) Aceh. This research used a non-factorial Randomized Block Design with five treatments where each treatment 4 replications. Treatments consisted of types of shade plants on coffee plants, namely, control/no shade, small lamtoro shade (Leucaena leucocephala ssp. leucocephala), big lamtoro shade (Leucaena leucocephala subsp. glabrata), banana shade (Musa paradisiaca L.), avocado shade (Persea americana Mill.). The results showed that shade tree type significantly affect potassium (K) nutrient levels in coffee plant leaves. Coffee plant shaded by big lamtoro had better N, P and K nutrient levels compared to small lamtoro, banana, avocado, and control.

Warming induced shade tolerance to become a key trait in invasion success of free-floating plant Pistia stratiotes over the native Hydrocharis morsus-ranae

Changes in nutrient concentration, temperature and light intensity due to climate change can alter the species composition of aquatic ecosystems, since global climate change can intensify the process of eutrophication. Eutrophication can enhance the biological invasion and the distribution of alien aquatic plants. Here we investigated the competition ability of alien Pistia stratiotes and native Hydrocharis morsus-ranae and the effect of different light intensities, temperatures and nutrient concentrations on the functional traits of the two species. In short term (8 days) monoculture experiment, we applied low (0.5 mg L-1 N; 0.05 mg L-1 P) and high nutrient concentrations (2 mg L-1 N; 0.2 mg L-1 P), four different light intensities (25–295 μmol m−2 s−1) as well as cold and warm (21.5; 27.5 ± 0.5°C) water treatments in full factorial design. In mixed cultures we cultivated the plants for 28 days with various biomass ratio, in shaded and well illuminated conditions, at a high nutrient concentration (4 mg L-1 N 1 mg L-1 P). In monocultures, the relative growth rate of P. stratiotes in warm water was significantly higher than that of H. morsus-ranae, however, this difference was not significant in colder water. In the co-culture experiment, P. stratiotes had significantly higher growth rate compared to H. morsus-ranae regardless of initial plant biomass ratio. Under shaded (65 ± 5 μmol m−2 s−1) conditions, P. stratiotes outcompeted H. morsus-ranae, resulting in its decay. Experimental results imply that with elevated temperature, the spread of alien P. stratiotes can be expected. Furthermore, under shaded conditions, P. stratiotes has a higher chance of occupying the water surface over the native plant H. morsus-ranae.

Monitoring Changes in Composition and Diversity of Forest Vegetation Layers after the Cessation of Management for Renaturalization

Overstory and understory vegetation play a vital role in forest ecosystem functionality. However, it is necessary to enhance the knowledge of their diversity and compositional dynamics following cessation of disturbance, which is required to inform restoration approaches and the mechanisms required for maintaining disturbance cessation. We conducted a chronosequence spanning 0–1, 5–6, 11–12, 20–24, and 28–34 years since disturbance cessation, and old-growth forests to investigate the dynamic changes in overstory and understory vegetation diversity and composition, as well as maintenance mechanisms following the cessation of anthropogenic disturbances in subtropical regions of Eastern China. The current study results indicated a decrease in understory cover and periodic fluctuations in the diversity of overstorey and understory vegetation following disturbance cessation efforts. Specifically, the shrub layer exhibited the highest richness in 28–34 years, while the herb layer showed the lowest evenness. Multivariate analysis using multiple-response permutation procedures indicated that the species composition and interspecific quantity ratio of understory plants in the forest at 28–34 years significantly differ from those in the early closure stage. An indicator species analysis revealed that more support was given to sun-loving plants after 0–1 years of the enclosure, while species with shade tolerance and low nutrient requirements were supported after 28–34 years. The structural equation model results show that 38.8% of the impact on herb evenness was related to light and substrate diversity. The ecological restoration time mainly indirectly affects understory vegetation by influencing the upper vegetation, light availability, and substrate heterogeneity. Overall, this study revealed that cessation of anthropogenic disturbance can maintain and care for understorey plant diversity and contribute to the sustainable management of forests.

Changes induced by parental neighboring touch in the clonal plant Glechoma longituba depend on the light environment.

Touch by neighboring plants is a common but overlooked environmental variable for plants, especially in dense vegetation. In addition, shade is inevitable for understory plants. The growth performance of clonal plant to the interaction between thigmomorphogenesis and shade response, and their impact on light adaptability is still unknown. At the present study, parental ramets of Glechoma longituba were exposed to two conditions (neighboring touch and shade), and their offspring ramets were in ambient or shaded environment. The phenotype and growth of parental and offspring ramets were analyzed. The results showed that neighboring touch of parental ramets regulated the performance of offspring ramets, while the effect depended on the light environment. The parental neighboring touch occurring in ambient environment suppressed the expansion of leaf organ, showed as a shorter petiole and smaller leaf area. Moreover, G. longituba exhibited both shade avoidance and shade tolerance characters to shaded environment, such as increased leaf area ratio and leaf mass ratio, longer specific petiole length and specific stolon length. It was notable that these characters of shade response could be promoted by parental neighboring touch to some extent. Additionally, parental light environment plays an important role in offspring growth, parent with ambient light always had well-grown offspring whatever the light condition of offspring, but the growth of offspring whose parent in shaded environment was inhibited. Finally, for the offspring with shaded environment, the touch between parental ramets in shade environment showed a disadvantage on their growth, but the influence of the touch between parental ramets in ambient environment was slight. Overall, the interaction of parental neighboring touch and shade environment complicate the growth of understory plants, the performance of plants is the integrated effect of both. These findings are conducive to an in-depth understanding of the environmental adaptation of plants.

Solar Lights for Highways with Zone-Wise Speed Control System for Vehicle

The challenge of providing adequate lighting along highways, particularly at critical points such as sharp turns and speed breakers, poses significant safety concerns. Traditional energy sources often fail to meet the demands of continuous lighting, especially in remote areas. To tackle this challenge, we present an automatic lighting system aimed at selectively activating lights during nighttime while also reducing vehicle speed near or at danger zones. Entire system is designed as automatic, human involvement is not required; lights are controlled automatically by sensing the vehicles. Whenever the vehicle enters into the danger zone, lights will be energized and they remain in ON state until the vehicle leaves that area. The system will be activated automatically during dark. In this method precious energy acquired from the solar panel can be saved. During the day time the battery will be charged and this stored energy is utilized in the nights[10]. It is a novel approach to vehicle navigation and safety implementation, and also aimed at automatically sensing the areas/zones like Schools, Hospital Accident, etc and automatically reducing the speed of the vehicle for safety purposes.

Coordination of bark and wood traits underlies forest‐to‐savanna evolutionary transitions

AbstractAimTo test the hypothesis that adaptive shifts leading to the assembly of tropical savannas involved coordination between bark and wood traits and to understand the underlying mechanisms.LocationTropical South America.TaxonAngiosperms (woody).MethodsWe compiled data on three bark traits (total, inner and outer relative bark thickness), wood density, maximum height, five secondary xylem traits and on species' habitat information (light environment, climate, soil and fire history) for Neotropical savanna, forest and generalist species (biome groups). We tested for pairwise and multivariate associations among traits across species and if biome group and habitat conditions explained species positions along the resulting strategy axes.ResultsTraits covaried along four different axes. The first axis was consistent with a trade‐off between fire (thick barks) and shade tolerance (low bark to diameter ratio, high vessel density) and contributed to differentiate the three biome groups according to the preference for shaded environments. Forest species also differed from savanna and generalist species in a separate axis by being more resource acquisitive. Maximum height and wood density did not strongly trade‐off with bark thickness, although maximum height was negatively covaried with relative outer bark thickness. Preference for shaded conditions was the main driver of variation in the two principal strategy axes, but temperature, fire and soil sand content also explained differences in plant stature between savanna and generalist species.Main ConclusionsAllocation to bark is constrained by trade‐offs with wood, opposing shade‐tolerant and acquisitive forest species to fire‐resistant and conservative savanna species. Rather than a single strategy axis, three axes are necessary to understand the functional differences among savanna, forest and generalist species. Because two of these axes are controlled by light availability, the associated traits tend to covary in space and time, but not across species.

Use of PGPR (Plant Growth Promoting Rhizobacteria) to Increase Yields of Cayenne Pepper (Capsicum frutescens L.) in Monoculture Planting Systems and Under the Shade of Mature Citrus Plants

Cayenne pepper is a vegetable commodity, which can be categorized as a commercial commodity and has the potential to be developed. The problem that arises is that more and more agricultural land is getting damaged. One effort to overcome this problem is to use organic fertilizers such as PGPR. The purpose of this study was to obtain the optimum dose of PGPR (Plant Growth Promoting Rhizobacteria) on the growth and yield (quantity and quality) of cayenne pepper in a monoculture cropping system and under the shade of mature citrus trees. The research was conducted in a Citrus Orchard, Tegalgondo Village, Karangploso District, Malang Regency. The time of the research was carried out in December 2022 - March 2023. This study used a Randomized Block Design (RBD) with two factors, namely the concentration of PGPR (Plant Growth Promoting Rhizobacteria) and the planting system. The first factor is the treatment of the application of the planting system which consists of 2 levels, namely MN (Monoculture) TS (Under the Orange Shade). The second factor was the treatment of PGPR concentration consisting of 4 levels, namely, P0 (without PGPR), P10 (10 ml.-1 concentration), P20 (20 ml.-1 concentration), P30 (30 ml.-1 concentration) and Treatment randomized in each group. and cropping system treatment. The results showed that there was no real interaction between the cropping system and PGPR on the growth of cayenne pepper plants. This is because there is a different effect on each treatment.

New perspectives on radial profiles of specific gravity in North American conifers

North American conifers exhibit three radial specific gravity (SG) patterns (Type 1, 2, and 3), which balance hydraulic and mechanical requirements. Type 1 and 2 patterns (Pinaceae) have low SG and high microfibril angle (MFA) corewood ensuring compliance, whereas in outerwood high SG/low MFA provide stiffness and strength resisting bending. Hydraulically, corewood, especially in Type 2 species, is resistant to embolism, whereas outerwood has higher specific conductivity. Cupressaceae (Type 3) have hydraulically very efficient, low SG outerwood, facilitating rapid growth. Corewood is flexible, whereas outerwood is mechanically weak and compensated for by more conical stems and durable heartwood (which prevents Brazier buckling). Radially earlywood (EW) decreases, and latewood (LW) increases for all types, whereas %latewood (%LW) increases (Type 1), decreases, then increases (Type 2) and decreases (Type 3). Ring SG increases when increasing LW SG and %LW are sufficient to counteract decreasing EW SG. Shade tolerance, crown recession, hormone gradients, and environmental variation affect patterns. Auxin concentration decreases with increasing distance from juvenile foliage slowing cell division, concomitantly gibberellin concentration (lignification) and carbohydrates (cell wall thickening) increase, producing higher %LW. Across a species range regions receiving relatively high summer rainfall have trees with higher %LW (by ring).

Inferring the tree regeneration niche from inventory data using a dynamic forest model

Abstract. The regeneration niche of trees is governed by many processes and factors that are challenging to determine. Besides a species's geographic distribution, which determines if seeds are available, a myriad of local processes in forest ecosystems (e.g., competition and pathogens) exert influences on tree regeneration. Consequently, the representation of tree regeneration in dynamic forest models is a notoriously complicated process which often involves many subprocesses that are often data deficient. The ForClim forest gap model solved this problem by linking species traits to regeneration properties. However, this regeneration module was never validated with large-scale data. Here, we compare this trait-based approach with an inverse calibration approach where we estimate regeneration parameters directly from a large dataset of unmanaged European forests. The inverse calibration was done using Bayesian inference, estimating shade and drought tolerance as well as the temperature requirements for 11 common tree species along with the intensity of regeneration (i.e., the maximum regeneration rate). We find that the parameters determining the species' light niche (i.e., light requirements) are similar for the trait-based and calibrated values for both model variants, but only a more complex model variant that included competition between recruits leads to plausible estimates of the drought niche. The trait-derived temperature niche did not match to the estimates from either model variant using inverse calibration. The parameter estimates differed between the complex and the simple model, with the estimates for the complex model being closer to the trait-based parameters. In both model variants, the calibration strongly changed the parameters that determine regeneration intensity compared to the default. We conclude that the regeneration niche of trees can be recovered from a large forestry dataset in terms of the stand-level parameters light availability and regeneration intensity, while abiotic drivers (temperature and drought) are more elusive. The higher performance (better fit to hold out) of the inversely calibrated models underpins the importance of informing dynamic models by real-world observations. Future research should focus on even greater environmental coverage of observations of demographic processes in unmanaged forests to verify our findings at species range limits under extreme climatic conditions.

How different daily light integrals and spectral treatments influence the development of Valerianella locusta plants grown in an indoor vertical farm

Light plays a crucial role in the development and growth rate of crops by impacting their physiology, morphology as well as the electricity cost for the system's operation which can significantly jeopardize the viability of a commercial-scale system. Different crops have different lighting demands in terms of quality (spectrum), quantity (intensity) and duration (photoperiod). At the same time only a little information is available in the literature concerning the minimum lighting requirements for indoor horticulture. This research aims to define the optimal combination of photoperiod, photosynthetically photon flux density (PPFD) and spectrum for indoor cultivation of Valerianella locusta plants by linking light and energy use efficiency to physiological responses of chlorophyll content and biomass production under different daily light integrals (DLI). Plants were cultivated in two growing towers with three layers of cultivation area under white LED lamps (WHITE) and two identical growing towers with three layers of cultivation area under blue/green/red/far-red lamps (BGRFR). The experimental setup is comprised of three different photoperiods (16, 14, 12 h · d−1) and three different PPFD (150, 250 and 350 μmol/m2s1), resulting in five daily light integrals (8.6, 10.8, 12.6, 14.4, 20.2 mol· m−2 · d−1). All growing towers and layers were equipped with a close-loop Ebb & Flow hydroponic system. Based on data analysis, spectra selection seems to have a significant impact on chlorophyll content, while lower DLIs did not correlate with lower chlorophyll content. The chlorophyll content was found to be similar either the plants received longer daily light hours or/and higher light intensity. Additionally, plants that grew under DLI 10.8 and 12.6 mol/m2d1 resulted in significantly higher fresh and dry biomass while at the same time required significantly lower electricity requirements due to the reduced hours of artificial lighting (14 and 12 h· d−1 respectively). Accordingly, light operation for Valerianella locusta plants under PPFD of 250 μmol/m2s1, 14 h of photoperiod and BGRFR spectra selection could be characterized as optimal for indoor cultivation to optimize the use of resources and ensure high-yield production, considering the specific setup of the cultivation system.

An arrow in the quiver: evaluating the performance of Hyptis suaveolens (L.) Poit. in different light levels

BackgroundHyptis suaveolens (L.) Poit., native to the American tropics, is a pantropical annual plant and a major invasive species throughout India. It was anticipated that the availability of sunlight, coupled with its superior reproductive potential, persistent propagule bank, and dispersal ability, could lead to an increase in the growth and spread of this invader, thus potentially impeding herbaceous growth and diversity in non-native areas. Clarifying its ecological fitness and competitive performance will be useful to manage the spread of H. suaveolens in natural ecosystems that are facing a wide range of anthropogenic pressures.MethodsThe present study is a three-tier experiment. In the first tier, a field study was conducted to assess the patterns of H. suaveolens abundance and herbaceous species diversity in response to light availability (sun, 842–1072 µmol m–2 s−1 and shade 253–341 µmol m–2 s−1) in the tropical dry deciduous ecosystems in the Vindhyan highlands, India. Furthermore, the impact of H. suaveolens abundance on the resident native and non-native species abundance and diversity was also studied. In the second tier, a randomized common garden experiment was conducted to understand the trait fitness of H. suaveolens in sun (940 µmol m–2 s−1) and shade (300 µmol m–2 s−1) conditions. In the third tier, a plant growth chamber experiment with high-light (940 µmol m–2 s−1) and low-light (300 µmol m–2 s−1) treatments was done to learn how H. suaveolens partitions its biomass between aboveground and belowground plant parts.ResultsThe field study indicated that the sunlit areas had a higher abundance of H. suaveolens and a lower diversity of resident herbaceous species than the shaded areas. The common garden experiment showed that sun-dwelling H. suaveolens individuals performed better in germinative, vegetative, eco-physiological, and reproductive traits than the shade-dwelling individuals. The growth chamber experiment exhibited that plants grown in high-light environment had greater seed germination, seedling recruitment, and aboveground biomass than those grown in low-light environment, whereas plants grown in low-light environment exhibited a higher root mass ratio than the high-light individuals. These results suggest that H. suaveolens individuals mask the understory vegetation owing to higher seedling recruitment, relative growth rate, photosynthetic performance, resource acquisition-allocation, and reproductive output in response to high-light conditions.ConclusionsThe study concludes that light significantly controls the invasive population dynamics of H. suaveolens in dry deciduous forests. In high-light areas, H. suaveolens populations dominate the forest understory with suboptimal shade tolerance. In shade environment, H. suaveolens maintains a persistent soil seed bank along with ‘Oskar individuals’ that become active in response to high-light availability. The modus operandi is a ‘sit and wait’ strategy. The current study provides insights on prioritizing areas for H. suaveolens management that will potentially reduce the risk of biological invasions on the native species diversity of tropical regions.

Degree of shade tolerance shapes seasonality of chlorophyll, nitrogen and phosphorus levels of trees and herbs in a temperate deciduous forest

Degree of shade tolerance shapes seasonality of chlorophyll, nitrogen and phosphorus levels of trees and herbs in a temperate deciduous forest

Ethnobotanical Study of Potential Food-Utilization of Shade and Undercover Vegetation in the Coffee Agroforestry Landscape, Kalibaru District, Banyuwangi Regency

Agroforestry is a cultivation system that integrates crops like coffee with various vegetation, as applied in the Kalibaru District. The local community utilizes an agroforestry system by combining shade and undercover plants that can be utilized as food. The objective of this study was to collect a diversity of edible vegetation and investigate the local utilization. Data was collected by vegetation analysis and ethnobotanical studies related to their use. The result showed that 22 species of shade plants and 22 species of undercover plants were edible. The highest use value of shade species in coffee agroforestry are Leucaena leucocephala, Musa paradisiaca, Syzygium aromaticum, Carica papaya, and Artocarpus heterophyllus. Meanwhile, the highest use values in undercover species are Capsicum frutescens, Manihot esculenta, Colocasia esculenta, and Maranta arundinacea. The highest index of cultural significance for shade species is shown in Carica papaya, Leucaena leucocephala, Parkia speciosa, and Musa paradisiaca. Meanwhile, the highest index of cultural significance for undercover species is C. frutescens, L. esculentum, P. amarylifolius, and C. longa. This area can support local food resources and serve as a means of cultural preservation.

Moderate-severity silvicultural methods generate better forest reorganization than other silvicultural methods in temperate rainforests four decades after implementation

Silvicultural regeneration methods promote regeneration of new tree cohorts following the harvest of mature trees and include a gradient of options from cutting all (clearcuts) or some (selection cuts) trees resulting in even- or uneven-aged forests. For forest managers and landowners, it is essential to have the best possible information on how forests reorganize following these different methods. Forest development, composition and growth are dependent on site quality and harvest type. In this study we evaluated two even-aged (clearcut (CC), seed-tree cut (STC)), one two-aged cut (extended irregular shelterwood (ISC)), one uneven-aged (single-tree selection cut (SC)), and an unmanaged control (CON), four decades after harvest implementation in old-growth Evergreen temperate rainforests above 500 m a.s.l. in the Coastal Range of south-central Chile. These forests grow on poor-quality sites due to old and shallow soil conditions and were dominated by late-successional species and a thick understory with the bamboo Chusquea machrostachya at the time of harvest implementation. Compositional and structural conditions reflected the type of harvests, with even- and two-aged methods largely similar to one another and the SC and the OG having very similar characteristics, which is likely a consequence of the very light severity of the SC. Tree species composition in even-aged harvests was dominated by shade midtolerant species of high timber value, although short-lived pioneer species of the Proteaceae family were also abundant, especially in ISC. The ISC had the greatest homogeneity in all stand variables (tree density, basal area, volume, and quadratic stand diameter), and since it was a two-layered forest, had basal areas and volumes close to the SC and OG, and a rotated-sigmoid diameter distribution (different to all other treatments). Height of the new cohort in the ISC was significantly taller than in the CC and the STC for most species’ groups, suggesting that the cut plus the residual canopy of ISC diminished the initial cover of the bamboo C. macrostachya and competition for regeneration. Only diameter growth of trees of all shade tolerances was lower in ISC, but diameter growth patterns were similar to CC and STC, with increasing growth during the first two-three decades followed by a decline. Based on these findings, we conclude that silvicultural methods of intermediate harvesting severity, especially ISC, provide the best ecological and economic option in these poor-quality sites given rapid reorganization following their implementation, while maintaining a relatively complex vertical structure, high tree species diversity, and a growing stock dominated by tree species of high timber value.

Formation of biometric parameters of sowings of soybean variety ‘Sirelia’ on typical chernozems depending on the nutrition area

Purpose. To determine the effect of row width and seeding rate on the biometric parameters of sowings of the early-ripening soybean variety 'Sirelia'. Methods. The research was carried out in 2021–2023 in the stationary crop rotation of the Plant Breeding Department in the fields of the Agronomic Research Station of the National University of Life and Environmental Sciences of Ukraine (Pshenychne, Vasylkiv district, Kyiv region). Scheme of the experiment: factor A – sowing method: ordinary row with a row spacing of 19 cm; strip with a row spacing of 19 × 38 × 12 cm; wide-row with a row spacing of 38 cm; factor B – seeding rate: 450, 600 and 750 thousand seeds/ha. Recordings were carried out in the main phases of crop development: budding, flowering and grain filling. Results. The thickening of crops with an increase in the seeding rate from 450 to 750 thousand seeds/ha contributed to a significant increase in the height of soybean plants: by 3.5 cm for row spacings of 19 cm and by 5.9 cm for row spacing of 38 cm. Seeding rate of 450,000 seeds/ha led to a decrease in plant height by 4.1 cm, or 5.2%. Thus, from the given data it can be concluded that the height of soybean plants increased with an increase in the seeding rate. The influence of the sowing rate on the growth of plants at a row width of 38 cm was particularly significant. The absolute dry mass of plants in the budding phase was within the range of 2.87–4.00 g, in the flowering stage 4.81–6.93 g, and in the seed filling stage 11.6–21.5 g. During the last period, the mass of plants in the case of increasing the seeding rate from 450 to 750 thousand seeds/ha decreased by 8.9 g, for a row spacing of 19 cm, and for a row spacing 38 cm by 7.3 g. The highest mass of plants was for the row width of 38 cm and the sowing rate of 450,000 seeds/ha. Conclusions. The height of soybean plants increases with an increase in the seeding rate. This is explained by the fact that the thickening of crops causes shading and elongation of plants. Soybean plants were the highest (81.9 cm) at a row spacing of 38 cm and a seeding rate of 750,000 seeds/ha. The highest absolute dry weight of one soybean plant was formed at a seeding rate of 450,000 seeds/ha, and significantly decreases in case of its increase to 750 thousand seeds/ha for all methods of sowing. That is, the thickening of crops with an increase in the seeding rate from 450 to 750 thousand units/ha led to a significant decrease in the dry weight of plants, which is explained by the deterioration of the conditions for their growth and development, primarily due to high competition for life factors.

Chemical Composition and Bioactivity of Dill Seed (Anethum graveolens L.) Essential Oil from Plants Grown under Shading

This study determined the content and composition of dill seed (Anethum graveolens L.) essential oil under varying light conditions: non-shaded plants in open fields and plants covered with pearl shade nets (40% shade index). Essential oil was extracted using Clevenger hydrodistillation. The essential oil content was 4.63% for non-shaded plants and 4.81% for shaded plants. GC/MS analysis revealed twenty-one and twenty-two components in dill seed from non-shaded and shaded plants, respectively. The terpenic fraction of essential oil from non-shaded plants consisted mainly of oxygen-containing monoterpene derivatives (53.6%), with carvone (46.1%) as the primary component, followed by monoterpene hydrocarbons (46.4%), predominantly limonene (43.8%). Essential oil from shaded plants contained a higher content of carvone (49.8%) and a lower content of limonene (37.8%) compared to essential oil from non-shaded plants. Non-shaded plant essential oil exhibited stronger antioxidant activity (EC50 value: 26.04 mg mL−1) than shaded plant essential oil (54.23 mg mL−1). Dill seed essential oil showed the most potent antimicrobial activity (disc diffusion method) against Escherichia coli (inhibition zone: 15–18 mm). Shaded plants demonstrated a positive influence of essential oil against Klebsiella pneumoniae. Carvone and its derivatives, as the main components, hold significant potential in the food industry and alternative medicines. A practical implication of this study could be higher plant densities or intercropping of dill, as it thrives with minimal light.

Effects of Flooding and Shade on Survival, Growth, and Leaf Gas Exchange of Bottomland Tree Species across the Great Lakes Region (USA)

Forested wetlands are common ecosystems within the Great Lakes region (Michigan, Minnesota, and Wisconsin), USA. Projected increases in extreme flooding events and shifting disturbance regimes create challenges for tree regeneration. Forest managers are considering the use of enrichment planting to increase tree species diversity, but limited information is available that quantifies the interactions between the flooding and shade tolerances of candidate tree species. We used a microcosm experiment to manipulate shade and flooding conditions to determine the effects on early survival, growth, and leaf gas exchange of 23 different tree species that vary in shade and flood tolerance. Seedlings were planted in pots and placed in 227 L tanks that were randomly assigned to light reduction (full sun, 40% and 70% reduced sunlight) and flood treatments (water levels of 0, 14, or 27 cm below the soil surface). In general, flooding treatments had a greater influence on seedling growth and leaf gas exchange rates than light reduction treatments. Of the species studied, bald cypress (Taxodium distichum (L.) Rich.) was the most flood-tolerant, but American sycamore (Platanus occidentalis L.) and river birch (Betula nigra L.) were also highly tolerant of flooding conditions throughout the entire growing season. The flood tolerances of the remaining species varied, but none were tolerant of water table depths within 14 cm of the soil surface for the entire growing season. Most species did not respond to the shade treatments in terms of early growth, survival, and leaf gas exchange. When considering species for planting in forested wetlands, matching the flood tolerance of candidate species to local site hydrology is an important step.

Shade responses and resistant mechanisms in Spatholobus suberectus

The medicinal plant Spatholobus suberectus Dunn is easily exposed to shade stress during growth, but its shade responses and shade stress resistant mechanisms have not been clarified. In this study, shade treatments including four attenuated sunlight intensities (100%, 60%, 40%, and 10%) and three shade durations (30 d, 45 d, and 60 d) were applied to S. suberectus. The shade-induced morphological indicators, phytohormonal regulations, metabolic flavonoids contents, transcriptomic flavonoid pathway gene expressions, and stress physiological changes of S. suberectus were analyzed. The putative promoter cis-regulatory elements (CREs) of 18 flavonoid biosynthetic pathway genes were identified. Results showed the stem growth indicators of S. suberectus were better at 40% light intensity. Phytohormones were involved in the shade-induced responses. Short-term shade (30 d) increased total flavonoids, gallated catechins and especially epigallocatechin gallate contents and favored for boosting medicinal value. Long-term shade (45 d, 60 d) tended to decrease flavonoids. The shade-induced flavonoids changes were attributed to their corresponding biosynthesizing genes expression variations. The high antioxidant capacity and the presence of phytohormone-, stress-, and development-related CREs provided the basis for stress resistance. In conclusion, the multiple responses under shade and the CREs analysis elucidated S. suberectus’ shade tolerance.

Linking High-Resolution UAV-Based Remote Sensing Data to Long-Term Vegetation Sampling—A Novel Workflow to Study Slow Ecotone Dynamics

Unravelling slow ecosystem migration patterns requires a fundamental understanding of the broad-scale climatic drivers, which are further modulated by fine-scale heterogeneities just outside established ecosystem boundaries. While modern Unoccupied Aerial Vehicle (UAV) remote sensing approaches enable us to monitor local scale ecotone dynamics in unprecedented detail, they are often underutilised as a temporal snapshot of the conditions on site. In this study in the Southern Alps of New Zealand, we demonstrate how the combination of multispectral and thermal data, as well as LiDAR data (2019), supplemented by three decades (1991–2021) of treeline transect data can add great value to field monitoring campaigns by putting seedling regeneration patterns at treeline into a spatially explicit context. Orthorectification and mosaicking of RGB and multispectral imagery produced spatially extensive maps of the subalpine area (~4 ha) with low spatial offset (Craigieburn: 6.14 ± 4.03 cm; Mt Faust: 5.11 ± 2.88 cm, mean ± standard error). The seven multispectral bands enabled a highly detailed delineation of six ground cover classes at treeline. Subalpine shrubs were detected with high accuracy (up to 90%), and a clear identification of the closed forest canopy (Fuscospora cliffortioides, >95%) was achieved. Two thermal imaging flights revealed the effect of existing vegetation classes on ground-level thermal conditions. UAV LiDAR data acquisition at the Craigieburn site allowed us to model vegetation height profiles for ~6000 previously classified objects and calculate annual fine-scale variation in the local solar radiation budget (20 cm resolution). At the heart of the proposed framework, an easy-to-use extrapolation procedure was used for the vegetation monitoring datasets with minimal georeferencing effort. The proposed method can satisfy the rapidly increasing demand for high spatiotemporal resolution mapping and shed further light on current treeline recruitment bottlenecks. This low-budget framework can readily be expanded to other ecotones, allowing us to gain further insights into slow ecotone dynamics in a drastically changing climate.