Stem Diameter Variations Research Articles

Konsentrasi Eco Enzyme berbasis Sumber Daya Lokal Ternate Mendukung Pertumbuhan Tanaman Kailan (Brassica oleracea var. achepala)

This study aims to examine the concentration of Eco-enzymes based on local Ternate resources in dealing with the greed of Tutman Kailan which was carried out in the Tabam sub-district, North Ternate district. The study used a factorial completely randomized completely randomized design (CRD) with two factors as the main factors. Concentration of top taluk ecoenzyme Eight concentrations of top taluk taluk without concentration (R0) to 7 ml/l water (R7) and lead factor. Kailan seed variety that talukat consists of two varieties, namely the Daily Fram variety and the red arrow variety. The tools used in this study were digital scales, ruler, caliper, spoon, 5 kg polybag, digital camera, sack, label, stationery, paper, hoe. The materials used in the research were soil media, kailan seed, Eco-enzyme. The research was carried out in several stages, namely the manufacture of eco enzymes, preparation of planting media, planting, and data collection. The results showed that the concentration of eco-enzyme based on local resources in Ternate did not have an interaction effect but gave a singular effect, a concentration of 5 ml/l water (R5) resulted in the highest plant height of 34 cm and the number of leaves 7.67 while in leaf area, 2006, 85 cm at a concentration of (R7) 7ml/water but not different from R5. Variable stem diameter Plant fresh weight and root dry weight had no significant effect, while the total fresh weight of treatment R5 gave the highest fresh weight of 280 g in the red arrow variety (V2) as well as the total dry weight of 23.37 g in treatment R5 but the difference variety has no effect.Keywords: Concentration of eco enzyme, local resources, kailan plant

TURION: A physiological crop model for yield prediction of asparagus using sentinel-1 data

In Peru, asparagus is an important crop for the export market. Forecasting the yields is key in planning ahead sales to exporters. Farmers currently apply an empirical method by counting the number of mature buds per crown per metre and making linear regressions with the previous harvests. There was no simulation model so far for a continuous cycling crop grown in Peru. Therefore, this research describes TURION, a mechanistic crop model coded in Python which includes 27 physiological parameters, some crop variables based on literature and field data. Growth rate, thermal time per phenological stages, biomass partition, stem diameter variations, spear volume and leaf area index (LAI) across the crop cycle were determined for model parameterisation. TURION includes three sub-models: (1) spears production and its root carbohydrates (CHO) depletion, (2) stems establishment and its root CHO depletion and (3) replenish CHO storage in roots by photosynthesis, LAI and CHO translocation. This model predicted: yield, numbers of spears, biomass of spears/stems, and root CHO changes brix% values. Predictions provided outputs at plant level. This model was validated on crops ranging from 3 to 12 years post-establishment, for 75 commercial harvests reported between July 2018 and May 2020 over 38 different plots. Results showed a relative root mean square error (rRMSE) of 16.72 % for final yield, 13.46 % for CHO at the end of harvest and 9.79 % CHO at the end of the crop cycle.

GENETIC PARAMETERS AND SELECTION CRITERIA IN QUINOA

Quinoa (Chenopodium quinoa Willd.) is a crop with high nutritional and agronomic potential, adapted to environmental stress conditions. It is grown on a small scale in Mexico, and currently improved varieties are not available. In order to establish the basis to guide genetic improvement in Mexico, the objective was to determine the genetic variability, heritability and interrelationships of yield and its components in 16 quinoa genotypes, in a randomized complete block design, in six environments in the central high valleys of Mexico. The proportion of participation of the sources of variation genetic, environmental, and genotype × environment interaction was determined; as well as heritability, response to selection, and phenotypic correlations among morphological characters, yield and its components. Out of 15 variables evaluated, the genetic effects on thousand-grains weight and grain filling period were the most important; whereas for plant height at flowering, harvest index, and stem diameter, environmental effects were the most relevant. The genotype × environment interaction is not greater than 20 % for the 15 variables evaluated. The highest values for additive variance, heritability, and response to selection were for grains per square meter, yield, thousand-grains weight, grain filling period, and panicle emergence. The variables stem diameter, plant height at maturity, grains per square meter, yield per day, grain filling period, and panicle emergence were the most correlated with yield. Therefore, they can be used as indirect yield selection criteria in breeding programs to obtain materials with better agronomic characteristics. Based on the genetic parameters obtained and the association of the variables with yield, grains per square meter, yield per day and plant height at maturity are the most appropriate traits for indirect selection for yield.

Effect of Foliar Application of Chitosan on Growth, Yield and Nutritional Qualities of Red Amaranth (Amaranthus gangeticus L.)

Chitosan is a promising natural biopolymer that stimulates growth, increases yield, and boosts-up plants' immune systems. A field experiment was conducted to study the effect of foliar application of chitosan on growth, yield and quality attributes (viz. chlorophyll-a, chlorophyll-b, total chlorophyll, carotenoids, total ash and major nutrient contents) of red amaranth. The field experiment was laid out in a Randomized Completely Block Design (RCBD) with three replications and six treatments [viz. T0 = Control (no chitosan application); T1 = 100 mg L-1; T2 = 150 mg L-1; T3 = 200 mg L-1; T4 = 250 mg L-1 and T5 = 300 mg L-1 chitosan solution]. The study results revealed that the application of chitosan at different doses had no significant effect on plant height, the number of leaves plant-1, and the moisture content of red amaranth. But there were significant variations in stem diameter, root length, and yield of red amaranth. Similarly, the application of chitosan at different doses also showed a significant effect on chlorophyll contents, carotenoids and total ash contents of red amaranth. The average chlorophyll-a, chlorophyll-b, total chlorophylls, carotenoids and ash content of red amaranth ranged from 6.02-9.51, 3.67-5.92 and 9.68-15.15 mg g-1 tissue, 0.20-0.28 µg g-1 sample (fresh wt.), and 16.36-17.69%, respectively. Among the major nutrient elements, the amount of Ca, Mg, Na, K and P in red amaranth was statistically insignificant among the treatments. On the contrary, the effect of foliar application of chitosan at different doses disclosed a statistically significant difference in S, Zn and Fe contents of red amaranth. The highest amounts of chlorophyll-a, carotenoids, total ash, S, and Fe in red amaranth were obtained from treatment T5. Finally, the study results concluded that foliar application of chitosan at 300 mg L-1 has a significant positive effect on the growth, yield, pigments, S, and Fe contents of red amaranth.

Trocas gasosas e crescimento do amendoim submetido ao estresse salino e hídrico

ABSTRACT Peanut crops are of great economic interest because their seeds are used as an important source of vegetable protein and edible oil. The objective of this study was to evaluate the physiological indices and growth of peanut crops subjected to saline and water stress. The experiment was conducted in Auroras, Redenção, Ceará, Brazil using a completely randomized split plot statistical design. The plots were composed of irrigation water treatments with varying levels of electrical conductivity - ECw (1.0, 2.0, 3.0, 4.0 and 5.0 dS m-1), while the subplots were formed by the water regimes of 50% and 100% crop evapotranspiration. Plant height, leaf number, shoot dry matter, relative chlorophyll level, transpiration, and leaf temperature were affected by salt stress. The water regime of 100% ETc provided better performance for the variables stem diameter, leaf number, and shoot dry mass of peanuts.

Pengaruh Pupuk Organik (Kandang Kambing) Terhadap Pertumbuhan dan Hasil Tanaman Tomat (Lycopersicum Esculentum Mill)

This study aims to determine the effect of giving organic fertilizer (goat cage) with different doses on the growth and yield of tomato plants. The study used a randomized block design with one factor, namely P0 = No treatment (control), P1 = dose of goat manure 4 kg.plot-1 equivalent to 10 t.ha-1, P2 = dose of goat manure 6 kg.plot-1 equivalent with 15 t.ha-1, P3 = dose of goat manure 8 kg.plot-1 is equivalent to 20 t.ha-1, P4 = dose of goat manure 10 kg.plot-1 is equivalent to 25 t.ha-1. The results showed that the treatment with various doses of organic fertilizer (goat cage) was 6 kg. gave results that had a very significant effect on the observation variable stem diameter 45 DAP, tomato plants showed an average of 3.79 cm, had a very significant effect on fruit weight of tomato plants on the observation variable showed an average of 232.50, had a very significant effect on the observed variables. flowering age of tomato plants with an average of 30, and significantly affected the observed variables of tomato plant height 45 DAP, number of leaves 15 DAP and 30 DAP and stem diameter 15 DAP

Legacy of thinning on woody species composition and structure in southern Appalachian Mountain hardwood forests: restoration implications

In the Appalachian Mountains, Liriodendron tulipifera monocultures are widespread, with these forests lacking both species and structural diversity. In this study, we developed models that described the effects of thinning treatments, conducted almost 60 years ago, on the density, composition, and functional identity of the woody understory in L. tulipifera forests. The woody understory of these thinned L. tulipifera forests was diverse, with the small seedling (<1.4 m), large seedling (≥1.4 m and <2.54 cm dbh), and sapling (≥2.54 and <12.7 cm) layers possessing 38, 32, and 23 species, respectively. Although model performance was low to moderate (r2 = 0.05–0.40), we found that legacy effects, alone or in combination with environmental variables, explained, in part, the variability associated with the density, composition, and functional identity of the small seedling, large seedling, and sapling size classes, with the relative influence of legacy versus environmental effects varying by metric and size class. Post‐thinning basal area and/or percent of basal area removed were not the primary legacy effects influencing the woody understory. Instead, legacy effects associated with species composition of the overstory before and/or after thinning along with average stem diameter post‐thinning, variation in stem diameter post‐thinning, and age at the time of thinning were more influential than density or thinning intensity. This study provides evidence that conserving species diversity during forest management activities can have positive long‐term effects on composition and function of the woody understory and increase restoration potential.

Environment Controls Seasonal and Daily Cycles of Stem Diameter Variations in Portuguese Oak (Quercus faginea Lambert)

Tree growth takes place at different time scales ranging from hours to days. To understand growth responses to climate, continuous high-resolution measurements of tree diameter variations are needed, which are usually obtained with automatic dendrometers. Here, we monitored stem diameter increment of Quercus faginea Lambert growing in central Portugal to determine the effect of climate on daily and seasonal growth dynamics during the 2013 growing season. Stem diameter variation presented a unimodal seasonal pattern characterized by an exponential phase in spring followed by a plateau during summer, interrupted by an abrupt increase in autumn caused by rainfall. Stem diameter increment started in March when the temperature was above 10 °C. Stem diameter variation showed a double climatic constrain, with temperature limiting growth in spring and precipitation in summer. The amplitude of the daily cycles of stem variation was higher in summer, as well as the expansion phase length, meaning that trees needed longer to replenish the water lost through transpiration during the day. The absence of a pronounced stem shrinkage during the summer suggests that Q. faginea has access to water over the whole growing season. Our results indicate that this species relies on deep soil water reserves and can be physiologically active during summer drought.

Mechanistic drivers of stem respiration: A modelling exercise across species and seasons.

Stem respiration (RS ) plays a crucial role in plant carbon budgets. However, its poor understanding limits our ability to model woody tissue and whole-tree respiration. A biophysical model of stem water and carbon fluxes (TReSpire) was calibrated on cedar, mapleand oak trees during spring and late summer. For this, stem sap flow, water potential, diameter variation, temperature, CO2 efflux, allometry and biochemistry were monitored. Shoot photosynthesis (PN ) and nonstructural carbohydrates (NSC) were additionally measured to evaluate source-sink relations. The highest RS and stem growth was found in maple and oak during spring, both being seasonally decoupled from PN and [NSC]. Temperature largely affected maintenance respiration (RM ) in the short term, but temperature-normalized RM was highly variable on a seasonal timescale. Overall, most of the respired CO2 radially diffused to the atmosphere (>87%) while the remainder was transported upward with the transpiration stream. The modelling exercise highlights the sink-driven behaviour of RS and the significance of overall metabolic activity on nitrogen (N) allocation patterns and N-normalized respiratory costs to capture RS variability over the long term. These insights should be considered when modelling plant respiration, whose representation is currently biased towards a better understanding of leaf metabolism.

Daily variations in tomato stem diameter as a criterion for irrigation management

The process of daily variation in tomato stem diameter is examined in order to justify the use of this parameter to control drip irrigation. Changes in the size of individual plant parts depend on the provision of water, light, heat and nutrients to the production process. Therefore, such plant parameters as leaf temperature, xylem flow rate, fruit and stem diameter can be indicators of availability of necessary resources. The research was carried out in Novosibirsk region in June - September 2020. The value of the range of daily variations in stem diameter, which has a close relationship to relative soil moisture, was used as an indicator of plant water stress. The source of the information is the results of measurements of soil moisture and stem diameter growth of tomato. Experiments to assess the effect of water deficit on stem parameters were carried out on a plant set out in the open ground separately from the rest. Artificial water stress conditions were created by watering once a week. Data were collected using a PM-11z phytomonitor, soil moisture and stem diameter growth sensors. The results of measurements were processed in Microsoft Office Excel program. It was found that the range of daily fluctuations of stem diameter growth depends on moisture availability. When soil moisture is below 30%, the plant experiences water stress and the range of stem diameter fluctuations increases. The maximum growth in stem diameter was observed at 7-10 a.m. and the minimum at 13-15 p.m. local time. The difference between the maximum and minimum of the daily stem diameter increase characterizes the range of the daily stem diameter difference, which correlates closely with soil moisture. The correlation coefficient between them is 0.72. The limit for the daily stem diameter difference is 0.025 mm at 30% soil moisture. If the actual value of this parameter exceeds the limit value, the irrigation system can be activated. The implementation of this approach makes it possible to automate the irrigation process and to take into account the indicator that signals water stress of the plant.

Short-term stem diameter variations in irrigated and non-irrigated stone pine (Pinus pinea L.) trees in a xeric non-native environment

Irrigation of adult stone pine trees growing in a xeric non-native habitat had positive effects not only in stem diameter growth but also in tree response to climatic variability. Stone pine is a key species from Mediterranean Europe increasingly planted in South America. The knowledge about irrigation impact on short-term stem diameter dynamics is still limited in non-native arid areas. To improve our understanding of the effect of irrigation on (1) stem diameter changes of stone pine trees in a drought-prone environment in Chile and (2) the sensitivity of the species to weather conditions. We studied daily stem diameter changes in irrigated and non-irrigated 31-year-old stone pine trees during a growing season with below average precipitation in Chile. Short-term diameter changes were recorded using high-resolution dendrometers. The detrended daily stem diameter changes, expressing tree water status, were correlated with weather variability in both irrigated and non-irrigated trees. The growth period lasted longer and the cumulative sum of daily changes increased by 130% in irrigated trees. Moreover, a similar correlation of tree water status with climatic variables was found in non-irrigated, with the exception of precipitation. Irrigation increased stone pine productivity in this xeric environment and reduced the correlations between daily stem diameter variations and local climatic variability.

Automated detection of atmospheric and soil drought stress in Ficus benjamina using stem diameter measurements and modelling

Plant stems show reversible diurnal fluctuation and irreversible growth, both related to plant water status. The reversible stem diameter shrinkage and swelling are caused by a depletion and refilling of the plant’s internal water storage pools, while irreversible growth occurs when turgor pressure exceeds a certain threshold value. For this reason, stem diameter measurements provide a useful tool to assess plant water status. In this study, the use of continuous stem diameter measurements to detect atmospheric and soil drought stress in Ficus benjamina L. was explored by assessing the deviation between measured and simulated stem diameter variations using a mechanistic stem diameter model with moving window calibration. Sap flow, either directly measured or simulated with measurements of the microclimate, was used as input to the model. Both atmospheric stress by a high vapor pressure deficit and drought stress by a reduced soil water content were detected, with the latter 2 to 3 days earlier than detection based on maximum daily shrinkage and daily growth. Therefore, comparing stem diameter measurements with model simulations shows great potential for irrigation scheduling in horticulture.

How does spatial heterogeneity affect inter‐ and intraspecific growth patterns in tundra shrubs?

Abstract Arctic and alpine ecosystems are strongly affected by rapidly changing environmental conditions, resulting in profound vegetation shifts, which are highly heterogeneous and hard to predict, yet have strong global impacts. Shrubs have been identified as a key driver of these shifts. In this study, we aim to improve the understanding of how such broad‐scale vegetation changes are locally impacted by inter‐ and intraspecific plasticity and topographically driven heterogeneity in microsite conditions. We assessed continuous stem diameter variation of three dominant tundra shrub species at daily resolution during 5 years, using high‐precision dendrometers, thus bridging the gap between classical dendroecology and plant physiology. From this data, we identified distinct growth patterns which we linked to microsite environmental drivers. The observed patterns appeared highly variable depending on site and species, strongly influenced by characteristics of the individual plant. As the main driver of this variability, we identified fine‐scale topographic complexity, causing the sampled specimens to adjust locally by developing distinct growth strategies. We found these strategies strongly related to snow‐cover variation and associated freezing and thawing. Predicted changes in winter conditions and associated snow regimes will therefore have strong effects on shrub growth and community structure, yet, these effects are highly complex and not uniform in direction. Synthesis. The ability to adapt in a heterogeneous environment appeared highly differentiated between species and closely connected to intraspecific plasticity. Here, we identified spatial variability related to local topography as a main indicator for potential future redistribution and niche shifts in response to environmental change.

The TreeTalkersCheck R package: An automatic daily routine to check physiological traits of trees in the forest

Monitoring of tree traits and tree response to the environment can be integrated with sensor technology. High-resolution monitoring requires a frequent data acquisition, that generally results in hourly measurements for the definition of daily processes, then scaled at monthly, seasonal and annual levels, by producing very large databases. The TreeTalker (TT) technology is an example of a tool for forest monitoring that measures hourly and simultaneously tree parameters and environmental variables, by collecting 1032 attributes per tree per day (43 variables, such as sap flow and stem diameter variation measured every hour). Therefore, we present the TreeTalkersCheck R package built to facilitate the remote checking of the functioning of the TreeTalkers devices. This package contains functions to download, process raw data obtained with TreeTalker devices, and produces a report with all the alerts detected and a complete database with preliminary processing of the data. The package was tested on a database obtained by 60 TT installed on 60 trees in three sites in Tuscany (Central Italy).

Signal Intensity of Stem Diameter Variation for the Diagnosis of Drip Irrigation Water Deficit in Grapevine

Precise irrigation management of grapevines in greenhouses requires a reliable method to easily quantify and monitor the grapevine water status to enable effective manipulation of the water stress of the plants. This study describes a study on stem diameter variations of grapevine planted in a greenhouse in the semi-arid area of Northwest China. In order to determine the applicability of signal intensity of stem diameter variation to evaluate the water status of grapevine and soil. The results showed that the relative variation curve of the grapevine stem diameter from the vegetative stage to the fruit expansion stage showed an overall increasing trend. The correlations of MDS (maximum daily shrinkage) and DI (daily increase) with meteorological factors were significant (p < 0.05), and the correlations with SWP, RWC and soil moisture were weak. Although MDS and DI can diagnose grapevine water status in time, SIMDS and SIDI have the advantages of sensitivity and signal intensity compared with other indicators. Compared with MDS and DI, the R2 values of the regression equations of SIMDS and SIDI with SWP and RWC were high, and the correlation reached a very significant level (p < 0.01). Thus, SIMDS and SIDI are more suitable for the diagnosis of grapevine water status. The SIMDS peaked at the fruit expansion stage, reaching 0.957–1.384. The signal-to-noise ratio of SIDI was higher than that of MDS across the three treatments at the vegetative stage. The value and signal-to-noise ratio of SIDI at the flowering stage were similar to those of SIMDS, while the correlation between SIDI and the soil moisture content was higher than that of SIMDS. It can be concluded that that SIDI is suitable as an indicator of water status of grapevine and soil during the vegetative and flowering stages. In addition, the signal-to-noise ratio of SIMDS during the fruit expansion and mature stages was significantly higher than that of SIDI. Therefore, SIMDS is suitable as an indicator of the moisture status of grapevine and soil during the fruit expansion and mature stages. In general, SIMDS and SIDI were very good predictors of the plant water status during the growth stage and their continuous recording offers the promising possibility of their use in automatic irrigation scheduling in grapevine.

Dendrometer measurements of arctic-alpine dwarf shrubs and micro-environmental drivers of plant growth - Dataset from long-term alpine ecosystem research in central Norway

Here, we present fine-scale measurements of stem diameter variation from three common arctic-alpine dwarf-shrub species monitored in two mountain regions of Central Norway. All three species (Betula nana, Empetrum nigrum ssp. hermaphroditum, and Phyllodoce caerulea) are abundant within the studied regions and highly important contributors to potential future arctic-alpine vegetation shifts. A profound understanding of their radial growth patterns therefore has the potential to yield crucial information regarding climate-growth relations within these ecosystems. We used high-resolution dendrometers (type DRO) to monitor 120 specimens, taking measurements near the shoot base of one major horizontal stem. Along with the shrub growth measurements, we measured on-site micro-environmental data at each studied site, including shoot zone and root zone temperatures as well as soil moisture. All data were recorded at an hourly scale and are presented as daily mean values. The monitoring period spanned five full years (2015 - 2019), with additional data from 2014 and 2020. Data were collected within one of the most continental climate regions of Europe, the Vågå/Innlandet region, and in the oceanic climate region Geiranger/Møre og Romsdal, spanning a steep climate gradient over just ~100 km horizontal distance. Both study regions are characterized by steep elevational gradients and highly heterogeneous micro-topography. The studied sites were chosen to represent these natural conditions using the transect principle. The collection of our original data is subject of our long-term alpine ecosystem monitoring program since 1991, from which numerous publications function as the basis for a recent project on the use of dendrometer data in alpine ecosystem studies.

In-situ and non-invasive measurement of stem water content of trees using an innovative interdigitated-electrodes dielectric sensor less susceptible to stem diameter variation

Stem water content (StWC) of plants is an important parameter for assessing plant response to drought stress in arid and semi-arid areas and for irrigation scheduling. The measurement accuracies of in-situ non-invasive approaches are degraded by plant growth and by diurnal changes in stem diameter associated with water content. Here we develop a frequency-domain (FD) dielectric sensor operating at 100 MHz with an innovative interdigitated-electrodes (IE) probe design for measuring StWC. We characterize the performance of the IE sensor and compare it with a previously described pair-strap-ring-electrodes (2RE) FD sensor. Simulations and experimental measurements were conducted to assess the electric field distribution and volume of sensitivity (VOS) of each probe, the sensitivity of each probe to stem diameter and the accuracy of each sensor for determining StWC of three apple trees in a greenhouse environment. The simulation analysis and the measurement showed that the IE probe has a smaller but denser VOS than the 2RE probe. The sensitivity test showed that the new IE probe (0.85 mV mm−1, R2 = 0.7108) was less susceptible to stem diameter variation in comparison with the 2RE probe (32.83 mV mm−1, R2 = 0.9977). The observations in the greenhouse showed that the three apple trees (AT-1, AT-2 and AT-3) experienced a daily dehydration-rehydration cycle and the averaged midnight-to-predawn StWC gradually decreased without irrigation. According to the reference values of the maximum daily trunk shrinkage (MDS) reported by a previous study, both AT-2 and AT-3 may experience water deficit before the irrigation. Besides, the stem diameter variation decreased the measurement accuracy of 2RE sensor to be ~0.0410 cm3 cm−3 mm−1. The stronger electric field intensity of the IE probe and its less susceptible to stem diameter variation make the new IE dielectric sensor an improved method for accurate in-situ measurement of diurnal stem water content.

Towards Silviculture Guidelines to Produce Large-Sized Silver Birch (Betula pendula Roth) Logs in Western Europe

Forest health problems arising from climate change, pests and pathogens are a threat to the main timber tree species. As a result, silver birch (Betula pendula Roth) has become a precious asset for meeting oncoming forestry challenges in western Europe. However, silviculture guidelines to produce high-value birch logs in this region are lacking. Producing large-sized birch trunks requires crown release, i.e., removing crown competitors around selected target trees. These interventions are currently seldom carried out or else too late when the growth potential of the trees has already diminished. This study set out to ascertain the diameter at breast height (dbh) that could be reached by crown-released birch, determine dbh-associated crown diameters, and further characterize the gain obtained from early crown release on birch dbh growth. We measured 704 birch trees that had undergone crown release in 38 naturally regenerated pure birch stands in southern Belgium and in northeastern France. We then evaluated the variation in stem and crown diameter, and analyzed increments in response to the earliness of the interventions in three subsamples, also compared with control target birch. We found that trees with a dbh of 50 cm could be grown within 60 years. Based on crown diameter, to produce 40, 50 and 60 cm dbh trunk, the distance required between target birch trees at the end of the rotation was around 8, 10 and 12 m. With no intervention and in ordinary dense birch regenerations, the dbh increment was found to decline once the stand reached age 4–7 years. Starting crown release in stands aged 4–5 years can double the dbh increment of target trees and provide a continual gain that may last up to 20 years. When birch crowns are released after 9–12 years, it may already be too late for them to recover their best growth rate. Our contribution should help complete emerging guidelines in support of birch silviculture development.

Dynamics and influencing factors of stem diameter micro-variations during the growing season in two typical forestation species in the loess hilly region, China.

Using DC3 high-resolution dendrometer and Granier-type thermal dissipation probes, we measured stem diameter micro-variations and xylem sap flow of two typical forestation species, Quercus liaotungensis and Robinia pseudoacacia, for a growing season in the loess hilly region of China. The main environmental factors (soil water content, solar radiation, air temperature and relative humidity) were monitored. The linkage between diameter micro-variations and transpiration water use were analyzed with respect to their responses to environmental factors. The results showed that the variations in stem diameter and sap flux density of both species had obvious diurnal rhythms. The maximum daily shrinkage was positively correlated with daily sap flux density. The micro-variation of stem diameter at the daily scale was affected by transpiration during the day. The maximum daily shrinkage of stem diameter was positively correlated and well fitted with transpiration driving factors (solar radiation, vapor pressure deficit, and the integrated variable VT). The difference in slopes of regression curves suggested that the daily variation of stem diameter in Q. liaotungensis was greater and more sensitive to meteorological factors than that in R. pseudoacacia. The sap flux densities of both tree species were higher during the period with relatively higher soil water content than that with lower soil water content. The difference of maximum daily diameter shrinkage between different soil water conditions was statistically significant in Q. liaotungensis, but not in R. pseudoacacia. These differences may be related to water use strategies, including transpiration regulation and stem water replenishment.

QTL mapping of the genetic basis of stem diameter in soybean.

QTL mapping of stem diameter was carried out in three RIL populations using a high-density genetic map, and candidate genes related to stem diameter were predicted. Stem diameter is an important agronomic trait affecting soybean lodging and productivity. However, this trait is underexploited, and the underlying genetic mechanism in soybean remains unclear. In this study, three recombinant inbred line (RIL) populations, including 156 F10 lines from Nannong 94-156 × Bogao (N × B), 127 F9 lines from Dongnong 50 × Williams 82 (D × W), and 146 F9 lines from Suinong 14 × Enrei (S × E), were used to identify QTLs for soybean stem diameter across multiple environments. Phenotype analysis revealed that stem diameter exhibited strong positive correlations with plant height and 100-seed weight, two of the most important yield components. A total of 12 QTLs for stem diameter were identified on eight chromosomes across three RIL populations and five environments. The most influential QTL that was stably identified across all the populations and environments, q11, explained 12.58-26.63% of the phenotypic variation. Detection of several environment-specific QTLs, including q14, q16, and q20, suggests that environments may also have important effects in shaping the natural variation in soybean stem diameter. Furthermore, we predicted candidate genes underlying the QTLs and found that several promising candidate genes may be responsible for the variation in stem diameter in soybean. Overall, the markers/genes linked closely or underlying the major QTLs may be used for marker-assisted selection of soybean varieties to enhance lodging resistance and even yield. Our results lay the foundation for the fine mapping of stem development-related genes to reveal the molecular mechanisms.