Small Seedlings Research Articles

Assessment of Root-Shoot Ratio, Biomass, and Carbon Sequestration of Chestnut-leaved Oak Seedling (Quercus castaneifolia C. A. Mey)

One of the most important ways to reduce atmospheric carbon is the carbon sequestration by trees. Chestnut-leaved oak (Quercus castaneifolia C. A. Mey) is one of the most important native oaks of Iran distributed in the Hyrcanian Forests. The pure and mixed stands of it cover about 6.5% of these forests. In this study, carbon sequestration of chestnut-leaved oak seedlings was evaluated by using some morphological characteristics of the root and shoot. For this purpose, one hundred seedlings were sampled by method of Systematic-Random from the sowing bed on March 2022 in the Pylambra nursery at Guilan province. Seedlings are divided to three grades small, medium and large according to Root Collar Diameter (RCD). The biomass and carbon sequestration of chestnut-leaved oak seedling were calculated according to the basic density of its root and shoot. The Pearson's correlation coefficient was used for correlation detection between variables. The one-way analysis variance test at the 95% confidence level was used to recognize difference among biomass and carbon sequestration of three group of the oak seedlings. The results of correlation analysis showed that the root collar diameter (RCD) had the strongest correlation with other morphological characteristics. The amount of the basic density for the root and shoot of the oak seedling was obtained about 0.57 g/cm3 which is the same for both of them. The amount of the biomass and carbon sequestration of the root was obtained more than shoot at the small and medium seedlings, whereas in large seedling was the same. In general, by increasing the size of seedling the biomass and carbon sequestration increased.

Differential Symptomology, Susceptibility, and Titer Dynamics Manifested by Phytoplasma-Infected Periwinkle and Tomato Plants.

Phytoplasmas are intracellular pathogenic bacteria that infect a wide range of plant species, including agriculturally important crops and ornamental trees. However, our understanding of the relationship between symptom severity, disease progression, and phytoplasma concentration remains limited due to the inability to inoculate phytoplasmas mechanically into new plant hosts. The present study investigated phytoplasma titer dynamics and symptom development in periwinkle and tomato, both infected with the same potato purple top (PPT) phytoplasma strain using a small seedling grafting approach. Virescence, phyllody, and witches'-broom (WB) symptoms sequentially developed in periwinkle, while in tomato plants, big bud (BB, a form of phyllody), cauliflower-like inflorescence (CLI), and WB appeared in order. Results from quantitative polymerase chain reaction (qPCR) targeting the PPT phytoplasma's 16S rRNA gene revealed that in both host species, phytoplasma titers differed significantly at different infection stages. Notably, the highest phytoplasma concentration in periwinkles was observed in samples displaying phyllody symptoms, whereas in tomatoes, the titer peaked at the BB stage. Western blot analysis, utilizing an antibody specific to PPT phytoplasma, confirmed substantial phytoplasma presence in samples displaying phyllody and BB symptoms, consistent with the qPCR results. These findings challenge the conventional understanding that phytoplasma infection dynamics result in a higher titer at later stages, such as WB (excessive vegetative growth), rather than in the early stage, such as phyllody (abnormal reproductive growth). Furthermore, the PPT phytoplasma titer was markedly higher in periwinkles than in tomato plants, indicating differing susceptibilities between the hosts. This study reveals distinct host responses to PPT phytoplasma infection, providing valuable insights into phytoplasma titer dynamics and symptom development, with implications for the future management of agricultural disease.

Design and test of walk-type rice potted seedling transplanting machine

At present, rice potted seedling transplanting machine is mostly suitable for high-speed, large seedlings and large plant distance rice transplanting. In order to adapt to the transplanting of different types of rice potted seedlings, this study carried out theoretical research and institutional design for transplanting rice potted seedlings suitable for small seedlings and small plant spacing. A 2R open-chain rice potted seedling transplanting mechanism with two non-circular gears meshing to achieve the ideal transplanting posture was developed, and an optimization software for potted seedling transplanting was developed by establishing the kinematic model of the transplanting mechanism, which simulated the motion trajectory and attitude of the transplanting arm during the transplanting process. Through the optimization of the optimization design software parameters, a set of parameters that meet the requirements of transplanting rice potted seedlings in the rear insert rice potted are obtained, a transplanting mechanism suitable for walking rice potted seedling transplanting machine is designed and developed, and the experiments of rice potted seedling picking, conveying and planting are completed. The success rate of the designed walk-type rice potted seedling transplanting mechanism on the bench was 96.7%, and the qualification rate of the whole machine transplanting test was 89.1%.

Side-effects of laser weeding: quantifying off-target risks to earthworms (Enchytraeids) and insects (Tenebrio molitor and Adalia bipunctata)

With challenges posed by chemical and mechanical weed control, there are now several research and commercial projects underway to develop autonomous vehicles equipped with lasers to control weeds in field crops. Recognition systems based on artificial intelligence have been developed to locate and identify small weed seedlings, and mirrors can direct a laser beam towards the target to kill the weed with heat. Unlike chemical and mechanical weed control, laser weeding only exposes a small area of the field for the treatment. Laser weeding leaves no chemicals in the field after the treatment or does not move the soil which may harm crop roots and non-target organisms. Yet, it is well-known that laser beams can harm living organisms; the effect on the environment and fauna should be studied before laser weeding becomes a common practice. This project aimed to study the effect of laser on some living non-target organisms. We investigated the effect of laser treatment on the mortality of two species of earthworms (Enchytraeus albidus and Enchytraeus crypticus), larvae, pupas, and beetles of yellow mealworm beetles (Tenebrio molitor) and the two-spotted lady beetle (Adalia bipunctata) for increasing dosages of laser energy. In all earthworms experiments except one, the mortality rates of the worms living in the uppermost soil layer of clay, sandy, and organic soil exposed to laser heating were not significantly different from the controls even with laser dosages up to 23.8 J mm-2. Laser doses sufficient to kill plants were lethal to the insects, and lower doses that did not kill plants, killed or harmed the insects across all life stages tested. The larger beetles survived higher doses than smaller. Laser weeding is a relatively new technology and not yet widely practiced or commercialized. Therefore, we do not discuss and compare the costs of the different weeding methods at this early stage of the development of the technology.

The Effect of Hydrocarbon Pollution on Niger Delta Root Crops: A Case Study of Cocoyam [Colocasia Esculenta

This paper investigates effects of re-occurring oil spillages on cocoyam, Colocasia esculenta (L.). It studies changes in petiole lengths, leaf blades, chlorophyll concentrations in leaves, and PAH and BTEX concentrations in tubers for three generations under diverse conditions. 8 10-gallon grow bags were used: Grow bags 5–8 were treated with a controlled quantity (4 L/cubic metre) of liquid crude hydrocarbon in the months of June 2019–2021; with 2 replications, after a 2-3-day interval within a week. In grow bags 3, 4, 7, and 8, poultry manure were applied once in 2 months after small seedlings emerged from soil surfaces. Grow bags 1 and 2, 3, and 4 served as “controls” for non-contaminated growth. Grow bags 7 and 8 were treated with hydrocarbons and poultry manure. In the first generation, coco yams planted in grow bags 7-8 showed growth responses (average values of 1.04 m, 51 cm, 4.45 mg/g for petiole length, leaf blade length, and chlorophyll concentration, respectively) very similar to coco yams planted in pristine soil with poultry manure with average values of 1.00 m, 50 cm, 3.45 mg/g. The cocoyams planted in pristine organic rich soils showed similar response with or without fertilizers (average values of 0.98 m, 48 cm 1.83mg/g and 1.00m, 50 cm, 3.45mg/g) with progressively smaller leaves as generation increases. The cocoyams in hydrocarbon impacted soils generally perform poorer than uncontaminated soil with or without poultry manure by the second and third generation. Poultry manure on soils with re-occurring hydrocarbon contamination exacerbates soil weakening. Mean PAH and mean BTEX concentrations in tubers were 0.001-0.0035 mg/kg and <0.001mg/kg respectively. Cocoyams are not strong BTEX bioactive scavenger but gradually became more concentrated in PAH.

Effect of Foliar Application of Macro and Micronutrients on Quality Seedlings Production in Small Cardamom (Elettaria cardamomum Maton.)

An experiment was carried out to assess the effect of foliar nutrition with macro and micronutrients on quality seedlings production in small cardamom seedlings in the secondary nursery at ZAHRS, Mudigere with seven treatments and three replications in Completely Randomized Design during the year 2020-21. The results of study revealed that, among the different treatments studied, combined application of macro and micro nutrients (19:19:19 @ 0.50%+ MgSO4 @ 0.25%+ ZnSO4 @ 0.25 %+ Borax @ 0.25 %) thrice at monthly intervals after 30 days of transplanting in the secondary nursery recorded significantly maximum pseudostem height (56.07 cm), number of leaves (7.26), leaf area (646.90 cm2), leaf area index (5.24), total chlorophyll content (1.68), number of primary (13.66) and secondary roots (76.85), root length (41.40), root thickness (1.58), root volume (17.88 cc), total dry matter production (5.61 g), tillering percentage (25.43), Dickson quality index (1.56) and volume index (259.87) at 120 days after treatment. The nutrient status of the nursery media revealed that, the available nitrogen (318.00 kg/ha), phosphorus (27.50 kg/ha) and potash (230.00 kg/ha). The analysis of plant nutrients at 120 days after treatment revealed that, the higher nitrogen (2.72 %), phosphorus (0.20 %) and potassium (3.90 %) were also recorded maximum with combined spray with macro and micronutrients. Hence, combined application of foliar nutrients proved to be the best application than either single spray or combination of two and uninoculated for raising quality seedlings in cardamom.

Secondary invasion by an invasive shrub limits native tree seedling growth in a size‐dependent manner following the eradication of a different invasive species in an island ecosystem

Following the control of an invasive tree species, native forest ecosystem restoration can be prevented by a secondary invasion by another invasive species that inhibits the reestablishment of native trees. In this study, we evaluated the effects of the invasive shrub Leucaena leucocephala on the initial growth of planted seedlings of four native tree species (Pandanus boninensis, Rhaphiolepis indica, Schima mertensiana, and Terminalia catappa) after eradication of the invasive tree Casuarina equisetifolia in the Ogasawara Islands in the northwestern Pacific Ocean. In a 24‐month field experiment, we compared the sizes of planted seedlings (diameter at ground level, height, and leaf number) among four treatments in a 2 × 2 design of initial seedling size (large vs. small) × L. leucocephala invasion (sowing L. leucocephala seeds vs. control). More than 75% of the seedlings (excluding S. mertensiana) survived regardless of the treatments. For all four species, initially large seedlings tended to become larger plants at the end of the experiment than initially small seedlings. We detected significant effects of L. leucocephala invasion on one or more plant size parameters in all four species. Seedlings grown in L. leucocephala invasion quadrats were smaller than those in control quadrats at the end of the experiment. We detected significant interactions between initial seedling sizes and L. leucocephala invasion for three species. Together, these results indicate that secondary invasion by L. leucocephala after controlling C. equisetifolia inhibits the initial growth of native tree seedlings, depending on their size at the time of invasion.

Aptness of Seedling Age of Important Avenue Woody Species of Uttar Pradesh, India

Trees are an important component of our ecosystem, as far as ecological services provided by them are concerned. Especially in urban ecology, their role becomes more significant where they mitigate negative impacts of urbanization like deforestation; loss of wetlands; acquirement of agricultural lands; loss of biodiversity due to habitat clearing; degradation and fragmentation of the landscapes, etc. Trees make urban areas more resilient to these adverse impacts. Avenue plantation is an important part of Urban Forestry. In Avenue plantation, mostly tall seedlings are used. But planting very tall seedlings may affect the secondary growth of the tree, whereas planting small seedlings may be grazed by the animals. It is very important that the planting stock must be able of high rates of survival and good field performance to justify the expense of reforestation efforts. Therefore the present study is focused on the suitable planting age of some important preferred tree species of the Uttar Pradesh Forest Department and their growth performance in field conditions. The selected tree species were Shisham (Dalbergia sissoo), Imli (Tamarindus indica) Kathal (Artocarpus heterophyllus), Jungle Jalebi (Pithecellobium dulce), Kat sagaun (Haplophragma adenophyllum) and Karanj (Pongamia pinnata). These are the major woody species presently being planted in urban forestry. The species with large crown are planted in government garden, city garden, etc. Different age groups of these tree species were planted and their growth performance was studied under different field conditions. Aptness and importance of seedling age were recommended for studied trees for avenue plantation. It was concluded that species like Jungle Jalebi (Pithecellobium dulce), Katsagaun (Haplophragma adenophyllum), and Shisham (Dalbergia sissoo ) seedlings performed well for one year old age as well as for two year old age ones but species like Karanj( Pongamia pinnata), Imli ( Tamarindus indica ) and Kathal (Artocarpus heterophyllus), performed well more for one year old seedling. Therefore all these may be planted after one year of age in nursery to avoid the extra expense of maintaining these seedlings in the nursery stage.

Warming adversely affects density but not growth of balsam fir regeneration across a climatic gradient in the Acadian Forest Region of eastern Canada

Balsam fir ( Abies balsamea (L.) Mill.) is projected to decline in the Acadian Forest Region under climate change. We hypothesized that along a 700 km latitudinal gradient with increasing mean annual temperature from New Brunswick to Nova Scotia, Canada, balsam fir regeneration density and growth rates would (1) decline with warming and (2) decline more in immature than in mature stands due to greater exposure to adverse climate conditions. Regeneration density, height growth, and lateral branch growth were measured in 30 mature and 28 immature plots and related to climate and stand variables using generalized additive models. Balsam fir regeneration density was negatively affected by increased mean annual temperature and increased with summer precipitation, supporting our first hypothesis, but varied by height class. Canopy cover significantly affected seedling density, but its effect varied by substrate type (coniferous litter and dry moss litter), with seedling density being greatest under low canopy cover for large seedlings and greatest at intermediate canopy cover for small seedlings. Seedling growth rates were determined by height class, canopy cover, precipitation, and coniferous litter cover. Stand maturity did not significantly affect fir regeneration density or growth rates. Our results indicate that over time, increasing mean annual temperature may reduce balsam fir regeneration density within the Acadian Forest Region, while the marginal summer precipitation increases may lead to small gains in growth.

Use of sulphur in bareroot pine and hardwood nurseries

During the 20th century, managers at sandy nurseries utilized sulphur (S) to lower soil pH and mitigate the risk of iron deficiency. During that time, however, applying S as a fertilizer was a rare event. At many nurseries, S in rain and irrigation water was sufficient to avoid visual deficiency symptoms. The S status of soil and foliage was typically unknown, and many researchers did not test for S due to the additional cost. Consequently, S became the most neglected macronutrient. While a few nursery trials demonstrated that elemental S reduced damping-off and increased height growth, a majority showed no benefit after applying S at rates lower than 100 kg ha-1. Even so, by 1980, S-deficiencies occurred at bareroot nurseries in Alabama, Oklahoma, Virginia, Wisconsin, the United Kingdom, and likely in North Dakota and New York. The risk of a deficiency increases when N-only fertilizers are applied to seedbeds. Due to research, experience and the precautionary principle, several managers transitioned to using ammonium sulfate instead of, less expensive, N-only nitrogen fertilizers. After soil tests became affordable, managers began to ask questions about the need to apply S to seedbeds.
 Only a few hydroponic trials with small pine seedlings have been used to estimate “threshold” or “critical values” for foliar S. Since an initial 1,500 μg g-1 S value is “unreliable” for pine seedlings, some authors lowered the value to 1,100 μg g-1 and even as low as 500 μg g-1 S. Others ignore all estimates based on total S concentrations and, instead, monitor only foliar SO4 levels.

Shedding light on a hot topic: Tuberisation in potato

AbstractGrowing small seedling tubers from true seed, comparable with mini tubers, in controlled conditions could be a method to multiply healthy starting material of potato. In indoor farming systems, the conditions can be optimised for high production. In field trials, it is impossible to investigate the effects of environmental factors such as temperature and light separately. In this study, we performed three climate room experiments in which the effects of light intensity, temperature and percentage of far‐red light in the light spectrum on tuber production were assessed. We found that increasing the average temperature reduced tuber number and tuber weight. Increasing the diurnal temperature variation while keeping the average temperature equal resulted in increased tuber size. The light treatments on the other hand only affected the number of tubers per plant: increasing light intensity and increasing the percentage of far‐red light in the spectrum enhanced the number of tubers. Moreover, interaction in tuber production between inbred lines and temperature was significant, with some inbred lines being relatively tolerant to high temperature. These findings will help breed for heat tolerant varieties and optimise growing conditions for tuber production in indoor farming systems.

Performance of Drift-Reducing Nozzles in Controlling Small Weed Seedlings with Contact Herbicides

In many EU countries, spray applications should comply with increasingly stringent requirements regarding the drift reduction class of spray nozzles. Many farmers fear that the use of drift-reducing nozzles producing coarse droplet spectra may compromise the performance of contact herbicides on small weed targets. This study examined the effects of various ISO 03 drift-reducing flat-fan nozzles (pre-orifice and single and dual flat-fan air induction nozzles) differing in spray drift reduction class and spray pressure (2.5 bar, 5.0 bar) on (1) spray coverage, (2) droplet characteristics and (3) efficiency of contact herbicides bentazon and phenmedipham against cotyledon and 2-leaf stage plants of Chenopodium album and Solanum nigrum. Performance was compared to that of an ISO 03 standard flat-fan nozzle producing a finer droplet size spectrum. All sprayings were performed at a spray volume of 200 L ha−1. In most dose–response experiments, several drift-reducing flat-fan nozzles performed equally well as standard flat-fan nozzles, regardless of herbicide, spray pressure, growth stage or weed species. However, droplet size spectra of air-induction nozzles were too coarse for an adequate spray coverage and efficient application of contact herbicides on cotyledon stage plants of S. nigrum. In addition, the performance of air-induction nozzles in controlling difficult-to-wet C. album weeds with phenmedipham was better at 5.0 bar than at 2.5 bar. In contrast with droplet size characteristics, spray coverage characteristics determined on water sensitive papers were not good proxies for estimating the biological efficiency of contact herbicides. Air induction nozzles at 5.0 bar allow efficient control of 2-leaf targets, but nozzles emitting finer droplet spectra, such as pre-orifice nozzles, should be preferred for controlling cotyledon stage weeds at low-herbicide doses.

Distance and density dependence in two native Bornean dipterocarp species.

The Janzen-Connell hypothesis proposes that density and distance-dependent mortality generated by specialist natural enemies prevent competitive dominance. Much literature on Janzen-Connell mechanisms comes from the neotropics, and evidence of the role of distance and density-dependence is still relatively sparse. We tested the predictions of the Janzen-Connell hypothesis in a South-East Asian system dominated by mast fruiting species. We hypothesized that seedling survival would decrease with distance and density, seedling growth would increase, and herbivory would decrease, according to the predictions of the Janzen-Connell hypothesis. Experiments were conducted to determine the strength of the Janzen-Connell mechanism by manipulating the density and identity of tree species as a function of the distance from parent trees. Survival of conspecific seedlings was reduced near adult trees of one species, but not another. High densities of seedlings decreased the growth of conspecific seedlings of both species. In both species, herbivory rates decreased with distance in low-density areas. This study indicates that dipterocarp species experienced weak Janzen-Connell effects of distance and density dependence at the growth stage studied. Future studies in this system might focus on earlier life-history stages such as seeds and small seedlings, as well as studying mortality during mast-seeding events.

Escape Game: Responses of Northern White Cedar (Thuja occidentalis L.) to an Extreme Reduction in White-Tailed Deer (Odocoileus virginianus Zimmerman) Population

Northern white cedar (Thuja occidentalis L.) is a species of high ecological and economic value whose abundance has been declining since the pre-industrial period. It is an important element of white-tailed deer (Odocoileus virginianus Zimmerman) habitat, but its regeneration can be compromised by excessive browsing. This situation is especially critical in deeryards, where deer concentrate during winter. In 2018 and 2019, deer culling operations were carried out by the Ministry of Forests, Wildlife and Parks of Québec over 400 km2 in response to the occurrence of chronic wasting disease cases on a red deer farm. This operation offered an opportunity to look at how variations in deer pressure influence cedar regeneration and how cedar responds to a sudden reduction in browsing. We conducted regeneration surveys within and outside mapped deeryards both in the deer reduction zone and in a control zone. We performed dendrochronological analyses of cedar seedlings and saplings to quantify radial growth response to a reduction in browsing pressure. The results show that cedar basal area influences the abundance of small seedlings but that the effect of browsing becomes dominant for seedlings taller than 50 cm. Cedar growth responds to a reduction in browsing, but a two-year period was not sufficient to translate into changes in regeneration structure. The duration of the windows of opportunity at low browsing pressure required for cedar to reach a safe height remains to be determined. However, canopy openness had a significant influence on growth, suggesting that silvicultural measures could be taken to shorten the period of vulnerability to deer browsing.

Survival on land: A dark-grown seedling searching for path.

To initiate its development into a plant, a small dark-grown seedling (prior to its emergence from the ground) must penetrate through the growth media. The path that the seedling takes during this journey has yet to be explained. As such, we conducted non-destructive tests using CT scans to observe the growth of dark-grown seedlings in soil over time; we also developed a model to simulate the dynamics of an emerging seedling, and to examine effects of various growth medium conditions, including Lunar soil. It was previously postulated that, with gravitropism in a terrestrial growth medium, a dark-grown seedling would grow directly upright. However, our CT scan results showed that dark-grown soybean seedlings departed from the vertical path in soil, as far as a lateral distance of approximately 10mm. The phenomenon of the non-straight path was also demonstrated by the model results. Through simulations, we found that an emerging seedling naturally weaves through the particles of growth medium, in search for the path of least resistance. As a result, the seedling ends up travelling a longer distance. Compared with a seedling that was artificially forced to take a straight path in a growth media, the seedling taking the natural path encountered significantly lower resistances (20% lower) from the growth medium, while travelled 12% longer distance during the emergence process. A seedling encountered a much higher impedance in Lunar soil. Our results suggest that taking the path of least resistance, in addition to shaping and orientating itself for mechanical advantage, are strategies evolved by plant species that have contributed to its vast success. An understanding of plant behavior and survival strategies on Earth lay the foundation for future research in agriculture in novel environments, including on celestial bodies.

Plant height determines phenological variation in Quercus suber L.

Phenological traits of vegetative apical buds were monitored in a Quercus suber L. (cork oak) montado near Lisbon during 2015. Natural regeneration plants, growing at a fenced plot, and mature trees (MT) from the surrounding montado were selected and divided in six groups (n=8) according to height (H): Sd1 (small seedlings, H<0.1 m); Sd2 (seedlings, 0.1<H<0.5 m); Sp (saplings, 1<H<2 m); Jv1 (small juveniles, 3<H<6 m); Jv2 (juveniles, H>6 m); MT (mature trees). Observations included budburst date, apical shoot elongation and leaf production. Vegetative phenology patterns of Q. suber changed according to height/age group. Average budburst dates occurred between early-April (day 99, Sd1) and mid-May (after day 120, mature and juvenile trees), at day lengths between 12.8 (Sd1) and 13.7 hours (Jv2). Height was positively related with average budburst dates, degree day sums and daylength at budburst. Shoot elongation followed different patterns according to size/age group. In seedlings, cumulative growth was smaller and restricted to the weeks immediately after budburst, whilst taller/older trees phenological patterns were more variable, with vegetative growth often maintained until mid-summer. The differences in budburst timing and vegetative growth patterns may be reflecting the different strategies to cope with resource limitation and maximize the length of the growing season among groups.

Model-based estimation of the leaf area of ozone-indicator tobacco (Nicotiana tabacum L.) plants under ambient ozone conditions

Bel-W3 is an ozone-sensitive tobacco (Nicotiana tabacum L.) cultivar widely used worldwide for ozone biomonitoring. Despite its extensive use, there is no comprehensive predictive model to non-destructively estimate the leaf area using only a common ruler, yet leaf area is a major evaluative trait in plants under ozone stress and of economic value in tobacco plants. In this method, we aimed at developing a predictive model to estimate leaf area using the product between leaf length and leaf width. To this end, we conducted a field experiment with ground-grown Bel-W3 plants treated with different solutions under ambient ozone conditions. The solutions were water, the antiozonant ethylenediurea (EDU; 500 ppm), and the antitranspirant pinolene (Vapor Gard; 1%, 5%, 10%). The chemical treatments were introduced to enhance leaves pool and capture different conditions that can occur in ozone biomonitoring projects.•A simple linear predictive model was developed and validated using data from a previous chamber experiment with small seedlings.•Overestimation of the model led to the integration of data from both experiments and development of another simple linear predictive model.•This integrated model provides improved estimation of leaf area and can be used for representative estimation of the area of Bel-W3 leaves of any sizes.

Use of calcium in bareroot pine nurseries

Bareroot nursery managers may apply dolomite, gypsum, or Ca-nitrate to increase Ca in nursery soils. Although a few managers follow S.A. Wilde’s recommendations and maintain soil at levels of 500 to 1,000 μg g-1 Ca, there is no need to keep Ca levels this high. In contrast, managers at sandy nurseries apply Ca when soil tests drop below 200 μg g-1 Ca. In fact, acceptable pine seedlings have been produced in irrigated soil with <100 μg g-1 available Ca. In plantations, asymptomatic wildlings grow when topsoil contains 17 μg g-1 Ca. In sandy soils, applying too much gypsum can result in a temporary Mg deficiency and too much lime will result in chlorotic needles.
 Managers apply Ca when foliar levels fall below a published “critical value.” The belief that the critical value for Ca varies by stock type is not valid. In fact, numerous “critical” values are invalid since they were not determined using growth response curves. Critical values determined for small seedlings using CaCl2 in sand are apparently not valid for use in bareroot nurseries. 
 At bareroot nurseries, the soil extractable Ca level can decline during a year by 30 μg g-1 or more. Harvesting 1.7 million pine seedlings may remove 20 kg ha-1 of Ca but irrigation can replace this amount or more. When water contains 5 mg l-1 Ca, 600 mm of irrigation will add 30 kg ha-1 Ca. In some areas, 1,000 mm of rainfall will supply 7 kg ha-1 Ca. Even when a Mehlich 1 test shows no exchangeable Ca in the topsoil, pine needles on tall trees may exceed 2,000 μg g-1 Ca due to root growth in subsoil.
 There are few documented cases of deficient pine needles (<300 μg g-1 Ca) in irrigated nurseries in Australia, New Zealand, Scotland and in the Americas. Even when soil fumigation delays the inoculation of ectomycorrhiza, bareroot pines have adequate levels of Ca. Typically, foliage samples from pine nurseries contain at least 1,000 μg g-1 Ca. Samples from 9-month-old seedlings range from 300 to 11,000 μg g-1 Ca. Although the “critical value” for Pinus echinata foliage is not known, 1-0 seedlings with 300 μg g-1 Ca were not stunted and apparently grew well after ouplanting.

Ontogenetic changes in root and shoot respiration, fresh mass and surface area of Fagus crenata.

To date, studies on terrestrial plant ecology and evolution have focused primarily on the trade-off patterns in the allocation of metabolic production to roots and shoots in individual plants and the scaling of whole-plant respiration. However, few empirical studies have investigated the root : shoot ratio by considering scaling whole-plant respiration at various sizes throughout ontogeny. Here, using a whole-plant chamber system, we measured the respiration rates, fresh mass and surface area of entire roots and shoots from 377 Fagus crenata individuals, from germinating seeds to mature trees, collected from five different Japanese provenances. Non-linear regression analysis was performed for scaling of root and shoot respiration, fresh mass and surface area with body size. Whole-plant respiration increased rapidly in germinating seeds. In the seedling to mature tree size range, the scaling of whole-plant respiration to whole-plant fresh mass was expressed as a linear trend on the log-log coordinates (exponent slightly greater than 0.75). In the same body size range, root and shoot respiration vs. whole-plant fresh mass were modelled by upward-convex (exponent decreased from 2.35 to 0.638) and downward-convex trends (exponent increased from -0.918 to 0.864), respectively. The root fraction in whole-plant respiration, fresh mass and surface area shifted continuously throughout ontogeny, increasing in smaller seedlings during early growth stages and decreasing in larger trees. Our results suggest a gradual shift in allocation priorities of metabolic energy from roots in seedlings to shoots in mature trees, providing insights into how roots contribute to shoot and whole-plant growth during ontogeny. The models of root : shoot ratio in relation to whole-plant physiology could be applied in tree growth modelling, and in linking the different levels of ecological phenomena, from individuals to ecosystems.

Increasing the utility of tree regeneration inventories: Linking seedling abundance to sapling recruitment

Tree regeneration surveys provide insight into potential forest change and trajectories of stand development, which can guide management in an era of global change. However, most tree regeneration surveys tend to be coarse and/or rapid assessments which can introduce considerable uncertainty into translating estimates of seedling abundance into models of sapling recruitment and subsequent overstory tree abundance and composition. Observations of seedling abundance changes across size classes may be essential to accurately predicting recruitment from seedling sized trees to advanced size classes, which is fundamental to informing our understanding of future forest composition and dynamics. Using the USDA Forest Service’s Forest Inventory and Analysis (FIA) program’s Regeneration Indicator (RI) dataset, in which seedlings are monitored by six height classes, we developed Boosted Regression Tree models to predict presence of sapling recruitment for five common, north temperate and boreal tree species as a function of seedling abundance by height class and site/stand factors. Models using the six RI seedling height classes were compared to models using the single seedling size class as commonly surveyed by programs such as FIA. Use of seedling height classes improved models for all species. Seedlings > 1.5 m tall were the most influential predictors of recruitment for each species while seedlings in classes < 1.5 m tall were either removed entirely from models or had low relative influence (<8%). Seedlings < 0.3 m tall had both positive and negative relationships with sapling recruitment depending on species, suggesting that abundances of small seedlings should be interpreted cautiously. This approach demonstrates the importance of collecting relatively coarse seedling height data during regeneration surveys with potential application to other regions and scenarios to expand the utility of tree regeneration surveys to predict future forest dynamics.