Basal Stem Diameter Research Articles

Chronosequence-based population structure and natural regeneration of Haloxylon ammodendron plantation in the southern edge of the Gurbantunggut Desert, Northwestern China

In the Gurbantunggut Desert of Northwestern China, we surveyed the population structure and regeneration characteristics of six Haloxylon ammodendron plantations based on chronosequencing. The results showed that the age class of an individual H. ammodendron plant from youngest to oldest showed growth potential under the present environment. The optimal termination stage of H. ammodendron occurred at 20 years of age, which was accompanied by a regeneration phase at 17 years. The H. ammodendron plantations started to regenerate after 7 years. The maximal height and basal stem diameter of a grade III seedling reached 1.2 m and 1.9 cm in a 17-year-old plantation. In a 33-year-old plantation, the transformation rate of the seedling from grade I to grade III increased up to 92.3%. Although the seedling bank was plentiful in the plantations, the replenishment of the canopy was not continuous and timely. Therefore, measures to further the stability and sustainability of H. ammodendron plantation were necessary.

Computation of coupled effects of root and shoot characteristics on transpiration based on optimization approach

PurposeWater balance is measured by transpiration, which has a significant impact on the performance of geotechnical infrastructure (vegetated slopes), ecological infrastructure (wetlands), urban infrastructure (green roof, biofiltration units) and agricultural infrastructure. Past studies have formulated models using analytical modeling to evaluate the transpiration index based on energy balance and suction. In circumstance of impartial and uncertain information about the root and shoot properties and its effect on the transpiration index, the present work aims to introduce the new optimization algorithm of genetic programming (GP) to quantify and optimize the transpiration index of plant.Design/methodology/approachThe GP framework, having objective function of structural risk minimization, is used for formulating the transpiration index model. The statistical metrics with 2D and 3D analyses of the models are conducted to determine its accuracy and understand the transpiration process.FindingsThe model analysis reveals that the proposed model extrapolates the transpiration index values accurately based on five inputs. 2D and 3D relationships between the transpiration index and the five inputs suggest that the total root area has the highest impact on the transpiration index followed by shoot length and root biomass. There is not much impact of the shoot mass and stem basal diameter on the transpiration index. It was also found that the transpiration index increases with an increase in total root area and root biomass.Originality/valueThis work is a first-of-its-kind study involving the extensive computation analysis for quantifying and optimizing the transpiration index of the soil for the complex civil systems.

Walnut Twig Beetle (Coleoptera: Curculionidae: Scolytinae) Colonization of Eastern Black Walnut Nursery Trees.

Thousand cankers disease, caused by the invasive bark beetle Pityophthorus juglandis Blackman and an associated fungal pathogen Geosmithia morbida M.Kolařík, E. Freeland, C. Utley, N. Tisserat, currently threatens the health of eastern black walnut (Juglans nigra L.) in North America. Both the beetle and pathogen have expanded beyond their native range via transport of infested walnut wood. Geosmithia morbida can develop in seedlings following inoculation, but the ability of P. juglandis to colonize young, small diameter trees has not been investigated. This study assessed the beetle’s colonization behavior on J. nigra nursery trees. Beetles were caged directly onto the stems of walnut seedlings from five nursery sources representing a range of basal stem diameter classes. Seedlings were also exposed to P. juglandis in a limited choice, field-based experiment comparing pheromone-baited and unbaited stems. When beetles were caged directly onto stems, they probed and attempted to colonize seedlings across the range of diameters and across sources tested, including stems as small as 0.5 cm in diameter. In the field experiment, beetles only attempted to colonize seedlings that were baited with a pheromone lure and appeared to prefer (though not statistically significant) the larger diameter trees. Despite several successful penetrations into the phloem, there was no evidence of successful progeny development within the young trees in either experiment. Further investigation is recommended to better elucidate the risk nursery stock poses as a pathway for thousand cankers disease causal organisms.

Patterns of biomass allocation in Haloxylon persicum woodlands and their understory herbaceous layer along a groundwater depth gradient

To investigate above- and belowground biomass allocation patterns and the relationship of root distribution between different functional groups (shrubs vs. herbs) along a groundwater depth gradient, an experiment was carried out in a Haloxylon persicum woodland. Four sites were selected along the groundwater depth gradient. At each site, five sample plots (20×20m) and 15 subplots (1×1m) were established for a vegetation inventory of Haloxylon persicum and the herbaceous layer. The vegetation inventory included plant density, canopy coverage, height, and basal stem diameter of H. persicum. Allometric equations were established for H. persicum based on the biomass of 22 excavated trees, which were then applied to inventory data to provide stand estimates of aboveground biomass (AGB), belowground biomass (BGB), and total biomass (TB) of H. persicum. The AGB of the herbaceous layer was measured in subplots (1×1m) and BGB was excavated and measured to a depth of 100cm at 10-cm intervals. Our results indicated that the BGB-to-AGB ratio at the community level in the herbaceous layer increased notably along the gradient of declining groundwater depth. The depth of the soil horizon that contained 65% of the root surface area and 85% of the root biomass was shallower (0–2.5m) in the deep end of the groundwater depth gradient than in the shallow end (0–3m) of the gradient. H. persicum adjusted root distribution to capture water in the upper soil layers in response to the decline in groundwater depth. However, this adjustment was not sufficient to compensate for the decline in the water table: the BGB-to-AGB ratio showed no significant increase as AGB declined. On the contrary, herbaceous plants seemed better adapted to changes in the water table by effectively adjusting their BGB-to-AGB ratio. Use of BGB-to-AGB ratios that are specific to groundwater tables will significantly improve our estimates of BGB carbon stocks in these woodlands. Considering the scarcity of information on biomass stocks and partitioning in desert woodlands, our results might be applicable to other desert regions in Central Asia dominated by H. persicum.

Characteristics of main layer and regeneration layer of Haloxylon ammodendron plantations at different ages on the southern edge of the Gurbantunggut Desert, Northwest China

The population structure characteristics, natural regeneration, and the influential factors of Haloxylon ammodendron plantations at six different stand ages on the southern edge of the Gurbantunggut Desert were studied. The results showed that H. ammodendron plantation at the stand age of 7 could naturally regenerate. At the stand age of 17, the densities of the seedlings (＜30 cm height), saplings (30≤H＜50 height), and small trees (≥50 cm height) reached optimal class, and the mean height and base diameter of the small tress reached 1.10 m and 1.91 cm, respectively. The parent trees in H. ammodendron plantation at the stand age of 20 grew best. The height of 35% individuals grew up to 2.50-3.00 m, and the basal stem diameter of 23.1% individuals grew up to 8.00-10.00 cm. The height and diameter growth of the parent trees in H. ammodendron plantation at the stand age of 33 apparently declined, but the regeneration ability by natural seed dispersal was still strong. The regeneration density of natural seed dispersal showed the greatest correlation with the available nitrogen content in 0-100 cm soil layer (0.87), followed by the soil rapidly available phosphorus content (0.84) and the soil water content (0.79). The soils with pH 8.1-8.6 did not limit the nutrient growth of the regeneration layer. In the main stand layer, the individual density of whole regeneration layer showed the greatest correlation with the biomass of the parent trees (0.77), while the density of regeneration layer of the small trees showed the greatest correlation with the planting density (0.71) and the age of the parent trees (0.70).

English

The species, Luehea divaricata offers great ecological and timber potential in addition to a wide geographic distribution, although there are few studies comparing seedling production in the nursery with its development in the field. Therefore, this research aimed to evaluate the performance of L. divaricata seedlings produced in different substrates in the nursery, as well as verify if the results obtained influence survival and growth after planting in the field. The seedlings were produced with four different substrate formulations (T1: 100% peat-based commercial substrate (Peat); T2: 80% peat and 20% carbonized rice husk (CRH); T3: 60% peat and 40% CRH; T4: 40% peat and 60% CRH). In the nurseries, at 202 days after sowing, the height, stem base diameter, aerial dry mass, root dry mass, total dry mass and Dickson quality index were evaluated. After the seedlings were planted in the field, their survival, height growth and stem base diameter were monitored. L. divaricata seedlings produced with up to 40% CRH mixed with peat-based commercial substrate can present adequate growth in the field, although improved performance may occur with even 20% CRH. It should be noted that the growth response of L. divaricata seedlings in the nursery is more efficient when associated with the performance of the seedlings in the field.   Key words: Native species, carbonized rice husk, initial growth after planting, substrate.

Predicting pine weevil risk: Effects of site, planting spot and seedling level factors on weevil feeding and mortality of Norway spruce seedlings

Several insecticides used against large pine weevil (Hylobius abietis (L.)) feeding have been prohibited due to environmental and health issues. Thus, there is a need to find other protection methods. We investigated whether spot mounding without insecticide protection could ensure high seedling survival in boreal conditions. In addition, we predicted pine weevil feeding and mortality by site, planting spot and seedling level factors. A generalized linear mixed model (GLMM) was used for predicting feeding pressure. Multivariate GLMM was used for modelling the effects of feeding pressure on lambda-cyhalothrin insecticide-sprayed and unsprayed seedlings. We planted Norway spruce (Picea abies (L.) Karst.) container seedlings for two different years in central Finland. Seedlings were planted with and without insecticide treatment in spot mounds. Untreated seedlings were also planted in unprepared humus to predict pine weevil feeding pressure. Pine weevil feeding pressure was explained only by the age of the clear cuts: feeding pressure was high in fresh clear cuts and decreased if there was one growing season between the clear cut and the planting. On average, 8% of unsprayed seedlings planted in mounds died within two years after planting, while 2% of sprayed seedlings died. Under high feeding pressure, mortality probability of an unsprayed seedling planted in a mound was less than 0.1 only when the seedling was surrounded by mineral soil and the stem base diameter of seedlings was at least 4mm. In mounds covered by mineral soil, especially if it was medium coarse, soil was splashed on the stem base and thereby protected seedlings from pine weevil feeding. Under lower feeding pressure, also thinner seedlings survived without insecticide treatment if mounds were covered by mineral soil. Thus, if Norway spruce seedlings are planted without insecticide treatment, they should have a relatively thick stem and need to be planted in mounds covered with mineral soil.

Improvement of In Vitro Date Palm Plantlet Acclimatization Rate with Kinetin and Hoagland Solution.

In vitro propagation of date palm Phoenix dactylifera L. is an ideal method to produce large numbers of healthy plants with specific characteristics and has the ability to transfer plantlets to ex vitro conditions at low cost and with a high survival rate. This chapter describes optimized acclimatization procedures for in vitro date palm plantlets. Primarily, the protocol presents the use of kinetin and Hoagland solution to enhance the growth of Barhee cv. plantlets in the greenhouse at two stages of acclimatization and the appropriate planting medium under shade and sunlight in the nursery. Foliar application of kinetin (20mg/L) is recommended at the first stage. A combination between soil and foliar application of 50% Hoagland solution is favorable to plant growth and developmental parameters including plant height, leaf width, stem base diameter, chlorophyll A and B, carotenoids, and indoles. The optimum values of vegetative growth parameters during the adaptation stage in a shaded nursery are achieved using planting medium containing peat moss/perlite 2:1 (v/v), while in a sunlight nursery, clay/perlite/compost at equal ratio is the best. This protocol is suitable for large-scale production of micropropagated date palm plantlets.

Water Treatments and Root-Shoot Growth Relations in Yemane (<i>Gmelina arborea roxb.</i>) Seedlings

The nursery study was conducted to provide a scientific explanation for the practice of hardening seedlings in the nursery prior to out-planting in the open field. Three watering treatments (unstressed condition (US) seedlings watered twice a day, moderately stressed condition (MS), seedlings watered once a week, and severely stressed condition (SS), water is applied when seedlings show symptoms of mid-day wilting) were applied to Yemane seedlings (<i>Gmelina arborea Roxb.</i>) and their effects on root-shoot growth parameters were measured. Yemane was selected as the test species considering their massive use for reforestation in the Philippines. The experiment was laid in a Randomized Complete Block Design (RCBD) with each treatment replicated 6 times. Data was obtained for a period of four (4) months and the ANOVA for RCBD was used to test level of significance among the treatments. The Duncan’s Multiple Range Test (DMRT) was used to compare treatment means. Shoot height, stem diameter, leaf area and shoot biomass and root length, root diameter, root density and root biomass were the parameters measured for above and below ground, respectively. Water treatments influence biomass partitioning responsible for the changes in seedling morphology and architecture. Seedlings in unstressed condition has bigger basal stem diameter, longer shoot length and wider leaf area. Furthermore, seedlings in unstressed condition obtained the largest volume of green shoot biomass but when ovendried has lighter weights, compared to the moderate and severely stressed seedlings. Severely stressed seedlings obtained the largest biomass gain in the number and length of lateral roots, root density, root biomass, root: shoot ratio and the production of a more fibrous root system. Water stress treatments suppressed the elongation of shoot parts but promotes increases in root parts. In the same manner, water treatments influenced source-sink relation between root and shoot parts wherein carbohydrates accumulates in the leaves and stem of seedlings in unstressed condition but shift to the roots in moderate and severely stressed condition. The shift in carbon allocation is an adaptive mechanism for stress regulation accounting for the larger increment in root parts under water stressed environment. It is clear that water stress treatments modified root and shoot morphology and it can used as a hardening tool for seedlings during the nursery tending phase.

Response of seed germination and seedling growth of Chinese fir to different light intensities

The effect of light intensity on the seed germination and seedling growth of Chinese fir under different light intensities (100%, 40%, 20%, 10%, 5% of full light, and the PPFD was 201.3, 77.0, 37.5, 19.2, 9.8 μmol·m-2·s-1, respectively) was investigated, and the adaptive strategy of seed germination, seedling survival, growth, morphological plasticity, biomass accumulation and allocation under different light intensities was explored in this paper. The results showed that light intensity significantly affected the germination rate, survival rate, establishment rate and germination index. Germination rate reached the maximum under 40% light intensity, while survival rate and establishment rate reached the maximum at 100% light intensity. With the light intensity decreased, the stem length increased, while the root length, cotyledon length, cotyledon thickness and euphylla number declined, and basal stem diameter had no significant difference among diffe-rent light intensities. The total biomass, root biomass, stem biomass and leaf biomass were the highest under 100% light intensity. With the light intensity decreased, the photosynthesis non-photosynthesis biomass ratio and leaf biomass ratio declined, while stem biomass ratio increased, the root to shoot ratio and root biomass ratio had no significant difference among different light intensities. Low light promoted seed germination, but seedlings grew slowly with high mortality under low light. The accumulation of biomass in stem increased the plant tolerance to low light.

Loss of preferred habitat and pollen limitation threatens reproduction in a rare mountain Paeonia delavayi

Paeonia delavayi is a wild tree peony species endemic to high-altitude regions in southwestern China. Recent agricultural land expansion, however, not only causes its dwindling population size, but also poses a severe threat to its long-term persistence. Since our knowledge of the reproductive biology of P. delavayi is very limited, and some management misconceptions have further exacerbated the already worrisome situation, the aim of the present study is to provide some scientific evidence regarding habitat preference and breeding system of P. delavayi, and to help correct some management misconceptions. Specifically, morphological traits of P. delavayi populations growing in two different habitats (i.e., the open area versus forest understory), including basal stem diameter, plant height and flower numbers per plant, were measured and compared with each other. A range of floral manipulation experiments was further conducted to study the extent of self-compatibility and pollen limitation. The results showed that P. delavayi preferred the open habitat over forest understory as it generally grew bigger with thicker stems, and produced a higher number of flowers in the former habitat. Therefore, the open habitat should receive immediate priority for conservation action instead of being converted to agricultural land; also, P. delavayi is pollen limited, as evidenced by the fact that experimental flowers receiving supplemental non-self pollen generally displayed elevated seed production than flowers subjected to other treatments (e.g., non-supplemental self pollen, non-supplemental non-self pollen and supplemental self pollen), which is consistent with reported observations that alpine plants are more likely to be pollen-limited than lowland plants. We suggest that human intervention might be necessary to guarantee the long-term persistence of P. delavayi as harsh alpine environment, intense competition for pollinators and different anthropogenic perturbations co-limit its reproductive success.

Allometric tree biomass models of various species grown in short-rotation agroforestry systems

Biomass equations for tree species and the early stages of growth used in short-rotation coppices and agroforestry systems are still lacking. Further, discussion about the structure and parameters of biomass equations are still ongoing. Yield estimations should be precise, while keeping efforts low. To determine the influence of tree species, farming system, and tree position (inner and outer row) on allometric relationships, we derived biomass equations for various tree species from organic and conventional silvoarable agroforestry systems with an alley-cropping configuration. The allometric equations were based on the power relationship between aboveground dry biomass and stem base diameter (SBD) as a single variable or in combination with tree height (H) and were calculated by log-linear mixed-effect regression. Equations span the third and fourth growth year of the first rotation and were validated on the fourth year. Neither farming system nor row position influenced allometric relationship, although biometric variables varied between trees from inner and outer rows. A general model across species explained 95% ( $$R_{\text{cond}}^{2}$$ ) of the variation for tree dry weight or 97% ( $$R_{\text{cond}}^{2}$$ ) with H as covariate. Yet, for the sake of precision, species-specific equations were necessary. The best fitting equation with only SBD as predictor had species-specific allometric factors and a general exponent across species. However, predicted yields were biased by 8–31%. Thus, functions incorporating H are recommended, as compensation for variances in height-diameter relationships due to the ontogenetic stage, site differences, or social status of the tree reduced the bias of biomass estimation (<10%).

Morphological Response of Eight Quercus Species to Simulated Wind Load.

Leaf shape, including leaf size, leaf dissection index (LDI), and venation distribution, strongly impacts leaf physiology and the forces of momentum exerted on leaves or the canopy under windy conditions. Yet, little has been known about how leaf shape affects the morphological response of trees to wind load. We studied eight Quercus species, with different leaf shapes, to determine the morphological response to simulated wind load. Quercus trees with long elliptical leaves, were significantly affected by wind load (P< 0.05), as indicted by smaller specific leaf area (SLA), stem base diameter and stem height under windy conditions when compared to the control. The Quercus trees with leaves characterized by lanceolate or sinuous edges, showed positive morphological responses to wind load, such as bigger leaf thickness, larger stem diameter, allocation to root biomass, and smaller stem height (P< 0.05). These morphological responses to wind can reduce drag and increase the mechanical strength of the tree. Leaf dissection index (LDI), an important index of leaf shape, was correlated with morphological response to wind load (P< 0.05), including differences in SLA, in stem base diameter and in allocation to root biomass. These results suggest that trees with higher LDI, such as those with more and/or deeper lobes, are better adapted to wind load.

Ecological characteristics andin situgenetic associations for yield-component traits of wildMiscanthusfrom eastern Russia

Background and aims Miscanthus is a genus of perennial C4 grasses native to East Asia. It includes the emerging ligno-cellulosic biomass crop M. ×giganteus, a hybrid between M. sinensis and M. sacchariflorus. Biomass yield and cold tolerance are of particular interest in Miscanthus, given that this crop is more temperate adapted than its C4 relatives maize, sorghum and sugarcane. Methods A plant exploration was conducted in eastern Russia, at the northern extreme of the native range for Miscanthus, with collections including 174 clonal germplasm accessions (160 M. sacchariflorus and 14 M. sinensis) from 47 sites. Accessions were genotyped by restriction site-associated DNA sequencing (RAD-seq) and plastid microsatellites. Key Results Miscanthus sinensis was found in maritime climates near Vladivostok (43·6°N) and on southern Sakhalin Island (46·6°N). Miscanthus sacchariflorus was found inland at latitudes as high as 49·3°N, where M. sinensis was absent. Most M. sacchariflorus accessions were diploid, but approx. 2 % were tetraploids. Molecular markers revealed little population structure (Jost's D < 0·007 among diploid groups) but high genetic diversity (expected heterozygosity = 0·14) within the collection of Russian M. sacchariflorus. Genome-wide association (GWA) analysis for traits measured at the collection sites revealed three M. sacchariflorus single nucleotide polymorphisms (SNPs) significantly associated with the number of stems per unit area, one with height and one with basal stem diameter; three were near or within previously described sorghum quantitative trait loci for related traits. Conclusions This new Miscanthus germplasm collection from eastern Russia will be useful for breeding Miscanthus and sugarcane cultivars with improved adaptation to cold. Moreover, a strategy is proposed to facilitate the rapid utilization of new germplasm collections: by implementing low-cost SNP genotyping to conduct GWA studies of phenotypic data obtained at collection sites, plant breeders can be provided with actionable information on which accessions have desirable traits and alleles.

Effect of rock fragments content on water consumption, biomass and water-use efficiency of plants under different water conditions

The proportion of rock fragments in soil affects water availability and therefore the characteristics of plants. The objective of this study was to evaluate the effect of rock-fragment content on plant water consumption, biomass, growth and water-use efficiency (WUE) under different water conditions. Four gravimetric treatments of rock-fragment contents (0, 10, 30 and 50%) and four treatments of water content were tested in sandy loamy soils. The water contents of the rock-free soil were 15–19% (80–100% of field capacity), 11–15% (60–80% of field capacity), 9–11% (47–60% of field capacity) and 6–9% (32–47% of field capacity). Transpiration, plant height, basal stem diameter and biomass of korshinsk peashrubs in the treatments were measured and compared. Plants grown in the soil with rock fragments transpired less, especially under well-watered conditions. The mean daily transpiration of plants in the soils with 30 and 50% rock-fragment contents was 18% (P=0.021) and 34% (P=0.001) lower, respectively, in 2014, and 25% (P=0.008) and 31% (P=0.002) lower, respectively, in 2015 relative to the soil without rock fragments and was not lower in the soil with 10% rock fragments. Plant height, basal stem diameter and biomass did not differ significantly between rock-fragment contents of 0 and 30% but were lower at 50%. WUE, the ratio between total transpiration and biomass, was highest at 30% and then decreased at 50%. Increasing plant water stress could thus improve WUE. The rock fragments in the soil had significant effects on plant water consumption, biomass, growth and WUE. Optimizing the rock-fragment content is necessary when the relationships between plants and water in stony ecosystems are evaluated.

Maize response to inoculation with strains of plant growth-promoting bactéria

ABSTRACT The aim of this study was to evaluate the response of maize to inoculation with strains of plant growth-promoting bacteria (PGPB) in two cultivation years. The experiment was set in a randomized block design with four replicates in two cultivation years (2012/13 and 2013/14). The treatments consisted of PGPB inoculation: control (without N and without inoculation); 30 kg of N ha-1 at sowing (N1); 160 kg of N ha-1 (N1 + 130 kg of N ha-1 as top-dressing); N1 + A. brasilense, Ab-V5; N1 + A. brasilense, HM053; N1 + Azospirillum sp. L26; N1 + Azospirillum sp. L27; N1 + Enhydrobacter sp. 4331; N1 + Rhizobium sp. 8121. Basal stem diameter, plant height, leaf area, shoot dry matter and yield were evaluated. The strain of Rhizobium sp. 8121and the isolate Azospirillum sp. L26 associated with 30 kg of N ha-1 at sowing promoted yields equivalent to that of the N fertilization of 160 kg ha-1, demonstrating the potential to be used in the inoculation of maize seeds.

Arbuscular Mycorrhizal Fungus Species Dependency Governs Better Plant Physiological Characteristics and Leaf Quality of Mulberry (Morus alba L.) Seedlings.

Understanding the synergic interactions between arbuscular mycorrhizal fungi (AMF) and its host mulberry (Morus alba L.), an important perennial multipurpose plant, has theoretical and practical significance in mulberry plantation, silkworm cultivation, and relevant textile industry. In a greenhouse study, we compared functional distinctions of three genetically different AMF species (Acaulospora scrobiculata, Funneliformis mosseae, and Rhizophagus intraradices) on physiological and growth characteristics as well as leaf quality of 6-month-old mulberry seedlings. Results showed that mulberry was AMF-species dependent, and AMF colonization significantly increased shoot height and taproot length, stem base and taproot diameter, leaf and fibrous root numbers, and shoot and root biomass production. Meanwhile, leaf chlorophyll a or b and carotenoid concentrations, net photosynthetic rate, transpiration rate and stomatal conductance were generally significantly greater, while intercellular CO2 concentration was significantly lower in AMF-inoculated seedlings than in non-AMF-inoculated counterparts. These trends were also generally true for leaf moisture, total nitrogen, all essential amino acids, histidine, proline, soluble protein, sugar, and fatty acid as they were significantly increased under mycorrhization. Among these three tested AMFs, significantly greater effects of AMF on above-mentioned mulberry physiological and growth characteristics ranked as F. mosseae > A. scrobiculata > R. intraradices, whilst on mulberry leaf quality (e.g., nutraceutical values) for better silkworm growth as F. mosseae ≈A. scrobiculata > R. intraradices. In conclusion, our results showed that greater mulberry biomass production, and nutritional quality varied with AMF species or was AMF-species dependent. Such improvements were mainly attributed to AMF-induced positive alterations of mulberry leaf photosynthetic pigments, net photosynthetic rate, transpiration rate, and N-containing compounds (methionine, threonine, histidine, and proline). As a result, application of Funneliformis mosseae or A. scrobiculata in mulberry plantation could be a promising management strategy to promote silkworm cultivation and relevant textile industry.

Characterization of accessions and species of Macadamia to stem infection by Phytophthora cinnamomi

Phytophthora cinnamomi is a major pathogen in most macadamia plantations worldwide. Due to stem lesions, stem cankers and leaf defoliation, it results in loss of productivity and tree death. This study examined accessions of the four Macadamia species and their hybrids, produced via rooted stem cuttings or germinated seeds, for susceptibility to stem canker and necrotic lesions caused by P. cinnamomi. Plants were wound‐inoculated with agar containing P. cinnamomi. The symptoms produced in inoculated plants were used to characterize host susceptibility variation within and among the population. Lesion length and severity of stem canker were recorded. The four species and hybrids differed significantly in stem canker severity (P &lt; 0.001) and lesion length (P = 0.04). Macadamia integrifolia and M. tetraphylla hybrids were the most susceptible. Macadamia integrifolia had the greatest stem canker severity and the most extensive lesions above and below the site of inoculation. Restricted lesion sizes were observed in M. ternifolia and M. jansenii. The effects of basal stem diameter and the method of propagation either from cuttings or from seed were not significant. The genetic variation in the reaction of macadamia accessions to stem infection by P. cinnamomi is discussed.

Growth–survival trade-off in shrub saplings from Neotropical mountain grasslands

The growth–survival trade-off plays a central role in the coexistence of species-rich plant communities. While recurrently described in forest tree communities primarily limited by light availability, this trade-off is still poorly documented in grassland and savanna vegetation. In this comparative study we planted in a quartzitic degraded site eight-month-old saplings of eleven shrub species native from constrained mountain grassland (Brazilian rupestrian grassland). We measured the relative growth rate (RGR) during a 30-week time interval, leaf water potential under dry and wet conditions, and related these traits to the species survival. The interspecific comparison between the saplings performance clearly showed the classic growth–survival trade-off. The RGR expressed in stem diameter and aboveground biomass explained respectively 62% and 40% of the variation in saplings' survival one year after planting, and respectively 65% and 44% of the variation in survival 4.5years after planting. This trade-off was not related to either leaf water potential or final size in aboveground biomass and basal stem diameter. Our results corroborate the view that the growth–survival trade-off is universally applicable, even in non-forest communities such as grasslands and savannas subjected to severe nutritional deficiency, pronounced seasonal drought, and high light incidence. The environmental differences in micro-habitats that compose rupestrian grasslands should distinctly favour species with contrasting strategies of growth and survival, thus contributing to niche partitioning and coexistence in this species-rich ecosystem.

Allometric relationships from coppice structure of seven North American willow (Salix) species

Biomass yield and component coppice growth traits were assessed in up to 20 clones from seven native North American willow species, Salix amygdaloides (SAM), Salix bebbiana (BEB), Salix discolor (DIS), S eriocephala (ERI), Salix humilis (HUM), Salix interior (INT), and Salix nigra (NIG), established together in a clonally replicated common-garden field test. Aboveground mass, coppice stem number, stem length, and stem basal diameter measurements on up to 20 of the largest stems from 2-yr-old coppiced plants showed that ERI had the greatest aboveground mass, followed by INT, and then a close grouping of BEB, DIS, and HUM; the “tree” willows, AMY and NIG, had the lowest yields. The tree willows were not as prolific in coppice stem sprout production as were the shrub willows. The greatest number of stem sprouts was produced by ERI, with one coppice producing 67 2-yr-old stem sprouts, and ERI also showed an atypical, non-negative relationship between stem size and stem number; whereas the other six willows showed a varying but expected negative relationship between coppice stem size and stem number. Species differences in allometric relationships highlight the need to develop species-specific models for more accurate non-destructive biomass yield estimation.