Increasing Tree Height Research Articles

Effect of organic and inorganic mulches on growth, yield and fruit quality of peach cv Redhaven

The present study was carried out on the effect of mulch materials on growth, yield and fruit quality of peach [Prunus persica (L) Batsch] cv Redhaven at experimental block of Department of Fruit Science, Dr YS Parmar University of Horticulture and Forestry, Nauni, Solan, Himachal Pradesh during 2019-2020. Various types of mulches like grass mulch, black polyethylene mulch, silver red polyethylene mulch, polyethylene mulch, nylon mulch mat and coir mulch were evaluated in this experiment. The results of the study showed that plant growth, yield and fruit quality of peach were significantly affected by all the mulching treatments as compared to control. The maximum increase in tree height, spread, volume, annual shoot extension growth, fruit set, lowest fruit drop, fruit yield, leaf area, leaf chlorophyll content, fruit size, weight and volume were recorded in the plants under black polyethylene mulch which was statistically at par with nylon mulch mat. The maximum fruit quality parameters like total soluble solids, titratable acidity, reducing and non-reducing sugars were recorded under nylon mulch mat.

Interspecific variations in tree allometry and functional traits in subtropical plantations in southern China.

Mechanical stability against buckling and water transport resistance through xylem vary with increasing tree height. To explore interspecific allometry based on morphological and physiological traits can play a crucial role in revealing their ecological adaptation. Four architectural traits (tree height, diameter at the breast height (DBH), crown width and crown depth) and seven functional traits (specific leaf area (SLA), leaf total carbon concentration (TC), midday leaf water potential, leaf δ13C and δ18O, wood density and xylem water transport efficiency) were measured in Schima superba, Acacia auriculiformis and Eucalyptus citriodora plantations in the subtropical region of China. The mechanical stability declined in the order of S. superba > A. auriculiformis > E. citriodora. Taller species at a given DBH had slender stems and narrower crowns. Smaller leaf δ18O and more efficient xylem water transport were observed in two taller tree species, A. auriculiformis and E. citriodora. Smaller SLA, higher leaf TC and larger leaf area indicated more carbon allocation to leaves of S. superba. The variations in architectural and functional traits with tree allometry among tree species may provide a more complete understanding of species-specific growth strategies in this subtropical region.

Range margin populations show high climate adaptation lags in European trees.

How populations of long-living species respond to climate change depends on phenotypic plasticity and local adaptation processes. Marginal populations are expected to have lags in adaptation (i.e. differences between the climatic optimum that maximizes population fitness and the local climate) because they receive pre-adapted alleles from core populations preventing them from reaching a local optimum in their climatically marginal habitat. Yet, whether adaptation lags in marginal populations are a common feature across phylogenetically and ecologically different species and how lags can change with climate change remain unexplored. To test for range-wide patterns of phenotypic variation and adaptation lags of populations to climate, we (a) built model ensembles of tree height accounting for the climate of population origin and the climate of the site for 706 populations monitored in 97 common garden experiments covering the range of six European forest tree species; (b) estimated populations' adaptation lags as the differences between the climatic optimum that maximizes tree height and the climate of the origin of each population; (c) identified adaptation lag patterns for populations coming from the warm/dry and cold/wet margins and from the distribution core of each species range. We found that (a) phenotypic variation is driven by either temperature or precipitation; (b) adaptation lags are consistently higher in climatic margin populations (cold/warm, dry/wet) than in core populations; (c) predictions for future warmer climates suggest adaptation lags would decrease in cold margin populations, slightly increasing tree height, while adaptation lags would increase in core and warm margin populations, sharply decreasing tree height. Our results suggest that warm margin populations are the most vulnerable to climate change, but understanding how these populations can cope with future climates depend on whether other fitness-related traits could show similar adaptation lag patterns.

Ontogenetic shifts in resource allocation and potential defense syndromes of a tropical medicinal treelet

Variation of plant traits across ontogeny can play an important role in shaping the vital functions of growth, reproduction and defense, depending on the priorities of resource investment. Plant functional traits in seven ontogenetic stages, following complete trajectories, of a tropical light-demanding evergreen medicinal treelet (Rauvolfia vomitoria Afzel.) were examined in a common garden experiment in the field. The highly plastic morph-physiological and potential defense traits showed complex and nonlinear variations with increasing tree height (age), revealing a mostly clear-defined transition at reproductive onset. Leaf photosynthetic rate varied in a unimodal pattern throughout ontogeny, with the highest value occurring at reproductive onset. Except for the oldest plants, priority of resource use in leaves across ontogeny shifted to enhance photosynthetic rate, photosynthetic N and P use efficiencies, and prevention of physical damage (higher leaf thickness, leaf mass per area and lignin concentration), but to decrease carbon-based chemical defense (i.e., total phenolics). Fine root phenolics were relatively stable, but lignin concentration increased throughout ontogeny. With higher levels than fine roots and aboveground parts, the concentrations of an indole alkaloid (i.e. reserpine) increased steadily in coarse roots, especially during the reproductive stages. Whereas, tree growth progressively shifted from the demand of N relative to P, based on the indirect evidence from N:P stoichiometry. Our results demonstrated that, under the conditions of no environmental interference, the pronounced trajectories in functional traits were observed throughout the life cycle of R. vomitoria plants due to strong ontogeny-induced shifts in resource allocation. The synergies or tradeoffs of the defense syndromes differed between and within the classes of defense (i.e., physical versus chemical), and also, between and within above- and below-ground tissues across the ontogenetic developmental stages, which could probably be explained by multiple defense hypotheses. The revealed variations of the growth traits and secondary metabolites of R. vomitoria plants at different developmental stages will be helpful for maximizing the reserpine yield through the suitable cultivation practices.

Trees as large-scale natural phononic crystals: Simulation and experimental verification

Urban trees are usually planted on a periodic layout in the spatial configuration. We regard urban trees as large-scale natural phononic crystals. The entire forest is reduced to a reasonable “tree-soil” unit cell based on the phononic crystal theory and finite element method by COMSOL software is used to obtain the dispersion curves. The Rayleigh wave band gaps of phononic trees are distinguished by the sound cone method. The influences of soil elastic modulus and tree height on band gaps are investigated. A three-dimensional simulation model and experiment test are applied to validate the effect of phononic trees on vibration control. The numerical frequency reduction zones coincide exactly with the theoretical band gaps. Increasing soil stiffness results in a higher-frequency and wider band gap. An increasing tree height is beneficial to obtain low-frequency band gaps. A periodically arranged plantation that Rayleigh wave band gaps at frequency ≤60 Hz could be designed. This study opens up a new theoretical basis for the quantitative analyses of urban trees to the ground vibration mitigation at a certain frequency range.

Populus trichocarpa clade A PP2C protein phosphatases: their stress-induced expression patterns, interactions in core abscisic acid signaling, and potential for regulation of growth and development.

Overexpression of the poplar PP2C protein phosphatase gene PtrHAB2 resulted in increased tree height and altered leaf morphology and phyllotaxy, implicating PP2C phosphatases as growth regulators functioning under favorable conditions. We identified and studied Populus trichocarpa genes, PtrHAB1 through PtrHAB15, belonging to the clade A PP2C family of protein phosphatases known to regulate abscisic acid (ABA) signaling. PtrHAB1 through PtrHAB3 and PtrHAB12 through PtrHAB15 were the most highly expressed genes under non-stress conditions. The poplar PP2C genes were differentially regulated by drought treatments. Expression of PtrHAB1 through PtrHAB3 was unchanged or downregulated in response to drought, while all other PtrHAB genes were weakly to strongly upregulated in response to drought stress treatments. Yeast two-hybrid assays involving seven ABA receptor proteins (PtrRCAR) against 12 PtrHAB proteins detected 51 interactions involving eight PP2Cs and all PtrRCAR proteins with 22 interactions requiring the addition of ABA. PtrHAB2, PtrHAB12, PtrHAB13 and PtrHAB14 also interacted with the sucrose non-fermenting related kinase 2 proteins PtrSnRK2.10 and PtrSnRK2.11, supporting conservation of a SnRK2 signaling cascade regulated by PP2C in poplar. Additionally, PtrHAB2, PtrHAB12, PtrHAB13 and PtrHAB14 interacted with the mitogen-activated protein kinase protein PtrMPK7. Due to its interactions with PtrSnRK2 and PtrMPK7 proteins, and its reduced expression during drought stress, PtrHAB2 was overexpressed in poplar to test its potential as a growth regulator under non-stress conditions. 35S::PtrHAB2 transgenics exhibited increased growth rate for a majority of transgenic events and alterations in leaf phyllotaxy and morphology. These results indicate that PP2Cs have additional roles which extend beyond canonical ABA signaling, possibly coordinating plant growth and development in response to environmental conditions.

Effect of rootstock in tree growth, dry matter, flowering, yield and quality of ‘Manila’ mango

Rootstock can modify tree size, flowering, and fruit yield and quality of mangoes. Using rootstock is an option for improving productive efficiency of the tree. The objective was to determine the growing, yield and fruit quality of mango ‘Manila’ grafted on different rootstocks to identify them potential use in high density plantations, as well as the effect of wind on fruit yield. ‘Manila’ mango cuttings were grafted onto short (‘Thomas’ and ‘Julie’), medium (‘Esmeralda’, ‘Irwin Morado’, ‘Gomera 1’ and ‘Chauza’) and tall (‘Criollo’) rootstock. Tree growth, leaf area, dry matter, flowering, and fruit yield and quality were determined. Also, the effect of wind on fruit yield was evaluated. Non-linear increase in tree height (m) was observed, while stem (cm) and canopy diameters (m) had linear growth. Leaf area (m2), dry matter (kg), flower production (panicles tree−1), fruit production (fruits tree−1), and total soluble solids content (°Brix) were affected positively by the rootstock. The rootstock cultivar ‘Julie’ promoted larger trees, more leaf area and dry matter, and higher fruit production, while ‘Thomas’ reduced tree size and stimulated lower production of panicles and fruits. Wind at speeds of more than 65 km h−1 can reduce fruit yield by more than 80% in the third year of production. Fruit size (cm) and weight (g) were not altered. Rootstock vigor was not necessarily reflected in tree size since short rootstock promoted different tree performance. According with tree size and yield was able to identify rootstocks with better adjustment to different planting densities.

Response of orchard floor management treatments to soil hydrothermal regimes in nectarine

Being the second important stone fruit crop of Himachal Pradesh, nectarine still requires a great improvisation in floor management. Keeping this objective, a two year study was conducted with various orchard floor management practices on eight year old ‘Snow Queen’ nectarine trees during 2014 and 2015. The experiment was laid out in Randomized Block Design, having seven treatments including control and replicated four times. Among all treatments soil hydrothermal regimes were maintained effectively under grass mulch and black polythene mulch. Grass mulch recorded maximum increase in annual shoot growth (148.25 cm), per cent increase in trunk girth (11.49%), per cent increase in tree height (14.46%) and per cent increase in tree volume (40.84%). Maximum fruit set (74.38%) and fruit yield (26.09 kg/tree) was recorded under nylon mulch mat while minimum fruit drop (16.37%) under grass mulch. Bicolour polythene mulch recorded fruit size (56.90 mm), fruit weight (100.97 g), fruit volume (102.94 cc), pulp to stone ratio (14.65), TSS (12.91 oBrix), total sugars (9.58%) and reducing sugars (4.10%) along with maximum proportion (82.25%) of “A” grade fruits.

Trees as large-scale natural metamaterials for low-frequency vibration reduction

Urban trees are often planted in a periodic arrangement in space. This study takes urban trees as natural metamaterials. Based on the metamaterial theorem, a three-dimensional unit cell is used to represent the entire forest, and finite element analysis via COMSOL software is implemented to identify dispersion relationships. The surface-wave band gaps of urban forests are identified using the sound cone method and strain energy method. The influences of soil elastic modulus, tree spacing, trunk radius, and tree height on band gaps are discussed. Finally, a three-dimensional simulation model is established to verify the effect of urban trees on vibration reduction. The results show that numerical frequency-reduction zones are consistent with theoretical surface-wave band gaps. An increasing soil modulus results in a wider and higher-frequency band gap. Urban forests with larger trunk diameters and smaller tree distance can generate lower-frequency and wider band gaps. It is beneficial to obtain low-frequency band gaps with increasing tree height. A manmade engineered array of trees can be designed with Rayleigh wave band gaps at a low frequency of ≤80 Hz. This study provides a new concept for the quantitative design of urban forests to reduce ground vibration in specific frequency ranges.

More than climate? Predictors of tree canopy height vary with scale in complex terrain, Sierra Nevada, CA (USA)

Tall trees and vertical forest structure are associated with increased productivity, biomass and wildlife habitat quality. While climate has been widely hypothesized to control forest structure at broad scales, other variables could be key at fine scales, and are associated with forest management. In this study we identify the environmental conditions (climate, topography, soils) associated with increased tree height across spatial scales using airborne Light Detection and Ranging (LiDAR) data to measure canopy height. The study was conducted over a large elevational gradient from 200 to 3000 m in the Sierra Nevada Mountains (CA, USA) spanning sparse oak woodlands to closed canopy conifer forests. We developed Generalized Boosted Models (GBMs) of forest height, ranking predictor variable importance against Maximum Canopy Height (CHMax) at six spatial scales (25, 50, 100, 250, 500, 1000 m). In our study area, climate variables such as the climatic water deficit and mean annual precipitation were more strongly correlated with CHmax (18–52% relative importance) than soil and topographic variables, and models at intermediate (50–500 m) scales explained the most variance in CHMax (R2 0.77–0.83). Certain soil variables such as soil bulk density and pH, as well as topographic variables such as the topographic wetness index, slope curvature and potential solar radiation, showed consistent, strong associations with canopy structure across the gradient, but these relationships were scale dependent. Topography played a greater role in predicting forest structure at fine spatial scales, while climate variables dominated our models, particularly at coarse scales. Our results indicate that multiple abiotic factors are associated with increased maximum tree height; climatic water balance is most strongly associated with this component of forest structure but varies across all spatial scales examined (6.9–54.8% relative importance), while variables related to topography also explain variance in tree height across the elevational gradient, particularly at finer spatial scales (37.15%, 20.26% relative importance at 25, 50 m scales respectively).

Soil amendment alters soil physicochemical properties and bacterial community structure of a replanted apple orchard

Compost amendment reportedly improved apple tree growth in replant soils. However, its effects should be evaluated at different soil depths and locations. This study investigated the impact of soil improvement with compost on soil physicochemical properties and bacterial community structure of a replanted apple orchard in comparison with the original orchard without compost improvement. The V1–V3 region of the bacterial 16S rRNA gene was subjected to high-throughput 454 pyrosequencing, and data were analyzed using the Mothur pipeline. The results showed that the soil improvement benefited tree growth and fruit quality during the study period. The compost amendment markedly increased tree height and stem diameter by a range of 6.1%–21.0% and 4.0%–14.0%, respectively. Fruit yield (9.5%), average weight (9.6%), and soluble solid content (5.6%) were also increased by compost amendment compared to those of the unimproved treatment. The pH, organic matter, and available N, P, and K contents were significantly increased by 5.7%–21.9%, 0.2%–62.9%, 9.3%–29.3%, 36.7%–64.5%, and 17.2%–100.3% in the compost improved soil. The pyrosequencing data showed that the soil improvement changed the bacterial community structure at all soil depths (0–20 cm and 20–40 cm) and locations (in-row and inter-row) considered; e.g., the relative abundance of Proteobacteria (20.2%), Bacteroidetes (2.5%), and Cyanobacteria (1.0%) was increased while that of Chloroflexi (5.5%), Acidobacteria (5.2%), Nitrospirae (4.5%), Gemmatimonadetes (3.8%), and Actinobacteria (1.8%) was decreased. The relative abundance of some dominant genera Burkholderia (2.3%), Pseudomonas (1.0%), and Paenibacillus (0.5%) were enhanced in the compost improved soil. Moreover, other dominant genera such as Nitrospira (6.4%), Gemmatimonas (2.2%), and Phenylobacterium (0.3%) were reduced by the application of compost. Our results indicate that soil improvement benefits the growth of tree and fruit quality, and is likely mediated by increased soil pH, organic matter, and available nutrient contents and beneficial bacterial community composition.

Xylem anatomical adjustments prioritize hydraulic efficiency over safety as Norway spruce trees grow taller.

As a tree grows taller, the increase in gravitational pressure and path length resistance results in lower water potentials at a given flow rate and higher carbon construction costs to transport a given amount of water to the leaves. We investigated how hydraulic safety and efficiency are coordinated under the constraints of higher cavitation risks and higher carbon construction costs with increasing tree height. We combined measurements of xylem tracheid anatomical traits with the vulnerability to drought-induced embolism and hydraulic conductivity of the apical shoots of 2- to 37-m tall Picea abies trees growing at two sites in the Dolomites (Italian Eastern Alps). We found that the theoretical hydraulic conductivity of the apical shoots increased with tree height at both sites (P < 0.001) as a result of an increase in either total tracheid number or mean hydraulic diameter. The xylem water potential inducing 50% loss of apical conductance significantly increased from small (-4.45 ± 0.20 MPa) to tall trees (-3.65 ± 0.03 MPa) (P = 0.007). The more conductive xylem at the treetop of taller trees allows the full compensation for the height-related hydraulic constraints and minimizes the additional carbon costs of transporting water over a longer path length. The corresponding increase in vulnerability to cavitation shows that hydraulic efficiency is prioritized over safety during height growth.

Monitoring individual tree-based change with airborne lidar.

Understanding the carbon flux of forests is critical for constraining the global carbon cycle and managing forests to mitigate climate change. Monitoring forest growth and mortality rates is critical to this effort, but has been limited in the past, with estimates relying primarily on field surveys. Advances in remote sensing enable the potential to monitor tree growth and mortality across landscapes. This work presents an approach to measure tree growth and loss using multidate lidar campaigns in a high‐biomass forest in California, USA. Individual tree crowns were delineated in 2008 and again in 2013 using a 3D crown segmentation algorithm, with derived heights and crown radii extracted and used to estimate individual tree aboveground biomass. Tree growth, loss, and aboveground biomass were analyzed with respect to tree height and crown radius. Both tree growth and loss rates decrease with increasing tree height, following the expectation that trees slow in growth rate as they age. Additionally, our aboveground biomass analysis suggests that, while the system is a net source of aboveground carbon, these carbon dynamics are governed by size class with the largest sources coming from the loss of a relatively small number of large individuals. This study demonstrates that monitoring individual tree‐based growth and loss can be conducted with multidate airborne lidar, but these methods remain relatively immature. Disparities between lidar acquisitions were particularly difficult to overcome and decreased the sample of trees analyzed for growth rate in this study to 21% of the full number of delineated crowns. However, this study illuminates the potential of airborne remote sensing for ecologically meaningful forest monitoring at an individual tree level. As methods continue to improve, airborne multidate lidar will enable a richer understanding of the drivers of tree growth, loss, and aboveground carbon flux.

Factors Affecting Efficacy of Prescribed Fire for Western Juniper Control

Western juniper (Juniperus occidentalis Hook.) is a tree species occurring on 3.6 million ha in the northern Great Basin. This native species can be quite invasive, encroaching into sagebrush-grassland vegetation, forming woodlands, and dominating extensive landscapes. Control of encroaching juniper is often necessary and important. Efficacy of prescribed fire for western juniper control depends on many factors for which our understanding is still quite incomplete. This knowledge gap makes fire management planning for western juniper control more difficult and imprecise. Natural resource managers require a fire efficacy model that accurately predicts juniper mortality rates and is based entirely on predictors that are measurable prefire. We evaluated efficacy models using data from a fall prescribed fire conducted during 2002 in southwestern Idaho on mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana [Rydb.] Beetle) rangelands with early to midsuccessional juniper encroachment. A logistic regression model, which included vegetation cover type, tree height, fire type, and bare ground as predictors, accurately predicted (area under the receiver operating characteristic [ROC] curve [AUC] = 0.881 ± 0.128 standard deviation [SD]) the mortality rate for a random sample of western juniper trees marked and assessed prefire and 5 yr post fire. Trees occurring in an antelope bitterbrush (Purshia tridentata [Pursh] DC.) type, which had a heavy fuel load, were 8 times more likely to be killed by fire than trees in a mountain big sagebrush type, where loading was typically lighter. Probability of mortality decreased by 28.8% for each 1-meter increase in tree height. Trees exposed to head fire were 3 times as likely to be killed as those exposed to backing fire. Findings from this case study suggest that with just four factors which are readily quantifiable prefire, managers can accurately predict juniper mortality rate and thus make better informed decisions when planning prescribed fire treatments.

Trees on the move: using decision theory to compensate for climate change at the regional scale in forest social-ecological systems

The adaptation of social-ecological systems such as managed forests depends largely on decisions taken by forest managers who must choose among a wide range of possible futures to spread risks. We used robust decision theory to guide management decisions on the translocation of tree populations to compensate for climate change. We calibrated machine learning correlational models using tree height data collected from five common garden tests in France where Abies alba provenances from 11 European countries are planted. Resulting models were used to simulate tree height in the planting sites under current and 2050 climates (regional concentration pathway scenarios (RCPs) 2.6, 4.5, 6.0 and 8.5). Our results suggest an overall increase in tree height by 2050, but with large variation among the predictions depending on the provenance and the RCPs. We applied maximin, maximax and minimax decision rules to address outcomes under five uncertain states of the world represented by the four RCPs and the present climate (baseline). The maximin rule indicated that for 2050, the best translocation option for maximising tree height would be the use of provenances from Northwest France into all target zones. The maximax and minimax regret rules pointed out the same result for all target zones except for the ‘Les Chauvets’ trial, where the East provenance was selected. Our results show that decision theory can help management by reducing the number of options if most decision rules converge. Interestingly, the commonly suggested recommendation of using multiple provenances to mitigate long-term maladaptation risks or from ‘pre-adapted’ populations from the south was not supported by our approach.

Effect of planting density on growth, yield and fruit quality of apple cv. Jeromine

A field experiment was conducted to study the effect of different planting densities on growth, yield and fruit quality of three-years-old apple trees during 2017–2018. The experiment was laid out in a Randomized Block Design consisting of four treatments of planting densities viz., 5333 trees/ha (2.5 m × 0.75 m), 4000 trees/ha (2.5 m × 1.0 m), 3200 trees/ha (2.5 m × 1.25 m) and 2666 trees/ha (2.5 m × 1.5 m) and each treatment was replicated six times. The maximum annual shoot growth (44.58 cm) and increase in tree height (42.55 cm) was recorded in planting density of 2666 trees/ha (2.5 m × 1.5 m) which was significantly higher than all other planting densities. Highest fruit yield per tree (4.93 kg/tree) was observed in high density 2666 trees/ha (2.5 m x (17.50 tonne/ha) was recorded in planting density of 5333 trees/ha (2.5 m x 0.75 m). Maximum fruit length (65.90 mm), fruit diameter (76.07 mm), fruit weight (177.45 g), sugars content and anthocyanin content was found in planting density of 2666 trees/ha (2.5 m x 1.5 m). On the basis of two-years study, it can be concluded that the planting densities of 3200 trees/ha (2.5 m x 1.25 m) and 2666 trees/ha (2.5 m x 1.5 m) could be the optimum density for higher production of quality fruits.

Effects of Fertilization on Potassium and Magnesium Deficiencies Associated with Flowering in Hong Kong Orchid Tree (Bauhinia ×blakeana Dunn)

Hong Kong orchid tree is an outstanding flowering tree for tropical and subtropical areas, but in south Florida’s nutrient-poor sand soils, it typically develops moderate to severe K and Mg deficiency symptoms during the fall, winter, and spring months. A 3-year field experiment was conducted to determine if flowering was responsible for the development of these deficiencies and to determine if these deficiencies could be prevented by fertilization with medium or high rates of a 24N–0P–9.2K turf fertilizer (24–0–11) an 8N–0P–10K–4Mg plus micronutrients palm fertilizer (8–0–12) or a 0N–0P–13.3K–6Mg plus micronutrients palm fertilizer (0–0–16). Onset of deficiency symptoms coincided with the beginning of flowering, but leaf nutrient concentrations of N, P, K, and Mg continued to decline after flowering ceased in late January, presumably because of movement of these elements from the leaves to stem tissue. Leaf nutrient concentrations were poorly or negatively correlated with all measured plant quality variables and were poor indicators of plant quality or nutritional status. Although fertilization with a high rate of 24–0–11 or either rate of 8–0–12 increased tree height, caliper, and number of flowers, no treatment significantly decreased the severity of K and Mg deficiencies.

Bending properties of loblolly pine

A three-point bending test was used to assess the effects of moisture content, radial location, and tree height on the specific toughness and bending stress of loblolly pine. Test samples were collected at 20%, 40%, 60%, and 80% of the radial distance between the tree pith and bark, across four heights (0mm/tree base, 116.84mm/breast height, 304.80mm, and 457.20mm) of five randomly selected loblolly pine tree trunks. The wood samples were cut into cuboid shapes (40mm by 10mm by 5mm). The samples from the various tree radius and tree height combinations were then adjusted to 10%, 20%, or 30% moisture content (wet basis). The average specific toughness of loblolly pine varied between 14.41kJ/m2 and 100.75kJ/m2 whereas the average bending stress of loblolly pine varied between 35.14MPa and 117.65MPa. Increase in the moisture content of loblolly pine caused increase in its specific toughness and decrease in its bending stress. The bending stress and specific toughness of loblolly pine decreased with decreasing tree radius and increasing tree height. This result show that wood materials get tougher and stronger as they mature. Regression analysis revealed that moisture content was the most important factor influencing the specific toughness and bending stress of loblolly pine. The r2 for the polynomial regression model developed to predict specific toughness and bending stress from moisture content, tree height, and tree radius were 0.614 and 0.662, respectively.

Induction of changes by nitrification inhibitor and nitrogen source on vegetative growth, physiological processes and biochemical constituents of Kinnow mandarin

A field experiment was conducted on two-year-old Kinnow mandarin plant to find out effect of different nitrogen sources and nitrification inhibitors on vegetative growth, physiological processes and biochemical constituents of Kinnow mandarin. There were thirteen treatments comprising four nitrogen sources, viz. ammonium sulphate (AS), calcium nitrate (CN), mixture of ammonium sulphate + calcium nitrate and urea, two nitrification inhibitor, viz. Dicyandiamide (DCD) 5% of fertilizers, meliacins (M) 0.1% of fertilizers and control. The increase in tree height was recorded significantly higher in plants treated with AS + DCD (44.05%); whereas, tree spread E-W (77.33%), tree spread N-S (66.03%), specific leaf area (123.86 cm2/g) and shoot growth rate (247.39%) was found maximum in AS + M. In the plants applied with AS + DCD registered significantly maximum values of chlorophyll (a, b and total) content, photosynthetic rate and stomatal conductance. However, transpiration rate was found maximum under treatment AS + M when applied during winter and summer in split doses. Ammonium sulphate treated with DCDproduced statistically highest total soluble sugar (9.22, 9.78 and 9.40% leaf fresh wt) and soluble proteins (74.80, 76.49 and 71.96 mg/g leaf dry wt) during winter, autumn and summer, respectively followed by ammonium sulphate treated with meliacins. The ammonium sulphate and urea as source of N along with nitrification inhibitor have a strong impact on growth and physio-biochemical parameters on Kinnow plants; thus, improved the performance of Kinnow plants under above natural pH soil conditions.

Precommercial release thinning of potential Acacia koa crop trees increases stem and crown growth in dense, 8-year-old stands in Hawaii

An 8-year-old dense monotypic stand of naturally regenerated koa (Acacia koa A. Gray) on the Island of Hawaii was selected to determine the effects of precommercial release thinning, phosphorous (P) fertilization and herbaceous weed control on growth of potential crop trees over approximately 30months. Thinning consisted of cutting down all stems within a 4.5-m radius of the crop tree. Phosphorus was added at a rate of 300kgha−1 over two years. Herbaceous weeds were sprayed once with imazapyr, a broad-spectrum herbicide. Thinning alone or in combination with P fertilization significantly increased stem diameter increment and allometric estimates of the growth of leaf area and aboveground biomass. There was no significant increase in stem diameter, leaf area or biomass in the absence of thinning. Within the thinned treatment, P fertilization resulted in significant increases in tree height over time. Herbaceous weed control had no effect on tree growth. The atmospherically resistant vegetation index (ARVI), which was derived from spectral analyses of high-resolution satellite imagery (GeoEye1), was significantly higher for thinned than unthinned trees 25months after study initiation, suggesting greater light absorbance and a possible explanation for overall greater growth of thinned trees. When considered with results from previous studies, these findings indicated that crop tree selection and precommercial release thinning in dense, even-aged koa stands should be done early in stand development to prevent loss of crown vigor and growth potential. Additional interventions like P fertilization or herbaceous weed control may not be necessary until trees are older or site conditions suggest important soil resource limitations.