Height Growth Response Research Articles

Spatial Heterogeneity of Climate Change Effects on Dominant Height of Larch Plantations in Northern and Northeastern China

Determining the response of dominant height growth to climate change is important for understanding adaption strategies. Based on 550 permanent plots from a national forest inventory and climate data across seven provinces and three climate zones, we developed a climate-sensitive dominant height growth model under a mixed-effects model framework. The mean temperature of the wettest quarter and precipitation of the wettest month were found to be statistically significant explanatory variables that markedly improved model performance. Generally, future climate change had a positive effect on stand dominant height in northern and northeastern China, but the effect showed high spatial variability linked to local climatic conditions. The range in dominant height difference between the current climate and three future BC-RCP scenarios would change from −0.61 m to 1.75 m (−6.9% to 13.5%) during the period 2041–2060 and from −1.17 m to 3.28 m (−9.1% to 41.0%) during the period 2061–2080 across provinces. The impacts of climate change on stand dominant height decreased as stand age increased. Forests in cold and warm temperate zones had a smaller decrease in dominant height, owing to climate change, compared with those in the mid temperate zone. Overall, future climate change could impact dominant height growth in northern and northeastern China. As spatial heterogeneity of climate change affects dominant height growth, locally specific mitigation measures should be considered in forest management.

Life history traits predict the response to increased light among 33 tropical rainforest tree species

Rainforest restoration is an important application in today’s multipurpose management of secondary forest. However, our knowledge of tree species’ traits and responses to treatment is insufficient for foresters to make good decisions for sustainable management. The aim of our study was to see whether it is possible to predict tree species’ responses to increased light based on species’ traits, and to relate these responses to a possible pioneer–climax continuum of life history traits, also among species with presumed climax properties. We examined 33 taxa (including 19 from the dipterocarp family) replicated 20 times and randomly planted in lines over a 3ha area in the interior of Sabah, Borneo. Four years after establishment we performed a canopy reduction treatment to increase the light conditions up to levels present in tree gaps in the forest. We created a PLS (Partial Least Square Regressions) model with the two predicted variables HGR (height growth response) and Q3 HGR (the 75 percentile of a species’ HGR, interpreted as the potential HGR). The model captured 47% of the variation for the predicted variables. We found significant tree species’ responses in height growth to the increased light. High specific leaf area, strong early height growth, high foliar N content, high leaved stem length and large crown were linked to fast growth, while high wood density and high foliar K content were associated with slow growth. We also found a trade-off between growth response and survival among the species. We conclude that climax tree species have specific life history adaptations along a pioneer–climax continuum, which can be predicted from species’ traits. The importance of easily observed or extracted traits such as initial growth rate, specific leaf area and wood density for predicting growth suggests the possibility of fast screening of species with unknown characteristics, which could be of great value in practical forest management.

Species richness loss after nutrient addition as affected by N:C ratios and phytohormone GA3contents in an alpine meadow community

Aims From the light-competition hypothesis, competition for light is asymmetric and the observed increases in plant-size variability with increasingly denser canopies are primarily due to competition for light. Greater plant height provides pre-emptive access to light and produces increased height differences among species. The question is what produces these differences in plant height or height growth response among species in response to fertilization. Methods In 2009, a field experiment of N, P and N + P enrichments at three levels each was initiated in an alpine meadow on the northeast Qinghai- Tibet Plateau. Effects of fertilization on species richness, aboveground net primary production (ANPP), relative light intensity and plant height of different plant functional groups were determined. Festuca ovina (grass), Kobresia humilis (sedge), Oxytropis ochrocephala (legume), Taraxacum lugubre (rosette forb) and Geranium pylzowianum (upright forb) were selected as exemplars of each of the indicated functional groups. The N: C ratios in aboveground biomass, gibberellic acid (GA3) concentrations in leaves, plant heights and height relative growth rate (RGR) of these exemplar species were analyzed in detail. Important Findings Species richness of grasses significantly increased with increasing N + P levels. Species richness of legumes and upright forbs decreased after N and N + P additions. P addition had no significant effect on species richness. The effects of N + P addition on species richness and ANPP were consistently stronger than those of the single N or P fertilization. Reductions in species richness caused by nutrient addition paralleled the increases in ANPP and decreases in light intensity under the canopies, indicating indirect effect of nutrient addition on species richness via ANPP-induced light competition. The exemplar species that responded most positively to fertilization in height and RGR also displayed stronger increases in their GA3 content and N:C ratios. GA3 concentrations and N: C ratios were positively correlated with height RGR when the data were pooled for all species. The tallest and the fastest-growing grass, F. ovina, had the largest increase in N: C ratios and the highest leaf GA3 concentrations after nutrient addition. These results indicated that differential responses of GA3 concentrations and N: C ratios to fertilization were related to the inequality in plant heights among species.

Differential growth rates through the seedling and sapling stages of two Nothofagus species underplanted at low-light environments in an Andean high-graded forest

The Andes of south-central Chile, with the valuable and dominant timber species Nothofagus dombeyi and N. alpina, have been heavily high-graded. Restoring these forests with these species is challenging since they are light demanding and the understory becomes dominated by bamboo (Chusquea culeou), which prevents natural regeneration. In this study we aimed to evaluate the root-collar diameter (RCD) and height growth response of these species during their seedling and sapling stages (years 1, 2, 3 and 6) after outplanting and removing the understory in a relatively low-light environment in a high-graded forest (incident light levels between 2.6 and 12.7 mol m−2 d−1). We fitted regression models to predict annual growth as a function of light availability, and used species as an indicator variable. RCD growth was significantly affected by light since the onset, and height growth only at ages 3 and 6. Species became a significant variable only at years 3 and 6 for RCD growth, and at age 6 for height growth. N. dombeyi grew faster than N. alpina throughout all the period, and both species had their greatest response to light the last years evaluated (adj. r 2 of 0.67 and 0.45 in RCD and height growth, respectively), i.e. an increasing intolerance to shade (ontogenetic change). The increasing variability of the data and the goodness-of-fit of the models at this stage suggest that light is becoming a major driver of growth. These results illustrate a good potential use of these species for restoration of Andean forests.

Contrasting effects of tree diversity on young tree growth and resistance to insect herbivores across three biodiversity experiments

Tree diversity is an important driver of forest ecosystem functioning, hypothesised to enhance tree growth and resistance to herbivores. To test this, we assessed the relative importance of tree species richness and functional diversity on tree height growth and insect herbivore damage across three tree diversity experiments in Finland, France and Germany, established within the last fifteen years. These experiments encompass species richness gradients from monocultures up to five species mixtures, with compositions drawn from a pool of eleven tree species. Tree height growth and total insect herbivory were evaluated at both the tree species and forest plot scales.Trees in mixtures tended to grow taller, but on average received more insect herbivory relative to monocultures. Gradients of tree species richness or functional diversity had only weak impact on the magnitude of these effects. Community weighted means of specific leaf area alone captured diversity effects on tree height growth, with stronger positive effects of diversity in mixtures with high community SLA. Tree species‐specific responses were highly variable. No species significantly benefited both in terms of increased growth and reduced herbivory when grown in mixtures. More species showed positive height growth responses in mixed assemblages, but only the two exotic conifers experienced associational resistance to herbivores.This large‐scale study shows that tree height growth in young forest plantations tends to be higher in species mixtures than in monocultures, but incremental increases in functional diversity have, at best, weak marginal growth benefits. Moreover, there appear to be contrasting effects at forest plot versus individual species scales. Thus, while some species show lower herbivore damage in mixtures, this is not a consistent trend and contrasts the higher overall damage in mixtures observed at the forest plot scale. To improve both tree growth and resistance to herbivores in tree species mixtures seems therefore challenging.

Conifer regeneration in managed temperate mixedwood stands: the balance between release and competition

We established a long-term experiment in a temperate mixedwood stand to evaluate the effectiveness of silvicultural treatments in regenerating a mixed-species cohort while maintaining the dominance of conifers. Silvicultural treatments included clearcutting using careful logging around advanced growth (CLAAG), uniform shelterwood (US), group shelterwood with (GS-s) or without scarification (GS), and an uncut control (control). After 10 years, height and ground-line diameter growth responses of advanced balsam fir (Abies balsamea [L.] Mill.) regeneration were substantial in CLAAG and GS compared to the control, and intermediate in US. Growth responses were proportional to increases in canopy light transmittance resulting from harvest. Advanced balsam fir regeneration had low mortality (<10 %) and a high potential for release as measured by the apical dominance ratio. At the stand level, however, a shift in species composition occurred in the regenerating cohort. Over the 10-year period, composition changed from conifer-dominated to hardwood-dominated in CLAAG, GS, and GS-s compared to the control. Scarification increased the magnitude of this shift by favoring shade-intolerant hardwoods. Results highlight the need to find a balance between releasing advance conifer regeneration and limiting competition from less desirable species.

Effect of climatic conditions on height growth of red pine: Results of a provenance test in northwestern Ontario

Response of height growth of red pine (Pinus resinosa Ait.) to changes in climatic conditions was analyzed using data collected in a 48-year-old provenance trial established in northwestern Ontario, Canada. Seed sources for the trial were collected from 23 provenances spanning the natural range of red pine. Mean monthly values of climatic variables were estimated from historical climatic data for 1971 to 2000. Quadratic transfer functions predicting mean tree height at age 48 and tree top height at age 50 were developed using the difference in climatic variables between the seed source provenances and the trial site. The transfer function for mean height at age 48 explained 59% of data variation using the mean minimum temperature in July and sum of precipitation during June to February. For tree top height at age 50, the transfer function explained 55% of data variation using mean minimum temperature in January and sum of precipitation during June to March. The developed equations can be used to select op...

Effects of aerial strip spraying on mixedwood stand structure and tree growth

Herbicide application in strips offers a cost-effective way to accelerate spruce growth in young mixedwood stands, while also retaining the mixedwood character of the stand. In June of 2006 data were collected to evaluate the effects of aerial strip spraying on subsequent growth of treated stands. These blocks had been planted in 1991 and treated in 2000 with Triclopyr ester herbicide applied in strips. Treated and untreated strips averaged 5.8 m and 8.4 m in width, respectively, with 38% of the block area being effectively treated. In 2006 aspen density, DBH, and height were significantly lower in the treated strips compared to either untreated strips or completely untreated blocks. Spruce growth was significantly larger in treated strips with diameter growth responses beginning in the first and height growth responses in the second growing season following treatment. Yield estimates from the Mixedwood Growth Model (MGM) indicate that the strip spray treatments result in the highest spruce yields. However, when understory protection (harvesting aspen at age 70 and spruce at 120) is applied, the untreated blocks provided higher total yield and net present value.

Height-convergence pattern in dense plant stands is affected by red-to-far-red ratio of background illumination

This study investigated the effects of illumination with different red-to-far-red ratios (R:FR) on height convergence pattern in cucumber (Cucumis sativus L.) seedling stands to obtain a basic knowledge for growing plant stands uniformly under artificial light sources. Seedlings of the same age but with different initial heights (30 or 15mm) were grown under either metal-halide lamps with spectra similar to that of natural light (R:FR=1.2) or fluorescent lamps with a high R:FR (R:FR=11), at a photosynthetic photon-flux (PPF) of 300μmolm−2s−1 and a light:dark period of 16:8h, until the first true leaf expanded. The shoot heights of the initially taller and shorter seedlings under the metal-halide lamps converged within 4 days. In contrast, the initially shorter seedlings under fluorescent illumination remained smaller than the initially taller seedlings throughout the experimental period (8 days), although the height difference decreased gradually. The rapid height-convergence under metal-halide illumination probably resulted from shade avoidance by the shorter seedlings due to the relatively low R:FR (=0.6) and PPF (=60μmolm−2s−1) at cotyledon level under shade from the taller seedlings. The R:FR at cotyledon level for the initially shorter seedlings under fluorescent illumination was 5.5, which was higher than the value (0.6) that caused the accelerated height growth response under metal-halide light. The fact that light quality affects the structure of plant community should be considered in selecting light sources for the plant production.

Demographic and height growth response of native broad-leaved deciduous tree saplings to overhead canopy release in a coastal Pinus thunbergii forest in Hokkaido, northern Japan

Prevention efforts to combat pine wilt disease must be instituted to avoid destruction of coastal forests in Hokkaido, northern Japan. We examine an alternative method involving the conversion of Pinus thunbergii forests to native broadleaf species through advancing their growth, but we have little knowledge about the response of advanced growth to overhead canopy release. To demonstrate the demographic and height growth response of advanced growth to the light change in a coastal Pinus thunbergii forest, canopy trees were removed and the sapling populations were monitored for 6 years. Inhibition in height growth caused by light increase was observed in Cerasus sargentii and Kalopanax septemlobus saplings. Especially in Kalopanax septemlobus, a remarkable decline was observed in the saplings growing in the darker positions which experienced light change. Therefore, large light changes should be carefully avoided for this species especially in the darker positions. In contrast, relative height growth rates of Quercus crispula and, especially, Quercus dentata increased with increasing light, and saplings tended to die in the darker positions. No dead trees of Sorbus commixta were observed during the study period. The saplings also showed good height growth even when under closed canopy. This species seems to be adaptive to a dark environment. Since Quercus dentata and Kalopanax septemlobus are the major components of the natural coastal forests in Hokkaido, gradual canopy release is available to foster advanced growth in coastal Pinus thunbergii forest, in accordance with the concept of density control in coastal forests.

The Tonoplast-Localized Sucrose Transporter in Populus (PtaSUT4) Regulates Whole-Plant Water Relations, Responses to Water Stress, and Photosynthesis

The Populus sucrose (Suc) transporter 4 (PtaSUT4), like its orthologs in other plant taxa, is tonoplast localized and thought to mediate Suc export from the vacuole into the cytosol. In source leaves of Populus, SUT4 is the predominantly expressed gene family member, with transcript levels several times higher than those of plasma membrane SUTs. A hypothesis is advanced that SUT4-mediated tonoplast sucrose fluxes contribute to the regulation of osmotic gradients between cellular compartments, with the potential to mediate both sink provisioning and drought tolerance in Populus. Here, we describe the effects of PtaSUT4-RNA interference (RNAi) on sucrose levels and raffinose family oligosaccharides (RFO) induction, photosynthesis, and water uptake, retention and loss during acute and chronic drought stresses. Under normal water-replete growing conditions, SUT4-RNAi plants had generally higher shoot water contents than wild-type plants. In response to soil drying during a short-term, acute drought, RNAi plants exhibited reduced rates of water uptake and delayed wilting relative to wild-type plants. SUT4-RNAi plants had larger leaf areas and lower photosynthesis rates than wild-type plants under well-watered, but not under chronic water-limiting conditions. Moreover, the magnitude of shoot water content, height growth, and photosynthesis responses to contrasting soil moisture regimes was greater in RNAi than wild-type plants. The concentrations of stress-responsive RFOs increased in wild-type plants but were unaffected in SUT4-RNAi plants under chronically dry conditions. We discuss a model in which the subcellular compartmentalization of sucrose mediated by PtaSUT4 is regulated in response to both sink demand and plant water status in Populus.

Height‐growth response to climatic changes differs among populations of Douglas‐fir: a novel analysis of historic data

Projected climate change will affect existing forests, as substantial changes are predicted to occur during their life spans. Species that have ample intraspecific genetic differentiation, such as Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), are expected to display population-specific growth responses to climate change. Using a mixed-effects modeling approach, we describe three-year height (HT) growth response to changes in climate of interior Douglas-fir populations. We incorporate climate information at the population level, yielding a model that is specific to both species and population. We use data from provenance tests from previous studies that comprised 236 populations from Idaho, Montana, and eastern Washington, USA. The most sensitive indicator of climate was the mean temperature of the coldest month. Population maximum HT and HT growth response to changes in climate were dependent on seed source climate. All populations had optimum HT growth when transferred to climates with warmer winters; those originating in sites with the warmest winters were taller across sites and had highest HT growth at transfer distances closest to zero; those from colder climates were shortest and had optimum HT growth when transferred the farthest. Although this differential response damped the height growth differences among populations, cold-climate populations still achieved their maximum growth at lower temperatures than warm-climate populations. The results highlight the relevance of understanding climate change impacts at the population level, particularly in a species with ample genetic variation among populations.

A comparison of tree seedling growth in artificial gaps of different sizes in two contrasting forest types.

One of the major concerns in forestry in the tropics is the lack of information on the impact of canopy disturbance through logging. The degree of canopy opening that should be allowed during logging to enhance natural regeneration of timber tree species is not known. Information on the seedling ecology of individual species and ecological species groups on which to base management decisions are also lacking. Experiments to determine the ecophysiological responses of seedlings of timber tree species to different irradiances in two forest sites were carried out. The two forest reserves are Nkrabia and Tinte Bepo in the Moist Evergreen and Moist Semi-Deciduous Forest Types, respectively. Eight species, representing three Shade Bearers, four Non-Pioneer Light Demanders and one Pioneer species, were grown in a series of artificially-created gaps in two forest sites differing in annual rainfall. The forest shade received 1-2% irradiance, while the artificial gaps received 5, 10, 15, 30 and 65% irradiance. Seedling growth was greater at Nkrabia Forest Reserve (Moist Evergreen Forest Type) than at Tinte Bepo Forest Reserve (Moist Semi-Deciduous Forest Type). This is probably due to the lower soil moisture stress at Nkrabia as a result of more rainfall. Lower moisture stress at Nkrabia may also explain the greater leaf area and specific leaf area ratios, lower leaf turnover and lower number of small leaves on plants than those at Tinte Bepo. Response of height growth to irradiance of Shade Bearers and Non-Pioneer Light Demanders was similar but different from that of Pioneer species.

The effects of belowground resources on aboveground allometric growth in Bornean tree species

Tree height and crown allometries reflect adaptations for resource acquisition and structural stability, as well as plastic responses to a heterogeneous environment. While both light and soil resources limit growth and influence competitive responses in tropical forests, the effects of belowground resources on allometries are less understood, especially within the understory. To characterize outcomes of tree competition along an edaphic resource gradient, we quantified variation in height and crown allometries of six Bornean tree species from contrasting regeneration niches (light-demanding vs. shade-tolerant) on two soil habitats (clay-fine loam and sandy loam) within a 52-ha forest dynamics plot. Using empirically-fit allometric parameters and diameter growth rates from plot census data, we modeled tree height and crown area growth over the projected life span of each species. Based on resource competition theory, we hypothesized that tree species specializing on and populations of generalist species growing on the relatively moister, more fertile clay-fine loam soil habitat would have faster height and crown growth rates, compared to those on the sandy loam habitat, regardless of regeneration niche. Among soil specialists and within generalists of both genera, trees growing on clay-fine loam had taller stems and larger crowns at a given age and faster height and crown area growth rates at most sizes than trees on sandy loam. Differences in height and crown growth were driven by the faster diameter growth rates of trees on clay-fine loam, not by differences in height- and crown-diameter allometries, as trees on sandy loam were significantly taller at a given diameter, and differences in crown allometry were not consistent across soil habitats. Characterizing the height and crown growth responses of trees along resource gradients provides insight into the mechanisms that maintain diversity in tropical forests. Our results point to the importance of adaptive and plastic responses to both above and belowground resource availability in determining the allometric growth of trees and suggest that this diversity of responses may contribute tree species coexistence through competition-based trade-off mechanisms and variation in growth among individuals. Additionally, as the importance estimating natural carbon sequestration increases with the escalating effects of anthropogenic climate change, differences in tree growth and architecture across soil habitats also have implications for the approximation of forest carbon storage on heterogeneous tropical soils.

The influence of recent climate change on tree height growth differs with species and spatial environment.

Tree growth has been reported to increase in response to recent global climate change in controlled and semi-controlled experiments, but few studies have reported response of tree growth to increased temperature and atmospheric carbon dioxide (CO2) concentration in natural environments. This study addresses how recent global climate change has affected height growth of trembling aspen (Populus tremuloides Michx) and black spruce (Picea mariana Mill B.S.) in their natural environments. We sampled 145 stands dominated by aspen and 82 dominated by spruce over the entire range of their distributions in British Columbia, Canada. These stands were established naturally after fire between the 19th and 20th centuries. Height growth was quantified as total heights of sampled dominant and co-dominant trees at breast-height age of 50 years. We assessed the relationships between 50-year height growth and environmental factors at both spatial and temporal scales. We also tested whether the tree growth associated with global climate change differed with spatial environment (latitude, longitude and elevation). As expected, height growth of both species was positively related to temperature variables at the regional scale and with soil moisture and nutrient availability at the local scale. While height growth of trembling aspen was not significantly related to any of the temporal variables we examined, that of black spruce increased significantly with stand establishment date, the anomaly of the average maximum summer temperature between May-August, and atmospheric CO2 concentration, but not with the Palmer Drought Severity Index. Furthermore, the increase of spruce height growth associated with recent climate change was higher in the western than in eastern part of British Columbia. This study demonstrates that the response of height growth to recent climate change, i.e., increasing temperature and atmospheric CO2 concentration, did not only differ with tree species, but also their growing spatial environment.

Response of a boreal forest to canopy opening: assessing vertical and lateral tree growth with multi-temporal lidar data

Fine-scale height-growth response of boreal trees to canopy openings is difficult to measure from the ground, and there are important limitations in using stereophotogrammetry in defining gaps and determining individual crowns and height. However, precise knowledge on height growth response to different openings is critical for refining partial harvesting techniques. In this study, we question whether conifers and hardwoods respond equally in terms of sapling growth or lateral growth to openings. We also ask to what distance gaps affect tree growth into the forest. We use multi-temporal lidar to characterize tree/sapling height and lateral growth responses over five years to canopy openings and high resolution images to identify conifers and hardwoods. Species-class-wise height-growth patterns of trees/saplings in various neighborhood contexts were determined across a 6-km matrix of Canadian boreal mixed deciduous coniferous forests. We then use statistical techniques to probe how these growth responses vary by spatial location with respect to the gap edge. Results confirm that both mechanisms of gap closure contribute to the closing of canopies at a rate of 1.2% per annum. Evidence also shows that both hardwood and conifer gap edge trees have a similar lateral growth (average of 22 cm/yr) and similar rates of height growth irrespective of their location and initial height. Height growth of all saplings, however, was strongly dependent on their position within the gap and the size of the gap. Results suggest that hardwood and softwood saplings in gaps have greatest growth rates at distances of 0.5-2 m and 1.5-4 m from the gap edge and in openings smaller than 800 m2 and 250 m2, respectively. Gap effects on the height growth of trees in the intact forest were evident up to 30 m and 20 m from gap edges for hardwood and softwood overstory trees, respectively. Our results thus suggest that foresters should consider silvicultural techniques that create many small openings in mixed coniferous deciduous boreal forests to maximize the growth response of both residual and regenerating trees.

Response of a boreal forest to canopy gap openings - assessing vertical and horizontal tree growth with multi-temporal lidar data

Fine-scale height-growth response of boreal trees to canopy openings is difficult to measure from the ground, and there are important limitations in using stereo-photogrammetry in defining gaps and determining individual crowns and height. However, precise knowledge on height growth response to different openings is critical for refining partial harvesting techniques. In this study, we question whether conifers and hardwoods respond equally in terms of sapling growth or lateral growth to openings. We also ask to what distance gaps affect tree growth into the forest. We use multi-temporal lidar to characterize tree/sapling height and lateral growth responses over five years to canopy openings and high resolution images to identify conifers and hardwoods. Species-class-wise height-growth patterns of trees/saplings in various neighborhood contexts were determined across a 6-km2 matrix of Canadian boreal mixed deciduous coniferous forests. We then use statistical techniques to probe how these growth responses vary by spatial location with respect to the gap edge. Results confirm that both mechanisms of gap closure contribute to the closing of canopies at a rate of 1.2% per annum. Evidence also shows that both hardwood and conifer gap edge trees have a similar lateral growth (average of 22 cm/yr) and similar rates of height growth irrespective of their location and initial height. Height growth of all saplings, however, was strongly dependent on their position within the gap and the size of the gap. Results suggest that hardwood and softwood saplings in gaps have greatest growth rates at distances of 0.5–2 m and 1.5–4 m from the gap edge and in openings smaller than 800 m2 and 250 m2, respectively. Gap effects on the height growth of trees in the intact forest were evident up to 30 m and 20 m from gap edges for hardwood and softwood overstory trees, respectively. Our results thus suggest that foresters should consider silvicultural techniques that create many small openings in mixed coniferous deciduous boreal forests to maximize the growth response of both residual and regenerating trees.

Short-term changes in Pinus strobus sapling height/diameter ratios following partial release: testing the acclimative stem-form development hypothesis

Following release, mature trees can acclimatively shift aboveground growth allocation from height to diameter at breast height (DBH) growth to adjust their stem form (reducing height/diameter ratio (HDR)) to better withstand increased wind stress. The purpose of this study was to determine if, over a 6-year period, 7- to 12-year-old eastern white pines ( Pinus strobus L.) also responded to different levels of partial release with (i) stem-form adjustments (reduced HDR) through growth-allocation shifts from height to DBH growth and (ii) lower HDR values (shorter heights) than for unreleased trees of the same DBH (“acclimative stem-form development hypothesis”). Over the 6-year postrelease period, juvenile white pine seedlings exhibited unsynchronized height and DBH growth response patterns that depended on their prerelease height growth. Height growth of faster growing white pines was temporarily reduced. Concurrently, DBH growth was enhanced with increasing release intensity. HDR reductions followed a fairly narrow and predictable trajectory, but HDR values of released trees were not lower than those of unreleased trees of the same DBH after 6 years. Juvenile white pine seedlings appear to maintain a balance among aboveground tree parts to enhance future tree stability, which may be an adaptive trait for moderately shade-tolerant species.

Release potential of giant sequoia following heavy suppression: 20-year results

We tested the release potential of suppressed giant sequoia ( Sequoiadendron giganteum) saplings in a plantation that was overgrown with shrubs at Blodgett Forest Research Station, CA in the mixed conifer forest of the Sierra Nevada. As an ancillary case study, we compared the shrub removal method of release with a clear-and-plant method in an adjacent stand. Measurements of various morphological traits were collected prior to shrub removal, then sapling height growth response was measured periodically after the release treatment. In general, giant sequoia responded quickly to the removal of competing shrubs, growing steadily for 20 years following treatment. Among the morphological traits considered, live crown ratio alone was the most important factor in predicting relative height growth following treatment. Other traits were correlated with release, but had lower importance values as indicated by a model selection procedure. The 16-year-old saplings that were released in this study did not grow as large as 2-year-old seedlings that were planted synchronously with release, but both methods resulted in merchantable-sized trees 20 years after treatment. Planted seedlings outgrew released seedlings by 27% in terms of stature and by 37% in terms of diameter. The released stand is projected with a growth model to take 12 years longer than the planted stand to grow to an average diameter of 38 cm. The misperception of giant sequoia as having a low capacity for release may be related to its ambiguous categorization as a shade intolerant species.

Growth Response of One Year Old Post Planted Shorea leprosula Seedling To Various Light, Under 19 Years Old Acacia mangium Stand

Development of meranti (S . leprosula) plantation forest is limited/ constrained by many factors, e.g. seed supply and seedling growth environment. The research deals with the observation of the current condition on A. mangium stand and did not employ any treatments. Meranti seedling was obtained from vegetative cutting (Komatsu-Forda), at one year (old) post planted meranti under A. mangium stands and spacing of 4 x 2 m, approximately two hectares of permanent sample plot (PSP) were made. Ineach hectare of young meranti plants with spacing 10 x 3 m (330 seedling/ha), 9 (nine) observation plots with size 10 x 10 m (6 seedlings/plot) were prepared, and placed in the middle of PSP. Totally, there were 108 seedlings available for the measurement of particular parameter, i.e. light intensity, height growth, and survival rate. Light intensity was measured by going around of 10 x 10 m plot. Result of measurement in each observation plot (10 x 10 m size) rescaled that light intensity ranged about 6,55 - 35,2% or being equal with 4908 - 26568 flux hour. Meanwhile, the best height growth response and survivalrate were at 10 % light intensity or over.