Basal Area Growth Research Articles

A Study on the Basal Area Growth Model of Phoebe zhennan Secondary Forest in Hunan Province

A Study on the Basal Area Growth Model of Phoebe zhennan Secondary Forest in Hunan Province

Regional Variability of the Romanian Main Tree Species Growth Using National Forest Inventory Increment Cores

In many countries, National Forest Inventory (NFI) data is used to assess the variability of forest growth across the country. The identification of areas with similar growths provides the foundation for development of regional models. The objective of the present study is to identify areas with similar diameter and basal area growth using increment cores acquired by the NFI for the three main Romanian species: Norway spruce (Picea abies L. Karst), European beech (Fagus sylvatica L.), and Sessile oak (Quercus petraea (Matt.) Liebl.). We used 6536 increment cores with ages less than 100 years, a total of 427,635 rings. The country was divided in 21 non-overlapping ecoregions based on geomorphology, soil, geology and spatial contiguousness. Mixed models and multivariate analyses were used to assess the differences in annual dimeter at breast height and basal area growth among ecoregions. Irrespective of the species, the mixed models analysis revealed significant differences in growth between the ecoregions. However, some ecoregions were similar in terms of growth and could be aggregated. Multivariate analysis reinforced the difference between ecoregions and showed no temporal grouping for spruce and beech. Sessile oak growth was separated not only by ecoregions, but also by time, with some ecoregions being more prone to draught. Our study showed that countries of median size, such as Romania, could exhibit significant spatial differences in forest growth. Therefore, countrywide growth models incorporate too much variability to be considered operationally feasible. Furthermore, it is difficult to justify the current growth and yield models as a legal binding planning tool.

The Long-Term Survival and Growth of Enrichment Plantings in Logged Tropical Rainforest in North Queensland, Australia

Enrichment planting is often suggested as a means of enhancing the productivity of logged rainforest. However, little is known about the long-term survival and growth of these trees. In this study, we used historical data from enrichment planting trials ranging from 15 to 32 years old to examine the survival and growth of 16 tree species across different sites in north Queensland, Australia. The results complement and extend current knowledge on the potential role of enrichment planting from a production perspective. A key finding was that the initial level of post-logging overwood did not appear to affect the immediate survival of enrichment plantings, but in the longer term (up to 30 years) survival decreased as post-logging overwood and regrowth increased. This suggests that removal of overwood should take place at the time of enrichment planting. A further key finding was that despite regular tending to remove vegetation adjacent to the plantings, competition from saplings and trees that were situated outside the tended area emerged as a major source of competition in some plots. By implication, the success of enrichment planting may depend on removal of competition from the entire logged area, not just adjacent to enrichment plantings. Results between individual species and trials varied widely. The best development of Flindersia brayleyana resulted in a mean tree diameter of 32.5 cm at age 22 for the 100 tallest trees per hectare. Although Eucalyptus grandis, Eucalyptus microcorys, and Eucalyptus pilularis all failed—as expected, because they do not normally grow in rainforest—Corymbia torelliana, Cardwellia sublimis, Araucaria bidwillii, Khaya senegalensis, Flindersia amboinensis, and Swietenia macrophylla also failed although they grow naturally in similar sites. In other trials, tree height and basal area growth were often poor. For example, Khaya ivorensis grew to a basal area of only 1.3 m2/ha and a mean height of 7.7 m at age 10, and Flindersia ifflaiana only grew to a basal area of 0.7 m2/ha and a height of 7.9 m, also at age 10. Overall, these results emphasise the necessity of site–species matching before enrichment planting begins and the necessity of post-planting monitoring and remedial tending.

Modeling stand basal area growth of Cryptomeria japonica D. Don under different planting densities in Taiwan

ABSTRACT Stand basal area (BA) is an important parameter, yet significantly influenced by initial planting density, in describing the developments of plantation forests. The effects of initial density on the growth of sugi (Cryptomeria japonica D. Don), an important plantation tree species in Taiwan, have seldom been studied. The goals of this study are to (1) model sugi stand BA growth under different initial densities, and (2) quantify model forecast accuracy. The data were from a spacing trial established in 1950 at the National Taiwan University Experimental Forest. The initial densities were 2500, 1111, 625, and 400 trees ha−1. Ten measurements were carried out up to stand age 65. Using a mixed-effects modeling approach, we fitted a Gompertz model with the initial density as the covariate to describe stand BA growth trends. Results showed that stand BA was the largest for stands with the highest initial density. The maximum current annual increment of the highest initial density was also the largest and reached earlier in stand development than that of the other spacings. Data up to stand age 60 were needed to yield a forecast accuracy within 6% for BA at stand age 65. This study showed that the fitted Gompertz model could adequately capture the general growth trends in stand BA despite unequal measurement intervals. The results agreed with other spacing trials in other regions and tree species, and the model accuracy was acceptable given the availability of data. The prediction accuracy results underlined the importance of long-term growth monitoring.

Fertilization of Norway spruce forest with wood ash and nitrogen affected both tree growth and composition of chemical defence

AbstractWe fertilized a Norway spruce (Picea abies (L.) Karst.) stand on rich mineral soil with 3 t ha−1 of wood ash (ASH), 150 kg ha−1 of nitrogen (N) or a combination of wood ash and nitrogen (ASH + N), in addition to unfertilized control plots. After five growing seasons, we remeasured the trees and took core samples. Current- and previous-year needles were sampled and analyzed for total nitrogen and carbon, low-molecular weight phenolics and condensed tannins. Annual volume increment and standing volume were significantly higher in the ASH + N treatment than in control plots after 5 years. N gave a significant positive effect on basal area growth in the third year, after which the effect diminished. The ASH + N treated trees, on the other hand, showed an increasing basal area growth trend throughout the period. ASH reduced the total concentration of low-molecular weight phenolic compounds significantly in current-year needles. Phenolic acids increased under both ASH and ASH + N, while flavonoids decreased significantly under the same treatments compared to N. By including annual growth rate before fertilization in the analyses, the effect of N-treatment on flavonoids was positive only in trees with higher growth rates, and in those trees the concentration was higher than in both ASH-treated plots and controls. An acetophenone, constituting more than half of the total low-molecular weight phenolics concentration, was strongly reduced under all fertilization treatments. These results demonstrate that in addition to effects on tree growth, fertilization of the forest floor also has a strong influence on other metabolic processes of trees, with potential implications for ecosystem functioning.

Assessing Differences in Competitive Effects Among Tree Species in Central British Columbia, Canada

Research Highlights: We investigated the competitive interactions among three tree species (interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco), interior spruce (Picea glauca [Moench] Voss × Picea engelmannii Engelm.), and lodgepole pine (Pinus contorta Dougl. Ex Loud. var. latifolia Englem.)) in multi-aged stands in central British Columbia, Canada. Background and Objectives: Understanding competitive interactions among tree species in mixed-species stands is fundamental to supporting silvicultural decision-making in such stands. Using the periodic annual basal area increment for single trees as our dependent variable, we investigated whether neighboring trees competed with subject trees independently of species identity. We also examined the differences in single-tree basal area growth among the three conifer species over time under different levels of competition. Materials and Methods: We developed several spatially explicit, single-tree basal area growth models for interior Douglas-fir, interior spruce, and lodgepole pine using data from 16 plots in two blocks of a long-term study (five measurements over a 21-year period) on the response to pre-commercial thinning. We compared these equations to assess whether intraspecific or interspecific competition predominated. We also examined the differences in basal area growth among the three conifer species over time under different levels of competition. Results: We found asymmetrical relationships between the conifer trees and their neighbors for all species, indicating that the main driver limiting growth in these stands is aboveground competition for light. There was evidence of higher intraspecific competition for small (<10.0 cm DBH) interior Douglas-fir in one block. However, there was no general pattern among larger subject trees with respect to the identity of neighborhood competitive effects and the equivalence of neighbors. We observed a higher level of basal area growth over time for interior Douglas-fir than for lodgepole pine and interior spruce, irrespective of the competition intensity and, not surprisingly, the growth rate declined with increasing competition levels for the three species. Conclusions: Our results provide an understanding of how interior Douglas-fir stands will develop over time and information on species interactions that could help forest managers explore different silvicultural options and their effects on individual tree growth in these complex stands.

Physiological responses of eastern hemlock (Tsuga canadensis) to light, adelgid infestation, and biological control: Implications for hemlock restoration

The rapid loss of eastern hemlock (Tsuga canadensis) in the southern Appalachian Mountains due to hemlock woolly adelgid (Adelges tsugae, HWA) infestation has resulted in substantial changes to ecosystem structure and function. Several restoration strategies have been proposed, including silvicultural treatments that increase incident light in forest understories. We conducted a four-year manipulative field experiment on surviving mid-story hemlock trees to investigate the effects of release from light limitation on HWA infestation and physiological parameters, expecting that higher light levels would improve tree carbon balance. Mixed hardwood forest sites were either previously uninfested with HWA (UN), infested with HWA (I), or infested with HWA and had a history of predatory beetle releases for biological control (I+P). At each site, we identified ten eastern hemlock trees in the mid-story and cut ~15 m radius canopy gaps around half of them while leaving the canopy intact over the other half. We compared short- and long-term indices of carbon gain and stress: leaf net photosynthesis (Anet); leaf fluorescence (Fv/Fm); leaf total non-structural carbohydrate concentration ([TNC]); new shoot growth; HWA density; and basal area growth. We found that trees experienced greater leaf-level stress in gaps and when HWA was actively feeding. Despite being more stressed, trees in gaps fixed 2x more carbon than those in reference conditions. High Anet in the spring translated into high leaf [TNC] in the spring, coinciding with when HWA was actively feeding. Although infested and uninfested trees had similar leaf [TNC] maxima, infestation prevented trees from allocating this carbon to shoot and basal area growth; this was particularly true for reference trees. Greater shoot growth in gap trees translated to greater annual basal area growth—by the end of the study, trees in gaps were growing 9x more than trees in reference conditions, and this was generally regardless of infestation status. In terms of growth and carbon balance, eastern hemlock consistently benefited from the increased light and soil moisture found in gaps; there was inconsistent and rather weak evidence that predator beetles conferred an additional advantage. Our results indicate that silvicultural treatments may improve long-term health and survival of infested trees and that integration of such treatments with existing strategies is worthy of continued exploration.

Differences in tree growth of Norway spruce under rotation forestry and continuous cover forestry

In Fennoscandia there is still lack of information for comparing the traditional even-aged management approach, or Rotation Forestry (RF), with the alternative uneven-aged management, or Continuous Cover Forestry (CCF), especially at tree level. We compared the basal area growth of more than 9000 individual Norway spruces (Picea abies (L.) Karst.), repeatedly measured in long-term permanent sample plots in both RF and CCF stands (the latter managed with single tree selection). We fitted a descriptive model considering characteristics related to tree growth potential (tree size and crown ratio), stand characteristics, site fertility, and management activities (namely forest management type, intensity and timing of last cutting before growth). Variables related to the individual tree characteristics were the most important predictors for growth. The model included two competition indexes, asymmetric (based on total basal area) and symmetric (based on on the amount of overtopping), which had both a stronger negative effect in CCF than in RF. Stand development stage (expressed by the mean height) had a slightly negative effect only in RF. Variables directly describing the intensity and timing of the cuttings had such a negligible effect in both management systems that they were discarded, likely due to their already indirect effects on modifying the stand-level structure (i.e. in reducing the competition effect). Concluding, we successfully fitted a biologically sound and accurate descriptive model that can be used in the ongoing comparison of the two management approaches. CCF trees had a consistently lower growth due to a stronger effect of the competition variables in the model. Our methods show that there is need to account for the differences in the forest structure when building a model aimed at different management systems.

Impact of regional climatic conditions on tree growth on mainland Greece

Abstract Forest growth is commonly used to explore tree vitality and ability to resist to environmental changes or climatic fluctuations. This paper illustrates and examines how regional climatic conditions can be related to the decline of tree growth, which were found to be more distinct in Quercus frainetto Ten. (Hungarian oak) and Fagus sylvatica L. (European beech) and less pronounced in Abies borissi-regis Matt f. (Bulgarian fir) on three long-term intensive monitoring plots (ICP Forests-Level II) in Greece during the period 1996–2009. Relative basal area increment and volume increment were calculated, expressing tree growth in terms of mean relative annual periodic increment. A decline in the growth of basal area and volume was observed after hot and dry periods, where annual temperatures and precipitation were far from the mean of the analyzed period. This observation was statistically confirmed in oak and beech plots regarding summer precipitation only and are in agreement with the findings of previous studies in Europe. The representativeness of the results at a national scale needs further investigation, although our results provide a good basis for further and more intensive monitoring programs to address various forest management scenarios against the background of potential climatic changes in the Mediterranean area.

Stand growth responses after fertilization for thinned lodgepole pine, Douglas-fir, and spruce in forests of interior British Columbia, Canada

This study was conducted to quantify growth responses of three major commercial conifer species (lodgepole pine (Pinus contorta Douglas ex Loudon var. latifolia Engelm. ex S. Watson), interior Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. glauca (Beissn.) Franco), and spruce (white spruce (Picea glauca (Moench) Voss) and hybrid spruce (Picea engelmannii Parry ex. Engelm. × Picea glauca (Moench) Voss × Picea sitchensis (Bong.) Carrière))) to various fertilizer blends in interior British Columbia, Canada. Over 25 years, growth-response data were repeatedly collected across 46 installations. The fertilizer blends were classified into three groups: nitrogen only; nitrogen and sulfur combined; and nitrogen, sulfur, and boron combined. The growth responses for stand volume, basal area, and top height were calculated through absolute and relative growth rate ratios relative to a controlled group. Fertilizer blend, inverse years since fertilization, site index, stand density at fertilization, and their interactions with the fertilizer blend were used as explanatory variables. The magnitude and significance of volume and basal area growth responses to fertilization differed by species, fertilizer-blend groups, and stand-condition variables (i.e., site index and stand density). In contrast, the response in top height growth did not differ among fertilization blends, with the exception of the nitrogen and sulfur fertilizer subgroup for lodgepole pine. The models developed in this study will be incorporated into the current growth and yield fertilization module (i.e., Table Interpolation Program for Stand Yields (TIPSY)), thereby supporting guidance of fertilization applications in interior forests in British Columbia.

Stand growth and structure of mixed-species and monospecific stands of Scots pine (Pinus sylvestris L.) and oak (Q. robur L., Quercus petraea (Matt.) Liebl.) analysed along a productivity gradient through Europe

Past failures of monocultures, caused by wind-throw or insect damages, and ongoing climate change currently strongly stimulate research into mixed-species stands. So far, the focus has mainly been on combinations of species with obvious complementary functional traits. However, for any generalization, a broad overview of the mixing reactions of functionally different tree species in different mixing proportions, patterns and under different site conditions is needed, including assemblages of species with rather similar demands on resources such as light. Here, we studied the growth of Scots pine and oak in mixed versus monospecific stands on 36 triplets located along a productivity gradient across Europe, reaching from Sweden to Spain and from France to Georgia. The set-up represents a wide variation in precipitation (456–1250 mm year−1), mean annual temperature (6.7–11.5 °C) and drought index by de Martonne (21–63 mm °C−1). Stand inventories and increment cores of trees stemming from 40- to 132-year-old, fully stocked stands on 0.04–0.94-ha-sized plots provided insight into how species mixing modifies stand growth and structure compared with neighbouring monospecific stands. On average, the standing stem volume was 436 and 360 m3 ha−1 in the monocultures of Scots pine and oak, respectively, and 418 m3 ha−1 in the mixed stands. The corresponding periodical annual volume increment amounted to 10.5 and 9.1 m3 ha−1 year−1 in the monocultures and 10.5 m3 ha−1 year−1 in the mixed stands. Scots pine showed a 10% larger quadratic mean diameter (p < 0.05), a 7% larger dominant diameter (p < 0.01) and a 9% higher growth of basal area and volume in mixed stands compared with neighbouring monocultures. For Scots pine, the productivity advantages of growing in mixture increased with site index (p < 0.01) and water supply (p < 0.01), while for oak they decreased with site index (p < 0.01). In total, the superior productivity of mixed stands compared to monocultures increased with water supply (p < 0.10). Based on 7843 measured crowns, we found that in mixture both species, but especially oak, had significantly wider crowns (p < 0.001) than in monocultures. On average, we found relatively small effects of species mixing on stand growth and structure. Scots pine benefiting on rich, and oak on poor sites, allows for a mixture that is productive and most likely climate resistant all along a wide ecological gradient. We discuss the potential of this mixture in view of climate change.

Dendroecology of Pinus elliottii Engelm. reveals waves of invasion in a neotropical savanna

Despite advances in understanding the ecology and consequences of pine invasions, information on the patterns of structure, dynamics, and growth needed to manage these invasive populations are still poorly known. Here we used tree ring analysis to elucidate growth dynamics, age distribution and fire effects, by sampling three populations of slash pine invading Cerrado vegetation in southeastern Brazil. We found that the invasion occurred in waves, every 5–7 years. These pulses are likely related to the time needed by founder trees to reach maturity, and to climatic events. We found distinct growth patterns among the three study areas. Individual trees in the open sites, under low competition for light, showed an increasing trend of diameter and of the basal area growth rates with age. In the dense stands, however, the diameter increment rates gradually decreased with age, as the competition for light was intensified, and the basal area growth rate increased at lower rates. Growth rates were markedly reduced after fire, likely due to fire impact on the canopies, reducing photosynthesis. Fire scars in the wood allowed us to confirm that the formation of the tree rings occurs annually. When competition for light intensifies as the canopy of the stand closes, the invasive populations experience reduced individual growth of adult trees and constraints to the recruitment of young individuals. We did not find, however, evidence of self-thinning due to competition that could reduce the population of adult trees, open gaps and allow colonization by shade-tolerant native species. Therefore, a monodominant pine stand—the “pine desert” feature of the invaded sites—tends to be persistent over time.

Tree-species interactions increase light absorption and growth in Chinese subtropical mixed-species plantations.

Light-related interactions can increase productivity in tree-species mixtures compared with monocultures due to higher stand-level absorption of photosynthetically active radiation (APAR) or light-use efficiency (LUE). However, the effects of different light-related interactions, and their relative importance, have rarely been quantified. Here, measurements of vertical leaf-area distributions, tree sizes, and stand density were combined with a tree-level light model (Maestra) to examine how crown architecture and vertical or horizontal canopy structure influence the APAR of 16 monocultures and eight different two-species mixtures with 16 different species in a Chinese subtropical tree diversity experiment. A higher proportion of crown leaf area occurred in the upper crowns of species with higher specific leaf areas. Tree-level APAR depended largely on tree leaf area and also, butto a lesser extent, on relative height (i.e., tree dominance) and leaf-area index (LAI). Stand-level APAR depended on LAI and canopy volume, but not on the vertical stratification or canopy leaf-area density. The mixing effects, in terms of relative differences between mixtures and monocultures, on stand-level APAR were correlated with the mixing effects on basal area growth, indicating that light-related interactions may have been responsible for part of the mixing effects on basal area growth. While species identity influences the vertical distributions of leaf area within tree crowns, this can have a relatively small effect on tree and stand APAR compared with the size and vertical positioning of the crowns, or the LAI and canopy volume.

Fourteen years of swamp forest change from the onset, during, and after invasion of emerald ash borer

Since beginning its invasion of eastern North America by 2002, the Asian-origin beetle emerald ash borer (EAB; Agrilus planipennis) has decimated ash trees (Fraxinus spp.). In the Great Black Swamp in northwestern Ohio, USA, 90 km south of the epicenter of EAB invasion, we examined changes in forest communities during a 14-year period spanning EAB’s arrival in 2005 through 2018. No green ash (Fraxinus pennsylvanica) trees larger than 4 cm in diameter were alive on study sites in 2018, but ash saplings 1–4 cm in diameter (764 stems/ha) and seedlings (1.5% cover) were plentiful. Basal area growth of other tree species did not compensate for ash loss; total basal area averaged 8% lower in 2018 than in 2005. In the understory, non-native plants were negligible (< 2% cover, < 3 species/0.05 ha) among years and did not change significantly after EAB’s arrival. Native plant cover was twice as high in 2018 than when EAB arrived in 2005. Changes in understory cover primarily entailed reorganization of species already established when EAB arrived, rather than colonization by new species. New colonizers proportionally comprised only 0.05–0.07 of total cover among years. The shrub spicebush (Lindera benzoin) and forb Virginia creeper (Parthenocissus quinquefolia) dominated understories throughout the study. From a perspective of maintenance of native understories in EAB-aftermath forests, observed changes were probably as favorable as could be expected. Native species already present increased the most, neither floristic quality nor wetland indicator species declined, and non-native plants did not increase.

Less is more: Effects of competition reduction and facilitation on intra-annual (basal area) growth of mature European beech

KEY MESSAGE: Species-specific neighborhood identity effects such as competition reduction or facilitation can positively influence growth patterns of Fagus sylvatica at a given site, but are not strong enough to overcome fundamental growth–environment interactions of European beech. Competition and growth dynamics operating within multi-species tree stands are more complex than interactions within evenly aged monocultures. In three major geographic regions of Germany, we used electronic dendrometers to analyze the impact of neighborhood identity effects such as competition reduction or facilitation on the intra-annual stem growth patterns of Fagus sylvatica (European beech) on various time scales (day to year). Although not consistently significant, within the same study site average basal area growth relative to initial values was always higher at the ends of the growing seasons if subject tree beeches were exposed exclusively to interspecific competition. Weibull growth curves were fitted to rescaled dendrometer profiles. Analysis of the resulting Weibull scale (T) and shape (m) parameter estimates indicated the following: within the same growing area, initial growth trends of beeches in either con- or allo-specific competitive neighborhoods did not differ significantly, but subject trees exclusively surrounded by Pinus sylvestris benefited through extended duration of growth. These findings are reflected in the results for onset, cessation and total duration of wood formation calculated from inverse Weibull functions. Results of this study tend to confirm the assumption that interspecific interference induces higher daily stem growth rates of beech throughout the entire growing season. However, although particular species-specific neighborhood identity or mixing effects can indeed positively influence growth patterns of Fagus sylvatica at a given site, they are not strong enough to overcome fundamental growth–environment interactions of European beech.

Asymmetric competition, ontogenetic growth and size inequality drive the difference in productivity between two-strata and one-stratum forest stands

Size inequality has been considered a key feature of plant population structure with impacts on ecosystem functions. In forest ecosystems, studies examining the relationship between tree size inequality and stand productivity have produced mixed outcomes. These studies found positive, neutral or negative relationships and discussed how this could be influenced by competition for light between trees (e.g. light interception efficiency), but far less attention has been paid to the role played by tree ontogenetic growth. In this article, we present a simple mathematical model that predicts the basal area growth of a two-strata stand as a function of tree basal areas and asymmetric competition. Comparing the growth of this stand to the growth of a spatially homogeneous one-stratum stand and a spatially heterogeneous one-stratum stand, we show that higher growth of the two-strata stand is achieved for concave shape, increasing functions of ontogenetic growth and for low intensities of absolute size-asymmetric competition. We also demonstrate that the difference in growth between the two-strata stand and the one-stratum stands depends on tree size inequality, mean tree basal area and total basal area in the two-strata stand. We finally found that the relationships between tree size inequality and productivity can vary from positive to negative and even non-monotonous. However, we highlight that negative relationships may be more frequent. As a conclusion, our results indicate that ontogenetic growth can have a major impact on the form and the magnitude of the size inequality–productivity relationship.

Respiratory costs of producing and maintaining stem biomass in eight co-occurring tree species.

Given the importance of carbon allocation for plant performance and fitness, it is expected that competition and abiotic stress influence respiratory costs associated with stem wood biomass production and maintenance. In this study, stem respiration (R) was measured together with stem diameter increment in adult trees of eight co-occurring species in a sub-Mediterranean forest stand for 2years. We estimated growth R (Rg), maintenance R (Rm) and the growth respiration coefficient (GRC) using two gas exchange methods: (i) estimating Rg as the product of growth and GRC (then Rm as R minus Rg) and (ii) estimating Rm from temperature-dependent kinetics of basal Rm at the dormant season (then Rg as R minus Rm). In both cases, stem basal-area growth rates governed intra-annual variation in R, Rg and Rm. Maximum annual Rm occurred slightly before or after maximum Rg. The mean contribution of Rm to R during the growing season ranged from 56% to 88% across species using method 1 and from 23% to 66% using method 2. An analysis accounting for the phylogenetic distance among species indicated that more shade-tolerant, faster growing species exhibited higher Rm and Rg than less shade-tolerant, slower growing ones, suggesting a balance between carbon supply and demand mediated by growth. However, GRC was not related to species growth rate, wood density, or drought and shade tolerance across the surveyed species nor across 27 tree species for which GRC was compiled. The GRC estimates based on wood chemical analysis were lower (0.19) than those based on gas exchange methods (0.35). These results give partial support to the hypothesis that wood production and maintenance costs are related to species ecology and highlight the divergence of respiratory parameters widely used in plant models according to the methodological approach applied to derive them.

An Annual basal area growth model with multiplicative climate modifier fitted to longitudinal data for shortleaf pine

Abstract Understanding climatic influences on annual basal area growth (ABAG) rates of individual trees is necessary to predict future stand dynamics. We fitted nonlinear ABAG models for shortleaf pine (Pinus echinata Mill.) with climate variables linearly added to the arguments of logistic and exponential multiplicative functions of climate variables as climate modifiers to incorporate 14 growing seasons and 30 month-specific climate variables including standardized precipitation index. Data were collected from permanently established plots in Arkansas and Oklahoma. Six re-measurement events collected between 1985 and 2014 provided five growth periods (GPs) and ABAG models were fitted using a mixed-effects approach. Model performance was evaluated using likelihood ratio tests and fit statistics. Climate variables from GPs expressed as deviations from long-term means that performed better than other candidate variables included (1) month-specific: June mean maximum air temperature (°C) (DTMAX6), and September precipitation (mm) (DPPT9); and (2) growing seasons: mean maximum air temperature (°C) (DGTMAX) and precipitation (mm) (DGPPT). ABAG models fitted with multiplicative climate modifiers provided improved growth predictions compared with models fitted with climate variables linearly added to the argument of a logistic function. There was positive correlation with DGTMAX and negative correlation with DMPPT. In addition, 1°C increase in mean maximum temperature had a greater cumulative effect on ABAG rates of young versus old trees. Fitting ABAG models with climate modifiers are useful for assessing variations in productivity due to climate change in the future.

Basal area and diameter growth in high-graded eastern temperate mixedwood forests: the influence of acceptable growing stock, species, competition and climate

AbstractHarvesting practices in temperate mixedwoods of eastern North America have a history of diameter-limit cuts, which have often resulted in degraded residual stands. In this study, we examined the factors influencing stand basal area (BA) and tree diameter growth in previously high-graded mixedwood forests, to understand which stands are more likely to recover from high-grading. Over 15 years, we monitored tree growth, recruitment and stem quality of 532 sample plots that were located in high-graded stands of Quebec’s mixedwood forest. We found that diameter growth rates were positively correlated with precipitation-related variables for balsam fir (Abies balsamea) and for yellow birch (Betulla alleghaniensis) but opposing trends for temperature-related variables were found. Conversely to balsam fir, yellow birch growth was positively correlated to temperature variables. Our results also show that BA growth was greater for plots with a larger acceptable growing stock (AGS: trees with potential sawlog production) and that the increase in AGS was greater for plots with larger amount of conifer BA. These result highlights the importance to maintain a proportion of conifer trees in these mixed stands. Moreover, the significant effect of asymmetric competition in our study underscores the relevance of considering the spatial distribution when choosing crop trees.

Effects of potassium/sodium fertilization and throughfall exclusion on growth patterns of Eucalyptus grandis W. Hill ex Maiden during extreme drought periods

In Brazil, most Eucalyptus plantations are located in regions experiencing periods of water shortage where fertilizers are intensively used to achieve high productivity. Fertilization can affect water use. However, the effects of fertilization on tree growth patterns during extreme droughts periods remain unknown. A throughfall exclusion experiment was set up in Sao Paulo State-Brazil to study the effects of potassium (K) and sodium (Na) fertilization and their interaction with water supply in the growth of Eucalyptus grandis trees over an abnormal season of 6 months of extreme drought in comparison with that in normal seasons, as well as the differences in responsiveness to intra-annual meteorological variability. Arranged in a split-plot design, the factors were water supply (37% throughfall exclusion vs. no throughfall exclusion) and fertilization regime (K, Na, and control). Basal area growth was monitored by band dendrometers measurements at 14-day intervals over 2 years. Meteorological and soil water content data were also collected. K and Na fertilization increased the tree basal area by four and three-fold, respectively, during normal seasons. During a severe drought season, these positive effects were suppressed. However, K- and Na-fertilized trees achieved a similar cumulative basal area increment to that of the control trees. The 37% throughfall exclusion significantly decreased tree growth in all treatments only in the severe drought period, and these effects were stronger in K-fertilized trees. K-fertilized trees were highly responsive to intra-annual meteorological variability. Our results suggest that extreme drought has similar effects on E. grandis tree growth regardless of the K/Na fertilization regime.