Taeda Plantations Research Articles

Determining the Pulping Conditions and Properties of Unbleached Pulp from Uruguayan Pinus Taeda

Context: In Uruguay, numerous Pinus taeda plantations are at final-turn age, but they still do not have commercial destination and are exported as green-wood logs. For the development of this sector, it is necessary to strive towards a comprehensive processing of this resource. Method: This work focused on analyzing the use of Pinus taeda wood available in the country to produce brown kraft pulp with a kappa number of 80, which can be used to make packaging paper. As raw materials, we employed by-products from the mechanical wood-transformation industry (wood chips and thinning wood) and final-turn wood. Pulping tests were carried out, varying the alkali charge and the H-factor while aiming for a kappa number of 80. The viscosity, pulping, and rejection yield were measured in the pulps, and the pH and residual alkali content were evaluated in black liquor. Results: Based on the results, the best pulping conditions were an active alkali charge of 14% (Na2O) and an H-factor of 1260 for sawmill chips and thinning wood, as well as an active alkali charge of 14% (Na2O) and an H-factor of 1080 for final-turn wood. The pulp obtained with sawmill chips exhibited the most resistant fibers, and the final-turn wood pulp was the most sensitive to the refining process. Under the aforementioned conditions, the paper properties of laboratory-produced pulp are comparable with those of commercial pulp. Conclusions: This indicates that it is technologically possible to produce brown kraft pulp from Uruguayan Pinus taeda wood, with adequate quality to produce packaging paper

Fungal biomass and ectomycorrhizal community assessment of phosphorus responsive Pinus taeda plantations.

Ectomycorrhizal fungi and non-ectomycorrhizal fungi are responsive to changes in environmental and nutrient availabilities. Although many species of ectomycorrhizas are known to enhance the uptake of phosphorus and other nutrients for Pinus taeda, it is not understood how to optimize these communities to have tangible effects on plantation silviculture and P use efficiency. The first step of this process is the identification of native fungi present in the system that are associated with P. taeda and influence P uptake efficiency. We used sand-filled mesh bags baited with finely ground apatite to sample ectomycorrhizal and non-ectomycorrhizal fungi associated with the rhizosphere of P-responsive P. taeda under several field conditions. Mesh bags were assessed for biomass accumulation over three years using a single three-month burial period pre-harvest and three six-month burial periods post-planting. Amplicon sequencing assessed ectomycorrhizal and non-ectomycorrhizal communities between phosphorus treatments, sites, mesh bags, and the rhizosphere of actively growing P. taeda in the field. We found biomass accumulation within the mesh bags was inversely related to increasing phosphorus fertilization (carryover) rates from pre-harvest to post-planting. Up to 25% increases in total biomass within the bags were observed for bags baited with P. Taxonomic richness was highest in Alfisol soils treated with phosphorus from the previous rotation and lowest in the Spodosol regardless of phosphorus treatment.

Production patterns of loblolly pine plantations along a geographic gradient in southern Brazil

Pinus taeda plantations depend directly on the supply of resources (light, water, and nutrients) available to the stand. However, studies quantifying edaphic and climatic factors in P. taeda stands are scarce. This study aimed to identify the main edaphic, climatic and stand factors that influence the productivity and growth pattern of P. taeda plantations in southern Brazil. A total of 24 stands, ranging between 8 and 10 years old were evaluated. Biometric variables such as height, diameter at breast height (DBH), stem analysis, growth rings, specific gravity, and soil chemical and physical variables were evaluated. Site index (SI), stem biomass, mean annual increment without bark (MAI) and correlations between variables were calculated. We observed that by nine years after planting, none of the plots had reached their maximum growth; and MAI, standing stem biomass and SI ranged from 15 to 35 m³ ha−1 year−1, 56–131 Mg ha−1, and 12–19 m, respectively, with higher values in Três Barras site. Stem biomass were positively related with SI (r = 0.89), and stem production was related with higher available water content (r = 0.41), warm temperatures (r = 0.61), and higher relative air humidity (r = 0.58). The study corroborates the role of nutrients, well-drained soils, mild climatic conditions, and low water deficit to explain the high yields of P. taeda in Brazil compared to other locations around the world. Based on these results, studies on fertilization, genetic material, and more frequent use of stem analysis, associated with X-ray densitometry, are recommended for P. taeda.

Colonization of root endophytic fungus Serendipita indica improves drought tolerance of Pinus taeda seedlings by regulating metabolome and proteome.

Pinus taeda is an important forest tree species for plantations because of its rapid growth and high yield of oleoresins. Although P. taeda plantations distribute in warm and wet southern China, drought, sometime serious and long time, often occurs in the region. To explore drought tolerance of P. taeda and usage of beneficial microorganisms, P. taeda seedlings were planted in pots and were inoculated with root endophytic fungus Serendipita indica and finally were treated with drought stress for 53 d. Metabolome and proteome of their needles were analyzed. The results showed that S. indica inoculation of P. taeda seedlings under drought stress caused great changes in levels of some metabolites in their needles, especially some flavonoids and organic acids. Among them, the levels of eriocitrin, trans-aconitic acid, vitamin C, uric acid, alpha-ketoglutaric acid, vitamin A, stachydrine, coumalic acid, itaconic acid, calceolarioside B, 2-oxoglutaric acid, and citric acid were upregulated more than three times in inoculated seedlings under drought stress, compared to those of non-inoculated seedlings under drought stress. KEGG analysis showed that some pathways were enriched in inoculated seedlings under drought stress, such as flavonoid biosynthesis, ascorbate and aldarate metabolism, C5-branched dibasic acid metabolism. Proteome analysis revealed some specific differential proteins. Two proteins, namely, H9X056 and H9VDW5, only appeared in the needles of inoculated seedlings under drought stress. The protein H9VNE7 was upregulated more than 11.0 times as that of non-inoculated seedlings under drought stress. In addition, S. indica inoculation increased enrichment of water deficient-inducible proteins (such as LP3-1, LP3-2, LP3-3, and dehydrins) and those involved in ribosomal structures (such as A0A385JF23). Meanwhile, under drought stress, the inoculation caused great changes in biosynthesis and metabolism pathways, mainly including phenylpropanoid biosynthesis, cutin, suberine and wax biosynthesis, and 2-oxocarboxylic acid metabolism. In addition, there were positive relationships between accumulation of some metabolites and enrichment of proteins in P. taeda under drought stress. Altogether, our results showed great changes in metabolome and proteome in inoculated seedlings under drought stress and provided a guideline to further study functions of metabolites and proteins, especially those related to drought stress.

Relationship between microbiological, physical, and chemical attributes of different soil types under Pinus taeda plantations in southern Brazil

Relationship between microbiological, physical, and chemical attributes of different soil types under Pinus taeda plantations in southern Brazil

Using microdialysis to assess soil diffusive P and translocated sap flow P concentrations in Southern Pinus taeda plantations

Using microdialysis to assess soil diffusive P and translocated sap flow P concentrations in Southern Pinus taeda plantations

Impact of phosphorus omission fertilizer on growth, nutritional status, biochemical and physiological parameters in a Pinus taeda L. plantation

Low availability of phosphorus (P) in the soil is one of the factors limiting the productivity of Pinus taeda plantations. Phosphate fertilizer application in Pinus shows divergence in growth responses. Thus, understanding the response of plant photosynthetic efficiency and growth in relation to phosphate fertilizer application can serve as a basis to guide management practices in Pinus taeda plantations. The study aimed to evaluate the impact of P omission fertilizer on growth parameters, nutritional, biochemical, and physiological status of a Pinus taeda L. plantation. The experiment was conducted on a Pinus taeda plantation subjected to P fertilization: Control - without addition of N, P and K; P–fertilized - with addition of N, P and K; and P–omission - addition of N and K, and P omission fertilizer. The parameters height, stem and canopy diameter and productivity factor, P concentration in needles, soil available P, electron transport rate (ETRm), maximum quantum yield of PSII (Fv/Fm), initial (Fo) and maximum (Fm) fluorescence, chlorophyll a, b and total, carotenoids, superoxide dismutase (SOD) and peroxidase (POD), hydrogen peroxide (H2O2), lipid peroxidation (TBARS), and acid phosphatase activity, were evaluated. P fertilized application increased soil available P, providing largest P uptake by roots and P concentration in needles. The increase in available soil P contributed to elevate photosynthetic parameters, such as ETRm, Fv/Fm, chlorophyll a, b and total, and carotenoids. These factors contributed to increase C assimilation, height, stem and canopy diameter and productivity factor parameters. On the other hand, the P–omission and control conditioned the growth of Pinus taeda under stress, elevating the values of Fo, Fm, SOD and POD, which reduced plant development.

Soil Depth Can Modify the Contribution of Root System Architecture to the Root Decomposition Rate

Aims: Changes in root system architecture (RSA) and soil depth affect the root decomposition rate. However, due to soil opacity, many variables of RSA have not been well studied or even measured. Methods: To investigate the effects of soil depth and the characteristics of RSA on the root decomposition rate, soil samples (Soil cores were collected in October 2020 from Cunninghamia lanceolata and Pinus taeda plantations, which were 40 years old) were obtained using a soil auger and had a diameter of 10 cm and a length of 60 cm. Samples were taken from six different soil depths, ranging from 0 to 60 cm with a 10 cm interval between each depth. The RSA in the in-situ soil cores was analyzed using computed tomography scans and Avizo. Results: Root volume and the number of root throats were significantly higher at the 0–10 cm soil depth than at the 10–60 cm soil depth, but root length was significantly lower at the 50–60 cm soil depth (p < 0.05). Structural equation modeling showed that different stand types influenced root biomass and thus the root decomposition rate directly or indirectly through the characteristics of the stand types. RSA, i.e., root thickness and breadth, affected root biomass indirectly and then affected the root decomposition rate. Root biomass contributed the most to the root decomposition rate in the Cunninghamia lanceolata (20.19%) and Pinus taeda (32.26%) plantations. The contribution of the RSA variables to the root decomposition rate exceeded 50% at the 20–30 cm and 40–50 cm soil depths. Conclusions: Our findings suggested that the influence of the RSA variables on the root decomposition rate varies with soil depth. This deserves more consideration in our future studies on root decomposition and RSA.

Can fertilization and stand uniformity affect the growth and biomass production in a Pinus taeda plantation in southern Brazil

Silvicultural activities employed during stand development are used to manage the distribution of site resources (light, water and nutrients) to the trees within the stand. Because heterogeneity within forest plantations has been shown to increase the number of dominated trees and decrease stand productivity, the establishment of efficient and productive plantations should presumably include nutrient regimes which ensure readily available nutrients and tree-to-tree homogeneity. The study aimed to evaluate how fertilization and uniformity can affect growth and biomass production in a Pinus taeda plantation in southern Brazil. Clones of loblolly pine (Pinus taeda L; Arborgen GE34) were subjected to two factors: (i) uniformity (U) or heterogeneity (H) of planting; and (ii) fertilization (F) or no fertilization (W) to the plants. Trees were evaluated up to 11.2 years of age. Individual survival (%), diameter at breast height (DBH), total height (H), dominant height (Hdom), basal area (G), stem volume (Vol), mean annual increment (MAI), leaf area index (LAI), uniformity index (PV50), needles, branches, bark, trunk, thick roots, and total biomass were measured. Trees grown under uniform and fertilized conditions showed the highest values of the variable’s uniformity index (PV50 index); growth (height, DBH, and LAI), productivity(MAI and stem volume), and biomass (stembark, stemwood, branches, coarse roots, and total) compared to trees grown under heterogeneous and unfertilized conditions. Our results show that the productivity of fast growing, genetically identical trees can be improved with silvicultural activities which promote uniformity and improve nutrient availability.

Legacy effects after seven years of afforestation withPinus taedain a natural grassland

The replacement of grassy vegetation by tree monocultures has become an emerging global activity. In South America, about half a million hectares of new plantations are incorporated each year, typically conducted with fast‐growing exotic species, likePinusandEucalyptusspecies. However, information about the potential for spontaneous recovery of these grasslands is almost nonexistent. We assessed the biotic and abiotic legacies left by a 7‐year plantation ofPinus taedaon a natural temperate sub‐humid grassland of Uruguay. In a paired sampling design, comparing a clear‐cutP. taedaplantation and a natural grassland, we analyzed the vegetation richness, cover and composition, the seed bank size and composition, and chemical soil parameters. Afforestation reduced species richness and vegetation cover by 30 and 58%, respectively. Also, species composition differed considerably between sites. Afforestation had a strong negative effect on grass species, excluding the shade‐intolerant C4grasses that dominate in the grassland. Seed‐bank richness did not differ between sites, but the total seedling density was significantly higher in the plantation compared to the grassland (6,620 and 4,420 seeds/m2, respectively), mainly due to the contribution of forbs. Only 30% of the seed bank species were shared between the two sites. In terms of soil chemical parameters, afforestation induced soil acidification (deviation by 0.15–0.20 pH units) and reduction in soil carbon and cation (Ca and K) concentrations (deviation by 30, 20, and 40%, respectively). Our study showed limited possibilities for passive restoration of a natural grassland of Uruguay after aPinusafforestation event.

Litterfall and Accumulated Nutrients in Pinus taeda Plantation and Native Forest in Southern Brazil

The dynamics of the production, chemical composition, and accumulated nutrients in litterfall are essential to understand the availability of nutrients and, consequently, possible gains in productivity in different forest types. Thus, the objective of the present study was to evaluate the litterfall and the accumulated nutrients in litterfall in a Pinus taeda plantation and native forest from southern Brazil. Two forest types: (i) an eight-year-old Pinus taeda L. plantation; and (ii) a native forest fragment, located in southern Brazil, were studied for four years. The monthly and annual litterfall production, chemical composition, accumulated nutrients, and nutrient use efficiency of the litterfall were evaluated. The Pinus taeda plantation showed higher values of leaves/needles litterfall and N, P, K, Ca and Mg use efficiency. This demonstrates that Pinus taeda plantations have a high production of needle biomass, which, in turn, has increased cell division, favoring the entry of these nutrients into the soil via decomposition. Our results show that total litterfall production did not significantly influence the accumulated nutrient and nutrient efficiency of litterfall, demonstrating that evaluating litterfall fractionation, such as leaves/needles, twigs and miscellaneous, is essential to understand the quantity and quality of litterfall and, thus, the nutrient cycling, which can contribute to possible silvicultural practices to be implemented, which can provide growth gains in forest types.

Do selective logging and pine plantations in humid subtropical forests affect aboveground primary productivity as well as carbon and nutrients transfer to soil?

Land use changes due to forestry activities can alter forest carbon (C) sequestration capacity by modifying vegetation structure and ecosystem functioning. The main objective of this study was to analyze aboveground net primary productivity (aNPP), through stem growth and litterfall production, and their feedback on soil C and nutrient contents, within a humid subtropical region. Two main forestry activities in NE Argentina were studied: selectively logged forests and Pinus taeda (loblolly pine) plantations for wood production. Well-preserved native forests were used as a control to compare the effects of interventions on the original subtropical forests. Despite differences in tree density and aboveground biomass among forests and pine plantation stands, the aNPP and total annual litterfall were similar across all ecosystems. However, litterfall quality and soil N content were substantially lower in pine plantations compared to both native forests. The labile soil C fractions were higher in pine plantations than native forests while no differences were observed in recalcitrant humic fractions across ecosystems. Overall, the results of this study suggest that man-made intervention in the structure of forest ecosystems does not necessarily result in degradation of aboveground ecosystem processes but had an impact on belowground processes and stocks in pine plantations, which has important implications for forest management.

ASSORTMENT DOWNGRADE CORRECTION FOR CLEAR CUT OF Pinus taeda L. WITH USE OF TRANSITION MATRIX

It is very important that the quantification of a forest's stock is determined efficiently and accurately, in such a way that more detailed information is desirable for the knowledge of the different multiproducts originated. However, the use of taper functions, a precise adjustment method for determining the assortments, does not foresee the appearance of defects in the stem that could disqualify the logs during the forest harvest. This study aimed to use the transition matrix method, a model traditionally used for predict the diametric structure of uneven-aged forests, to correct assortment estimates made by tapering functions, such as failures in tree processing, that provide a disqualification of the logs in the market values. Adapting the concept of the Markov Chain, for the correction of the assortment downgrade, the transition of the assortment classes can be obtained by dividing the actual volume obtained after the operation of the harvesting machine by the volume estimated by the tapering function. In this case, applying this alternative to the clear cut of a 16-year-old Pinus taeda plantation, it was possible to verify the existence of changes, mainly in assortment classes with a thin end diameter of 24 and 18 cm and presenting efficient correction in the estimates. In order to make realistic corrections to the assortment transition, probability matrices must be built for each compartment or forest site to be estimated. Divergences between processing machines or forestry operator’s qualifications can be decisive for the calibration of the model.

Mid-rotation fertilization and liming of Pinus taeda: growth, litter, fine root mass, and elemental composition

Forest floor litter can influence biogeochemical cycling and root growth in Pinus taeda systems, especially on low soil fertility sites. The impact of fertilization and liming on forest floor litter (quantity, elemental composition and root presence) was evaluated in a Pinus taeda stand in southern Brazil. A nutrient omission experiment was initiated in November 2008 on an 11 year-old Pinus taeda plantation. The experiment was a randomized block design with seven treatments and four blocks. The treatments were: complete (macro + micro + lime); minus macronutrients; minus micronutrients; minus K; minus Zn; minus lime; and control. In 2012, forest floor litter samples were collected, divided by layer (new litter, old litter, coarse fragmented forest layer > 2mm, fine fragment forest floor < 2mm, and fine roots) and analyzed for concentrations of Na, Al, and total nutrients. Results indicated that lime increased Ca and Mg concentrations, reduced Al toxicity, and improved fine root growth. An increase in fine roots was observed in treatments without K. There were large increases in Fe and Al as a function of litter age and increased Mn in fragmented litter when lime was applied. There was little variation in forest floor litter accumulation in all treatments. Elemental abundance was C>N>Fe>P>Ca>K>Mg>Mn under control conditions and C>N>Ca>Mg>P>Fe>Mn>K for the complete treatment. Occurrence of needle chlorosis, similar to that reported for Mg, and low growth under lime omission indicate that Mg was a major factor limiting growth. Fertilization and liming affected the bio-cycling of nutrients, Al toxicity, and root growth.

Leptographium terebrantis inoculation and associated crown symptoms and tree mortality in Pinus taeda

Leptographium terebrantis has been implicated as a contributing factor of P. taeda decline and mortality over the past several decades. We examined the potential of L. terebrantis to cause decline symptoms and determined the relationship between pathogen spread and the formation of new sapwood. The study was undertaken in a 13-y-old P. taeda plantation using artificial inoculations of fungal-colonized, sterilized toothpicks. We found that L. terebrantis was not only re-isolated from dying inoculated trees but caused decline symptomology and mortality at a high inoculum density. It was found that 20% mortality and severe growth loss among surviving trees occurred with L. terebrantis infection at the high density. At lower inoculum densities, trees produced a complete ring of new sapwood that appeared to sustain tree physiology. This suggests that management practices in P. taeda plantations which minimize bark beetle infestation and pathogen inoculum densities allow adequate sapwood function for sustained growth. • Leptographium terebrantis causes P. taeda tree mortality at high inoculum density. • Some P. taeda trees, however, tolerate the fungus at high inoculum density. • At lower inoculum densities, P. taeda completely tolerates L. terebrantis infection. • Tolerant trees form a continuous or partial sapwood without the fungal infection.

Potential damage by Acromyrmex ant species in pine plantations in southern Brazil

Abstract Acromyrmex species primarily attack Pinus taeda plantations during the first months after planting, with more intense damage in the first 30 days. We evaluated potential damage by Acromyrmex crassispinus and Acromyrmex subterraneus in 30‐day‐old P. taeda plantations in southern Brazil by assessing the number of attacked plants and the distance reached by each colony, along with the losses in plant development resulting from different levels of defoliation. Both species were significant pests in newly established pine plantations. A single colony can attack a substantial number of seedlings (up to 453 seedlings). Colonies with larger nests attacked more plants and ranged farther; A. crassispinus reached 59 m and A. subterraneus 87 m. After 10 years, no significant losses in plant development were seen in seedlings defoliated less than 50% at 30 days after planting. But when defoliation of the young plants attained 75%, 100%, and 100%, including the cut of the apical meristem, volume losses reached 32%, 37%, and 43%, respectively. Leaf‐cutting ant controls should be carried out in plantations of P. taeda within 30 days of planting to avoid attacks. When seedlings are defoliated more than 75%, they should be replanted to avoid future losses in final wood volume.

Carbon stock densities of semi-deciduous Atlantic forest and pine plantations in Argentina

Recent studies have shown the importance of subtropical forests as terrestrial carbon sinks and also their vulnerability to human disturbances and climate change. The Semi-deciduous Atlantic Forest presents large extensions replaced by productive uses, such as tree plantations, and forest remnants showing high levels of structural heterogeneity. No studies have performed carbon stock densities estimations in different pools in the region. We wonder how changes in forest structure and forest replacement by pine plantations affect ecosystem carbon stock densities in different pools and fluxes. We performed carbon estimates based on field data and compared closed (CF) and open (OF) canopy natural forest patches and Pinus taeda plantations at harvest age (PP). Structural changes in the natural forest had a profound effect on the ecosystem by halving the forest carbon stock while pulp-intended pine plantations reached the carbon stock of closed forest at harvest age. Main changes from CF to OF were a 55% decrease in the carbon of biomass and a 42% decrease in SOC. Instead, carbon stock density in biomass of PP was similar to CF but the carbon in fallen deadwood was 78% lower while in the litter layer was double; the SOC at 0–5 cm depth was 31% lower in PP than CF. Our study shows that structural changes in the natural forest halve the forest carbon stock while pulp-intended pine plantations can reach the closed forest carbon stock at harvest age. However, PP do not seem to be effective for carbon storage in the long term because of regular harvesting and clearing and their short-life products. Therefore, to effectively store the forest carbon, arresting deforestation, replacement and degradation of the original forest is crucial.

Mid-rotation response of Pinus taeda to early silvicultural treatments in subtropical Argentina

Pinus taeda plantations in subtropical areas of South America are extremely productive and commonly established on well-drained red clay sites. In the past, land with more poorly-drained soil was avoided due to concern over the factors limiting site productivity. Establishment of intensively managed plantations on poorly-drained soils usually includes soil preparation by subsoiling and/or bedding, weed control, and fertilization. However, forest managers lack information about the efficacy of early silvicultural practices to ameliorate environmental limitations and if these intensive practices generate long-term improvements in productivity in this area. Consequently, we established studies in northeastern Argentina on two sites differing by drainage class and soil texture as a full factorial design with site preparation (S; disking and disking + subsoiling (red clay) or bedding (wet loam)), fertilization (F; none or 78 kg ha−1 elemental phosphorus at planting), and weed control (W; none or two-year banded). Seven years after planting, the red clay and wet loam sites were equally productive, with maximum treatment means of 218 m3 ha−1 and 264 m3 ha−1 respectively. At the red clay site, only weed control significantly increased volume. At the wet loam site, both weed control and site preparation significantly increased volume, mainly due to increased survival. The combination of weed control and bedding yielded a non-additive volume response as indicated by a significant W*S interaction. Our results do not support the common practice of subsoiling on red clay soils. In addition, fertilization with P alone appears counterproductive or unneeded at both sites.

Nutrient Export with Logs, and Release from Residues, after Harvest of a &amp;lt;i&amp;gt;Pinus taeda&amp;lt;/i&amp;gt; Plantation in Uruguay

In Uruguay, Pinus taeda is usually planted a few months after harvest of the former turn, therefore; decomposing residues represents a nutrient source for the new plantation. The aim of this study was to determine the biomass and nutrient extraction off site, following the harvest of a P. taeda plantation. Residue decomposition patterns, and nutrient release were also examined. The site will be referred as S1, corresponding to the clear cut of a 22-year-old P. taeda plantation. Before the clear cut 10 trees were harvested, and logs, branches, twigs, and needles separately weighed. Additionally, forest litter at harvest time was quantified in three different areas. To assess decomposition, mesh bags with residues were allocated in three areas over the forest litter, and samples were taken periodically for 26 months. The remaining biomass, N, P K, Ca, and Mg contents were determined in the different fractions, calculating decompositon rates. Most of the harvested biomass was removed in logs, but the proportion of nutrients exported was considerably lower. Needles showed the highest biomass loss and only 39.1% remained after 26 months, while branches presented high rates in the first two months after cut, but slower thereafter, and at the end of the study more than two thirds of the woody residues remained. Potassium was rapidly released from the residues, while Ca, and Mg, were slowly released, and there was evidence of N and P immobilization in the early stages of decomposition. It was concluded that, although a lower proportion of nutrients were exported, compared to biomass, in the long term, nutrient export with logs could be significant for the sustainability of this production system. While K release from residues did not depend on biomass decay, the slow decomposition, and release of the other nutrients, indicates that this process could have been delayed by nutrient scarcity.

Meteorological effects on 30-years-grown Pinus taeda under a gradient of crown thinning intensities in southern Brazil

Pinus taeda plantations are an important economic activity in southern Brazil, where edaphoclimatic conditions are optimal. Understanding how meteorological conditions influence tree growth is important in such a favorable environment for reaching high growth rates and for predicting tree growth responses to climate change. The study was designed to evaluate the influence of meteorological variables on 30 years of radial growth of P. taeda trees subjected to different crown thinning intensities in southern Brazil. In total, 9280 measurements of ring width and age were evaluated. Residual chronologies were obtained according to standard dendrochronology techniques. Correlation was calculated between chronologies and meteorological variables, and thus the direction and magnitude of the relationship between meteorology and growth was addressed. Results indicated that, accounting for the whole year, meteorological conditions show no particular influence on the radial growth of Pinus taeda trees in the studied region. The exception was the vapor pressure deficit, with a significant and negative correlation with the radial growth of trees at all thinning intensities. When considering seasons, several consistent correlations were detected. Rainfall during winter, previously or at the end of the growing season, was positively correlated with the radial growth of trees at all thinning intensities. A consistent negative correlation between minimum and maximum temperature during winter and the radial growth of trees shows that P. taeda in southern Brazil, regardless of thinning intensity, benefit from colder winters in general and, particularly, from colder days during winter. Although temperature increases in the highlands of southern Brazil, as a result of global warming, may not render the cultivation of P. taeda unfeasible, they may restrict or shift the region of optimum growth as well as require changes in the genetic material. Results also suggest that high-intensity thinning may increase the influence of temperature on growth pattern of the stands.