Trees最新文献

Key message

Understanding bark allocation in juvenile stages of commercially viable Pinus trees can be useful in dating wood formation, thus improving the accuracy of correlating wood quality to environmental factors.

Abstract

Bark is an important and multifunctional part of plant anatomy that has been researched mostly in the context of fire history, timber resource assessments and more recently as a bioresource. Few studies have comprehensively examined bark thickness in some commercially valuable Pinus species. More importantly, the role of bark in accurately dating wood formation has seldom been researched. This study was conducted to model and compare bark thickness variation between different species of young South African-grown Pinus trees including Pinus radiata var. radiata D. Don., Pinus elliottii Engelm., Pinus elliottii × Pinus caribaea var. hondurensis, Pinus patula × Pinus tecunumanii (Low Elevation), and Pinus patula × Pinus tecunumanii (High Elevation). Measurements were taken at 1.6 and 2.3 years including absolute and relative bark thickness and distribution along the stem. Results showed species-specific variation in absolute and relative bark thickness with the highest means recorded in Pinus elliottii × Pinus caribaea and lowest in Pinus radiata. A positive linear relationship was observed between bark thickness and diameter, consistent with all species and ages. Absolute bark thickness decreased along the stem from bottom to top while more nuanced patterns of variation were observed for relative bark thickness. These findings underscore the importance of understanding bark thickness in young trees for various applications, including dating wood formation, anticipatory breeding strategies for quality wood and predicting stand quality among others.

Key message

Terrestrial laser scanning data of trees combined with models of heartwood content proportion of woody disks can provideprecise characterization of total aboveground tree sapwood and heartwood volume.

Abstract

Quantifying sapwood and heartwood content of trees is challenging. Previous studies have primarily characterized main stem wood composition, while branches have rarely been studied. Terrestrial Laser Scanning (TLS) can provide precise representations of the entire above-ground tree structure, non-destructively, to help estimate total tree sapwood and heartwood volume. In this study, we used TLS to scan above-ground portions of twenty-four open-grown, urban Gleditsia triacanthos trees on Michigan State University campus. TLS data were used to generate quantitative structure models that provided comprehensive characterizations of the total tree woody surface area (WSA) and volume. A subsample of trees was harvested (after scanning) and main stem and branch woody disks were collected to build models of heartwood content proportion. Models were applied to measurements from TLS to quantify complete heartwood and sapwood volume of each tree, including main stem and branches. From the base to the top of the trees, the largest portion of stem vertical cumulative volume was heartwood, whereas vertical cumulative volume of branches showed the opposite pattern. Absolute heartwood volume declined monotonically toward zero from stem base to stem top, while absolute sapwood volume declined sharply from stem base up to near the crown base and then remained relatively constant within crown. We also found that tree WSA increased with sapwood volume for both branches and main stem. This study developed a novel, general method for quantifying total aboveground sapwood and heartwood volume of trees and provided new insights into urban tree growth and structure.

Key message

The effects of MJ on pine trees are species-specific and trigger a resistant phenotype to the PWN. A more dynamic response of hormones and gene expression in Pinus pinea explains the high resistance to Bursaphelenchus xylophilus of this species.

Abstract

Knowledge on hormonal and genetic mechanisms of pine trees in response to the pinewood nematode (PWN; Bursaphelenchus xylophilus) is limited. To describe tree defence strategies against B. xylophilus, this study used the plant stress hormone methyl jasmonate (MJ) on four pine species with different susceptibility (Pinus pinaster < P. radiata ≈ P. sylvestris < P. pinea). Three-year-old trees were sprayed with MJ at 0, 25, and 50 mM, and 2 months later challenged with the PWN. Multiple samples were taken to assess nematode content, oxidative stress, secondary metabolites, phytohormone levels, and stress-related gene expression. Nematode infestation in trees correlated negatively with the water content of needles and phenolics of stems, and positively with the concentration of indole-3-carboxylic acid in stems. MJ spray reduced in a dose-dependent manner the nematode content in P. pinaster and P. sylvestris. The effects of MJ were species-specific, although a more pronounced impact was observed in the susceptible P. pinaster species, leading to a decrease of chlorophyll and water loss and to the upregulation of the gene involved in the biosynthesis of terpenoids (AFS). After MJ spray, increased levels of JA-Ile were observed in P. pinea only. Hormone profiling, predisposition to activate antioxidant response, and gene expression in P. pinea trees provide evidence of why this species is highly resistant to B. xylophilus. On the contrary, the lack of effective hormonal changes in P. pinaster explained the lack of defence responses to B. xylophilus of this susceptible species. This study is a first approach to explore biochemical, molecular, and hormonal interactions between Pinus species and the PWN, and presents unprecedented insights into alterations induced by exogenous MJ in regulating defence mechanisms in pine trees.

Key message

The temperature sensitivity of maximum latewood density measurements in pine trees from a high-elevation site in the Spanish Pyrenees increases with tree age. Detrending modulates the intensity of the effect.

Abstract

Tree-rings are the prime archive for high-resolution climate information over the past two millennia. However, the accuracy of annually resolved reconstructions from tree-rings can be constrained by what is known as climate signal age effects (CSAE), encompassing changes in the sensitivity of tree growth to climate over their lifespans. Here, we evaluate CSAE in Pinus uncinata from an upper tree line site in the Spanish central Pyrenees, Lake Gerber, which became a key location for reconstructing western Mediterranean summer temperatures at annual resolution. We use tree-ring width (TRW) and maximum latewood density (MXD) measurements from 50 pine trees with individual ages ranging from 7 to 406 years. For MXD, temperature sensitivity increases significantly (p < 0.01) with tree age from r = 0.31 in juvenile rings with a cambial age < 100 years to r = 0.49 in adult rings > 100 years. Similar CSAE are not detected in TRW, likely affected by the overall lower temperature signal (r_TRW = 0.45 vs. r_MXD = 0.81 from 1951 to 2020). The severity of CSAE is influenced by the approach used to remove ontogenetic trends, highlighting the need to assess and consider potential biases during tree-ring standardization. Our findings reveal CSAE to add uncertainty in MXD-based climate reconstructions in the Mediterranean. We recommend studying CSAE by sampling diverse age classes in dendroclimatic field campaigns.

Key message

Resin production and growth in Pinus pinaster and Pinus pinea show a trade-off under varying environmental conditions, impacting future resin yields under climate change.

Abstract

Resin production in pines constitutes an important defense mechanism against biotic and abiotic factors, and it is also an important forestry product. In Portugal, resin is mainly extracted from Pinus pinaster and to a lesser extent from Pinus pinea, the two most widespread pine species in the country. The resin tapping season coincides with the growing season, from spring to autumn. Thus, growth and resin production may compete for carbon, although their response to environmental conditions can differ. This study investigates how the daily growth and biweekly resin production of P. pinaster and P. pinea in a mixed stand respond to environment over the 2021 growing season. During the resin tapping period, growth of both species showed a positive correlation with temperature, soil moisture, air relative humidity and radiation. Resin yield of both species showed a positive relation with soil temperature, and a negative relation with growth, suggesting a trade-off between growth and resin yield. Our results indicate that both growth and resin yield increase with temperature, with growth being more sensitive to soil moisture and relative humidity. Under a scenario of rising temperatures and precipitation reduction, both functions (growth and resin yield) are expected to be affected positively. However, resin production depends on carbon assimilation and allocation, both of which are reduced or altered during periods of extreme drought. This can lead to increasing competition for carbon allocation between growth, storage and resin yield, making resin yield responses to climate change scenarios uncertain.

Forest restoration is one of the key approaches employed to reverse environmental degradation, although there is no consensus regarding the best model to be applied for this purpose. It has been hypothesized that overall bacterial density and the diversity of bacterial antagonists in replanted areas are modulated by the reforestation model employed. To test this hypothesis, we have compared the bacterial density in soil samples from ten different replanted forest areas and from a native forest for two consecutive years, evaluated the antagonist activities of bacterial isolates from these areas against Fusarium oxysporum and Rhizoctonia solani, and identified the bacterial antagonists by 16S rRNA gene sequencing. All timber and non-timber species employed in the reforestation models were native to the Amazon biome, with the exception of eucalyptus, and additional cover plants were employed in three of the areas. No significant differences were found in bacterial densities between replanted forest areas in either of the years, but significant between-year differences were detected in five of the plots. Twenty of the 220 bacterial isolates tested showed antagonistic activity and of these three were classified within the phylum Proteobacteria and 17 were classified as Firmicutes and belonged to the genera Bacillus, Brevibacillus, Burkholderia, Paenibacillus and Variovorax. The largest microbial diversities were found in soil samples from plots that had undergone natural reforestation or had been reforested by broadcasting or mechanical sowing of a mixture of seeds from timber and non-timber species along with leguminous cover plants.

Key message

The Montgomery equation, which assumes a proportional relationship between the tepal area and the product of the tepal length and width, is validated using data drawn from four Magnolia species.

Abstract

An important metric of floral non-reproductive size is individual petal or tepal area (A). The Montgomery equation (ME) estimates A by assuming a proportional relationship between A and the product of petal or tepal length (L) and width (W), i.e., (A propto LW), whereas the power-law equation (PLE) assumes the allometric relationship (A propto left( {LW} right)^{{{upalpha }_{1} ne 1}}). If W/L has a small variation, four relationships are expected to hold true, i.e., (A propto L^{2}), (A propto L^{{{upalpha }_{2} }}), (A propto W^{2}), and (A propto W^{{{upalpha }_{3} }}), where α₁, α₂, and α₃ are scaling exponents to be estimated. To assess the validity of these six formulae, 2031 the petal-like tepals of 250 flowers from four Magnolia species were measured. The root-mean-square error (RMSE) was used to determine the goodness of fit of each equation, and the percentage error (PE) was used to compare any two equations with the same predicator, i.e., LW, L and W. The ME was validated for calculating A at the species level and for the pooled data given that three of the four species had < 0.05 RMSEs and one had a < 0.07 RMSE. However, the PLE was more robust than the ME at the species level. For the pooled data, the ME and PLE had a negligible difference in RMSE values. These results show that the ME is a valid and non-destructive tool for measuring A for the Magnolia species examined in this study and likely holds true across other more diverse species.

Phoebe bournei (Hemsl.) Yang, a valuable timber species, grows slowly in the seedling stage. In this experiment, the effects of the combined application of nitrogen and phosphorus on the biomass and nutrient status of P. bournei container seedlings were investigated. Using the exponential fertilization method, eight fertilization levels (CK, N1, N2, N3, P, N1P, N2P, and N3P) were set up for P. bournei one-year container seedlings. Following fertilization, the biomass and nutrient element contents of each organ of the seedlings were determined. The biomass, mass fractions of nitrogen, phosphorus, and potassium, as well as their accumulation and absorption in the organs of seedlings, were higher under various fertilization treatments than under CK. Additionally, when nitrogen and phosphorus were applied together, the organs of seedlings absorbed the most quantity of nitrogen, phosphorus, and potassium. The accumulation and distribution ratio of nitrogen, phosphorus, and potassium in the aboveground part of seedlings was higher than in the underground part. Furthermore, for nitrogen and potassium, fertilization treatments increased the distribution ratio in the underground part. All fertilizer treatments, except for the single P treatment, resulted in a decrease in the phosphorus allocation ratio in the underground part. Overall, fertilizer application can increase the nutrient element content of seedlings. The nutrient status of seedlings under the N2P treatment was better than other treatments, indicating that, with a synergistic effect of nitrogen and phosphorus, the N2P treatment could effectively promote the growth of P. bournei container seedlings.

Juniperus excelsa M. Bieb. (Cupressaceae) is the most common species among the six juniper species in Iran. Unfortunately, in recent years, due to anthropogenic disturbances, low natural reproduction, and excessive drought, the population of this valuable endangered species has decreased significantly. In a case study conducted in Parvar Protected Area in Semnan province, the decline was associated with strip-cankers on the trunk, detached bark, discolorations and browning of the plant, resulting in its complete dryness. After isolating the fungus associated with declined trees, macro- and micro-morphological characteristics showed that the obtained isolate belonged to Biscogniauxia mediterranea (De Not.) Kuntze. Then, evaluation of rDNA ITS region sequence information confirmed it. The pathogenicity test was performed in the greenhouse conditions and its pathogenicity was confirmed on juniper plants. This is the first report of B. mediterranea causing disease on J. excelsa as a new host, from Iran and worldwide. This study confirms the current spread of B. mediterranea to different regions and hosts in Iran, as reported in other parts of the world, most likely due to ongoing climate change that create optimal conditions for the survival of the fungus in other areas, that were previously unsuitable for it.

Key message

Exposure to water shortage causes acclimation to drought in 40-year-old Norway spruce.

Abstract

Growth and health of trees that are drought-naïve may be more affected by water shortage, which could increase the risk of mortality. This study evaluates whether drought conditioning can improve resilience to subsequent drought, where resilience is the ability to regain pre-drought levels of basal area growth. It also explores the xylem structure underlying the responses. Tree-ring samples were collected from Norway spruce trees subjected to throughfall exclusion in southern Sweden, which subsequently experienced a severe natural drought event. We compare growth and xylem structure in three treatments from a randomized complete block design: drought-conditioned trees with a 2-year artificial drought treatment and 2 years of recovery prior to the natural drought; a prolonged artificial drought that exaggerated the natural drought; and a control. Trees in the conditioned with recovery treatment were significantly more resilient than trees in the control and in the prolonged drought without recovery treatment. While not significant, drought-conditioned trees were trending toward xylem with thicker cell walls, and wider cell lumen. At the same time, the fortification of the xylem did not seem to impair long-term growth performance. These findings suggest that drought conditioning, after a period of recovery, can improve tree responses to subsequent droughts.