Search Results (42)

The potential for species distribution shifts in response to changing climate and altered fire regimes is a pressing concern across ecosystems. Species responses to climate and disturbance are expressed demographically as changes in survivorship and recruitment across gradients. We examined tree recruitment and radial growth response to climate along a biophysical gradient in a mixed-conifer forest in northern New Mexico, USA, in a watershed spanning from near the lower to upper elevation range for ponderosa pine (Pinus ponderosa var. scopulorum Engelm.) and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). We compared growth responses with climate variables and stand demographic patterns of the six major tree species present, to track shifts in species community composition and dominance. We found significant changes in species composition between mature trees and seedlings and saplings across Elevation–Aspect groups in several species, indicating incipient community change. Drought stress drove patterns of tree growth and species composition shifts at low elevations, while at higher elevations increased stand density following fire exclusion led to success of shade-tolerant species. Altered growth and demographic trends driven by drought and fire exclusion can serve as the mechanism for changing species distributions and community reorganization across landscape climatic gradients. Full article

Assessing long-term hydroclimatic variability in central Mexico is essential to understand regional water availability and groundwater recharge for urban centers such as Querétaro. This study developed a multi-century winter–spring precipitation reconstruction for the Sierra Gorda Biosphere Reserve (SGBR) using ring width chronologies of Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco. Standard dendrochronological techniques were applied to develop a 284-year master chronology (1731–2015). Following the accepted Subsample Signal Strength criterion (SSS ≥ 0.85) for chronology reliability, the reconstruction was restricted to the 1744–2015 period, yielding a statistically robust 271-year December–April precipitation record. A bootstrapped ordinary least-squares regression model relating tree-ring indices to instrumental December–April precipitation was calibrated and validated using split-sample cross-validation, explaining 46% of the instrumental precipitation variance (R² = 0.46) and yielding positive verification statistics (RE = 0.38–0.58; CE = 0.37–0.57). Spatial field correlations against gridded climate data (CRU TS4.08) confirmed a broad regional hydroclimatic signal centered over the Sierra Madre Oriental. Continuous wavelet transform (CWT), spectral analysis, superposed epoch analysis (SEA), and wavelet coherence (WTC) revealed significant interannual (2–8 years) and decadal (10–20 years) variability associated with large-scale ocean–atmosphere climate modes, including the El Niño–Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), Atlantic Multidecadal Oscillation (AMO), and Tropical North Atlantic (TNA) index. The pronounced sensitivity of these conifer forests to pre-monsoonal moisture deficits highlights their vulnerability to projected warming and increasing spring evapotranspiration stress. Although the reconstruction is limited to pre-monsoonal (December–April) precipitation, it provides a robust centuries-long baseline for contextualizing regional hydroclimatic variability and supports water-resource management, groundwater conservation, and climate-adaptation strategies in central Mexico. Full article

There is limited information on the effects of irregular-spaced and clumped planting on forest production and structural diversity. We explored Tagetes patula L. development as a model system to demonstrate stand development under varying planting patterns, and conceptualized in the context of Pseudotsuga menziesii (Mirb.) Franco mesic production forests of the Pacific Northwestern USA. Two variable planting patterns, clumps of 24 plants and of four plants, were compared to square regular patterns in replicate growing boxes. Spatial patterns were compared post-planting and at maturation, along with stand-level metrics and final dry weights, and stand structural statistics were used to compare production and diversity. The clumped spatial structure of 24-plant clumps was maintained to maturity. Groups of four plants maintained clumping at small scales and regular patterns at larger scales. Initial Regular-Square spacing remained at 2 cm at maturity but became indistinguishable from random patterns at larger scales. There was (1) overall greater mean directional index for the Large-Clumped patterns and greater spatial complexity indices for both clumped patterns, (2) greater social class (size) mean mingling index for small clumps, and (3) higher mean dominance index and mean differentiation index and lower crown volume complexity and height-to-diameter ratios for Regular-Square spacing. The structural complexity was accompanied by limited differences in dried weights by plant tissue (total weight, stem, leaf, flower weight) or plant biometric parameters (stem straightness, crown ratio, crown volume, number of leaves and flowers). The results from irregular planted marigold stand development are discussed in the context of increasing forest stand complexity, potentially without compromising productivity. Full article

Tannin-boron (TB) treatment is an effective method for enhancing the biological resistance of some types of wood, although knowledge regarding its efficacy as a preservative in a wider range of wood is limited. In this study, we investigated the effects of TB treatment on the mechanical and microscopic properties, and on biological resistance of six types of wood (Pinus massoniana Lamb., Cunninghamia lanceolata (Lamb.) Hook, Pseudotsuga menziesii (Mirb.) Franco, Intsia bijuga (Colebr.) Kuntze, Tectona grandis L. f., and Quercus mongolica Fisch. ex Ledeb.). The results showed that the six types of wood exhibited different boron retention after leaching, with the highest retention rate, 21.85%, observed in P. massoniana. The TB treatment did not significantly alter the original density and compressive strength of the wood, except in the case of I. bijuga, where the compressive strength significantly decreased after treatment. Scanning electron microscopy revealed that TB preservative is attached around the tracheids of softwood, or deposited within the vessels of hardwood. No-choice feeding tests showed that the TB-treated wood exhibited high resistance to Coptotermes formosanus with a maximum weight loss of 2.5%. TB treatment significantly improved the resistance of P. massoniana, C. lanceolata, P. menziesii, and T. grandis to Trametes hirsuta. These results demonstrate the potential usefulness of TB preservatives in different wood types. Full article

In 2020, a high-intensity wildfire burned over 35,000 ha in the Santa Cruz Mountains of California, including over 1700 ha of old-growth coast redwood forest. This event created a unique opportunity to evaluate post-fire succession. We compared vegetation recovery in high versus low/moderate severity burned areas using data collected one year and four years following the fire. Random plot sampling was conducted at Big Basin Redwoods State Park to assess the regeneration of trees, shrubs, and herbaceous species. Descriptive and inferential statistical analyses were used to assess recovery over time and across burn severities. Results indicate significant increases in shrub cover and richness over time, with a positive association between shrub recruitment and high-severity fire. Notably, the fire-adapted species blue blossom (Ceanothus thyrsiflorus Eschsch.), which was not recorded one year following the fire, dominated the shrub layer after four years, particularly in higher severity areas. Herbaceous species also exhibited an increase in cover and richness over time, though a substantial portion of that increase was based on non-native species recruitment. Analysis did not indicate a significant relationship between fire severity and herbaceous species recovery, however. The regeneration of tree species occurred both through seedling recruitment and basal sprouting. The recruitment of basal sprouts was prolific following the fire, particularly for coast redwood. The number of basal sprouts declined significantly during the time frame of this study, as the sprouts became larger and began to self-thin. Seedling abundance, on the other hand, exhibited an approximately 30-fold increase. Seedling recruitment was primarily driven by coast redwood (Sequoia sempervirens [Lamb. ex D.Don] Endl) and Douglas fir (Pseudotsuga menziesii [Mirb.] Franco) and was positively correlated with low/moderate fire severity. These findings underscore the complex interactions shaping post-fire forest dynamics and highlight the importance of understanding such patterns to inform management strategies that support the resiliency of coast redwood forests in an era of increasing wildfires. Full article

Douglas fir (Pseudotsuga menziesii [Mirb.] Franco) is a valuable timber species native to western North America that was introduced to Europe in the 19th century. The objective of this study was to select the most valuable and stable Douglas fir provenances in Romania by combining growth and quality traits, using two indices recently used in forest tree species: the multi-trait genotype–ideotype distance index (MGIDI) and the multi-trait stability index (MTSI). The study was conducted across three common garden experiments in Romania, established in 1977, evaluating 61 provenances from the United States, Canada, Germany, France, and Romania. The analyzed traits were diameter at breast height (DBH), total height (TH), and pruned height (PH). Significant genotype–environment interactions were observed, with the Douglas fir showing superior growth performance in one of the testing sites in western Romania (Aleșd). The MGIDI and MTSI identified high-performing provenances from diverse geographic origins, including the Pacific Northwest, Europe, and Canada. Selection differentials ranged from 2.8% to 10.9% for individual traits, highlighting the potential for genetic improvement. The selected provenances represent valuable genetic resources of Douglas fir that are adapted to environmental conditions in the Carpathian region, contributing to the development of climate-adaptive breeding strategies and sustainable forest management. Full article

Distance to the pith is a parameter that is known to be correlated with the mechanical properties of wood, but it is not utilized in strength grading machines. This study aimed to investigate how different the mechanical properties and grading yields are for Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) boards with small and large distances to the pith, respectively, and whether the distance to the pith could be an interesting parameter to use for strength grading in combination with other predictor variables. For this purpose, 221 boards were scanned to obtain fiber orientation and local density. Their dynamic modulus of elasticity and distance to the pith were measured, and they were finally tested in bending. The boards were classified into two categories: corewood if a board’s cross-section was entirely located within a radius of 200 mm from the pith, and outerwood otherwise. The results show that corewood presents lower mechanical properties than outerwood, explained especially by the higher knottiness of corewood. Distance to the pith improves the grading yields of a machine based on fiber orientation measurements, but using the dynamic modulus of elasticity rather than the distance to the pith leads to better results. Distance to the pith can be used as a single or secondary parameter to predict timber strength if the dynamic modulus of elasticity is not used. Full article

This study evaluates the performance of the ZEB Horizon RT portable mobile laser scanner (MLS) in simulating silvicultural thinning operations across three different Tuscan forests dominated by Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), Italian cypress (Cupressus sempervirens L.), and Stone pine (Pinus pinea L.). The aim is to compare the efficiency and accuracy of the MLS with traditional dendrometric methods. The study established three marteloscopes, each covering a 50 m × 50 m plot area (0.25 ha). Traditional dendrometric methods involved a team georeferencing trees using a total station and measuring the diameter at breast height (DBH) and selected tree heights (H) to calculate the growing stock volume (GSV). The MLS survey was carried out by a two-person team, who processed the point cloud data with LiDAR 360 software to automatically identify the tree positions, DBH, and H. The methods were compared based on the time, cost, and simulated felling volume. The MLS method was more time-efficient, saving nearly one and a half hours per marteloscope, equivalent to EUR 170. This advantage was most significant in denser stands, especially the Italian cypress forest. Both methods were comparable in terms of accuracy for Douglas-fir and Stone pine stands, with no significant differences in felling number or volume, although greater differences were noted for the Italian cypress forest. Full article

The foraging behavior of ruminating ungulates significantly impacts forest ecosystems due to their nutritional requirements. This study focuses on inter-specific comparisons of bark browsing (stripping) between Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) and silver fir (Abies alba Mill.). Field measurements were conducted at the previously established research demonstration site “Husárik” in the Javorníky Mountains, north-western Slovakia. We measured the sizes of wounds on stems and assessed the dimensions of unrecovered parts of wounds, subsequently calculating areas of recovered bark patches. Then, the total areas of wounds recovered patches, and unrecovered parts were measured. Additionally, the percentages of wound areas, recovered areas, and unrecovered areas were expressed as proportions relative to the total bark surface. Influencing factors such as the position of wounds along the vertical stem profile and stem diameter class were analyzed using two- and three-way ANOVA followed by Fisher’s LSD test. The results demonstrate the susceptibility of both tree species to bark browsing by ruminating ungulates, primarily red deer (Cervus elaphus L.) in our study site. Douglas fir exhibited slightly less intense browsing compared to silver fir, while silver fir had a slightly higher recovery rate. Specifically, 17.0% of the bark surface in Douglas fir and 21.5% in silver fir were browsed. The proportions of recovered areas on wounds were 62.5% and 69.6% in Douglas fir and silver fir, respectively. Regarding the vertical stem profile, the most intense browsing occurred at a height of 101–125 cm from the ground level, with rates of 40.7% in Douglas fir and 47.0% in silver fir. Browsing intensity showed negligible variation among diameter classes, which were classified as up to 35 mm, 35–50 mm, and over 50 mm. Our findings suggest that, as an introduced species, Douglas fir is not a suitable substitute for other commercially significant tree species in supporting sustainable forestry in European countries where ruminating ungulates are overabundant. Full article

Successful regeneration of commercial species is central to the long-term sustainability of forests managed for wood production. We studied two species of tree seedlings planted after group selection and single-tree selection harvesting in a 20 ha replicated silviculture experiment in stands dominated by coast redwood (Sequoia sempervirens (D.Don) Endl.). Treatments consisted of complete harvest in 1 ha group selection opening (GS), low-density dispersed retention (LD), aggregated high-density retention (HA), and dispersed high-density retention (HD). One year after planting, seedlings planted on a southwest aspect had the lowest survival rate, while northeast aspects had nearly complete survival rates. As expected, redwood had a higher survival rate than coast Douglas-fir (Pseudotsuga menziesii var menziesii (Mirb.) Franco). Survival rates exhibited a rise-peak-fall pattern with stand density, most notably on southwest-facing slopes, ranking LD > HA ≈ HD > GS treatments. Deer browsing of planted seedlings was a pervasive problem where Douglas-fir were preferentially browsed over redwood. In treatments with higher retention densities, browsing was less likely, ranking GS > LD > HA > HD treatments. Further from watercourses at higher elevation, the probability of browsing diminished. Overall, dispersed treatments outperformed aggregated and GS treatments by simultaneously maximizing survival and minimizing browsing of planted seedlings. We did not perform site preparation or herbicide treatment of re-sprouting hardwoods following harvest, and therefore recommend testing the effectiveness of understory vegetation management to enhance seedling survival. Consideration could also be given to planting more seedlings in anticipation of lower survival rates, and/or implementing seedling protection measures when and where heavy browsing is expected. Full article

Relatively little is known about whole-plant fungal communities (mycobiome) and associated soil nematodes, especially with respect to woody plant seedlings and disturbance caused by forest harvesting. In a growth chamber experiment, we tested simulated clear-cut soil conditions on shoot biomass, total soil nematode density, and the shoot and root mycobiome of Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, seedlings. Soil treatments included unamended bare soil and soil amended with root segments of kinnikinnick, Arctostaphylos uva-ursi (L.) Spreng., pinegrass, Calamagrostis rubescens Buckley, or P. menziesii seedlings. We used next-generation Illumina sequencing and the PIPITS pipeline to obtain fungal taxa used for mycobiome community richness and Jaccard-based taxonomic normalized stochasticity ratio to assess mycobiome community assembly stochasticity. Total nematode density, measured from Baermann funnel extractions, increased in soils supplemented with A. uva-ursi or C. rubescens root segments. Root mycobiomes were more stochastic in the A. uva-ursi than P. menziesii or the bare conditions, whereas the shoot mycobiome was more stochastic in the C. rubescens treatment than in the P. menziesii treatment. Our results suggest that refugia plants impact the phyto-biome, in this case plant-associated nematodes and the stochasticity of root and shoot mycobiome community assembly, while not showing noticeable impacts on above-ground plant growth. Full article

Theoretical tree crop ideotypes have long and narrow live crowns with a high total leaf area. This crown form allows more efficient exploitation of site resources, in part by physically occupying less growing space per unit leaf area and by packing a greater number of trees into a given area. Genetic selection for crop ideotypes has been proposed as a strategy for maximizing productivity per unit area in stands managed under intensive silviculture. The primary objective of this study was to test the relationship between the relative growth performance of different families in a Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco) progeny test and morphological crown attributes that conform to a theoretical crop ideotype. The overarching goal was to identify attributes conferring superior height and diameter growth on families and to facilitate the incorporation of these attributes and associated growth mechanisms into hybrid growth models for intensively managed plantations. Crown structural attributes were measured on destructively sampled trees and averaged for the entire crown and each third of live crown length among families. Multivariate analysis revealed that crown attributes averaged over the entire crown performed best for identifying families with different height and diameter growth, followed successively by the bottom, middle, and top crown third. Trees with relatively short branch lengths and steep branch angles tended to have higher total leaf area per unit crown length (TLACL), and this structural attribute showed a strong positive correlation with cumulative diameter growth. The ratio of crown width to crown length (CWL) was moderately and negatively correlated with cumulative height growth. The families displaying the most rapid diameter growth in this progeny test conformed to a theoretical crop ideotype, while those with the most rapid height growth displayed crown attributes with a less obvious relationship to the crop ideotype concept. TLACL implied one possible mechanism driving genetic gain in Douglas-fir families, given its high heritability and strongly positive correlation with growth performance. Incorporating TLACL as an explanatory variable in diameter growth models could at least partly represent different genetic levels. TLACL is less strongly correlated with height growth rate, so incorporating CWL may better represent genetic effects on height growth models. Full article

This study investigated the variations in tracheid length of Pseudotsuga menziesii (Mirb.) Franco from three sites in Croatia in relation to cambium age, within- and between-site differences, and growth rate. Tracheids are the main structural element in P. menziesii wood, varying in length following different patterns that should be precisely determined. After the maceration procedure, earlywood tracheid length (EWTL), latewood tracheid length (LWTL), annual growth ring tracheid length (RTL), earlywood ring width (EWW), latewood ring width (LWW), and annual ring width (ARW) were measured in selected annual growth rings. The significant effect of annual growth rings and zone interaction for EWTL and LWTL, as well as of annual growth rings, trees, and sites for RTL, was determined. The results conclude on the differences between the trends in EWTL and LWTL from pith toward the bark. In addition, the correlation analysis between the tracheid length and different growth patterns was investigated, and very weak or no association between the variables was detected. This research contributes to better understanding the degree of wood uniformity of P. menziesii from the technological perspective, as well as the variability factor in the optimization of forest management with favoring overall wood quality. Full article

Proxy records from the late Quaternary help in understanding climate variability on extended time scales. An ancient landslide deposit in Oregon U.S.A. preserved large logs from Douglas fir trees (Pseudotsuga menziesii (Mirb.) Franco) and afforded an opportunity to explore the response of tree growth to climate on annual and decadal scales. High-precision radiocarbon dating indicates an age exceeding 63 ka, i.e., the trees grew within the generally cool Marine Isotope Stage 5 (MIS 5), likely during a warmer interval optimal for Douglas fir establishment. This would include the prolonged warm MIS 5e (ca. 110–130 ka), corresponding approximately to the Eemian interglacial, which was warm like the current Holocene interglacial. A 297-year tree-ring width chronology from 12 Douglas fir logs and 227-year tree-ring δ¹³C and δ¹⁸O records are analyzed with spectral and wavelet analysis. Variance of the ancient rings is consistent with modern Douglas fir growth sensitive to moisture and ecological disturbances. Spectra of ancient and modern chronologies are dominated by low frequencies with significant spectral peaks appearing at high frequencies (2.1–4 years) and cyclic behavior transient over centuries. It is conceivable that the O-isotopes track moisture and that C-isotopes track temperature or sunlight. The findings illustrate the challenges in assessing the response of ancient tree-ring properties to late Quaternary climate variability. Full article

There is debate on which tree species can sustain forest ecosystem services in a drier and warmer future. In Europe, the use of non-native timber species, such as Douglas fir (Pseudotsuga menziesii [Mirb.] Franco), is suggested as a solution to mitigate climate change impacts because of their high growth resilience to drought. However, the biogeographical, climatic and ecological limits for widely planted timber species still need to be defined. Here, we study the growth response to climate variables and drought of four Douglas fir plantations in northern Spain subjected to contrasting climate conditions. Further, we measure wood density in one of the sites to obtain a better understanding of growth responses to climate. Correlative analyses and simulations based on the Vaganov–Shaskin process-based model confirm that growth of Douglas fir is constrained by warm and dry conditions during summer and early autumn, particularly in the driest study site. Minimum wood density increased in response to dry spring conditions. Therefore, planting Douglas fir in sites with a marked summer drought will result in reduced growth but a dense earlywood. Stands inhabiting dry sites are vulnerable to late-summer drought stress and can act as “sentinel plantations”, delineating the tolerance climate limits of timber species. Full article