Douglas-fir Plantations Research Articles

Dynamics and Vertical Distribution of Roots in European Beech Forests and Douglas Fir Plantations in Bulgaria

Identifying patterns in roots spatial distribution and dynamics, and quantifying the root stocks, annual production and turnover rates at species level is essential for understanding plant ecological responses to local environmental factors and climate change. We studied selected root traits in four different stands, two European beech (Fagus sylvatica L.) forests and two Douglas fir (Pseudotsuga menziezii Mirb. Franco) plantations. Root system vertical distribution and dynamics were studied using sequential coring method and characterised into three root diameter size classes (0–2, 2–5 and 5–10 mm) sampled at three different soil depths (0–15, 15–30, 30–45 cm). Root annual production and turnover rates were analysed and quantified using Decision Matrix and Maximum-Minimum estimation approaches. The overall root mass (<10 mm diameter up to 0–45 cm soil depth) was higher in the beech forests than in the Douglas fir plantations. Some root traits, e.g., the overall root mass, the fine (0–2 mm) and small (2–5 mm) roots mass, differed significantly between the sampling plots rather than between the forest types. The root system revealed a tree species specific vertical distribution pattern. More than half of the fine and small roots biomass of the Douglas fir stands were allocated in the uppermost soil layer and decreased significantly with depths, while in the beech forests the biomass was more uniformly distributed and decreased gradually with increasing soil depth. Although both tree species belong to two different plant functional types and the stands were situated in two distantly located regions with different climatic and soil characteristics, we revealed similar trends in the root biomass and necromass dynamics, and close values for the annual production and turnover rates. The mean turnover rates for all studied stands obtained by sequential coring and Decision Matrix were 1.11 yr−1 and 0.76 yr−1 based on mean and maximum biomass data, respectively. They were similar to the averaged values suggested for Central and Northern European forests but higher compared to those reported from Southern Europe.

Profitability and risk sources in global timberland investments

As a long-term investment, timberland investments offer financial benefits including portfolio diversification, attractive risk/return profile, an inflation hedge, and the potential of cash flow. Based on interviews with experts regarding ranges of input parameters used in single-hectare financial models and Monte Carlo simulation method, we examine what are the main factors that influence internal rates of returns (IRRs) in several global timber plantation investment opportunities: loblolly pine on the U.S. Atlantic coastal plain; Douglas-fir plantations in the western U.S.; loblolly pine and eucalyptus plantations in Brazil; radiata pine and eucalyptus plantations in Chile; and pine and oak stands in Poland. The results show that excluding the price of land, biological growth and timber prices were the most influential variables that impacted the IRRs across global timberland investments. In addition, some country-specific factors, such as planting costs (Chile) and management costs (Poland and the U.S.), were identified as crucial when considering timberland investments in these countries. Investments in South America’s pine plantations are characterized by the same level of returns as eucalyptus opportunities, but with lower risk. The same was found for Douglas-fir investments in the Pacific Northwest compared to loblolly pine in the U.S. South. If Poland were an investable alternative, which is not the case so far, any investments in oak and pine stands are not recommended yet, given that for the same level of risk, better returns may be achieved in Douglas-fir plantations in the U.S. PNW. The Monte Carlo method utilized provides easily interpretable representation of the robustness of timberland investment estimates in selected regions and should become standard practice in forest-business decision making. However, more accurate probability density functions need to be determined in further research, using, for instance, historical data and kernel density estimation, rather than “lack of information” (triangular) distributions.

Contrasting the Pathogen Loads in Co-Existing Populations of Phytophthora pluvialis and Nothophaeocryptopus gaeumannii in Douglas Fir Plantations in New Zealand and the Pacific Northwest United States.

The emergence of Phytophthora pluvialis as a foliar pathogen of Douglas fir in New Zealand and the Pacific Northwest United States has raised questions about its interaction with the widespread Swiss needle cast (SNC) disease. During Spring 2017, we repeatedly sampled 30 trees along an environmental gradient in each region and 292 additional trees in a longitudinal transect to assess the P. pluvialis epidemic and the association between P. pluvialis and Nothophaeocryptopus gaeumannii, which are causal agents of SNC. Both pathogens were consistently more abundant in the host's exotic environment in New Zealand. In both areas, the two pathogens co-exist in different spatial scales for regions and needles. The relative abundance of both pathogens was negatively correlated in the Pacific Northwest, where both presumably have co-existed for longer. Our findings confirmed the interaction of P. pluvialis and N. gaeumannii as foliar pathogens of Douglas fir and suggest a within-site spatial variation in the Pacific Northwest.

Forest inventory sensivity to UAS-based image processing algorithms

Frequent and accurate estimation of forest structure parameters, such as number of trees per hectare or total height, are mandatory for sustainable forest management. Unmanned aircraft system (UAS) equipped with inexpensive sensors can be used to monitor and measure forest structure. The detailed information provided by the UAS allows tree level forest inventory. However, tree identification depends on a variety of parameters defining the image processing and tree segmentation algorithms. The objective of our study was to identify parameter combinations that accurately delineated trees and their heights. We evaluated the impact of different tree segmentation and point cloud generation algorithms on forest inventory from imagery collected with a UAS over a mature Douglas-fir plantation forest. We processed the images with two commonly used commercial software packages, Agisoft PhotoScan and Pix4Dmapper, both implementing image processing algorithms called Structure from Motion. For each software we generated photogrammetric point clouds by varying the parameters defining the implementation. We segmented individual trees and heights using three tree algorithms: Variable Window Filter, Graph-Theoretical, and Watershed Segmentation. We assessed the impact of image processing algorithms on forest inventory by comparing the estimated trees with trees manually identified from the point clouds. We found that the type of tree segmentation and image processing algorithms have a significant effect in accurately identifying trees. For tree height estimation, we found strong evidence that image processing algorithms had significant effects, whereas tree segmentation algorithms did not significantly affect tree height estimation.These findings may be of interest to others that are using high-resolution spatial imagery to estimate forest inventory parameters.

Managing Fragmented Fire-Threatened Landscapes with Spatial Externalities

Abstract Accounting for externalities generated by fire spread is necessary for managing fire risk on landscapes with multiple owners. In this paper, we determine the optimal management of a synthetic landscape parameterized to represent the ecological conditions of Douglas-fir (Pseudotsuga menziesii) plantations in southwest Oregon. The problem is formulated as a dynamic game, where each agent maximizes their own objective without considering the welfare of the other agents. We demonstrate a method for incorporating spatial information and externalities into a dynamic optimization process. A machine-learning technique, approximate dynamic programming, is applied to determine the optimal timing and location of fuel treatments and timber harvests for each agent. The value functions we estimate explicitly account for the spatial interactions that generate fire risk. They provide a way to model the expected benefits, costs, and externalities associated with management actions that have uncertain consequences in multiple locations. The method we demonstrate is applied to analyze the effect of landscape fragmentation on landowner welfare and ecological outcomes.

Severity of Swiss needle cast in young and mature Douglas-fir forests in western Oregon, USA

Swiss needle cast (SNC), caused by Nothophaeocryptopus gaeumannii, is an important foliage disease of Douglas-fir (Pseudotsuga menziesii) forests of the Pacific Northwest. The fungus lives endophytically within the foliage, until forming reproductive structures (pseudothecia) that plug stomates and cause carbon starvation. When pseudothecia appear on one- and two-year-old foliage, significant needle abscission can occur, which reduces productivity of the tree. While there is considerable evidence of SNC disease in coastal Douglas-fir plantations, the severity of SNC in mature and old-growth forests is poorly understood. We compared tree crowns of mature and old-growth conifer forests and nearby young forests at three locations in the Oregon Coast Range and four locations in the western Cascade Range of Oregon. We assessed disease severity for N. gaeumannii on two-year-old foliage, incidence by presence of N. gaeumannii on all foliage, foliage retention for the first four years, and foliar nitrogen of one-year-old foliage. We also compared leaf wetness at three heights in one mature and one young tree at five of the seven sites. Disease severity was greater in young forests than mature forests at all sites except for high elevation Cascade Range areas. Incidence of disease was highest for two-year-old needles in young trees and 3–5 year-old needles in mature trees, except for one coastal site. Retention of 1–4 year-old needle cohorts differed between young and mature trees, and mature trees had much larger complements of > four-year-old needles. Total foliar nitrogen (TN) concentration did not differ in needles of young and mature trees, but at some locations total N differed between canopy positions. Leaf wetness differences were not consistent between young and mature tree crowns. However, at one study site in the core epidemic area, the younger stand had longer periods of wetness in the upper crowns than a nearby old stand. Leaf wetness and foliar N were hypothesized to play a role in SNC disease severity, but they do not explain differences in adjacent young and mature trees. Although the fungus is present in old and young trees, the likelihood of disease expression and lower foliage retention appears to be greater in younger plantation trees than mature and older trees in western Oregon Douglas-fir forests.

Динаміка біологічної активності ґрунтів лісових біогеоценозів Присамар’я

Представлены результаты исследований одного из показателей биологическойактивности почв – содержание углекислого газа, характеризующее интенсивностьдыхания в почвах. Установлено, что биологическая активность почв исследованныхнасаждений Quercus robur L. приближалась к активности в природных лесных био-геоценозах и зависела от сезонной динамики, лесорастительных условий, типа дре-востоя, влажности и др.

Varijabilnost prečnika smolnih kanala u četinama različitih provenijencija duglazije

Douglas-fir is the most commonly grown allochthonous species in the forests of Europe. Growth speed, adaptive power, favorable wood properties, as well as low sensibility to pests are the attributes that have contributed the most to the success and occurrence of Douglas-fir plantations in Europe. Introduction program of an exotic species includes testing of its provenances in new ecosystems and localities. In Serbia, testing of the genetic potentials of Douglas-fir, native to North America, has begun by seting up provenance trials on several locations. Afforestation with exotic tree species must be justified and it should fulfill the aims of the introduction. Therefore, it is neccessary to test all the traits of the introduced species to show the effects of ecological factors. The aim of this research was to determine the ecological adaptations of Douglas-fir in Serbia by studying its anatomic characteristics. In the paper, the influence of locality conditions on the diameter of resin canals in the needles of different Douglas-fir provenances was investigated on the sites where the provenance tests were set up. A two-way ANOVA was performed, by investigating the effects of site and provenance factors on the diameter of resin canals. Resin canals serve as an important diagnostic taxonomic characteristic in conifers, while resin itself has important physiological and protective role in conifers.

Effects of Douglas Fir Stand Age on Soil Chemical Properties, Nutrient Dynamics, and Enzyme Activity: A Case Study in Northern Apennines, Italy

The aim of this study was to determine the effect of a Douglas fir plantation along a stand chronosequence in the North Apennine (Italy) on soil carbon and nitrogen stocks, as well as on soil chemical and biochemical properties involved in the nutrients biogeochemical cycle. In 2014, three sites of Douglas fir stands, aged 80, 100, and 120 years, were selected in Vallombrosa forest to study the dynamics of soil nutrients in the ecosystem. Along the Douglas fir chronosequence, general evidence of surface element accumulation was found, including a conspicuous increase of alkaline element with respect to Al, which was attributed to the increase of soil pH along the Douglas fir stand age classes. A general increase of specific enzyme activity (per unit of organic carbon) and functional diversity were observed in the epipedon of the Douglas fir stand over 100 years of age. Moreover, the (chitinase + leucine aminopeptidase) to acid phosphatase ratio progressively increased from 0.15 to 0.31 in the epipedon of the chrononsequence, while the β-glucosidase to (chitinase + leucine aminopeptidase) ratio decreased from 1.45 to 0.83, suggesting nitrogen limitation with respect to carbon. In fact, the soil carbon stock progressively increased along the chronosequence, in the epipedon from 17 to 53 Mg C ha−1 and in the endopedon from 17 to 37 Mg C ha−1. Conversely, the soil nitrogen stock increased from 1.2 to 2.4 Mg N ha−1, but not over the 100-year-old stand class. In conclusion, soil organic matter accumulation became sufficient to define the umbric horizon in the Northern Apennines when the Douglas fir plantation reached the age of 100 years. Over this age class of plants, a limitation of soil nitrogen may occur, affecting enzyme activities regulating the biogeochemical cycle of nutrients.

Estimating shallow soil available water supply for Douglas-fir forests of the coastal Pacific Northwest: climate change impacts

Douglas-fir forests of the coastal Pacific Northwest experience yearly summer droughts; however, the variation in shallow soil available water supply throughout the region is not well understood nor is the effect of future climate change. Soil moisture sensors were installed in 60 Douglas-fir plantation forests over 6 years. Stands were grouped by physiographic regions to describe differences in climate and available water supply. Monthly available water supply (MAWS) (0–50 cm) was calculated as the average daily available moisture content. MAWS was modeled using monthly climate variables, and the equation was then used to predict the change in MAWS due to mild, moderate, and severe climate change predictions. Regional monthly air temperature and precipitation were strongly predictive of MAWS. Mild to severe climate change are predicted to decrease yearly available water supply by 8% to 19%, while summer available water supply will decrease from 25% to 72%. The greatest decreases due to climate change will be found in the coastal regions of Washington and Oregon due to greater negative effects of temperature on available water supply. Climate change, especially the most severe predictions, was shown to have a sizeable effect on shallow soil available water supply in coastal Douglas-fir forests.

Logging debris and herbicide treatments improve growing conditions for planted Douglas-fir on a droughty forest site invaded by Scotch broom

Abstract Logging debris has the potential to benefit forest regeneration by increasing resource availability, modifying microclimate, and altering plant community structure. To understand potential mechanisms driving these benefits, we initiated research at a forested site on the Olympic Peninsula, WA that contained the invasive, nonnative competitor, Scotch broom (Cytisus scoparius). Immediately after harvesting the stand of mature coast Douglas-fir (Pseudotsuga menziesii var. menziesii) in late 2011, two levels of logging debris retention were created on replicated plots: 18.9 and 9.0 Mg ha−1, with debris depths averaging 32 and 17 cm, respectively. Within each plot, three herbicide treatments (aminopyralid (A), triclopyr ester (T), and A + T) and a non-sprayed control were applied to split plots in August 2012. Douglas-fir seedlings were planted in early 2013, and microclimate and seedling performance were monitored through 2016. During the growing seasons of 2012–2014, soil water content was greater and soil temperature was lower under heavy debris than under light debris. Survival of planted Douglas-fir seedlings declined an average of 45 and 11 percentage points after intense summer droughts in 2015 and 2016, respectively, but it averaged 7–10 percentage points greater in heavy debris than in light debris during this period. Douglas-fir stem diameter growth was consistently greater in heavy debris than in light debris, with the exception of treatment A + T where diameter did not differ between debris treatments. A reciprocal regression model (R2 = 0.55) predicted that total stem volume of Douglas-fir increased from 19 to 84 dm3 ha−1 as Scotch broom cover decreased from 20% to 0% as a result of the logging debris and herbicide treatments. There were limited treatment effects on mineral soil chemical and physical properties, but forest floor mass and nutrient content were increased in the heavy debris treatment. Five years after forest harvesting (2016), logging debris mass in heavy debris differed little from that in light debris at study initiation, indicating a substantial reduction in fuels and the potential for severe wildfire. Results suggest that, on gravelly soils and possibly other droughty forest ecosystems in the Pacific Northwest, heavy debris will benefit planted Douglas-fir by improving growing conditions and by limiting abundance of nonnative competitors, such as Scotch broom.

Evaluating Carbon Stock Changes in Forest and Related Uncertainty

For the evaluation of changes in the carbon stock of living biomass, two methods are reported in the Good Practice Guidance for Land Use, Land-Use Change, and Forestry: (1) the default method, which requires the biomass carbon loss to be subtracted from the biomass carbon increment for the reporting year; and (2) the stock change method, which requires two consecutive biomass carbon stock inventories for a given forest area at two points in time. We used three methods to estimate above-ground biomass: (1) application of allometric equations, (2) constant BEF (biomass expansion factor), and (3) age-dependent BEF, following which we evaluated the changes in carbon stock and the related uncertainty. Our study was carried out in a Douglas fir plantation composed of plots with three different planting densities, monitored at three different ages (15, 25, and 40 years old). Results showed the highest uncertainty in the estimates based on the constant BEF, whereas the use of allometric equations led to the lowest uncertainty in the estimates. With a constant BEF, it is usually difficult to obtain a reliable value for the whole tree biomass because stem proportion increases with tree size at the expense of the other components. The age-dependent BEFs aim to reduce the bias representing the actual change in stock, thus we found a lower uncertainty in the estimates by using this method compared to the constant BEF. The default method had the highest uncertainty (35.5–48.1%) and gave an estimate higher by almost double compared to the stock change method, which had an uncertainty ranging from 2.9% (estimated by the allometric equation) to 3.4% (estimated by the constant BEF).

Biomass conversion and expansion factors in Douglas-fir stands of different planting density: variation according to individual growth and prediction equations

Aim of study: We built biomass expansion factors (BCEFs) from Douglas-fir felled trees planted with different planting densities to evaluate the differences according tree size and planting density.Area of study: The Douglas-fir plantation under study is located on the northern coastal chain of Calabria (Tyrrhenian side) south Italy.Materials and methods: We derived tree level BCEFs, relative to crown (BCEFc), to stem (BCEFst = basic density, BD) and total above-ground (BCEFt) from destructive measurements carried out in a Douglas-fir plantation where four study plots were selected according to different planting densities (from 833 to 2500 trees per hectare). The measured BCEFs were regressed against diameter at breast height and total height, planting density, site productivity (SP) and their interactions to test the variation of BCEFs. Analysis of variance (ANOVA) and the post hoc Tukey comparison test were used to test differences in BCEFt, BCEFc and in BD between plots with different planting density.Main results: BCEFs decreased with increasing total height and DBH, but large dispersion measures were obtained for any of the compartments in the analysis. An increasing trend with planting density was found for all the analyzed BCEFs, but together with planting density, BCEFs also resulted dependent upon site productivity. BCEFt average values ranged between 1.40 Mg m-3 in planting density with 833 trees/ha (PD833) to 2.09 Mg m-3 in planting density with 2500 trees/ha (PD2500), which are in the range of IPCC prescribed values for Douglas-fir trees.Research highlights: Our results showed that the application of BCEF to estimate forest biomass in stands with different planting densities should explicitly account for the effect of planting density and site productivity.

Projecting Nonnative Douglas Fir Plantations in Southern Europe with the Forest Vegetation Simulator

Projecting Nonnative Douglas Fir Plantations in Southern Europe with the Forest Vegetation Simulator

The effects of gap size in a group selection silvicultural system on the growth response of young, planted Douglas-fir: a sector plot analysis

The effects of gap size in a group selection silvicultural system on the growth response of young, planted Douglas-fir: a sector plot analysis

Ecology and pathology of Phytophthora ITS clade 3 species in forests in western Oregon, USA

ABSTRACTPhytophthora species are widespread and diverse in forest ecosystems, but little is known about their ecology. We explore ecological attributes of the closely related clade 3 species that occur sympatrically in western North American forests. We address the population structure, pathology, and epidemiology of P. ilicis, P. nemorosa, P. pluvialis, P. pseudosyringae, and P. psychrophila. Phytophthora species were isolated from plant tissues, rainwater falling through the forest canopy, streams, and soils in forests in western Oregon. Species identifications were based on morphology in culture with molecular confirmation using COX spacer and internal transcribed spacer (ITS) sequences. All five clade 3 Phytophthora species are present in western Oregon forests, although P. ilicis (only 1 forest isolate) and P. psychrophila (only 12 isolates) are apparently rare. P. ilicis is known only from holly in horticultural situations and once from a naturalized seedling in an urban forest. The known distribution of P. nemorosa in forest settings coincides with the ranges of its principle hosts, tanoak and myrtlewood, in Oregon and California. Although it is regularly identified from streams within the tanoak range, it has not been recovered from streams beyond that range. P. pluvialis is primarily associated with Douglas-fir canopies. It was identified from scattered locations throughout western Oregon in rain traps beneath Douglas-fir plantations and from diseased needles. P. pseudosyringae is also isolated from tanoak and myrtlewood in southwest Oregon and California, but its distribution, in streams at least, extends throughout much of western Oregon. P. psychrophila in Oregon is known only from rain traps beneath tanoak trees. Little intraspecific variation was detected in the nuclear rDNA ITS of clade 3 species. Variation in the mitochondrial COX spacer region was more frequent, with 2 to 10 haplotypes identified in the clade 3 species, for which we had multiple isolates.

Varijabilnost broja epitelnih ćelija u smolnom kanalu četina duglazije

The research on the interactions between the genetic potential of introduced provenances and the environmental features of the locations in which the plantations were established was carried out in Douglas-fir plantations in Serbia. The twoway ANOVA was conducted in order to study the effects of the site conditions in the localities of Douglas-fir provenance tests in Serbia on the anatomical properties of needles. These analyses look into the effects of two factors (locality and provenance) on the number of epithelial cells in the resin duct of Douglas-fir needles.

Determining the Effects of Biogeoclimatic Properties on Different Site Index Systems of Douglas-fir in the Coastal Pacific Northwest

Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) site index is commonly used as a measure of site productivity in many regions of the world, including the US Pacific Northwest. However, site index presents numerous limitations as a measure of site productivity because it is based on top height growth potential, which has been estimated in stands managed under many alternative silvicultural regimes. Three alternative site index systems (King's, Nigh's, and Flewelling's) and a forest company-reported site index were examined and compared according to biogeoclimatic variables from 71 Douglas-fir installations throughout the coastal Pacific Northwest. Climate, physiographic, soil water, and soil nitrogen (N) properties and stand variables from mapped sources and from field measurements were examined as predictors of site index. The best site and soil productivity variables for predicting Douglas-fir growth using these site indices were identified by Pearson correlations and boosted regression tree models based on mapped predictors and a combination of mapped and measured predictors. All three site indices predicted greater height growth on stands with lower elevations, greater soil available water supply, lower surface soil and forest floor carbon to N ratios, and high stand relative densities. Models based on a combination of mapped and field-measured data tended to perform better than those from only mapped data, suggesting the importance of at least some field measurements for accurately assessing Douglas-fir site index. For these juvenile stands, all three site indices produced comparable height predictions and had similar effects from biogeoclimatic variables. The fact that the measured site index methods were more related to each other than to the company-reported site index suggests that site indices of intensively Douglas-fir plantations should be reassessed to improve volume growth and harvesting predictions.

Swiss Needle Cast in Western Oregon Douglas-Fir Plantations: 20‐Year Monitoring Results

Swiss needle cast (SNC), a foliar disease specific to Douglas-fir (Pseudotsuga menziesii), is caused by an endemic Ascomycete fungus (Phaeocryptopus gaeumannii). In the late 1980s and early 1990s significant symptoms began to appear in coastal Oregon, and these have been associated with the planting of Douglas-fir in the Sitka spruce zone, leaf wetness during potential spore dispersal in May–August, and mild winter temperature. The first annual aerial survey was initiated in 1996 and has continued through 2015, which indicates a significant increase in area of visible symptoms from the air, increasing from 53,050 ha in 1996 to 238,705 ha in 2015. Monitoring plots in the NW Oregon Coast Range verified impacts of SNC on tree growth and productivity, with growth reductions averaging about 23% in the epidemic area linked to needle retention. A series of monitoring plots was set up in the western Cascade Mountains of Oregon and 590 10–23-year old Douglas-fir trees in 59 stands were tracked for 10 years, measured in 2001, 2006, and 2011. No measureable growth impacts were noted in this region of Oregon. A new plot network is being installed throughout the Oregon and southwest Washington coastal ranges as a means of monitoring future disease impact and providing framework for additional studies.

Hierarchical neighbor effects on mycorrhizal community structure and function.

Theory predicts that neighboring communities can shape one another's composition and function, for example, through the exchange of member species. However, empirical tests of the directionality and strength of these effects are rare. We determined the effects of neighboring communities on one another through experimental manipulation of a plant‐fungal model system. We first established distinct ectomycorrhizal fungal communities on Douglas‐fir seedlings that were initially grown in three soil environments. We then transplanted seedlings and mycorrhizal communities in a fully factorial experiment designed to quantify the direction and strength of neighbor effects by focusing on changes in fungal community species composition and implications for seedling growth (a proxy for community function). We found that neighbor effects on the composition and function of adjacent communities follow a dominance hierarchy. Specifically, mycorrhizal communities established from soils collected in Douglas‐fir plantations were both the least sensitive to neighbor effects, and exerted the strongest influence on their neighbors by driving convergence in neighbor community composition and increasing neighbor seedling vigor. These results demonstrate that asymmetric neighbor effects mediated by ecological history can determine both community composition and function.