Western Gall Rust Research Articles

Pre-Commercial Thinning Increases Tree Size and Reduces Western Gall Rust Infections in Lodgepole Pine

Alberta’s forest industry is predicted to be impacted by a medium-term decline in timber supply. Intensive silviculture tools, such as pre-commercial thinning, have been shown to increase individual tree growth, shorten rotation lengths, and improve stand merchantability in important commercial species such as lodgepole pine. However, lodgepole pine stands are susceptible to western gall rust infections, and thinning at an early stage may increase infection rates. This study collected tree and stand level data from 33 operational harvest origin lodgepole pine stands consisting of 11 stands thinned at age 17–19 years (PCT_18), 11 stands thinned at age 23–25 (PCT_24), and 11 unthinned stands. Approximately 40 years after pre-commercial thinning, merchantable volume is similar in all stands but thinned stands, regardless of timing, had greater individual tree size (~15% higher) compared to unthinned stands. Pre-commercially thinned stands also had a higher potential for commercial thinning since they have lower variability in tree size and longer live crown lengths. In addition, delayed thinning (PCT_24) reduced western gall rust infections and the severity of infections compared to both PCT_18 and unthinned stands. In conclusion, pre-commercial thinning should be considered for lodgepole pine stands in order to address timber supply issues in Alberta.

Soil disturbance, amelioration and rehabilitation affect forest growth, health, soil carbon and chemistry on five long-term soil productivity (LTSP) sites in southeastern British Columbia

Soil disturbance amelioration affected tree survival, growth, health, mineral soil chemistry, and their covariation on five Long-Term Soil Productivity (LTSP) sites in southeastern British Columbia. The two most different LTSP treatments (baseline disturbance of no compaction / all organic matter left, versus most severe of heavy compaction / forest floor removed) were compared to five amelioration treatments: rehabilitation of most severe LTSP treatment (soil tillage with or without incorporation of removed forest floor [Rehab + FF]), root disease (Armillaria ostoyae (Romagn.) Herink) amelioration treatments (stump removal or biological with Hypholoma fasiculare), and enhancement of soil organic matter (tilling extra forest floor into mineral soil). Treatment significantly (p < 0.05) affected 10-year mineral soil carbon, nitrogen, sulfur, mineralizable nitrogen, and potassium, which were lower on forest floor removal treatments and higher on forest floor addition treatments (27 to 97% of baseline versus 78 to 183% of baseline, respectively). Western white pine (Pinus monticola Dougl. ex D.Don) 15-year productivity (m3/ha) was significantly affected by treatment (Rehab + FF yielding a 10 fold increase in productivity versus the poorly growing baseline treatment), with treatment also significant when total disease was a covariate and for average and total volume when mineral soil Ca:Al ratio was a marginally significant (p < 0.1) covariate, and for survival when the incidence of total disease or white pine blister rust (Cronartium ribicola) were significant covariates; or with mineral soil C:N ratio as a significant covariate. The incidence of blister rust and total disease were significantly influenced by treatment when C:N was a significant covariate. For 20-year lodgepole pine (Pinus contorta Dougl. Ex Loud) there were no direct relationships apparent, but western gall rust (Endocronartium harknessii) had treatment significant when total sulfur was a significant covariate. Fifteen- and twenty-year Douglas-fir (Pseudotsuga menziesii var. glauca [Beissn.] Franco) had no significant relationships. Results demonstrate that restoring or adding extra organic matter (forest floor) into mineral soil increased soil carbon and related nutrients and can increase above ground carbon (forest productivity). Conversely, removing forest floor lowered mineral soil carbon and generally lowered tree volume. Varied effects due to growth limiting factors like frost and competing vegetation affected results on a few plots. Recommendations include leaving or enhancing organic matter onsite for soil carbon, nutrients, forest health and site productivity. Further analysis with the larger LTSP dataset and ongoing monitoring is encouraged to determine if the results persist in the long-term and to better understand the significant covariate relationships.

Evidence of Coevolution Between Cronartium harknessii Lineages and Their Corresponding Hosts, Lodgepole Pine and Jack Pine.

Variation in rate of infection and susceptibility of Pinus spp. to the fungus Cronartium harknessii (syn. Endocronartium harknessii), the causative agent of western gall rust, has been well documented. To test the hypothesis that there is a coevolutionary relationship between C. harknessii and its hosts, we examined genetic structure and virulence of C. harknessii associated with lodgepole pine (P. contorta var. latifolia), jack pine (P. banksiana), and their hybrids. A secondary objective was to improve assessment and diagnosis of infection in hosts. Using 18 microsatellites, we assessed genetic structure of C. harknessii from 90 sites within the ranges of lodgepole pine and jack pine. We identified two lineages (East and West, FST = 0.677) associated with host genetic structure (r = 0.81, P = 0.001), with East comprising three sublineages. In parallel, we conducted a factorial experiment in which lodgepole pine, jack pine, and hybrid seedlings were inoculated with spores from the two primary genetic lineages. With this experiment, we refined the phenotypic categories associated with infection and demonstrated that stem width can be used as a quantitative measure of host response to infection. Overall, each host responded differentially to the fungal lineages, with jack pine exhibiting more resiliency to infection than lodgepole pine and hybrids exhibiting intermediate resiliency. Taken together, the shared genetic structure between fungus and host species, and the differential interaction of the fungal species with the hosts, supports a coevolutionary relationship between host and pathogen.[Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Cumulative Impact of Biotic and Abiotic Damage Agents on Lodgepole Pine Tree Form and Stand Structure in Southern British Columbia

Not all pests kill trees or compromise final tree form; however, the cumulative effect of one or more damage agents over time can significantly limit final expectations at harvest, severely reducing or compromising wood quality and timber supply expectations going forward. This study highlights the effects of damage agents on young lodgepole pine insouthern British Columbia during the formative years of stand development. Over 4,300ntrees were monitored for up to three decades with over 40 damage agents recorded, causing significant repercussions on stocking, health, and form of potential crop trees. By the final assessment, density of potential crop trees had declined dramatically, with 84% affectedby one or more pests, and 63% of natural ingress dead. Most natural ingress was severely suppressed; thus, it is unlikely to fill in stand gaps caused by mortality and damage agents affecting larger potential crop trees. Lodgepole pine terminal weevil and western gall rust were the predominant damage agents influencing form and quality of potential crop trees. Lodgepole pine terminal weevil attacked up to 73% of pine and over 24% suffered multiple attacks. Results from this study emphasize the need for more short- and long-term monitoring of young stands to inform the development of forest policy and promote healthy, resilient new forests. KEYWORDS: lodgepole pine, damage agents, lodgepole pine terminal weevil, western gall rust, Southern British Columbia

Improving lodgepole pine genomic evaluation using spatial correlation structure and SNP selection with single-step GBLUP.

Modeling environmental spatial heterogeneity can improve the efficiency of forest tree genomic evaluation. Furthermore, genotyping costs can be lowered by reducing the number of markers needed. We investigated the impact on variance components, breeding value accuracy, and bias of two phenotypic data adjustments (experimental design and autoregressive spatial models), and a relationship matrix calculated from a subset of markers selected for their ability to infer ancestry. Using a multiple-trait multiple-site single-step Genomic Best Linear Unbiased Prediction (ssGBLUP) approach, four scenarios (2 phenotype adjustments × 2 marker sets) were applied to diameter at breast height (DBH), height (HT), and resistance to western gall rust (WGR) in four open-pollinated progeny trials of lodgepole pine, with 1490 (out of 11,188) trees genotyped with 25,099 SNPs. As a control, we fitted the conventional ABLUP model using pedigree information. The highest heritability estimates were achieved for the ABLUP followed closely by the ssGBLUP with the full marker set and using the spatial phenotype adjustments. The highest predictive ability was obtained by using a reduced marker subset (8000 SNPs) when either the spatial (DBH: 0.429, and WGR: 0.513) or design (HT: 0.467) phenotype corrections were used. No significant difference was detected in prediction bias among the six fitted models, and all values were close to 1 (0.918-1.014). Results demonstrated that selecting informative markers, such as those capturing ancestry, can improve the predictive ability. The use of spatial correlation structure increased traits' heritability and reduced prediction bias, while increases in predictive ability were trait-dependent.

Tree Mortality following Thinning and Prescribed Burning in Central Oregon, U.S.

We examined causes and levels of tree mortality one year after thinning and prescribed burning was completed in ponderosa pine (Pinus ponderosa Dougl. ex Laws.) forests at Pringle Falls Experimental Forest, Oregon, U.S. Four blocks of five experimental units (N = 20) were established. One of each of five treatments was assigned to each experimental unit in each block. Treatments included thinning from below to the upper management zone (UMZ) for the dominant plant association based on stand density index values for ponderosa pine followed by mastication and prescribed burning: (1) 50% UMZ (low density stand), (2) 75% UMZ (medium density stand), (3) 75% UMZ Gap, which involved a regeneration cut, (4) 100% UMZ (high density stand), and (5) an untreated control (high density stand). Experimental units were thinned in 2011 (block 4), 2012 (block 2), and 2013 (blocks 1 and 3); masticated within one year; and prescribed burned two years after thinning (2013–2015). A total of 395,053 trees was inventoried, of which 1.1% (4436) died. Significantly higher levels of tree mortality occurred on 100 UMZ (3.1%) than the untreated control (0.05%). Mortality was attributed to prescribed fire (2706), several species of bark beetles (Coleoptera: Curculionidae) (1592), unknown factors (136), windfall (1 tree), and western gall rust (1 tree). Among bark beetles, tree mortality was attributed to western pine beetle (Dendroctonus brevicomis LeConte) (881 trees), pine engraver (Ips pini (Say)) (385 trees), fir engraver (Scolytus ventralis LeConte) (304 trees), mountain pine beetle (D. ponderosae Hopkins) (20 trees), Ips emarginatus (LeConte) (1 tree), and Pityogenes spp. (1 tree).

Comparative genomics of the chitinase gene family in lodgepole and jack pines: contrasting responses to biotic threats and landscape level investigation of genetic differentiation

The sister species, lodgepole pine (Pinus contorta var. latifolia Engelm.) and jack pine (Pinus banksiana Lamb), face pressures from a multitude of biotic agents, including mountain pine beetle (Dendroctonus ponderosae Hopkins, 1902) and their pathogenic fungal associates (e.g., Grosmannia clavigera (Rob.-Jeffr. &amp; R.W. Davidson) Zipfel, Z.W. de Beer &amp; M.J. Wingf.), mistletoe (Arceuthobium americanum Nutt. ex A.Gray), and the pathogen causing western gall rust (Cronartium harknessii E. Meinecke). Here, we report new stem tissue transcriptome resources developed for lodgepole and jack pines subjected to these biotic stresses. The annotated transcriptomes were compared to determine species-specific responses to the necrotrophic G. clavigera and the biotrophic Cronartium harknessii. We focused on chitinases, a family that includes members with well-documented roles in defense. Putative chitinase family members were identified via annotation, sequence similarity to reference chitinase genes, phylogenetic analyses, and in silico motif characterization. RNA-Seq revealed marked differences in the responses of lodgepole and jack pine chitinases to G. clavigera and Cronartium harknessii. The potential for adaptive variation in chitinases was investigated by assessing the level of genetic differentiation between and within lodgepole and jack pines using single nucleotide polymorphisms within chitinases. These analyses illustrate the potential of combining transcriptomic and genotyping resources to investigate genotype–phenotype correlations for non-model species.

Long-Term Effects of Lodgepole Pine Terminal Weevil and Other Pests on Tree Form and Stand Structure in a Young Lodgepole Pine Stand in Southern British Columbia

This study describes the impacts of 25 damaging agents recorded on young lodgepole pine trees over a 30-year period in a study plot in southern British Columbia. During the study, density fluctuated due to infill and mortality. Of the 1,295 stems per hectare present at the outset of the study, 37% of lodgepole pine died and only 24% of the trees remained pest-free by the final assessment. Pest-free trees were predominantly small and suppressed infill, leaving just over 1,000 stems per hectare of crop trees. Lodgepole pine terminal weevil affected over 38% of pine, with up to six attacks per tree. Fifty percent of lodgepole pine in the study was infected or killed by one or more hard pine stem rusts, with comandra blister rust and western gall rust being the predominant diseases, affecting 32% and 19% of the pine, respectively. Until age 20, 70% of weevil attacks caused major defects. From age 20–40 years, 50% of attacks caused major defects, often forks or multiple tops (stagheads). Defects were more severe when trees were attacked early in stand development. There was a strong correlation between the number of weevil attacks per tree and tree form, and the number of pests recorded per tree and tree form. Two or more pests per tree caused tree form to shift from good to moderate or poor.

A module to simulate the impact of western gall rust (Cronartium harknessii) on merchantable volume and lumber yields for lodgepole pine (Pinus contorta var. latifolia) stands in British Columbia

Western gall rust (Cronartium harknessii (J.P. Moore) E. Meinecke) is a pathogen that affects lodgepole pine (Pinus contorta Douglas ex Loudon var. latifolia Engelm. ex S. Watson) and has the potential to reduce lumber product yields derived from stands managed for the commercial production of timber. A dataset containing repeated measurements from 7775 trees located within the province of British Columbia, Canada, was used to develop equations that predict annual rates of stem infection, post-infection mortality, and the location of large stem galls. Results showed that annual rates of infection peaked between 3 and 5 years following stand establishment. Few new infections were predicted to occur beyond the stand age of 15 years. For an individual tree, the probability of first infection increased as its height increased relative to stand top height. The rate of mortality increased with the number of stem infections and was highest among trees infected within the first 3 years following planting. Mortality rates decreased thereafter, with many trees likely to survive to rotation. The equations predicting rust incidence and mortality were added to the Tree and Stand Simulator (TASS), an individual-tree growth model used within the province. A final equation predicting the location of large galls was added and allows TASS to account for losses due to the removal of stem defects during lumber manufacturing.

Pest categorisation of Cronartium harknessii, Cronartium kurilense and Cronartium sahoanum.

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of Cronartium harknessii, Cronartium kurilense and Cronartium sahoanum, which are well‐defined and distinguishable tree fungal pathogens of the family Cronartiaceae. In 2018, these species were moved from the genus Endocronartium to the genus Cronartium. These pathogens are not known to be present in the EU and are regulated in Council Directive 2000/29/EC (Annex IAI) (as non‐European Endocronartium spp.) as harmful organisms whose introduction into the EU is banned. These three fungi are autoecious rusts completing their life cycle on Pinus spp. C. harknessii is known as the western gall rust or pine‐pine gall rust in North America (Canada, the USA and Mexico). C. kurilense and C. sahoanum are reported from Russia (North Kuril Islands) and Japan. The pathogens could enter the EU via host plants for planting and cut branches. The pathogens could establish in the EU, as climatic conditions are favourable and Pinus spp. are common. The pathogens would be able to spread following establishment by movement of host plants for planting and cut branches, as well as natural spread. Should these pathogens be introduced in the EU, impacts can be expected on pine forests, plantations, ornamental trees and nurseries. The pathogens cause formation of stem galls, which kill young trees and result in stem defect in older trees. The main knowledge gap concerns the limited available information on C. kurilense and C. sahoanum compared to C. harknessii. The criteria assessed by the Panel for consideration of C. harknessii, C. kurilense and C. sahoanum as potential quarantine pests are met, whilst, for regulated non‐quarantine pests, the criterion on the pest presence in the EU is not met.

Using excess greenness and green chromatic coordinate colour indices from aerial images to assess lodgepole pine vigour, mortality and disease occurrence

Here, we test the feasibility of using two colour indices to assess differences in stand-health metrics in 54 plots of lodgepole pine in British Columbia, Canada. Colour indices of excess greenness (EG) and green chromatic coordinate (GCC) were calculated over two spatial scales from colour images captured from a Cessna T210 flying at 600m above ground level. EG and GCC were then compared to five ground-based metrics of stand health: vigour, mortality, foliar disease occurrence, western gall rust occurrence, and root disease symptoms. Colour indices, calculated at both tree and plot scales, significantly related to the ground-based metrics of stand health, except western gall rust occurrence. These relationships were influenced by canopy closure, but were unaffected by foliar nitrogen concentration. Using linear regression models, ground-based stand-health metrics accounted for 36.5–60.9% of the variability in colour indices. Within research projects, EG and GCC values could be used to set thresholds below which ground-checks of stand health would be warranted.

Complex Interactions Among Agents Affect Shore Pine Health in Southeast Alaska

Abstract Permanent plots are essential for tracking long-term forest change and have become more important given the projected increase in widespread tree mortality and forest health issues associated with climate change, invasive pests, altered disturbance regimes, and other novel stressors. Inventory and monitoring plots can reveal otherwise undetected loss of tree biomass, initiating targeted biological investigations. Shore pine is an understudied subspecies of lodgepole pine that reaches its northern extent in southeast Alaska. U.S. Forest Service Forest Inventory Analysis data detected a significant loss of live shore pine biomass in Alaska, with greater losses among larger trees and no known cause. We installed 46 permanent plots to monitor shore pine health and survival. Mortality was higher in shore pine (13%) than most associated conifers, and 43% of pines > 40 cm diameter at breast height were dead. Western gall rust, bole wounds, and Dothistroma needle blight were the most common forms of dama...

Genetic resistance to western gall rust in jack pine and its relationship with tree height growth

Developing resistance to western gall rust (WGR) is important for maintaining healthy and productive jack pine plantations. In this study, we estimated genetic parameters of resistance to WGR and its relationship with tree height growth, based on data collected from three second-generation full-sib progeny testing series of jack pine planted in New Brunswick, Canada. Results indicated that (i) resistance to WGR in jack pine was controlled by both additive and dominance gene effects, with the latter playing a greater role; (ii) narrow-sense heritability estimates for resistance to WGR were low (mean = 0.05; series range = 0.00∼0.09), and broad-sense heritability estimates were moderate on an individual-tree basis (mean = 0.53) and considerably higher on the full-sib family mean basis (mean = 0.87); (iii) additive genetic correlation between tree height growth and WGR incidence was low (≤0.06) in two series and only slightly higher and favorable (–0.19) in one series, suggesting that selection on growth traits would not negatively affect WGR resistance; and (iv) mid-parental additive genetic and dominance effects on WGR were empirically correlated (&gt;0.65), indicating that incorporating breeding for WGR resistance into current jack pine tree improvement programs with a seed orchard approach could partly capture the benefit from dominance effects. Although genetic gains in WGR resistance could be realized through various breeding and deployment schemes, it appeared that rapid improvement could be achieved through backward selection on full-sib family means.

Hard pine stem rusts on lodgepole pine at a site-preparation study in sub-boreal British Columbia: effects over 24 years

Site preparation can improve lodgepole pine (Pinus contorta var. latifolia Engelm. ex S. Watson) survival and growth; however, we lack information regarding possible interactions between treatment effects and the impacts of western gall rust (Endocronartium harknessii (J.P. Moore) Y. Hirats.) and comandra blister rust (Cronartium comandrae Peck). Mechanical and burning techniques examined over 24 years at a sub-boreal British Columbia site did not significantly increase rust infection rates or characteristics relative to an untreated control. Most infection occurred before age 10 years and at heights &lt;2 m. By age 24 years, 22% and 10% of pine had sustained at least one western gall rust or comandra blister rust stem infection, respectively, but only 4% of western gall rust infected trees were dead, compared with 60% of comandra blister rust infected trees. Exploratory regression analysis of the relationship between tree volume and percent stem encirclement and infection height suggested that volume of 24-year-old pine infected with western gall rust averaged 8% less than the corresponding volume of uninfected trees. Over 24 years, estimated stand-level, rust-related volume loss was 8.4%, with the majority due to mortality from comandra blister rust. One-fifth of estimated volume loss was provisionally attributed to growth reductions among live western gall rust infected pine.

Evidence against planting lodgepole pine monocultures in the cedar-hemlock forests of southeastern British Columbia

Single-species planting of lodgepole pine (Pinus contorta var. latifolia) following clear-cut logging or wildfire has been common throughout interior British Columbia, Canada, but health problems with the species have been documented as it grows beyond the juvenile stage. We examined damage and stocking in twenty-seven 15to 30-yearold lodgepole pine plantations that were previously declared free growing in the highly productive cedar–hemlock forests in southeastern British Columbia, where lodgepole pine is absent from many primary forests. In order to be free growing, stands must meet minimum tree density, height, damage and brush competition criteria as legislated by the Provincial government. Overall, 44 per cent of lodgepole pine trees had unacceptable damage (causing them to be rejected as crop trees), and as a direct result, one-third of the plantations were no longer defined as free growing because there were insufficient crop trees remaining. Natural regeneration of other tree species partially compensated for the unhealthy pine. Logistic regression and odds ratio analysis associated increasing risk of damage from western gall rust with increasing soil moisture, more northerly aspects and mechanical site preparation, and decreasing risk with pre-commercial thinning treatment. Risk of damage from snow and ice was associated with increasing mean annual precipitation, decreasing longitude and broadcast burning. Risk of bear damage was associated with increasing soil moisture, pre-commercial thinning treatment and broadcast burning. Based on our results, we recommend that single-species planting of lodgepole pine be curtailed in the Interior Cedar–Hemlock zone in southeastern British Columbia.

Management strategies for pitch canker infected Año Nuevo stands of Monterey pine

The future resilience of Pinus radiata D. Don (Monterey pine) is dependent upon the development of a silviculture program inclusive of either preventative or management techniques for the potentially fatal pitch canker disease (Fusarium circinatum Nirenberg and O’Donnell (=F.subglutinans (Wollenw and Reinking) Nelson et al. f. sp. Pini). As an ecologically and commercially valued species of limited natural range, a number of factors threaten to reduce the Monterey pine gene pool potentially impacting its long-term resilience. This study evaluated the effectiveness of uneven-aged forest management for regeneration success applied in the native, pitch canker infested Año Nuevo stands at Swanton Pacific Ranch in Davenport, California. The impact of gap size (0.20-ha (0.50 acre), 0.10-ha (0.25 acre), and 0.05-ha (0.125 acre)), site-preparation treatment (pile and burn, lop and scatter), and parent tree (13 local seed sources) on seedling survival and growth response (height, diameter) were addressed. Pitch canker symptoms were quantified to conclude if there is indeed a range of expressed resistance according to parent tree. The above independent variables were also examined for being correlated with branch tip incidence of pitch canker and western gall rust disease.A generalized linear mixed model estimated that the odds of seedling survival varied by site treatment and parent, but not by gap size. Pile and burn sites were estimated to have higher survival rates than lop and scatter sites. Linear mixed models estimated that gap size was associated with average seedling growth, both in terms of height and diameter. Parent and site treatment were not found to be significantly associated with the growth outcome measures. The 0.05-ha sites had smaller average height and diameter than the 0.20-ha sites. The 0.10-ha site also had smaller average diameter than the 0.20-ha sites. The presence of pitch canker disease on branch tips was found to be correlated only with gap size, with 0.10-ha sites having higher pitch canker incidence than the 0.05- and 0.20-ha sites. Though gall rust presence on branch tips was not associated with any of the hypothesized independent variables, there was an association between gall rust presence and pitch canker presence on branch tips. Site treatment and parent tree were associated with seedling survival, while gap size was found to be associated with seedling growth and disease resistance.

Age and Structure of Mature Knobcone Pine Forests in the Northern California Coast Range, USA

AbstractAn understanding of current structural conditions and disturbance history is a requisite for optimal management of forest ecosystems, especially for serotinous species such as knobcone pine (Pinus attenuataLemmon). Knobcone pine is widely distributed in California, yet little is known regarding age and forest structure patterns. In this study, we quantify forest conditions of 21 mature knobcone pine stands in the northern Mayacmas Mountains, north Coast Range, California, USA. Characterized by complex terrain, knobcone pine forests occur in small patches interspersed with chaparral and mixed evergreen forests. Stands displayed unimodal, bimodal, and diffuse age distributions with predominant stand ages ranging from 42 yr to 70 yr, although trees ranged from 17 yr to 98 yr old. Knobcone pine stands appear to have been maintained by stand replacing fires. However, stands with uneven-aged structures were produced through the persistence of residual trees and low intensity fires that created secondary cohorts. Stands varied in density, ranging from 503 stems ha−1to 2986 stems ha−1, with snags comprising 12 % to 40 % of total density. Wildfires that occurred from the 1930s to the 1960s, in addition to a large wildfire in 1981, created a heterogeneous landscape of knobcone pine forests. Older stands have lower canopy cover, high snag densities, and many trees with evidence of western gall rust (Peridermium harknessii) infections—signs that they are approaching their expected life spans. Risks and constraints associated with using stand replacing prescribed fire pose a challenge for managers of knobcone pine forests, and research may be needed to explore feasible treatment alternatives.

Effect of galls induced by Endocronartium harknessii on stem hydraulic conductivity and growth of lodgepole pine

SummaryTo test the hypothesis that galls resulting from infection by western gall rust [Endocronartium harknessii (J. P. Moore) Y. Hiratsuka] on lodgepole pine [Pinus contorta Dougl. ex Loud.] create hydraulic constrictions that reduce tree growth, the hydraulic conductivity (Kψ; m2 s−1 Pa−1), leaf area (AL) and sapwood area (AS) were measured on 6‐ to 15‐year‐old trees having galls encircling 0–100% of the stem. Increases in gall encirclement were accompanied by decreases in Kψ, foliar nitrogen concentration, AL and AS, although the AL:AS ratio remained constant. Dye flow patterns through galled stem sections indicated that water moved primarily through the non‐galled portions of the stem. In a second field study, xylem and phloem wounds were applied to 13‐year‐old galled and non‐galled trees on either the galled or non‐galled side of the tree. Although both galls and xylem wounds reduced Kψ, radial and height growth were unaffected. In aggregate the two experiments showed that although trees are quite tolerant to small galls and short term reductions in Kψ, the disruption of water movement by larger galls may be sufficient to initiate a chain of events leading to tree death, especially in very dense stands with high levels of intraspecific competition.

Lodgepole pine provenances differ in chemical defense capacities against foliage and stem diseases

Maximization of lodgepole pine ( Pinus contorta Douglas ex Louden var. latifolia Engelm. ex S. Watson) growth in a future climate with increased pest activity requires an understanding of the natural variability of quantitative resistance to disease. Foliar and bark secondary metabolites from different lodgepole pine provenances (populations) were quantified and correlated with severity of foliar diseases caused by Lophodermella spp. ( Lophodermella concolor (Dearn.) Darker or Lophodermella montivaga Petre.) or Elytroderma deformans (Wier) Darker and bark diseases caused by Elytroderma or Endocronartium harknessii (J.P. Moore) Y. Hiratsuka. Greater foliar concentrations of lignin, tannins, and some phenolics were associated with increased resistance to single or multiple foliar pathogens. Bark secondary metabolites levels were generally unassociated with resistance to bark diseases. Provenances appearing to originate in ecosystems where lodgepole pine are not the dominant species generally were more susceptible to foliar diseases and had less foliar defense-associated compounds than trees from areas where pines were the dominant species, yet clear trends proved to be elusive. Regardless, pine provenances with greater foliar levels of identified defense-associated compounds should be preferred seed sources for replanting forests in areas in which foliar disease is expected to be increasingly prevalent.

Investigating the influence of climate, site, location, and treatment factors on damage to young lodgepole pine in southern British Columbia

Lodgepole pine ( Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) has been extensively planted throughout interior British Columbia, and as a result may be particularly susceptible to climate-induced changes in the range and severity of common damaging agents. We quantified the presence of 14 damaging agents in sixty-six 15- to 30-year-old pine stands. Hard pine stem rusts, primarily western gall rust, were present on every site. We used logistic regression to predict individual agent presence from climatic, location, site, and treatment factors and calculated odds ratios to evaluate whether risk to lodgepole pine increases or decreases as these factors change. Risk of damage from serious agents (stem disease, root disease, and mountain pine beetle) increased with increasing latitude; however, in several of these models, risk also increased as temperature of the coldest month got warmer. We also found evidence that increasing risk of damage from agents that are currently less serious (sequoia pitch moth, pine needle cast, and pine terminal weevil) was associated with warming and (or) increasingly dry climatic conditions. Given the predominance of lodgepole pine in northerly ecosystems and the prediction that climate change effects will increase with latitude, our results suggest the need to consider potential increases in damage from diseases and insects during silviculture planning and timber supply prediction.