College Mathematics Journal

Supplementation with silicon (Si) and salicylic acid (SA) represents a mitigating solution to water deficit stress in some species. However, studies related to native tree species are scarce. This work evaluated the application of Si and SA doses in Cedrela fissilis Vell. seedlings during and after water restriction (WR). We had 8 treatments: Control; WR and treatments with WR+3 doses of Si (0.42, 0.84 and 1.68 g L-1) and SA (100, 200 and 300 mg L-1). Seedlings were evaluated at two periods: P0, when the photosynthetic rate (A) of seedlings presented values close to zero; and REC, the period in which the previously stressed seedlings reached an A value equal to or greater than control. We observed that seedlings showed reduction in the photochemical and biochemical metabolism of photosynthesis. The leaf application of Si at 0.84 g L-1 ensures metabolic adjustments in water use efficiency.

Climate change induces earlier snowmelt in most regions and extends growing seasons for woody plants. However, there is still limited understanding of how the relative impacts and interactions of light, temperature, and water conditions altered by early snowmelt affect phenological and morphological traits of understory plants. We conducted snow removal experiments in a heavily snow-covered forest. We compared bud break dates and leaf size developments with the effects of snow removal in understory Fagus crenata, Lindera umbellata, and Viburnum furcatum. Snow removal increased temperature and light conditions around buds but decreased the soil moisture during bud break. Removing snow one month before ambient snowmelt accelerated bud break but only by 5.9-11.9 days. Bud break in individuals with snow removal required more thawing degree days around buds than under ambient conditions. Leaf areas of V. furcatum in the snow removal were smaller than those in controls. Summarizing changes in light conditions and leaf area growth, the earlier bud break and leaf growth did not result in greater light capture potential over the spring period in L. umbellata and V. furcatum. Although earlier snowmelt accelerates bud break and leaf expansion in these plants, this may not result in greater carbon accumulation.

Precommercial thinning reduces the density of young, high-density stands, promoting the growth of selected trees. However, existing growth models are calibrated for merchantable-sized trees and do not account for saplings, which limits their ability to simulate the changes induced by precommercial thinning. To address this gap, we developed EsPaCe, a growth simulator tailored to balsam fir stands treated with precommercial thinning. Using data from 329 plots monitored over 20 years post-treatment, we calibrated six interconnected models to predict stem density, species composition, and diameter distribution at 5-year intervals. Simulation results in the balsam fir–paper birch domain show that balsam fir (Abies balsamea (L.) Mill.) remains largely dominant after treatment. Initial stand conditions (density, composition, and quadratic mean diameter) had little effect on the final stand composition. However, later interventions in stands with higher initial quadratic mean diameters appeared to promote tree diameter growth and provide slight control over species composition. Model predictions remained unbiased over 20 years, and simulations extended to 35 years produced plausible outcomes. EsPaCe provides forest managers with a valuable tool for planning silvicultural treatments and integrates seamlessly with long-term growth models for merchantable stands.

Au Canada, plusieurs initiatives autochtones de conservation évoluent vers de véritables partenariats avec des ministères gouvernementaux. Toutefois, il est possible de se questionner sur l’adéquation de ces cadres gouvernementaux avec les besoins et les attentes des Autochtones. Ce projet de recherche porte sur le projet de parc national Assinica initié par la communauté crie d’Oujé-Bougoumou dans la région Eeyou Istchee au Québec. Employant une approche collaborative alliant entretiens semi-dirigés et recherche documentaire, ce projet visait à comprendre dans quelle mesure les aspirations cries sont concrétisées au sein du parc. Les résultats démontrent que ce projet découlant de la Paix des Braves est perçu par les Cris comme un moyen de conserver un mode de vie fondé sur la continuité du lien au territoire et de poursuivre une tradition d’intendance du territoire. Même s’ils ont dû s’allier avec le cadre de parc national, leur vision s’en distingue. Ainsi, des lacunes informationnelles et participatives constatées dans notre recherche suggèrent que la structure de gouvernance des parcs nationaux du Québec ne permet pas pleinement de représenter la vision crie. Cette étude de cas soulève l’importance de revoir les cadres institutionnels applicables aux aires protégées pour qu’ils outrepassent la logique coloniale en vigueur, afin de permettre une participation des communautés autochtones à la hauteur de leurs aspirations.

Anthropogenic disturbances have significantly impacted Alberta's boreal forest, particularly through an extensive network of seismic lines created during oil and gas exploration. These linear disturbances (3-10 m wide) fragment woodland caribou habitat, leading to the loss and degradation of ecosystem services. Natural tree regeneration on seismic lines can help reduce predator presence in caribou habitats; thus, achieving a minimum density of 2000 stems per hectare (sph) with trees at least 3 m tall is considered essential for recovery. However, there are currently no regulatory mandates for seismic line restoration, resulting in limited understanding of forest recovery dynamics, particularly tree regrowth rates. This study aimed to address this gap by comparing the growth of two common conifer species—white spruce and balsam fir—on seismic lines versus adjacent mature forests in northwest Alberta's upland conifer mixedwood stands. Findings indicate that both species may take approximately 30 to 50 years to achieve the 3 m height and 2000 sph target necessary for potential predator-use reduction. While it remains uncertain how this regeneration rate will affect woodland caribou habitat restoration, further investigations through modeling exercises will explore its implications for land use planning.

Plants interact with microorganisms that can cause diseases and reduce crop productivity. The fungal pathogen Melampsora larici-populina (Mlp) causes the leaf rust disease of poplar trees by secreting proteins, termed effectors, into host tissues to promote pathogenesis. In this study, we functionally characterized two homologous Mlp candidate secreted effector proteins (CSEPs), Mlp72983 and Mlp52166. Confocal microscopy experiments revealed that Mlp72983 has cell type-specific differential localization. It accumulates in the guard cells’ chloroplast of the epidermis and in the nucleus of the spongy mesophyll of Arabidopsis thaliana and Populus alba x Populus tremula. Mlp52166 has a nucleocytosolic accumulation in the epidermal layer and has nuclear localization in the mesophyll layer of the two species. Transcriptomic experiments showed that Mlp72983 and Mlp52166 deregulate plant genes, when constitutively expressed in either Arabidopsis or poplar. The two CSEPs deregulate genes that encode histones, hydroxysteroid dehydrogenases and multidrug and toxic compound extrusion proteins, with roles in DNA repair, methylation, and xenobiotic detoxification. Inoculation assays showed that CSEPs overexpression in poplar transgenics did not enhance susceptibility to rust infection. Despite being closely related in sequence identity, Mlp72983 and Mlp52166 have cell-type specific subcellular localization and deregulate mostly unique sets of plant genes.

To understand the effects of water stress on plant growth, nutrients distribution and their stoichiometry in different organs of poplar seedlings, and further explore the validation of growth rate hypothesis (GRH) under water stress treatments. Poplar seedlings (Populus deltoides 'Nanlin 3804') were grown under drought (D), normal water management (CK), low-level flooding (LF), high-level flooding (HF) and high-level flooding followed by flood recovery (FR) treatments in 60 days. Poplar seedling growth, nutrients contents and stoichiometry among different treatments were analyzed. The seedlings had greater relative growth rate of biomass, height and stem-basal diameter (BRGR, HRGR, and SRGR, respectively) under flooding treatments, especially in FR treatment (P < 0.05). Among different organs, stem had the highest BRGR. The N, P and K concentrations were highest in D treatment (P < 0.05). Leaves and stems had greater nutrient concentrations and stoichiometries than roots under different treatments (P < 0.05). The plant stoichiometry were positively correlated with BRGR and HRGR but negatively correlated with SRGR from whole-plant perspective. In organ level, BRGR were negatively correlated with root stoichiometry, but were positively correlated with stem and leaf stoichiometry. Poplar seedlings are suitable for cultivation in relatively moist soil or under short-term periodic flooding conditions. This study provides a scientific basis for the cultivation of high-quality seedlings and the selection of suitable afforestation sites for existing poplar clones.

Trees that form symbioses with nitrogen (N)-fixing bacteria (N-fixers) have long been thought to facilitate neighbors’ growth by providing new N, but some data do not show facilitation. Two hypotheses to explain the lack of facilitation are that (1) N-fixers may decrease the amount of N they fix over time, reducing the N supply to their neighbors and (2) the effect of facilitation might take longer than the 1-5 y interval of most studies. In this study, we tested these hypotheses with the N-fixing tree Robinia pseudoacacia L. and its non-fixing neighbors, using tree ring N isotopes to estimate past N fixation and tree ring width to estimate past size and growth. Where the isotopes allowed a constrained estimate of N fixation, we did not find support for the first hypothesis: 51% of Robinia’s N came from fixation throughout its 60-y lifespan, with little variation across age. In support of the second hypothesis, we found that Robinia enhanced growth of neighboring trees in the future (up to 14 y) more than in the present. This delayed effect matches the expected timing of facilitation by N-fixers and indicates that single-census studies might underestimate the degree to which N-fixers facilitate forest growth.

Spruce budworm (SBW; Choristoneura fumiferana Clem.) outbreaks are an important natural disturbance in North America, killing trees over millions of hectares. We related 11 years of SBW defoliation in 87 plots in Gaspé Peninsula, Québec, to 23 stand, site, and climate variables. Defoliation was consistently ordered among host species: balsam fir > white spruce > black spruce. Within the relatively small 200 km2 study area, cluster analyses resulted in four and 10 clusters for balsam fir cumulative and current defoliation, respectively; variation in cumulative defoliation converged over 11 years. Current defoliation was significantly spatially autocorrelated among plots within stands, but autocorrelation weakened at distances >2500m. Cumulative defoliation was significantly related to insecticide spraying, minimum and maximum summer temperature, and interactions between SBW larvae per branch versus hardwood and white spruce basal area. Tree species, insecticide spraying, and number of defoliating SBW larvae were the main determinants of defoliation. Results showed much higher local spatial variability in current defoliation patterns than previous studies, but over the course of an outbreak, cumulative defoliation patterns converged. Cumulative defoliation patterns similar to these, assigned based on local defoliation severity, can be input into defoliation-based growth models to predict impacts on growth and survival.

The western spruce budworm (Choristoneura freemani; WSB) is the most damaging defoliating insect in the Pacific Northwest. Despite general knowledge about climate influences on WSB, few studies have evaluated how outbreak dynamics are affected by local variability in climate. We used dendrochronological techniques to reconstruct WSB activity in Douglas-firs (Pseudotsuga menziesii) at three low- and three high-elevation sites (representing climate variability) in Idaho, USA. We first tested different thresholds used in an established algorithm for determining WSB activity and found substantial variability in outbreak metrics. We then compared the timing of our reconstructed outbreaks with activity reported by aerial surveys, historical reports, and other reconstructions. Some agreement occurred in non-outbreak periods but significant disagreement existed in the timing of outbreaks. Our assessment of topo-climatic influences on reconstructed WSB activity revealed that defoliation frequency was lower at low-elevation sites, with some inconsistencies depending on metric and threshold choice. Finally, we examined the influence of interannual variability of drought on outbreak initiation, finding no consistent effects. Our results reveal sensitivity to the choice of threshold of the reconstruction algorithm and suggest more investigation is needed to better understand the role of climate given future conditions that will likely be warmer and drier.

Understanding the responses of boreal conifers to climate change are essential for future mitigation and adaptation. In this study, three-year-old seedlings of three Japanese boreal conifers including Sakhalin fir, Yezo spruce, and Sakhalin spruce, naturally found in Hokkaido, Japan, were transplanted in spring 2016 to a cool control and two warm (air-dried interior and humid coastal) sites. We investigated survival, height, and ecophysiological traits based on three parameters: stable carbon isotope discrimination (δ13C), specific leaf area (SLA), and leaf mass specific nitrogen concentration (N) of seedlings during experiments. The survival rates of two spruce species were gradually significantly lower in warm sites, while that of Sakhalin fir did not significantly differ among sites. The relative growth rate (RGR) of two spruce species was significantly lower in the warm-interior site than in both cool control and warm-coastal sites in 2018, although in 2017 the RGR of two spruce species was lower in the warm sites than in cool control site. The less negative δ13C value in 2018 revealed that a vapor pressure deficit might decrease the spruces’ RGR via stoma closure in the warm-interior site. We found that Sakhalin fir would be less sensitive to climate change than two spruce species.

Regeneration failure is occasionally encountered in the boreal mixed forest following clear-cutting, primarily due to competing vegetation and altered soil conditions. This study investigates the effects of applying several soil amendments to improve white spruce plantation growth on poorly regenerated forest sites. Biochar (2.6 Mg ha-1), wood ash (7 Mg ha-1), and manure (105 Mg ha-1) were used alone or in combination, with effects on foliar elements and seedling growth assessed after two growing seasons. While biochar and wood ash have been frequently used, combining them with manure has been limited in boreal forests. Using a randomized complete block design, we measured soil pH, incident light, seedling growth, specific leaf area, and foliar nutrition. Manure significantly increased seedling growth (+37%) compared to treatments without it. It also increased foliar nitrogen (+17%) and phosphorus (+14%). Wood ash increased foliar nitrogen (+7%), phosphorus (+15%), potassium (+19%) and calcium (+29%). Biochar, without wood ash, decreased foliar aluminum by 56%. We conclude that manure represented an important nitrogen and phosphorus source for seedling growth. This research highlights the potential of amendment combinations for improving growth and foliar nutrition of seedlings in poorly regenerated boreal forest ecosystems, for example where herbicide use is prohibited.

The mixed estimator (ME) for annual forest inventory proposed by van Deusen (1999; Can. J. For. Res. 29: 1824–1828) is reformulated as a linear mixed model. This equivalent structure admits an interpretation of the ME as a polynomial regression on year with correlated year-specific random effects. It also uncovers the necessary criterion for maximum likelihood (ML) estimation. The improved performance of the ME under ML estimation is illustrated through simulations and application to inventory data from Montana, USA. Limitations of the ME relating to model-misspecification are also discussed.

Nationwide Forest Inventories (NFIs) collect data on and monitor the trends of forests across the globe. Users of NFI data are increasingly interested in monitoring forest attributes such as biomass at fine geographic and temporal scales, resulting in a need for assessment and development of small area estimation techniques in forest inventory. We implement a small area estimator and parametric bootstrap estimator that account for zero-inflation in biomass data via a two-stage model-based approach and compare the performance to a Horvitz-Thompson estimator, a post-stratified estimator, and to the unit- and area-level empirical best linear unbiased prediction (EBLUP) estimators. We conduct a simulation study in Nevada with data from the United States NFI, the Forest Inventory & Analysis Program, and remote sensing data products. Results show the zero-inflated estimator has the lowest relative bias and the smallest empirical root mean square error. Moreover, the 95% confidence interval coverages of the zero-inflated estimator and the unit-level EBLUP are more accurate than the other two estimators. To further illustrate the practical utility, we employ a data application across the 2019 measurement year in Nevada. We introduce the R package, saeczi, which efficiently implements the zero-inflated estimator and its mean squared error estimator.

Establishing fast-growing plantations is a long-term strategic climate change mitigation option since these plantations may absorb carbon at an accelerated rate and alleviate the pressure on natural forests. In Istanbul, nearly 5% of the forests, totaling 32,603 hectares of natural oak-beech forest ecosystems, were converted to Maritime pine (Pinus pinaster Aiton.) plantations in the 1990s. Maritime pine grows faster than native mixed broadleaf forests but introduces a higher fire risk. The objective of this study was to assess the Greenhouse Gas (GHG) consequences of these conversions by analyzing wildfire emissions and carbon stock changes for a period of 2 decades after conversion. The carbon modeling was done using the CBM-CFS3 model calibrated with ground measurements. The results revealed that the total ecosystem carbon stocks would remain at 97.9 tC/ha (Avoided Species Conversion/ASC scenario) compared to 116.7 tC/ha in the Business as Usual (BAU) scenario. The BAU scenario refers to real life conditions that the species conversions have occurred. The fire emissions had a minor share in total ecosystem GHG balance, because the burnt area rate was low (around 0.1 percent) during the assessment period.