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Abstract The compensatory reserve index (CRI), derived from machine learning algorithms from peripherally obtained photoplethysmography signals, provides a non‐invasive assessment of cardiovascular stability, that may be useful clinically. Briefly, the CRI device provides a value between 0 and 1, with 1 reflecting full compensable capabilities and 0 reflecting little to no compensable capabilities. However, the CRI algorithm was developed in younger to middle aged adults, such that it is unknown if older age modulates CRI responses to cardiovascular challenges. In young and older subjects, we compared CRI responses to normothermic and hyperthermic progressive lower body negative pressure (LBNP), and volume loading with saline infusion. Eleven younger (20–36 years) and 10 older (61–75 years) healthy participants underwent (1) graded normothermic LBNP up to 30 mmHg, (2) graded hyperthermic (1.5°C increase in blood temperature) LBNP up to 30 mmHg, and (3) infusion of 15 mL/kg saline (volume loading) with hyperthermia maintained. CRI was obtained throughout each procedure. CRI at 30 mmHg LBNP was 0.18 and 0.24 units greater in the older group during normothermic and hyperthermic LBNP, respectively. However, CRI was not different between age groups at any other LBNP stage, nor did CRI change with volume loading regardless of age. In response to passive hyperthermia alone, regression analyses showed that heart rate was the strongest predictor of CRI. Blood temperature, rate pressure product, and stroke volume were also predictive of CRI but to a lesser extent. In conclusion, age attenuates the reduction in CRI during progressive normothermic and hyperthermic LBNP, but only at 30 mmHg. Second, the CRI was unchanged during volume loading in all subjects. Future studies should determine whether the age differences in CRI reflect age differences in LBNP tolerance.

Abstract Planet Earth is warming at an unprecedented rate and our future is now assured to be shaped by the consequences of more frequent hot days and extreme heat. Humans will need to adapt both behaviorally and physiologically to thrive in a hotter climate. From a physiological perspective, countless studies have shown that human heat acclimation increases thermoeffector output (i.e., sweating and skin blood flow) and lowers cardiovascular strain (i.e., heart rate) during heat stress. However, the mechanisms mediating these adaptations remain understudied. Furthermore, several possible benefits of heat acclimation for other systems and functions involved in maintaining health and performance during heat stress remain to be elucidated. This review summarizes recent advances in human heat acclimation, with emphasis on recent studies that (1) advanced our understanding of the mechanisms mediating improved thermoeffector output and (2) investigated adaptations that go beyond those classically associated with heat acclimation. We highlight that these studies have contributed to a better understanding of the integrated physiological responses underlying human heat acclimation while leaving key unanswered questions that will need to be addressed in the future.

Abstract Hotter climates have important impacts on human health and performance. Yet, the cellular and molecular responses involved in human heat stress and acclimation remain understudied. This dataset includes physiological measurements and the plasma concentration of 2,938 proteins collected from 10 healthy adults, before and during passive heat stress that was performed both prior to and after a 7-day heat acclimation protocol. Physiological measurements included body temperatures, sweat rate, cutaneous vascular conductance, blood pressure, and skin sympathetic nerve activity. The proteomic dataset was generated using the Olink Explore 3072 assay, enabling a high-multiplex antibody-based assessment of protein changes based on proximity extension assay technology. The data need to be interpreted in the context of the moderate level of body hyperthermia attained and the specific demographic of young, healthy adults. We have made this dataset publicly available to facilitate research into the cellular and molecular mechanisms involved in human heat stress and acclimation, crucial for addressing the health and performance challenges posed by rising temperatures.

Introduction Despite proven programmes, implementing lifestyle interventions for pre-diabetes and type 2 diabetes is challenging. Cardiac rehabilitation, provide a valuable opportunity to promote the adoption of healthy lifestyle behaviours for patients with atherosclerotic cardiovascular disease (ASCVD). However, only a limited number of studies have explored the potential for reversing the underlying causes of ASCVD in this setting.Objectives The DIABEPIC1 study is an ongoing single-arm lifestyle clinical trial to assess the feasibility of an upgraded 6-month intensive cardiac rehabilitation programme combining an innovative diet assignment with exercise training to reverse newly onset pre-diabetes (glycated haemoglobin 5.7%–6.4%) to normal glucose concentrations in patients with coronary heart disease.Methods and analysis 36 patients referred from the Montreal Heart Institute for cardiac rehabilitation, aged ≥40 years with a recent diagnosis of pre-diabetes in the last 6 months, will be offered to participate in the upgraded programme. Interventions will include four sessions of nutritional counselling on ultra-processed foods intake reduction and a moderate-carbohydrate (

Abstract The aim of this study was to gain a better understanding of the acute effect of heat exposure on brachial artery flow‐mediated dilatation (FMD) and postocclusion reactive hyperaemia (PORH) by: characterizing the time course of changes post‐heating; comparing forearm and whole‐body heating; determining the impact of forearm heating during whole‐body heating; and comparing males and females. Twenty adults (11 males and nine females; 28 ± 6 years of age) underwent two forearm [10 min electric blanket (EB) or 30 min hot water immersion (WI)] and two whole‐body [60 min water‐perfused suit with forearm covered (WBH‐C) or uncovered (WBH‐U)] heating modalities. The FMD and PORH were measured before and after (≤5, 30, 60, 90 and 120 min) heating. The FMD increased from baseline 30 min after EB, and 30 and 90 min after WI. In contrast, FMD decreased from baseline immediately after both WBH modalities. Peak PORH increased immediately after WI and both WBH modalities. Total PORH did not differ after WI, whereas it decreased immediately after both WBH modalities. Covering the forearm during WBH did not alter acute changes in FMD or PORH. Changes in FMD and PORH did not differ statistically between males and females during each heating modality, although the observed differences could not always be considered equivalent. These results demonstrate that the acute effect of heat exposure on brachial artery FMD and PORH is: (1) transient and short lasting; (2) different between forearm heating and WBH; (3) unaffected by direct forearm heating during WBH; and (4) not different but not always equivalent between males and females.

Abstract The primary aim of this investigation was to determine the individual contribution of the cutaneous and skeletal muscle circulations to the cold‐induced pressor response. To address this, we examined local vascular resistances in the cutaneous and skeletal muscle of the arm and leg. Thirty‐four healthy individuals underwent three different protocols, whereby cold air to clamp skin temperature (27°C) was passed over (1) the whole‐body, (2) the whole‐body, but with the forearm pre‐cooled to clamp cutaneous vascular resistance, and (3) the face. Cold exposure applied to the whole body or isolated to the face increased mean arterial pressure (all, P

Background: The intensity of inflammatory response triggered by cardiopulmonary bypass (CPB) during cardiac surgery has been associated with adverse outcomes. Neutrophils might contribute to organ injury through the liberation of DNA histone-based structures named “neutrophil extracellular traps” (NETs). Our objective was to assess circulating NETs levels before and after cardiac surgery in low-risk and high-risk patients. Methods: This prospective cohort study included 2 groups of patients undergoing elective cardiac surgery with the use of CPB. The first group consisted of low-risk patients (European System for Cardiac Operative Risk Evaluation II ≤ 1%), and the second group included high-risk patients (European System for Cardiac Operative Risk Evaluation II ≥ 5%). Blood samples were drawn pre-CPB and 3 hours post-CPB separation. Measurements of circulating NETs, interleukin-6, C-reactive protein, myeloperoxidase, citrullinated histone 3, and pentraxin-related protein 3 levels were performed at each time point. Results: Twenty-four patients, 12 high-risk and 12 low-risk patients, were included. Circulating NETs measurements changed from a median of 0.054 before CPB to 0.084 at 3 hours post-CPB separation, with a median increase of 0.037 (P < 0.001) per patient. No difference was noted between the high-risk and low-risk groups. A linear relationship was found between the circulating NETs measurements 3 hours post-CPB and CPB duration (ß = 0.047; confidence interval, 0.012-0.081; P = 0.01 R2 = 0.27). A correlation was found between the change in NETs with citrullinated histone 3 and myeloperoxidase levels, but not between NETs and other inflammatory biomarkers. Conclusions: Circulating NETs measurements increases during cardiac surgery with postsurgical levels proportional to CPB duration. The clinical significance of NETs production during cardiac surgery should be further investigated. Résumé: Contexte: L’intensité de la réponse inflammatoire déclenchée par la circulation extracorporelle en cours de chirurgie cardiaque a été associée à des résultats défavorables. Les neutrophiles pourraient contribuer à des lésions organiques par la libération de structures d’ADN lié à des histones appelées « pièges extracellulaires des neutrophiles » (ou NETs, de l’anglais neutrophil extracellular traps). Nous nous sommes donné pour objectif d’évaluer les taux de ces pièges extracellulaires dans la circulation avant et après la chirurgie cardiaque chez des patients exposés à des risques faibles et à des risques élevés. Méthodologie: Cette étude prospective de cohortes a été menée chez deux groupes de patients subissant une chirurgie cardiaque non urgente au cours de laquelle nous avons eu recours à la circulation extracorporelle. Le premier groupe était composé de patients exposés à un faible risque (EuroSCORE II [European System for Cardiac Operative Risk Evaluation II] ≤ 1 %), et le second, de patients exposés à un risque élevé (EuroSCORE II ≥ 5 %). Des échantillons sanguins étaient prélevés avant la mise sous circulation extracorporelle, puis 3 heures après le sevrage de la circulation extracorporelle. Les taux de NETs circulants, d’interleukine-6, de protéine C réactive, de myéloperoxydase, d’histones 3 citrullinées et de protéines apparentées à la pentraxine 3 ont été mesurés à chaque point d’évaluation. Résultats: Les données obtenues chez vingt-quatre patients, 12 dans le groupe à risque élevé et 12 dans le groupe à faible risque, ont été incluses dans l’analyse. Le taux médian de NETs circulants est passé de 0,054 avant la circulation extracorporelle à 0,084 trois heures après le sevrage, avec une augmentation médiane de 0,037 (p < 0,001) par patient. Aucune différence n’a été notée entre les deux groupes. Une relation linéaire a été observée entre la mesure du taux de NETs circulants 3 heures après le sevrage et la durée de la circulation extracorporelle (ß = 0,047; intervalle de confiance : 0,012-0,081; p = 0,01; R2= 0,27). Une corrélation a été notée entre la variation du taux de NETs comportant des histones 3 citrullinés et du taux de myéloperoxydase, mais pas entre le taux de NETs et ceux des autres biomarqueurs de l’inflammation. Conclusions: Le taux de NETs circulants augmente pendant une chirurgie cardiaque, le taux après la chirurgie étant proportionnel à la durée de la circulation extracorporelle. L’importance clinique de la production de NETs pendant la chirurgie cardiaque doit faire l’objet d’études plus approfondies.

Menopause accelerates increases in arterial stiffness and decreases cognitive performances. The objective of this study was to compare cognitive performances in physically active pre- and post-menopausal females and their relationship with arterial stiffness. We performed a cross-sectional comparison of blood pressure, carotid–femoral pulse wave velocity (cf-PWV) and cognitive performances between physically active late pre- and early post-menopausal females. Systolic (post-menopause—pre-menopause: +6 mmHg [95% CI −1; +13], p = 0.27; ŋ2 = 0.04) and diastolic (+6 mmHg [95% CI +2; +11], p = 0.06; ŋ2 = 0.12) blood pressures, and cf-PWV (+0.29 m/s [95% CI −1.03; 1.62], p = 0.48; ŋ2 = 0.02) did not differ between groups. Post-menopausal females performed as well as pre-menopausal females on tests evaluating executive functions, episodic memory and processing speed. Group differences were observed on the computerized working memory task. Post-menopausal females had lower accuracy (p = 0.02; ŋ2 = 0.25) but similar reaction time (p = 0.70; ŋ2 < 0.01). Moreover, this performance was inversely associated with the severity of menopausal symptoms (r = −0.38; p = 0.05). These results suggest that arterial stiffness and performance on tests assessing episodic memory and processing speed and executive functions assessing inhibition and switching abilities did not differ between physically active pre- and post-menopausal females. However, post-menopausal females had lower performance on a challenging condition of a working memory task, and this difference in working memory between groups cannot be explained by increased arterial stiffness.

Abstract The southern range limit of white spruce (Picea glauca) in western Canada is believed to arise from effects of moisture limitation on seedling recruitment. Within stands near white spruce’s range limit, the adverse effects of water limitation on seedling growth and survival may be compounded by competition from neighboring understory plants and trees. To test this hypothesis, we conducted a competition removal experiment on white spruce seedlings in the Cypress Hills, an isolated forest landscape within the Canadian Prairies. We measured the height and diameter at root collar of 371 natural seedlings, and then we manually cleared all vegetation within a 75‐cm radius of 83 seedlings to remove local competition from neighboring plants. In addition to removal of neighboring plants, we excavated a 75‐cm radius trench around another 46 of these seedlings to remove competition for belowground resources. We took hemispherical photographs above each seedling to calculate canopy openness (a proxy for light availability) and re‐measured height and diameter over two years to calculate pre‐ and post‐treatment growth. There was a pronounced difference in precipitation between the two years of our experiment, with spring–summer precipitation 58% higher than average in the pre‐treatment year and 62% lower than average in the post‐treatment year. The diameter growth and survival of seedlings growing without competition showed smaller decreases in the dry post‐treatment year than control seedlings. Removing competition by trenching increased the height growth of seedlings located under an open canopy, but not of those growing under heavy shade. These interactions suggest that white spruce regeneration in water‐limited areas is sensitive to both light availability and local competition. Competition exacerbated drought effects on seedlings, which suggests that frequent droughts could have greater negative impacts on boreal tree seedlings that are growing under a closed canopy.

This study assessed the effects of two vegetation management treatments (black polyethylene mulch and a control treatment) on tree growth, fine root biomass of trees and of competing vegetation, earthworms, and physiochemical soil properties in a 10 year-old agricultural riparian buffer planted in southern Québec (Canada) with five trees species: Populus × canadensis Moench (hybrid poplar), Fraxinus pennsylvanica Marsh. (red or green ash), Quercus macrocarpa Michx. (bur oak), Quercus rubra L. (red oak), and Pinus strobus L. (eastern white pine). Vegetation management treatments had a significant effect on tree growth, fine root biomass, earthworms and on many soil properties. Overall, the use of plastic mulch increased tree growth in all species (not to the same extent), but locally decreased soil organic matter, total soil carbon, total soil nitrogen, earthworm biomass and abundance, competing vegetation fine root biomass and the biomass of the total pool of fine roots. Also, more than three times more soil nitrate was measured under mulch despite the higher tree growth. Lower soil phosphorus availability (in some species), base cation saturation and moisture content under the mulch suggested higher uptake of these soil resources to sustain high tree growth. Across treatments and species, significant and strong correlations were observed between total fine root biomass and soil carbon, between competing vegetation fine root biomass and earthworm biomass, and between total soil carbon and earthworm biomass. These highlight the central role of the total pool of fine roots in maintaining or enhancing soil carbon, the importance of understory herbaceous vegetation for earthworm populations and the importance of organic matter as a factor limiting earthworm activity. Species × Treatment interactions were observed on tree growth, fine roots, and earthworms. Pine growth was little enhanced by the mulch and its fine root biomass peaked in the control treatment, suggesting plasticity in allocation to fine roots in response to resource limitations. Pine had similar earthworm biomass across both vegetation management treatments, with two to three times less earthworm biomass than other tree species observed in control plots, reflecting its low needle litter quality. Only poplar and ash had higher tree fine root biomass under the mulch. Red oak was the species the most negatively affected by herbaceous competition. In practice, plastic mulch is rarely removed from tree plantation sites. This should change in a context where plastic mulch is increasingly used as an alternative to herbicide, and where riparian agroforestry projects need to meet both timber and non-timber objectives (carbon sequestration in the soil and in tree biomass, N and P storage in woody biomass, soil quality restoration), while minimizing their impacts in terms of nitrate leaching. Identifying alternative mulching materials and strategies that would provide high growth benefits without degrading the soil or water quality is a priority to optimize ecosystem services provision in tree plantations and riparian buffers.

Linear bioenergy buffers planted with fast-growing trees along field edges are increasingly used to address challenges related to sustainable biomass production, climate change mitigation (i.e., carbon storage and microclimate regulation), water quality protection, and forest habitat connectivity in agricultural landscapes. This study assessed: (1) the extent to which 15 m wide hybrid poplar bioenergy buffers (1666 stems/ha) with closed canopy responded to thinning (diamond pattern of tree removal); (2) the regrowth of poplars from cut stumps following gap harvesting; (3) the effects of harvesting treatments on soil microclimate and nutrient availability; and (4) the spatiotemporal pattern of tree growth in unthinned plots. After three post-thinning years, results showed a strong growth response of seven-year-old hybrid poplar trees to thinning (12% increase in diameter and 30% increase in individual stem volume), accompanied by a slight decline in stand productivity. Gap harvesting was not an effective treatment to regenerate the stand from shoots growing from cut stumps because of the high deer browsing. Overall, thinning had marginal effects on soil nutrients and microclimate, compared with gap harvesting, which increased soil temperature, soil moisture, and the availability of several macro and micronutrients. However, harvest effects on soil nutrients were mostly observed during the first postharvest year, with the exception of soil nitrate, which was lowest in the gap treatment during the second postharvest year. Finally, the spatial pattern observed in tree growth between the buffer rows suggests that other more operational thinning patterns (row or corridor thinning) need to be evaluated in linear buffers.

Abstract Regular Finnish sauna bathing is associated with a reduced risk of all‐cause and cardiovascular mortality in middle‐aged and older adults. Potential acute physiological adaptations induced by sauna bathing that underlie this relationship remain to be fully elucidated. The purpose of this study was to determine if typical Finnish sauna sessions acutely improve brachial artery flow‐mediated dilation (FMD) and reactive hyperemia (RH) in healthy middle‐aged and older adults. Using a randomized crossover design, FMD and RH were evaluated in 21 healthy adults (66 ± 6 years, 10 men/11 women) before and after each of the following conditions: (1) 1 × 10 min of Finnish sauna bathing (80.2 ± 3.2°C, 23 ± 2% humidity); (2) 2 × 10 min of sauna bathing separated by 10 min of rest outside the sauna; (3) a time control period (10 min of seated rest outside the sauna). FMD was taken as the peak change from baseline in brachial artery diameter following 5 min of forearm ischemia, whereas RH was quantified as both peak and area‐under‐the‐curve forearm vascular conductance postischemia. FMD was statistically similar pre to post 1 × 10 min (4.69 ± 2.46 to 5.41 ± 2.64%, P = 0.20) and 2 × 10 min of sauna bathing (4.16 ± 1.79 to 4.55 ± 2.14%, P = 0.58). Peak and area‐under‐the‐curve forearm vascular conductance were also similar following both sauna interventions. These results suggest that typical Finnish sauna bathing sessions do not acutely improve brachial artery FMD and RH in healthy middle‐aged and older adults.

Implementing bioenergy buffers on farmland using fast-growing tree species could reduce firewood harvest pressure in woodlots and increase forest connectivity, while improving carbon sequestration, phytoremediation, stream habitats, soil stabilization and hydrological regulation. The objective of the study was to evaluate the natural drying and chemical characteristics of hybrid poplar firewood produced from bioenergy buffers, and to compare these characteristics with those of native species harvested in adjacent woodlots. In Trial A, 110 cm-long unsplit logs (a feedstock for biomass furnaces) were produced to evaluate the effect of log diameter class on firewood quality. In this trial, hybrid poplar firewood characteristics were also compared with Populus tremuloides, Acer rubrum and Fraxinus americana. In Trial B, the effect of hybrid poplar genotype and cover treatment was evaluated on the moisture content of short split logs (40 cm long). Firewood of satisfactory quality was produced on a yearly cycle for short split logs, and on a biannual cycle for long unsplit logs. Covering short split log cords with metal sheeting lowered the final moisture content (from 20.7% to 17.3%) and reduced its variability, while genotype did not significantly affect final moisture content. In Trial A, larger-diameter logs from hybrid poplar had lower element concentrations, but slightly higher moisture content after two years. A two-fold variation in N concentration was observed between diameter classes, suggesting that burning larger poplar logs would minimize atmospheric N pollution. Heating value, carbon and calcium concentrations increased following the seasoning of hybrid poplar firewood. After the first seasoning year outdoors, hybrid poplar had the highest moisture content (33.1%) compared to native species (24.1–29.5%). However, after the second seasoning year in an unheated warehouse, the opposite was observed (14.3% for hybrid poplar vs. 15.0–21.5% for native species). Heating value, carbon and nitrogen concentrations were similar between tree species, while high phosphorus and base cation concentrations characterized hybrid poplar, suggesting higher ash production. Poplar bioenergy buffers could provide a complementary source of firewood for heating in the fall and in the spring, when the heat demand is lower than during cold winter months.

Many small-scale private forest owners increasingly focus their management on amenity functions rather than on wood production functions. This paradigm shift is an opportunity to implement novel forestry management approaches, such as forested land zoning. Forest zoning consists in separating the land base in three zones that have different management objectives: (1) conservation zones; (2) ecosystem management zones; and (3) intensive production zones, which locally increase productivity, as a trade off to increase the land area dedicated to conservation and ecosystem management. We evaluate the ecological feasibility of implementing forest zoning on a private property (216 ha) at St-Benoît-du-Lac, Québec (Canada) characterised by agricultural and forest land uses. As a basis for delineating conservation and ecosystem management zones, historical and contemporary data and facts on forest composition and dynamics were reviewed, followed by a detailed forest vegetation analysis of forest communities. Delineating intensive production zones was straightforward, as fertile agricultural field margins located downslope were used to establish multifunctional hybrid poplar buffers. At St-Benoît-du-Lac, a realistic zoning scenario would consist of (1) conservation zones covering 25% of the forestland (37 ha); (2) ecosystem management zones covering 75% of the forestland (113 ha, including restoration zones on 24 ha); and (3) intensive production zones on 2.8 ha. Based on a yield projection of 13 t/ha/year for hybrid poplars, only 5.6% of agricultural field areas would need to be converted into agroforestry systems to allow for the loss of wood production in a conservation zone of 37 ha of forest. Ecosystem services provision following the implementation of zoning would include increased habitat quality, biodiversity protection and enhancement (by restoration of some tree species), carbon storage, non-point source aquatic pollution control, local biomass production for heating, and increased forest economic value.

The exotic shrub glossy buckthorn (Frangula alnus) is a great concern among forest managers because it invades both open and shaded environments. To evaluate if buckthorn grows similarly across light environments, and if adopting different shapes contributes to an efficient use of light, we compared buckthorns growing in an open field and in the understory of a mature hybrid poplar plantation. For a given age, the relationships describing aboveground biomass of buckthorns in the open field and in the plantation were not significantly different. However, we observed a significant difference between the diameter-height relationships in the two environments. These results suggest a change in buckthorn’s architecture, depending on the light environment in which it grows. Buckthorn adopts either an arborescent shape under a tree canopy, or a shrubby shape in an open field, to optimally capture the light available. This architectural plasticity helps explain a similar invasion success for glossy buckthorn growing in both open and shaded environments, at least up to the canopy closure level of the plantation used for this study.

In this study, we developed clone-specific allometric relationships, with the objective of calculating volume and biomass production after 13 years in 8 poplar plantations, located across an environmental gradient, and composed of 5 unrelated hybrid poplar clones. Allometry was found to be very similar for clones MxB-915311, NxM-3729 and DNxM-915508, all having P. maximoviczii parentage. Clones DxN-3570 and TxD-3230 also had a similar allometry; for a given DBH they have a lower stem volume, stem biomass and branch biomass than P. maximoviczii hybrids. Strong Site × Clone interactions were observed for volume and woody biomass growth, with DxN and TxD hybrids only productive on low elevation fertile sites, whereas P. maximovizcii hybrids were also very productive on higher elevation sites with moderate to high soil fertility. At the site level (5 clones mean), yield reached 27.5 and 22.7 m3/ha/yr. on the two best sites (high fertility and low elevation), confirming the great potential of southern Québec (Canada) for poplar culture. The productivity gap between the most and least productive sites has widened from year 8 to year 13, highlighting the need for high quality abandoned farmland site selection in terms of climate and soil fertility. Although clone selection could optimize yield across the studied environmental gradient, it cannot fully compensate for inadequate site selection.

In the high Andes of Ecuador, although expanding agricultural practices and overgrazing have had negative impacts on soil fertility, few investigations have been conducted to identify which practices are most likely to reduce fertility. Quinoa (Chenopodium quinoa Willd.) was grown in soils from native forests, Nf; pastures, Pa; Eucalyptus globulus Labill. plantations, Eg; and Pinus patula Schlecht. plantations, Pp. A bioassay study was conducted using a randomized block design with control (C), ammonium nitrate (N), triple superphosphate (P), and combined N and P (N+P) fertilizer treatments. On soils from Pp, quinoa mortality was 100% in N, 88% in C, 63% in N+P and 0% in P; P enhanced growth the most; quinoa biomass attained only 0.1 g/pot and had a P content of 0.7 mg/pot. N+P enhanced quinoa growth the most on soils from Nf, Pa and Eg. Here, quinoa biomass (g/pot) averaged 0.1 in C, 0.4 in N, 1.6 in P and 7.2 in N+P; P content (mg/pot) averaged 0.9 in C, 0.6 in N, 12 in P and 38 in N+P. In all soils, PO4- was the principal limiting factor. K deficiencies and Al toxicity probably occurred only in Pp soils. This study suggests that the studied soils cannot support production of quinoa crops without additions of combined fertilizers containing P and K as the principal elements. Pp have the least fertile soils, presumably resulting from a longer history of use after pasturing in addition to the pine effect itself.

Se determinaron las características de crecimiento y de producción iniciales de 6 especies de árboles pioneros y de 9 especies de árboles de estados sucesionales avanzados, todas nativas de la Amazonia ecuatoriana. Las 15 especies fueron plantadas en un dispositivo experimental de bloques aleatorios completos, con 1 testigo y 2 tratamientos con fertilizantes. Los 2 tratamientos no difieren más que en el tiempo de liberación de los nutrientes (70 días y 180 días). El ensayo se situó en el recinto Domono, Macas, Morona Santiago, Ecuador. El crecimiento (altura, diámetro basal) de todas las plantas fueron medidas en 7 ocasiones durante los 6 meses que duró la experiencia. Tres recolecciones parciales de plántulas fueron efectuadas para medir la biomasa. Los resultados indican que Nectandra membranaceae es una de las especies de estados sucesionales avanzados que tienen mucha dificultad de adaptarse al crecimiento en plena luz, ya que su sobrevivencia fue casi nula. Las especies que tienen mejor crecimiento tanto en altura como en diámetro basal y biomasa son las especies pioneras: Heliocarpus americanus, Pollalesta discolor y Erythrina poeppigiana. El análisis de varianza sobre el efecto de los fertilizantes entre las especias, muestra que no hubo efectos significativos sobre el crecimiento en altura, diámetro basal y sobre la biomasa durante los tres primeros meses. Los resultados de este trabajo servirán para seleccionar de manera más acertada las especies pioneras susceptibles de producir lo más rápidamente una cubierta vegetal densa sobre sitios de suelos degradados y a las especies de árboles de estados sucesionales avanzados.

This study took place in southern Québec (Canada) where young stands of white ash and grey birch have been underplanted with white pine, red oak, bitternut hickory and black walnut. The establishment success of white pine and red oak was measured with and without tree shelters (to protect from deer). Ecological factors affecting the height growth of the four species were also measured for protected trees. After 6 years, the survival and total height of unprotected oak was 29% and 44.3 cm vs. 80.5% and 138.5 cm for protected oak. White pine was less affected by browsing (survival of 79.5 and 93.5%; height of 138.5 and 217.9 cm for unprotected vs. protected pine). Height of white pine was higher in the grey birch stands, while height of all hardwoods was higher in the white ash stands, which had better soil drainage, higher fertility, and an understory dominated by Rubus species. Total height of all hardwoods was significantly (p < 0.05) correlated with Rubus cover and with soil fertility. Pine and walnut height were strongly correlated (p < 0.001) to shelterwood structure (canopy openness or total basal area). Pine was less sensitive to variations in shelterwood characteristics, while black walnut showed high sensitivity. This study provides evidence that underplanting is suitable for black walnut assisted migration northward and for bitternut hickory restoration, despite soil conditions that were less favorable than in bottomland habitats mainly supporting these species in eastern Canada. Tree shelters offering protection from deer browsing and species-specific site selection are recommended for underplanting in the southern Québec region.

This study was conducted in a riparian buffer bordering a 1 km segment of a headwater stream crossing a pasture site located in southern Québec (Canada). Three species were planted (black walnut (Juglans nigra L.), bur oak (Quercus macrocarpa Michx.), and eastern white pine (Pinus strobus L.)) with three vegetation treatments (control, herbicide (one application/year for 3 years), and black plastic mulch)). The main objective was to determine to which extent herbicide and plastic mulch, used with species having different ecological characteristics, affect tree growth and soil nutrient status in riparian buffers. Survival was high (>93%) for all species in all treatments. In the control (no vegetation treatment), growth was similar among species. Black walnut had the strongest growth response to herbicide and plastic mulch, and white pine had the weakest. For all species, growth was similar in the herbicide and the plastic mulch treatments. During the fifth growing season, plastic mulch increased soil nitrate and phosphorus compared to the herbicide treatment. In the plastic mulch treatment, higher soil nitrate supply was observed for species that preferentially uptake ammonium (black walnut and white pine). Soil nutrient supplies were similar between the control and herbicide treatments. Despite the more favorable nutritional conditions it provides, permanent black plastic mulching does not provide higher growth benefits after 5 years than a 3-year herbicide treatment. The high soil nitrate supply observed in mulched black walnut and mulched white pine may indicate a limited capacity for nitrate phytoremediation by these species.

In this study, planting density and site effects on hybrid poplar productivity and stem dimensions were evaluated on the mid-term and longer term (8 and 14 years) in southern Québec (Canada). We also evaluated the effects of planting density and site on biomass accumulation and carbon stocks in different plantation compartments, on biomass partitioning at the stand-level, on soil carbon stocks and on soil nutrient supply rate after 14 years. The experimental design consisted of three replicate poplar stands located along a site fertility gradient. Each stand contained six planting densities (ranging from 494 to 1975 trees/ha) and a single genotype (Populus canadensis × P. maximowiczii hybrid). Planting density had a large effect on stem dimensions, but a minor effect on stand volume, aboveground woody biomass production, and aboveground biomass carbon stocks. Site selection and tree survival were more important factors affecting these variables. At all sites, and independent of planting density, mean annual volume increments were also higher after 14 vs. 8 years. On fertile sites, strong correlations between area per tree at planting and biomass partitioning, carbon allocation belowground, soil nutrient supply rate and soil carbon stocks were observed. Aboveground, higher competition for light with increasing planting density resulted in an increase in the stem to branch ratio. Belowground, higher competition for soil resources with increasing planting density reduced soil macronutrient availability (except for potassium), which likely stimulated carbon allocation belowground and carbon accumulation in the soil. Over the longer-term, higher density plantations of poplars could provide greater benefits in terms of carbon storage belowground (soil and roots).

We evaluated the extent to which general or site-specific allometric equations, using diameter at breast height (DBH) as a predictor, are more accurate for estimating stem volume, stem biomass, branch biomass, aboveground woody biomass, and coarse root biomass in 14 year-old plantations of Populus canadensis × Populus maximowiczii (clone DN × M-915508) located along an environmental gradient in southern Québec (eastern Canada). The effect of tree size and site on stem wood basic density, moisture content, and proportion of branch biomass was also evaluated. For stem volume, stem biomass, and aboveground biomass, site-specific and general models had comparable fit and accuracy, but lower Akaike’s Information Criterion (AICc) values were observed for the general models. For the branch and coarse root biomass, higher fit and accuracy and lower AICc values were observed for the site-specific models. Allometric trajectory changes (plastic allometry) across sites were mainly observed for coarse root biomass, branch biomass, and stem volume. On the low fertility site, allocation was increased to coarse roots and decreased to stem volume. Site-specific tradeoffs between tree architecture and stem wood density explained the relatively invariant allometry for the whole aboveground woody biomass across the plantation sites. On the high fertility sites, basic wood density was the lowest and declined as tree DBH increased. At all sites, stem wood moisture content and the proportion of branch biomass increased with DBH. Overall, this study showed that biomass allometry, tree architecture, and biomass quality are a function of both tree size and plantation environment in hybrid poplar. Allometric model selection (site-specific or general) should depend on the objective pursued (evaluation of yield, nutrient budget, carbon stocks).

In temperate agricultural watersheds, the rehabilitation of tree vegetation in degraded riparian zones can provide many ecosystem services. This study evaluated ecosystem service provision potential following the conversion of non-managed herbaceous buffers to hybrid poplar (Populus spp.) buffers in three watersheds (555–771 km2) of southern Québec (Canada), with contrasting agricultural land uses. To extrapolate services at the watershed level, total stream length where hybrid poplars could be established was calculated using GIS data from hydrological and land cover maps. After nine years, a 100% replacement of herbaceous buffers by hybrid poplar buffers along farm streams could lead to the production of 5280–76,151 tons of whole tree (stems + branches) biomass, which could heat 0.5–6.5 ha of greenhouses for nine years, with the potential of displacing 2–29 million litres of fuel oil. Alternatively, the production of 3887–56,135 tons of stem biomass (fuelwood) could heat 55–794 new farmhouses or 40–577 old farmhouses for nine years. Producing fuelwood in buffers rather than in farm woodlots could create forest conservation opportunities on 300–4553 ha. Replacing all herbaceous buffers by poplar buffers could provide potential storage of 2984–42,132 t C, 29–442 t N and 3–56 t P in plant biomass, if woody biomass is not harvested. The greatest potential for services provision was in the Pike River watershed where agriculture is the dominant land use. A review of the potential services of poplar buffers is made, and guidelines for managing services and disservices are provided.

In this field study, we used in vivo NRA activity in hybrid poplar leaves as an indicator of NO3- assimilation for five unrelated hybrid poplar clones. We also examined if leaf NRA of these clones is influenced to the same extent by different levels of soil NO3- availability in two riparian agroforestry systems located in pastures. Leaf NRA differences of more than one order of magnitude were observed between the clones, clearly showing their different abilities to reduce NO3- in leaves. Clone DxN-3570, a P. deltoides x P. nigra hybrid (Aigeiros intrasectional hybrid), always had the highest leaf NRA during the field assays. This clone was also the only one to increase its leaf NRA with increasing NO3- soil availability, which resulted in a significant Site x Clone interaction and a positive relationship between soil NO3- concentration and NRA. All of the four other clones studied had one or both parental species from the Tacamahaca section. They had relatively low leaf NRA and they did not increase their leaf NRA when grown on the NO3- rich site. These results provide evidence that NO3- assimilation in leaves varies widely among hybrid poplars of different parentages, suggesting potential preferences for N forms.