Legacy Forest Harvesting Impacts on Phosphorus Transport Dynamics in Hardwood Dominated Canadian Shield Catchments: Evaluating Changing Source Availability and Source Channel Connectivity
Notice bibliographique
Résumé
Forests are critical to the safe provision of drinking water across the globe and provide over 4.1 trillion USD per year in savings to drinking water treatment costs. These supplies are threatened by climate change-exacerbated landscape disturbances such as wildfire, which can severely impact forest hydrologic and biogeochemical cycles. Potential increases in the transport of sediment and associated nutrients to streams networks are especially concerning because they can propagate downstream and lead to conditions that challenge drinking water treatment operations. Excess phosphorus loading is especially concerning in drinking water sources as it can cause the proliferation of cyanobacteria and other algae that can clog filtration processes or produce toxins that most plants are not equipped to treat, thereby leading to service disruptions or complete outages. Forest harvesting has been proposed as a potential mitigation strategy to lower fuel loads and reduces the risk of catastrophic wildfire, preventing negative impacts on water quality and treatability. However, this strategy needs to be adopted with caution as forest harvesting has the potential to increase phosphorus transport to stream networks, presenting a potential threat to downstream drinking water treatment operations and, thereby exacerbating the problems that they are supposed to mitigate. Accordingly, the objectives of this study were to evaluate the impacts of legacy forest harvesting on the physical processes (i.e., source channel connectivity and source availability) that control phosphorus transport from terrestrial to aquatic environments. This work was conducted on hardwood dominated, Canadian Shield catchments within the Turkey Lakes Watershed (TLW) of Ontario, Canada. A before-after-control-impact (BACI) study design was used to evaluate the immediate and legacy impacts (1-12 years after harvesting) of multiple forest harvesting strategies (i.e., clear-cut, shelterwood cut, and selection cut) on total phosphorus (TP) concentration and yield. Additionally, the hydrologic source areas contributing to stream flow were evaluated using end member mixing analysis (EMMA) in a legacy clear-cut (24 years after harvesting) and control catchment. Phosphorus sources in those catchments were evaluated by measuring TP and soluble reactive phosphorus (SRP) in these source areas and analyzing soil samples for total particulate phosphorus (TPP) and phosphorus fractions throughout the soil profile. These results were used to explain the legacy impacts of harvesting on seasonal and event-based TP and SRP concentrations draining the clear-cut and control catchments. Results from the BACI study and seasonal and event sampling demonstrate that harvesting had a small but significant impact on TP stream concentrations. However, as many of these differences were below the detection limit (< 1 µg l-1) the results are not practically significant. EMMA showed that stream water chemistry corresponds most with shallow groundwater and wetland groundwater chemistry in both catchments, suggesting that legacy forest harvesting has little impact on the primary water sources contributing to stream flow. Additionally, legacy forest harvesting appeared to have little impact on phosphorus source availability as there were few differences in phosphorus concentrations between the legacy clear-cut and control catchment within those source areas. Further evidence of this is demonstrated by the lack of differences in TPP and phosphorus fractions within the mineral soils between the two catchments. Finally, wetlands were identified as a major source of phosphorus delivered to streams as they are hydrologically connected with the stream channel and have measurable phosphorus concentrations. As legacy forest harvesting appears to have little long-term impacts on either hydrologic processes or phosphorus source availability its expected that little impact was observed on stream phosphorus concentration and yield. Results of the study suggest that forest harvesting may be a suitable land management strategy that promotes source water protection in hardwood-dominated Canadian Shield forested watersheds.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,002 |
| Études des sciences et des technologies | 0,002 | 0,001 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,001 | 0,001 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».