Impacts of fire and climate change on long-term nitrogen availability and forest productivity in the New Jersey Pine Barrens

Abstract

Increased wildfires and temperatures due to climate change are expected to have profound effects on forest productivity and nitrogen (N) cycling. Forecasts about how wildfire and climate change will affect forests seldom consider N availability, which may limit forest response to climate change, particularly in fire-prone landscapes. The overall objective of this study was to examine how wildfire and climate change affect long-term mineral N availability in a fire-prone landscape. We employed a commonly used landscape simulation model (LANDIS-II) in the New Jersey Pine Barrens, a landscape characterized by frequent small fires and fire-resilient vegetation. We found that fire had little effect on mineral N, whereas climate change and fire together reduced mineral N by the end of the century. Though N initially limited forest productivity, mineral N was no longer limiting after 50 years. Our results suggest that mineral N is resilient to fire under our current climate but not under climate change. Also, predictions that do not consider N limitation may underestimate short-term but not long-term productivity responses to climate change. Together these results illustrate the importance of including N dynamics when simulating the effects of climate change on forest productivity, particularly in fire-prone regions such as the New Jersey Pine Barrens.Résumé : On s'attend à ce que l'augmentation des températures et des feux de forêt due aux changements climatiques aient de sérieux impacts sur la productivité des forêts et le recyclage de l'azote (N). Les prévisions concernant les impacts des feux et des changements climatiques sur les forêts tiennent rarement compte de la disponibilité de N, laquelle peut limiter la réaction de la forêt aux changements climatiques, particulièrement dans les paysages sujets aux feux. L'objectif général de cette étude consistait à examiner comment les feux de forêt et les changements climatiques affectent la disponibilité à long terme de N minéral dans un paysage sujet aux feux. Nous avons utilisé un modèle de simulation du paysage d'usage courant (LANDIS-II) dans les pinèdes de la plaine côtière du New Jersey, un paysage caractérisé par de fréquents feux de faible intensité et une végétation qui supporte bien les feux. Nous avons trouvé que le feu avait peu d'effet sur N minéral tandis que les changements climatiques couplés aux feux réduisaient la disponibilité de N vers la fin du siècle. Même si initialement N limitait la productivité de la forêt, N minéral n'était plus un facteur limitant après 50 ans. Nos résultats indiquent que N minéral n'est pas affecté par les feux dans les conditions climatiques actuelles mais qu'il le sera dans les conditions associées aux changements climatiques. De plus, les prédictions qui ne tiennent pas compte de la disponibilité de N pourraient sous-estimer les réactions de la productivité aux changements climatiques à court mais non à long terme. Globalement, ces résultats illustrent l'importance d'inclure la dynamique de N lorsqu'on simule les effets de...

More than the sum of its parts: how disturbance interactions shape forest dynamics under climate change

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Widespread severe wildfires under climate change lead to increased forest homogeneity in dry mixed‐conifer forests

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Spatial resilience of forested landscapes under climate change and management

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