期刊
ECOLOGY
卷 96, 期 9, 页码 2478-2487出版社
WILEY
DOI: 10.1890/14-1810.1
关键词
canopy; carbon cycling; disturbance; leaf area index (LAI); light; mortality; net primary production; northern Michigan, USA, forest; production efficiency; resilience; resistance
类别
资金
- Climate and Environmental Sciences Division, Office of Science, U.S. Department of Energy (DOE) [DE-SC0006708]
The global carbon (C) balance is vulnerable to disturbances that alter terrestrial C storage. Disturbances to forests occur along a continuum of severity, from low-intensity disturbance causing the mortality or defoliation of only a subset of trees to severe stand-replacing disturbance that kills all trees; yet considerable uncertainty remains in how forest production changes across gradients of disturbance intensity. We used a gradient of tree mortality in an upper Great Lakes forest ecosystem to: (1) quantify how aboveground wood net primary production (ANPP(w)) responds to a range of disturbance severities; and (2) identify mechanisms supporting ANPP(w) resistance or resilience following moderate disturbance. We found that ANPP(w) declined nonlinearly with rising disturbance severity, remaining stable until >60% of the total tree basal area senesced. As upper canopy openness increased from disturbance, greater light availability to the subcanopy enhanced the leaf-level photosynthesis and growth of this formerly light-limited canopy stratum, compensating for upper canopy production losses and a reduction in total leaf area index (LAI). As a result, whole-ecosystem production efficiency (ANPP(w)/LAI) increased with rising disturbance severity, except in plots beyond the disturbance threshold. These findings provide a mechanistic explanation for a nonlinear relationship between ANPP(w) and disturbance severity, in which the physiological and growth enhancement of undisturbed vegetation is proportional to the level of disturbance until a threshold is exceeded. Our results have important ecological and management implications, demonstrating that in some ecosystems moderate levels of disturbance minimally alter forest production.
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