|Title||Net primary production of a temperate deciduous forest exhibits a threshold response to increasing disturbance severity|
|Publication Type||Journal Article|
|Year of Publication||2015|
|Authors||Stuart-Haëntjens EJ, Curtis PS, Fahey RT, Vogel CS, Gough CM|
|Pagination||2478 - 2487|
|Type of Article||Masters Thesis|
The global carbon (C) balance is vulnerable to disturbances that alter terrestrialC storage. Disturbances to forests occur along a continuum of severity, from low-intensitydisturbance 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 forestproduction changes across gradients of disturbance intensity. We used a gradient of treemortality in an upper Great Lakes forest ecosystem to: (1) quantify how aboveground woodnet primary production (ANPPw) responds to a range of disturbance severities; and (2)identify mechanisms supporting ANPPwresist ance or resilience fo llowing modera tedisturbance. We found that ANPPwdeclined nonlinearly with rising disturbance severity,remaining stable until .60% of the total tree basal area senesced. As upper canopy opennessincreased from disturbance, greater light availability to the subcanopy enhanced the leaf-levelphotosynthesis and growth of this formerly light-limited canopy stratum, compensating forupper canopy production losses and a reduction in total leaf area index (LAI). As a result,whole-ecosystem prod uction efﬁciency (ANPPw/LAI) increa sed with rising disturbanceseverity, except in plots beyond the disturbance threshold. These ﬁndings provide amechanistic explanation for a nonlinear relationship between ANPPwand disturbanceseverity, in which the physiological and growth enhancement of undisturbed vegetation isproportional to the level of disturbance until a threshold is exceeded. Our results haveimportant ecological and management implications, demonstrating that in some ecosystemsmoderate levels of disturbance minimally alter forest production.