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Observations from old forests underestimate climate change effects on tree mortality.

Luo Y, Chen HY - Nat Commun (2013)

Bottom Line: Furthermore, interpreting the climate change-associated tree mortality estimated from old forests for regional forests rests on an un-tested assumption that the effects of climate change are the same for young and old forests.Here we disentangle the effects of climate change and stand developmental processes on tree mortality.We show that both climate change and forest development processes influence temporal mortality increases, climate change-associated increases are significantly higher in young than old forests, and higher increases in younger forests are a result of their higher sensitivity to regional warming and drought.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Natural Resources Management, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario, Canada P7B 5E1.

ABSTRACT
Understanding climate change-associated tree mortality is central to linking climate change impacts and forest structure and function. However, whether temporal increases in tree mortality are attributed to climate change or stand developmental processes remains uncertain. Furthermore, interpreting the climate change-associated tree mortality estimated from old forests for regional forests rests on an un-tested assumption that the effects of climate change are the same for young and old forests. Here we disentangle the effects of climate change and stand developmental processes on tree mortality. We show that both climate change and forest development processes influence temporal mortality increases, climate change-associated increases are significantly higher in young than old forests, and higher increases in younger forests are a result of their higher sensitivity to regional warming and drought. We anticipate our analysis to be a starting point for more comprehensive examinations of how forest ecosystems might respond to climate change.

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Year effect on annual tree mortality probability and sensitivity scores of predictors.(a) Year effect on annual tree mortality probability, logit (p), estimated by Model 1 (without endogenous factors as predictors) and Model 2 (with endogenous factors as predictors). Models were separately developed all plots (All), young plots (Young, initial SA ≤80 years) and old plots (Old, initial SA >80 years), respectively. Error bars are 95% credible intervals. (b) Sensitivity scores. For each species and age group (All, Young or Old), sensitivity scores of predictors from Model 1 are on the left and Model 2 on the right.
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f1: Year effect on annual tree mortality probability and sensitivity scores of predictors.(a) Year effect on annual tree mortality probability, logit (p), estimated by Model 1 (without endogenous factors as predictors) and Model 2 (with endogenous factors as predictors). Models were separately developed all plots (All), young plots (Young, initial SA ≤80 years) and old plots (Old, initial SA >80 years), respectively. Error bars are 95% credible intervals. (b) Sensitivity scores. For each species and age group (All, Young or Old), sensitivity scores of predictors from Model 1 are on the left and Model 2 on the right.

Mentions: With all data pooled, the effects of year, used to represent climate change drivers as a whole in both Model 1 (with only year as a predictor) and Model 2 (with year, endogenous processes and their interactions as predictors) were significantly positive for all study species (Table 1; Fig. 1), indicating significant increases of annual mortality probability during the study period (Fig. 2). The two models, however, produced different estimates for climate change-associated tree mortality: year effects estimated by Model 1 are bigger for Populus tremuloides, Pinus banksiana, Picea mariana and Picea glauca, but smaller for Populus balsamifera than those by Model 2 (Fig. 1a), resulting in different estimates of annual tree mortality probability from the two models (Fig. 2).


Observations from old forests underestimate climate change effects on tree mortality.

Luo Y, Chen HY - Nat Commun (2013)

Year effect on annual tree mortality probability and sensitivity scores of predictors.(a) Year effect on annual tree mortality probability, logit (p), estimated by Model 1 (without endogenous factors as predictors) and Model 2 (with endogenous factors as predictors). Models were separately developed all plots (All), young plots (Young, initial SA ≤80 years) and old plots (Old, initial SA >80 years), respectively. Error bars are 95% credible intervals. (b) Sensitivity scores. For each species and age group (All, Young or Old), sensitivity scores of predictors from Model 1 are on the left and Model 2 on the right.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3644074&req=5

f1: Year effect on annual tree mortality probability and sensitivity scores of predictors.(a) Year effect on annual tree mortality probability, logit (p), estimated by Model 1 (without endogenous factors as predictors) and Model 2 (with endogenous factors as predictors). Models were separately developed all plots (All), young plots (Young, initial SA ≤80 years) and old plots (Old, initial SA >80 years), respectively. Error bars are 95% credible intervals. (b) Sensitivity scores. For each species and age group (All, Young or Old), sensitivity scores of predictors from Model 1 are on the left and Model 2 on the right.
Mentions: With all data pooled, the effects of year, used to represent climate change drivers as a whole in both Model 1 (with only year as a predictor) and Model 2 (with year, endogenous processes and their interactions as predictors) were significantly positive for all study species (Table 1; Fig. 1), indicating significant increases of annual mortality probability during the study period (Fig. 2). The two models, however, produced different estimates for climate change-associated tree mortality: year effects estimated by Model 1 are bigger for Populus tremuloides, Pinus banksiana, Picea mariana and Picea glauca, but smaller for Populus balsamifera than those by Model 2 (Fig. 1a), resulting in different estimates of annual tree mortality probability from the two models (Fig. 2).

Bottom Line: Furthermore, interpreting the climate change-associated tree mortality estimated from old forests for regional forests rests on an un-tested assumption that the effects of climate change are the same for young and old forests.Here we disentangle the effects of climate change and stand developmental processes on tree mortality.We show that both climate change and forest development processes influence temporal mortality increases, climate change-associated increases are significantly higher in young than old forests, and higher increases in younger forests are a result of their higher sensitivity to regional warming and drought.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Natural Resources Management, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario, Canada P7B 5E1.

ABSTRACT
Understanding climate change-associated tree mortality is central to linking climate change impacts and forest structure and function. However, whether temporal increases in tree mortality are attributed to climate change or stand developmental processes remains uncertain. Furthermore, interpreting the climate change-associated tree mortality estimated from old forests for regional forests rests on an un-tested assumption that the effects of climate change are the same for young and old forests. Here we disentangle the effects of climate change and stand developmental processes on tree mortality. We show that both climate change and forest development processes influence temporal mortality increases, climate change-associated increases are significantly higher in young than old forests, and higher increases in younger forests are a result of their higher sensitivity to regional warming and drought. We anticipate our analysis to be a starting point for more comprehensive examinations of how forest ecosystems might respond to climate change.

Show MeSH