Multi‐stemming and size enhance survival of dominant tree species in a frequently typhoon‐disturbed forest

Abstract

Questions:Quantifying tree species persistence through recurrent disturbances is of crucial importance for understanding forest dynamics in typhoon-prone regions.We ask the following: (a) What are the major determinants of dominant tree survival in frequently typhoon-disturbed forests? (b) Are survival determinants different between small and large trees?Location: A subtropical old-growth forest located in Fushan, Taiwan (24°45′34″N, 121°33′58″E), with frequent typhoon disturbances.Methods: Data were from three consecutive censuses of a 25-ha permanent forest plot that censused trees ≥1 cm in diameter every five years. The survival of three dominant tree species was modeled using generalized additive model and boosted trees with abiotic and biotic predictors. We evaluated model performance using validation data obtained from the two available census intervals.Results: Model validations showed that multi-stemming and tree size enhanced the survival of large and small trees, respectively. For the most dominant species, multi-stemming had a consistently positive effect on survival irrespective of diameter classes. Abiotic factors and conspecific density had little effect on tree survival. Furthermore, evaluating model performance based on the data used in the model construction (i.e., training data) overestimated the predictive ability of survival models. Conclusions:We showed that the survival determinants for the three most dominant species at Fushan changed from tree size for small trees to multi-stemming for large trees. The results suggest that the dominant species in this frequently typhoon-disturbed forest have the stature and architectural traits to persist, and thereby maintain their dominance and shape the forest physiognomy. Our approach illustrates how datasets from different census periods can be used in model validation to better assess model performance. K E Y W O R D Sdevelopmental change, Fushan Forest Dynamics Plot, life history strategy, mortality, multistemming, sprouting, subtropical forest, survival, tree size, typhoon disturbance 430 |

Damage to living trees contributes to almost half of the biomass losses in tropical forests

“…Fushan, the site with the highest contribution of alive damaged trees to total AGB losses, has been impacted by nine typhoons and 18 tropical storms in the last 20 years (i.e., the center of the storm passed within a 50 km radius of the plot), with two of them occurring during the course of this study ( Nesat typhoon in 2017‐07‐29 and Lupit tropical storm in 2021‐08‐07; Taiwan Center Weather Bureau). The prevalence of windstorms in this site results in disproportionate losses of AGB via damage that does not necessarily translate into individual tree mortality because many species in this site are adapted to withstand strong winds (e.g., multi‐stemmed, short‐stature, and sprouting; Su et al, 2020; Yap et al, 2016). High damage and low mortality have been documented for trees in other typhoon‐disturbed forests (Hall et al, 2020; Hogan et al, 2018; Tanner et al, 2014; Yap et al, 2016).…”

Major axes of variation in tree demography across global forests

“…dbh) as a covariate would most likely explain some of the residual variance (Hülsmann et al ., 2018). Moreover, functional traits at the individual level (Su et al ., 2020) and structures that explicitly deal with spatial (Wiegand et al ., 2017) and temporal autocorrelation may explain additional differences in individual vital rates. On the other hand, there are intrinsic limits to what can be explained by even the most detailed models, as the residual variance also includes inherent noise which, by definition, is unexplainable.…”

Individual tree damage dominates mortality risk factors across six tropical forests

“…As modular organisms, trees can delay death or recover by compartmentalising damage (Shigo, 1984; Finch, 1990; Bernard et al ., 2020). This trait, along with the ability to resprout, constitute key traits that allow trees to withstand damage (Putz & Brokaw, 1989; Paciorek et al ., 2000; Su et al ., 2020).…”