Intense light and conspecific density increase seedling mortality across age groups in a typhoon‐disturbed tropical forest

• Published in: Journal of vegetation science 2024-09, Vol.35 (5), p.n/a
• Main Authors: Lin, Yung‐Chiau, Chao, Kuo‐Jung, Song, Guo‐Zhang M., Chao, Wei‐Chun, Chang‐Yang, Chia‐Hao, Hsieh, Chang‐Fu
• Format: Article
• Language: English
• Subjects: Age; Age groups; competition; Coniferous forests; conservation areas; conspecificity; deciduous forests; Density; disturbances; ecological resilience; Ecosystem resilience; Foothills; Generalized linear models; Health risks; hills; life history; light; light intensity; Light levels; Microhabitats; Mortality; Mortality risk; Nature reserves; negative density dependence; plant establishment; Planting density; risk; Risk factors; seedling survival limitations; Seedlings; Shade; shade tolerance; species; Species diversity; Statistical models; Survival; Taiwan; Tropical forests; Typhoons
• ISSN: 1100-9233; 1654-1103
• DOI: 10.1111/jvs.13309

Questions Maintaining forest species diversity, regenerative function and ecosystem resilience begins with successful seedling establishment. Despite their critical role, seedlings face the highest mortality risks among plant life‐history stages. Our research aims to answer the following questions: In a tropical forest disturbed by typhoons, what is the median survival time for seedlings, to what extent do light levels contribute to mortality risks and what are the crucial mortality risks across seedling age groups? Location A tropical mountain zonal foothill evergreen broad‐leaved forest in Nanjenshan Nature Reserve, Taiwan, frequently visited by typhoons. Methods We investigated woody seedlings in 75 quadrats (each 1 m × 1 m) every 3 months from October 2009 to January 2018, spanning 8.3 years with 34 censuses. We used the Kaplan–Meier method to estimate seedlings’ median survival time and Generalized Linear Models to identify mortality risk factors for all seedlings and those that persisted beyond the median survival time. Results The median survival time for all seedlings was 0.5 years, ranging from 0.25 years for shade‐intolerant species to 1.25 years for shade‐tolerant species. Seedlings germinated in high‐light microhabitats and high conspecific seedling density exhibited higher mortality probabilities, regardless of age. Conclusions This study reveals the short survival time and key mortality risks of seedlings in a typhoon‐disturbed forest. The negative impact of light levels on seedling survival highlights the potential consequences of increased light levels resulting from typhoon disturbances in the study region. Mortality among seedling age groups in a typhoon‐disturbed tropical forest is constrained by intense light levels and high conspecific density. Quarterly census data over 8.3 years revealed that 50% of new seedlings died within 0.5 years, and 50% of shade‐tolerant species within 1.25 years. The negative influence of light suggests that increasing typhoon intensity could reshape future forest composition.