Altered climate leads to positive density‐dependent feedbacks in a tropical wet forest

Abstract

Climate change is predicted to result in warmer and drier Neotropical forests relative to current conditions. Negative density-dependent feedbacks, mediated by natural enemies, are key to maintaining the high diversity of tree species found in the tropics, yet we have little understanding of how projected changes in climate are likely to affect these critical controls. Over 3 years, we evaluated the effects of a natural drought and in situ experimental warming on density-dependent feedbacks on seedling demography in a wet tropical forest in Puerto Rico. In the +4°C warming treatment, we found that seedling survival increased with increasing density of the same species (conspecific). These positive density-dependent feedbacks were not associated with a decrease in aboveground natural enemy pressure. If positive densitydependent feedbacks are not transient, the diversity of tropical wet forests, which may rely on negative density dependence to drive diversity, could decline in a future warmer, drier world. K E Y W O R D S arbuscular mycorrhizal fungi, climate change, negative density dependence, positive density dependence, tropical wet forest S U PP O RTI N G I N FO R M ATI O N Additional supporting information may be found online in the Supporting Information section. How to cite this article: Bachelot B, Alonso-Rodríguez AM, Aldrich-Wolfe L, Cavaleri MA, Reed SC, Wood TE. Altered climate leads to positive density-dependent feedbacks in a tropical wet forest. Glob Change Biol. 2020;26:3417-3428.

Precipitation‐drainage cycles lead to hot moments in soil carbon dioxide dynamics in a Neotropical wet forest

“…Decay rates depend on fragmentation efficiency and therefore on soil fauna activity (Sanderman & Amundson, 2003). However, global atmospheric CO 2 and climate change are altering the functioning of all of these trophic levels and of CO 2 dynamics (Allen & Allen, 2017; Allen, Kitajima, & Hernandez, 2014; Allen, Klironomos, Treseder, & Oechel, 2005; Bachelot et al., 2020).…”

Warming intensifies soil pathogen negative feedback on a temperate tree

“…The optimal temperature range for pathogen reproduction and infection is likely to explain the contrasting results of our study compared with those of Bachelot et al . ( 2020 ), who found that warming weakened plant–soil feedback. In their study, an increase of 4°C made temperature exceed the upper optimal range and was deleterious to the soil pathogens in the tropics.…”

“…For example, a 6‐yr warming experiment showed that increased temperature was a primary driver for the observed increase in foliar pathogen loads in a meadow ecosystem in the Tibet plateau (Liu et al ., 2019 ). Another in situ warming experiment in a wet tropical forest in Puerto Rico reported that the effect of conspecific negative density dependence (CNDD) on seedling survival changed to be positive after 3 yr of warming (presumably due to decreased pathogen pressure or other processes) (Bachelot et al ., 2020 ). This empirical result made the authors suggest that diversity of wet tropical forests could decline under global warming because of the weakening CNDD (Bachelot et al ., 2020 ).…”

“…Another in situ warming experiment in a wet tropical forest in Puerto Rico reported that the effect of conspecific negative density dependence (CNDD) on seedling survival changed to be positive after 3 yr of warming (presumably due to decreased pathogen pressure or other processes) (Bachelot et al ., 2020 ). This empirical result made the authors suggest that diversity of wet tropical forests could decline under global warming because of the weakening CNDD (Bachelot et al ., 2020 ). It however remains unclear how this result may be extrapolated to other forest ecosystems, particularly forests at higher latitudes where the intensity and trend of global warming are very different from that in the tropics (IPCC, 2013 ).…”

Predicting the responses of subalpine forest landscape dynamics to climate change on the eastern Tibetan Plateau

“…mortality, productivity and recruitment (Bachelot et al, 2020;Boulanger et al, 2017;Girardin et al, 2016;Kueppers et al, 2017;Kumarathunge et al, 2019;Liang et al, 2017;Liu et al, 2020;Way & Oren, 2010). However, the impact of climate change on forest ecosystems will greatly depend on our actions today and will vary tremendously across biomes and regions (IPCC, 2018).…”