The sensitivity of wet and dry tropical forests to climate change in Bolivia

Abstract

Bolivia's forests contribute to the global carbon and water cycle, as well as to global biodiversity. The survival of these forests may be at risk due to climate change. To explore the associated mechanisms and uncertainties, a regionally adapted dynamic vegetation model was implemented for the Bolivian case, and forced with two contrasting climate change projections. Changes in carbon stocks and fluxes were evaluated, factoring out the individual contributions of atmospheric carbon dioxide ([CO2]), temperature, and precipitation. Impacts ranged from a strong increase to a severe loss of vegetation carbon (cv), depending on differences in climate projections, as well as the physiological response to rising [CO2]. The loss of cv simulated for an extremely dry projection was primarily driven by a reduction in gross primary productivity, and secondarily by enhanced emissions from fires and autotrophic respiration. In the wet forest, less precipitation and higher temperatures equally reduced cv, while in the dry forest, the impact of precipitation was dominating. The temperature‐related reduction of cv was mainly due to a decrease in photosynthesis and only to lesser extent because of more autotrophic respiration and less stomatal conductance as a response to an increasing atmospheric evaporative demand. Under an extremely dry projection, tropical dry forests were simulated to virtually disappear, regardless of the potential fertilizing effect of rising [CO2]. This suggests a higher risk for forest loss along the drier southern fringe of the Amazon if annual precipitation will decrease substantially.

Will seasonally dry tropical forests be sensitive or resistant to future changes in rainfall regimes?

“…In their simulations and in satellite observations, annual GPP of SDTF was more sensitive to rainfall anomalies than that of wet tropical forests. When the LPJ-GUESS model was forced with the precipitation projections that have been projected for Bolivia at the end of the 21st century, Seiler et al (2015) found that the pure effect of decreased rainfall was a >70% reduction in SDTF vegetation carbon. Xu et al (2016) were the first to incorporate an explicit plant hydraulic scheme into model simulations focusing on SDTF.…”

Loss carbon by recent deforestation (2010-2013) in the lowlands and Yungas of Bolivia

“…62 millones de tC/año -es plausible esperar una disminución cercana al 17% del carbono remanente. Las implicaciones de esta pérdida de cobertura vegetal en la capacidad de los bosques remanentes para mitigar las variaciones de temperatura y precipitación esperadas por impacto del cambio climático (ver Seiler et al 2014Seiler et al , 2015 son desconocidas. Un siguiente paso será también estimar qué representó la deforestación ocurrida entre 2010 y 2013 en términos de emisiones netas de CO 2 (e.g.…”

¿Serán vulnerables los bosques tropicales secos a los cambios climáticos, y cuáles serán sus efectos sociales?

“…Sin embargo, es probable que sus respuestas sean diferentes a la de los bosques tropicales húmedos debido a la diferente fenología de las copas de los árboles (Eamus, 1999) y los diferentes procesos hidrológicos dominantes que afectan el flujo de agua (Farrick & Branfireun, 2013). Por ejemplo, un estudio utilizó un modelo dinámico de vegetación para evaluar cómo los aumentos de temperatura y la disminución de la lluvia afectan a los bosques húmedos y secos en Bolivia (Seiler, Hutjes, Kruijt & Hickler, 2015). Concluyeron que las reservas de carbono en la vegetación eran más sensibles a los cambios en el clima en los bosques secos que en los húmedos; además, los cambios en los bosques húmedos se debieron a una combinación de temperatura y precipitación, mientras que en los bosques secos los cambios fueron en respuesta a los regímenes de precipitación (Seiler et al, 2015).…”