Today we celebrate International Day for Forests. Organised by the UN, International Day for Forests raises awareness of the importance of all types of woodlands and trees, and celebrates the ways in which they sustain and protect us. In order to highlight the importance of wood energy, sustainable development and climate change, the theme for 2017 is ‘Forests and Energy’.
Tropical forests play an important role in global carbon storage and sequestration and are therefore important natural solutions for climate change mitigation. To optimize the use of tropical forests for climate change mitigation and other important functions and services, such as biodiversity conservation and timber harvesting, we need to understand how the dynamics of these forests depend on abiotic conditions, biotic conditions, and human influences.
In our study, ‘Abiotic and biotic drivers of biomass change in a Neotropical forest’, we developed a comprehensive framework to understand drivers of net biomass change. We evaluated how abiotic conditions (water and nutrient availability and disturbance intensity) and biotic conditions (species and trait diversity, community-mean trait values, and forest density) shape biomass recruitment, biomass growth and biomass mortality, and how all these underlie net biomass change.
Using 48 1-ha plots in a moist tropical forest in Bolivia, we evaluated the direct and indirect effects of abiotic and biotic conditions on recruitment, growth and mortality using structural equation modelling. We showed that most of net biomass change is determined by mortality, but that mortality cannot be predicted by these abiotic and biotic conditions. Recruitment and growth are mostly driven by soil water availability and forest density, and not by the diversity or functional composition of the forest.
These results imply that we need ways to better understand and predict mortality, in order to increase carbon sequestration potential and resilience. Moreover, the importance of water availability suggests that this moist forest is vulnerable to climate change.
In temperate ecosystems, diversity is often found to buffer the effect of environmental fluctuations on ecosystem functioning. We found no diversity effects on recruitment, growth and mortality, suggesting that diversity does not necessarily enhance ecosystem functioning on the short term. However, such diversity effects may differ among forest types and depend on the spatial and temporal scale considered.
This study was part of the ROBIN-project, which includes other studies which have shown that the role of diversity and other abiotic and biotic drivers on forest dynamics strongly depends on tropical forest type, spatial scale and temporal scale. Whereas diversity effects are often weak in individual site studies focusing on short temporal scales (such as this study), positive diversity effects are found for sites across the Neotropics (e.g. Poorter et al. 2015) and for (modelling) studies focusing on long temporal scales (e.g. Sakschewski et al. 2016).
To work towards a more comprehensive understanding of drivers behind tropical forest dynamics, we need to use and integrate different forest types and spatiotemporal scales, and apply a range of approaches including empirical, remote sensing and ecosystem modelling (van der Sande et al. 2017).
Masha van der Sande, Helmholtz Centre for Environmental Research GmbH (UFZ) / German Centre for Integrative Biodiversity Research (iDiv)
Additionally, Wiley have coordinated a special Plant Science Virtual Issue in celebration of today, which includes a Journal of Ecology paper which was published last month. All articles are free to read until April 21 2017.
Read Masha’s full paper here: Abiotic and biotic drivers of biomass change in a Neotropical forest