Growing biodiverse carbon-rich forests

Background

Carbon storage and biodiversity has long been viewed as completely separate restoration objectives, resulting in parceling tracts of restoration land for one objective or the other. This study shows that the relationship between plant functional diversity and carbon sequestration rate depends on climate and habitat factors. Knowing this relationship, a restoration site can be managed for both objectives.

Conclusions and Takeaways

The study found that water availability is a key driving factor in making restoration decisions for carbon-biodiversity cobenefits. Under limited water conditions only a limited set of functional traits can establish (fast-growing, shade intolerant, not water-demanding, small seeds), thus undermining the objective of maximizing biodiversity. On the other hand, water abundant sites are capable of supporting the coexistence of higher tree diversity. This indicates that it is not always possible to maximize both carbon and biodiversity in dry conditions.

To optimize carbon-biodiversity cobenefits, the best regeneration method was found to be enrichment planting aimed at maximizing species diversity. This decision takes most effect in lowlands and wet-hot uplands; in arid-hot uplands, there is no significant difference between natural and assisted regeneration. To optimize carbon-biodiversity cobenefits, applying one of the following thinning methods were found to be effective regardless of climate or habitat factors: 1) selectively thinning dominant trees, 2) thinning dominant trees with low density wood, or 3) retaining taller trees that produce larger seeds. Best thinning frequency differs between sites: wet-hot uplands respond best to 5-year thinnings for one of the dominant plant functional traits while lowlands and arid-hot uplands respond best to annual thinning for one of the dominant traits.