Pine plantation forest in Australia. iStock
This post was authored by Cyril Melikov, Senior Research Analyst of Natural Climate Solutions at EDF.
Forests planted for commercial purposes can help slow down climate change. How? With improved forestry management that uses forestry practices that increase the amount of carbon stored in commercial forests.
The idea is that foresters and land managers can put forestry practices in place that will raise the carbon levels in the plantation forests they manage, thus helping slow climate change.
For example, foresters could harvest trees at an older age than the age at which they would normally be harvested (known as extending the rotation length). Or they could plant several trees species in the same tree plantation (known as mixed planting) as opposed to planting only one tree species. Or they could add nutrients to the soil using inorganic or organic nutrient sources (known as fertilization).
All these practices could add carbon to plantation forests. Their study has gained traction over the past decade as improved forest management could represent a cost-effective and rapidly deployable natural climate solution, or NCS. It’s a promising avenue for climate change mitigation.
Global impact
The effects of improved management on carbon stocks in tree plantations have mainly been documented at individual sites.
Now new research published in Current Forestry Reports assesses and reviews the global impacts of three common forest management practices on aboveground carbon stocks in plantation forests:
- Application of inorganic nitrogen, phosphorus, and potassium (NPK) fertilizer.
- Interplanting with nitrogen fixing species (a type of mixed planting).
- Thinning.
This work updates and synthesizes the understanding of how different management actions impact aboveground carbon stocks globally, particularly at scales relevant for designing and implementing forest-based natural climate solutions.
Using a meta-analysis approach, we found that the effect of management actions on plantation forest carbon depended heavily on factors such as species selection, tree age, time since action, soil moisture regime, and previous land use.
For example, interplanting of plants that fix nitrogen from the atmosphere (N-fixing) boosted carbon storage in older, but not younger tree communities, known as stands. Our study also reveals that the use of N-fixing companion crops as a fertilization technique depends heavily on finding complementary crops and intercropped species.
We also show that substantial trade-offs exist for some management actions. For example, the application of nitrogen fertilizer will increase carbon accumulation over short periods of time, but the climate benefits can be negated by nitrogen-based greenhouse gas emissions associated with fertilizer manufacturing and use.
Finally, although thinning reduced aboveground carbon stocks, this research also suggests that the initial decrease in aboveground carbon caused by thinning operations can eventually be recovered by more vigorous growth after thinning, particularly when coupled with longer rotation times.
From research to design
The effect sizes quantified in our meta-analysis can serve as benchmarks for the design and scoping of improved forest management projects as forest based natural climate solutions. Overall, this new research underscores that management actions can enhance the climate mitigation potential of plantation forests, if performed with sufficient attention to the nuances of local conditions.