Age-dependent CO2 uptake of Salix nipponica estimated from annual destructive biomass sampling in a field-scale grid-based cultivation system

To mitigate damage from increasingly frequent and severe floods under climate change, the use of riparian corridors as flood buffers has been expanding. In particular, as part of Nature-based Solutions (NbS), growing efforts have focused on designing flood-buffer areas that reflect natural landscapes and geomorphic settings while actively incorporating natural attributes such as existing ecological conditions and vegetation distribution. In parallel, in response to carbon-neutrality policies, NbS-based flood-buffer spaces are increasingly being designed to include riparian vegetation communities—especially willows—so that these areas can also function as carbon sinks. Among willow species, Salix nipponica is the dominant riparian species in Korea; however, quantitative information on its age-dependent carbon dioxide uptake remains insufficient. Because carbon dioxide uptake can vary substantially with plant age, assessing uptake by growth stage or age class provides an important basis for characterizing carbon-sequestration potential and informing NbS design. In this study, we established a field-scale, grid-based cultivation system that enables annual destructive biomass sampling of Salix nipponica, with the ultimate objective of estimating age-dependent carbon dioxide uptake from the collected biomass data.

The field-scale grid-based cultivation system was established at the River Experiment Center of the Korea Institute of Civil Engineering and Building Technology using seeds of Salix nipponica collected from the Nakdonggang River. To identify growth characteristics, the basal diameter and height of sample trees were measured annually. Biomass for carbon dioxide uptake estimation was measured after uprooting sample trees and oven-drying to constant weight. Carbon dioxide uptake calculated from these directly measured biomass data corresponds to a measurement-based Tier 3 approach under the IPCC (Intergovernmental Panel on Climate Change) guideline. Associated with growth was estimated by applying the carbon fraction of dry matter and the mass ratio of CO₂ to C provided in the IPCC guideline.

The results of this study are presented for years 1–3 after planting in the cultivation system. Average individual biomass increased from 37 g (one-year) to 847 g (two-year) and 2,526 g (three-year), while average annual CO₂ uptake increased from 0.3 to 4 and 8 ton·ha⁻¹·yr⁻¹ over the same period. The increase in both biomass and average annual CO₂ uptake from one-year to two-year was larger than that from two-year to three-year. Compared with a previous study that estimated age-dependent CO₂ uptake for major forest tree species, CO₂ uptake in Salix nipponica was 1.2 times higher in two-year than that of same-aged softwood species and 1.3 times higher in three-year than that of same-aged hardwood species. The results quantitatively present the carbon sequestration potential of riparian willow stands in Korea. The identified age-dependent carbon dioxide uptake characteristics of Salix nipponica would demonstrate applicability to the development of river management strategies for climate change adaptation.

 

Acknowledge

This research was funded by the Korea Environment Industry & Technology Institute (KEITI) through the Smart Water-supply Service Research Program, funded by the Korea Ministry of Climate, Energy, Environment (MCEE)(RS-2022-KE002091).