Change in CO₂ balance under a series of forestry activities in a cool‐temperate mixed forest with dense undergrowth

Abstract

To evaluate the effects on CO2 exchange of clearcutting a mixed forest and replacing it with a plantation, 4.5 years of continuous eddy covariance measurements of CO2 fluxes and soil respiration measurements were conducted in a conifer‐broadleaf mixed forest in Hokkaido, Japan. The mixed forest was a weak carbon sink (net ecosystem exchange, −44 g C m−2 yr−1), and it became a large carbon source (569 g C m−2 yr−1) after clearcutting. However, the large emission in the harvest year rapidly decreased in the following 2 years (495 and 153 g C m−2 yr−1, respectively) as the gross primary production (GPP) increased, while the total ecosystem respiration (RE) remained relatively stable. The rapid increase in GPP was attributed to an increase in biomass and photosynthetic activity of Sasa dwarf bamboo, an understory species. Soil respiration increased in the 3 years following clearcutting, in the first year mainly owing to the change in the gap ratio of the forest, and in the following years because of increased root respiration by the bamboo. The ratio of soil respiration to RE increased from 44% in the forest to nearly 100% after clearcutting, and aboveground parts of the vegetation contributed little to the RE although the respiration chamber measurements showed heterogeneous soil condition after clearcutting.

Ecosystem carbon (CO2 and CH4) fluxes of a Populus dettoides plantation in subtropical China during and post clear-cutting

“…The GEP was nearly all from the understory species for the tree leaves was underdeveloped. On the other hand, the ER from the cutover at our site was 1495 g-C m À2 yr À1 in the same period (July 2011-June 2012), which was larger than that from the Douglas-fir cutovers (840-1130 g-C m À2 yr À1 ) (Humphreys et al, 2005;Paul-Limoges et al, 2015), but similar with that from the cool-temperate mixed forest cutover (1395 g-C m À2 yr À1 ) (Aguilos et al, 2014;Takagi et al, 2009), and slight smaller than that from the pine plantation cutovers (1974 g-C m À2 yr À1 ) (Clark et al, 2004). Thus, we conclude that the high productivity of understory vegetation was the changed primary component responsible for the low carbon emission induced by the clear-cutting at our site.…”

“…In fact, the abundant and fast growing understory species always weaken the emission induced by clear-cutting and shorten the term of carbon source after clear-cutting (Kowalski et al, 2003;Machimura et al, 2005;Takagi et al, 2009). Clear-cutting effect on ER appeared less drastic than that on GEP (Clark et al, 2004;Humphreys et al, 2005;Takagi et al, 2009). Nevertheless, the living biomass removal and residual biomass (e.g.…”

“…on the arrival of next growing season. In the first 1-year period post clear-cutting (July 2011-June 2012, the GEP of the cutover was 1341 g-C m À2 yr À1 (Table 3), which was much larger than those from the Douglas-fir cutovers in Canada (130-220 g-C m À2 yr À1 ) (Humphreys et al, 2005;Paul-Limoges et al, 2015), the cooltemperate mixed forest cutover in Japan (481 g-C m À2 yr À1 ) (Aguilos et al, 2014;Takagi et al, 2009) and the pine plantation cutovers in Florida (705 g-C m À2 yr À1 ) (Clark et al, 2004). The GEP was nearly all from the understory species for the tree leaves was underdeveloped.…”

“…Similarly in Finland, the 4-year-old stand after clear-cutting was still a source of carbon throughout the year (386 g-C m À2 yr À1 ), while the 12-year-old stand was nearly neutral (Kolari et al, 2004). In a cooltemperature mixed forest in Japan, the CO 2 emission in the first year after clear-cutting was 569 g-C m À2 yr À1 , and $7 years later the clearcut regained as a carbon sink (Aguilos et al, 2014;Takagi et al, 2009). In a slash pine plantation forests in North Florida, USA with warm and humid climate, the CO 2 emission during the first year following the harvest ranged from 742 to 1269 g-C m À2 yr À1 (Clark et al, 2004;Gholz and Fisher, 1982), and turned neutral after $3 years (Gholz and Fisher, 1982).…”

“…Clear-cutting is a traditional harvest practice that is widely applied in forest management throughout the world (Keenan and Kimmins, 1993;Ma et al, 2013;Rosenvald and Lohmus, 2008). Numerous studies have reported that clearcutting turned the ecosystem from carbon sinks to carbon sources (Fredeen et al, 2007;Machimura et al, 2005;Takagi et al, 2009). The carbon emission after clear-cutting ranged from 200 to 1300 g-C m À2 yr À1 (Clark et al, 2004;Kowalski et al, 2004;Takagi et al, 2009), and the emission state lasted for either 3-10 years (Clark et al, 2004;Fredeen et al, 2007) or even 20 years (Law et al, 2001).…”