Canopy structure and phenology modulate the impacts of solar radiation on C and N dynamics during litter decomposition in a temperate forest

• Published in: The Science of the total environment Vol. 820; p. 153185
• Main Authors: Wang, Qing-Wei, Robson, Thomas Matthew, Pieristè, Marta, Kenta, Tanaka, Zhou, Wangming, Kurokawa, Hiroko
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 10.05.2022
• Subjects: blue light; Canopy cover; canopy gaps; carbon; Carbon loss; Climate; deciduous forests; Ecosystem; environment; forest litter; Forests; land use; leaf abscission; light intensity; lignin; Mesic ecosystems; nitrogen; Nutrient dynamics; organic matter; phenology; Photodegradation; photolysis; Plant Leaves - metabolism; Seasons; spring; temperate forests; Trees; ultraviolet radiation; understory; Mesic ecosystems; Photodegradation; Nutrient dynamics; Canopy cover; Carbon loss
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.153185

Decomposition of plant organic matter plays a key role in the terrestrial biogeochemical cycles. Sunlight has recently been identified as an important contributor to carbon [C] turnover through photodegradation, accelerating decomposition even in forest ecosystems where understorey solar irradiance remains relatively low. However, it is uncertain how C and nutrients dynamics respond to fluctuations in solar spectral irradiance caused by canopy structure (understorey vs. gaps) and season (open vs. closed canopy phenology). Spectral-attenuation treatments were used to compare litter decomposition over eight months, covering canopy phenology, in a temperate deciduous forest and an adjacent gap. Exposure to the full spectrum of sunlight increased the loss of litter C and lignin by 75% and 64% in the forest gap, and blue light was responsible for respectively 27% and 42% of that loss. Whereas in the understorey, C and lignin loss were similar among spectral-attenuation treatments over the experimental period, except prior to and during spring canopy flush when exposure to the full spectrum of sunlight promoted C loss by 15% overall, 80% of which was attributable to ultraviolet-B (UV-B) radiation. Nitrogen [N] was immobilized in the understorey during canopy flush before the canopy completely closed but N was swiftly released during canopy leaf-fall. Our study suggests that blue-driven photodegradation plays an important role in lignin decomposition and N dynamics in canopy gaps, whereas seasonal canopy phenology affecting sunlight reaching the forest floor drastically changes patterns of C and N in litter during decomposition. Hence, including sunlight dynamics driven by canopy structure and phenology would improve estimates of biogeochemical cycling in forests responding to changes in climate and land-use. [Display omitted] •Sunlight drives nutrient dynamics below a forest canopy.•Blue light increases the loss of litter C and lignin in the forest gap.•UV-B radiation promotes litter C loss in the forest understorey.•Litter N tends to be mineralized in the gap but immobilized in the understorey.