Future atmospheric CO₂ leads to delayed autumnal senescence

Abstract

Growing seasons are getting longer, a phenomenon partially explained by increasing global temperatures. Recent reports suggest that a strong correlation exists between warming and advances in spring phenology but that a weaker correlation is evident between warming and autumnal events implying that other factors may be influencing the timing of autumnal phenology. Using freely rooted, field-grown Populus in two Free Air CO 2 Enrichment Experiments (AspenFACE and PopFACE), we present evidence from two continents and over 2 years that increasing atmospheric CO 2 acts directly to delay autumnal leaf coloration and leaf fall. In an atmosphere enriched in CO 2 (by $ 45% of the current atmospheric concentration to 550 ppm) the end of season decline in canopy normalized difference vegetation index (NDVI) -a commonly used global index for vegetation greenness -was significantly delayed, indicating a greener autumnal canopy, relative to that in ambient CO 2 . This was supported by a significant delay in the decline of autumnal canopy leaf area index in elevated as compared with ambient CO 2 , and a significantly smaller decline in end of season leaf chlorophyll content. Leaf level photosynthetic activity and carbon uptake in elevated CO 2 during the senescence period was also enhanced compared with ambient CO 2 . The findings reveal a direct effect of rising atmospheric CO 2 , independent of temperature in delaying autumnal senescence for Populus, an important deciduous forest tree with implications for forest productivity and adaptation to a future high CO 2 world.

An Integrated Functional Genomics Consortium to Increase Carbon Sequestration in Poplars: Optimizing Aboveground Carbon Gain

“…In the F-2 generation, leaf development and quality traits including leaf area, leaf shape, epidermal cell area, stomatal number, specific leaf area (SLA), and the phenology trait, canopy senescence index, were sensitive to elevated CO 2. This latter finding is consistent with the findings of Taylor et al (2008) that a significant delay exists in the decline of autumnal canopy leaf area index under elevated CO 2 at both Aspen FACE and POPFACE.…”

Trehalose 6-Phosphate Is Required for the Onset of Leaf Senescence Associated with High Carbon Availability

“…There is also evidence from free-air CO 2 enrichment studies that increased carbon supply can accelerate senescence in plants with determinate growth, in particular in cereals (Nie et al, 1995;Zhu et al, 2009 (Tricker et al, 2004;Taylor et al, 2008). Both in annual plants and in trees, senescence can be accompanied by anthocyanin accumulation.…”

Field-Based Radiometry to Estimate Tidal Marsh Plant Growth in Response to Elevated CO2 and Nitrogen Addition

“…Radiometric VIs allow for comparison of treatment effects on the length of the growing season. A previous study using NDVI reported that elevated CO 2 may delay autumnal senescence (Taylor et al 2008). Here, most VIs revealed no strong differences in the course of autumnal senescence according to CO 2 treatment; however, several VIs, including NDVI and MSAVI2, indicate N-fertilized treatments approach the "zero point" more slowly (Fig.…”

“…Shaw et al 2002;Erickson et al 2007;Gedan and Bertness 2009;Reich 2009). A shortcoming of this approach is that seasonal patterns of plant growth may vary widely from year to year (Cleland et al 2007), particularly in the face of global change factors that alter phenological patterns of growth (Cleland et al 2006;Taylor et al 2008). Typically, researchers target peak biomass but lack foreknowledge of when plant biomass will peak, and thus, may substantially underestimate productivity when peak plant growth occurs before or after the prescribed sampling dates.…”