Elevated atmospheric CO2 and humidity delay leaf fall in Betula pendula, but not in Alnus glutinosa or Populus tremula × tremuloides

Table 1 Environmental variables and the lifespan of the leaf canopy (bud burst to final leaf fall) in Betula pendula at BangorFACE throughout the 4 years of CO₂ enrichment

Year	T_min (°C)	T_max (°C)	GDD (base 10 °C)	Rain (mm)	Ozone (AOT40)	Ambient CO₂ canopy lifespan (days)	Elevated CO₂ canopy lifespan (days)
2005	−3.5	27.0	1,910	726	9,058	201	201 (+0)
2006	−5.5	34.3	2,065	1,111	12,931	176	190 (+14)
2007	−3.3	24.3	1,672	705	3,783	172	172 (+0)
2008	−4.5	25.4	1,788	1,077	7,561	165	177 (+12)

The effect of elevated CO₂ on canopy lifespan is shown in parenthesis in days. T_min and T_max are based on the daily minimum and maximum temperatures
GDD growing degree days
\( \mathrm{GDD}=\left(\frac{T_{\min }+{T}_{\max }}{2}\right)\hbox{--} 10 \)

ISSN: 1297-966X