Evaluation of isoprene emission rates of tropical trees by an iterative optimization procedure for G-93 parameters

An Overview of the Isoprenoid Emissions From Tropical Plant Species

“…C T for G93 postulates that the maximal temperature-dependent isoprene emission is almost 2-fold higher than the basal emission rate ( Is ). This magnitude is between 2 and 4 for most temperate plants ( Monson et al, 1992 ; Sharkey and Monson, 2014 ) but is >5 for most tropical tree species and > 10 for the regional highest emitters ( Ficus virgata and Calophyllum inophyllum ; Oku et al, 2008 , 2014 ; Higa et al, 2018 ). The pattern of the response of isoprene emissions to temperature for tropical species thus notably differed from the pattern predicted by the G93 model.…”

“…Emission inventories and model calculations have been developed to define the strength of regional and global BVOC emissions, but they rely mostly on studies of VOC emissions from temperate areas of North America and Europe, and more efforts in parameterizations are warranted for tropical regions ( Guenther et al, 1996b , 1999b , 2012 ; Holm et al, 2014 ; Mutanda et al, 2016 ; Higa et al, 2018 ).…”

“…In addition, the actual relative emission rate under standard conditions was notably lower than that postulated by the G93 model, which tended to overestimate Is when the average Is was estimated by G93 under variable conditions of temperature and light intensities for tropical species ( Oku et al, 2008 ). Therefore, G93 may provide higher normalized emission rates under standard conditions but lower rates for predicted emissions under high temperatures and light intensities, which also tended to overestimate the emission rate in the morning and evening and to underestimate the rate at midday ( Oku et al, 2008 ; Higa et al, 2018 ).…”

“…(2) , and α in Eq. (3) ( Mutanda et al, 2016 ; Higa et al, 2018 ). For illustration, original and changed parameters are presented in Table 1 for the species applied in these two studies.…”

“…The influence of seasonality is important in Amazonia ( Kuhn et al, 2002 ) and Xishuangbanna ( Wang et al, 2007 ). Other important tropical regions (e.g., Borneo), however, have little or no climatic seasonality, so emission algorithms need to be more region-specific ( Higa et al, 2018 ). Isoprene emission from tropical plants is also associated with physiological and developmental changes during the growing season, the capacity of isoprene emission to vary with foliar age and the highest capacity of isoprene emission from young mature leaves (recently fully expanded; Kuhn et al, 2004b ; Alves et al, 2014 ), indicating a variable inherent capacity of plants to synthesize isoprene during foliar development.…”