Use absolute radiation instead of % intercepted to define senescence

[lpmorenoc]

Comment from James:

The accumulated LAIj by cohort is compared with the total LAI of the canopy when the radiation intercepted is 95 % (LAIXX). LAIXX is calculated using the Lambert-Beer law (Monsi and Saeki, 2005) (Eq. (4-19) and (4-20)). When LAIj is greater than LAIXS, senescence begins for that cohort. We had discussed this and suggested that senescence begins when a canopy level falls below a critical level of absolute PAR for a few day. This allows for higher LAIs during the long summer days with very high PAR in Keatings trials in Australia. This should be incorporated. (Note: there may also be a photoperiod effect but let's not get into that). `This is very easy to do and will make the model much more attractive as we can show high LAIs reported by some are possible. I would suggest that the limit be put at something like five days of leaves with less than 150 cal cm-2 day-1 (Sorry I am an old timer and still use old measures!) This will have to be converted to whatever units we use in the model.

[lpmorenoc]

Current output from Keating:

[lpmorenoc]

Assuming this conversion factor: 1 cal cm-2 day-1 = 4.1868 10-2 MJ m-2 day-1; 150 cal cm-2 day-1 = 6.2802 MJ m-2 day-1 This threshold could be high based on the low radiation levels observed sometimes in Keating experiment

[lpmorenoc]

When using the threshold for PAR of 6.2802 MJ m-2 day-1 to define leaf senescence, the LAI is too low: I used a threshold of 0.2 instead, representing 98.25% of radiation intercepted in a day with solar radiation of 25 MJ m-2 day-1 (PAR = 12.5) with a kcan of 0.45 and LAI of 9 using the Lambert-Beer law. The modification increased the LAI between January and April of 1978, but it is still below 10: And with a threshold of 0.1:

[lpmorenoc]

Other experiments (Thailand) before: with the threshold of 0.1: Variety KU 50 before: Variety KU 50 now with the threshold of 0.1. It does not change because the shading was not limiting the LAI:

[lpmorenoc]

Quilichao before: Now with the threshold of 0.1: