### 2.20.1.1. 14.1.1 Onset Periods[¶](#onset-periods "Permalink to this headline")

The deciduous phenology algorithms specify the occurrence of onset growth periods (Figure 14.1). Carbon fluxes from the transfer pools into displayed growth are calculated during these periods as:

(2.20.1)[¶](#equation-20-1 "Permalink to this equation")\\\[CF\_{leaf\\\_ xfer,leaf} =r\_{xfer\\\_ on} CS\_{leaf\\\_ xfer}\\\]

(2.20.2)[¶](#equation-20-2 "Permalink to this equation")\\\[CF\_{froot\\\_ xfer,froot} =r\_{xfer\\\_ on} CS\_{froot\\\_ xfer}\\\]

(2.20.3)[¶](#equation-20-3 "Permalink to this equation")\\\[CF\_{livestem\\\_ xfer,livestem} =r\_{xfer\\\_ on} CS\_{livestem\\\_ xfer}\\\]

(2.20.4)[¶](#equation-20-4 "Permalink to this equation")\\\[CF\_{deadstem\\\_ xfer,deadstem} =r\_{xfer\\\_ on} CS\_{deadstem\\\_ xfer}\\\]

(2.20.5)[¶](#equation-20-5 "Permalink to this equation")\\\[CF\_{livecroot\\\_ xfer,livecroot} =r\_{xfer\\\_ on} CS\_{livecroot\\\_ xfer}\\\]

(2.20.6)[¶](#equation-20-6 "Permalink to this equation")\\\[CF\_{deadcroot\\\_ xfer,deadcroot} =r\_{xfer\\\_ on} CS\_{deadcroot\\\_ xfer} ,\\\]

with corresponding nitrogen fluxes:

(2.20.7)[¶](#equation-20-7 "Permalink to this equation")\\\[NF\_{leaf\\\_ xfer,leaf} =r\_{xfer\\\_ on} NS\_{leaf\\\_ xfer}\\\]

(2.20.8)[¶](#equation-20-8 "Permalink to this equation")\\\[NF\_{froot\\\_ xfer,froot} =r\_{xfer\\\_ on} NS\_{froot\\\_ xfer}\\\]

(2.20.9)[¶](#equation-20-9 "Permalink to this equation")\\\[NF\_{livestem\\\_ xfer,livestem} =r\_{xfer\\\_ on} NS\_{livestem\\\_ xfer}\\\]

(2.20.10)[¶](#equation-20-10 "Permalink to this equation")\\\[NF\_{deadstem\\\_ xfer,deadstem} =r\_{xfer\\\_ on} NS\_{deadstem\\\_ xfer}\\\]

(2.20.11)[¶](#equation-20-11 "Permalink to this equation")\\\[NF\_{livecroot\\\_ xfer,livecroot} =r\_{xfer\\\_ on} NS\_{livecroot\\\_ xfer}\\\]

(2.20.12)[¶](#equation-20-12 "Permalink to this equation")\\\[NF\_{deadcroot\\\_ xfer,deadcroot} =r\_{xfer\\\_ on} NS\_{deadcroot\\\_ xfer} ,\\\]

where CF is the carbon flux, CS is stored carbon, NF is the nitrogen flux, NS is stored nitrogen, \\({r}\_{xfer\\\_on}\\) (s\-1) is a time-varying rate coefficient controlling flux out of the transfer pool:

(2.20.13)[¶](#equation-zeqnnum852972 "Permalink to this equation")\\\[\\begin{split}r\_{xfer\\\_ on} =\\left\\{\\begin{array}{l} {{2\\mathord{\\left/ {\\vphantom {2 t\_{onset} }} \\right.} t\_{onset} } \\qquad {\\rm for\\; }t\_{onset} \\ne \\Delta t} \\\\ {{1\\mathord{\\left/ {\\vphantom {1 \\Delta t}} \\right.} \\Delta t} \\qquad {\\rm for\\; }t\_{onset} =\\Delta t} \\end{array}\\right.\\end{split}\\\]

and _t_onset (s) is the number of seconds remaining in the current phenology onset growth period (Figure 14.1). The form of Eq. [(2.20.13)](#equation-zeqnnum852972) produces a flux from the transfer pool which declines linearly over the onset growth period, approaching zero flux in the final timestep.

