# Net Ecosystem Exchange of CO\({}_{2}\) in Deciduous Pine Forest of Lower Western Himalaya, India
## Materials and Methods
### Micrometeorological Observations and Data Processing  
An INSAT uplinked micrometeorological tower (13 m) was installed within the homogenously distributed young pine forest with a fetch of about 500 m from all directions (fetch ratio = 1:100) for continuous and automated measurements of radiation components (shortwave and longwave), energy and water balance. The slow response sensors consisted of a four component net radiometer (at 10 m; Kipp and Zonen, Delft, Netherlands), two-depth (at 0.1 m and 0.2 m) self-calibrating soil heat flux plates (HFP-01 SC, Radiation & Energy Balance System Inc., Bellevue, WA, USA), three-height (at 4.5 m, 7.5 m, and 12.5 m) air temperature-relative humidity (AT--RH) probes with a shielded and aspirated sensor (HMP-45C, Campbell scientific, Logan, UT, USA), three-height (at 4.5 m, 7.5 m, and 12.5 m) anemometer-vane for wind speed and direction (KDS-131, Komoline Aerospace Limited, Ahmedabad, India), and three-depth (0.05 m, 0.2 m, and 0.45 m) soil thermometers (KDS-031, Komoline Aerospace Limited, Ahmedabad, India). A rain gauge of the tipping bucket type (KDS-071, Komoline Aerospace Limited, Ahmedabad, India) was placed in the open to record rainfall. A programmable 25-channel data logger (DSAWSKM1-W, Komoline Aerospace Limited, Ahmedabad, India) automatically stored these data. The data were logged every second and averaged for 30 min [12]. Batch processing of micrometeorological data was carried out to convert all sub-hourly fluxes into daily averages. Radiation balance components and ground heat flux were averaged for the daytime and for the 24 h period. 10-day (dekadal) and monthly averages of fluxes were computed from daily averages. The data quality was screened to remove spurious spikes in the instantaneous and daily averages to have smooth temporal transition [26] and to obtain reliable dekadal averages. Net radiation at the surface was computed from the four components of radiation balance as given in Equation (5). \[R\mathrm{n}=\mathrm{SW_{net}}+\mathrm{LW_{net}} \tag{5}\]  
where,  
\[\mathrm{SW_{net}}=\mathrm{SW}\downarrow-\mathrm{SW}\uparrow\]\[\mathrm{LW}_{\mathrm{net}}=\mathrm{LW}\downarrow\ -\mathrm{LW}\uparrow\]  
where, SW and LW are shortwave and longwave radiation, respectively. The symbols '\(\downarrow\)' and '\(\uparrow\)' represent incoming and outgoing fluxes, respectively. The SWnet and LWnet are net shortwave and net longwave radiation fluxes at the surface. The net radiation (\(R\)n) is partitioned into sensible heat flux (SH), latent heat flux (LE), ground heat flux (G), and metabolic and storage energy in the vegetation canopy (\(\Delta\)H). \[R\mathrm{n}=\mathrm{SH}+\mathrm{LE}+\mathrm{G}+\Delta\mathrm{H} \tag{6}\]  
G was measured following methodology adopted by [PERSON] et al. [27]. The storage heat of the canopy was ignored in the seasonal cycle, with the assumption that the amount of energy stored during the heating cycle is being released during the cooling cycle [26]. The amount of metabolic heat is usually negligible as compared to other components [26]. The net available energy (Q) was computed as:  
\[\mathrm{Q}=R\mathrm{n}-\mathrm{G} \tag{7}\]  
Latent heat flux from Bowen ratio energy balance (BREB) method was computed as:  
\[\mathrm{LE}=\frac{R\mathrm{n}-\mathrm{G}}{1+\beta} \tag{8}\]  
where: \(\beta=\frac{\mathrm{SH}}{\mathrm{LE}}=\gamma\frac{dT_{g}}{d\epsilon_{g}}\)  
The air temperature (\(\frac{dT_{g}}{dZ}\)) and vapor pressure (\(\frac{d\epsilon_{g}}{dZ}\)) gradients can be determined through multi-height measurements within the surface layer (or quasi-laminar boundary layer). \(\gamma\) is the psychrometric constant (0.66 mbar \({}^{\circ}\)C\({}^{-1}\)). The evaporative fraction (EF) was computed as the ratio between the evapotranspiration (LE) and the available energy (Q) at the land surface and considered as an indirect indicator that affects the C balance. It is a stable indicator of the annual dryness-wetness cycle that isolates surface control (soil moisture and vegetation) from radiation and turbulent factors (range 0 to 1).