## 3 Methods--Field Experiment
### Other Measurements  
The following micrometeorological data were collected in both treatment and control plots: air temperature (\(T_{a}\)) and humidity from an aspirated and shielded temperature/humidity probe (model Hygroclip S3, Rotronic, Bassersdorf, Switzerland); above canopy total incoming and diffuse photosynthetic active radiation (_PAR_) using a pyranometer (model BF2, Delta-T Services, Cambridge, UK); Net radiation (_RAD\({}_{n}\)_), short and long wave downwelling and upwelling radiation streams using a 4-channel radiometer (model CNR1, Kipp & Zonen, Delft, The Netherlands); precipitation above the canopy using a tipping bucket (model TR-525-M, Texas Electronics, Dallas,  
Figure 2: Daily soil respiratory carbon loss (\(R_{s}\)) calculated from the 1 hour soil respiration measurements (points) between Control (blue), and Treatment (red) plots in 2008, 2009, and 2010 growing seasons. TX, USA). Sensors were deployed at 46 m above ground on a tower at the control plot and at 32 m on a tower at the treatment plot. Soil temperature (\(T_{s}\)), was measured at depths of 2, 7.5, 20, 50 and 100 cm below ground at each tower site (Type E Thermocouples, Campbell Scientific, Inc.); Soil water content (\(SWC\)) was measured at two points near each tower site and at two depths (7.5, 20 cm) at each point using a soil-moisture sensor (models CS615-L and CS616-L, Campbell Scientific, Inc.). For each site, soil moisture and temperature series were computed taking the spatial average along all depths and location. Above-canopy and soil observations were logged every minute and averaged to half-hour periods. The net flux of CO\({}_{2}\) between atmosphere and forest (net ecosystem exchange, \(NEE\)), the surface sensible (H) and latent (LE) heat fluxes were measured using the flux-covariance approach. Wind velocity and temperature fluctuations were sampled at 10 Hz using three-dimensional sonic anemometers (model CSAT3, Campbell Scientific, Inc.); CO\({}_{2}\) and water vapor concentrations were sampled at 10 Hz using closed-path infrared gas analyzers (IRGAs) (model LI-7000, Li-Coer Bioscience). Measurement outliers and measurements marked as faulty by the sensors' quality control variables were removed (despicked). Wind data were processed using a 3-D coordinate rotation assuming half-hourly mean vertical wind velocity is 0 and rotating the horizontal wind components toward the mean wind direction [31]. Lag time between the anemometer and scalar concentrations was calculated using the maximal covariance method [32]. The Schotanus correction [33,34] and conversion to \"real\" temperature [35] were applied to sonic anemometer measurements of temperature. Wind and concentrations observations were compiled into half-hour block averages of net fluxes following the AmeriFlux recommendations [36]. Water vapor and CO2 concentrations were adjusted using the Webb, Pearman, and [PERSON] correction [37] in a modified form derived by [PERSON] and [PERSON] [38] as a correction for the 10 Hz time series of the scalar. Observations were divided into seasons according to the carbon flux phenology in the site [39] and only observations during the growing season were used here. Data were filtered based on a seasonal frictional velocity (u*) threshold criterion [40,41], with a prescribed maximum u* threshold of 0.35 m/s [42], typical growing season u* threshold values were between 0.29 and 0.35. We used a bilinear periodic method to fill gaps in temperature, moisture, humidity, and radiation observations and assumed that CO\({}_{2}\) fluxes during nighttime were driven entirely by ecosystem respiration (\(R_{e}\)). \(R_{e}\) was calculated using site-specific empirical formulas developed for our site [30], which relate nighttime \(NEE\) to soil moisture and temperature [43]. We used this \(R_{e}\) equation to gap-fill \(NEE\) during the nighttime. Gaps in _GPP_ were filled using the mean of 100 neural network simulations [44]. Gap-filled _GPP_ was added to \(R_{e}\) to provide gap-filled \(NEE\).