Evaluation and estimation of canopy heat storage fluxes in an apple orchard

2023

J. Agric. Meteorol.

Self Cite

To investigate the reasons for irregular and severe decreases in net ecosystem production (NEP) in a sod-cultured apple orchard for better understanding orchard carbon dynamics, CO 2 flux observation was conducted from April to November (2013 and 2014) using two sets of eddy covariance equipment on different towers that were 15 m apart. Special attention was paid to the effect of grass mowing, which was conducted ten times during the observation period. In the latter half of, or just after the grass mowing period, gross primary production (GPP) on fine (sunny) days decreased to 50% -73% of the level before the grass mowing nine out of ten times, whereas ecosystem respiration (RE) did not decrease or slightly increased. As a result, NEP (= GPP−RE) on fine days drastically diminished after every grass mowing event. Moreover, three other moderate NEP decreases were observed, in addition to mowing events. Two of these events, which occurred 9 -10 days before apple flowering, were possibly caused by a temporal increase in the respiration of apple tree. The remaining event, which occurred immediately after the drought period, was possibly caused by the recovery of microorganism and root respirations. Moreover, in comparing the daily GPP trend in 2013 and 2014, it was apparent that meteorological conditions, such as low temperature from April to May or severe soil water deficiency and low solar radiation in the vigorous growth stage, also negatively affected the population photosynthesis of the orchard.

Section: Energy Balance Closurementioning

confidence: 99%

The effect of periodical grass mowing and various meteorological factors on CO<sub>2</sub> flux in a sod-cultured apple orchard

2023

J. Agric. Meteorol.

Self Cite

“…However, the EC method has a serious problem of energy imbalance, generally resulting in a serious underestimation of the nocturnal CO 2 efflux. We attempted to resolve this energy imbalance problem for our site (Ito et al, 2011;Ito and Ishida, 2012), but the nocturnal CO 2 efflux still remained uncertain. To overcome this problem, complemental observations of soil respiration were conducted for several EC observation sites (Flanagan and Johnson, 2005;Ohkubo et al, 2007), since the CO 2 emitted from the soil surface is the largest source of nocturnal CO 2 efflux.…”

Section: Introductionmentioning

confidence: 99%

Short- and long-term effects of soil moisture on soil respiration in an apple orchard

2016

J. Agric. Meteorol.

Self Cite

Although CO 2 flux observations by eddy covariance technique have many advantages, the nocturnal CO 2 efflux remains uncertain. To complement these observations and clarify the carbon budget/dynamics of an apple orchard, we applied an open chamber method and measured the soil respiration rate in September 2006-July 2010 for 237 days. We analyzed the temperature and moisture dependency of the soil respiration rate. The daily soil respiration rate, when normalized by soil temperature, was maximum when soil moisture was at the field capacity, and decreased linearly with the increase and decrease of the soil suction (pF). Excluding the negative effect of the pF, the exponential relationship between the daily soil respiration and the soil temperature became slightly closer, with the determination coefficient increasing from 0.76 to 0.84. The temperature sensitivity indicator Q 10 fluctuated inter-annually from 2.0 to 3.1, and seemed to depend on the soil moisture status of each year. We also constructed a mathematical model to calculate the daily soil respiration from the soil temperature and pF.

Equations to predict daily snowmelt energy in a deciduous fruit orchard

2012

Climate in Biosphere

In order to precisely evaluate the snowmelt energy at our flux observation site located in an apple orchard and thereby contribute to reliable flux observation, we derived an equation on the basis of the energy budget theory for predicting the daily snowmelt energy at the snow surface. For practical use at farmers' fruit orchards, we also derived some simpler prediction equations in which the number of meteorological elements used as explanatory variables was restricted. The optimum values of the parameters for these equations were then determined by using the data for the snow weight, monitored near the flux observation site. The accuracy of these equations was also examined.Using a theoretical equation in which five meteorological elements (daily integrated solar radiation, daily wind run, daily mean snow albedo, air temperature, and specific humidity deficit) and daily integrated clear-sky solar radiation were used as explanatory variables, we could predict the daily snowmelt energy with a root mean square error (RMSE) of 0.84 MJ·m -2 . The values of the bulk transfer coefficients for sensible and latent heat, estimated on the basis of the optimum values of the parameters for the prediction equation, were slightly smaller than but fairly agreed with those in previous studies. The prediction accuracy hardly decreased in the case of simpler equations in which wind run, specific humidity deficit, and clearsky radiation were not used as explanatory variables. However, the accuracy decreased considerably when solar radiation or snow albedo was excluded. When the daily snowmelt energy was predicted on the basis of only the mean air temperature, RMSE increased up to 1.34 MJ·m -2. For farmers' fruit orchards, it seemed desirable to predict the daily snowmelt energy on the basis of the integrated solar radiation in addition to the mean air temperature.