Date of Graduation

8-2023

Document Type

Thesis

Degree Name

Master of Science in Environmental Engineering (MSEnE)

Degree Level

Graduate

Department

Environmental Dynamics

Advisor/Mentor

Runkle, Benjamin R.

Committee Member

Naithani, Kusum J.

Second Committee Member

Tullis, Jason A.

Keywords

Arkansas; Gross primary productivity; Photosynthesis; Rice

Abstract

An estimate of the gross primary productivity (GPP) of rice fields can be instrumental to understand their harvest yield and to fulfill an array of agricultural monitoring needs. One of the most common satellite-based models to estimate GPP is the vegetation photosynthesis model (VPM). In this study, we use the VPM model for rice cropland in Arkansas and validate our findings against 16 site-years in-situ data (eddy covariance (EC)). At the site scale, results validated against 16 site-years have shown that the VPM with site information (R2 = 0.71, MAE = 2.90 g C m-2day- 1, and RMSE = 4.04 g C m-2day-1) outperforms VPM based on spatial information (R2 = 0.59, MAE = 4.9 g C m-2day-1, and RMSE = 3.48 g C m-2day-1). At the state scale, in the timeframe between 2008 to 2020, the mean photosynthetic carbon uptake of Arkansas rice fields was 1563.81± 129.09 g C m-2 season-1. The spatial distribution of GPP has shown that rice fields located between 33.5° N and 34.5° N have higher GPP values (1840.40 ± 8.34 g C m- 2 season-1) than other rice regions of Arkansas. At the county-scale, GPP has shown an R2 value of 0.07 against reported yield obtained from an agricultural survey. This GPP dataset will help to identify its underlying meteorological and soil factors, derive a relationship with yield, and investigate crop responses to a changing climate.

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