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标题：Estimation of Net Rice Production through Improved CASA Model by Addition of Soil Suitability Constant (ħα)
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作者：Raza, Syed Muhammad Hassan ; Mahmood, Syed Amer
期刊名称：Sustainability
印刷版ISSN：2071-1050
出版年度：2018
卷号：10
期号：6
页码：1-21
出版社：MDPI, Open Access Journal
摘要：Net primary production (NPP) is an important indicator of the supply of food and wood. We used a hierarchy model and real time field observations to estimate NPP using satellite imagery. Net radiation received by rice crop canopies was estimated as 27,428 Wm −2 (215.4 Wm −2 as averaged) throughout the rice cultivation period (RCP), including 23,168 Wm −2 (118.3 Wm −2 as averaged) as shortwave and 4260 Wm −2 (34.63 Wm −2 as averaged) as longwave radiation. Soil, sensible and latent heat fluxes were approximated as 3324 Wm −2 , 16,549 Wm −2 , and 7554 Wm −2 , respectively. Water stress on rice crops varied between 0.5838 and 0.1218 from the start until the end of the RCP. Biomass generation declined from 6.09–1.03 g/m 2 in the tillering and ripening stages, respectively. We added a soil suitability constant (ħα) into the Carnegie-Ames-Stanford Approach (CASA) model to achieve a more precise estimate of yield. Classification results suggest that the total area under rice cultivation was 8861 km 2 . The spatial distribution of rice cultivation as per suitability zone was: 1674 km 2 was not suitable (NS), 592 km 2 was less suitable (LS), 2210 km 2 was moderately suitable (MS) and 4385 km 2 was highly suitable (HS) soil type with ħα ranges of 0.05–0.25, 0.4–0.6, 0.7–0.75 and 0.85–0.95 of the CASA based yield, respectively. We estimated net production as 1.63 million tons, as per 0.46 ton/ha, 1.2 ton/ha 1.9 ton/ha and 2.4 ton/ha from NS, LS, MS and HS soil types, respectively. The results obtained through this improved CASA model, by addition of the constant ħα, are likely to be useful for agronomists by providing more accurate estimates of NPP.
关键词：net primary production; biomass estimation; photosynthesis; respiration; rice cultivation period; net radiation