Northward expansion of paddy rice in northeastern Asia during 2000–2014

Dong, Jinwei; Xiao, Xiangming; Zhang, Guoren; Menarguez, Michael A.; Choi, Chang‐Yong; Qin, Yuanwei; Luo, Ping; Zhang, Y.; Moore, Berrien

doi:10.1002/2016gl068191

Cited by 63 publications

(48 citation statements)

References 40 publications

(53 reference statements)

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“…On sub-continental scales, some efforts of paddy rice mapping have been made including South Asia (Gumma et al, 2011;Xiao et al, 2006) and Southeast Asia (Bridhikitti and Overcamp, 2012;Kuenzer and Knauer, 2013), northeastern Asia (Dong et al, 2016a(Dong et al, , 2016b, as well as on the national scales, like the Landsatbased Cropland Data Layer (CDL) in the USA (Johnson and Mueller, 2010) and MODIS-based paddy rice maps of India, China and Bangladesh (Gumma et al, 2014;Sun et al, 2009;Xiao et al, 2005). A recent paddy rice map was released for monsoon Asia however, it was not validated (Fig.…”

Section: Existing Paddy Rice Maps At National or Larger Scalesmentioning

confidence: 99%

“…Based on this approach, continental scale paddy rice maps was generated, covering southern China, South Asia, and Southeast Asia by using 8-day time series MODIS data (Xiao et al, 2006(Xiao et al, , 2005. This method has attracted increasing attention and is now widely used in various geographical regions (Dong et al, , 2016a(Dong et al, , 2016bQin et al, 2015;Shi et al, 2013;Zhang et al, 2015).…”

Section: Category Four: Phenology-based Approaches Through Remote Senmentioning

confidence: 99%

“…Paddy rice mapping in tropical regions is more difficult due to the shorter growing season and more frequent cloud coverage. However, the phenology-based approach also encountered new challenges in cold temperate zones where the winter season is long, snowmelt occurs in spring, and precisely identifying the time period of the flooding and transplanting phases is vital Dong et al, 2016aDong et al, , 2016b.…”

Section: Major Characteristics Of Evolution Of Paddy Rice Mapping Metmentioning

confidence: 99%

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Evolution of regional to global paddy rice mapping methods: A review

Dong

Xiao

2016

ISPRS Journal of Photogrammetry and Remote Sensing

196

118

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a b s t r a c tPaddy rice agriculture plays an important role in various environmental issues including food security, water use, climate change, and disease transmission. However, regional and global paddy rice maps are surprisingly scarce and sporadic despite numerous efforts in paddy rice mapping algorithms and applications. With the increasing need for regional to global paddy rice maps, this paper reviewed the existing paddy rice mapping methods from the literatures ranging from the 1980s to 2015. In particular, we illustrated the evolution of these paddy rice mapping efforts, looking specifically at the future trajectory of paddy rice mapping methodologies. The biophysical features and growth phases of paddy rice were analyzed first, and feature selections for paddy rice mapping were analyzed from spectral, polarimetric, temporal, spatial, and textural aspects. We sorted out paddy rice mapping algorithms into four categories: (1) Reflectance data and image statistic-based approaches, (2) vegetation index (VI) data and enhanced image statistic-based approaches, (3) VI or RADAR backscatter-based temporal analysis approaches, and (4) phenology-based approaches through remote sensing recognition of key growth phases. The phenology-based approaches using unique features of paddy rice (e.g., transplanting) for mapping have been increasingly used in paddy rice mapping. Current applications of these phenologybased approaches generally use coarse resolution MODIS data, which involves mixed pixel issues in Asia where smallholders comprise the majority of paddy rice agriculture. The free release of Landsat archive data and the launch of Landsat 8 and Sentinel-2 are providing unprecedented opportunities to map paddy rice in fragmented landscapes with higher spatial resolution. Based on the literature review, we discussed a series of issues for large scale operational paddy rice mapping. Ó

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Section: Existing Paddy Rice Maps At National or Larger Scalesmentioning

confidence: 99%

Section: Category Four: Phenology-based Approaches Through Remote Senmentioning

confidence: 99%

Section: Major Characteristics Of Evolution Of Paddy Rice Mapping Metmentioning

confidence: 99%

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Evolution of regional to global paddy rice mapping methods: A review

Dong

Xiao

2016

ISPRS Journal of Photogrammetry and Remote Sensing

196

118

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“…A large fraction of the received energy in a rice field is distributed as latent heat flux; thus, the extent of evaporative cooling is large (Baldocchi et al., ; Harazono et al., ; Ikawa et al., ; Oue, ). As such, the spatial extent of rice fields can influence regional climate systems (Dong et al., ; Yoshida, Iizumi, Nishimori, & Yokozawa, ). However, it is not known how rice varieties with different photosynthetic capacities influence energy balance.…”

Section: Introductionmentioning

confidence: 99%

Increasing canopy photosynthesis in rice can be achieved without a large increase in water use—A model based on free‐air CO₂ enrichment

Ikawa

Chen

Sikma

et al. 2017

Global Change Biology

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Achieving higher canopy photosynthesis rates is one of the keys to increasing future crop production; however, this typically requires additional water inputs because of increased water loss through the stomata. Lowland rice canopies presently consume a large amount of water, and any further increase in water usage may significantly impact local water resources. This situation is further complicated by changing the environmental conditions such as rising atmospheric CO concentration ([CO ]). Here, we modeled and compared evapotranspiration of fully developed rice canopies of a high-yielding rice cultivar (Oryza sativa L. cv. Takanari) with a common cultivar (cv. Koshihikari) under ambient and elevated [CO ] (A-CO and E-CO , respectively) via leaf ecophysiological parameters derived from a free-air CO enrichment (FACE) experiment. Takanari had 4%-5% higher evapotranspiration than Koshihikari under both A-CO and E-CO , and E-CO decreased evapotranspiration of both varieties by 4%-6%. Therefore, if Takanari was cultivated under future [CO ] conditions, the cost for water could be maintained at the same level as for cultivating Koshihikari at current [CO ] with an increase in canopy photosynthesis by 36%. Sensitivity analyses determined that stomatal conductance was a significant physiological factor responsible for the greater canopy photosynthesis in Takanari over Koshihikari. Takanari had 30%-40% higher stomatal conductance than Koshihikari; however, the presence of high aerodynamic resistance in the natural field and lower canopy temperature of Takanari than Koshihikari resulted in the small difference in evapotranspiration. Despite the small difference in evapotranspiration between varieties, the model simulations showed that Takanari clearly decreased canopy and air temperatures within the planetary boundary layer compared to Koshihikari. Our results indicate that lowland rice varieties characterized by high-stomatal conductance can play a key role in enhancing productivity and moderating heat-induced damage to grain quality in the coming decades, without significantly increasing crop water use.

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“…Croplands have shrunk as urban areas have progressively expanded, and foreign crop imports have further expedited the decrease in cropland area (Lee et al, ). Rice paddy fields have decreased significantly since 1988, due to decreased rice consumption and a lower rice price (Dong et al, ). Upland fields also showed a decreasing trend; however, a slight increase was observed in recent years as paddy fields were converted into upland fields and greenhouse farming was increased to grow more profitable cash crops.…”

Section: Discussionmentioning

confidence: 99%

Unexpected nationwide nitrate declines in groundwater of Korea

Lee

Park

Jeon

2017

Hydrological Processes

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Elevated levels of nitrate in groundwater are an important concern for health and the environment. The overapplication of nitrogen fertilizer to croplands is one of the major sources of high nitrate content in groundwater. In this study, we analyse the nitrate concentrations in Korean groundwater based on data from groundwater quality monitoring wells (n = 1,022–2,072), which were sampled twice annually over a recent 13‐year analysis period (2001–2013). We report that groundwater nitrate levels are decreasing, despite steadily increasing groundwater use. The maximum nitrate concentration decreased from 168.91 to 48.11 mg/L, whereas the mean values also show a gradual decreasing trend. Non‐parametric Mann–Kendall tests on nitrate concentrations also confirm the decreasing trend. The nitrate decrease is more clearly evident in agricultural groundwater as compared to domestic and drinking groundwaters. This decrease of nitrate in groundwater coincides with a large decline in nitrogen fertilizer application due to reduced cropland areas, more sustainable agricultural practices, and progressive improvement of sewage disposal services. This study proposes that the long‐term adoption of best practices in agriculture has had a positive impact on groundwater nitrate control.

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Northward expansion of paddy rice in northeastern Asia during 2000–2014

Cited by 63 publications

References 40 publications

Evolution of regional to global paddy rice mapping methods: A review

Evolution of regional to global paddy rice mapping methods: A review

Increasing canopy photosynthesis in rice can be achieved without a large increase in water use—A model based on free‐air CO₂ enrichment

Unexpected nationwide nitrate declines in groundwater of Korea

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Northward expansion of paddy rice in northeastern Asia during 2000–2014

Cited by 63 publications

References 40 publications

Evolution of regional to global paddy rice mapping methods: A review

Evolution of regional to global paddy rice mapping methods: A review

Increasing canopy photosynthesis in rice can be achieved without a large increase in water use—A model based on free‐air CO2 enrichment

Unexpected nationwide nitrate declines in groundwater of Korea

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Product

Resources

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Increasing canopy photosynthesis in rice can be achieved without a large increase in water use—A model based on free‐air CO₂ enrichment