Paddy Rice Cultivation Research Articles

Mapping paddy rice with the random forest algorithm using MODIS and SMAP time series

Abstract Rice production is very important for national food security in China. Time series vegetation indices and phenology-based algorithms have been utilized to map paddy rice fields by identifying the flooding and seedling transplanting phases from multitemporal moderate-resolution (500 m to 1 km) images. Satellite imagery in other electromagnetic spectrum such as microwave region provides supplementary information about land surface characteristics such as soil moisture, which may improve the accuracy of rice mapping. In this study, we developed a method for identifying paddy rice at the regional scale based on the potential relationship between soil moisture and crop growth. Random forest classification optimized by the coordinate descent algorithm was used to generate a 500 m resolution paddy rice map with time series downscaled soil moisture based on Soil Moisture Active Passive (SMAP) images and Moderate Resolution Imaging Spectroradiometer (MODIS) images of the northern Songnen Plain in Northeast China-one of the major paddy rice cultivation regions in China. A combination of the Enhanced Vegetation Index (EVI), Land Surface Water Index (LSWI), Phenological Parameters (PH), and Soil Moisture (SM) was used to identify the rice fields during the flooding/transplanting and ripening phases. Two scenarios (EVI+LSWI+PH and EVI+LSWI+PH+SM as the input parameters) were developed to extract the paddy rice from the images. A comparison of the two identification scenarios indicated that the addition of the soil moisture to the combination achieved higher identification accuracy, especially at the junction of the different crop phases. The proposed method could be beneficial to researchers attempting to improve the accuracy of paddy rice identification at regional scale.

Wetting-drying cycles during a rice-wheat crop rotation rapidly (im)mobilize recalcitrant soil phosphorus

The residual phosphorus (P) in Hedley’s sequential fractionation procedure is considered to be a relatively stable soil P pool and unavailable for plant uptake. In the present study, we investigated the effect of wetting-drying events on the dynamics of the residual soil P fraction in a flooded rice and aerobic wheat rotation. Soils were taken from a long-term field trial after flooded (rice), and aerobic (wheat) crops were harvested. Hedley’s sequential fractionation method was used to assess the distribution of various P fractions. These changes in these P fractions were then related to Fe cycling in the soil. The residual P (H2SO4-H2O2 digested) was the dominant P fraction (37–51% of total P) in the aerobic soil under wheat, while it was decreased by 18–27% in flooded soil under rice cultivation. In contrast, the sparingly soluble Ca-bound P (HCl-Pi) increased from 25–31% under wheat cultivation to 41–50% under flooded rice (paddy) cultivation where reducing conditions are expected to prevail under submerged paddy soil conditions. The crop rotation not only altered the sparingly available P fraction but also influenced soil labile P, especially the organic P form. Compared with the rice soil, a 4-fold increase in the labile P fraction (NaHCO3-Po) was observed in wheat soil. The moderately labile P fraction (NaOH-extractable) showed a similar trend to that of labile P pool, but the increased NaOH-Po in wheat soil was relatively small. The relatively rapid change in the residual P fraction was attributed to oxidation-reduction cycles of Fe oxides between flooded (rice) and aerobic (wheat) soil conditions. Wetting and drying cycles associated with a rice-wheat crop rotation promoted the transformation of the sparingly soluble soil P fraction between crops, which was attributed to changes in soil redox conditions, particularly Fe cycling. This indicated that the rice-wheat crop rotation can draw upon the sparingly soluble P fraction for crop production, thus relying less on fertilizer-applied P.

Multi-functionality and land use dynamics in a peri-urban environment influenced by wastewater irrigation

Peri-urban areas are characterized by multifunctional land-use patterns forming a mosaic of built-up and agricultural areas. They are critical for providing food and other agricultural products, livelihood opportunities and multiple ecosystem services, which makes them transformative where urban and rural spaces blend. We analyzed land use changes in a peri-urban micro-watershed in Southern India by using Google Earth data to understand the micro-level spatio-temporal dynamics. This study aims at understanding the peri-urban agriculture and landscape changes as related to the change in use of wastewater and groundwater for irrigation. The temporal dynamics of peri-urban system including the changes in built-up, paragrass, paddy rice and vegetable cultivation, groundwater and wastewater irrigated areas in the watershed were evaluated. The detected changes indicate that, as a consequence of urban pressures, agricultural landscapes are being converted into built-up areas and, at the same time, former barren land is converted to agricultural plots. The mapped land use data are used in landscape change modelling for predicting the peri-urban agricultural dynamics and the driving factors in the watershed. Combined with the mapping and modelling approaches for land use change analysis, our results form the basis for integrated resources management in the wastewater influenced peri-urban systems.

High yield of protein-rich forage rice achieved by soil amendment with composted sewage sludge and topdressing with treated wastewater

Aiming to promote low-cost production of protein-rich forage rice and resource recycling from wastewater treatment plants, a pot experiment was conducted to assess the possibility to substitute mineral fertilizers with composted sewage sludge (CSS) with/without top-dressing with treated municipal wastewater (TWW). Results indicated that a basal application of CSS at 2.6 g N pot−1 replaced conventional mineral fertilization of 1.3 g N pot−1 to produce comparable yields with the same rice protein content, although there might be a risk of increased As concentration in rice grains. Interestingly, CSS application at a reasonable dose of 1.3 g N pot−1, followed by a topdressing with TWW resulted in 27% higher yield and 25% superior rice protein content relative to the mineral fertilization, with no risk of heavy metal(loid) accumulation in grains and in paddy soils. Here we demonstrated an appealing fertilization practice with zero use of mineral fertilizers in paddy rice cultivation, expectedly contributing towards sustainable rice farming and animal husbandry in Japan.

Influence of Water Irrigation Schemes and Seasonality on Transmission Dynamics of Opisthorchis viverrini in the Snail Intermediate Host, Bithynia siamensis goniomphalos in Rice Paddy Fields in Northeast Thailand.

Opisthorchis viverrini is a fish-borne zoonotic trematode that causes significant public health problems in Southeast Asia. Its life cycle requires Bithynia snails as the first intermediate hosts, fish, and human and/or carnivore hosts. This study assessed impacts of land use practice for rice cultivation and seasonality on the transmission dynamics of O. viverrini in Bithynia siamensis goniomphalos in rice paddy field habitats. The transmission of O. viverrini cercariae in B. s. goniomphalos was monitored at monthly intervals over a 4-year period from January 2010 to December 2013. From a total of 59,727 snails examined by standard cercarial shedding, the prevalence of O. viverrini was 0.7% (range, 0.0-4.1%). The prevalence of O. viverrini infection in B. s. goniomphalos varied with the amount of rainfall, with peaks of infection occurring in the cool-dry season, that is, after each rainy season. A shift of peak prevalence from cool-dry to hot-dry season observed in 2013 was associated with the increase in preceding water irrigation to support the production of second annual rice crop. Significant positive correlations were found between the prevalence and intensity of cercarial infection and the size of snails. Our results revealed substantial variation between years so that to have a clear understanding of the population dynamics of this complex system, studies should be conducted over an extended period (> 1 year). Results from this study highlight that water irrigation schemes in rice paddy cultivation and seasonality have a significant effect on the prevalence of O. viverrini in B. s. goniomphalos.

Adaptation of Rice to the Nordic Climate Yields Potential for Rice Cultivation at Most Northerly Site and the Organic Production of Low-Arsenic and High-Protein Rice.

There is an urgent demand for low-arsenic rice in the global market, particularly for consumption by small children. Soils in Uppsala, Sweden, contain low concentrations of arsenic (As). We hypothesize that if certain japonica paddy rice varieties can adapt to the cold climate and long day length in Uppsala and produce normal grains, such a variety could be used for organic production of low-arsenic rice for safe rice consumption. A japonica paddy rice variety, “Heijing 5,” can be cultivated in Uppsala, Sweden, after several years’ adaptation, provided that the rice plants are kept under a simple plastic cover when the temperature is below 10°C. Uppsala-adapted “Heijing 5” has a low concentration of 0.1 mg per kg and high protein content of 12.6% per dry weight in brown rice grain, meaning that it thus complies with all dietary requirements determined by the EU and other countries for small children. The high protein content is particularly good for small children in terms of nutrition. Theoretically, Uppsala-adapted “Heijing 5” can produce a yield of around 5100 kg per ha, and it has a potential for organic production. In addition, we speculate that cultivation of paddy rice can remove nitrogen and phosphorus from Swedish river water and reduce nutrient loads to the Baltic Sea and associated algae blooms.

ALLEVIATION OF SOIL SALINITY ON PHYSIOLOGICAL AND AGRONOMIC TRAITS OF RICE CULTIVARS USING Arbuscular mycorrhizal fungi AND Pseudomonas STRAINS UNDER FIELD CONDITIONS

Rice cultivation in Iran has a special place and its cultivation area is about 640,000 ha. Soil salinization is one of the most factor in reducing of grain yields and cultivation of paddy rice. Currently, half of Iran's cultivated lands (9.5 million ha) are affected by salinity, which has a major impact on crop yields. For this purpose, an field experiment conducted with the use of microorganisms (Pseudomonas putida strain S34, Pseudomonas fluorescens strain R167, Arbuscular mycorrhizal fungi (AMF) (Rhizophagus irregularis), co-inoculation of P.putida + P.fluorescens + AMF, and a non-inoculated treatment as control) on two rice cultivars (Hashemi and Gilane) in saline and normal soil in north of Iran during the 2018 and 2019. The results showed interactions of microorganisms and soil condition could alleviate the adverse effects of salinity by decreasing H2O2 (14-71% in normal soil and 44-281% in saline soil) and increasing catalase (CAT) activity (39.5-65% in Gilane and 45-61% in Hashemi), proline (17-46% in Gilane and 13.5-52% in Hashemi) and nitrogen (N) concentrations (12-27% in normal soil and 7-23% in saline soil) of leaves. Also microorganisms significantly increased tiller, panicle and grain number plant-1, and biological and grain yield (23-44.5% and 32.5-56% in normal and saline soil, respectively). Furthermore, the greatest mitigating effects were observed in treated by P.putida + P.fluorescens + AMF plants. This study indicated that P.putida + P.fluorescens + AMF synergistically mitigate harmful impacts of soil salinity in rice cultivars.

Effects of cultivation history in paddy rice on vertical water flows and related soil properties

Soil properties, especially physical properties and macropore characteristics, are controlling factors for vertical water flow in paddy fields. However, the effects of paddy rice cultivation history on vertical water flows and related soil properties have been rarely studied. The objectives were to identify the differences in soil physical properties and macropore parameters and to reveal the effects of these soil properties on vertical water flow patterns in paddy fields under different cultivation times. In this study, soil physical properties in a very young paddy field (2 y, VYPF), a young paddy field (18 y, YPF), and an old paddy field (>100 y, OPF) were analyzed. Meanwhile, macropore parameters (resolution of 0.6 mm) and vertical water flow patterns in these fields were identified by computed tomography and dye tracing experiment, respectively. As cultivation history lengthened in paddy rice, the average content of soil clay and organic carbon in the 80 cm depth soil profile increased, as did the thickness and bulk density of the plow pan. Also, macroporosity, macropore area density, macropore number density, node density, macropore angle, and hydraulic radius significantly decreased as length of cultivation age increased. As a result, differences in these soil propeties affected vertical water flow in three studied paddy fields. Steady-state infiltration rates decreased significantly in accordance with the reduced saturated hydraulic conductivity of soil cores from the plow pan; median values were 9.76 cm d−1, 2.93 cm d−1, and 0.13 cm d−1 for VYPF, YPF, and OPF, respectively. A greater abundance and distribution of a dye tracer and a higher stained area ratio under the plow pan in younger paddy fields indicated that more obvious preferential water flows occurred in VYPF and YPF than in OPF. This implied that the conversion of farmland from upland field to paddy field resulted in greater use of irrigation water and also posed a risk of groundwater pollution through increased percolation. Therefore, a longer puddling time before planting paddy rice should be conducted in paddy fields (i.e. YPF and VYPF) with a short cultivation history, which can reduce water percolation by enhancing bulk density, reducing macropores, and lowering the saturated water conductivity of the plow pan.

Developing a management-oriented simulation model of pesticide emissions for use in the life cycle assessment of paddy rice cultivation.

Management of the negative environmental impact of pesticides used in paddy fields requires the quantification of the emissions reaching relevant environmental compartments and the determination of the factors that influence such emissions. The present study is the first to develop a simulation model for estimating the fractions emitted to the air (fair), surface water (fsw), and the fractions that leach vertically (fvl) of pesticides applied in paddy fields for life cycle assessments (LCA). The emission quantification methods are based on the properties of the active ingredients of the pesticides and management aspects such as formulations (granular or liquid) and the water-holding period following application. The emission fractions of 37 pesticides used commonly in Japan were estimated using the presented model. A sensitivity analysis was conducted by adjusting parameters applied in the model to reveal their influence on the emission fractions. The parameters influencing fair included the formulation applied, while the water-holding period and waterproofing of the levee influenced fsw regardless of the formulation adopted, suggesting that local management could effectively reduce emissions to surface water. In addition, soil organic carbon content influenced fvl greatly, suggesting considerable regional variation in the emission factor. The developed model is expected to greatly improve the realism of impact assessment of pesticide in LCAs for paddy rice cultivation, considering it fills a gap in the fate model used in LCAs to estimate pesticide emissions to air, surface water, and soil in paddy fields.

Analysis of the characteristics and driving forces of water footprint productivity in paddy rice cultivation in China.

Water productivity improvement is fundamental to agricultural water use control, and the water footprint provides a new and comprehensive method for identifying the crop-water relationship. This study is intended to explore the spatiotemporal pattern and driving forces underlying the rice water footprint productivity (WFP) in China during the years 1996-2015 based on calculations of the provincial blue, green, gray, and white water footprints. The national water footprint in paddy rice cultivation was 240.97 Gm3 , and green water accounted for 43.9% of the total. The WFP was 0.795 kg m-3 and increased over time in all 30 provinces for which it was calculated. The growth rate in the northern provinces was greater than that in the southern part of the country. The WFP clustered geographically in all years observed. High-value provinces were concentrated to the south of the Yangtze River, whereas most of the provinces that showed a low WFP were distributed in the north China and northwest subregions. Precipitation and sunshine hours were the most obvious driving factors of rice WFP. The effects of agricultural input, e.g., agricultural machinery power, pesticides, and irrigation efficiency, on WFP also could not be ignored. The WFP is a comprehensive and useful index of the crop-water relationship and water-use efficiency. Improving agricultural input and irrigation technology are reliable approaches for WFP promotion. Areas in northeast China showed the most urgent need for improving the rice WFP, and the inclusion of the main grain producing areas in the Yangtze River Basin will further reduce ineffective water occupancy to improve water-use efficiency. © 2019 Society of Chemical Industry.

Weeding efficacy, crop injury and dispersion uniformity of the suspension concentrate of imazosulfuron, oxaziclomefone, pyraclonil and bromobutide in some trials of water inlet application with shortened irrigation time in paddy rice cultivation

Weeding efficacy, crop injury and dispersion uniformity of the suspension concentrate of imazosulfuron, oxaziclomefone, pyraclonil and bromobutide in some trials of water inlet application with shortened irrigation time in paddy rice cultivation

Variability in Nutritional Composition, Kernel Morphology and Cooking Quality of Selected Rice in Xingan Meng from Northeast China

Paddy rice cultivation expanded in Northeast China, and Xingan Meng of Inner Mongolia is an emerging area of rice production area. The goals of this study: i) to investigate varietal differences in levels of nutritional quality, kernel morphology and cooking quality and ii) to identify clusters of rice samples from Xingan Meng, northeast part of China. Research was conducted in Xingan Meng, China during the 2019 rice-growing season. The nutritional quality (energy, protein, carbohydrate, lipid, amylose, ash, Ca, Na, Fe, Zn, Mn), cooking quality (alkali spreading value, gel consistency) and kernel morphology (length, width, length width ratio, chalky rice percentage, chalky rice degree) were analysed. Significant difference were found across all traits. The largest variation was found for Mn, followed by Ca, Fe and Zn content. Four principal components were found that accounted for 95.14% of overall variability. Cluster analysis sorted the rice sample into four clusters based on nutritional quality, kernel morphology, and cooking quality. The findings of this study can support to demonstrate the quality of rice from Xingan Meng, northeast part of China.

A Technical-Economic Comparison between Conventional Tillage and Conservative Techniques in Paddy-Rice Production Practice in Northern Italy

In this study a technical-economic comparison was conducted to compare three different agronomic practices applied to paddy rice cultivation areas in Italy: one based on conventional tillage (CT), and two adopting conservative agriculture approaches, namely minimum tillage (MT) and no-tillage (NT). Data about production inputs (seed, fertilizers, agrochemicals, fuel) and working time were measured for each technique during the whole production season in three experimental fields. The total production costs were computed by adding the mechanization costs, calculated through the ASABE (American Society of Agricultural and Biological Engineers) EP (Engineering Practice) 496.3 methodology, and the production input costs. The results of the study highlighted a significant reduction of total costs obtained with both minimum (−16%) and no-tillage (−19%) compared to conventional tillage.

Farm size shapes friend choice amongst rice producers in China: Some evidence for the theory of network ecology

Multiple dynamics jointly determine who we befriend, however, researchers have failed to systematically assess which processes matter most under different circumstances. Here I draw on observations around how the demands of paddy rice cultivation shape social interaction to demonstrate that the relative importance of reciprocity, transitivity and generalised exchange to who rice producers choose as friends varies with the amount of agricultural land under their control. In doing so, I use unique data on farm size and friendship amongst 4713 rice-growing smallholders in 162 rural villages in Jiangxi, China along with a new technique for measuring the relative importance of effects in Stochastic Actor-Oriented Models. In line with the micro-level component of the recently advanced “theory of network ecology”, results suggest that features of an individual’s proximal environment can powerfully moderate the relative expression of network-formation mechanisms such that for some individuals, a dynamic may be expected to hold substantial sway over the process of choosing social contacts and, for others, no sway at all.

Large increases of paddy rice area, gross primary production, and grain production in Northeast China during 2000–2017

China is the largest rice producer and consumer in the world. Accurate estimations of paddy rice planting area and rice grain production is important for feeding the increasing population in China. However, Southern China had substantial losses in paddy rice area over the last three decades in those regions where paddy rice has traditionally been produced. Several studies have shown increased paddy rice area in Northeast China. Here we document the annual dynamics of paddy rice area, gross primary production (GPP), and grain production in Northeast China (Heilongjiang, Jilin and Liaoning provinces) during 2000–2017 using agricultural statistical data, satellite images, and model simulations. Annual maps derived from satellite images show that paddy rice area in Northeast China has increased by 3.68 million ha from 2000 to 2017, which is more than the total combined paddy rice area of North Korea, South Korea, and Japan. Approximately 82% of paddy rice pixels had an increase in annual GPP during 2000–2017. The expansion of paddy rice area slowed down substantially since 2015. Annual GPP from those paddy rice fields cultivated continuously over the 18 years were moderately higher than that from other paddy rice fields, which suggested that improved management practices could increase grain production in the region. There was a strong linear relationship between annual GPP and annual rice grain production in Northeast China by province and year, which illustrates the potential of using satellite-based data-driven model to track and assess grain production of paddy rice in the region. Northeast China is clearly an emerging rice production base and plays an increasing role in crop production and food security in China. However, many challenges for the further expansion and sustainable cultivation of paddy rice in Northeast China remain.

Effects of shift in growing season due to climate change on rice yield and crop water requirements

According to recent climate projections for South Korea, increases in temperature and precipitation will affect water use and crop production associated with paddy rice cultivation. Impacts are expected on crop growing season, crop varieties, and farming methods, all of which are highly vulnerable to disruption in weather conditions. Previous studies have estimated the effects on agricultural water resources according to climate change scenario, but most do not consider the growing season. In this study, changes in paddy rice yield and agricultural water requirement are estimated based on the impact of shift in growing season using a crop growth model. Future weather trends for four selected study areas in central and southern regions of South Korea were constructed using the Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios developed by the UN Intergovernmental Panel on Climate Change, and the paddy rice yields were simulated using the Crop Environment Resource Synthesis–Rice growth simulation model. Weather, soil, crop data, cultivars, and experimental data were used as model inputs. The results show a delay in the optimal transplanting date in 2100, with the date in the RCP 8.5 scenario delayed rapidly compared with the delay in RCP 4.5. In addition, paddy rice yield and growing period decrease. Consumptive water use and irrigation requirements decrease in the RCP 4.5 scenario due to increased rainfall. However, in RCP 8.5, less precipitation falls during the growing period, leading to an increase in irrigation requirements in some regions. These results are expected to be useful for paddy water management and growing season adjustment and to help establish long-term food security policies.

Effects of long-term paddy rice cultivation on soil arsenic speciation

Geochemical behavior of arsenic (As) in rice paddy soils determines the availability and mobility of As in the soils, but little is known about the long-term effects of paddy rice cultivation on As speciation in the soils. In this study, surface soil samples were collected from a rice paddy land and its adjacent dry land with similar soil properties and known cultivation histories. The soils of the paddy land and dry land contained 378 and 423 mg As kg−1, respectively. The predominant As species in the soils were investigated using As K-edge X-ray absorption spectroscopy (XAS) in combination with two sequential chemical fractionation methods. The XAS results showed that the predominant As species in the soils were As(III)- and As(V)-ferrihydrite, As(V)-goethite and scorodite. In comparison to the dry land soil, the paddy land soil contained a higher proportion of As(V)-ferrihydrite and a lower proportion of scorodite. The results of chemical fractionation revealed that As in the paddy land soil was more labile than that in the dry land soil. It is therefore suggested that long-term rice cultivation enhances the mobility and availability of As in paddy soils.

Paddy rice farming diversification with Trigona sp. in Pandeglang regency, Banten province (case study: diversification income analysis of paddy rice business with bee cultivation)

The study is aimed to determine the total income and contribution income of Trigona sp. cultivation by paddy rice farmers in Pandeglang District, Banten Province. The study location was purposively selected sub-districts at Pandeglang, Majasari, and Menes. Seven farmers who had at least 30 units of honeycomb colony and managed maximum 0,3 hectare (ha) of paddy field was used as a respondent. Data were collected using questionnaire to obtain the information and analyzed using Microsoft Excel for data analysis. The results showed that bee cultivation diversification with paddy rice business has potentially make a good income. The contribution income of bee cultivation and paddy rice business in 1 year have a rate 59.46% or Rp. 13,291,857,00 and 40.54% or Rp. 8,872,257.00, respectively with rate total income Rp. 22,164,114.00. The highest paddy rice and bee cultivation income were 10,296,000.00 and 18,568,000.00, respectively obtained by same farmer.

Agrogenic soil evolution of rice agrolandscapes

This paper describes soil chronosequence studies relating to fertility evolution of meadow-chernozemic (Gleyic Chernozem) soil of the Kuban region. The research has been conducted in the rice irrigation system of Krasnoarmeysky district, Krasnodar Krai. Over the course of 80 years with 12-year intervals, soil was sampled from pits from the plots/checks with permanent rice cultivation, or with crop rotation as well as from fallow land. Changes of morphological, physical and physico-chemical soil characteristics were studied. Rice paddy cultivation results in removal from the plow layer organic substances, carbonates, mineral elements, and silt particles, i.e. of the components responsible for stable soil development in the irrigation system. This illustrates the expression of dehumification, lessivage, and degradation soil processes with rice cultivation permanently as a monoculture or in a crop rotation during the chronosequence study. Deterioration of the soil physical condition is one of ever-increasing factors.

Climatic reconstruction at the Sannai-Maruyama site between Bond events 4 and 3\u2014implication for the collapse of the society at 4.2\u2009ka event

The Jōmon period/culture corresponds to the Neolithic period/culture in Japanese prehistory. The Sannai-Maruyama site (5.9–4.2 cal. kyr BP), the most famous, the largest, and the well-studied mid-Holocene (mid-Jōmon) archeological site inhabited by hunter-gatherers with sedentary lifestyle in northern Japan, started at early Bond event 4 and collapsed at late Bond event 3 (4.2 cal. kyr BP at the boundary between mid-Holocene, Northgrippian, and late-Holocene, Meghalayan), synchronous with the decline of the north Mesopotamian civilization and the Yangtze River civilization in China. Alkenone sea surface temperatures (SSTs), a proxy for early-midsummer SSTs, generally suggest that the early-midsummer SSTs (and atmospheric temperatures (ATs)) at 41° 00′ N, 140° 46′ E, about 20 km north to the Sannai-Maruyama site, located in Aomori Prefecture, peaked around 4.8–4.3 cal. kyr BP and showed minima at 5.9 and 4.1 cal. kyr BP. In spite of some discrepancy in short periods, this feature is consistent with that estimated from the assemblages of Ostracodas. δ18O value of benthic foraminifera of Nonionellina labradorica and Nonionella stella, alkenone production flux, and pollen assemblages could reflect annual-based temperature, which generally suggests that the climate was warmer at 6.0–4.2 cal. kyr BP, which could show the warmer environments at 6.0–5.0 cal. than expected from alkenone SST in early-midsummer. Overall, northward shift of the westerly jet, in association with a strengthened East Asian Summer Monsoon, could cause a relatively warm climate around 6.0–4.3 cal. kyr BP, when the Sannai-Maruyama site flourished. High food production density, by effective hansaibai (selective preservation or growth) in Castanea- and Aesculus-dominated forests, up to one sixth of the rice production density, could have supported high population density, resulting large community at the Sannai-Maruyama site. Cooling episode at 4.2 cal. kyr BP could have resulted in the decline of chestnut hansaibai, leading to the collapse of the site. Recent results from a compiled archeological site map suggested no large decline of the population but, instead, a dispersal to the surrounding area at 4.2 cal. kyr BP. It is consistent with ancestral population dynamics for the descendent from Jōmon people, in contrast to those from the immigrants from Far East Asia to the Japanese Archipelago with paddy rice cultivation technology after 2.9 cal. kyr BP, based on modern Japanese molecular sequences.