Search Results (16)

Abandoned cropland has been expanding due to complex socio-economic factors such as urbanization, demographic shifts, and declining agricultural profitability. As abandoned cropland simultaneously brings ecological, environmental, and social risks and benefits, quantitative monitoring is essential to assess its overall impact. Satellite image-based spatial data are suitable for identifying spectral characteristics related to crop phenology, and recent research has advanced in detecting large-scale abandoned cropland through changes in time-series spectral characteristics. However, frequent cloud covers and highly fragmented croplands, which vary across regions and climatic conditions, still pose significant challenges for satellite-based detection. This study combined Harmonized Landsat and Sentinel-2 (HLS) imagery, offering high temporal (2–3 days) and spatial (30 m) resolution, with the eXtreme Gradient Boosting (XGBoost) algorithm to capture seasonal spectral variations among rice paddy, upland fields, and abandoned croplands. An XGBoost model with a Balanced Bagging Classifier (BBC) was used to mitigate class imbalance. The model achieved an accuracy of 0.84, $Cohen’s kappa$ 0.71, and $F2 score$ 0.84. SHapley Additive exPlanations (SHAP) analysis identified major features such as NIR (May–June), SWIR2 (January), MCARI (September), and BSI (January–April), reflecting phenological differences among cropland types. Overall, this study establishes a robust framework for large-scale cropland monitoring that can be adapted to different regional and climatic settings. Full article

Over time, the vegetation of abandoned rice paddy fields is succeeded by communities of willow (Salix pierotii Miq.). This study was carried out to confirm the potential for future carbon farming by evaluating the carbon absorption capacity of willow communities restored passively in abandoned rice paddy fields. The net primary productivity (NPP) of willow communities established in abandoned rice paddy fields in three areas of central Korea (Cheongju, Andong, and Buyeo) was determined. The NPP was obtained by combining the diameter growth of willow individuals and the density of willow stands, yielding 24.36, 19.74, and 38.69 tons·ha⁻¹·yr⁻¹, respectively, and the average NPP of the three sites was 27.62 tons·ha⁻¹·yr⁻¹. The carbon-based NPP calculated from the average NPP at the three sites was 13.81 tons·C·ha⁻¹·yr⁻¹, and the amount of heterotrophic respiration, which is the respiration of microorganisms and animals in the soil, measured in abandoned rice paddy fields in Cheongju was 5.25 tons·C·ha⁻¹·yr⁻¹. As a result, the net ecosystem production (NEP) of the willow communities established in the abandoned rice paddy fields was calculated as 8.56 tons·C·ha⁻¹·yr⁻¹. By substituting this NEP value into the area of abandoned rice paddy fields so far, the carbon dioxide absorption capacity of abandoned rice paddy fields was estimated to exceed 19 million·tons·yr⁻¹. This amount is high enough to account for 77% of the total forecasted carbon absorption capacity in 2050, which is the year Korea aims to achieve carbon neutrality. In this regard, carbon farming using abandoned rice paddy fields is evaluated as a promising project. Full article

In Japan, rural areas are grappling with population decline and aging, leading to a shortage of labor for farmland maintenance. This has resulted in the abandonment of farmland or its conversion for solar photovoltaic (PV) use. However, this unplanned conversion raises concerns about agricultural productivity decline, landscape degradation, biodiversity loss, water resource maintenance, and disaster prevention. This study focuses on the Kushida watershed, examining (1) accurate farmland classification using remote sensing data, (2) the geographical distribution of farmland converted to PV systems from 2016 to 2021 and concentrated along the river, especially on north-facing slopes, (3) the highest conversion rates in wheat fields, followed by legume fields, tea fields, and paddy fields, and (4) no clear correlation between farmland conversions and changes in the number of farmers, but associations with farmland geography and solar radiation levels. These findings contribute to a nuanced understanding of sustainable rural development in Japan, emphasizing the importance of considering geographical factors in the conversion of farmland to PV. Full article

For the study on the relationships between the seed dispersal of exotic plants and bird population, flora, avifauna, vegetation patches, and the dynamics of seed banks were investigated in and around the exposed floodplains of the large rivers, and the causes of exotic vegetation development were determined with respect to plant life form, bird population characteristics, and landscape using multivariate analysis. The number of dominant exotic plant species observed in exposed areas was higher than that observed in an abandoned field and paddy field undergoing secondary succession. Additionally, the area occupied by exotic vegetation in exposed areas increased with the increase in number of vine plants and small terrestrial birds, whereas the relationship between vine and runner plants was inversely proportional. Therefore, to control exotic plants in exposed floodplains surrounding large rivers, it is necessary to remove vines and shrubs along the waterfront where small resident birds carrying plant seeds live and to maintain and manage runner plant populations. Furthermore, implementing an ecological landscape management strategy, such as afforestation through the planting of trees, may also be effective. Full article

The Indonesian land area is 191.1 million ha, part of which is abandoned land in various agroecosystems that have the potential for expanding the agricultural area. The purpose of this research was to geospatially analyze abandoned land based on its agroecosystem at the national and district levels, as well as to evaluate the land suitability of the land for expanding agricultural development. The methods included: (1) geospatial analysis of the national land cover map at a scale of 1:250,000 combined with soil and climate information to identify abandoned land and examine its agroecosystem, (2) selecting representative districts in each agroecosystem for visual interpretation using high-resolution imagery, i.e., SPOT 6/7, (3) assessing the land suitability of abandoned land for agricultural development at the national and district levels, and (4) predicting national abandoned land and its land suitability. The essential finding is the identification of abandoned land at around 42.6 million ha in Indonesia distributed over six agroecosystems, with the widest being in dry lowland and wet climates. Then, 54 districts were selected to characterize abandoned land by using SPOT 6/7 high-resolution imagery and were interpreted visually. It was found that the abandoned land covered approximately 16.9 million ha. The distribution of abandoned land from the interpretation of satellite imagery was smaller than that of geospatial analysis due to differences in the map scale and the use of ancillary data. The identification of abandoned land from high-resolution imagery should be carried out for all regions of Indonesia to accurately map the distribution of the abandoned land and characterize the properties. However, it requires a large amount of time, cost, and facilities to complete the inventory. The geospatial analysis that combined imageries and ancillary data identified 27.7 million ha of abandoned land suitable for expanding the agricultural area. The largest suitable abandoned land for the purpose was found in the lowlands with a wet climate, especially in Papua, Kalimantan, and Sumatra islands. The identified suitable abandoned land of 54 districts differed by scale, in which it was 11.2 million ha at the scale of 1:250,000 and 8.5 million ha at the scale of 1:50,000, respectively. The potential land expansion for food crops, particularly paddy fields, was only 2.2 million ha, located in mineral swamp land, which was predominantly located in Papua, with inadequate accessibility. Expanding paddy fields for national food security in the future would be constrained by less suitable land resources, while the near future challenge is the competition of land allocation for agricultural and non-agricultural sectors, as well as for food crops and plantations. Full article

The vegetation changes in the abandoned rice fields with different abandonment histories were analyzed across the country of South Korea. The successional process was confirmed by changes in vegetation profiles and species composition. The vegetation profile showed the process of starting with grassland, passing through the shrub stage, and turning into a tree-dominated forest. DCA ordination based on vegetation data showed that the process began with grasslands consisting of Persicaria thunbergii, Juncus effusus var. decipiens, Phalaris arundinacea, etc., then partially went through shrubland stages consisting of Salix gracilistyla, S. integra, young Salix koreensis, etc., and ultimately changed to a Salix koreensis dominated forest. In order to study the relationship between the succession process of the abandoned rice paddies and riparian vegetation, information on riparian vegetation was collected in the same watershed as the abandoned rice paddies investigated. Riparian vegetation tended to be distributed in the order of grasslands consisting of Phragmites japonica, Miscanthus sacchariflorus, P. arundinacea, etc., shrubland dominated by Salix gracilistyla, S. integra, etc., and a S. koreensis community dominated forest by reflecting the flooding regime as far away from the waterway. The result of stand ordination based on the riparian vegetation data also reflected the trend. From this result, we confirmed that the temporal sequence of the vegetation change that occurred in the abandoned rice fields resembled the spatial distribution of the riparian vegetation. Consequently, succession of the abandoned rice fields restored the riparian forest, which has almost disappeared in Korea and other Asian countries that use rice as their staple food. Full article

The agricultural landscape patterns of fishing village have undergone visible transformations in recent decades. Scholars pay less attention to fishermen with diverse livelihoods. Therefore, it is necessary to sort out the changing characteristics of fishermen’ livelihoods and agricultural landscape patterns under different policy periods. We use in-depth interviews, remote sensing technology, and mathematical analysis to systematically study the changes in fishermen’s livelihoods and in agricultural landscape patterns in a typical fishing village. The results show that policy have profoundly affected fishermen’ livelihoods. Livelihood transformation have altered local land use practices, which had a direct impact on agricultural landscape patterns. The livelihood of fishermen has changed from diverse to single, and their cropping structure were gradually becoming simpler and more specialised. After grazing ban and comprehensive fishing ban, many fishermen migrated to towns and cities, it accelerated the loss of population in the fishing village, which caused the amount of abandoned land increasingly. Left-behind fishermen became rice farmers by contracting abandoned paddy fields. The expanses of abandoned land and bamboo woodland had increased, which caused agricultural landscape patterns gradually becoming fragmented, heterogeneous and complex. Full article

Agricultural land use may deteriorate soil bacterial diversity and function in an agroecosystem. This study aimed to explore the impact of agricultural disturbance on the taxonomic and functional diversity of soil bacteria using a high-throughput sequencing method. We examined the bacterial community diversity in five types of flooded soils in the Hanon Maar Crater from two types of canals characterized by different nutrient levels and three field types with a different rice cultivation history. Proteobacteria (43.2%), Chloroflexi (19.8%), Acidobacteria (15.8%), Actinobacteria (5.1%), and Nitrospirae (5.0%) were the dominant phyla (>5%). The relative abundance of Actinobacteria was 7.1 times greater in the abandoned fields than in the polluted canal. Alpha diversity indices of taxonomic diversity showed strong negative correlations with C, N, and NH₄⁺ levels. The 1.7-fold greater number of operational taxonomic units (OTUs) in abandoned fields than in paddy fields may be caused by factors other than nutrients. Functional analysis revealed that 11 putative functions, including cellulolysis and ligninolysis, were significantly affected by soil management. Functional diversity indices showed negative correlations with electrical conductivity (EC) and NH₄⁺. Nitrogen input had a greater effect on bacterial taxonomic diversity than on functional diversity. Available P was positively correlated with the diversity indices. Taken together, these results suggest that keeping land fallow for more than 5 years and monitoring of C, N, and P levels are practical approaches for restoring taxonomic diversity but not functional diversity of soil bacteria. Our study demonstrated a decoupled response of taxonomic and functional diversity to rice cultivation, highlighting the necessity of further studies on the impact of decoupling on the stability of ecosystem functioning. Full article

In Timor-Leste, most paddy fields are abandoned after rice harvest due to limited water resources for another rice production cycle, particularly in lowland coastal areas. There is substantial scope for including legumes and other crops in the rice–fallow system in Timor-Leste. This study investigated the adaptation of grain legumes to terminal drought. The experiment was undertaken in 2018 and 2019 at field sites in Vemase and Laleia, respectively, on the northeast coast of Timor-Leste. The experiments used a split-plot design with two factors (water treatment and species) and three blocks (Vemase site) or four blocks (Laleia site). In 2018, the water treatments were well-watered control (W0), water withheld from flower initiation to maturity (W1), and water withheld after seedling establishment to maturity (W2). In 2019, the water treatments were well-watered control (W0) and water withheld from flower initiation to maturity (W1). Grain legumes were mungbean and soybean tested against grass pea (cv. Ceora), a well-known drought-adapted grain legume. The measured parameters included soil water content, crop phenology, plant growth and development, yield and yield components. The experiments revealed that mungbean is the most suitable grain legume crop after rice harvest under moderate drought conditions, while soybean is the preferred option under severe drought. Grass pea could be the best adaptive grain legume under severe drought in Timor-Leste when combined with the worsening conditions of climate change. Full article

Water shortages have an important impact on the photosynthetic capacity of Phragmites australis. However, this impact has not been adequately studied from the perspective of photosynthesis. An in-depth study of the photosynthetic process can help in better understanding the impact of water shortages on the photosynthetic capacity of P. australis, especially on the microscale. The aim of this study is to explore the photosynthetic adaptation strategies to environmental changes in saline‒alkaline wetlands. The light response curves and CO₂ response curves of P. australis in five habitats (hygrophilous, xerophytic, psammophytic, abandoned farmland, paddy field drainage) in saline‒alkaline wetlands were measured at different stages of their life history, and we used a nonrectangular hyperbolic model to fit the data. It was concluded that P. australis utilized coping strategies that differed between the growing and breeding seasons. P. australis in abandoned farmland during the growing season had the highest apparent quantum efficiency (AQE) and photosynthetic utilization efficiency for weak light because of the dark environment. The dark respiration rate of P. australis in the drainage area of paddy fields was the lowest, and it had the highest values for photorespiration rate, maximum photosynthetic rate (Pmax), photosynthetic capacity (Pa), biomass, maximum carboxylation rate (Vcmax), and maximum electron transfer rate (Jmax). The light insensitivity of P. australis increased with the transition from growing to breeding season, and the dark respiration rate also showed a downward trend. Moreover, Vcmax and Jmax would decline when Pmax and Pa showed a declining trend, and vice versa. In other words, Vcmax and Jmax could explain changes in the photosynthetic capacity to some extent. These findings contribute to providing insights that Vcmax and Jmax can directly reflect the variation in photosynthetic capacity of P. australis under water shortages in saline‒alkaline wetlands and in other parts of world where there are problems with similarly harmful environmental conditions. Full article

The objectives of this study were to understand the characteristics of heavy metal pollution caused by mining activities on the two sides of the Shun’an river and the response of soil microorganisms to the habitats by different contamination levels and vegetation. This paper selected soil samples from the banks of the Shun’an River near the Shizishan mining area, which is at the left of the river, in Tongling, Anhui Province, China. Using Illumina MiSeq 2500 technology, we analyzed the relationship between environmental factors and microbial communities. As the distance from the mining area increased, the heavy metal comprehensive pollution and potential risk value decreased. Additionally, the pollution severity and risk value of the left bank, where the mining area lies, were generally higher than those of the right bank. Because the symmetric sampling points on both banks of the river had similar planting types, their environmental factors and microbial community structure were similar and clustered. However, under different vegetation, the paddy soils tended to have a higher nutrient content and community richness and diversity than the vegetable fields or the abandoned land. It was found that soil microbial communities in this area were mostly affected by pH and Nemerow pollution index (P_N). The pH significantly affected the abundance and structure of most microorganisms. In addition, Proteobacteria, Acidobacteria, and Bacteroidetes had significant tolerance to Zn, Pb, and Cd. By exploring the potential use of these tolerant microorganisms, we seek to provide strains and the theoretical basis for the bioremediation of areas contaminated by heavy metal. Full article

Urbanization and regional geomorphological and agricultural conditions have caused rural hollowing out and a large number of farms to be abandoned, which is a big obstacle to food security and rural industrial development. Sichuan Province is representative of national major grain producing areas and high-quality cultivated protected land in China. This paper reveals the spatial heterogeneity of farmland abandonment in the Sichuan Province. In total, 455 random sample plots were investigated to explore spatial heterogeneity of abandoned farmland in Sichuan Province. In each sample plot, farmland and abandoned farmland patches were mapped. The rate of paddy field abandonment (RPFA), the rate of non-irrigated farmland abandonment (RNFA), and the rate of farmland abandonment (RFA) were calculated as indicators of farmland abandonment. Our results reveal the spatial heterogeneity of abandoned farmland in Sichuan Province, and the clustering characteristics of spatial cold- and hot spots of the RFA. The findings from this study may have importance in rural infrastructure construction and the implementation of a rural revitalization strategy, as well as in making policies to curb abandonment of farmland. The spatial heterogeneity of farmland abandonment revealed in this study may contribute to sustaining food security and farmland protection in China. Full article

As a constructed wetland ecosystem, paddy field plays an irreplaceable role in flood storage and detention, groundwater replenishment, environmental protection, and ecological balance maintenance. New paddy field construction can give full play to the production and ecological functions of paddy field and can adjust the development structure of the agricultural industry effectively. The soil properties of shear strength and permeability, which provide a theoretical basis for engineering design, construction, and post-operation, are important indexes in the site selection of new paddy field. The shear strength and permeability properties of soils from different land use types (vegetable field, gentle slope dryland, corn field, grapery, and abandoned dryland) for engineering new paddy field construction were investigated in this study. The results showed that the soil water content had a significant effect on the soil shear strength, internal friction angle, and cohesion. The total pressure required for soil destruction decreased with increasing water content under the same vertical pressure, resulting in easier destruction of soils. The internal friction angle decreased with increasing soil water content, and the soil cohesion first increased and then decreased with increasing soil water content. Considering that paddy fields were flooded for a long time, the soil strength properties had certain water sensitivity. Effective measures must be taken to reduce the change in soil water content, so as to ensure the stability of the embankment foundation, roadside ditch foundation, and cutting slope. In addition, the influence of changing soil water content on the strength properties of paddy soils should be fully considered in engineering design and construction, and the soil bulk density at the plough pan should reach at least 1.5 g cm⁻³ or more to ensure better water retention and the anti-seepage function of paddy field. The study can provide construction technology for engineering new paddy field construction in a hilly mountainous region of southwestern China. Full article

In recent years, Japan has undergone an unprecedented increase in farmland abandonment, which not only causes serious environmental problems and rural landscape loss, but also has a significant impact on socio-economic conditions and the livelihood of Japanese farmers. Many studies have analyzed farmland abandonment and its processes and drivers at multiple scales; however, few have focused on East Asia, especially Japan, which is a heavily depopulated country in rural areas suffering from serious abandonment. Therefore, this study attempts to shed light on the spatial patterns and determinants of farmland abandonment in Japan. For this analysis, we used the former municipalities defined in 1950 at a national scale as unit samples. Consequently, the spatial patterns, characteristics and variations of farmland abandonment in Japan are displayed. As for the drivers or determinants, we adopted ordinary least squares (OLS) and geographically weighted regression (GWR) by categorizing the determinants into geographical and socio-economic aspects. We have found that, firstly, farmland abandonment in Japan exhibits a significantly uneven pattern. While taking the farmland abandonment rate as a measurement, the results demonstrate that most abandoned farmland is positively correlated with slope and is highly clustered in the Kanto, Chubu and Chugoku Shikoku regions, compared to other regions that are suitable for agricultural production, such as the Hokkaido and Tohoku regions. Secondly, the arable land ratio of self-sufficient farm households, the ratio of non-successor farm households and the number of laborers per farm household positively affect abandonment. In contrast, arable land area per farm household and paddy field density have a negative impact on abandonment. Thirdly, the determinants are spatially varied among study regions. Farmland abandonment is driven by interactions of multiple determinants and depends on specific local circumstances. Such results can contribute to the understanding of farmland abandonment in Japan, promoting the maintenance of farmland and sustainable agriculture. Full article

Soil mercury (Hg) pollution in some areas of China is a serious problem and has aroused a lot of attention on a local scale. However, there are few studies on Hg pollution on a national scale. This study collected 444 published papers during 2005–2015 on Hg concentrations in agricultural soil throughout China, under seven land uses, namely: dry land, paddy field, vegetable field, tea garden, orchard, traditional Chinese medicine field and tobacco field, to assess the spatial distribution of Hg concentration and evaluate its influence on food safety. The averaged Hg concentration (0.108 mg/kg) was higher than its background (0.065 mg/kg), but much lower than the guidelines (GB15618-1995 II) for crop production. The spatial distribution of Hg throughout China showed great variability, with some hotspots due to Hg related mining and smelting activities. According to the Environment Quality Standard for soil in China (GB15618-1995 II), 4.2% of agricultural soil should be abandoned due to Hg pollution, and 2.0% faced a high risk of Hg pollution. Full article