-
Mccall Weber posted an update 6 months ago
ost effective fertilizer practice for improving soil fertility and rice yield in paddy field of yellow soil in Guizhou Province.Straw returning is one of the important measures for improving soil fertility. It is unclear, however, whether the regulation function of soil on nitrogen (N) cycle after fertilization is sustainable and the relationship between the regulation function and the amount of straw returned to the field. In this study, a 3-year straw returning field trial was set up in a field had been carried out straw returning of all the havested straw for nine years. The amount of straw returned was 100%, 67%, 33% and 0 of the average annual straw yield (7500 kg·hm-2) to identify the effects of different straw returned amount on N transformation in the fertilized soil (0-10 cm). Results showed that the amount of straw returning affected the production and consumption of NH4+-N and NO3–N by affecting the potential gross N transformation rate. When the amount of straw returning was less than 67%, the production rate of NH4+-N significantly reduced and the consumption rate significantly increased, and thus led to the decrease in soil NH4+-N retention capacity. The NO3–N production rate increased and the retention capacity decreased, and the NO3–N accumulation and leaching loss risk increased. Therefore, returning more than 67% of harvested straw was necessary to maintain the function of soil N conservation.The spatial distribution of the preferential flow path in soil affects the occurrence and movement of preferential flow. In afield soil staining and tracing experiment, with the help of morphological image analysis technology and community ecological analysis method, we examined the spatial distribution characteristics of preferential flow path in paddy fields under straw mulching (CM) and non-mulching (CK) in karst areas of Guangxi. The results showed that, under the same external water supply conditions, with the increases of soil depth, soil horizontal dyeing changed from overall distribution to clump aggregation distribution in paddy field under straw mulching. In the non-mulching paddy field, the main dyeing was branch, with an average shape coefficient of staining patch of 21.69. The dyeing morphology in the non-mulching paddy field was 1.04 times of straw mulching paddy field. The preferential flow paths of straw mulching and non-mulching paddy fields showed both clustered distribution. In straw mulching paddy field, the Morisita index was 1.28 as the preferential flow paths with radius of influence less than 1.0 mm were the main ones (importance value 0.31). The importance value of preferential flow paths with radius less than 1.0 mm was 0.28 in non-straw mulched rice field. Straw mulching affected the preferential flow paths in paddy fields, which could help to improve water and fertilizer utilization of crops in the field.The land cover of Bohai Rim region has changed greatly due to urbanization and economic development. Monitoring the land cover with high accuracy and real time is the most important basis for relevant researches. Traditional single-machine processing mode is difficult to realize rapid monitoring for large-scale and long-time series. The emergence of remote sensing big data makes it possible to combine computing platform and massive data. The land cover maps of study area were interpreted based on Google Earth Engine (GEE) platform with decision tree (CART) method from 2000 to 2019. The land cover change was analyzed, and the interpretation results using different data sources were compared. The results showed that the GEE platform could realize the rapid land cover interpretation in a large area, which interpreted coastal wetlands and other cover types with high accuracy over 80% comparing the surveyed points. Compared with Landsat images, the Sentinel-2A images interpretation results had a great improvement in accuracy, which increased from 85% to 95%, and thus more detailed surface information could be reflected. In 2000, the area of wetland, build-up area, farmland, forest, and water in the study area were 1612.5, 5734.9, 32074.8, 11853 and 3504.3 km2, accounting for 2.9%, 10.5%, 58.6%, 21.6% and 6.4% respectively. By 2019, wetlands had been reduced by 775.1 km2, with a decline of 40.1%; built-up area increased by 5310.5 km2 with an increasing rate of 92.6%. The area of farmland, forestland and water area decreased 1841.6, 1823.5 and 870.3 km2, with a decreasing rate of 5.7%, 24.8% and 48.1%, respectively. The coastal urbanization process caused the occupation of built-up area to other land use types, which was the main driving force of land cover change in the study area.Analyzing the characteristics of spatial-temporal evolution of habitat quality caused by land use change can provide a scientific basis for the coordinated development of regional ecological economy. With Fujian Province (the ecological civilization demonstration area of China) as an example,the InVEST model was used to evaluate the habitat quality based on the land use change data from 1980 to 2018. Further, the influencing factors were analyzed through Geodetector, and the spatial-temporal characteristics of habitat quality was analyzed by combining with the change of land use type. Bupivacaine cell line The results showed that the main land use change types included farmland translating to forest land and construction land, forest land translating to farmland, grassland and construction land, and grassland translating to forest land, which accounted for 8.4%, 14.5%, 7.6%, 17.1%, 6.4% and 31.7% of the total land use change, respectively. From 1980 to 2018, the overall habitat quality of Fujian Province was at a high level (0.6-0.8), showing a trend of habitat degradation and habitat quality reduction. The first leading factor for the spatial variation of habitat quality was the change of land use type, with the impact of socioeconomic factors on the habitat quality of coastal counties and cities being significantly higher than that of the entire region and inland counties and cities. The rapid encroachment of construction land on the surrounding forest and grassland accele-rated the degradation of habitat in coastal areas, the process of which was irreversible. The habitat degradation of central urban areas would undergo a similar process in inland area, but might be slower than coastal area in terms of speed and scale. In the long term, the speed of habitat degradation could be slowed by controlling the scale of cities, developing urban ecological greening, and buil-ding an ecological security pattern.