Urban expansion dynamic and its potential effects on dry-wet circumstances in China's national-level agricultural districts.

Although urbanization has been widely examined in individual city and urban agglomeration scales, urban expansion patterns and dynamics in large-scale agricultural districts remain absent. In this study, multifaceted characteristics in urban expansion were quantified in China's nine national-level agricultural districts, and responses of dry-wet circumstances to urban sprawl were evaluated. From 1980 to 2018, China has undergone an extensive urban sprawl. Huang-Huai-Hai Plain (HHHP) has the maximum urban coverage extent, followed by Middle-lower Yangtze Plain (MLYP) and Southern China (SC). The largest annual increase was recorded in MLYP, reaching 816.12 km2; followed by HHHP, with an annual increase of 725.22 km2. There are prominent heterogeneities in expansion rate and direction among various districts. The dominating growth patterns were edge- and leapfrogging-expansion, accompanying by a less percentage of infilling-expansion. Accompanying by urbanization, connectedness in urban landscapes gradually improved, while separation degree decreased. Upon many occasions, holistic average dry-wet circumstances in non-urbanized areas are superior to those in urban areas, although this is not absolute for all the districts or periods. In urbanization progress, the development of leapfrogging-expansion has a potential to ameliorate dry-wet circumstances in both urban and non-urban zones, while infilling- and edge-expansion would constitute an inverse effect. In comparison to urban zones, leapfrogging-expansion would cause a more prominent effect on dry-wet environment in non-urbanized zones. Increased connectivity in urbanized landscapes would improve dry-wet environments, especially for urbanized zones. Inversely, increased spatial separated extent among urban landscapes would perform an opposite effect. This study provides a potential for understanding the dynamic features of urban expansion in large-scale agricultural districts. Moreover, the results can also provide a potential opportunity for optimizing dry-wet environments by regulating urbanization pattern and landscape configuration.

[Effects of alternate partial root-zone subsurface drip irrigation on potato yield and water use efficiency].

Field experiment was conducted to investigate the effects of alternate partial root-zone subsurface drip irrigation (APRSDI) on the physiological responses, yield, and water use efficiency of potato. Compared with conventional drip irrigation (CDI), APRSDI had less negative effects on the potato leaf photosynthesis rate (P(n)), but decreased the transpiration rate and stomatal conductance significantly. The slightly higher P(n) under CDI was at the expense of consuming more water. No significant difference was observed in the potato yield under APRSDI and CDI, but APRSDI saved the irrigation amount by 25.8% and increased the irrigation water use efficiency and total water use efficiency by 27.5% and 15.3%, respectively, suggesting that APRSDI would be a feasible water-saving irrigation technique for the planting of potato.