Urban agriculture is making an increasing contribution to food security in large cities around the world. The potential contribution of biodiversity to ecological intensification in urban agricultural systems has not been investigated. We present monitoring data collected from rice fields in 34 community farms in mega-urban Shanghai, China, from 2001 to 2015, and show that the presence of a border crop of soybeans and neighboring crops (maize, eggplant and Chinese cabbage), both without weed control, increased invertebrate predator abundance, decreased the abundance of pests and dependence on insecticides, and increased grain yield and economic profits. Two 2 year randomized experiments with the low and high diversity practices in the same locations confirmed these results. Our study shows that diversifying farming practices can make an important contribution to ecological intensification and the sustainable use of associated ecosystem services in an urban ecosystem.

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ABSTRACT. Deficit irrigation has been shown to increase crop water use efficiency (WUE) under certain conditions, even

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Water security in the ecotone between semi-humid and semi-arid regions (EHA) is very vulnerable and sensitive to climate change and human interferences. Urban turf irrigation is a primary consumer of urban water resources in the EHA, which places huge pressures on water security by substantial irrigated water use due to the expansion of urban turf planting. Based on a 2-year (2020–2021) turf experiment in Zhangjiakou City, a typical water-deficit city in the EHA of northern China, the water budget for turf was measured and analyzed. Furthermore, the Root Zone Water Quality Model (RZWQM2) was employed to evaluate the optimal irrigation scheme for turf. The results showed that the average volumetric water content in the 0–40 cm soil layer was maintained above 23% in 2020–2021. The evapotranspiration in growth period of turf accounted for more than 70% of the annual evapotranspiration, and the deep seepage in turf soil accounted for 49.67% and 60.28% of the total precipitation and irrigation in 2020 and 2021, respectively, during the vigorous growth period of the turf from May to September. The calibrated RZWQM2 showed a robust ability to simulate the water changes in turf. The d-values (consistency index) between the simulated and observed volumetric water contents and evapotranspiration were both greater than 0.90. In the aspects of irrigation scenarios, the T60%-12 scenario (TA-B, where A is 100%, 80%, 60% or 40% of the total irrigation amount and B is the number of irrigation events corresponding to A) was determined as the best irrigation schedule in our study area because of lower evapotranspiration, seepage and higher turf soil water storage under this irrigation scenario, also resulting from the comparison of different irrigation scenarios using the entropy-weight-TOPSIS method. In such an optimal scenario, T60%-12 irrigation treatment reduced the irrigated water requirement of turf by 40% (142.06 mm) and the seepage amount by 28.07% (39.05 mm), and had the lowest negative impacts on the turf growth.

Quantitative assessment of the effects of climate change and human activities on runoff is very important for regional sustainable water resources utilization. Determining abrupt changes in runoff could enhance identification of the main driving factors for the sudden changes. In this study, the double mass curves analysis combined with field investigation is used to determine abrupt changes in runoff in two sub-catchments of Upper Yongding River Basin(UYRB), while trend analysis via the traditional Mann-Kendall test for the period 1961-2017 is used to identify the basic trend of precipitation, temperature and potential evapotranspiration(E0). The results suggest an insignificant change in precipitation, a significant increase in temperature and a significant decline in E0 in both sub-catchments. For both of the sub-catchments, abrupt changes in runoff occurred in 1982 and 2003. Both Budyko's curve and double mass curves are used to evaluate the potential impacts of climate variability and human activities on mean annual streamflow. The results showed that, from the 1960s to the 1980s, runoff declined by 20.01% and 22.28% for Xiangshuibu and Shixiali, respectively; from the 1980s to the 2000s, runoff declined by 68.23% and 67.77% respectively. In the variation stage I (1983˜2003), human activities contributed 90.6% and 62.7% of the mean annual streamflow change in YRB and SRB, respectively. In the variation stage II(2004˜2017), human activities contributed 99.5% and 93.5% of the change in YRB and SRB, respectively. It is also noted that the first abrupt decline in runoff was actually at the beginning of China's land reform, when the land reform motivated farmers to productively manage their reallocated lands, agricultural water consumption therefore increased. The second abrupt change point occurred in 2003, when "Capital water resources planning" implemented including water conservation projects and irrigation district construction. In general, human activities, including soil and water conservation projects and water consumption, are found to be the dominant factors responsible for the significant decline in the annual streamflow in the UYRB over the last six decades.