Impact assessment of urbanization on vegetation net primary productivity: A case study of the core development area in central plains urban agglomeration, China.

Rapid urbanization process has a negative or positive impact on vegetation growth. Net primary productivity (NPP) is an effective indicator to characterize vegetation growth status. Taking the core development area of the Central Plains urban agglomeration as the study area, we estimated the NPP and its change trend in the past four decades using the Carnegie-Ames-Stanford Approach (CASA) model and statistical analysis based on meteorological and multi-source remote sensing data. Meanwhile, combined with the urbanization impact framework, we further analyzed urbanization's direct and indirect impact on NPP. The results showed that the urban area increased by 2688 km2 during a high-speed urbanization process from 1983 to 2019. As a result of the intense urbanization process, a continuous NPP decrease (direct impact) can be seen, which aggravated along with the acceleration of the urban expansion, and the mean value of direct impact was 130.84 g C·m-2·a-1. Meanwhile, urbanization also had a positive impact on NPP (indirect impact). The indirect impact showed an increasing trend during urbanization with a mean value of 10.91 g C·m-2·a-1. The indirect impact was mainly related to temperature in climatic factors. The indirect impact has a seasonal heterogeneity, and high-temperature environments of urban areas are more effective in promoting vegetation growth in autumn and winter than in summer. Among different cities, high-speed development cities have higher indirect impact values than medium's and low's because of better ecological construction. This study is of great significance for understanding the impact of urbanization on vegetation growth in the Central Plains urban agglomeration area, supporting urban greening plans, and building sustainable and resilient urban agglomerations.

Impact of the Grain for Green Project on water resources and ecological water stress in the Yanhe River Basin.

The Grain for Green project (GGP), initialized by the Chinese government in 1999, has achieved substantial achievements accompanied by a decrease in surface runoff on the Loess Plateau, but the impacts of large-scale afforestation on regional water resources are uncertain. Hence, the objective of this study was to explore the impact of land use change on generalized water resources and ecological water stress using the blue and green water concepts, taking the Yanhe River Basin as the case study. The Soil and Water Assessment Tool (SWAT) was applied to quantify the green water and blue water, which are defined as generalized water resources. The ecological water requirement of vegetation (forest and grass), agricultural water footprint and virtual water flow are considered regional water requirements. The land use types of 1980 (Scenario I) and 2017 (Scenario II) were entered into the SWAT model while keeping the other parameters constant to isolate the influence of land use changes. The results show that the average annual differences in blue, green and generalized water resources were -72.08 million m3, 24.34 million m3, and -47.74 million m3, respectively, when the simulation results of Scenario II were subtracted from those of Scenario I, which shows that land use change caused by the GGP led to a decrease in blue and generalized water resources and an increase in green water resources. Surface runoff in Scenario I was more than that in Scenario II in all of the years of the study period from 1980-2017, and green water storage in Scenario I was more than that in Scenario II in all of the years of the study period except in 1998; although lateral flow in Scenario I was less than that in Scenario II except in 2000 and 2015, as was groundwater runoff in 1992, 2000 and 2015, and green water flow in 1998. Blue water flow, green water storage and green water flow in Scenario II were less than those in Scenario I in the whole basin, 12.89 percent of the basin and 99.21 percent of the basin, respectively. The total water footprint increased from 1995 to 2010 because the forest water footprint increased significantly in this period, although the agricultural water footprint and grass water footprint decreased. The ecological water stress index values had no obvious temporal change trends in either land use scenario, but the ecological water stress index in Scenario II was greater than that in Scenario I, which illustrates that the GGP led to an increase in ecological water stress from the perspective of generalized water resources.

[Dual-energy CT angiography for evaluation of internal carotid artery stenosis and occlusion].

OBJECTIVE: To compare the feasibility of bone and calcified plaque subtracted dual-energy CT angiography (CTA) with time of flight magnetic resonance angiography (TOF MRA) in evaluation of internal carotid artery atherosclerosis. METHODS: Totally 32 patients received a dual-energy CTA scan, along with a cerebral TOF MRA scan before or after CTA examination from one day to one month. Dual-energy software was used for bone and calcified plaque subtraction. Five anatomical segments were described for each internal carotid artery according to Fischer (1938). Ratings were based on a 1-4 scale for the dual-energy CTA maximum intensity projection (MIP) image: 1 not diagnostic, 2 partially diagnostic, 3 diagnostic, and 4 excellent. Lesions were categorized as mild (0-29%), moderate (30%-69%), severe (70%-99%), or occluded (no flow detected). Stenosis of internal carotid artery was evaluated based on post-subtracted CTA images and TOF MRA images. RESULTS: In 320 arterial segments, 99% of arterial segments were > or = 3 score. Grading of stenosis on dual-energy CTA agreed with grading of stenoses on MRA images in 98% of arteries. In the mild and occlusion group, the agreement was 100% respectively. In the moderate and severe group, dual-energy CTA showed more severe stenosis than MRA in 7 vessels and there was significant difference between the results from the two different modalities (Z = -3.071, P = 0.002). CONCLUSION: Dual-energy CTA can be used to assess the stenosis of internal arteries around skull base, but may exaggerate the severe stenosis of cerebral arteries compared with TOF MRA.

[Thoracic high resolution CT findings of 100 SARS patients in convalescent period].

OBJECTIVE: To study thoracic high resolution CT findings of severe acute respiratory syndrome (SARS) patients in convalescent period and the relationship between the features with laboratory and pulmonary function results. METHODS: All the 100 SARS patients who had been discharged from hospital for about 2 months underwent thoracic high resolution CT examinations. Among them, 65 also had laboratory results and 91 underwent examinations of pulmonary function. RESULTS: Forty-nine SARS patients (49.0%, 49/100) in convalescent period still had abnormal findings in CT examination. And ground-glass opacification (95.9%, 47/49) and reticular opacification (59.2%, 29/49) were common. There was no significant difference in the level of lymphocytes and CD4 cells among groups divided according to severity of CT findings (P > 0.01). Diffusing capacity for carbon monoxide (DLco%) of level 2 and 3 were statistically lower than that of level 0 (P < 0.01). CONCLUSIONS: The features of CT findings of SARS patients in convalescent period are not the same as those of patients in period of apparent manifestation. The high resolution CT can reflect pulmonary diffusing function to some degree.