Cropland redistribution to marginal lands undermines environmental sustainability.

Cropland redistribution to marginal land has been reported worldwide; however, the resulting impacts on environmental sustainability have not been investigated sufficiently. Here we investigated the environmental impacts of cropland redistribution in China. As a result of urbanization-induced loss of high-quality croplands in south China (∼8.5 t ha-1), croplands expanded to marginal lands in northeast (∼4.5 t ha-1) and northwest China (∼2.9 t ha-1) during 1990-2015 to pursue food security. However, the reclamation in these low-yield and ecologically vulnerable zones considerably undermined local environmental sustainability, for example increasing wind erosion (+3.47%), irrigation water consumption (+34.42%), fertilizer use (+20.02%) and decreasing natural habitats (-3.11%). Forecasts show that further reclamation in marginal lands per current policies would exacerbate environmental costs by 2050. The future cropland security risk will be remarkably intensified because of the conflict between food production and environmental sustainability. Our research suggests that globally emerging reclamation of marginal lands should be restricted and crop yield boost should be encouraged for both food security and environmental benefits.

Quantifying the response of surface urban heat island to urban greening in global north megacities.

Urban heat island, a phenomenon that urban temperature is higher than the rural area nearby, affects directly citizens' human health and well-being. However, the cooling effect from urban green space (UGS) and the attribution of the different land processes to surface urban heat island intensity (SUHI) under different background climates remains unclear. The coarse-grained model was used to estimate summer SUHI in three different background climatic zones and for seven agglomerations (BTH, JP, LD, NAAC, NAGL, YZ, UQ). Results indicate that (1) the temperate zone had the highest daytime SUHI (0-10 °C), while the arid zone has the lowest daytime SUHI (-1-2 °C). In both temperate and cold zone, the daytime SUHI was higher than the nighttime SUHI. The SUHI in downtown was higher (more than 2 °C) than in the suburbs. (2) The increasing precipitation can enhance daytime SUHI while can weaken nighttime SUHI in all three climatic zones. The increasing temperature tends to enhance SUHI in both daytime and nighttime (exclude UQ). (3) The cooling effects of UGS in daytime SUHI were highly dependent on the background climate (cold > temperate > arid). (4) The nighttime SUHI could be effectively offset when UGSFs were greater than 0.48, 0.82, 0.97, 0.95 in NAAC, NAGL, YZ, and UQ. This article highlights the different feedback of urban green space to UHII and supports green infrastructure intervention as an effective means of reducing urban heat stress at urban agglomeration scales.

Large-scale rain-fed to paddy farmland conversion modified land-surface thermal properties in Cold China.

The recent acute evolution of cropland structure in Cold China could lead to rapid rice paddy expansion, potentially altering land-surface thermal processes and influencing climate. To address the issue, this study investigated the changes in cropland type, land-surface temperature (LST) and heat fluxes in the agricultural region of Cold China during 2000-2015 based on time-series of land-use data and MODIS LST product, using the split-window algorithms (SWA) model and the pixel component arranging and component algorithm (PCACA). The investigation revealed large-scale land transformation from rain-fed farmland to paddy field in Cold China during 2000-2015. Compared to the rain-fed farmland, lower LST was observed in paddy field throughout crop growing seasons, with the highest LST threshold found in June (7.17 ± 1.05 °C) and the lowest value found in August (1.04 ± 0.35 °C). The cooling effect of paddy-field ranged from 0.59 ± 0.06 °C, 0.77 ± 0.07 °C, and 1.08 ± 0.08 °C for the low-, medium-, and high-density paddies, respectively. Compared to other months, stronger cooling effect was found in May and June. Further analysis showed the conversion of a rain-fed farmland to paddy field reduced the sensible heat flux and soil heat flux by 52.94 W/m2 and 15.26 W/m2, respectively, while increased the latent heat flux and net radiation by 115.66 W/m2 and 47.34 W/m2, respectively. The findings from this study indicated the changes in cropland structure and management regime (e.g., irrigation) could profoundly modify land-surface thermal processes and local/regional climate, interfering the signals from global warming. Therefore, instrumental climate data that collected from areas experienced large-scale conversion between rain-fed and paddy farmland should be carefully screened and corrected to prevent land-use induced biases.

A comparative analysis of urban impervious surface and green space and their dynamics among 318 different size cities in China in the past 25 years.

Urban impervious surface (UIS) and urban green space (UGS) fractions in a city are essential indicators in supporting urban planning and management. However, little is known about the dynamics of urban expansion and the resultant UIS/UGS fraction in different size cities in China over time. We comparatively analyzed the urban expansion, UIS/UGS, and their dynamics among 318 different size cities during 1990-2015 derived from the China Land Use/cover Datasets (CLUDs) and the UIS/UGS datasets. The results indicate that the urban expansion area for the 318 cities increased by 2.32 × 104 km2 during 1990-2015, with an average growth percentage of 4.37%. Megacities experienced dramatic expansion between 1990 and 2000, and the urban expansion of large and medium cities increased rapidly in the following decade. During 2010-2015, the urban expansion of small cities notably increased. Meanwhile, the proportion of the UIS fraction in newly expanded urban land continuously decreased during 1990-2015. Compared to the other three size cities, the proportion of the UGS fraction in megacities was the highest (24.55%) in 1990 and then increased (27.99-31.97%) in newly expanded urban land during 1990-2015 due to ecological construction. Thus, more attention should be paid to the dynamics of urban expansion, especially in small cities. The proportions of UGS in large, medium, and small cities are relatively low, and urban environment needs to be improved for greenness and livability in the future.

Impacts of anthropogenic land use/cover changes on soil wind erosion in China.

Assessing the impacts of land use/cover change (LUCC) on the aeolian process is crucial for improving regional ecosystem services and sustainable development. The objective of the study were to 1) examine the spatiotemporal patterns of the soil wind erosion modulus (SWEM) in China from 1990 to 2015, and 2) reveal the contributions of LUCC to SWEM dynamics. The annual SWEM derived by the revised wind erosion equation (RWEQ) was analyzed at regional and sub-regional scales using statistical analysis. The impacts of various LUCCs on SWEM were further assessed in each county. The results showed that the regions that experienced severe wind erosion (SWEM > 50 t/(ha·a)) accounted for 8.91% of all of China. The average SWEM generally decreased by half from 1990 to 2015. Large SWEM differences were found among various land use/cover types. The SWEM from desert was two times or higher than that from sparse grass, cropland, and woodland; moreover, that of dense grass was the lowest in arid/semiarid areas. The conversion of grassland/woodland to cropland and desert expansion during 1990-2000 induced a net increase in total soil wind erosion of approximately 1205 × 104 t. With the implementation of ecological projects starting in the early 2000s, woodland/grassland was reconverted from cropland, and the eco-restoration of sparse grass and desert induced a net decrease in wind erosion of 278 × 104 t. All these indicated that anthropogenic activities in ecological projects had positive impacts in terms of reducing aeolian erosion intensity. We suggest that eco-restoration should be protected and consolidated in the future. Adaptive management is required to control wind erosion and improve ecosystem services and human wellbeing for people in China.

Divergent changes in cropping patterns and their effects on grain production under different agro-ecosystems over high latitudes in China.

Drastic rice paddy expansion and rapid upland crop loss have occurred over high latitudes in China, which would affect national food security. Different agro-ecosystems (i.e., state farms guided by the central government for agriculture and private farms guided by individual farmers for agriculture) could lead to different agricultural land use patterns; but this topic has not been investigated, which has limited our understanding of the dynamics of cropping patterns (i.e., rice paddies and upland crops) under different agro-ecosystems and their effect on total grain production. Thus, this study examined these issues over high latitudes in China. The results showed that: the developed methodology for determining cropping patterns presented high accuracy (over 90%). Based on the cropping pattern data, first, a satellite evidence of substantial increase in rice paddies with the loss of upland crops was found, and the large-scale conversion from upland crops to rice paddies has become the principal land use changes during the period of 2000-2015. Second, the new phenomenon was observed with rice paddies in state farms expanding at faster rates (at proportions of 12.98%-70.11%) than those in private farms (4.86%-30.48%). Third, the conversion of upland crops into rice paddies contributed 10.69% of the net increase in grain, which played a significant role in ensuring food security. The study provided new evidence of different changes in cropping patterns under different agro-ecosystems, thereby affecting rice cropping pattern and total grain production. This information is important for understanding and guiding the response to food sustainability and environmental issues.

Mapping Water Vulnerability of the Yangtze River Basin: 1994-2013.

A holistic understanding of the magnitude and long-term trend of water vulnerability is essential for making management decisions in a given river basin. Existing procedures to assess the spatiotemporal dynamic of water vulnerability in complex mega-scale river basins are inadequate; a new method named ensemble hydrologic assessment was proposed in this study, which allows collection of data and knowledge about many aspects of water resources to be synthesized in a useful way for vulnerability assessment. The objective of this study is to illustrate the practical utility of such an integrated approach in examining water vulnerability in the Yangtze River Basin. Overall, the results demonstrated that the ensemble hydrologic assessment model could largely explain the spatiotemporal evolution of water vulnerability. This paper improves understanding of the status and trends of water resources in the Yangtze River Basin.

Impacts of impervious surface expansion on soil organic carbon--a spatially explicit study.

The rapid expansion of impervious surface areas (ISA) threatens soil organic carbon (SOC) pools in urbanized areas globally. The paucity of field observations on SOC under ISA (SOCISA), especially in dryland areas has limited our ability to assess the ecological impacts of ISA expansion. Based on systematically measured SOCISA (0-80 cm depth) of a dryland city, and land-use and land-cover change data derived from remotely sensed data, we investigated the magnitude and vertical/horizontal patterns of SOCISA and mapped the impact of ISA expansion on SOC storage. The mean SOCISA in the city was 5.36 ± 0.51 kg C m(-2), lower than that observed in humid cities but much higher than that assumed in many regional carbon assessments. SOCISA decreased linearly as the soil depth or the horizontal distance from the open area increased. SOCISA accounted for over half of the city's SOC stock, which decreased by 16% (primarily in the converted croplands) because of ISA expansion from 1990 to 2010. The impacts of the ISA expansion varied spatially, depending on the land- use and converted land-cover type.

[Dynamic aspects of corneal lymphatic vessels after keratoplasty in rats].

OBJECTIVE: To study the development of lymphatic vessels after keratoplasty and to explore the molecular mechanisms of corneal lymphangiogenesis in transplanted corneas. METHODS: Experimental research. The development of corneal lymphangiogenesis was examined by LYVE-1 immunohistochemistry and whole mount immunofluorescence 1, 3, 7, 10, 14, 30 and 60 days after corneal transplantation, then lymphatic vessels counting (LVC)was evaluated. The expression of vascular endothelial growth factor-C (VEGF-C) in transplanted corneas was examined by immunohistochemistry, enzyme-linked immunosorbent assay (ELISA), and real time-PCR at same time. In addition, the inflammatory index (IF) was recorded at each time point. The association of VEGF-C and IF with LVC in transplanted corneas was examined. Analysis of the significance of differences between two groups was performed using paired Student's t-test. Pearson's analysis was used to analyze the correlation between VEGF-C, IF and LVC. RESULTS: Corneal lymphangiogenesis occurred in the stroma with LVC (1.8 ± 0.3) on Day 3, then developed and reached the peak with LVC (9.1 ± 1.5) on Day 14 after corneal transplantation. Both VEGF-C protein and mRNA up-regulated dramatically in rat transplanted corneas. The immunoreactivity reached the peak on the 3(rd) day and the 14(th) day after keratoplasty. Compared with the expression of VEGF-C mRNA (1.62 ± 0.08 copies/g) on Day 3, the expression of VEGF-C mRNA (2.48 ± 0.03 copies/g) significantly increased 14 days after the transplantation (t = 4.296, P = 0.02). LVC was strongly and positively correlated with IF (r = 0.55, P = 0.003) and the expression of VEGF-C mRNA (r = 0.51, P = 0.003). CONCLUSIONS: Corneal lymphangiogenesis correlates closely with corneal inflammation. The increased expression of VEGF-C in the cornea may be one of the important molecular mechanisms in the occurrence of corneal lymphangiogenesis after keratoplasty.

Spatio-temporal pattern and rationality of land reclamation and cropland abandonment in mid-eastern Inner Mongolia of China in 1990-2005.

The Mid-eastern Inner Mongolia of China, a typical agro-pastoral transitional zone, has undergone rapid agricultural land use changes including land reclamation and cropland abandonment in past decades due to growing population and food demand, climatic variability, and land use policy such as the "Grain for Green" Project (GFG Project). It is significant to the regional ecology and sustainability to examine the pattern and its rationality of land use change. The processes of land reclamation and cropland abandonment were accessed by using land use change dataset for four periods of 1990, 1995, 2000, and 2005, derived from the interpretation of Landsat TM images. And then the rationality of land reclamation and cropland abandonment was analyzed based on the habitat suitability for cultivation. The results indicated that: (1) land reclamation was the dominant form of agricultural land use change from 1990 to 2005, the total cropland area increased from 64,954.64 km(2) in 1990 to 76,258.51 km(2) in 2005; However, the speed of land reclamation decreased while cropland abandonment increased around 2000. The Land Reclamation Degree decreased from 1995-2000 to 2000-2005, meanwhile, Cropland Abandonment Degree increased. (2) As for the habitat suitability levels, moderately and marginally suitable levels had largest areas where cropland was widespread. Pattern of agricultural land use trended to become more rational due to the decrease of land reclamation area in low suitable levels and the increase of cropland abandonment in unsuitable area after 2000. (3) The habitat suitability-based rationality analysis of agricultural land use implicated that the GFG Project should take cultivation habitat suitability assessment into account.

Corneal lymphangiogenesis correlates closely with hemangiogenesis after keratoplasty.

AIM: To examine the relationship between corneal lymphangiogenesis and hemangiogenesis after keratoplasty. METHODS: Nineteen human corneas were obtained from 19 patients undergoing a second corneal transplantation in Zhongshan Ophthalmic Center in 2005. Blood and lymphatic vessels in human transplanted corneas were identified by lymphatic vessel endothelial receptor (LYVE-1) and platelet endothelial cell adhesion modecule-1 (PECAM-1) immunohistochemistry, and double enzyme-histochemistry; then the association of corneal blood vessel counting (BVC) with lymphatic vessel counting (LVC) was examined. RESULTS: Corneal hemangiogenesis was present in 12 cases (63%), and lymphangiogenesis occurred in 5 cases (26%) human transplanted corneas. In addition, corneal lymphangiogenesis was only present in vascularized corneas. LVC was strongly and positively correlated with BVC (r=0.725, P<0.01). CONCLUSION: Corneal lymphangiogenesis develops after keratoplasty and strongly associates with hemangiogenesis.

[The relationship between corneal lymphangiogenesis and inflammation index after corneal alkali injury].

OBJECTIVE: To discuss the relationship between corneal lymphangiogenesis and inflammation index (IF) in alkali burned corneas. METHODS: Experimental research. Rat corneal hemangiogenesis and lymphangiogenesis were examined by 5'-nase-alkaline phosphatase (5'-NA-ALP) double enzyme-histochemistry and whole mount immunofluorescence at 1 day, 3 days, and 1, 2, 3, 4, 5, 6, 7, 8 weeks after alkaline burns, and the blood vessel counting (BVC) and the lymphatic vessel counting (LVC) were recorded. The state of corneal inflammation was observed under the slit lamp and evaluated by inflammation index (IF) grading at the same time. Then, the association of LVC with IF was examined. In addition, eleven human alkali burned corneas were obtained from 11 patients undergoing corneal transplantation in Zhongshan Ophthalmic Center from January 2005 to June 2008. Corneal lymphangiogenesis was examined by lymphatic vessel endothelial receptor (LYVE-1) immunohistochemistry. The significance of the differences in IF, inflammatory cells counting, burn history, and age between two groups was analyzed by using paired student's t-test. RESULTS: New lymphatic vessels were present in rat alkali burned corneas. Corneal lymphangiogenesis developed 3 days after alkaline burns, reached the top 2 weeks after the injury, then decreased gradually, and disappeared at the end of the 5th week. Corneal lymphatics occurred behind corneal inflammation, but disappeared before corneal inflammation and hemangiogenesis. LVC was strongly and positively correlated with IF (r = 0.572, P < 0.01) after corneal alkaline burns. Among eleven human alkali burned corneas, corneal lymphatic vessels were present in 3 corneas. Compared with the other 8 cases without corneal lymphangiogenesis, the scores of IF was significantly higher (t = 3.28, P < 0.05), the inflammatory cells counting dramatically increased (t = 2.42, P < 0.05), but the age decreased significantly (t = 2.62, P < 0.05). However, the difference in burn history between two groups was not significant (t = 1.28, P > 0.05). CONCLUSION: Corneal lymphangiogenesis develops after alkaline-burns and correlates closely with inflammation index.

[Down-regulation of vascular endothelial growth factor in human retinal pigment epithelial cells by small hairpin loop RNA targeting hypoxia inducible factor-1 alpha under hypoxia condition].

OBJECTIVE: To explore the effect of hypoxia inducible factor-1 alpha (HIF-1 alpha) gene on the expression of vascular endothelial growth factor (VEGF) in human retinal pigment epithelial (hRPE) cells under hypoxia conditions by using small hairpin loop RNA (shRNA) to silence HIF-1 alpha. METHODS: CoCl(2) (150 micromol/L) was used to simulate the hypoxia environment for hRPE cells. After choosing a target site of HIF-1 alpha mRNA, shRNA was designed and synthesized by this target site. hRPE cells were transfected by this shRNA in vitro. Then, these cells were cultured under hypoxia conditions (150 micromol/L CoCl(2)). The mRNA expression of HIF-1 alpha and VEGF was measured by semi-quantitative reverse transcription PCR (RT-PCR). The protein level of HIF-1 alpha and VEGF was studied by western blot analysis. RESULTS: After hRPE cells were transfected by HIF-1 alpha-specific shRNA, RT-PCR showed that the expression of HIF-1 alpha mRNA was inhibited by 77.1%, and western blot analysis showed that the level of HIF-1 alpha protein was significantly decreased in hRPE cells under hypoxia conditions. Moreover, the expression of VEGF mRNA was inhibited by 27.8% and the level of VEGF protein was also significantly decreased in transfected hRPE cells under hypoxia conditions. CONCLUSIONS: Under hypoxia conditions, HIF-1 alpha-specific shRNA effectively keeps HIF-1 alpha gene silenced, and consequently down-regulates VEGF expression against hypoxia. These results suggest that HIF-1 alpha is one of the most important cytokines for retinal neovascularization.

[Quantification of oxygen-induced retinopathy in the mouse].

PURPOSE: To establish a quantifying model of retinal neovascularization suitable for examining pathogenesis and therapeutic intervention for the retinal neovascularization. METHODS: Sixty 7-day-old C57BL/6J mice were divided into oxygen-induced retinopathy group and control group. In oxygen-induced retinopathy group, 32 mice were exposed to (75 +/- 2)% oxygen for 5 days and then to room air; in control group, 32 mice were raised in room air. The retinal frozen sections were stained with griffonia simplicifolia lectin B4 (GSA) which selectively stained vascular cells; or the retinal preparation perfused with fluorescein-dextran were used to test the areas of the retinal neovascularization. RESULTS: After 5 days of exposure to hyperoxia at postnatal day 12 (P12), the larger central radial vessels became tortuous and constricted and central perfusion became obviously decreased. After returning to room air for 2 days at P14, neovascularization was seen. This response was maximal at P17. CONCLUSION: The reproducible and quantifiable mouse model of retinal neovascularization is useful for the study of pathogenesis of retinal neovascularization and therapeutic intervention.

In vivo and in vitro inhibitory effect of amniotic extraction on neovascularization.

PURPOSE: To prepare amniotic extraction (AE) and to test its antiangiogenic effect in vivo and in vitro. METHODS: AE was prepared and diluted to 50, 100, and 200 microg/mL concentrations. Alkali burn-induced corneal neovascularization (NV) was produced and topically treated with different concentrations of AE or 0.1% dexamethasone for 7 days. Normal saline was used as a control. Corneal NV was visualized by heart perfusion of Chinese ink and quantified as the percentage of corneal NV area to the whole corneal area. Human umbilical vein endothelial cells (HUVECs) were primarily cultured. The effects of AE on proliferation and tube formation of HUVECs were tested by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method and in vitro angiogenesis assay. Pigment epithelium-derived factor (PEDF) in AE was detected by Western blot. RESULTS: Relative corneal NV area in the control group was 56.6% +/- 9.9%, which was significantly reduced by 50 microg/mL AE (47.6% +/- 6.9%; P = 0.043) and 200 microg/mL AE (34.3% +/- 7.8%; P < 0.001) and by 0.1% dexamethasone (21.1% +/- 1.8%; P < 0.001). HUVEC cell proliferation was significantly decreased after treatment with AE at concentrations of 50 and 100 microg/mL compared with control (P = 0.036 and 0.001, respectively). The tube formation was significantly suppressed by 100 microg/mL AE (70.03% +/- 4.35%) compared with control (100% +/- 4.84%; P = 0.002). No expression of PEDF was detected in AE. CONCLUSION: AE inhibits NV induced by alkali burn. This effect may be elicited at least in part through the inhibiting activity of blood vessel endothelial cells and is not associated with PEDF.

Plasminogen kringle 5 inhibits alkali-burn-induced corneal neovascularization.

PURPOSE: Plasminogen kringle 5 (K5) is a potent angiogenic inhibitor. The purpose of the present study was to evaluate the therapeutic effect of K5 on alkali-burn-induced corneal neovascularization (NV) and to investigate its mechanism of action. METHODS: Corneal NV was induced in rabbits by NaOH. The rabbits received eye drops containing K5 or vehicle alone, four times per day. Corneal NV and inflammation were monitored every other day with a slit lamp microscope, and the length of the vessels in the cornea and the area of NV were measured. Vascular endothelial growth factor (VEGF) was determined by immunohistochemical and Western blot analyses. The TUNEL assay was used to assess the apoptosis of endothelial cells. The effects of K5 on primary bovine aortic endothelial cells (BAECs) were determined by MTT assay, flow cytometry, transmission electron microscopy, and DNA fragmentation assay. RESULTS: Alkali-burn-induced progressive corneal NV and inflammation in the cornea. K5 delayed the onset of corneal NV (P < 0.05) and decreased NV areas (P < 0.05) in a dose-dependent manner. K5 treatment, after the formation of corneal NV, induced regression of newly formatted vessels in the cornea. K5 decreased the inflammatory index in the corneas at different time points after the alkali burn. Corneal VEGF levels were reduced by K5 treatment. K5 inhibits proliferation and induces apoptosis in BAECs. CONCLUSIONS: Topical application of K5 may have therapeutic potential for the chemical burn-induced corneal NV and inflammation. The inhibitory effect of K5 on corneal NV may be by downregulation of VEGF expression.