One inherent characteristic of both environmental data and health data is that they have a location component. This characteristic makes Geographic Information Systems (GIS) an ideal and sometimes indispensable tool for analyzing environmental and health data. Indeed, the past decade witnessed significant efforts in developing GIS tools for supporting epidemiologic research. Despite these efforts, the availability of accessible GIS tools that can be easily used by epidemiologists to link environmental and health data has remained a problem. We present a simple spatial search tool--GIS-EpiLink--that can be used to link environmental and health data when distance between an environmental site and the location of the maternal address of a case or control is used as a proxy for exposure. The tool was used in a research project and it successfully provided the necessary data for epidemiological analyses. This tool should be very useful to epidemiologists in environmental health research.

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Abstract. Variations in precipitation and atmospheric N deposition affect water and N availability in desert and thus may have significant effects on desert ecosystems. Haloxylon ammodendron is a dominant plant in Asian desert, and addressing its physiological acclimatization to the changes in precipitation and N deposition can provide insight into how desert plants adapt to extreme environments by physiological adjustment. Carbon isotope ratio (δ13C) in plants has been suggested as a sensitive long-term indicator of physiological acclimatization. Therefore, this study evaluated the effect of precipitation change and increasing atmospheric N deposition on δ13C of H. ammodendron. Furthermore, H. ammodendron is a C4 plant; whether its δ13C can indicate water use efficiency (WUE) has not been addressed. In the present study, we designed a field experiment with a completely randomized factorial combination of N and water and measured δ13C and gas exchange of H. ammodendron. Then we calculated the degree of bundle-sheath leakiness (φ) and WUE of the assimilating branches of H. ammodendron. δ13C and φ remained stable under N and water supply, while N addition, water addition and their interaction affected gas exchange and WUE in H. ammodendron. In addition, δ13C had no correlation with WUE. These results were associated with the irrelevance between δ13C and the ratio of intercellular to ambient CO2 concentration (ci / ca), which might be caused by a special value (0.37) of the degree of bundle-sheath leakiness (φ) or a lower activity of carbonic anhydrase (CA) of H. ammodendron. In conclusion, δ13C of H. ammodendron is not sensitive to global change in precipitation and atmospheric N deposition and cannot be used for indicating its WUE.

Abstract. Variations in precipitation and atmospheric N deposition affect water and N availability in desert, and thus may have significant effects on desert ecosystems. Haloxylon ammodendron is a dominant plant in Asian desert, and addressing its physiological acclimatization to the changes in precipitation and N deposition can provide an insight into how desert plants adapt extreme environment by physiological adjustment. Carbon isotope ratio (ẟ13C) in plants has been suggested as a sensitive long-term indicator of physiological acclimatization. Therefore, this study evaluated the effect of precipitation change and increasing atmospheric N depositon on ẟ13C of H. ammodendron. Furthermore, Haloxylon ammodendron is a C4 plant, whether its ẟ13C can indicate water use-efficiency (WUE) has not been addressed. In the present study, we designed a field experiment with a completely randomized factorial combination of N and water, and measured ẟ13C, gas exchange and WUE of the assimilating branches of H. ammodendron. ẟ13C in H. ammodendron remained stable under N and water supply, while N addition, water addition and their interaction affected gas exchange and WUE in H. ammodendron. In addition, ẟ13C had no correlation with WUE. This result are associated with the irrelevance between ẟ13C and ci/ca, which might be caused by a special value (0.37) of the degree of bundle-sheath leakiness (φ) or a lower activity of carbonic anhydrase (CA) of H. ammodendron. Thus, ẟ13C of H. ammodendron cannot be used for indicating its WUE.

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