[Tracing the sources of sedimentary organic matter in Nanyue small watershed based on C, N and C/N].

Losses of organic matter in agricultural watersheds result in eutrophication and land degra-dation, which not only threaten water quality and food security, but also lead to environmental problems such as the greenhouse gases emission. We used C, N and C/N as fingerprint markers to trace the sources of sedimentary organic matter at the outlet in the Nanyue small watershed. We analyzed the spatial distribution in watershed sedimentary organic matter and soils of typical land use types, including forest, paddy field, and vegetable fields.

[Responses of net assimilation rate to elevated atmospheric COand temperature at different growth stages in a double rice cropping system].

Effects of elevated atmospheric CO concentration and temperature on rice dry matter accumulation vary in planting regions and cropping systems. It remains unclear how dry matter productivity responds to factorial combination of elevated CO and temperature in the double rice cropping system of China. Field experiments were conducted using open-top chambers (OTC) to simulate different scenarios of elevated CO and/or temperature for three rotations of double rice in Jingzhou, Hubei Province.

[Key Production Process of Nitrous Oxide and Nitrogen Sources in Tuojia River].

The nitrogen (N) pollution of water is a common global problem. To understand the key production process of N O and identify the dominant N sources, Tuojia River, a typical agricultural watershed in a subtropical area, was investigated. To analyze the characteristics of dual nitrate isotopes (δN-NO,δO-NO) in water, and N isotope (δN) and carbon-nitrogen ratio (C/N) in sediment organic matter from four reaches(S1-S4), the stable isotopes method was used.

[Key pathway of methane production and characteristics of stable carbon isotope of the Tuojia River waterbody.].

This study aimed at exploring the key pathway of methane production and clarifying the composition and distribution of carbon (C) isotopes in the Tuojia River waterbody in Hunan Pro-vince. We estimated CH concentrations and fluxes of four reaches (S, S, S and S) by a two-layer diffusion model and gas chromatography. The spatial and temporal distribution of CH flux and its relationship with environmental factors were examined.

Effects of increased levels of atmospheric CO2 and high temperatures on rice growth and quality.

The increased atmospheric temperatures resulting from the increased concentration of atmospheric carbon dioxide (CO2) have had a profound influence on global rice production. China serves as an important area for producing and consuming rice. Therefore, exploring the effects of the simultaneously rising levels of atmospheric CO2 and temperatures on rice growth and quality in the future is very important.

[Effects of slow/controlled release urea on annual CH and NO emissions in paddy field].

Present study examined the influence of different types of slow/controlled release urea on rice yield and annual greenhouse gas emissions in a paddy field, and assessed the greenhouse gas intensity (GHGI, equivalent to global warming potential GWP/rice yield). The results indicated that the optimized fertilization (OPT) treatment recorded the similar yield with reduced nitrogen fertilizer (21.4%) supply compared with the farmers' fertilizer practice (FFP) treatment, and decreased the annual emissions of CH (12.

[Observation for CH4 and N2O emissions under different rates of nitrogen and phosphate fertilization in double rice fields].

Two non-CO2 greenhouse gas emissions (methane and nitrous oxide) and related environmental factors were measured within rice growing season under five treatments including non-fertilization (CK), balanced fertilization (BF), decreased nitrogen and phosphate 1 (DNP1), decreased nitrogen and phosphate 2 (DNP2) and increased nitrogen and phosphate 1 (INP) in double rice fields of red clay soil in 2009, using the method of static chamber-gas chromatograph techniques. The results showed that the average CH4 emission fluxes for treatments of BF, DNP1, DNP2 and INP were 4.57, 5.

[Grassland net primary productivity and its spatiotemporal distribution in northern Tibet: a study with CASA model].

Based on the remote sensing data, meteorological data and other related data from 1981 to 2004, the grassland net primary productivity (NPP) and its spatiotemporal distribution in Northern Tibet were analyzed by CASA (Carnegie-Ames-Stanford Approach) model. The results indicated that in the study area, the spatial distribution of grassland NPP was affected by the local water and heat conditions, and represented a horizontal zonality. From southeast to northwest, the grassland NPP reduced from 230 g C x m(-2) x a(-1) to near 0 g C x m(-2) x a(-1).