[Research progress on the monitoring methods of atmospheric nitrogen deposition]. / å¤§æ°”æ°®æ²‰é™ç›‘æµ‹æ–¹æ³•ç ”ç©¶è¿›å±•.

As an important component of global nitrogen (N) biogeochemical cycle, atmospheric N deposition refers to the removal process of reactive N, including oxidized N (NOy) and reduced N (NHx), from the atmosphere to earth surface through dry and wet deposition. Nitrogen deposition can exert important impacts on the structure and functioning of both terrestrial and aquatic ecosystems. Increasing N deposition poses a potential threat to natural ecosystems and human health. It is a challenge to accurately monitor the composition and flux of dry and wet N deposition in different ecosystems, using a unified technology. Here, we reviewed the research progress on monitoring methods of dry and wet N deposition in China and aboard, including micrometeorology, inferential method, model estimation, surrogate surface, precipitation collection, and ion exchange resin methods. We further discussed the advantages and disadvantages of each method in terms of its applications at regional, national, and global scales. This review would provide a methodological support to establish national monitoring network for atmospheric N deposition.

[Effects of enhanced-efficiency nitrogen fertilizers on nitrous oxide emissions from cotton field under plastic mulched drip irrigation in Xinjiang,China]. / 高效氮肥对新疆膜下滴灌棉田土壤氧化亚氮排放的影响.

The effect of enhanced-efficiency nitrogen (N) fertilizers on emissions of nitrous oxide (N2O) from the grey desert agricultural soils of Xinjiang is uncertain. In this study, the enhanced-efficiency fertilizers, polymer-coated urea (ESN), and stabilized urea with urease and nitrification inhibitors (U+I) were compared to conventional urea (U) for N2O emissions from cotton under plastic mulch drip irrigation near Urumqi, Xinjiang. ESN was added once at planting but the other treatments were added multiple times with drip irrigation during the growing season. Gas samples were collected and analyzed twice per week during the growing season, using the static chamber-chromatography methodology. The results showed that generally, ESN significantly increased soil cumulative N2O emissions during the growing season by 47%-73% compared to other treatments. In the first four months after fertilization, soil ammonium (NH4+-N) and nitrate (NO3--N) concentrations under ESN treatment were generally higher than under other treatments. Thereafter, NH4+-N and NO3--N concentrations under all treatments gradually decreased to similar levels. ESN all added at planting was likely responsible for high NH4+-N and NO3--N concentrations and highest N2O emissions. The U+I treatment reduced soil N2O emission by 9.9% in comparison with U, whereas the difference was not statistically significant. In addition, soil NO3--N contents of the U+I treatments were generally lower than those of the ESN and the U treatments. The cumulative N2O emissionsover the growing season ranged from 300 to 500 g N2O-N·hm-2, generally lower than emissions reported for other agricultural ecosystems. Drip irrigation successfully kept moisture conditions below levels for appreciable N2O emissions. Multiple applications of N via drip irrigation seemed to be effective to lower emissions than all N applied at planting. Therefore, for cotton field under plastic mulch drip irrigation in arid land of Northwest China, the benefit of enhanced efficiency N ferti-lizers on N2O mitigation is limited.

[Effects of different disturbance modes on the morphological characteristics and aboveground biomass of Alhagi sparsifolia in oasis-desert ecotone].

Taking Cele oasis at the southern fringe of Taklimakan Desert as a case, this paper studied the effects of different disturbances (burning in spring, cutting in spring, and cutting in fall) on the morphological characteristics and aboveground biomass of natural vegetation Alhagi sparsifolia in the ecotone of oasis-desert. Burning in spring decreased the A. sparsifolia plant height, crown width, and biomass significantly, being harmful to the regeneration and growth of the vegetation. Cutting in spring decreased the A. sparsifolia plant height, crown width, and biomass but increased the leaf biomass, thorn length, and thorn diameter, whereas cutting in fall decreased the plant height and crown width but increased the ramification amount and biomass of A. sparsifolia. Moderate cutting in fall could benefit the protection of A. sparsifolia at the southern fringe of Taklimakan Desert.

[Changes and analysis of soil quality under different land use types in oasis rim].

The aggravation process of oasisization leads to changes of land use type in oasis rim. In order to discuss the effects of different land use types on soil properties and soil quality, the four land use types located Cele oasis rim in south margin of Tarim Basin, which are the cotton field, orchard, and Caligonum mongolicum Turcz land use type reclaimed by people and nature state land use type covered by Alhagi sparsifolia SHAP, were selected as study object. The relative soil quality index (RI) and the soil quality synthesis index (SQI) were used to analyse the changes of soil quality between four land use types within 0-20 cm, 2040 cm, 40-60 cm soil depth, respectively. Meantime, the fractal theory was used to analyse the particle-size distribution (PSD) property of top soil under different land use types. The results indicated that there was a significant difference in the soil organic matter and total nitrogen in same soil depth between four land use types; the order ranked according to RI was same to the order ranked according to SQI in each soil depth between four land use types. The cotton field and orchard have an obviously positive effect on soil quality of the top soil, however, the soil quality of Alhagi sparsifolia SHAP land use type was gradually increasing along with the increasing soil depth. The soil properties and soil quality of Caligonum mongolicum Turcz land use type were at the lowest level according to the comparison results among all land use types, and the calculation results of PSD fractal dimension also indicated the Caligonum mongolicum Turcz land use type had the worst ability on maintaining soil fine fractions.

[Assessment of farmland soil quality under different utilization intensity in arid area].

Based on the 2005-2007 experimental data in Cele oasis in the southern margin of Tarim Basin of Xinjiang, the soil quality of four typical types of farmland with different utilization intensity, i.e., farmland with high input, farmland with normal input, newly reclaimed farmland, and farmland in oasis' interior, was analyzed and assessed by using sustainable yield index, soil improvement index, and soil quality synthesis index. Among the farmlands, there were significant differences in the contents of soil organic matter, available nitrogen, and available phosphorus. Newly reclaimed farmland had the lowest level of soil quality, while the farmland in oasis' interior had relatively higher soil quality. This study could help the reasonable exploitation and utilization of farmlands in Cele oasis, and the protection of local farmland eco-environment.