覆盖材料和方式对模拟旱作党参播种出苗与成苗的影响

目的:探寻较好的旱地党参播种覆盖新型材料及其覆盖技术,为党参规范化种植提供新的技术支撑。方法:研究不同颜色(黑色、绿色)、不同密度(3针、4针、6针)遮阳网和不同覆盖方式(单层、双层覆盖)对模拟旱作党参播种出苗与成苗特性的影响。结果:不同颜色、不同密度遮阳网及不同覆盖方式对党参播种出苗与成苗特性以及播种田地面环境均有不同的影响。黑色遮阳网覆盖效应显著好于绿色遮阳网。同在黑色遮阳网覆盖条件下,党参播种田出苗早晚、出苗整齐度、0~20 cm土层土壤湿度与杂草防除效应基本随遮阳网遮光度的增加而提早或提高,但幼苗生长势、种苗产量与群体质量水平并不随遮阳网遮光度的增加呈渐增或渐降趋势。结论:采用黑色3针网双层覆盖方式,党参播种出苗早、出苗整齐、单位面积优质种苗数多,并有较好的保墒防草效应,其综合效应最佳。

生物抗旱剂预处理对模拟旱作党参播种出苗与成苗的影响

以党参种子为试材,采用生物抗旱剂SK 1号和SK 2号进行浸种处理,以干种子直接播种和清水浸种处理作对照,研究了2种生物抗旱剂预处理对模拟旱作党参播种出苗与成苗特性的影响。结果表明,与干种子直接播种和清水浸种处理的对照相比较,SK 1号生物抗旱剂浸种可加速党参播种的出苗进程,增加出苗整齐度,显著提高党参播种的成苗率和种苗产量,显著提升党参种苗的群体质量水平,而对党参幼苗的支根发生无显著影响。说明SK 1号生物抗旱剂浸种对模拟旱作条件下党参播种出苗、成苗以及幼苗根系的生长均有良好作用。

覆盖材料和方式对模拟旱作秦艽播种出苗与成苗的影响

以秦艽种子为试验材料,研究了4种遮阳网地面覆盖处理(黑色3针网单层覆盖、黑色3针网双层覆盖、黑色3针网+黑色6针网混合双层覆盖、黑色2针网+黑色6针网混合双层覆盖)对模拟旱作秦艽播种出苗与成苗特性的影响。结果表明,不同覆盖处理具有明显不同的效应。黑色3针网双层覆盖和黑色3针网+黑色6针网混合双层覆盖效应最好,二者在测试的各项指标间无显著差异,均可使模拟旱作条件下秦艽播种提早出苗,显著提高秦艽种苗产量,并能显著促进秦艽幼苗地上部和地下部生长,显著提升秦艽种苗的个体质量水平。黑色3针网单层覆盖效应次之,黑色2针网+黑色6针网混合双层覆盖效应最差。

Assessing Drought Vulnerability of Bulgarian Agriculture through Model Simulations

This study assesses vulnerability of agriculture to drought, using WINISAREG model and seasonal SPI2-index for eight climate regions （1951-2004）. Results relative to Plovdiv show that in soils of large TAW （total available water） net irrigation requirements NIRs range from 0 to 380 mm. In soils of small TAW, NIRs reach 440 mm in the very dry year. NIRs in Sofia/Silistra are about 100 mm smaller than in Plovdiv while in Sandanski they are 30-110 mm larger. Rainfed maize is associated with great yield variability （29% 〈 Cv 〈 72%）. Considering an economical RYD （relative yield decrease） threshold, 32% of years are risky when TA Wis large in Plovdiv that is double than in Sofia and half than in Sandanski. In North Bulgaria the risky years are 10% in Pleven/Silistra that is half than in Lom. In Plovdiv region reliable relationships （R2 〉 91%） were found relating the SPI2 ＂July-Aug.＂ with simulated RYD of rainfed maize while remaining relationships were less accurate （73% 〈 R2 〈 86%）. Economical losses are produced when High Peak Season SPI2 〈 ＋ 0.20 in Sandanski, SPI2 〈 - 0.50 in Plovdiv and SPI2 〈 - 0.90 in Sofia. In North Bulgaria the SPI2 threshold ranges from - 0.75 to - 1.50. Derived reliable relationships and SPl-thresholds are used for drought vulnerability mapping.

Regional Simulation of Soil Organic Carbon Dynamics for Dry Farmland in East China by Coupling a 1:500000 Soil Database with the Century Model

Changes in soil organic carbon (SOC) in agricultural soils influence soil quality and greenhouse gas concentrations in the atmosphere. Dry farmland covers more than 70% of the whole cropland area in China and plays an important role in mitigating carbon dioxide (CO2) emissions. In this study, 4109 dry farmland soil polygons were extracted using spatial overlay analysis of the soil layer (1:500000) and the land use layer (1:500000) to support Century model simulations of SOC dynamics for dry farmland in Anhui Province, East China from 1980 to 2008. Considering two field-validation sites, the Century model performed relatively well in modeling SOC dynamics for dry farmland in the province. The simulated results showed that the area-weighted mean soil organic carbon density (SOCD) of dry farmland increased from 18.77 Mg C ha1 in 1980 to 23.99 Mg C ha1 in 2008 with an average sequestration rate of 0.18 Mg C ha1 year?1. Approximately 94.9% of the total dry farmland area sequestered carbon while 5.1% had carbon lost. Over the past 29 years, the net SOC gain in dry farmland soils of the province was 19.37 Tg, with an average sequestration rate of 0.67 Tg C year1. Augmentation of SOC was primarily due to increased consumption of nitrogen fertilizer and farmyard manure. Moreover, SOC dynamics were highly differentiated among dry farmland soil groups. The integration of the Century model with a fine-scale soil database approach could be conveniently utilized as a tool for the accurate simulation of SOC dynamics at the regional scale.

Estimation of key surface parameters in semi-arid region and their impacts on improvement of surface fluxes simulation

Uncertainties in some key parameters in land surface models severely restrict the improvement of model capacity for successful simulation of surface-atmosphere interaction. These key parameters are related to soil moisture and heat transfer and phy- sical processes in the vegetation canopy as well as other important aerodynamic processes. In the present study, measurements of surface-atmosphere interaction at two observation stations that are located in the typical semi-arid region of China, Tongyu Station in Jilin Province and Yuzhong Station in Gansu Province, are combined with the planetary boundary layer theory to estimate the value of two key aerodynamic parameters, i.e., surface roughness length zorn and excess resistance κB-1. Multiple parameterization schemes have been used in the study to obtain values for surface roughness length and excess resistance κB-1 at the two stations. Results indicate that Zorn has distinct seasonal and inter-annual variability. For the type of surface with low-height vegetation, there is a large difference between the default value of Zorn in the land surface model and that obtained from this study, κB-1 demonstrates a significant diurnal variation and seasonal variability. Using the modified scheme for the estimation of Zom and κB-1 in the land surface model, it is found that simulations of sensible heat flux over the semi-arid region have been greatly improved. These results suggest that it is necessary to further evaluate the default values of various parameters used in land surface models based on field measurements. The approach to combine field measurements with atmospheric boundary layer theory to retrieve realistic values for key parameters in land surface models presents a great potential in the improvement of modeling studies of surface-atmosphere interaction.