湖南省双季稻产量差时空分布特征

【目的】湖南省是中国主要的双季稻种植区之一,2014年湖南水稻总产量位居全国第一,在中国籼稻生产中占重要地位。研究湖南省双季稻区早稻和晚稻潜在产量特征,明确潜在产量、实际产量以及产量差时空分布特征。【方法】论文基于湖南省1981—2010年气候资料、水稻作物资料、土壤资料及产量统计资料,对ORYZA v3进行调参和验证,选用决定系数(R2)、D指标、均方根误差(RMSE)、归一化均方根误差(NRMSE)、平均绝对误差(MAE)等评价指标来评价模型调参验证的结果。然后利用调参验证后的ORYZA v3模型并结合Arc GIS软件模拟分析湖南省双季稻的潜在产量时空分布特征,再结合双季稻实际产量,分析早稻和晚稻产量差绝对值及相对值过去30年的时间变化趋势及空间分布特征,明确研究区域双季稻的产量可提升空间。【结果】(1)调参验证后的ORYZA v3模型对研究区域早稻和晚稻的出苗—穗分化、出苗—开花、出苗—成熟的时间(天数)以及产量具有较好模拟效果,可用于湖南双季稻潜在产量模拟研究。(2)1981—2010年间湖南省早稻和晚稻潜在产量呈北高南低的空间分布特征,高值区为研究区域中部的武冈和邵阳等地,低值区为南部的丘陵地区;研究区域内东部地区双季稻潜在产量稳定性略高于西部地区,早稻潜在产量稳定性高于晚稻。研究时段内早稻和晚稻潜在产量随时间呈降低趋势,且晚稻潜在产量降低速率更快。(3)研究区域内双季稻产量差空间分布差异较大。研究区域内北部地区早稻和晚稻产量差最大,表明该地区双季稻产量有较大的可提升空间;西南部地区双季稻产量差小于北部地区,且早稻产量差最小而晚稻产量差相对较大,即西南部地区晚稻产量可提升空间大于早稻。研究时段内湖南省早稻和晚稻产量差均呈缩小趋势,且晚稻的产量差缩小速率大于早稻。【结论】气候变化背景下平均气温的升高使得双季稻潜在产量呈现下降趋势,同时品种的改进、栽培技术进步及生产投入增加,实际产量不断增加,研究时段内除个别站点(道县、沅江等)外早稻和晚稻的产量差均呈减小趋势。研究表明湖南省双季稻区内早稻产量差普遍高于晚稻且其随时间缩小的速率小于晚稻,这是由于早稻生长季内日照时数增加对早稻生长发育和产量形成的正效应可以部分抵消温度升高的负效应。同时,早稻产量差呈现增加趋势的站点多于晚稻,因此湖南省双季稻产区早稻产量提升空间较晚稻大。

Spatial-Temporal Distribution of Double Cropping Rice’s Yield Gap in Hunan Province

【Objective】 Hunan is one of the main regions of double cropping rice in China, and the total rice yield was the highest in the country in 2014. This study characterized the spatial and temporal variations of the potential and reported statistical yields as well as their gaps of the early and late rice in the double cropping rice areas of Hunan province. 【Method】The historical weather (1981-2010), soil, crop growth and statistical yield data of Hunan province were collected and used to parameterize the rice model ORYZA v3 through the standardized calibration and validation processes. The performance of the model with parameters of rice cultivars was evaluated with satisfied decision coefficient (R²), D-index, root mean square error (RMSE), normalized root mean square error (NRMSE), mean absolute error (MAE) between simulated and observed values. The verified model was used to compute the potential yields in each area in the period from 1981 to 2010, and then the temporal and spatial variations of the potential yields and their gaps (in both absolute and relative value) to actual yields were characterized by using ArcGIS. 【Result】The ORYZA v3 estimations highly agree with observations in the rice development phenology and yields for both of the early and late rice in Hunan province. The verified model could be used in the study of rice potential yields in Hunan province. The spatial distribution of potential yields of early and late rice were both higher in north area than in the south area. High potential yields appeared in Wugang and Shaoyang while low-yielding area was located in hilly south area. Within the study area, the inter-year variation of the potential yields of double cropping rice was slightly higher in the eastern region than that in the western region while the stability of the early rice was higher than that of the late rice. The potential yield of double cropping rice in Hunan province presented a decreasing tendency from north to south and also from 1981 to 2010, especially more significant for the late rice. The biggest yield gap of the double cropping rice appeared in the north areas and the actual yield could be increased furthermore. The yield gaps were smaller in the south area than the north, and they were relatively larger in the late rice than in the early rice, indicating that late rice yield could be improved more in this area. During the period from 1981 to 2010, the yield gaps of double cropping rice in Hunan province decreased gradually. The reduction was more obvious in the late rice than that in the early rice.【Conclusion】The potential yields of double-cropping rice decreased as the average temperature increased under the background of climate change. Meanwhile, the actual production increased continuously due to varieties improvement, technology optimization and increase of inputs. Thus yield gaps between early rice and late rice both decreased during the study period excepted a few stations like Daoxian and Yuanjiang. The yield gaps of the early rice were generally higher than those of late rice with the lower reduction rates over the period from 1981 to 2010. The positive effect of increasing sunshine hours in the growing season of early rice could partially compensate the negative effect of temperature rise. Additionally, the yield gaps of the early rice presented an increasing trend in more areas than those in the late rice. Generally, the actual yield of early rice has a larger gap to close in the future in the double cropping rice area of Hunan province.