改进作物水分亏缺指数用于东北地区春玉米干旱灾变监测

为了明确不同程度、不同时段低温对棉花纤维品质的影响，该研究利用棉花延迟型低温冷害指标和灾情资料，筛选出1961－2017年间不同程度延迟型低温冷害的典型年份，在实现棉花功能结构模型CottonXL模型本地化应用的基础上，利用CottonXL模型模拟不同程度冷害对纤维品质的影响。结果表明：CottonXL模型能够较准确地模拟延迟型冷害对棉花纤维品质的影响，不同热量条件下纤维长度、纤维比强度、马克隆值模拟结果与实测值间的RMSE分别为0.7 mm、0.9 cN/tex、0.1。冷害对棉花纤维马克隆值影响最大、纤维比强度次之，对纤维长度影响最小。随冷害程度的加重纤维长度较长、纤维比强度较大且马克隆值适中的棉铃数量显著减少（P＜0.01），纤维品质整体下降。发生轻度、中度和重度冷害时，纤维长度分别下降0.8、1.4和1.5 mm，纤维比强度分别降低3.9、4.5和5.1 cN/tex，马克隆值分别降低1.0、1.2和1.4。同等程度延迟型低温冷害情况下，夏秋季低温冷害对纤维品质的影响大于春季低温冷害。轻度夏秋季型低温冷害对纤维品质的影响较中度春季型低温冷害更大。

Improved crop water deficit index for monitoring drought disaster change process of spring maize in the Northeast China

Cotton (Gossypium hirsutum) fiber quality is the key factor that determines the price of cotton and its textiles. Fiber length, strength, strength and micronaire are the main indicators of cotton fiber quality. Temperature is the most important meteorological factor that determines the fiber quality. Delayed-type chilling damage is the main meteorological disaster in cotton production in Xinjiang. And it is also the meteorological disaster that has the greatest impact on fiber quality. Quantitative evaluation of the effect of chilling damage on cotton fiber quality is of great significance for disaster assessment and formulating countermeasures. Functional-structural model of cotton (CottonXL) is a visual model that developed on GroIMP platform. It can vividly simulate the three-dimensional growth process and spatial distribution of fiber quality of cotton under different scenarios. So, the model is a powerful tool for studying the effect of climate on fiber quality. In this study, the parameters of the model were calibrated and validated by the experimental data of staged sowing. Because the quality data of stage sowing experiment were the cotton fiber on fruit branches 3 and 4, the simulated value of fiber quality of bolls on fruit braches 3 and 4 were averaged to compared with the observed data. The root mean square error (RMSE) and normalized root mean square error (NRMSE) of observed and simulated fiber length, strength and micronaire were 0.7 mm, 0.9 cN/tex, 0.1 and 2.6%, 3.2%, 3.0%, respectively. The results showed that CottonXL can accurately simulate the effects of different heat conditions on fiber quality. In order to study the effect of delayed chilling injury on cotton fiber quality in Shihezi area, the model were validated by the sample survey data of cotton fiber quality in Shihezi area from 2006 to 2011. Because the sampled data were the average value of Shihezi area, the simulated value of fiber quality of all cotton bolls in the whole plant were averaged to compared with sampled data. The RMSE and NRMSE of observed and simulated fiber length, strength and micronaire were 0.4 mm, 0.9 cN/tex, 0.1 and 1.5%, 3.1%, 1.3%, respectively. The results showed that CottonXL can accurately simulate the average value of fiber quality in Shihezi area. The typical years of delayed-type chilling damage in different degrees were selected from 1961 to 2017 by using the index of delayed chilling damage and disaster data. Based on calibration and validation of functional-structural plant model CottonXL, we simulated the effects of different degrees of chilling damage on fiber quality. The results showed chilling damage had the greatest effect on micronaire, followed by fiber strength, and had the least effect on fiber length. With the aggravation of chilling damage, the number of cotton bolls with longer fiber length, lager fiber strength and moderate micronaire decreased significantly, and the fiber quality decreased as a whole. The fiber length, strength and micronaire decreased by 0.8, 1.4 and 1.5 mm, 3.9, 4.5 and 5.1 cN/tex, 1.0, 1.2 and 1.4, respectively when mild, moderate and severe chilling damage occurred. Under the same degree of delayed chilling damage, the effect of chilling damage in summer and autumn on fiber quality was greater than that in spring. Under condition with insufficient heat, changing sowing time, cut top time and planting density could reduce losses.