Autumn phenology variation in temperate grassland is a direct indicator of land degradation, and a phenology-based model has been used to simulate human-induced land degradation. It is important to reveal how environmental factors influence autumn phenology of herbaceous plants. In this study, we examined the effects of temperature, photoperiod, and soil moisture on the leaf withering date (LWD) of four herbaceous species (Xanthium sibiricum, Plantago asiatica, Iris lactea, and Taraxacum mongolicum) at 15 sites in the Inner Mongolian steppe from 1981 to 2012. Then, we developed two process-based models coupling the effects of the three factors based on an existing cold degree–days (CDD)-based model for predicting the LWD of the four species. The new models showed better accuracy than CDD model during validation. The model structure and parameters suggested that soil moisture likely influenced LWD nonlinearly and presented a multiplicative interaction with temperature and photoperiod. In addition, photoperiod had divergent effects on the accumulation of cold temperature for different species and sites. For X. sibiricum, the photoperiod only determined the start of cold temperature accumulation. Considering the carryover effect of spring phenology did not improve model performance. Our study also showed that local adaptation of plants was commonly ignored when using same parameters in model calibration with observation data from multiple sites; however, model calibrations using site-specific data were less stable, and the parameters could not be extrapolated across space. It will be necessary to establish a generalized regional model driven by both climatic and genotypic factors in future research.

中文翻译：

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土壤水分控制内蒙古草原草本植物秋季物候的重要作用

温带草原秋季物候变化是土地退化的直接指标，基于物候的模型已被用于模拟人类引起的土地退化。揭示环境因素如何影响草本植物秋季物候具有重要意义。在这项研究中，我们研究了温度、光周期和土壤水分对四种草本植物（西伯利亚苍耳、车前草、鸢尾花和蒲公英）叶片枯萎日期（LWD）的影响。) 在内蒙古草原的 15 个地点从 1981 年到 2012 年。然后，我们开发了两个基于过程的模型，基于现有的冷度 - 天 (CDD) 模型耦合了三个因素的影响，用于预测 LWD四种。新模型在验证过程中表现出比 CDD 模型更好的准确性。模型结构和参数表明，土壤水分可能对 LWD 产生非线性影响，并呈现出与温度和光周期的乘积相互作用。此外，光周期对不同物种和地点的冷温积累有不同的影响。对于X. sibiricum，光周期只决定了寒冷温度积累的开始。考虑到弹簧物候的结转效应并没有提高模型性能。我们的研究还表明，在使用来自多个站点的观测数据的模型校准中使用相同参数时，通常会忽略植物的局部适应性；然而，使用特定地点数据的模型校准不太稳定，并且无法跨空间外推参数。在未来的研究中，有必要建立一个由气候和基因型因素驱动的广义区域模型。