内蒙古中西部优势植物春季返青对降水的非线性响应

Non-linear response of dominant plant species regreening to precipitation in mid-west Inner Mongolia in spring

长期以来,研究植被物候变化与气候因子的关系多基于线性模型,事实上植被物候对气候变化的响应可能是非线性的。以1984—2017年内蒙古中西部温性典型草原和温性草原化荒漠长时间序列植被物候观测资料为基础,分析了近40年来气候变化背景下不同草地类型优势植物返青期变化特征及其对春季降水的非线性响应。结果表明:(1)温性典型草原冷蒿返青期主要受水分控制,与春季降水量表现为开口向下的二次函数关系。气候暖干化导致的水分亏缺是冷蒿返青期呈极显著延迟趋势(1.32 d/a)的主要原因;春季降水量超过60 mm时,冷蒿返青期表现出由延迟转变为提前的趋势。(2)温性草原化荒漠猫头刺返青期主要受热量控制。受春季显著升温影响,猫头刺返青期呈极显著提前趋势(0.63 d/a)。春季降水增多利于猫头刺提早返青,二者表现为开口向上的二次函数关系;春季降水量超过40 mm时,猫头刺返青期对降水的响应程度逐渐降低,这可能与荒漠植物本身的生理特性有关。

The relationship between plant phenology and climate factors has been studied mostly based on linear models for a long time. In fact, the response of plant phenology to climate change may be non-linear. Based on long-time series of phenological observation data of temperate typical grassland and temperate steppe desert in Inner Mongolia from 1984 to 2017, the phenological change characteristics of dominant plant species in different grassland types and their non-linear responses to spring precipitation during the past 40 years were analyzed. The results showed that:(1) the controlling factor of Artemisia frigidawilld regreening in temperate typical grassland was water in spring, which behaved as a quadratic function of downward opening. The water deficit caused by warm and dry climate in spring was the main reason for the significantly delayed trend(1.32 d/a) of Artemisia frigidawilld regreening. Only if the precipitation in spring exceeded 60 mm, its regreening might show a transition trend from delay to advance.(2) The controlling factor of Oxytropis aciphylla regreening in temperate steppe desert was temperature. Affected by the significant warming in spring, the regreening of Oxytropis aciphylla showed a significantly advanced trend with the magnitude of 0.63 d/a. The precipitation increase in spring promoted regreening, and there was a quadratic function of upward opening between the plant regreening and spring precipitation. When the spring precipitation exceeded 40 mm, its response to precipitation gradually decreased, which was mainly related to the physiological characteristics of desert plants.