Increased heat requirement for leaf flushing in temperate woody species over 1980-2012: effects of chilling, precipitation and insolation
Increased heat requirement for leaf flushing in temperate woody species over 1980-2012: effects of chilling, precipitation and insolation
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DOI：
10.1111/gcb.12863
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发表时间：
2015-07-01
影响因子：
11.6
通讯作者：
Janssens, Ivan A.
中科院分区：
文献类型：
--
作者：
Fu, Yongshuo H.;Piao, Shilong;Janssens, Ivan A.
最近的研究表明，在基于热量需求的物候模型中存在大量无法解释的变化，导致在预测生态系统碳平衡和水平衡对气候变化的响应时存在很大的不确定性。因此，迫切需要提高我们对春季物候的热量需求的理解。在这项研究中，我们估计了13个温带木本植物的叶片冲洗的长期物候观测从欧洲和北美的物种特定的热量需求。根据所有地点的平均叶片冲洗日期，将这些物种定义为早期和晚期冲洗物种。采用偏相关分析方法，研究了休眠期需热量与冷量、降水量和日射量的时间相关关系。我们发现，在1980-2012年的研究期间，叶片冲洗的热量需求增加了近50%，平均每十年增加30个热量单位。在所有物种中观察到这种时间上的增加热量的需求，但要大得多，晚于早期冲洗的物种。与以往的研究一致，我们发现，热量需求与冷量积累呈负相关。有趣的是，在去除冷积累引起的变化后，热量需求和降水量之间存在显著的正偏相关，而热量需求和太阳辐射量之间存在显著的负相关。这表明，除了众所周知的影响，寒冷，叶片冲洗的热量需求也受到降水和太阳辐射总量在休眠期间。然而，我们假设所观察到的降水和日照效应可能是人为因素，可归因于不适当的使用空气温度的热量需求量化。而不是空气温度，分生组织温度可能是叶片冲洗过程的主要驱动因素，但这些数据是不可用的。因此，需要进一步的实验研究，以验证是否日照和降水量直接影响叶片冲洗的热量需求。
Recent studies have revealed large unexplained variation in heat requirement-based phenology models, resulting in large uncertainty when predicting ecosystem carbon and water balance responses to climate variability. Improving our understanding of the heat requirement for spring phenology is thus urgently needed. In this study, we estimated the species-specific heat requirement for leaf flushing of 13 temperate woody species using long-term phenological observations from Europe and North America. The species were defined as early and late flushing species according to the mean date of leaf flushing across all sites. Partial correlation analyses were applied to determine the temporal correlations between heat requirement and chilling accumulation, precipitation and insolation sum during dormancy. We found that the heat requirement for leaf flushing increased by almost 50% over the study period 1980-2012, with an average of 30 heat units per decade. This temporal increase in heat requirement was observed in all species, but was much larger for late than for early flushing species. Consistent with previous studies, we found that the heat requirement negatively correlates with chilling accumulation. Interestingly, after removing the variation induced by chilling accumulation, a predominantly positive partial correlation exists between heat requirement and precipitation sum, and a predominantly negative correlation between heat requirement and insolation sum. This suggests that besides the well-known effect of chilling, the heat requirement for leaf flushing is also influenced by precipitation and insolation sum during dormancy. However, we hypothesize that the observed precipitation and insolation effects might be artefacts attributable to the inappropriate use of air temperature in the heat requirement quantification. Rather than air temperature, meristem temperature is probably the prominent driver of the leaf flushing process, but these data are not available. Further experimental research is thus needed to verify whether insolation and precipitation sums directly affect the heat requirement for leaf flushing.