Abstract
Feedbacks of plant phenology to the regional climate system affect fluxes of energy, water, CO2, biogenic volatile organic compounds as well as canopy conductance, surface roughness length, and are influencing the seasonality of albedo. We performed simulations with the regional climate model COSMO-CLM (CCLM) at three locations in Germany covering the period 1999 to 2015 in order to study the sensitivity of grass phenology to different environmental conditions by implementing a new phenology module. We provide new evidence that the annually-recurring standard phenology of CCLM is improved by the new calculation of leaf area index (LAI) dependent upon surface temperature, day length, and water availability. Results with the new phenology implemented in the model show a significantly higher correlation with observations than simulations with the standard phenology. The interannual variability of LAI improves the representation of vegetation in years with extremely warm winter/spring (e.g., 2007) or extremely dry summer (e.g., 2003) and shows a more realistic growth period. The effect of the newly implemented phenology on atmospheric variables is small but tends to be positive. It should be used in future applications with an extension on more plant functional types.
Highlights
Phenology is the timing of seasonal activities of animals and plants [1,2]
Phenology is affected by climate change [4,5], since the 1950s, the growing season in temperate Europe lengthened by 3.6 days per decade [2,6,7]
The first cutting is between the end of May and the beginning of June showing the first decrease of leaf area index (LAI)
Summary
Phenology is the timing of seasonal activities of animals and plants [1,2]. It indicates changes in ecology [2] which are linked to local or regional climate variability [3]. The precipitation and the available soil water are important for the variability during the phenophase [12]. Precipitation as a source for soil water has a strong influence on the development of the leaf area index (LAI, the leaf area per unit area of land [15]) especially in summer during the growing season [16]. In a year with less precipitation, there is less water available a reduction of the LAI is observed [17]
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