Rtw 454.pdf - Google Drive

Winter snow emerges as an important driver of subsequent tree growth by regulating a range of ecosystem processes, yet these processes are often overlooked when considering the impacts of future climate on forest function. These processes include an increase in soil moisture content, which could partially compensate water loss caused by drought during the growing season (Potopova et al. 2016; Shamir et al. 2020), insulation effects of snow, which reduce winter damage to the shallow roots of trees (Blume-Werry et al. 2016; Reinmann and Templer 2016; Reinmann and Templer 2018; Wipf and Rixen 2010; Wipf et al. 2009; Reinmann et al. 2019), and regulation of the soil nutrient cycles (Wu 2018). The contributions of these different processes mediated by winter snow to tree growth are, however, heterogeneous among diverse bioclimatic regions. Increasing attention has been focused on the hydrothermal regulations of winter snow and its lagged effects on subsequent tree growth (Wang et al. 2018; Wu et al. 2018b; Zhang et al. 2017; Zhang et al. 2016a; Shamir et al. 2020), particularly in facing a warmer and drier climate regime in many temperate regions. Snow cover/depth acts as a uniquely sensitive climate variable in response to a rapidly changing climate, which depends on temperature and precipitation at a variety of temporal and spatial scales (Hamlet et al. 2005). Decreasing winter snowfall and earlier spring snowmelt in response to a near-surface warming and changing precipitation regime are seen over many parts of temperate mid-latitudes (Barnett et al. 2005). The response of tree growth to winter snow cover/depth could provide critical insight into the comprehensive and complex effects of winter climate on tree radial growth, particularly over cool temperate forests where tree growth tends to be susceptible to seasonal drought, and winter snow exhibits dramatic interannual variations.

rtw 454.pdf - Google Drive

Despite improved understanding of tree growth responses to variations in growing-season climate, little is known regarding how and to what extent winter snow will compensate for the subsequent growing-season tree growth in diverse bioclimatic regions already suffering or prone to seasonal drought stress (Ladwig et al. 2016; Zhang et al. 2018; Shamir et al. 2020; Davis and Gedalof 2018; Pederson et al. 2011). It is likely that these mechanisms balance out differently for different species and microsite environmental conditions. Preceding winter and spring precipitation play a critical role in temperate environments under dry climates (Kunz et al. 2018; Liu et al. 2013; Martin et al. 2018; Zhang et al. 2019b). However, we still lack information on the role of winter snow to store such precipitation for subsequent tree growth. Despite recent studies that found no marked compensatory effect of winter snow at regional scale across temperate China (Peng et al. 2010; Wu et al. 2019), a full picture of the potential compensation effect of winter snow on tree growth across diverse bioclimatic zones still remains elusive. One critical issue is how the compensation effect of winter snow varies along a drought gradient in semi-arid and sub-humid regions and what underlying processes drive the potential spatial divergence in such a compensation effect. We expect that the compensation effect of winter snow on tree radial growth would be more prominent under drier climate conditions. 041b061a72