Deepened winter snow cover enhances net ecosystem exchange and stabilizes plant community composition and productivity in a temperate grassland

Abstract

Global warming has greatly altered winter snowfall patterns, and there is a trend towards increasing winter snow in semi-arid regions in China. Winter snowfall is an important source of water during early spring in these water-limited ecosystems, and it can also affect nutrient supply. However, we know little about how changes in winter snowfall will affect ecosystem productivity and plant community structure during the growing season. Here, we conducted a 5-year winter snow manipulation experiment in a temperate grassland in Inner Mongolia. We measured ecosystem carbon flux from 2014 to 2018 and plant biomass and species composition from 2015 to 2018. We found that soil moisture increased under deepened winter snow in early growing season, particularly in deeper soil layers. Deepened snow increased the net ecosystem exchange of CO 2 (NEE) and reduced intra-and inter-annual variation in NEE. Deepened snow did not affect aboveground plant biomass (AGB) but significantly increased root biomass. This suggested that the enhanced NEE was allocated to the belowground, which improved water acquisition and thus contributed to greater stability in NEE in deep-snow plots. Interestingly, the AGB of grasses in the control plots declined over time, resulting in a shift towards a forb-dominated system. Similar declines in grass AGB were also observed at three other locations in the region over the same time frame and are attributed to 4 years of below-average precipitation during the growing season. By contrast, grass AGB was stabilized under deepened winter snow and plant community composition remained unchanged.Hence, our study demonstrates that increased winter snowfall may stabilize arid grassland systems by reducing resource competition, promoting coexistence between plant functional groups, which ultimately mitigates the impacts of chronic drought during the growing season. K E Y W O R D S community composition, net ecosystem exchange, plant biomass, semiarid grassland, stability, winter snow cover S U PP O RTI N G I N FO R M ATI O N Additional supporting information may be found online in the Supporting Information section. How to cite this article: Li P, Sayer EJ, Jia Z, et al. Deepened winter snow cover enhances net ecosystem exchange and stabilizes plant community composition and productivity in a temperate grassland. Glob Change Biol. 2020;26:3015-3027.

Seasonal not annual precipitation drives 8-year variability of interannual net CO2 exchange in a salt marsh

“…The result revealed that seasonal precipitation had significant influence on carbon exchange in this salt marsh. The result is consistent with the conclusion of previous studies that seasonal precipitation plays important roles in regulating annual C budget (Beier et al, 2012;Li et al, 2020b). Specially under the background of warm and dry environment (Han et al, 2018), higher temperature and decreased precipitation during the early growth will enhance soil moisture evaporation and increase soil salinity, which will influence biomass accumulation and annual C budget.…”

Deepened snow cover mitigates soil carbon loss from intensive land‐use in a semi‐arid temperate grassland

“…The experimental set‐up is described in full by Li et al. (2020). Briefly, three blocks were established along a snow fence made of polyethylene mesh, which acted as a barrier to the prevailing north‐westerly winter wind from October to March each year to increase snow depth, depending on winter precipitation levels (deep‐snow treatment).…”

“…Climate change is likely to have a major influence on soil erosion by modifying winter precipitation, which affects soil moisture status and plant growth (Li et al., 2020; Peng et al., 2010). Global warming is projected to weaken cold air surges and increase winter snow cover in cold regions (Hartmann et al., 2013; Tsunematsu et al., 2011), which can influence vegetation structure and soil exposure throughout the year.…”

“…Global warming is projected to weaken cold air surges and increase winter snow cover in cold regions (Hartmann et al., 2013; Tsunematsu et al., 2011), which can influence vegetation structure and soil exposure throughout the year. First, deepened winter snow enhances soil moisture in the spring (Dorji et al., 2013; Li et al., 2020), which directly reduces soil erodibility by promoting the formation of soil crusts and aggregates, and thus enhancing the stability of surface soil fine particles (Field et al., 2010; Webb & Strong, 2011). Second, increased spring snowmelt can promote plant growth in water‐limited regions by alleviating water and nutrient limitation in the early growing season, which enhances plant cover and above‐ground biomass throughout the growing season (Grippa et al., 2005; Li et al., 2020; Schmidt & Lipson, 2004).…”

“…First, deepened winter snow enhances soil moisture in the spring (Dorji et al., 2013; Li et al., 2020), which directly reduces soil erodibility by promoting the formation of soil crusts and aggregates, and thus enhancing the stability of surface soil fine particles (Field et al., 2010; Webb & Strong, 2011). Second, increased spring snowmelt can promote plant growth in water‐limited regions by alleviating water and nutrient limitation in the early growing season, which enhances plant cover and above‐ground biomass throughout the growing season (Grippa et al., 2005; Li et al., 2020; Schmidt & Lipson, 2004). Finally, plants in arid grasslands predominately allocate more resources to surface root biomass under deepened winter snow (Li et al., 2020), which enhances aggregate stability and reinforces the soil (Moreno‐Espíndola et al., 2007).…”