Cover Crops May Cause Winter Warming in Snow‐Covered Regions

Abstract

Cover crops, grown between cash crops when soil is fallow, are a management strategy that may help mitigate climate change. The biogeochemical effects of cover crops are well documented, as they provide numerous localized benefits to farmers. We test potential biogeophysical climate impacts of idealized cover crop scenarios by assuming that cover crops are planted offseason in all crop regions throughout North America. Our results suggest that planting cover crops increases wintertime temperature up to 3°C in central North America by decreasing albedo in regions with variable snowpack. Cover crops with higher leaf area indices increase temperature more by decreasing broadband albedo, while decreasing cover crop height helped to mitigate the temperature increase as the shorter height was more frequently buried by snow. Thus, climate mitigation potential must consider the biogeophysical impacts of planting cover crops, and varietal selection can minimize winter warming.Plain Language Summary Planting cover crops is an agricultural management technique in which crops are grown in between cash crop seasons when the soil would otherwise be fallow. Cover crops provide many local benefits to farmers and can increase carbon storage in soils. In this study, we test how planting cover crops in all agricultural regions in North America can change wintertime temperatures. Model simulations suggest that cover crops can warm winter temperatures up to 3°C in regions with variable winter snowpack, such as central North America. Planting cover crop varieties that are less leafy or get buried under the variable snowpack can help to minimize winter warming. Our study suggests that the climate mitigation potential of cover crops may be offset in these regions if cover crop varieties are not carefully selected.

The Community Land Model Version 5: Description of New Features, Benchmarking, and Impact of Forcing Uncertainty

“…Agricultural management practices can have a considerable impact on climate (Bagley et al, ; Davin et al, ; Lombardozzi et al, ; Mueller et al, ; Thiery et al, ), highlighting the importance of representing agriculture in ESMs. CLM5 is the first version of CLM that includes transient representation of crop distribution and management, and the inclusion of managed agriculture in CLM5 does affect carbon, water, and energy fluxes from the land surface.…”

Ground‐Truthing a Recent Report of Cover Crop–Induced Winter Warming

“…This suggests that the maximum effects of cover crops on albedo and local warming are likely far less than the results of the tall-leafy scenario and somewhat greater than the results of the shortleafy scenario. However, the mean snow depth reported in Lombardozzi et al (2018) was greater than 20 cm in much of the region with significant local warming and above 10 cm in all of it. Therefore, in most years, the cover crops in our study would be largely buried in snow.…”

“…While there are additional cover crop species beyond those for which we have presented morphological data, most are unlikely to develop the tall-leafy growth form simulated in Lombardozzi et al (2018) in the regions with significant simulated warming. The most realistic scenario in which a cover crop would approach a height of 50 cm and a LAI of 4 m 2 m -2 would be a warm-season annual that is planted early enough for stem elongation to occur prior to winter.…”

“…The interaction between surface residues and snow depth (Benoit et al, 1986) should also be considered when interpreting results from Lombardozzi et al (2018). Surface residues lead to deeper snowpacks by increasing the threshold wind speed for saltation to occur and reducing snow transport (Pomeroy and Li, 2000).…”

Challenging a Global Land Surface Model in a Local Socio-Environmental System

“…It is possible, however, that the shallower rooting depth prescribed for grasses in CLM [74] could lead to less transpiration and, therefore, higher soil moisture. Soil and plant hydraulics are active areas of research in CLM [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25], and our analysis suggests that, at this site, the within summer seasonal patterns are nearly correct but the overall magnitude could still be improved.…”