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Climate models for the northeastern United States (U.S.) over the next century predict an increase in air temperature between 2.8 and 4.3 °C and a decrease in the average number of days per year when a snowpack will cover the forest floor (Hayhoe et al. 2007, 2008; Campbell et al. 2010). Studies of forest dynamics in seasonally snow-covered ecosystems have been primarily conducted during the growing season, when most biological activity occurs. However, in recent years considerable progress has been made in our understanding of how winter climate change influences dynamics in these forests. The snowpack insulates soil from below-freezing air temperatures, which facilitates a significant amount of microbial activity. However, a smaller snowpack and increased depth and duration of soil frost amplify losses of dissolved organic C and NO3- in leachate, as well as N2O released into the atmosphere. The increase in nutrient loss following increased soil frost cannot be explained by changes in microbial activity alone. More likely, it is caused by a decrease in plant nutrient uptake following increases in soil frost. We conducted a snow-removal experiment at Hubbard Brook Experimental Forest to determine the effects of a smaller winter snowpack and greater depth and duration of soil frost on trees, soil microbes, and arthropods. A number of publications have been based on these data: Comerford et al. 2013, Reinmann et al. 2019, Templer 2012, and Templer et al. 2012. These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station. Campbell JL, Ollinger SV, Flerchinger GN, Wicklein H, Hayhoe K, Bailey AS. Past and projected future changes in snowpack and soil frost at the Hubbard Brook Experimental Forest, New Hampshire, USA. Hydrological Processes. 2010; 24:2465–2480. Comerford DP, PG Schaberg, PH Templer, AM Socci, JL Campbell, and KF Wallin. 2013. Influence of experimental snow removal on root and canopy physiology of sugar maple trees in a northern hardwood forest. Oecologia 171:261-269. Hayhoe K, Wake CP, Huntington TG, Luo LF, Schwartz MD, Sheffield J, et al. Past and future changes in climate and hydrological indicators in the US Northeast. Climate Dynamics. 2007; 28:381–407. Hayhoe, K., Wake, C., Anderson, B. et al. Regional climate change projections for the Northeast USA. Mitig Adapt Strateg Glob Change 13, 425–436 (2008). https://doi.org/10.1007/s11027-007-9133-2. Reinmann AB, J Susser, EMC Demaria, PH Templer. 2019. Declines in northern forest tree growth following snowpack decline and soil freezing. Global Change Biology 25:420-430. Templer PH. 2012. Changes in winter climate: soil frost, root injury, and fungal communities (Invited). Plant and Soil 35: 15-17 Templer PH , AF Schiller, NW Fuller, AM Socci, JL Campbell, JE Drake, and TH Kunz. 2012. Impact of a reduced winter snowpack on litter arthropod abundance and diversity in a northern hardwood forest ecosystem. Biology and Fertility of Soils 48:413-424.
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Winter soil temperature varies with canopy cover in Siberian larch forests
Abstract In the Arctic, winter soil temperatures exert strong control over mean annual soil temperature and winter CO2emissions. In tundra ecosystems there is evidence that plant canopy influences on snow accumulation alter winter soil temperatures. By comparison, there has been relatively little research examining the impacts of heterogeneity in boreal forest cover on soil temperatures. Using seven years of data from six sites in northeastern Siberia that vary in stem density we show that snow-depth and forest canopy cover exert equally strong control on cumulative soil freezing degrees days (FDDsoil). Together snow depth and canopy cover explain approximately 75% of the variance in linear models of FDDsoiland freezingn-factors (nf; calculated as the quotient of FDDsoiland FDDair), across sites and years. Including variables related to air temperature, or antecedent soil temperatures does not substantially improve models. The observed increase in FDDsoilwith canopy cover suggests that canopy interception of snow or thermal conduction through trees may be important for winter soil temperature dynamics in forested ecosystems underlain by continuous permafrost. Our results imply that changes in Siberian larch forest cover that arise from climate warming or fire regime changes may have important impacts on winter soil temperature dynamics.
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- Award ID(s):
- 2224776
- PAR ID:
- 10571328
- Publisher / Repository:
- Institute of Physics
- Date Published:
- Journal Name:
- Environmental Research Letters
- Volume:
- 19
- Issue:
- 5
- ISSN:
- 1748-9326
- Page Range / eLocation ID:
- 054013
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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ABSTRACT In snow‐dominated areas, runoff from winter precipitation can comprise up to 80% of the annual water budget. Warming winters are shifting snow precipitation to rain, shortening the snow accumulation and melt seasons, and increasing midwinter melt events and flooding during rain‐on‐snow events. At the same time, forests are changing in species composition and geographical extent, and forest‐dominated catchments can mediate the effects of increased winter temperatures on snow dynamics. Here, we combine climatic data and high‐resolution forest and snow observations to investigate the complex relationships between forest canopy structure and below‐canopy snow depth in two low‐relief Mississippi headwater catchments. To do so, we use a two‐dimensional canopy cover metric (i.e., leaf area index) with forest canopy and understory surveys and catchment terrain (e.g., slope, aspect) to examine their joint influences on snow depth. Results show that (1) co‐dominant tree density is a better predictor of peak snow depth over leaf area index, due to representation of both canopy overlap and interception and (2) canopy structural diversity increases peak snow depth. These results suggest that maintaining forest structural diversity not only contributes to forest health but also allows for a deeper snowpack, thereby increasing the potential for water storage in snow‐dominated low‐relief watersheds.more » « less
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The climate is changing in many temperate forests with the amount of forest area dominated by sugar maple experiencing an insulating snowpack expected to shrink between 49 and 95% compared to 1951-2005 values. A reduced snowpack and increased depth and duration of soil frost can injure or kill fine roots, which are essential for plant water and nutrient uptake. These adverse impacts on tree roots can have important impacts on tree growth and ecosystem carbon sequestration. We evaluated the effects of changing winter climate, including snow and soil frost dynamics, by using tree cores to measure sugar maple radial growth rates in the Soil Freezing Study plots at the Hubbard Brook Experimental Forest. These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station. Analysis of these data are published in: Reinmann AB, Susser JR, Demara EMC, and Templer PH. 2019. Declines in northern forest tree growth following snowpack decline and soil freezing. Global Change Biology. 25(2):420-430. https://doi.org/10.1111/gcb.14420more » « less
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{"Abstract":["These data are from four separate projects undertaken between 1997 and\n 2017. The first of these are two snow manipulation (freeze) projects:\n 1) In 1997, as part of a study of the relationships between snow\n depth, soil freezing and nutrient cycling, we established eight 10 x\n 10-m plots located within four stands; two dominated (80%) by sugar\n maple (SM1 and SM2) and two dominated by yellow birch(YB1 and YB2),\n with one snow reduction (shoveling) and one reference plot in each\n stand. 2) In 2001, we established eight new 10-m x 10-m plots (4\n treatment, 4 reference) in four new sites; two high elevation, north\n facing and (East Kineo and West Kineo) two low elevation, south facing\n (Upper Valley and Lower Valley) maple-beech-birch stands. To establish\n plots, we cleared minor amounts of understory vegetation from all\n (both treatment and reference) plots (to facilitate shoveling).\n Treatments (keeping plots snow free by shoveling through the end of\n January) were applied in the winters of 1997/98, 1998/99, 2002/2003\n and 2003/2004.\n\n \n The Climate Gradient Project was established in October 2010. Here we\n evaluated relationships between snow depth, soil freezing and nutrient\n cycling along an elevation/aspect gradient that created variation in\n climate with little variation in soils or vegetation. We established 6\n 20 x 20-m plots (intensive plots) and 14 10 x 10-m plots (extensive\n plots), with eight of the plots facing north and twelve facing south.\n\n \n The Ice Storm project was designed to evaluate the damage and changes\n ice storms cause to northern hardwood forests in forest structure,\n nutrient cycling and carbon storage. Ten 20x30 meter plots were\n established in a predominately sugar maple stand, with 4 icing\n treatments and 2 control plots. The treatments are as follows: Low\n (0.25"), Mid (0.5"), Midx2 (0.5") 2 Years in a row,\n High: (0.75"), Control. The icing treatment was conducted in the\n winter of 2015-2016, with a second year of icing on the Midx2\n treatments plots in the winter of 2016-2017. The treatments are as\n follows: Low (0.25"), Mid (0.5"), Midx2 (0.5") 2 Years\n in a row, High: (0.75"), Control."]}more » « less
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Abstract Cold‐air pooling is an important topoclimatic process that creates temperature inversions with the coldest air at the lowest elevations. Incomplete understanding of sub‐canopy spatiotemporal cold‐air pooling dynamics and associated ecological impacts hinders predictions and conservation actions related to climate change and cold‐dependent species and functions. To determine if and how cold‐air pooling influences forest composition, we characterized the frequency, strength, and temporal dynamics of cold‐air pooling in the sub‐canopy at local to regional scales in New England, USA. We established a network of 48 plots along elevational transects and continuously measured sub‐canopy air temperatures for 6–10 months (depending on site). We then estimated overstory and understory community temperature preferences by surveying tree composition in each plot and combining these data with known species temperature preferences. We found that cold‐air pooling was frequent (19–43% seasonal occurrences) and that sites with the most frequent inversions displayed inverted forest composition patterns across slopes with more cold‐adapted species, namely conifers, at low instead of high elevations. We also observed both local and regional variability in cold‐air pooling dynamics, revealing that while cold‐air pooling is common, it is also spatially complex. Our study, which uniquely focused on broad spatial and temporal scales, has revealed some rarely reported cold‐air pooling dynamics. For instance, we discovered frequent and strong temperature inversions that occurred across seasons and in some locations were most frequent during the daytime, likely affecting forest composition. Together, our results show that cold‐air pooling is a fundamental ecological process that requires integration into modeling efforts predicting future forest vegetation patterns under climate change, as well as greater consideration for conservation strategies identifying potential climate refugia for cold‐adapted species.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1088/1748-9326/ad3bcf
