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Modern forest management generally relies on thinning treatments to reduce fuels and mitigate the threat of catastrophic wildfire. They have also been proposed as a tool to augment downstream flows by reducing evapotranspiration. Warming climates are causing many forests to transition from snow-dominated to rain-dominated precipitation regimes—in which water stores are depleted earlier in the summer. However, there are relatively few studies of these systems that directly measure the hydrologic impacts of such treatments during and following snow-free winters. This work compares the below-canopy meteorological and subsurface hydrologic differences between two thinning prescriptions and an unaltered Control during periods of extreme drought and near-record precipitation (with little snow). The field site was within a coniferous forest in the rain-snow transition zone of the southern Cascades, near the Sierra Nevada Range of California. Both thinning-prescriptions had a modest and predictable impact on below-canopy meteorology, which included their causing lower nighttime minimum temperatures in the critical summer months and higher wind speeds. Relative to the Control, both treatments affected soil moisture storage by delaying its annual decline and increasing its minimum value by the end of the season. The onset of soil moisture depletion was strongly tied to the magnitude of winter precipitation. In dry years, it began much earlier within the dense Control stand than in the treated ones, and, without snow, soil moisture was not replenished in the late spring. During high precipitation years, the storage capacity was topped off for all three stands, which resulted in similar timing of moisture decline across them, later in the season. The two thinning prescriptions increased stores through the height of summer (in wet and drought years). Finally, the basal area increment (BAI) of the remaining trees rose in both, suggesting they used the excess moisture to support rapid growth.
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Snow Accumulation Increases With Forest Structural Diversity in Low‐Relief Catchments
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.
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- Award ID(s):
- 2153802
- PAR ID:
- 10666481
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Hydrological Processes
- Volume:
- 39
- Issue:
- 12
- ISSN:
- 0885-6087
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Snow and frost measurements have been collected approximately weekly during the winter season at the Hubbard Brook Experimental Forest using transects underneath the forest canopy adjacent to the established network of standard rain gages from 1956 to the present. Maximum snow depth, snow water content, frost occurrence, and frost depth data are recorded at points along a transect known as a snow course, which includes 10 points spaced at 2-m intervals within a designated 0.25 ha area. Data from one course are averaged for each collection date. These data were gathered at the Hubbard Brook Experimental Forest in Woodstock, NH, which is operated and maintained by the USDA Forest Service, Northern Research Station.more » « less
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Snow and frost measurements have been collected approximately weekly during the winter season at the Hubbard Brook Experimental Forest using transects underneath the forest canopy adjacent to the established network of standard rain gages from 1956 to the present. Maximum snow depth, snow water content, frost occurrence, and frost depth data are recorded at points along a transect known as a snow course, which includes 10 points spaced at 2-m intervals within a designated 0.25 ha area. Data from one course are averaged for each collection date. These data were gathered at the Hubbard Brook Experimental Forest in Thornton, NH, which is operated and maintained by the USDA Forest Service, Northern Research Station.more » « less
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Snow and frost measurements have been collected approximately weekly during the winter season at the Hubbard Brook Experimental Forest using transects underneath the forest canopy adjacent to the established network of standard rain gages from 1956 to the present. Maximum snow depth, snow water content, frost occurrence, and frost depth data are recorded at points along a transect known as a snow course, which includes 10 points spaced at 2-m intervals within a designated 0.25 ha area. Data from one course are averaged for each collection date. These data were gathered at the Hubbard Brook Experimental Forest in Woodstock, NH, which is operated and maintained by the USDA Forest Service, Northern Research Station.more » « less
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Snow and frost measurements have been collected approximately weekly during the winter season at the Hubbard Brook Experimental Forest using transects underneath the forest canopy adjacent to the established network of standard rain gages from 1956 to the present. Maximum snow depth, snow water content, frost occurrence, and frost depth data are recorded at points along a transect known as a snow course, which includes 10 points spaced at 2-m intervals within a designated 0.25 ha area. Data from one course are averaged for each collection date. These data were gathered at the Hubbard Brook Experimental Forest in Thornton, NH, which is operated and maintained by the USDA Forest Service, Northern Research Station.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1002/hyp.70352
