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Jul 2009

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Accelerated Snowmelt Protocol to Simulate Climate Change Induced Impacts on Snowpack Dependent Ecosystems
加速雪融诱发气候变化对依赖雪被斑块生态系统的影响   

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Abstract

Field studies that simulate the effects of climate change are important for a predictive understanding of ecosystem responses to a changing environment. Among many concerns, regional warming can result in advanced timing of spring snowmelt in snowpack dependent ecosystems, which could lead to longer snow-free periods and drier summer soils. Past studies investigating these impacts of climate change have manipulated snowmelt with a variety of techniques that include manual snowpack alteration with a shovel, infrared radiation, black sand and fabric covers. Within these studies however, sufficient documentation of methods is limited, which can make experimental reproduction difficult. Here, we outline a detailed plot-scale protocol that utilizes a permeable black geotextile fabric deployed on top of an isothermal spring snowpack to induce advanced snowmelt. The method offers a reliable and cost-effective approach to induce snowmelt by passively increasing solar radiation absorption at the snow surface. In addition, control configurations with no snowpack manipulation are paired adjacent to the induced snowmelt plot for experimental comparison. Past and ongoing deployments in Colorado subalpine ecosystems indicate that this approach can accelerate snowmelt by 14-23 days, effectively mimicking snowmelt timing at lower elevations. This protocol can be applied to a variety of studies to understand the hydrological, ecological, and geochemical impacts of regional warming in snowpack dependent ecosystems.

Keywords: Biogeochemistry (生物地球化学), Paired field studies (成对实地研究), Climate warming (气候预警), Induced early snowmelt (诱发早期融雪), Ecosystem (生态系统), Plant phenology (植物物候学)

Background

The intergovernmental panel on climate change reported in 2014 that over a period of 1976-2012 snow cover in the Northern Hemisphere has decreased by 11.7% per decade in the month of June (IPCC, 2014). Snowpack storage is crucial for headwater regions, and early water release could lead to water resource management and ecosystem function issues (Elias et al., 2015; Demaria et al., 2016). It has been predicted that snowmelt timing in the western U.S. could be enhanced by as much as two months by the end of this century (Rauscher et al., 2008), while a more recent study (Clow et al., 2016) reported advanced snowmelt offset by 1-2 weeks over the past two decades in Colorado, which is an essential headwater state. Shorter periods of snow cover and earlier water release have the potential to affect several aspects of ecosystem health in mountainous environments such as water availability and storage (Barnett et al., 2005), plant phenology and succession (Livensperger et al., 2016), and the soil microbial community structure (de Vries and Griffiths, 2018). With several aspects of the environment impacted by shifts in snowmelt timing, it is helpful to have a reliable and reproducible method that enables paired comparisons of enhanced and natural snowmelt across researchers and geographic regions.

A variety of methods have been used to manipulate snowmelt rates. Some have used a shovel to remove snow depth (Wipf et al., 2006), while others implemented more involved methods such as infrared heating sources (Harte et al., 1995; Bokhorst et al., 2008), or distributing black sand across the snow surface area (Steltzer et al., 2009; Blankinship et al., 2018). In contrast to these methods, the protocol described here is a noninvasive, low cost, and easily reproducible method that increases the absorption of solar radiation with a permeable black fabric deployed directly on the snow surface (Walsh et al., 2003; Steltzer et al., 2009). In addition, the method enables paired contrasts between accelerated and natural snowmelt processes in adjacent plots with conserved water equivalents. In contrast to black sand applications, the fabric is removed once the snow has fully melted and does not leave residual non-native material in associated soils. This refined protocol builds upon insights from past studies using permeable fabric covers (Steltzer et al., 2009) with a goal of increasing method utility, adoption and reproducibility. More recent efforts from 2017-2019 in Crested Butte, Colorado have documented snowmelt advancement of 14-23 days when contrasting manipulated and control plots at an elevation of 3,170 meters (Figure 1). The protocol and equipment explained below allows others to establish, deploy and monitor several aspects of the snowmelt process and can be adapted for a variety of environmental studies including but not limited to plant litter decay processes, geochemical shifts in the hydrosphere, and local plant phenology and growth.



Figure 1. Visual representation of tarp deployment and resulting accelerated snowmelt during spring 2019 manipulation. A. The geotextile fabric was deployed after an isothermal snowpack was established. B. Removal of the tarp reveals the clear influence of this protocol on enhanced melting in the target plot. C. Contrast of the accelerated snowmelt plot with the control snowmelt reveals localized, accelerated onset of plant growth in the manipulated plot. Note, white rings visible within the area of manipulation were used for a separate experiment and are not discussed in this protocol (B, C).

Materials and Reagents

  1. Snow cover and anchors
    1. Permeable black UV PE Knitted Shade Cloth 50%: 9.8 x 9.8 m with hemmed grommets spaced every 1.2 m (Agriculture Solutions, catalog number: KS50 )
    2. Type III 550 paracord 60 m spool (Paracord Planet)
    3. 12 Pack aluminum alloy locking Carabiners (Bondream)
    4. Four 1.1 cm x 15.2 cm wooden dowels (Hardware Store)
    5. Four 5 cm x 10 cm x 12 cm wood blocks (Hardware Store)
    6. Drill with a 6.35 mm bit (Hardware Store)

  2. Snow stakes and plot markers
    1. Four PVC pipes 2.5 cm x 3 m; Plain end PVC Schedule 40 Pressure Pipe (Hardware Store)
    2. Multi-Colored Duct Tape (Hardware Store)
    3. Four 1.3 cm x 1.2 m #4 Rebar (Hardware Store)
    4. Small sledge hammer (Hardware Store)

Equipment

  1. Deployment
    1. Post hole digger or metal shovel (Hardware Store)
    2. 35.5 cm Big Grip Garden Knife (Hardware Store)

  2. Data analysis
    1. Two Hobo H21 Data Loggers (Onset HOBO data logger, catalog number: H21-002 )
    2. Four Hobo moisture probes (Onset HOBO data logger, catalog number: S-SMD-M005 )
    3. Four Hobo temperature probes (Onset HOBO data logger, catalog number: S-TMB-M006 )
    4. Two Chemical resistant washdown enclosures 22.9 cm x 22.9 cm x 11.4 cm (McMaster-Carr, catalog number: 8261k27 )
    5. Ultra-abrasion resistant expandable sleeving stainless steel 1.3 cm ID, 3 m length (McMaster-Carr, catalog number: 1478T3 )
    6. 250 g Plumber’s putty (Hardware Store)
    7. TimelapseCam Pro camera (Wingscapes, catalog number: WCB-00121 )
    8. At least 6 Lysimeters (15.2 cm Soil Moisture lysimeters, catalog number: 1905L06 )

Procedure

  1. Plot Selection: During fall snow-free season
    1. Find a location for experimentation with annual snowfall that allows for snowpack manipulation: Ensure the location is not heavily forested or shaded and has a slope aspect that receives direct sunlight radiation throughout the day. In addition, seasonal human and animal traffic should be considered. It is possible that snowmobilers and skiers may frequent the area and precautions may be necessary to prevent damage to the plot. In our case, the PVC snow stakes were successful in designating the area and prevented most human interference.
    2. The control and manipulated plots should be positioned horizontally adjacent at the same elevation and slope aspect to allow for comparison while also preventing interference between the two plots.

  2. Snow fabric preparation: During fall snow-free season
    1. Choose a geotextile fabric surface area larger than the predetermined plot perimeter under investigation to allow for error in deployment placement as well as to minimize boundary effects. Here, we utilized a 9.8 x 9.8 m geotextile that was deployed over a 7.6 x 7.6 m experimental grid (Figure 2).


      Figure 2. Geotextile fabric schematic according to our plot dimensions. Perimeter sizing is easily customizable for different plot sizes. Here our plot dimensions are shown with a square 7.6 x 7.6 m plot (green dashed square), and a 9.8 x 9.8 m geotextile fabric (larger shaded square). The rope lengths should be long enough (at least 1.5 m from the plot) to maintain sufficient tension over the desired plot while allowing the fabric to stay flush against the snow surface area. Carabiners are shown at the fabric corners (dashed ovals) and dowels are shown tied to the ropes threaded across the middle length and width of the fabric (rectangles). Note dowels, rope and carabiner objects are enlarged for visual purposes and are not to scale.

    2. Cut four 0.6 m lengths of paracord and thread each through the grommets of the four corners of the fabric and tie the ends to a carabiner. These ends will serve as attachments to the corner snow anchors described in Procedure C and as shown in Figure 2.
    3. Cut two lengths of paracord that will thread across the full length and width of the geotextile fabric as shown in Figure 2. For our experimental area, two 13 m lengths of rope were cut. When choosing a length, ensure enough extra paracord (~1-1.5 m) is allowed on each end of the tarp to anchor the fabric and allow tension during snowmelt for the fabric to fall flush with the melted snow surface.
    4. Drill holes in the middle of the wooden dowels with a 6.35 mm or larger drill bit to ensure the paracord will thread through the hole.
    5. Thread one stretch of the pre-cut paracord along the length and the other along the width of the fabric through the middle edge grommets and tie the ends of the paracord through the drilled holes of the wooden dowels (Figure 2).
    6. Determine the logistics of deployment and if it is feasible to leave the geotextile fabric folded nearby the plot under study to be recovered during deployment. If not, plan to travel with the tarp during deployment. In our case, we traveled with the snow fabric tied to a travel pack.

  3. Snow stake deployment: During fall snow-free season
    1. Prepare the snow stakes. In our case we used a 3 m PVC pipe length; however, if a higher snowpack is expected the PVC pipe may need to be longer than documented here. Mark each sequential height of one foot with multicolored duct tape on each pipe to allow for approximate snow depth measurements. Multicolored tape is suggested to ensure ease of measuring sequential heights from the time-lapse photos.
    2. Prepare snow anchors: drill holes in the middle of the wooden blocks with a 6.35 mm or larger drill bit to ensure the paracord will thread through.
    3. Drill a hole at the bottom and top of the PVC pipes on the same side approximately 15 cm from the ends using a 6.35 mm or larger drill bit.
    4. Thread the paracord through the drilled hole at the top of the PVC pipe, tying it securely at the top of the pipe. Thread the tied portion of paracord along the outside of the pipe and into the bottom drilled hole and out through the bottom of the pipe leaving 0.3-0.6 m of free paracord.
    5. Tie the free paracord end to the wood block through the drilled hole and do this for all four PVC pipes (Figure 3).


      Figure 3. Snow stake schematic. The anchoring design is shown with holes (circles) drilled in the PVC pipe with paracord (black line) threaded along the height of the pipe to the bottom. The drilled hole at the top of the pole enables quick access to the paracord when the snow has fallen, and the bottom hole is an attachment for the wood block to serve as a snow anchor (bottom rectangle).

    6. Determine the desired snowmelt area by providing at least 1.5 m extra distance from the perimeter of the plot under investigation for anchors to be placed to secure the fabric (Figure 2). Hammer the rebar into the four corners of the determined anchor perimeter until half of the rebar is above the soil surface.
    7. Place the PVC pipes over each rebar with the bottom of the pipe flush against the soil surface to stand in an upright position during the snow season. Ensure the wood block is located at the bottom of the PVC pipe.
    8. Extend the wooden block at the bottom of the PVC pipe outward from the plot to serve as a snow anchor during snowfall.

  4. Data logger assembly: During fall snow-free season
    1. Prepare the soil moisture and temperature probes for the induced snowmelt and control plots following manufacturer instructions. You should have at least two of each probe placed in the center of both plots to ensure redundancy.
    2. Avoid leaving loose wires open to the environment by threading the probe wires through the abrasion resistant steel covers for resistance against critters.
    3. Use the garden knife to make a cut into the soil for the temperature (6 cm depth) and moisture probes (6-12 cm depth) and insert the sensors into each cut.
    4. Place the data logger in the respective waterproof enclosure for each plot to avoid weather damage. You will need to drill a hole in one side of each box to allow the sensor wires to thread through into the box. Once the sensor wires are threaded through, use plumber’s putty to seal the drilled hole.
    5. Connect the sensors to the data logger station using manufacturer instructions and ensure your computer is connected correctly to the logger using the Hoboware software provided. Set the logger to begin logging hourly data acquisition.
    6. Find a landmark such as a tree nearby to secure the time-lapse camera, or use a tripod to capture snowmelt progression directly above the plots. Ensure the camera is higher than the expected snowpack height to ensure photos are collected daily.
    7. Set the camera to activate daily time series using manufacturer instructions. In our case, the time series was set for collection every 24 h in the afternoon.

  5. Snow fabric deployment: During spring peak snowpack
    1. Determine the best time frame for deployment: Ideally the snowpack will be isothermal and entering a net seasonal melting cycle. Our deployment was conducted between April 10-25 in 2017-2019 in Colorado at 3,170 m.
    2. It is best to determine a time when peak snowpack is reached, and no further large snow storms are forecasted. Over the years 2017-2019 snowpack during deployment ranged 1.2-1.5 m.
    3. Access to the site can vary depending upon conditions and distance. Snowshoes or backcountry skis work well with minimal damage to the site; however, snowmobile access is fastest for longer deployment distances.
    4. Once at the site with the pre-deployed snow stakes identified, lay down the prepared fabric with the threaded paracord facing upward and accessible.
    5. Align the corners of the fabric with the snow stake anchor points. Untie the pre-deployed paracord from the top of the snow stakes and tie each tight to the carabiners that are attached to the corner grommets of the fabric (Figure 4A). Note that the end of the untied paracord will be buried in the snow at the bottom of the snow stake.
    6. Dig a trench of increasing depth in the snow from the corners of the geotextile along the length of the paracord to achieve roughly a 45-degree angle to ensure tension on the corners as the snow melts.
    7. Extend the length of the paracord attached to the grommets at the middle length and width of the fabric to secure the four middle edges with the wooden dowels (Figure 4B).
    8. Dig a tapered trench of increasing depth in the snow under the paracord from the edge of the fabric to the end where the wooden dowels will be buried to maintain a 45-degree angle. Use the garden knife to lead the tapered trench and use the post hole digger to dig a hole at the deepest depth of the snow. For our deployments, a tapered trench that reached a 1.2 m deep hole 1-1.5 m from the fabric edge was sufficient.
    9. Bury the dowels by placing the dowel at the bottom of each hole and fill the holes with snow.
    10. Ensure the fabric is flush to the snow surface and secure at all four corners and middle lengths of the perimeter (Figure 4C).


      Figure 4. Geotextile fabric after a successful deployment. A. The corners of the geotextile fabric are tied securely to a carabiner and the paracord from the top of the snow stakes. B. The paracord threaded across the length and width of the fabric is anchored by the wooden dowels buried 1.2 m deep in the snow ~1.5 m away from the fabric edge at a 45-degree angle. C. The fabric is shown deployed flush to the snow surface.

  6. Snow fabric Removal: During spring snowmelt
    Remove the geotextile fabric. This should be when the manipulated snowmelt plot boundary is 60-80% bare ground. Over the years of 2017-2019, the geotextile was removed within a date range of May 30-June 7 to achieve 80% bare ground.

Data analysis

Visually over time, the induced snowmelt should be apparent from the time-lapse photos. The Onset Hoboware software downloadable on any computer will provide outputs of the hourly data during the experiment. It should be clear that the induced snowmelt plot has melted out before the paired control plot and it is possible to infer the time difference using the soil moisture and temperature results while visually validating dates with the time-lapse camera (Figure 5).


Figure 5. Data analysis to determine advanced snowmelt timing in 2017. Use of the time-lapse camera with the soil moisture temperature data will help determine the dates of full melt-out. The fabric was deployed on April 12th (A). and melt-out of the induced plot appears to have occurred on May 13th (first arrow) based on the soil temperature increase; however, the fabric was removed on May 30th (B). New plant growth is apparent in the former location of the tarp demonstrating accelerated plant growth associated with snowmelt manipulation (C). Natural melt-out of the control plot began on June 4th (second arrow), and the full control plot melted completely on June 8th (C). It can be concluded from these observations that the induced snowmelt was advanced by three weeks.

Notes

  1. This method allows a variety of hydrological and ecological aspects of a plot-scale field experiment to be tested for additional analysis. Porewater can be collected using lysimeters; for example, in our experiment 20 lysimeters were utilized with a grid of 4 x 5 across each transect of the square plots. This value however is dependent on the experimental design and should be determined within the scope of each experiment. A minimum of six is suggested assuming three for the manipulated plot and control each. Soil microbial DNA analysis can also be conducted to study the soil microbial communities along with a variety of other methods easily adapted to this paired plot protocol.
  2. When determining the experimental implementation of this protocol, it is recommended to consider whether environmental replicates of manipulated snowmelt are necessary for statistical analysis. Note that an increase in replicates will alter the number of materials and equipment needed, as the numbers provided here are for one manipulated plot and one control. An example of deployed fabric in triplicate is depicted in Figure 6.


    Figure 6. Deployed fabric in triplicate. An increase in replicates utilized for ongoing projects is displayed as an example if environmental replicates are deemed necessary.

  3. Over the past three years using this method, the manipulated snowmelt plot has undergone advanced melt-out 14-23 days prior to the control. Use of the time-lapse camera allowed us to capture the behavior of the induced melting and determine when the complete melt-out of the manipulated versus the control plots occurred (Figure 7 and Video 1).


    Figure 7. Time-lapse photos captured during induced snowmelt in 2017. Geotextile deployment on April 12th (A), the fabric is removed on May 30th (B), and full melt-out of the two paired plots on June 8th (C).

    Video 1. Accelerated snowmelt time-lapse during 2016-2017 snow season

  4. When deciding the best location for our study, we normalized the paired plots by choosing a meadow landscape with an east-northeast aspect to allow for sufficient sun irradiation throughout the day. Sun exposure is necessary for success of this protocol, which could complicate utility in forested regions. In addition, it is best to research annual snowfall depths and variability in the region of investigation to tailor deployment. Ensure the snow stakes will not be covered by the snowpack when it is time to deploy the geotextile. In addition, the snow stakes can partially bend in association with snowpack movement and wind on sloped surfaces effectively shortening their overall height. Create a contingency plan if the snow stakes are covered by the snowpack. We suggest mapping out the location measurements of the stakes using a long measuring tape and compass with respect to a non-moving landmark, or obtain precise GPS coordinates of the anchors.
  5. Snow avalanche awareness is necessary for safe and successful implementation of the protocol. It is required in our research group that members trained in avalanche awareness help with deployment. Keep an eye on the conditions of your site and use avalanche reporting stations if available to analyze the risk. In addition, keep in mind that if the geotextile is deployed early, significant snowfall can upset the progress of the induced snowmelt by covering the fabric and returning sunlight absorption similar to that of the paired control. Advanced melting will not occur until the fabric is snow free, however in our experience subsequent snowfall has not strongly impacted the overall efficacy of this system with respect to net accelerated snowmelt.

Acknowledgments

Financial support was provided by the U.S. Department of Energy (DOE), Office of Science, Office of Biological and Environmental Research under exploratory university-led research: DE-AC02-05CH11231with partial support through the Lawrence Berkley National Laboratory’s Watershed Function Scientific Focus Area under contract DE-AC02-05CH11231 (Lawrence Berkeley National Laboratory; operated by the University of California). Field access and support was provided by the Rocky Mountain Biological Laboratory (RMBL) in Gothic, CO. The Center for Snow and Avalanche Studies, Silverton, CO provided invaluable resources to test and implement the snowmelt approach used in the original implementation of this method. The authors thank Wendy Brown, Tony Brown, Amanda Henderson, and Kayla Hubbard for field and logistical support.
  This protocol was adapted from previous work conducted by co-author Heidi Steltzer published in 2009, “Biological consequences of earlier snowmelt from desert dust deposition in alpine landscapes” (Steltzer et al., 2009).

Competing interests

Authors have no competing interest.

References

  1. Intergovernmental Panel on Climate Change (IPCC). (2014). AR5 Synthesis Report: Climate Change. https://www.ipcc.ch/report/ar5/syr/.
  2. Barnett, T. P., Adam, J. C. and Lettenmaier, D. P. (2005). Potential impacts of a warming climate on water availability in snow-dominated regions. Nature 438 (7066): 303-9.
  3. Blankinship, J. C., McCorkle, E. P., Meadows, M. W. and Hart, S. C. (2018). Quantifying the Legacy of snowmelt timing on soil greenhouse gas emissions in a seasonally dry montane forest. Global Change Biology 24 (12): 5933-47.
  4. Bokhorst, S., Bjerke, J. W., Bowles, F. W., Melillo, J., Callaghan, T. V. and Phoenix, G. K. (2008). Impacts of extreme winter warming in the sub-arctic: growing season responses of dwarf shrub heathland. Global Change Biology 14 (11): 2603-12.
  5. Clow, D. W., Williams, M. W. and Schuster, P. F. (2016). Increasing aeolian dust deposition to snowpacks in the Rocky mountains inferred from snowpack, wet deposition, and aerosol chemistry. Atmospheric Environment, Acid Rain and its Environmental Effects: Recent Scientific Advances, 146 (December): 183-94.
  6. Demaria, E. M. C., Roundy, J. K., Wi, S. and Palmer, R. N. (2016). The effects of climate change on seasonal snowpack and the hydrology of the northeastern and upper midwest united states. Journal of Climate 29 (18): 6527-41.
  7. Elias, E. H., Rango, A., Steele, C. M., Mejia, J. F. and Smith, R. (2015). Assessing climate change impacts on water availability of snowmelt-dominated basins of the upper rio grande basin. Journal of Hydrology: Regional Studies 3 (March): 525-46.
  8. Harte, J., Torn, M. S., Chang, F., Feifarek, B., Kinzig, A. P., Shaw, R. and Shen, K. (1995). Global warming and soil microclimate: results from a meadow-warming experiment. Ecological Applications 5 (1): 132-50.
  9. Livensperger, C., Steltzer, H., Darrouzet-Nardi, A., Sullivan, P. F., Wallenstein, M. and Weintraub, M. N. (2016). Earlier snowmelt and warming lead to earlier but not necessarily more plant growth. AoB Plants 8: pii: plw021. https://doi.org/10.1093/aobpla/plw021.
  10. Rauscher, S. A., Pal, J. S., Diffenbaugh, N. S. and Benedetti, M. M. (2008). Future changes in snowmelt-driven runoff timing over the western US. Geophysical Research Letters 35 (16). doi.org/10.1029/2008GL034424.
  11. Steltzer, H., Landry, C., Painter, T. H., Anderson, J. and Ayres, E. (2009). Biological consequences of earlier snowmelt from desert dust deposition in alpine landscapes. Proc Nati Acad Sci U S A 106 (28): 11629.
  12. de Vries, F. T. and Griffiths, R. I. (2018). Chapter 5: Impacts of Climate Change on Soil Microbial Communities and Their Functioning. In: Climate change impacts on soil processes and ecosystem properties. Developments in Soil Science. Horwath, W. and Kuzyakov, Y. (Eds.). Elsevier. 35:111-29.
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  14. Wipf, S., Rixen, C. and Mulder, C. P. H. (2006). Advanced snowmelt causes shift towards positive neighbour interactions in a subarctic tundra community. Global Change Biology 12 (8): 1496-1506.

简介

[摘要 ] 模拟气候变化影响的野外研究对于预测生态系统对变化的环境的响应具有重要意义。在许多问题中,区域变暖可能导致依赖积雪的生态系统中春季融雪提前,这可能导致更长的无雪期和夏季土壤干燥。过去研究气候变化的这些影响的研究采用多种技术操纵融雪,包括使用铲子手动改变积雪,红外线,黑沙和织物覆盖物。然而,在这些研究中,方法的充分文献记录是有限的,这会使实验复制变得困难。在这里,我们概述了一个详细的样地规模协议,该协议利用部署在等温春季积雪堆顶部的可渗透黑色土工织物来引发高级融雪。该方法通过被动地增加雪表面的太阳辐射吸收,提供了一种可靠且经济高效的方法来融雪。此外,将没有雪堆操纵的控制配置与诱导的融雪图配对,以进行实验比较。科罗拉多州亚高山生态系统的过去和正在进行的部署表明,这种方法可以使融雪加快14-23天,有效地模仿了低海拔地区的融雪时间。该协议可以应用于各种研究,以了解依赖积雪的生态系统中区域变暖的水文,生态和地球化学影响。

[背景] 关于气候变化专门委员会在2014年报道称,在北半球的一个时期1976年至2012年积雪在六月份下降了11.7%,每十(IPCC,2014) 。锡owpack存储是河源地区至关重要,早期的水释放可能导致水资源管理和生态系统功能的问题(埃利亚斯等人,2015年; 德马里亚。等,2016) 。据预测,在美国西部融雪时间可以多达本世纪末增强两个月(劳舍尔等,2008) ,而更近期的研究(克洛等人。2016 )报道先进在过去的两个世纪中,科罗拉多州的融雪被抵消了1-2周,这是一个重要的源头州。较短的积雪时间和较早的水分释放可能会影响山区环境中生态系统健康的多个方面,例如水的可利用性和储存性(Barnett 等,2005),植物物候和演替(Livensperger 等,2016),以及土壤微生物群落结构(de Vries和Griffiths,2018)。由于融雪时间的变化会影响环境的多个方面,因此,有一种可靠且可重现的方法将对研究人员和地理区域的增强融雪和自然融雪进行成对比较是很有帮助的。

已经使用多种方法来控制融雪速率。一些使用铲子去除积雪深度(Wipf 等人,2006),而其他人则采用更多涉及的方法,例如红外加热源(Harte 等人,1995;Bokhorst 等人,2008),或在黑沙上分布雪表面积(Steltzer 等,2009; Blankinship 等,2018)。与这些方法相比,此处介绍的协议是一种非侵入性,低成本且易于重现的方法,该方法使用直接部署在雪面上的可渗透黑色织物来增加对太阳辐射的吸收(Walsh 等,2003;Steltzer 等。 。,2009) 。此外,该方法可以在相邻小区的加速融雪过程和自然融雪过程之间实现成对的对比,并节省了水。与黑沙相比,一旦雪完全融化并且不将残留的非天然物质留在相关土壤中,便可以除去织物。这种改进的方案建立在过去使用可渗透织物覆盖物的研究的见解之上(Steltzer 等,2009),目的是提高方法的实用性,采用性和可重复性。2017年20 月19 日在科罗拉多州克雷斯特比尤特所做的最新工作表明,对比3,170米高处的控制区和对照区,融雪进展14-23天(图1)。下面介绍的协议和设备允许其他人建立,部署和监视融雪过程的多个方面,并且可以适用于各种环境研究,包括但不限于植物凋落物衰变过程,水圈中的地球化学变化和局部植物物候学和成长。



D:\ Reformatting \ 2020-2-7 \ 1902884--1318 Jonathan Sharp 825728 \ Figs jpg \ Figure1.jpg

图1. 可视化表示篷布的部署以及在2019年春季操纵期间导致的加速融雪。A. 建立了一个等温积雪后的土工布部署。B. 去除油布揭示了该协议对目标地块融化增强的重要影响。C. 加速融雪与对照融雪的对比揭示了在受控地块中植物生长的局部,加速发作。请注意,在操作区域内可见的白环用于单独的实验,因此在本协议中未进行讨论(B,C)。

关键字:生物地球化学, 成对实地研究, 气候预警, 诱发早期融雪, 生态系统, 植物物候学

材料和试剂


 


雪盖和锚
渗透性黑色UV PE编织遮光布50%:9.8 x 9.8 m ,每1.2 m间隔有一个卷边索环(农业解决方案,目录号:KS50)
III型550 paracord 60 m 线轴(Paracord Planet)
12件装铝合金锁定登山扣(Bondream )
四1.1厘米x 15.2公分木销钉(硬件小号撕)
四5厘米×10厘米×12厘米木块(硬件小号撕)
用6.35毫米钻头钻孔(硬件S 撕裂)
 


积雪桩和情节标记
四个PVC管2.5 cm x 3 m ; 平端PVC附表40压力管道(硬件小号撕)
多色管道胶带(硬件小号撕)
四1.3厘米X1.2米#4钢筋(硬件小号撕)
小八角锤(五金S tore )
 


设备


 


部署方式
挖孔机或金属铲(五金店)
35.5厘米大握力花园刀(五金店)
 


数据一nalysis
两个何博H21数据记录器(起始HOBO数据记录器,目录号:H21-002)
四个Hobo湿度探头(内置HOBO数据记录仪,目录号:S-SMD-M005)
四个Hobo温度探头(Onset HOBO数据记录器,目录号:S-TMB-M006)
两个耐化学腐蚀冲洗外壳22.9 cm x 22.9 cm x 11.4 cm (McMaster-Carr,目录号:8261k27)
超耐磨可膨胀套管不锈钢,内径1.3厘米,长度3 m (McMaster-Carr,目录号:1478T3)
250克水管工的腻子(五金店)
TimelapseCam 临相机(Wingscapes ,目录号:WCB-00121)
至少6测力计(15.2 cm土壤水分测力计,目录号:1905L06)




程序


 


地块选择:在秋季无雪季节
找出可以进行雪堆操纵的年度降雪量进行试验的位置:确保该位置没有茂密的森林或阴影,并且坡度可以整天接收阳光直射。此外,应考虑季节性的人和动物运输。滑雪者和滑雪者可能会经常出没该地区,并且有必要采取预防措施以防止损坏该地块。在我们的案例中,PVC雪桩成功地指定了该区域,并防止了大多数人为干扰。
控制图和受控图应在同一海拔高度和坡度上水平相邻放置,以便进行比较,同时还可以防止两个图之间的干扰。
 


防雪面料的准备:秋季无雪季节
选择比正在调查的预定样区周长大的土工织物表面积,以考虑布放位置中的误差并最大程度地减少边界影响。在这里,我们利用了9.8 x 9.8 m的土工布,该土工布部署在7.6 x 7.6 m的实验网格上(图2)。
 


D:\ Reformatting \ 2020-2-7 \ 1902884--1318 Jonathan Sharp 825728 \ Figs jpg \ Figure2.jpg


图2. 根据我们的图样尺寸的土工织物结构。可以轻松地针对不同地块大小自定义周长大小。在这里,我们的样地尺寸以7.6 x 7.6 m 的正方形样地(绿色虚线正方形)和9.8 x 9.8 m的土工织物(更大的阴影正方形)显示。绳索的长度应足够长(距离地块至少1.5 m),以在所需的地块上保持足够的张力,同时使织物在雪表面上保持齐平。钩扣显示在织物的角处(虚线椭圆),销钉显示的是绑在穿过织物中间长度和宽度(矩形)的绳索上。注意销钉,绳索和登山扣对象是为了视觉目的而放大的,未按比例绘制。


 


切缶ř 0.6米paracord的长度和通过织物的四个角的扣眼每个线程和领带电子NDS到竖钩。这些末端将作为步骤C中所述的角形雪锚的附件,如图2所示。
如图2所示,将长度切成两段,穿过土工织物的整个长度和宽度。在我们的实验区域,剪断了两条长度为13 m的绳索。选择长度时,请确保在篷布的两端留出足够的额外伞绳(〜1-1.5 m),以固定织物,并在融雪期间施加张力,使织物与融化的雪面齐平。
用6.35 mm 或更大的钻头在木制销钉的中间钻孔,以确保伞绳穿过该孔。
将预切的伞绳的一小段沿着织物的长度方向穿入,另一段沿着织物的宽度穿过中边缘索环,并穿过木销的钻孔将伞绳的两端绑在一起(图2)。
确定部署的后勤工作,并确定是否可行将土工织物折叠在所研究的地块附近,以便在部署期间进行恢复。如果不是,请在部署期间计划随篷布一起旅行。在我们的情况下,我们将防雪布绑在旅行包上。
 


积雪桩部署:在秋季无雪季节
准备雪桩。在我们的案例中,我们使用了3 m的PVC管长度;但是,如果期望更高的积雪量,则PVC管可能需要比此处记录的更长。在每条管道上用彩色胶带将一只脚的每个顺序高度标记出来,以进行近似的雪深测量。建议使用彩色胶带,以确保从延时照片中轻松测量连续高度。
准备防雪锚:用6.35毫米或更大的钻头在木块中间钻孔,以确保伞绳可穿过。
使用6.35毫米或更大的钻头在距两端约15厘米的同一侧的PVC管道的底部和顶部钻一个孔。
将伞绳穿过PVC管顶部的钻孔,然后将其牢固地绑在管顶部。通过管离开的底部沿着所述管的外侧并进入底部钻孔和出螺纹paracord的并列部0.3- 0.6米ö ˚F自由paracord。
将自由的伞绳末端通过钻孔绑到木块上,然后对所有四个PVC管进行此操作(图3)。
 


D:\ Reformatting \ 2020-2-7 \ 1902884--1318 Jonathan Sharp 825728 \ Figs jpg \ Figure3.jpg


图3.雪桩示意图。所示的锚固设计在PVC管道上钻有孔(圆形),顺时针(黑线)沿着管道的高度穿入底部。杆子顶部的钻孔可以在降雪时快速进入伞绳,而底部的孔是木块的附件,用作雪锚(底部矩形)。


 


通过提供至少1.5 m的距离来确定所需的融雪区域,该距离要调查的样地的周边至少要放置用于固定织物的锚点(图2)。将钢筋锤击至确定的弦长周长的四个角,直到钢筋的一半位于土壤表面上方。
将PVC管放置在每个钢筋上,并使管的底部与土壤表面齐平,以在下雪季节直立放置。确保木块位于PVC管的底部。
将PVC管底部的木块从地块向外延伸,以在降雪期间用作防雪锚。
 


数据记录器组件:在秋季无雪季节
按照制造商的说明,准备土壤水分和温度探头,用于诱发融雪和控制区。每个探针至少应放置在两个图的中心,以确保冗余。
通过将探针线穿过耐磨的钢盖,以防止弯曲,避免使散线对环境敞开。
用花园刀在土壤中切出一个温度(深度为6厘米)和湿度探头(深度为6-12厘米),然后将传感器插入每个切口。
将数据记录器放置在每个图的相应防水外壳中,以避免天气损坏。您将需要在每个盒子的一侧钻一个孔,以使传感器导线穿过盒子。传感器导线穿过后,用水管工的腻子密封钻孔。
按照制造商的说明将传感器连接到数据记录仪站,并使用提供的Hoboware 软件确保计算机正确连接到记录仪。设置记录器以开始记录每小时的数据采集。
在附近找到地标,例如树木,以固定定时摄影机,或使用三脚架捕捉地块正上方的融雪过程。确保照相机高于预期的积雪高度,以确保每天收集照片。
按照制造商的说明将相机设置为激活每日时间序列。在我们的案例中,时间序列设定为每隔24 小时收集一次。
 


防雪布的部署:在春季高峰降雪期间
确定最佳的部署时间范围:理想情况下,雪堆将是等温的,并进入净海底融化周期。我们的部署于2017-2019年4月10日至25日在科罗拉多州3,170 m进行。
最好确定到达积雪高峰的时间,并且预计不会有更大的暴风雪。在2017- 20 年间,部署期间的19个积雪量为1.2-1.5 m 。
根据条件和距离的不同,对网站的访问可能有所不同。雪鞋或偏远地区的滑雪板效果很好,对场地的破坏最小。但是,雪地车访问速度最快,可延长部署距离。
一旦在现场发现了预先部署的积雪桩,放下准备好的织物,使带线的伞绳朝上并易于接近。
将布料的角与雪桩固定点对齐。从雪桩的顶部解开预先部署的伞绳,然后将每个紧绳子紧紧地扣在与织物角corner扣相连的安全钩上(图4A)。请注意,解开的伞绳的末端将被埋在雪桩底部的雪中。
挖深度增加的沟槽在雪地˚F ROM土工织物的角部沿着所述paracord的长度粗略地实现45度角,以确保角部作为雪融化张力。
在织物的中间长度和宽度处延长与索环相连的伞绳的长度,以用木销钉固定四个中间边缘(图4B)。
                                                                                                                      挖锥形增加深度的沟槽在雪地理解过程从织物的边缘r处的paracord到其中木销钉将埋保持45度角的端部。使用花园刀引领锥形沟,并使用后挖坑挖的最深的德孔PTH 雪。对于我们的部署,从织物边缘到1.2 m 深的孔1-1.5 m 的锥形沟槽就足够了。
通过将销钉放在每个孔的底部来埋入销钉,并用雪将孔填充。
确保织物与雪表面齐平,并固定在周长的所有四个角和中间长度处(图4C)。
 


D:\ Reformatting \ 2020-2-7 \ 1902884--1318 Jonathan Sharp 825728 \ Figs jpg \ Figure4.jpg


图4.成功部署后的土工织物。A. 土工织物的边角从雪桩的顶部牢固地绑在登山扣和伞绳上。B. 穿过织物长度和宽度的伞绳被埋在雪中1.2 m 深处的木制销钉锚定,该销钉与织物边缘成45度角成1.5 m 。C. 所示织物与雪面齐平展开。


 


除雪布:春季融雪期间
去除土工织物。这应该是在操纵的融雪区边界为60-80%的裸露地面时。在2017- 20- 19年间,土工布在5月30日至6月7 日期间被移除,以实现80%的裸地。


 


数据分析


 


从时间上看,随时间推移的照片应该可以明显地感应到融雪。可在任何计算机上下载的Onset Hoboware 软件将在实验过程中提供每小时数据的输出。应该清楚的是,诱导的融雪图已经在配对的控制图之前融化了,并且可以使用土壤湿度和温度结果推断时差,同时使用延时摄影机以视觉方式验证日期(图5)。


 


D:\ Reformatting \ 2020-2-7 \ 1902884--1318 Jonathan Sharp 825728 \ Figs jpg \ Figure5.jpg


图5.确定2017年提前融雪时间的数据分析。将定时摄影机与土壤湿度温度数据一起使用将有助于确定完全融化的日期。该结构于4月12 日(A)部署。根据土壤温度的升高,诱导区的融化似乎发生在5月13 日(第一个箭头)。但是,织物是在5月30 日(B)移走的。新的植物生长在篷布的前部位置很明显,表明与融雪操作相关的植物生长加快(C)。控制区的自然融化于6月4 日开始(第二个箭头),而整个控制区的融化于6月8 日(C)完全融化。从这些观察结果可以得出结论,诱导的融雪提前了三周。


 


笔记


 


这种方法可以测试样地规模野外实验的各种水文和生态方面,以进行其他分析。可以使用渗漏计收集孔隙水。例如,在我们的实验中,在正方形图的每个样点上使用了20平方公尺的网格,网格为4 x 5。但是,该值取决于实验设计,并且应在每个实验的范围内确定。建议至少六个,假设三个用于操作图并分别控制。还可以进行土壤微生物DNA分析,以研究土壤微生物群落以及其他易于适应该配对试验方案的其他方法。
在确定该协议的实验实现时,建议考虑是否需要对受控融雪进行环境复制以进行统计分析。请注意,重复次数的增加将改变所需的材料和设备的数量,因为此处提供的数量是针对一个操作区和一个控制区。图6所示为一式三份的已部署结构示例。
 


D:\ Reformatting \ 2020-2-7 \ 1902884--1318 Jonathan Sharp 825728 \ Figs jpg \ Figure6.jpg


图6. 一式三份部署的结构。如果认为有必要进行环境复制,则显示正在进行的项目使用的复制增加。


 


在过去的三年中,使用这种方法后,在控制之前14-23天,受控的融雪区已经提前融化。通过使用延时摄影机,我们可以捕获诱发的熔化行为,并确定何时发生了完全熔化的情况(图7 和视频1)。
 


D:\ Reformatting \ 2020-2-7 \ 1902884--1318 Jonathan Sharp 825728 \ Figs jpg \ Figure7.jpg


图7 。在2017年诱导融雪期间拍摄的延时照片。在4月12 日(A)部署土工布,在5月30 日(B)拆除织物,并在6月8 日(C)完全融化两个配对地块。


 






V IDEO 1. 2016 - 2017年期间融雪加速时间推移雪季节


 


在为我们的研究确定最佳位置时,我们通过选择东北偏东的草地景观来规范配对的样地,以全天提供充足的阳光照射。阳光照射对于该协议的成功是必不可少的,这可能会使在林区中的实用程序复杂化。此外,最好在调查区域内研究年度降雪深度和变异性,以调整部署范围。确保在部署土工布时,雪堆不会被积雪覆盖。另外,雪桩会随着积雪的运动而部分弯曲,并且在倾斜的表面上会刮风,从而有效地缩短了它们的整体高度。如果积雪覆盖了积雪堆,请制定应急计划。我们建议使用长卷尺和指南针针对静止的地标绘制木桩的位置测量结果,或者获取锚点的精确GPS坐标。
雪崩意识对于安全和成功实施该协议至关重要。我们的研究小组要求经过雪崩意识培训的成员可以帮助部署。密切注意站点的状况,并使用雪崩报告站(如果有)来分析风险。此外,请记住,如果土工布部署得早,大量的降雪会通过覆盖织物并返回与配对控件类似的阳光吸收而扰乱诱导的融雪过程。除非织物没有积雪,否则不会发生高级融化,但是根据我们的经验,随后的降雪并未严重影响该系统在净加速融雪方面的整体功效。
 


致谢


 


由美国能源部(DOE),科学办公室,生物与环境研究办公室根据大学主导的探索性研究项目DE-SC0016451 提供财政支持,并通过劳伦斯伯克利国家实验室的分水岭功能科学重点领域按合同提供了部分支持DE-AC02-05CH11231 (劳伦斯伯克利国家实验室;由加利福尼亚大学运营)。科罗拉多州哥特市的落基山生物实验室(RMBL)提供了现场访问和支持。科罗拉多州希尔弗顿的雪和雪崩研究中心提供了宝贵的资源来测试和实施该方法的原始实施中使用的融雪方法。作者感谢Wendy Brown,Tony Brown,Amanda Henderson和Kayla Hubbard的现场和后勤支持。


  该方案改编自合著者海蒂· 斯特尔策(Heidi Steltzer)于2009年发表的著作“高山景观中沙漠尘埃沉积引起的早期融雪的生物学后果”(Steltzer 等,2009)。


 


竞争我nterests


 


作者没有竞争利益。


 


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引用:Leonard, L. T., Wilmer, C., Steltzer, H., Williams, K. H. and Sharp, J. O. (2020). Accelerated Snowmelt Protocol to Simulate Climate Change Induced Impacts on Snowpack Dependent Ecosystems. Bio-protocol 10(6): e3557. DOI: 10.21769/BioProtoc.3557.
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