Snow and the Subnivean Ecotone

Winter wonderland

When I look out the window, the landscape looks quiet—muted, simplified, almost suspended. Garden beds disappear under a smooth white blanket. Fields lose their texture. Woods grow hushed. It is easy to assume that winter has pressed pause.

Understanding snow as insulation, structure, and habitat changes the way we see winter. The white blanket covering our gardens is not merely decorative. It is a living system, quietly shaping survival until spring returns.

Snowflake Formation

Snowflakes begin high in the atmosphere inside clouds, where tiny droplets of water and invisible water vapor are constantly moving around. When the temperature in a cloud drops below freezing, water vapor sticks to microscopic particles such as dust or pollen. Instead of turning into liquid water first, the vapor changes directly into ice. 

Nakaya diagram of snow crystal formation 
Source (snowflakes.com)

As soon as that first bit of microscopic ice forms, it becomes the center of a tiny crystal. Because of the way water molecules bond when they freeze, the crystal naturally forms a six-sided, or hexagonal, shape. That basic six-sided structure is the foundation of every snowflake.

Snowflake images - W. A. Bentley

As the crystal falls through the cloud, more water vapor freezes onto it. The temperature and humidity of the air determine how the snowflake grows. In some conditions, it develops flat plates; in others, it grows long arms or delicate branching patterns. Since each snowflake travels through slightly different layers of air, no two follow exactly the same path or experience the same conditions. That is why every snowflake has a unique design.

Once those flakes reach the ground, an entirely new process begins. Over time, layer upon layer of fallen snow transforms into something important known as snowpack.

Snowpack

Snowpack is simply the accumulation of snow that remains on the ground over time. It forms when repeated snowfalls occur without completely melting between storms. Instead of disappearing, each new snowfall settles on top of the previous one, creating distinct layers. In regions with consistent winter cold—whether in the mountains of the West or during a steady winter—this layered structure can persist for weeks or months.

Principal physical processes of a snowpack
WSL - Institut für Schnee und Lawinenforschung SLF

When snow accumulates deeply enough, the bottom layer—where snow meets the ground—begins to change. Heat rising from the soil slightly warms this lowest layer, while the upper layers remain cold. This temperature difference causes the snow crystals near the ground to become larger and more loosely packed, creating small air spaces. Over time, these spaces connect, forming a hidden network of tunnels and pockets.

Diagram of ecotones - State of Maine

Subnivean Zone

This space is called the subnivean zone (from the Latin “sub” meaning under, and “nivean” relating to snow). It exists between the soil surface and the compacted snow above. While air temperatures above the snow may plunge well below freezing, the subnivean layer remains comparatively stable—often hovering around 32°F. The snowpack acts as insulation, trapping heat from the earth and buffering against wind.

Many of native pollinators spend the winter far closer to the ground than we might imagine. Unlike honey bees, which overwinter as a colony, most native bees are solitary. A large number nest in soil, creating small underground chambers where larvae develop and eventually overwinter as adults or pupae. Others overwinter in hollow stems, leaf litter, or just beneath the soil surface.

A consistent snowpack provides insulation that moderates extreme temperature swings. Even when air temperatures drop into the single digits, soil temperatures beneath steady snow often remain close to freezing but relatively stable. That stability can mean the difference between survival and winterkill for ground-nesting bees.

Polyester bee (Colletes spp.) Photo:Heather Holm

The same is true for many butterflies and moths. Some species overwinter as chrysalides attached to stems or hidden in leaf litter. Others overwinter as caterpillars tucked into protected crevices at the soil surface. Snow cover acts as a thermal blanket, shielding them from desiccating winds and repeated freeze–thaw cycles.

Some common overwintering insects stage and site.

American dog tick (Dermacentor variablis) - adult, in soil - (actually an archanid)

Japanese beetle (Popillia japonica) - mature grub (larva), in soil

Squash vine borer (Mellitia cucumberitae) - larva or pupa, cocoon in soil

Bean leaf beetle ( Ceratoma trifurcate) - adult, in soil or under plant debris.

Ironically, winters with little snow can be harder on pollinators than colder winters with steady snow cover. Without insulation, soil temperatures fluctuate more dramatically. Repeated freezing and thawing can damage overwintering insects and expose them to predators.

This connection reinforces an important gardening principle: leaving plant stems standing and allowing leaf litter to remain through winter is not neglect—it is habitat stewardship. When snowpack settles over an undisturbed garden bed, it creates a layered system of protection: soil warmth rising from below, insulating snow above, and structural plant material in between.

By early spring, as snow gradually melts, moisture filters into the soil, and soil temperatures rise slowly. This gentle transition supports emerging pollinators and early-season flowering plants alike.

What looks like a quiet winter garden is actually a protected nursery beneath the snow. The subnivean space, shaped by snowpack, helps ensure that when spring returns, the bees, butterflies, and other beneficial insects return with it.

Additional Resources

How do snowflakes form? - National Oceanic and Atmosphere Administration

Spring reveals subnivean secrets - Maine Department of Inland Fisheries and Wildlife

The physics of snowflakes - American University, Washington, DC

Below the snow - Department of Fish, Wildlife and Parks, State of Montana

Subnivean - Department of Fish and Game, State of Idaho

How to help bees and butterflies survive the winter - University of New Hampshire

New Jersey Pollinators - NRCS - USDA

Snow crystal information - snowcrystals.com

Bees in winter - University of Wisconsin - Madison

Surviving winter: what heat-loving butterfly do during cold months - Xerces Society

How do insects survive winter? - University of Nebraska - Lincoln

Snow - WSL - Institute for Snow and Avalanche Research SLF

Digging Deeper into New Jersey's Soil Taxonomy

 

Soil Taxonomy is the scientific system used to classify and name soils based on their observable and measurable properties. It was developed by the United States Department of Agriculture (USDA) and is widely used in the U.S. and internationally for soil survey, research, land use planning, and natural resource management.

Like the taxonomy used for plants, soil taxonomy is hierarchical — it has six main levels, from broadest to most specific:

1. Order — the broadest group; there are 12 soil orders worldwide. Orders are defined by dominant soil-forming processes and major diagnostic features (e.g., presence of permafrost, organic matter, clay accumulation).
• Examples: Mollisols (prairie soils), Ultisols (weathered soils), Histosols (organic soils).

2. Suborder — groups soils within an order based on properties like moisture regime or dominant processes.
3. Great Group — further divides suborders by the presence of specific horizons or features.
4. Subgroup — refines great groups to indicate how typical or atypical a soil is within that group.
5. Family — describes properties important for use and management, such as particle size, mineralogy, temperature regime.
6. Series — the most specific level; identifies soils that are alike in all major profile characteristics. Soil series names are often geographic (e.g., Atsion, Manahawkin).
   

Soil horizons are distinct layers of soil that form naturally over time through soil-forming processes like weathering, organic matter accumulation, leaching, and biological activity. When you dig a soil pit, you can usually see these layers stacked vertically — together they form what’s called a soil profile.

Atsion Soil Profile - UC Davis

Atsion Soil Profile Photo - NRCS

Most soils have a combination of some or all of these master horizons, usually named by letters:

O Horizon

• What it is: Organic layer — composed mostly of decomposed leaves, plant material, and other organic matter.
• Where found: Common in forests and wetland soils, but often absent in cultivated soils.

A Horizon (Topsoil)

• What it is: Surface mineral soil mixed with humus (decomposed organic material). Darker in color due to organic matter.
• Importance: Most fertile layer — where seeds germinate and roots grow.

E Horizon (Eluviation layer)

• What it is: A light-colored, leached layer where minerals and nutrients have been washed (eluviated) out.
• Where found: Common in forested soils under the A horizon.

B Horizon (Subsoil)

• What it is: Zone of accumulation (illuviation) — where leached materials (like clay, iron, or organic compounds) from upper layers collect.
• Appearance: Often denser and more colorful due to clay and minerals.

C Horizon

• What it is: Weathered parent material — partially broken down rock or unconsolidated deposits. Little biological activity.
• Significance: The source material from which the soil develops.

R Horizon

• What it is: Hard, unweathered bedrock beneath the soil layers.
• Note: Not soil per se, but it’s included as the bottom boundary.

Understanding soil taxonomy will help you match plants to the right soil conditions, leading to healthier gardens with fewer problems. By knowing your soil’s classification, you can better predict how it drains, retains nutrients, and responds to amendments like compost or lime. This knowledge will guide smarter choices for planting, watering, and fertilizing, reducing waste and improving plant success. Ultimately, soil taxonomy empowers you to work with your soil’s natural properties instead of against them, creating more sustainable and productive home gardens.  Use the additional resources listed below to explore and learn more about soil and its structure.

Additional Information

USDA Soil Orders Taxonomy Poster - USDA

Marlton Soil Series Block Diagram - UC Davis Soil Explorer

New Jersey Soil Profile Photos - National Resource Conservation Service (NRCS)

Web Soil Survey Web App - NRCS

Soil Web - UC Davis - Great tool for finding information about soils where you live.

Eluviation-Illuviation Soil Formation - University of New England, Australia

Slugs - In the garden

Leopard Slug (Limax maximus) - Ohio State University

Slugs are among the most misunderstood and underappreciated animals in the natural world. Often viewed as garden pests or unsightly creatures, these soft-bodied gastropods actually represent a fascinating chapter in the evolutionary narrative of life on Earth. With a lineage that stretches back hundreds of millions of years and ecological roles that range from decomposers to predators, slugs are as biologically rich as they are squishy.

Natural History

Slugs belong to the class Gastropoda, a diverse group of mollusks that also includes snails, limpets, and sea slugs. Unlike their shelled relatives, slugs have evolved to lose or significantly reduce the protective external shell that typifies most gastropods. This shell loss has occurred multiple times in gastropod evolution—a classic example of convergent evolution, in which similar traits evolve independently in different lineages.

The transition to a shell-less body allowed slugs greater flexibility and access to narrow crevices and subterranean habitats. While this came at the cost of some protection, slugs adapted through behaviors, chemistry, and mucus-based defense mechanisms.

The slug’s anatomy is a model of evolutionary trade-offs. Its soft, elongated body glides across surfaces using rhythmic muscular contractions of the foot, aided by a thin trail of mucus that reduces friction and helps deter predators. The body is covered in moist, glandular skin that must be kept wet to prevent desiccation.

Slug Anatomy - Oregon State University

At the head end are two pairs of retractable tentacles. The upper, longer pair is tipped with light-sensitive eyes, while the lower pair serves as chemical sensors. On the right side of the body lies the pneumostome, the breathing pore that opens into a primitive lung.

Mucus is arguably the slug’s most important adaptation. It plays a role in movement, moisture retention, communication, and defense. Some slugs can produce sticky or foul-tasting mucus to discourage predators or escape when attacked.

Slugs are found on every continent except Antarctica, thriving in moist environments from temperate woodlands to tropical forests. Their reliance on high humidity restricts them to areas with regular rainfall, thick leaf litter, or moist soil.

Most slugs are nocturnal or crepuscular, avoiding the sun to minimize water loss. In dry periods, they retreat under logs, rocks, or underground, sometimes entering a dormant state known as aestivation.

Slugs are primarily herbivorous scavengers, feeding on decaying vegetation, fungi, algae, and living plant material. Their mouth contains a specialized feeding structure called a radula—a ribbon-like tongue lined with rows of microscopic teeth—which they use to rasp and shred food.

Some slugs, particularly in tropical and temperate forests, are omnivores or even carnivores, feeding on other invertebrates, slug eggs, or carrion. This dietary flexibility makes them important players in the breakdown of organic matter and nutrient cycling within ecosystems.

In turn, slugs are a vital food source for a wide range of animals, including birds, amphibians, beetles, hedgehogs, and rodents.

Slugs are hermaphrodites, possessing both male and female reproductive organs. During mating, which can involve complex and even acrobatic courtship behaviors, two slugs exchange sperm and both may go on to lay eggs.

Slug Eggs - University of Maryland

Eggs are laid in moist, protected environments and hatch into juvenile slugs resembling miniature adults. Most slug species live for one to two years, though life span varies by species and environment.

Gray Slug Lifecycle - Oregon State University 

Beyond mucus and cryptic behavior, some slugs have evolved more specialized defenses. For instance, certain species exude distasteful chemicals, while others mimic the appearance of toxic animals. Bright coloration is rare in terrestrial slugs but common among nudibranchs, their marine relatives, who often advertise their toxicity with vivid hues.

Slugs are a persistent and often frustrating problem in gardens and landscapes, especially in cool, moist climates. These slimy mollusks can quickly damage seedlings, leafy vegetables, and ornamental plants, leaving behind ragged holes and telltale slime trails. Yet, while it may be tempting to reach for chemical slug pellets, there’s a more thoughtful and effective solution: Integrated Pest Management (IPM).

IPM is a sustainable, science-based approach to pest control that minimizes risks to people, pets, and the environment. Rather than relying on a single method, IPM uses a combination of biological, cultural, physical, and chemical tools to manage pests like slugs in a way that is effective and ecologically responsible.

• Understanding the slugs and they life cycle
• Monitor and assess slug levels in your garden
• Prevent conditions that allow slug outbreaks
• Use targeted control methods only when necessary
• Evaluate the effectiveness of your approach and adapt over time

This proactive and adaptive strategy can dramatically reduce slug damage while preserving beneficial insects and maintaining a healthy garden ecosystem.

Prevention

 Make the Garden Less Slug-Friendly

• Reduce moisture: Slugs thrive in damp conditions. Water plants in the morning rather than evening to allow the soil to dry before nightfall.
• Clear hiding spots: Remove debris, boards, dense ground covers, and thick mulch where slugs hide during the day.
• Encourage airflow: Prune overcrowded plants to improve air circulation and reduce humidity.

Barriers and Deterrents

These physically or chemically deter slugs from reaching plants.  Here are some effective options:

• Copper tape or strips: Slugs receive a mild electric shock when they cross copper. Use around pots or garden beds.
• Crushed eggshells or diatomaceous earth: Sharp or abrasive materials irritate the slug’s body, but they lose effectiveness when wet.
• Wool pellets or matting: Some products form a barrier that deters slugs while helping retain soil moisture.
• Slug collars: Small plastic or metal collars placed around plant stems.

Traps and Baits

You can trap and remove slugs or lure them to poison baits.

DIY traps:

• Beer trap: Bury a shallow container (like a tuna can) level with the soil and fill it with beer. Slugs are attracted, fall in, and drown.
• Grapefruit or melon rinds: Place them cut side down in the garden overnight. Slugs gather underneath and can be removed in the morning.
  
  

Slug baits:

• Look for iron phosphate–based slug baits (e.g., Sluggo). It’s effective, safe for pets, humans, and wildlife, and breaks down into fertilizer.
• Avoid metaldehyde slug pellets—it’s toxic to pets, birds, and beneficial insects.

Natural Predators

Encouraging or introducing natural predators can help keep slug populations in check:

• Ground beetles, toads, frogs, and birds feed on slugs.
• Create habitats with rocks, logs, or water features to invite these animals.
• Nematodes (e.g., Phasmarhabditis hermaphrodita) are microscopic worms that kill slugs from the inside.

Resistant Plants

Choose plants that slugs are less likely to eat. Some examples:

• Ferns
• Lavender
• Geraniums
• Foxglove
• Ornamental grasses
• Sage
• Rosemary

Manual Removal

• Go slug hunting at night with a flashlight.
• Wear gloves or use tongs to pick and dispose of them (e.g., in soapy water or a sealed container).
• This is labor-intensive but effective in small gardens.

Keep Containers and Raised Beds Clear

Slugs often hide under pots, trays, or the edges of raised beds. Regularly lift and inspect these areas and apply deterrents as needed.

Controlling slugs in a home garden requires a combination of methods. The key is to make your garden less inviting while targeting existing slugs in an environmentally responsible way.

Additional Resources

Land Snails and Slugs of the Mid-Atlantic - Carnegie Museum

Slug it out with slugs - Iowa State University Extension

What the heck is a nudibranchs? - American Museum of Natural History

Gardening with and without slugs and snails - OSU Extension

Slugs and snails in the vegetable garden - Rutgers University Extension

Timing in Nature - Phenology

Phenology is the study of the timing of biological events in plants and animals, such as flowering, leafing, migration, and breeding, in relation to seasonal and environmental changes. In ecology, phenology is used in several important ways:

1. Tracking Ecosystem Responses to Climate Change: Changes in phenological events (e.g., earlier blooming of flowers, shifts in migration times) can indicate how ecosystems are responding to climate change. Ecologists monitor these shifts to understand the broader impacts on biodiversity and ecosystem health.
2. Understanding Species Interactions: Phenology helps ecologists study how the timing of different species' activities align. For example:
• Plant-pollinator interactions: If plants bloom earlier but pollinators (like bees) don't emerge earlier, it can disrupt pollination.
• Predator-prey dynamics: If prey species hatch earlier but predators are not synchronized, it may affect survival rates.

3. Assessing Ecosystem Productivity: Phenology is used to estimate the timing and duration of growing seasons, which influences primary productivity (the amount of plant growth) in ecosystems. This information is vital for understanding carbon cycles and ecosystem functioning.
4. Wildlife and Conservation Management: Knowing the phenology of species helps in planning conservation efforts and managing wildlife populations. For instance, understanding breeding seasons can guide habitat protection efforts.
5. Predicting Ecological Shifts: Long-term phenological data can be used to predict future changes in ecosystems, such as shifts in species distributions or changes in ecosystem services like crop pollination and water availability.
6. Monitoring Ecosystem Health: Sudden or abnormal shifts in phenological patterns can serve as indicators of environmental stress or ecological disturbances (e.g., drought, pollution).

By integrating phenology into ecological research, scientists gain insights into how organisms and ecosystems respond to environmental variability and change, which is crucial for developing strategies to maintain biodiversity and ecosystem resilience.

Phenology is also a valuable tool for the home gardener when planning and planting vegetables, as it aligns gardening activities with natural seasonal changes rather than fixed calendar dates. Traditional planting schedules often rely on estimated frost dates, which can vary from year to year due to unpredictable weather patterns. By observing natural cues—such as the blooming of trees and flowers, the return of migratory birds, or the emergence of insects— you can determine the optimal time to plant specific vegetables. For example, many gardeners use the blooming of forsythia as a sign that it is time to plant cool-season crops like peas, spinach, and lettuce, while the blooming of lilacs indicates the right conditions for planting warm-season crops such as tomatoes, peppers, and beans.

Forsythia

Phenology also helps a gardener stagger plantings for continuous harvests. Many vegetables, such as lettuce, radishes, and carrots, benefit from successive planting every few weeks to provide a steady supply throughout the season. By observing phenological cues, a gardener can determine the best times to start new plantings based on weather patterns and plant growth stages, rather than following a rigid schedule. This strategy maximizes garden productivity and ensures a steady stream of fresh produce.

In addition to planting, phenology can guide a you in companion planting and pest control. Certain pests, such as cabbage moths or squash vine borers, emerge at specific times of the year based on temperature and plant development. By monitoring natural indicators—such as when specific wildflowers bloom or insects appear—you can take proactive measures like covering crops, introducing beneficial insects, or planting pest-repelling companion plants at the right time. This approach reduces the reliance on pesticides and promotes a healthier, more sustainable vegetable garden.

Squash Vine Borer (Milittia satyrinformis)

By integrating phenology into your gardening practices, a gardener can create a more efficient and resilient vegetable garden. Observing seasonal changes and natural cues allows for smarter planting decisions, better pest management, and improved yields, all while working in harmony with nature.

Additional Resources

USA National Phenology Network

Phenology - University of Wisconsin Extension

Phenology Study - Aldo Leopold Foundation

Using Phenology for Ornamental Pest Control - University of Illinois Extension