Biomass change during succession is a central concept in ecology that describes how the total mass of living organisms in a community shifts as the ecosystem develops over time. Understanding this pattern helps scientists predict ecosystem productivity, carbon storage, and recovery after disturbances, making it vital for conservation, forestry, and climate‑change mitigation efforts.
What Is Ecological Succession?
Ecological succession refers to the orderly process by which species composition and community structure change in a given area following a disturbance or on newly formed substrate. Two main types are recognized:
- Primary succession occurs on barren surfaces lacking soil, such as lava flows, glacial retreats, or sand dunes.
- Secondary succession happens where soil remains intact after a disturbance like fire, logging, or agriculture abandonment.
In both cases, the trajectory of biomass change during succession follows predictable stages, though the rate and magnitude differ.
Biomass Dynamics in Primary Succession
Early Colonizers and Low Biomass
When life first establishes on sterile ground, pioneer species—typically lichens, mosses, and nitrogen‑fixing microbes—dominate. These organisms have:
- Small individual size
- Rapid reproduction but low tissue density
- Limited capacity to store carbon
Because of this, total biomass remains low, often less than 1 % of that found in mature forests. The community’s net primary productivity (NPP) is modest because nutrients are scarce and soil development is nascent Which is the point..
Intermediate Stages and Biomass Accumulation
As organic matter from dead pioneers accumulates, a thin soil layer forms, allowing herbaceous grasses and shrubs to take root. These plants possess larger leaves, deeper roots, and higher lignin content, which boosts:
- Leaf area index (LAI) → more photosynthesis
- Root biomass → greater below‑ground storage
During this phase, biomass can increase exponentially, sometimes doubling every few years. Practically speaking, , Alnus spp. Also, g. Nitrogen‑fixing shrubs (e.) accelerate soil fertility, further amplifying growth Not complicated — just consistent..
Late‑Successional Forest and Biomass Plateau
Eventually, shade‑tolerant tree species replace early successional shrubs. So naturally, these trees allocate substantial carbon to woody stems, leading to a marked rise in above‑ground biomass (AGB). In many primary‑successional chronosequences, AGB reaches 150–300 Mg ha⁻¹ after 100–200 years, after which the increase slows as the system approaches a steady‑state biomass where growth balances mortality and decomposition.
Biomass Dynamics in Secondary Succession
Immediate Post‑Disturbance Drop
When a disturbance removes vegetation but leaves soil intact, biomass plummets abruptly. Practically speaking, for example, a stand‑replacing fire may reduce AGB from 250 Mg ha⁻¹ to under 5 Mg ha⁻¹ within hours. Even so, the soil seed bank, residual roots, and nutrient reserves enable rapid regrowth Not complicated — just consistent. That's the whole idea..
Rapid Early Growth Phase
Herbaceous colonizers and fast‑growing tree seedlings exploit the high light and nutrient availability. Their high specific leaf area (SLA) and low wood density translate into:
- High photosynthetic rates per unit biomass
- Fast turnover of leaf litter
So naturally, biomass can rebound to 30–50 % of pre‑disturbance levels within 5–10 years in many temperate forests.
Mid‑Successional Stabilization
Mid‑successional species—often shade‑intolerant hardwoods or conifers—begin to dominate. Consider this: they invest more in structural tissues (wood, bark) and less in rapid leaf production. Here's the thing — biomass accumulation continues but at a decelerating pace. In many secondary forests, AGB reaches 80–90 % of old‑growth values after 30–50 years Simple, but easy to overlook. Practical, not theoretical..
Approaching Maturity
Eventually, shade‑tolerant species replace early successional trees, and the forest structure resembles that of primary‑successional endpoints. Which means biomass growth slows as the system nears its carrying capacity, dictated by climate, soil depth, and disturbance regime. At this stage, net biomass change approaches zero, though carbon continues to cycle through litter fall and decomposition.
Factors Influencing Biomass Accumulation During Succession
Several abiotic and biotic drivers shape the trajectory of biomass change during succession:
| Factor | Effect on Biomass Trajectory |
|---|---|
| Climate (temperature, precipitation) | Warmer, wetter climates accelerate photosynthetic rates and decomposition, generally increasing peak biomass. |
| Soil fertility & texture | Nutrient‑rich, well‑aerated soils support faster growth and higher biomass ceilings. On top of that, |
| Disturbance frequency & intensity | Frequent or severe disturbances reset succession, lowering long‑term average biomass. On the flip side, |
| Species traits | Traits such as wood density, specific leaf area, and nitrogen‑fixing ability dictate growth speed and biomass allocation. Because of that, |
| Facilitation & competition | Early colonizers can modify microclimate and soil conditions, facilitating later species; intense competition can suppress biomass accumulation. |
| Herbivory & pathogens | Consumption of plant tissue reduces net biomass accumulation, especially in early stages. |
Understanding these controls enables managers to steer succession toward desired outcomes, such as maximizing carbon sequestration or restoring habitat complexity Surprisingly effective..
Case Studies Illustrating Biomass Change During Succession
1. Glacier Bay, Alaska (Primary Succession)
Researchers tracked plots exposed after glacial retreat over 120 years. So at year 80, Sitka spruce (Picea sitchensis) dominated, pushing AGB to >120 Mg ha⁻¹. By year 30, dwarf shrubs raised biomass to ~5 Mg ha⁻¹. That said, 5 Mg ha⁻¹ biomass. Practically speaking, initial moss‑lichen cover contributed <0. The curve showed a classic sigmoid shape: slow start, rapid mid‑phase increase, then asymptote Which is the point..
2. Yellowstone National Park, USA (Secondary Succession Post‑Fire)
After the 1988 fires, lodgepole pine (Pinus contorta) seedlings established within two years. Also, by year 10, AGB averaged 15 Mg ha⁻¹; by year 25, it reached 45 Mg ha⁻¹; and by year 45, values approached 80 Mg ha⁻¹, close to unburned reference stands. The recovery trajectory highlighted the importance of serotinous cones and residual soil nutrients And that's really what it comes down to..
3. Tropical Pasture Abandonment, Brazil (Secondary Succession)
In abandoned cattle pastures, biomass increased from <2 Mg ha⁻¹ (grass‑dominated) to ~30 Mg ha⁻¹ after 15 years, driven by fast‑growing pioneer trees such as Cecropia spp. After 30 years, biomass plateaued around 55 Mg ha⁻¹, still below old‑growth forest values
