Odum's Strategy of Ecosystem Development

Odum's Strategy of Ecosystem Development is a foundational macroecological and systems-ecology synthesis published by the American ecologist Eugene Pleasants Odum (1913–2002) in the journal Science on April 18, 1969 ("The Strategy of Ecosystem Development: An understanding of ecological succession provides a basis for resolving man's conflict with nature," Science, 164: 262–270). Originally delivered as the presidential address to the Ecological Society of America in 1966, Odum's paper unified classical plant community succession (Frederic E. Clements, 1916; Henry Allan Gleason, 1926), Raymond L. Lindeman's (1942) trophic-dynamic energetics, Alfred J. Lotka's (1922) and Howard T. Odum's (1955, 1967) maximum-power thermodynamics, Ramón Margalef's (1963, 1968) information-theoretic maturity gradients, and F. Herbert Bormann and Gene E. Likens' Hubbard Brook watershed biogeochemistry into a single quantitative tabular model of ecosystem ontogeny.

In Odum's formulation, ecological succession—which he termed ecosystem development—is defined by three holistic system-level parameters: (1) it is an orderly process of community directional change that is reasonably predictable; (2) it results from modification of the physical environment by the biological community (autogenic control); and (3) it culminates in a stabilized mature (climax) ecosystem in which maximum biomass (B) and symbiotic function are maintained per unit of available energy flow (E). To make this trajectory operational across terrestrial, freshwater, marine, and laboratory microcosm systems, Odum codified 24 tabular attributes grouped into six functional categories—Community Energetics, Community Structure, Life History, Nutrient Cycling, Selection Pressure, and Overall Homeostasis—contrasting early developmental stages (optimized for rapid net biomass production, r-selection, and linear grazing chains) with mature stages (optimized for structural maintenance, K-selection, detritus food webs, and closed internal nutrient conservation).

Gross Production (P), Community Respiration (R), and Standing Biomass (B)

Building on work conducted with his brother Howard T. Odum on Pacific coral reefs (Eniwetok Atoll, 1955), Florida thermal springs (Silver Springs, 1957), old-field succession at the Savannah River Ecology Laboratory, and aquatic laboratory microcosms (Beyers, 1963; Cooke, 1967), Eugene Odum anchored his theory of ecosystem development in the first and second laws of thermodynamics applied to open dissipative biological systems. Let gross primary production (P_G, or P) denote the total rate of photosynthetic (and chemosynthetic) fixation of radiant energy into organic carbon (measured in kcal m⁻² day⁻¹ or g C m⁻² yr⁻¹), and let total community respiration (R_T, or R) denote the summed catabolic respiratory dissipation of autotrophs (R_A) and heterotrophs (R_H = herbivores + carnivores + detritivores + decomposers):

R = R_A + R_H

The net rate of organic matter accumulation within the ecosystem boundaries—termed Net Ecosystem Production (NEP) or Net Community Production (NCP)—is the difference between gross production and total community respiration:

dB / dt = NEP = P − R − L_export

where B is total standing organic biomass (living phytomass, zoomass, microbial biomass, plus non-living particulate and dissolved organic detritus) and L_export represents net hydrologic or physical export.

Autotrophic versus Heterotrophic Succession Toward P/R = 1

Odum demonstrated that the dimensionless ratio of gross production to community respiration (P/R)—together with the biomass-to-energy-throughput ratio (B/E, where E = P + R)—governs the trajectory of ecosystem development along two symmetric paths converging asymptotically toward metabolic balance (P/R → 1.0):

1. Autotrophic Succession (P/R > 1 initially → P/R ≈ 1 at maturity): Occurs in inorganic environments colonized by photoautotrophs, such as newly exposed glacial moraines, lava flows, sand dunes, abandoned agricultural fields (old-field succession), or inorganic water microcosms. In the early developmental pioneer stage (Attribute 1), standing biomass B is small, respiratory demand R is low, and gross photosynthesis P exceeds R (P/R > 1, yielding high net community production P − R > 0, Attribute 4). As organic matter accumulates in wood, roots, and humus over decades to centuries, every increment of standing biomass B adds to maintenance respiration R until total respiration matches gross photosynthetic capacity (P ≈ R, P/R → 1.0, and NEP = P − R → 0), stabilizing biomass at B_max.
2. Heterotrophic Succession (P/R < 1 initially → P/R ≈ 1 at maturity): Occurs in environments initialized with pre-formed organic detritus—such as a stream receiving organic sewage, a fallen forest log, or a hay-infusion microcosm. Early stages are dominated by heterotrophic bacteria, fungi, and saprophagous invertebrates (R > P, P/R ≪ 1). As labile organic substrates are mineralized into inorganic nutrients (CO₂, NH₄⁺, PO₄³⁻) and colonized by algae or vascular plants, respiration falls and gross primary production rises toward the same metabolic steady state (P/R → 1.0).

The Schrödinger–Margalef Ratio (B/P and B/E)

Following Erwin Schrödinger's What Is Life? (1944) and Ramón Margalef's Perspectives in Ecological Theory (1968), Odum defined the bioenergetic metric of ecosystem maturity as the ratio of total standing structure (B) to maintenance energy flow (P or R) (Attribute 3, B/P, with dimensions of time, i.e., biomass turnover time τ = B/P):

• Early Developmental Stage: Low standing biomass (B ≈ 0.2–2.0 kg dry matter m⁻²) supported by a high specific metabolic rate, yielding a low B/P ratio (τ ≈ days to 1 year) and a high P/B ratio (Attribute 2).
• Mature Climax Stage: High standing biomass (B ≈ 30–60 kg dry matter m⁻² in old-growth forests) maintained by solar-limited gross primary production P, yielding a large B/P ratio (τ ≈ 20 to 50 years) and a low P/B ratio—meaning that a modest flux of energy dissipation supports a large, complex biological structure.

At the core of Odum's 1969 Science article is Table 1 ("A tabular model of ecological succession: trends to be expected in the development of ecosystems"), which organizes 24 measurable ecosystem properties across six functional categories:

Shift from Grazing Food Chains to Detritus Food Webs (Attribute 5)

One of Odum's central trophic insights is that as an ecosystem matures from an annual grassland or phytoplankton bloom into an old-growth forest or kelp bed, the primary pathway of energy flow shifts from the linear grazing food chain to the complex detritus food web:

• In early developmental herb communities or pelagic algal blooms, plant tissues have high nitrogen concentrations and low lignin/cellulose investments; herbivores consume 30% to 60% of net primary production directly while alive.
• In mature forests (such as Hubbard Brook or Coweeta), woody stems and chemically defended foliage (rich in tannins, lignins, and terpenoids; Attribute 10) experience less than 2% to 8% direct herbivory. Over 90% of net primary production enters the forest floor as leaf litter, fine root turnover, and woody debris, processed through a multi-trophic detritus web of saprotrophic fungi, bacteria, oribatid mites, collembolans, millipedes, earthworms, and dipteran larvae. Because detrital carbon buffers seasonal fluctuations in photosynthesis, the detritus pathway confers high temporal stability (Attribute 22) against drought or frost perturbations.

Closure of Biogeochemical Nutrient Cycles (Attributes 7, 15, 16, 17, 20, 21)

Drawing on Bormann and Likens' (1967, 1979) experimental deforestation at Hubbard Brook in New Hampshire and Stark and Jordan's (1978) radiotracer studies on Amazonian rainforests, Odum highlighted how mature ecosystems tighten mineral nutrient cycles (N, P, K, Ca, Mg):

1. Intrabiotic Storage (Attribute 7): In young developmental soils, mineral nutrients reside in the exchangeable soil solution (extrabiotic), where they are vulnerable to leaching. As succession proceeds, plants and microbes pump soluble ions into woody biomass and humic complexes (intrabiotic).
2. Direct Mycorrhizal Nutrient Trapping (Attributes 17 & 20): In mature forests (especially on weathered tropical Oxisols and Ultisols), surface root mats colonized by arbuscular (AM) and ectomycorrhizal (ECM) fungi intercept mineralizing nitrogen and phosphorus directly from decomposing leaf litter before ions enter mineral soil water, reducing streamwater nitrate and phosphate export to near-zero levels (closed mineral cycles, Attribute 15).

The Bioenergetic Trade-Off Between Yield (P − R) and Protection (B)

In the second half of his 1969 Science paper, Odum applied the 24-attribute model to resolve the central environmental dilemma of human land use: humanity requires both high net harvestable production (food and fiber) and high environmental buffering (climate regulation, flood control, and nutrient retention), yet no single ecosystem can maximize both simultaneously:

• Agriculture Maximizes Developmental Attributes: Intensive agriculture and short-rotation forestry arrest succession in an early developmental state (using tillage, monoculture annual crops, and fertilizers) to maximize Net Community Production (P − R, Attribute 4) and the P/B ratio (Attribute 2). The thermodynamic price of maintaining an arrested developmental state is open, leaky mineral cycles (Attribute 15), nutrient runoff, soil erosion, and vulnerability to pest outbreaks (low homeostasis, Attribute 22).
• Mature Ecosystems Maximize Protective Homeostasis: Conversely, old-growth forests, wetlands, and climax prairies maximize standing biomass (B), carbon storage, soil water retention, and biogeochemical closure, but their net harvestable food yield (P − R) approaches zero.

Odum's Four-Compartment Landscape Zoning Model

Rather than forcing every hectare of the landscape into an unstable compromise, Odum proposed Landscape Compartmentalization—dividing regional watersheds into four coupled functional compartments linked by regulated material and energy flows:

1. The Productive Compartment: Croplands and timber plantations (developmental P > R systems dedicated to food and fiber yield).
2. The Protective (Natural) Compartment: Conserved mature ecosystems—old-growth forests, riparian buffer strips, estuaries, and marshes (P ≈ R climax systems dedicated to hydrological buffering, nutrient trapping, and biodiversity maintenance).
3. The Compromise (Multiple-Use) Compartment: Managed rangelands, agroforestry systems, and recreational woodlands intermediate between developmental and mature states.
4. The Urban-Industrial (Non-Vital / Heterotrophic) Compartment: Cities and industrial zones (R ≫ P fuel-powered hubs whose waste heat and effluents must remain within the assimilative capacity of surrounding protective compartments).

Population-Darwinian Critiques of Holistic Ecosystem "Strategy"

During the 1970s and 1980s, Odum's 1969 paper stimulated productive debate between holistic systems ecologists and evolutionary population ecologists (Drury & Nisbet, 1973; Connell & Slatyer, 1977; Vitousek & Reiners, 1975; Pickett, Collins & Armesto, 1987):

1. Individual Natural Selection vs. Ecosystem-Level "Strategy": Evolutionary ecologists (Drury & Nisbet, 1973; Connell & Slatyer, 1977) noted that ecosystems lack a unified genome and are not units of Darwinian natural selection. Observed successional replacements (from fast-growing, shade-intolerant pioneers to slow-growing, shade-tolerant canopy trees) emerge from species-specific life-history trade-offs (seed size vs. dispersal, shade tolerance vs. growth rate; see Connell–Slatyer Succession Models and Tilman's Resource-Ratio Hypothesis).
2. The Vitousek–Reiners (1975) Biomass-Accrual Nutrient Retention Curve: Peter M. Vitousek and William A. Reiners (1975) tested Odum's Attribute 15 and Attribute 21 across watershed chronosequences in New England and the Pacific Northwest, demonstrating that net nutrient retention is highest in intermediate-aged, aggrading forests where net biomass increment (dB/dt = NEP > 0) actively locks nitrogen and calcium into growing wood. Once steady-state climax is reached (dB/dt = 0), net biotic storage ceases and hydrologic nutrient output equals atmospheric/weathering input (Output ≈ Input).
3. Mid-Successional Diversity Peaks and Retrogressive Succession: Long-term chronosequence studies (Connell, 1978; Wardle et al., 2004) showed that species diversity (Attributes 8 & 9) often peaks in mid-succession, and that over multimillennial timescales without rejuvenating disturbance (e.g., Franz Josef Glacier in New Zealand or Kauai in Hawaii), soil phosphorus occlusion drives a retrogressive phase of declining biomass and canopy opening.

What happens to the P/R ratio during autotrophic and heterotrophic succession in Odum's model?

In autotrophic succession (starting on bare rock, sand dunes, or abandoned fields), gross primary production (P) initially exceeds total community respiration (R), so P/R > 1 and net community production (P − R) is high. As standing plant, animal, and microbial biomass (B) accumulates over time, maintenance respiration R increases until it equals gross production, driving P/R → 1 and net yield (P − R) toward zero at climax. In heterotrophic succession (starting on organic sewage or decaying wood), respiration initially exceeds photosynthesis (P/R < 1), and the ratio rises toward 1.0 as organic matter is mineralized and autotrophs colonize.

Why did Eugene Odum argue that humans cannot maximize agricultural yield and ecosystem stability on the same piece of land?

According to Odum's bioenergetic equations, high net harvestable yield (P − R, Attribute 4) occurs only in early developmental ecosystems where standing biomass (B) and community respiration (R) are kept small (high P/B ratio). Conversely, high ecosystem stability, flood buffering, and closed nutrient conservation (Attributes 15, 21, 22) require a large standing biomass (B), complex detrital webs, and mycorrhizal symbioses whose respiratory demand consumes nearly all gross production (P ≈ R, leaving zero net harvestable yield). Odum therefore advocated zoning landscapes into distinct productive (agricultural) and protective (mature natural) compartments.

How did Vitousek and Reiners (1975) modify Odum's prediction about nutrient conservation during succession?

In Attribute 15 and Attribute 21, Odum proposed that mature climax ecosystems have the tightest nutrient conservation and lowest streamwater nutrient losses. Vitousek and Reiners (1975) showed that because net uptake of essential elements (like nitrogen and calcium) is proportional to the net rate of biomass accumulation (dB/dt = NEP), streamwater nutrient losses are actually lowest in intermediate-aged, rapidly growing (aggrading) forests, and rise again toward atmospheric input levels once the mature forest reaches steady-state biomass (dB/dt ≈ 0).

How do Connell and Slatyer's (1977) succession models differ from Odum's (1969) framework?

Whereas Odum (1969) analyzed succession from a top-down, holistic systems perspective (tracking macro-level fluxes of energy P, R, biomass B, and nutrient stoichiometry across 24 emergent ecosystem attributes), Connell and Slatyer (1977) analyzed succession from a bottom-up, neo-Darwinian population perspective, classifying species replacements into three testable interaction pathways—Facilitation, Tolerance, and Inhibition—driven by individual life-history traits and competitive resource depletion.

1. Odum, E. P. (1969). "The strategy of ecosystem development." Science, 164(3877), 262–270. https://doi.org/10.1126/science.164.3877.262
2. Margalef, R. (1963). "On certain unifying principles in ecology." The American Naturalist, 97(897), 357–374. https://doi.org/10.1086/282286
3. Vitousek, P. M., & Reiners, W. A. (1975). "Ecosystem succession and nutrient retention: A hypothesis." BioScience, 25(6), 376–381. https://doi.org/10.2307/1297148
4. Connell, J. H., & Slatyer, R. O. (1977). "Mechanisms of succession in natural communities and their role in community stability and organization." The American Naturalist, 111(982), 1119–1144. https://doi.org/10.1086/283241
5. Wardle, D. A., Walker, L. R., & Bardgett, R. D. (2004). "Ecosystem properties and forest decline in contrasting long-term chronosequences." Science, 305(5683), 509–513. https://doi.org/10.1126/science.1098778