Combines long-term field experiments, infrared warming manipulations, and elevation gradients to understand how sagebrush-dominated and subalpine plant communities respond to climate change across the Gunnison Basin.
The Rocky Mountains are warming faster than the global average, and the subalpine meadows around the Rocky Mountain Biological Laboratory (RMBL) in Gothic, Colorado, provide a natural laboratory for understanding what that warming means for mountain ecosystems. For more than three decades, researchers have been heating small patches of meadow at a place known as the Warming Meadow, watching how plants, soils, insects, and microbes respond. Because the Gunnison Basin sits at a climatic crossroads — where sagebrush steppe gives way to subalpine forb meadows and alpine tundra — the answers from these experiments inform how land managers think about water supplies, livestock forage, carbon storage, and biodiversity across the West.
A few key concepts make the rest of this primer accessible. Climate change experiments are manipulative studies that alter temperature, snowmelt, or moisture in the field to mimic the future and observe responses in real plant communities. At RMBL, the dominant tool has been infrared heating manipulation: overhead electric radiant heaters that add a steady increment of heat to 30-square-meter plots, advancing snowmelt, warming soils, and drying them out. The space-for-time substitution approach complements these experiments by comparing sites along elevation gradients, treating today's lower-elevation conditions as a stand-in for tomorrow's higher-elevation climate.
Several ecological ideas thread through the findings below. Litter quality — the chemistry of dead plant material, especially the ratio of lignin to nitrogen — controls how quickly soil microbes can decompose it and return carbon to the atmosphere. A climate-ecosystem feedback occurs when warming changes vegetation or soils in ways that either amplify (positive feedback) or dampen (negative feedback) the original warming. Foundation species like big sagebrush (Artemisia tridentata) structure entire communities, so shifts in their abundance ripple outward. Finally, the maximum entropy theory of ecology (METE) and related species-area relationships are mathematical tools developed in part at RMBL that predict how species richness and abundance should be distributed in undisturbed communities — and, importantly, where those predictions break down when ecosystems are stressed.
The RMBL warming experiment began in 1991 when overhead infrared heaters were installed across a moisture and vegetation gradient in a montane meadow. The first major synthesis showed that adding roughly 15 watts per square meter advanced snowmelt by about a week, raised summer soil temperatures by up to 3 degrees Celsius, and reduced soil moisture by as much as 25 percent — with the strongest temperature responses in the drier, more sparsely vegetated upper zone of each plot . That study established infrared heating as a viable way to simulate warming in a natural community and revealed that responses depend strongly on where a plot sits along the moisture gradient.
Manipulative experiments that alter abiotic conditions or reciprocally transplant individuals to understand and predict the effects of environmental c...
Changes in network composition between treatments, partitioned into species turnover versus interaction rewiring components
The positive relationship between species richness and the surveyed area, described by the power-law S=cA^z where c is the intercept and z measures th...
SPAD measurement of leaf chlorophyll concentration indicating photosynthetic capacity
Theory providing mass-metabolism scaling rules that relate metabolic rate to organism mass through allometric relationships
Ecosystem responses to climate change that exert positive or negative feedbacks on climate, mediated by slow-moving factors such as shifts in vegetati...
Theory that predicts patterns of distribution, abundance, and energetics using instantaneous values of community state variables including total area,...
Systematic excavation of 1-meter soil pits with depth-stratified sampling at 10 cm intervals for soil organic carbon, nitrogen, and dissolved organic ...
Infrared heaters suspended above experimental plots to simulate warming effects on montane vegetation communities across moisture gradients. Heating p...
A novel approach to measure light response curves for entire plant communities rather than individual plants using tent-based gas exchange measurement...
Measurement of chlorophyll fluorescence using LI-600 to assess photosynthetic efficiency by quantifying light emission from chlorophyll molecules exci...
Application of METE mathematical framework to predict species-area relationships and species-abundance distributions based on community state variable...
Systematic measurement of plant morphological characteristics (leaf number, leaf area, stalk count, etc.) before plant extraction to develop predictiv...
The data set consists of strontium (Sr) isotope ratios (87Sr/86Sr), water isotopes, soil cation concentrations, soil water potential sensor data, and ...
This is data collected to explore the impacts of warming and dominant species removal on the quantity and quality of plants for cattle foraging. The d...
Macroecological data sets, their state variables, and various calculated metabolic quantities for tests of the Maximum Entropy Theory of Ecology. Thes...
<p>This map is a soil moisture proxy derived from analysis of the UG 1m hydrologically corrected digital elevation model. The intuition behind this ma...
This dataset contains measurements from a hand-held FieldScout TDR Soil Moisture Meter within the 0-10 cm soil depth of: Time (UTC), GPS locations, El...
A broader conceptual framework soon followed, laying out how warming experiments should be designed and interpreted differently from earlier carbon-dioxide enrichment studies (Shaver et al., 2000). Within a few years, researchers at the Warming Meadow had documented the first phenological responses: experimental warming advanced flowering by roughly two weeks across eleven subalpine species, and snowmelt date emerged as the single most important driver of flowering timing (Dunne et al., 2003). Parallel work showed that warming reshuffled the carbon balance of the meadow, altering when and how much carbon plants took up and released (Saleska et al., 1999).
The most consistent result across decades of work is that warming dries soils and shifts plant communities away from productive forbs toward woody shrubs. A ten-year synthesis found that heated plots lost about 200 grams of carbon per square meter from soil organic matter, and the culprit was not faster microbial decomposition but a shift in plant community composition from high-productivity forbs to low-productivity shrubs, which reduced the amount and quality of plant litter entering the soil (Saleska et al., 2002). A later analysis spanning 23 years of warming confirmed that snowmelt advanced by an average of 7.7 days and that shrub encroachment continued to drive long-term soil carbon feedbacks (convergent ecosystem responses study, 2015). A subsequent global synthesis of 27 warming experiments reinforced the local pattern: warming reliably dries soils, but the temperature sensitivity of soil respiration itself changes little with experimental warming (Carey et al., 2016).
Individual species and trophic groups respond idiosyncratically. Warming reduced flower production by nearly 29 percent in glacier lily (Erythronium grandiflorum) and 49 percent in larkspur (Delphinium nuttallianum) while leaving other species unaffected (reproductive responses study, 2007). Plants in earlier-melting plots accumulated more damage from a wider range of pathogens and herbivores, though individual attacker species varied in their responses (Roy et al., 2004). Nitrogen cycling responded only in the drier sagebrush zone, where gross mineralization rates doubled in the first two years before returning to baseline (Shaw & Harte, 2001). Aboveground, sagebrush biomass increased in the dry zone while the dominant grass tufted hairgrass (Deschampsia cespitosa) declined in the wet zone (Rodriquez, 2022), and one alpine forb, Androsace septentrionalis, went locally extinct in a heated plot (climate warming extinction study, 2018).
A parallel theoretical program at RMBL developed the maximum entropy theory of ecology, which uses information entropy to predict patterns of biodiversity, abundance, and energy use from a few community-level numbers (Harte & Newman, 2014). The theory successfully predicts a universal species-area curve across diverse ecosystems (Harte et al., 2009) and, more recently, an equation of state linking species richness, biomass, abundance, and energy flow that captured the patterns in 42 datasets (Harte et al., 2022).
Early work in the 1990s and 2000s established that warming dries soils, advances snowmelt, and shifts community composition. Recent studies since 2020 have shifted focus to two new questions: how macroecological theory itself behaves under disturbance, and how soil carbon is redistributed rather than simply lost. A six-year study of a stressed alpine plant community showed that species-area and species-abundance patterns increasingly deviated from static maximum entropy predictions as the community lost roughly 10 percent of its species, with mortality and declining recruitment driving the breakdown (Franzman et al., 2021). To address this, researchers developed DynaMETE, a dynamic version of the theory that incorporates explicit mechanisms of disturbance such as shifts in birth, growth, and migration rates (Harte et al., 2021).
New soil carbon work suggests the picture is more nuanced than early experiments implied. A recent thesis found that warming and removal of dominant species shifted soil organic carbon from deeper to shallower layers without changing the total amount stored, and that early snowmelt had no detectable effect on total soil carbon (Waldron, 2023). Along an elevation gradient, soil moisture emerged as the best single predictor of soil carbon, explaining about 23 percent of the variation (Issa, 2022). Microbial activity declined sharply with soil depth, complicating predictions about deep-soil carbon vulnerability (long-term warming microbial study, 2019).
Several major questions remain. How will compounded stresses — warming, drought, altered snowpack, and species loss — interact over the coming decades, and can dynamic theories like DynaMETE predict community trajectories accurately enough to guide management? Will the transient soil carbon losses observed in early decades of warming reverse, stabilize, or accelerate as shrub-dominated communities mature, and how do redistributions of carbon across soil depths affect long-term storage? How will idiosyncratic species responses — local extinctions in some species, compensation by others — reshape pollination, herbivory, and decomposition networks? Answering these questions will require continued long-term experimentation at sites like the Warming Meadow, paired with elevation-gradient studies and the next generation of macroecological theory.
Carey, J. C. et al. (2016). Temperature response of soil respiration largely unaltered with experimental warming. PNAS. →
Climate Warming Drives Local Extinction (2018). →
Convergent ecosystem responses to 23-year ambient and manipulated warming (2015). →
Dunne, J. A., Harte, J., Taylor, K. J. (2003). Subalpine meadow flowering phenology responses to climate change: integrating experimental and gradient methods. Ecological Monographs. →
Franzman, J. et al. (2021). Shifting macroecological patterns and static theory failure in a stressed alpine plant community. Ecosphere. →
Harte, J. et al. (2022). An equation of state unifies diversity, productivity, abundance and biomass. Communications Biology. →
Harte, J., Newman, E. A. (2014). Maximum information entropy: a foundation for ecological theory. Trends in Ecology and Evolution. →
Harte, J., Smith, A. B., Storch, D. (2009). Biodiversity scales from plots to biomes with a universal species-area curve. Ecology Letters. →
Harte, J., Torn, M. S., Chang, F.-R., Feifarek, B., Kinzig, A. P., Shaw, R., Shen, K. (1995). Global warming and soil microclimate: results from a meadow-warming experiment. Ecological Applications. →
Harte, J., Umemura, K., Brush, M. (2021). DynaMETE: a hybrid MaxEnt-plus-mechanism theory of dynamic macroecology. Ecology Letters. →
Issa (2022). The Effect of Climate Change on Soil Organic Carbon over an Elevational Gradient. →
Reproductive and physiological responses to simulated climate warming for four subalpine species (2007). →
Rodriquez (2022). Abundance and Identification of Hymenopteran Parasitoids in Euphydryas gilletti. →
Roy, B. A., Gusewell, S., Harte, J. (2004). Response of plant pathogens and herbivores to a warming experiment. Ecology. →
Saleska, S. R. et al. (2002). Plant community composition mediates both large transient decline and predicted long-term recovery of soil carbon under climate warming. Global Biogeochemical Cycles. →
Saleska, S. R., Harte, J., Torn, M. S. (1999). The effect of experimental ecosystem warming on CO2 fluxes in a montane meadow. Global Change Biology. →
Shaver, G. R. et al. (2000). Global warming and terrestrial ecosystems: a conceptual framework for analysis. BioScience. →
Shaw, M. R., Harte, J. (2001). Response of nitrogen cycling to simulated climate change: differential responses along a subalpine ecotone. Global Change Biology. →
The impacts of long term warming on potential soil microbial activity across soil depth (2019). →
Waldron (2023). Exploring the impact of climate change on soil carbon storage in montane meadows. →
Distribution of metabolic rates over individuals in a community, obtained by summing over abundance
Reduction in population growth rates, size, or occurrence across species ranges
A quantitative measure of uncertainty about an outcome of a draw from a probability distribution
Species best suited for the environment that make up most of the vegetation in early successional stages
Statistical inference procedure that selects flattest probability distributions compatible with constraints imposed by prior knowledge
Ability of plants to survive exposure to elevated temperatures, measured as lethal temperature causing 50% electrolyte leakage (LT50)
Assumption that spatial differences in environmental conditions can predict temporal responses to environmental change
Loss of cellular electrolytes through compromised cell membranes, used as indicator of heat stress damage
Species that define ecosystems and provide critical habitat structure, where big sagebrush is a foundation species in steppe ecosystems of western Nor...
A statistical distribution commonly observed in species abundance patterns, predicted by METE for undisturbed communities
The principle asserting an inverse relationship between local population density and average metabolic rate of individuals in a species
Extrapolation of species richness estimates from small plots to larger spatial scales using theoretical scaling relationships
Overland flow that occurs when rainfall intensity exceeds the rate at which water can enter the soil
The movement of eroded soil and rock particles by water flow
Model developed to determine LARs based on SAR and simple properties of food webs including species richness, number of links and connectance
Distinct layers in soil profile with different physical and chemical properties
A series of sites of different ages since disturbance used to infer temporal changes in ecological processes
The rate at which temperature decreases with elevation, typically expressed as degrees Celsius per kilometer
Controlled temperature treatments from 15-65°C applied to detached leaves for 1 hour, with temperature ramped at 2°C/hour. Used to determine lethal te...
Visual counting method for arthropods on sagebrush plants involving systematic counting of mobile species first (to avoid double-counting) followed by...
Systematic measurement of slope and aspect at grid cell centers using compass and clinometer with clipboard to minimize micro-scale surface variation ...
Paired sampling of vegetation inside exclosures before and after controlled grazing events to quantify herbivore impacts on standing crop biomass.
Calculation of Shannon diversity index (ln type) and Simpson dominance index (1-D) from species count data using online biodiversity calculator. Stand...
Complete census of sagebrush individuals within systematic 16m × 16m grids divided into 1m² cells, with measurement of plant dimensions for size estim...