
Michael G RyanColorado State University | CSU · Department of Ecosystem Science and Sustainability
Michael G Ryan
PhD, Oregon State University
About
258
Publications
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Introduction
Whole tree physiology and carbon cycling in forest ecosystems, including 1) changes in tree physiology and ecosystem processes with tree age; 2) carbon allocation; 3) productivity; 4) causes of tree mortality; 5) plant respiration and productivity; 6) ecosystem respiration, soil carbon and nitrogen interactions, decomposition of soil carbon; 7) disturbance effects on landscape carbon cycling; and 8) coordination of carbon, water and nutrients at whole tree level.
Additional affiliations
October 2012 - present
January 1990 - September 2012
January 1990 - December 2011
Publications
Publications (258)
The height of woody plants is a defining characteristic of forest and shrubland ecosystems because height responds to climate, soil and disturbance history. Orbiting LiDAR instruments, Ice, Cloud and land Elevation Satellite-2 (ICESat-2) and Global Ecosystem Dynamics Investigation LiDAR (GEDI), can provide near-global datasets of plant height at pl...
Species‐rich forests can produce litter of varying carbon (C) and nitrogen (N) composition (i.e. quality), which can affect decomposition and play a central role in long‐term soil organic carbon (SOC) accumulation. However, how differences in litter quality affect SOC decomposition and formation remains unclear over the full litter decomposition tr...
This article is a Commentary on Marshall et al. (2023), 239: 2166–2179.
Categorization of soil organic carbon (SOC) into different functional subpools according to their recalcitrance and protective mechanisms helps better understand ecosystems organic carbon (OC) dynamics, and various attempts have been made to explore the suitable experimental fractionation method for such purpose. However, most previous studies negl...
Plant survival depends on a balance between carbon supply and demand. When carbon supply becomes limited, plants buffer demand by using stored carbohydrates (sugar and starch). During drought, NSCs (non-structural carbohydrates) may accumulate if growth stops before photosynthesis. This expectation is pervasive, yet few studies have combined simult...
Short-term plant respiration (R) increases exponentially with rising temperature, but drought could reduce respiration by reducing growth and metabolism. Acclimation may alter these responses. We examined if species with different drought responses would differ in foliar R response to +4.8°C temperature and -45% precipitation in a field experiment...
The area of tropical secondary forests is increasing rapidly, but data on the physical and biological structure of the canopies of these forests are limited. To obtain such data and to measure the ontogeny of canopy structure during tropical rainforest succession, we studied patch-scale (5 m²) canopy structure in three areas of 18–36 year-old secon...
Background: Because soil organic carbon (SOC) variation is a result of its physicochemical protection, fractionating SOC into different functional subpools according to its protection mechanism and studying the mechanism of different SOC fractions’ responses to environmental change will help guide the study of SOC dynamics. Therefore, we conducted...
Fundamental knowledge about the processes that control the functioning of the biophysical workings of ecosystems has expanded exponentially since the late 1960s. Scientists, then, had only primitive knowledge about C, N, P, S, and H2O cycles; plant, animal, and soil microbial interactions and dynamics; and land, atmosphere, and water interactions....
Cross-site patterns for multiple sites tend to be more broadly applicable and more useful for constructing and constraining models. We examined cross-site patterns of Eucalyptus plantation response to water supply (including irrigation and 1/3 precipitation removal), mean annual temperature (MAT), vapor pressure deficit during the daytime (VPD), an...
Forest plantations have a large potential for carbon sequestration, playing an important role in the global carbon cycle. However, despite the large amount of research carried out worldwide, the absolute contribution of forest plantations is still incomplete for some parts of the world. To help bridge this gap, we calculated the amount of C stock i...
Forest plantations have a large potential for carbon sequestration, playing an important role in the global carbon cycle. However, despite the large amount of research carried out worldwide, the absolute contribution of forest plantations is still incomplete for some parts of the world. To help bridge this gap, we calculated the amount of C stock i...
Forest plantations have a large potential for carbon sequestration, playing an important role in the global carbon cycle. However, despite the huge amount of research carried out worldwide, the absolute contribution of industrial forest plantations is still incomplete for some parts of the world. To contribute to bridge this gap, we calculated the...
Clonal plantations of Eucalyptus are among the most productive forests in the world, with intensification of silviculture and genetic breeding doubling the wood mean annual increments over the past four decades. The TECHS Project demonstrated that even with intensive silviculture, wood production varies by more than twofold across environmental gra...
Plant water deficits arise from low soil water and high atmospheric demand for water (expressed as vapor pressure deficit; VPD). Soil water and VPD often covary making it difficult to examine the effect of only VPD on biomass production. We used four Eucalyptus plantation sites where one treatment maintained high soil water with irrigation to evalu...
Two simplifying hypotheses have been proposed for whole‐plant respiration. One links respiration to photosynthesis; the other to biomass. Using a first‐principles carbon balance model with a prescribed live woody biomass turnover, applied at a forest research site where multidecadal measurements are available for comparison, we show that if turnove...
Two simplifying hypotheses have been proposed for whole-plant respiration. One links respiration to photosynthesis; the other to biomass. Using a first-principles carbon balance model with a prescribed live woody biomass turnover, we show that if turnover is fast, the accumulation of respiring biomass is low and respiration depends primarily on pho...
This article is a Commentary on Drake et al. (2019a), 222: 1298–1312 and Drake et al. (2019b), 222: 1313–1324.
Background: Soil organic carbon (SOC) is a large reservoir of terrestrial carbon (C); it consists of different fractions of varying complexity and stability. Partitioning SOC into different pools of decomposability help better predict the trend of changes in SOC dynamics under climate change. Information on how physical fractions and chemical struc...
Background: Soil organic carbon (SOC) is a large reservoir of terrestrial carbon (C); it consists of different fractions of varying complexity and stability. Partitioning SOC into different pools of decomposability help better predict the trend of changes in SOC dynamics under climate change. Information on how physical fractions and chemical struc...
Landscape carbon (C) flux estimates help assess the ability of terrestrial ecosystems to buffer further increases in anthropogenic carbon dioxide (CO2) emissions. Advances in remote sensing have led to coarse-scale estimates of gross primary productivity (GPP; e.g., MODIS 17), yet efforts to develop spatial respiration products are lacking. Here we...
p>Resistance to moving sugars from foliage to roots is high in trees, suggesting that the transport mechanism found in herbs might not work in trees. Now with new measurements of phloem structure and leaf turgor pressure, it has been shown that the Münch pressure-flow hypothesis can also explain sugar transport in tall trees.</p
In subalpine forests where snowpacks can persist for 50% of the year or longer, wintertime subnivean soil respiration constitutes a significant, but poorly understood, portion of the carbon (C) cycle. The temporal and seasonal dynamics of this flux are difficult to measure compared to snow-free respiration. This makes it challenging to fully addres...
For more accurate projections of both the global carbon (C) cycle and the changing climate, a critical current need is to improve the representation of tropical forests in Earth system models. Tropical forests exchange more C, energy, and water with the atmosphere than any other class of land ecosystems. Further, tropical-forest C cycling is likely...
Changes in tropical forest carbon sink strength during El Niño Southern Oscillation ( ENSO ) events can indicate future behavior under climate change. Previous studies revealed ˜6 Mg C ha ⁻¹ yr ⁻¹ lower net ecosystem production ( NEP ) during ENSO year 1998 compared with non‐ ENSO year 2000 in a Costa Rican tropical rainforest. We explored environm...
Widespread tree mortality associated with drought has been observed on all forested continents and global change is expected to exacerbate vegetation vulnerability. Forest mortality has implications for future biosphere-atmosphere interactions of carbon, water and energy balance, and is poorly represented in dynamic vegetation models. Reducing unce...
For more accurate projections of both the global carbon (C) cycle and the changing climate, a critical current need is to improve the representation of tropical forests in Earth system models. Tropical forests exchange more C, energy, and water with the atmosphere than any other class of land ecosystems. Further, tropical-forest C cycling is likely...
Mulching fuels treatments have been increasingly implemented by forest managers in the western USA to reduce crown fire hazard. These treatments use heavy machinery to masticate or chip unwanted shrubs and small-diameter trees and broadcast the mulched material on the ground. Because mulching treatments are relatively novel and have no natural anal...
Widespread tree mortality associated with drought has been observed on all forested continents and global change is expected to exacerbate vegetation vulnerability. Forest mortality has implications for future biosphere–atmosphere interactions of carbon, water and energy balance, and is poorly represented in dynamic vegetation models. Reducing unce...
Predicted increases in the frequency and intensity of droughts across the temperate biome have highlighted the need to examine the extent to which forests may differ in their sensitivity to water stress. At present, a rich body of literature exists on how leaf- and stem-level physiology influence tree drought responses; however, less is known regar...
Shaped by the hydrology of the Kissimmee-Okeechobee-Everglades watershed, the Florida Everglades is composed of a conglomerate of wetland ecosystems that have varying capacities to sequester and store carbon. Hydrology, which is a product of the region’s precipitation and temperature patterns combined with water management policy, drives community...
In forests, total belowground carbon (C) flux (TBCF) is a large component of the C budget and represents a critical pathway for delivery of plant C to soil. Reducing uncertainty around regional estimates of forest C cycling may be aided by incorporating knowledge of controls over soil respiration and total belowground C flux (TBCF). Photosynthesis,...
Many studies and production inventory systems have shown the utility of coupling covariates derived from Light Detection and Ranging (LiDAR) data with forest variables measured on georeferenced inventory plots through regression models. The objective of this study was to propose and assess the use of a Bayesian hierarchical modeling framework that...
Nature Plants is a scientific journal publishing primary research papers concerned with all aspects of plant biology, technology, ecology and evolution.
Non-structural carbohydrates (NSC) in plant tissue are frequently quantified to make inferences about plant responses to environmental conditions. Laboratories publishing estimates of NSC of woody plants use many different methods to evaluate NSC. We asked whether NSC estimates in the recent literature could be quantitatively compared among studies...
Mountain pine beetle-caused tree mortality has substantially changed live tree biomass in lodgepole pine ecosystems in western North America since 2000. We studied how beetle-caused mortality altered ecosystem carbon (C) stocks and productivity using a central US Rockies age sequence
of ecosystem recovery after infestation, augmented with growth-an...
Shaped by the hydrology of the Kissimmee-Okeechobee-Everglades watershed, the Florida
Everglades is composed of a conglomerate of wetland ecosystems that have varying capacities to sequester
and store carbon. Hydrology, which is a product of the region’s precipitation and temperature patterns
combined with water management policy, drives community...
How trees sense source-sink carbon balance remains unclear. One potential mechanism is a feedback from non-structural carbohydrates regulating photosynthesis and removing excess as waste respiration when the balance of photosynthesis against growth and metabolic activity changes. We tested this carbohydrate regulation of photosynthesis and respirat...
As tropical forests respond to environmental change, autotrophic respiration may consume a greater proportion of carbon fixed in photosynthesis at the expense of growth, potentially turning the forests into a carbon source. Predicting such a response requires that we measure and place autotrophic respiration in a complete carbon budget, but extrapo...
This research examines the relationships between El Niñ o Southern Oscillation (ENSO), water level, precipitation patterns and carbon dioxide (CO 2) exchange rates in the freshwater wetland ecosystems of the Florida Everglades. Data was obtained over a 5-year study period (2009–2013) from two freshwater marsh sites located in Everglades National Pa...
During the twenty-first century, tree mortality from forest disturbances may switch the United States from a current carbon sink (offsetting 13 % of U.S. fossil fuel greenhouse gas emissions) to a source. Carbon losses from disturbances in western U.S. forests (insects, wildfire) may be partially offset by increased growth in the East, where water...
Background
Forests store large amounts of carbon in forest biomass, and this carbon can be released to the atmosphere following forest disturbance or management. In the western US, forest fuel reduction treatments designed to reduce the risk of high severity wildfire can change forest carbon balance by removing carbon in the form of biomass, and by...
Eddy covariance nighttime fluxes are uncertain due to potential measurement biases. Many studies report eddy covariance nighttime flux lower than flux from extrapolated chamber measurements, despite corrections for low turbulence. We compared eddy covariance and chamber estimates of ecosystem respiration at the GLEES Ameriflux site over seven growi...
Background/Question/Methods
Soil respiration contributes > 75% of the annual ecosystem respiration in water-limited terrestrial ecosystems and is roughly equivalent to plant belowground carbon flux at an annual scale. As the frequency and intensity of drought increases in the southwestern US, changes in plant available water will likely change ec...
Plant carbon balance determines growth, carbon storage and perhaps resistance to stress. Most terrestrial carbon cycle models and measurements of plant carbon balance assume that photosynthesis drives growth. This assumption is wrong because the environmental controls of growth are more sensitive than those of photosynthesis. Consequences: models w...
We analyzed energy partitioning in short- and long-hydroperiod freshwater marsh ecosystems in the Florida Everglades by examining energy balance components (Eddy Covariance derived latent energy (LE) and sensible heat (H) flux). The study period included several wet and dry seasons and variable water levels, allowing us to gain better mechanistic i...
The Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O,
Organics & Nitrogen (BEACHON) project seeks to understand the feedbacks
and inter-relationships between hydrology, biogenic emissions, carbon
assimilation, aerosol properties, clouds and associated feedbacks within
water-limited ecosystems. The Manitou Experimental Forest Obser...
The Florida Everglades is composed of a conglomerate of wetland ecosystems that have varying capacities to sequester and store carbon. Hydrology drives the productivity of Everglades ecosystems, which is ultimately a product of the region’s precipitation patterns. As shifts in both air temperature and precipitation are expected over the next 100 ye...
This research examines variations in precipitation, water level and carbon dioxide (CO2) exchange rates in the freshwater wetland ecosystems of the Florida Everglades in response to phase changes in the El Niño Southern Oscillation (ENSO). Teleconnections from ENSO are known to affect global climate and have been associated with precipitation and w...
The Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen (BEACHON) project seeks to understand the feedbacks and inter-relationships between hydrology, biogenic emissions, carbon assimilation, aerosol properties, clouds and associated feedbacks within water-limited ecosystems. The Manitou Experimental Forest Obser...
Nutrient supply often limits growth in forest ecosystems and may limit the response of growth to an increase in other resources, or to more favorable environmental factors such as temperature and soil water. To explore the consequences and mechanisms of optimum nutrient supply for forest growth, the Flakaliden research site was established in 1986...
Model–data comparisons of plant physiological processes provide an understanding of mechanisms underlying vegetation responses to climate. We simulated the physiology of a piñon pine–juniper woodland ( Pinus edulis–Juniperus monosperma ) that experienced mortality during a 5 yr precipitation‐reduction experiment, allowing a framework with which to...
Abstract
This report describes the database used to compile, store, and manage intensive ground-based biometric data collected at research sites in Colorado, Minnesota, New Hampshire, New Jersey, North Carolina, and Wyoming, supporting research activities of the U.S. North American Carbon Program (NACP). This report also provides details of each si...
Background/Question/Methods
In recent decades, forest mortality due to bark beetle infestation in conifer forests of western North America has reached epidemic levels, which may have profound effects on net primary production, heterotrophic respiration (Rh), and hence the net carbon flux between forest and atmosphere (NEE). The response of Rh to...
Background/Question/Methods In our largely water limited world, plants that could photosynthesize and produce more biomass with less water would be a boon for agriculture and forestry. Carbon isotopic discrimination during photosynthesis is linearly related to the intrinsic water use efficiency of photosynthesis at the leaf level, and 13C discrimin...
Background/Question/Methods
Drought and temperature-induced tree mortality is believed to be occurring globally, though the physiological mechanisms underlying documented mortality events are not well understood. Understanding the controls on forest carbon cycling and their responses during drought and temperature stress is critical in informing...
Background/Question/Methods
Individual tree species differ in morphology, phenology, tissue chemistry, and resource use, and these differences can affect ecosystem carbon cycling. To what extent do tree species differ in respiration, photosynthesis, and carbon partitioning at the ecosystem level? We examined this question using experimental plant...
Hydrology drives the carbon balance of wetlands by controlling the uptake and release of CO2 and CH4 . Longer dry periods in between heavier precipitation events predicted for the Everglades region, may alter the stability of large carbon pools in this wetland's ecosystems. To determine the effects of drought on CO2 fluxes and CH4 emissions, we sim...