Herman H. Shugart

University of Virginia | UVa · Department of Environmental Sciences

Wood growth is an important process of carbon sequestration and plant physiology in forest ecosystems. Hence, understanding and predicting wood growth is central to quantifying forest carbon cycling. Current dynamic global vegetation models (DGVMs) are mainly driven by carbon inputs (e.g., Gross Primary Production, GPP). However, observations indic...

The earth's forests are havens of nature supporting a diversity of life. Shaped by climate and geography, these vast and dynamic wooded spaces offer unique ecosystems that shelter complex and interdependent webs of flora, fungi, and animals. The World Atlas of Trees and Forests offers a beautiful introduction to what forests are, how they work, how...

Process-based ecological models are essential tools to quantify and predict forest growth and carbon cycles under the background of climate change. The accurate description of phenology and tree growth processes enables an improved understanding and predictive modeling of forest dynamics. An individual tree-based carbon model, FORCCHN2 (Forest Ecos...

Three options for the sampling design of the field plot clusters of NAFORMA II biophysical survey are compared in this report. Option 1 consists of re-measuring all NAFORMA I field sample plots (3 205 clusters) and Option 2 of re-measuring only those that were established as permanent (848 clusters). The recommended Option 3 is a compromise betwe...

Leaf phenology regulates multiple aspects of plant vital activities and provides feedback to climate change. Despite its importance, an effective parameterization method to predict continental‐scale leaf phenology has been elusive. Here, we aimed to develop a new parameterization method using local climatic conditions instead of species or plant fu...

Process-based ecological models are essential tools to quantify and predict forest growth and carbon cycle under the background of climate change. The accurate description of phenology and tree growth processes enables an improved understanding and predictive modeling of forest dynamics. An individual tree-based carbon model, FORCCHN2 (FORest ecosy...

Vegetation growth is often limited by the availability of soil mineralized N (Nm), and Nm dynamics are important to forest productivity and succession. However, current dynamic global vegetation models (DGVMs) do not fully mechanistically represent the linkage between plants, microbes, and soil. Here, we sought to develop and test a DGVM with an ex...

Miombo woodlands are the most extensive dry forest type in southern Africa, covering ca. 1.9 million km² across seven countries. Fire is a key ecosystem process that has structured miombo for the last 200,000 years. However, how fires affect the ecosystem's functioning is not well understood. In this study, we used the individual-based forest model...

The growth of forests and the feedbacks between forests and environmental changes are central issues in the planetary carbon cycle, global climate change, and basic plant ecology. A challenge to understanding both growth and feedbacks from local to global scales is that many critical metabolic processes vary among species. An innovation in solving...

Process-based biogeochemical models are valuable tools to evaluate impacts of environmental or management changes on the greenhouse gas (GHG) balance of forest ecosystems. We evaluated LandscapeDNDC, a process-based model developed to simulate carbon (C), nitrogen (N) and water cycling at ecosystem and regional scales, against eddy covariance and s...

Climate change is affecting the growth and distribution of trees in the Chinese boreal forest. Such changes in China, the southern terminus of the extensive Eurasian boreal forests, reflect on the changes that could occur further north under a warming climate. Most studies have found that tree growth increases with increasing temperature and precip...

1. Carbon sequestration is a key ecosystem service provided by forests. Inventory data based on individual trees are considered to be the most accurate method for estimating forest productivity. However, estimations of forest photosynthesis itself from inventory data remains understudied, particularly when considering the growth and development of...

This study is the first to find the unexpected increases in albedo due to forest greening, which has important implications in research of land‐surface energy‐balance and the forest‐climate feedback. We investigated interannual changes of vegetation and albedo for forests and grassland during the main growing period, May to September, between 2002...

Background Gap models are individual-based models for forests. They simulate dynamic multispecies assemblages over multiple tree-generations and predict forest responses to altered environmental conditions. Their development emphases designation of the significant biological and ecological processes at appropriate time/space scales. Conceptually, t...

Diffuse radiation produces a higher light use efficiency (LUE) than does direct radiation. However, light components and their impacts on interannual variations of photosynthesis in China have not been intensively studied. We estimated gross primary production (GPP) from a two‐leaf LUE model that incorporates a diffuse radiation effect and compared...

Forest ecosystems are an important sink for terrestrial carbon sequestration. Hence, accurate modeling of the intra‐ and interannual variability of forest photosynthetic productivity remains a key objective in global biology. Applying climate‐driven leaf phenology and growth in models may improve predictions of the forest gross primary productivity...

Climate warming generally is expected to increase drought, but arguments about China's past drought trends persist. PDSIARTS, a revised self‐calibrating Palmer Drought Severity Index, was computed for China over 1982–2016 using satellite leaf‐area indices combined with monthly climate data interpolated from 2000 high‐density stations. Drought clima...

The boreal zone of Alaska is dominated by interactions between disturbances, vegetation, and soils. These interactions are likely to change in the future through increasing permafrost thaw, more frequent and intense wildfires, and vegetation change from drought and competition. We utilize an individual tree-based vegetation model, the University of...

Forest mortality is accelerating due to climate change and the largest trees may be at the greatest risk, threatening critical ecological, economic, and social benefits. Here, we combine high-resolution airborne LiDAR and optical data to track tree-level mortality rates for ~2 million trees in California over 8 years, showing that tree height is th...

Investigations into the impacts of vegetation-emitted biogenic volatile organic carbon emissions (BVOCs) on atmospheric processes and the subsequent impacts of these changes on vegetation have been ongoing since the 1950s 1,2 (Fig. 1). Recently, Rap et al.3 explicitly examined the radiative effects of aerosols formed from BVOCs on plant productivit...

Nonstructural carbohydrates (NSC) are considered important in the metabolism of wood plants, and they are highly dynamic. Accurate and detailed modelling of NSC dynamics may increase understanding of physiological processes. We constructed a physiological model that simulates NSC dynamics from photosynthesis, transpiration and growth carbon demand....

Wetlands hold the highest density of belowground carbon stocks on earth, provide myriad biogeochemical and habitat functions, and are at increasing risk of degradation due to climate and land use change. Microtopographic variation is a common and functionally important feature of wetlands but is challenging to quantify, constraining estimates of th...

Forests provide important ecosystem services such as carbon sequestration. Forest landscapes are intrinsically heterogeneous—a problem for biomass and productivity assessment using remote sensing. Forest structure constitutes valuable additional information for the improved estimation of these variables. However, survey of forest structure by remot...

Whether enhanced sunshine increases photosynthesis in Amazon rainforests during drought is unclear. Here we used a light component‐based two‐leaf‐photosynthesis model, driven with climate data and satellite vegetation data, to inspect the controlling mechanisms among climate factors on gross primary production (GPP) during the 2015/2016 El Niño dro...

Differences, arising from differences in gross primary production (GPP) model structures and driving forces, have fueled arguments concerning interannual changes of GPP in China since 2000. To better investigate the interannual variability of GPP and its covariance with climate factors in China, this study adopted a multi‐model analysis based on th...

In our recent article in Global Change Biology (Wang et al., 2019), we proposed to develop aggregate‐based models (ABMs) based on a view of soil aggregates as biogeochemical reactors in the context of soil heterogeneity. Using a bottom‐up philosophy, we argued for developing ABMs based on a systematic and dynamic view of soils as a constellation of...

Aim: Climate and disturbance alter forest dynamics, from individual trees to biomes and from years to millennia, leaving legacies that vary with local, meso‐ and macroscales. Motivated by recent insights in temperate forests, we argue that temporal and spatial extents equivalent to that of the underlying drivers are necessary to characterize fores...

These supplementary tables (.xls) tabulate in more detail than the tables presented in the manuscript the information associated with each existing studies on aggregate-scale GHGs. Could be very good resources to tap for next step research on soil aggregate-level activities.

This supporting text documents some existing equations that would be helpful for developing an aggregate-based model as proposed in the main text.

Dynamic changes in forest structure drive trends in ecosystem-level photosynthesis globally, but gross primary production (GPP) and forest structure remain challenging to accurately quantify in detail across space and time. Most estimates of GPP are based on modeling and flux observations, but both approaches are indirect and coarse in spatial scal...

Soil‐atmosphere exchange significantly influences the global atmospheric abundances of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). These greenhouse gases (GHGs) have been extensively studied at the soil profile level and extrapolated to coarser scales (regional and global). However, finer scale studies of soil aggregation have not...

In the subalpine zone of the Rocky Mountains, climate change is predicted to result in an increase in the frequency and severity of spruce beetle outbreaks. Climate change itself may affect vegetation, potentially leading to changes in species composition. The direct and indirect effects of climate and disturbances on forest composition, biomass, a...

Additional analysis relevant to "Assessing terrestrial laser scanning for developing non-destructive biomass allometry."

Forests provide essential ecosystem services and hold approximately 45% of global terrestrial carbon. Estimates of the quantity and spatial distribution of global forest carbon are built on the assumption that regional- or national-scale allometry accurately captures growth form across the wide spectrum of plant size. Allometry is painstaking and c...

This article contains data related to the research article entitled “Assessing terrestrial laser scanning for developing non-destructive biomass allometry” (Stovall et al., 2018 [1]) and presents 258 terrestrial LiDAR-derived estimates of tree volume and biomass. The terrestrial LiDAR acquisitions were completed in the Center for Tropical Forest Sc...

Ecological modeling and forecasting are essential tools for the understanding of complex vegetation dynamics. The parametric demands of some of these models are often lacking or scant for threatened ecosystems, particularly in diverse tropical ecosystems. One such ecosystem and also one of the world’s biodiversity hotspots, Madagascar’s lowland rai...

Air quality is closely associated with climate change via the biosphere because plants release large quantities of volatile organic compounds (VOC) that mediate both gaseous pollutants and aerosol dynamics. Earlier studies, which considered only leaf physiology and simply scale up from leaf-level enhancements of emissions, suggest that climate warm...

Air quality is closely associated with climate change via the biosphere because plants release large quantities of volatile organic compounds (VOC) that mediate both gaseous pollutants and aerosol dynamics. Earlier studies, which considered only leaf physiology and simply scale up from leaf‐level enhancements of emissions, suggest that climate warm...

Individual-based models (IBMs) of complex systems emerged in the 1960s and early 1970s, across diverse disciplines from astronomy to zoology. Ecological IBMs arose with seemingly independent origins out of the tradition of understanding the ecosystems dynamics of ecosystems from a 'bottom-up' accounting of the interactions of the parts. Individual...

Mountain forests provide the main water resources and lumber for Northwest China. The understanding of the differences in forests growing among individual slope aspects in mountainous regions is of great significance to the wise management and planning of these natural systems. The aim of this study was to investigate the impacts of slope aspect on...

Future NASA and ESA satellite missions plan to better quantify global carbon stocks through detailed observations of forest structure, but ultimately rely on uncertain ground measurement approaches for calibration and validation. A substantial amount of uncertainty in estimating plot-level biomass can be attributed to inadequate and unrepresentativ...

Future NASA and ESA satellite missions plan to better quantify global carbon stocks through detailed observations of forest structure, but ultimately rely on uncertain ground measurement approaches for calibration and validation. A substantial amount of uncertainty in estimating plot-level biomass can be attributed to inadequate and unrepresentativ...

During the past several decades, the Earth system has changed significantly, especially across Northern Eurasia. Changes in the socio-economic conditions of the larger countries in the region have also resulted in a variety of regional environmental changes that can have global consequences. The Northern Eurasia Future Initiative (NEFI) has been de...

Understanding the mechanism of photosynthetic seasonality in Amazonian evergreen forests is critical for its formulation in global climate and carbon cycle models. However, the control of the unexpected photosynthetic seasonality is highly uncertain. Here we use eddy-covariance data across a network of Amazonian research sites and a novel evapotran...

Diffuse radiation can increase canopy light use efficiency (LUE). This creates the need to differentiate the effects of direct and diffuse radiation when simulating terrestrial gross primary production (GPP). Here, we present a novel GPP model, the diffuse-fraction-based two-leaf model (DTEC), which includes the leaf response to direct and diffuse...

Tropospheric ozone (O3), a harmful secondary air pollutant, can affect climate via direct radiative forcing and by modifying the radiative forcing of aerosols through its role as an atmospheric oxidant. Moreover, O3 exerts a strong oxidative pressure on the biosphere and indirectly influences climate by altering the materials and energy exchange be...

This supporting document presents important analyses results supporting the major results presented in the main text, including the distribution of sites over the globe that have data on O3-GHGs.

The compiled data on ozone manipulation and soil CO2, CH4, and N2O flux from around the world conducted in the forest, cropland, and grassland.

A model is a simplification of our understanding of reality, but how much simplification is too much? We assessed model sensitivity for a new spatially-explicit individual-based gap model (IBM) SIBBORK to determine how spatial resolution (i.e., plot size) and explicit representation of light and space affect the simulated vegetation characteristics...

Rocky Mountain forests are highly important for their part in carbon cycling and carbon storage as well as ecosystem services such as water retention and storage and recreational values. These forests are shaped by complex interactions among vegetation, climate, and disturbances. Thus, climate change and shifting disturbances may lead to significan...

Siberia has experienced a pronounced warming over the past several decades, which has induced an increase in the extent of evergreen conifer forest. However, the potential slowing of the trend of increasing surface air temperature (SAT) has produced intense debate since the late 1990s. During this warming hiatus, the Siberian region experienced a s...

A model is a simplification of our understanding of reality, but how much simplification is too much? We assessed model sensitivity for a new spatially-explicit individual-based gap model (IBM) SIBBORK to determine how spatial resolution (i.e., plot size) and explicit representation of light and space affect the simulated vegetation characteristics...

Forests produce and emit abundant non-methane volatile hydrocarbon species (VOCs) influencing the atmosphere chemistry and climate. Over a half century of research has produced significant under-standings of the biochemistry and eco-physiology of biogenic VOCs. However, VOCs production is highly species-specific, and the impact of changes in specie...

Change in the Russian boreal forest has the capacity to alter global carbon and climate dynamics. Fire disturbance is an integral determinant of the forest's composition and structure, and changing climate conditions are expected to create more frequent and severe fires. Using the individual tree-based forest gap model UVAFME, along with an updated...

Wildfires release the greatest amount of carbon into the atmosphere compared to other forest disturbances. To understand how current and potential future fire regimes may affect the role of the Eurasian boreal forest in the global carbon cycle, we employed a new, spatially-explicit fire module DISTURB-F (DISTURBance-Fire) in tandem with a spatially...

Caribbean tropical forests are subject to hurricane disturbances of great variability. In addition to natural storm incongruity, climate change can alter storm formation, duration, frequency, and intensity. This model-based investigation assessed the impacts of multiple storms of different intensities and occurrence frequencies on the long-term dyn...

The carbon budget of forest ecosystems, an important component of the terrestrial carbon cycle, needs to be accurately quantified and predicted by ecological models. As a preamble to apply the model to estimate global carbon uptake by forest ecosystems, we used the CO2 flux measurements from 37 forest eddy-covariance sites to examine the individual...

Divergence among maps of global aboveground biomass carbon is primarily driven by spatial variation in allometric relationships. Measurements of canopy height using airborne or spaceborne LiDAR have led to improvements in forest carbon mapping, but plot-level estimates are almost entirely reliant on generalized regional, national-, or global-scale...

Spruce beetle (Dendroctonus rufipennis (Kirby)) outbreaks cause widespread mortality of Engelmann spruce (Picea engelmannii (Parry ex Engelm)) within the subalpine forests of the western United States. Early detection of infestations could allow forest managers to mitigate outbreaks or anticipate a response to tree mortality and the potential effec...