Heidi Renninger

Mississippi State University | MSU · Department of Forestry

Research has indicated the potential of using machine learning algorithms to automatically detect and measure stomata. However, the current limitation for further improving and fine-tuning machine learning-based stomatal study methods is due to the small, inconsistent, and monotypic nature of stomatal datasets, which are also not easily accessible....

The characteristics of stomata on leaves are crucial for the performance of plants and their impact on global water and carbon cycling. However, manually counting stomata can be time-consuming, prone to bias, and limited to small scales and sample sizes. We have created StoManager1, a high-throughput tool that automates detecting, counting, and mea...

Genetic improvement and hybridization in the Populus genus have led to the development of genotypes exhibiting fast growth, high rooting ability and disease resistance. However, while large biomass production is important for bioenergy crops, efficient use of resources including water is also important in sites lacking irrigation and for maintainin...

The southeastern USA is well suited for producing biomass with rapid growth on nonagricultural sites, and Populus spp. and hybrids contain the necessary traits for the production of biofuels and bioproducts. Identification of optimal Populus genotypes best suited for site conditions can increase productivity, but is difficult due to genotype × envi...

Eastern cottonwood ( Populus deltoides W. Bartram ex Marshall) and hybrid poplars are well-known bioenergy crops. With advances in tree breeding, it is increasingly necessary to find economical ways to identify high-performing Populus genotypes that can be planted under different environmental conditions. Photosynthesis and leaf nitrogen content ar...

Black willow and eastern cottonwood are fast-growing hardwoods native to river bottoms throughout the southeastern United States, e.g., the Lower Mississippi Alluvial Valley (LMAV), that are often grown as short rotation woody crops (SRWCs) because of their potential to provide high biomass yields in short periods of time. This study focused on dev...

The southeastern United States has wide-scale potential to achieve high productivity from elite eastern cottonwood and hybrid poplar varietals to produce renewable bioenergy and bioproducts. In order to determine how environmental drivers impact water use and growth so that individuals can maintain growth during drought periods, varietals that use...

For floodplain forests such as bottomland hardwood forests, large fluctuations in moisture availability can lead to stress from both flooded as well as drought conditions. Likewise, these forests can be diverse in species composition and the water use and drought strategies of co-occurring species will impact surrounding hydrology, nutrient dynamic...

Eucalyptus is one of the fastest growing hardwoods for bioenergy production. Currently, few modeling tools exist to simultaneously estimate soil hydrological processes, nitrogen (N) uptake, and biomass production in a eucalyptus plantation. In this study, a STELLA (Structural Thinking and Experiential Learning Laboratory with Animation)-based model...

Pyrophytic oak landscapes across the central and eastern United States are losing dominance as shade-tolerant, fire-sensitive, or opportunistic tree species encroach into these ecosystems in the absence of periodic, low-intensity surface fires. Mesophication, a hypothesized process initiated by intentional fire exclusion by which these encroaching...

Intensively managed poplar plantations (Populus spp. and their hybrids) have the potential to provide large quantities of renewable biomass for bioenergy. Identifying clonal varieties that are productive on water-limited, marginal agricultural land unsuitable for food production with low land costs is key to realizing that potential. Carbon isotope...

Research Highlights: Bottomland hardwood forests exhibit seasonal flooding, are species diverse, and provide numerous ecosystem services including floodwater storage, wildlife habitat and nutrient mitigation. However, data are needed to adequately predict the potential of individual species to achieve these services. Background and Objectives: In b...

Afforestation and reforestation of once dominant bottomland hardwood forests in the southeastern United States can provide ecosystem services and wildlife habitat. However, challenges of prior site conditions, seasonal flooding, soil texture and lack of nearby seed sources can necessitate planting of seedlings to achieve desirable results, particul...

Research Highlights: Bottomland oaks receive less attention than upland species, however their adaptations to flooding and summer water stress will extend our understanding of the oak genus and links between physiology and leaf anatomy. Background and objectives: Determining links between leaf anatomy and physiology can aid in parameterizing dynami...

Key message Increasing water use patterns were more spatially restricted than increased nitrogen in leaves and litterfall in mid-canopy sweetgum trees of varying proximity to overstory pines undergoing mortality. Abstract Ecosystem changes following selective mortality of individual trees can be difficult to predict and depend on the response of s...

The southeastern United States contains extensive loblolly pine (Pinus taeda L.) plantations at risk from bark beetle damage that can change ecosystem biogeochemical cycling. Functional changes in tree physiology have the potential to occur before visual evidence of mortality making them difficult to incorporate into ecosystem models. Therefore, we...

Chinese tallow has invaded and spread at landscape level in the southeastern United States for decades, which has threatened the habitat of native plant species, such as longleaf-slash pine and savannah. The local ecosystems are fire (wild and prescribed) dependent systems, but the fire could also affect the invasive pattern of Chinese tallow. Ther...

Understanding processes underlying forest carbon dynamics is essential for accurately predicting the outcomes of non-stand-replacing disturbance in intermediate-age forests. We quantified net ecosystem production (NEP), aboveground net primary production (ANPP), and the dynamics of major carbon (C) pools before and during the decade following invas...

Hurricane Katrina caused large losses of bottomland hardwood forests on the Gulf Coastal Plain. Heavy-seeded species such as oaks (Quercus) generally require direct planting for restoration after such losses. However, evaluating the performance of various oak planting stocks using biometric data alone can be challenging due to their slow juvenile g...

A comparative analysis of the impacts of prescribed fire on three upland forest stands in the Northeastern Atlantic Plain, NJ, USA, was conducted. Effects of prescribed fire on water use and gas exchange of overstory pines were estimated via sap-flux rates and photosynthetic measurements on Pinus rigida Mill. Each study site had two sap-flux plots,...

Palms (Arecaceae) represent one of the oldest surviving monocot families maintaining a presence in tropical rainforest-like biomes throughout history. Comprising a variety of plant growth forms (arborescent, acaulescent, lianoid), palms are one of the few monocots that achieve significant heights. In doing so, they face many of the same environment...

Pine-oak ecosystems are globally distributed even though differences in anatomy and leaf habit between many co-occurring oaks and pines suggest different strategies for resource use, efficiency and stomatal behavior. The New Jersey Pinelands contain sandy soils with low water-and nutrient-holding capacity providing an opportunity to examine trade-o...

Hydrologic variability during 2005–2011 was observed and analyzed at an upland oak/pine forest in the New Jersey Pinelands. The forest experienced defoliation by Gypsy moth (Lymantria dispar L.) in 2007, drought conditions in 2006 and a more severe drought in 2010. By using sap flux and eddy covariance measurements, stream discharge data from USGS,...

We used eddy covariance and meteorological measurements to estimate net ecosystem exchange of CO2 (NEE), gross ecosystem production (GEP), evapotranspiration (Et), and ecosystem water use efficiency (WUEe; calculated as GEP / Et during dry canopy conditions) in three upland forests in the New Jersey Pinelands, USA, that were defoliated by gypsy mot...

Carbon and water cycling of forests contribute significantly to the Earth’s overall biogeochemical cycling and may be affected by disturbance and climate change. As a larger body of research becomes available about leaf-level, ecosystem and regional scale effects of disturbances on forest ecosystems, a more mechanistic understanding is developing w...

We used eddy covariance and meteorological measurements to estimate net ecosystem exchange of CO2 (NEEc), gross ecosystem production (GEP), evapotranspiration (Et), and ecosystem water use efficiency (WUEe) in three upland forests in the New Jersey Pinelands that were defoliated by Gypsy moth (Lymantria dispar L.) or burned using prescribed fire. B...

Although snags and coarse woody debris are a small component of ecosystem respiration, disturbances can significantly increase the mass and respiration from these carbon (C) pools. The objectives of this study were to 1) measure respiration rates of snags and coarse woody debris throughout the year in a forest previously defoliated by gypsy moths,...

Oak species are well suited to water-limited conditions by either avoiding water stress through deep rooting or tolerating water stress through tight stomatal control. In co-occurring species where resources are limited, species may either partition resources in space and/or time or exhibit differing efficiencies in the use of limited resources. Th...

Correlation analyses were carried out for the dynamics of leaf water potential in two broad-leaf deciduous tree species in a sandy site under a range of air vapor pressure deficits and a relatively dry range of soil conditions. During nights when the soil is dry, the diffuse-porous, isohydric and shallow-rooted Acer rubrum does not recharge its xyl...

Background/Question/Methods We investigated the hydrologic balance of an upland oak/pine forest on the Atlantic Coastal Plain. During 2005-2011, sap flux measurements were used to quantify transpiration and eddy covariance measurements were used to estimate evapotranspiration. The forest experienced a defoliation by Gypsy moth (Lymantria dispar L...

Although wildfires are important in many forested ecosystems, increasing suburbanization necessitates management with prescribed fires. The physiological responses of overstory trees to prescribed fire has received little study and may differ from typical wildfires due to the lower intensity and timing of prescribed fire in the dormant season. Tree...

The value of urban green space has become an increasingly controversial issue. In particular, development of novel vegetative assemblages on vacant lands may have many formerly unrecognized benefits. However, questions remain regarding the functional impairment of these assemblages due to degraded soils. We investigated the effects of elevated conc...

In this response, we address the criticisms put forth by Tomlinson and Quinn (American Journal of Botany 100: 461-464) about our original publication on secondary stem lengthening in Iriartea deltoidea palms (American Journal of Botany 99: 607-613) and find areas on which we may agree. We address our figure of a typical palm vascular bundle; the lo...

Palms are an important component of tropical ecosystems, living alongside dicotyledonous trees, even though they have a very different growth pattern and vascular system. As monocots, vessels in palms are located within vascular bundles and, without a vascular cambium that many dicotyledonous trees possess, palms cannot add additional vessels to th...

We used eddy covariance and meteorological measurements to quantify energy exchange and evapotranspiration (Et) in three representative upland forest stands in the New Jersey Pinelands that were either defoliated by gypsy moth (Lymantria dispar L.) or burned in prescribed fires during the study period. Latent (λE) and sensible heat (H) fluxes were...

Background/Question/Methods: Wildfires are an important ecological component of the New Jersey Pine Barrens with its sandy, excessively well-drained soils. However, increasing encroachment by human development has made it necessary to manage these systems using early-spring prescribed burns. Spring prescribed burns, while occurring during the natur...

Sap flow measurements have become integral in many physiological and ecological investigations. A number of methods are used to estimate sap flow rates in trees, but probably the most popular is the thermal dissipation (TD) method because of its affordability, relatively low power consumption, and ease of use. However, there have been questions abo...

Premise of the study: Although traditionally assumed that all height growth in trees occurs at apical meristems, sequential measurement of internode lengths in the palm Iriartea deltoidea suggested that stems were lengthening long after the differentiation of tissues and far below the apical meristem. This observation is difficult to reconcile wit...

Background/Question/Methods Sap flow measurements have become integral in many physiological and ecological investigations. There are a number of methods described to estimate sap flow rates in trees, but probably the most popular is the Granier thermal dissipation method because of its affordability and ease of use. However, there have been ques...

Because palms grow in highly varying climates and reach considerable heights, they present a unique opportunity to evaluate how environment and plant size impact hydraulic function. We studied hydraulic properties of petioles from palms of varying height from three species: Iriartea deltoidea, a tropical rainforest species; Mauritia flexuosa, a tro...

Unlabelled: Premise of the study: This study seeks to determine how hydraulic factors vary with ontogeny and whether they begin to limit further height growth in palms. Palms are an attractive group for physiological research because their columnar trunks and simple leaf habit allow key intrinsic and extrinsic hydraulic variables to be estimated...

The wet and dry seasons in tropical rain forests can differ in precipitation, soil moisture and irradiance more significantly than often assumed. This could potentially affect the water relations of many tree species that may exhibit either increased transpiration in the dry season as a response to the increased irradiance or decreased transpiratio...

As trees grow taller, the energetic cost of moving water to the leaves becomes higher and could begin to limit carbon gain and subsequent growth. The hydraulic limitation hypothesis states that as trees grow taller, the path length and therefore frictional resistance of water flow increases, leading to stomatal closure, reduced photosynthesis and d...

Background/Question/Methods As trees grow taller, the path length for water flow increases and could begin to limit stomatal conductance, subsequent carbon gain and further height growth. This study seeks to determine how hydraulic properties of fronds from Washingtonia robusta palms change along a height gradient. Fronds were measured from palms...

We compared hydraulic architecture, photosynthesis and growth in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), a shade-intolerant species, and western hemlock (Tsuga heterophylla (Raf.) Sarg.), a shade-tolerant species, to study the temporal pattern of release from suppressive shade. In particular, we sought to determine whether hydraulic arc...

Little is known of wood properties in trees that were initially suppressed and subsequently released from suppression. The purpose of this study was to assess differences in growth ring width, specific conductivity (Ks), tracheid dimensions, moisture content, and wood density in suppressed Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and west...

The width of earlywood and latewood in conifer xylem may have a profound effect on water transport and storage, vulnerability to embolism, and wood strength, yet the controls over the timing of latewood formation are unclear. Tracheids differentiating in the cambial zone are influenced by IAA indole-3 acetic acid, the radial concentration gradient...