Effects of Eucalyptus wood and leaf litter on saproxylic insects in the southeastern United States.

Although Eucalyptus is widely planted outside its native range for timber and pulp production, the effects of these exotic plantations on biodiversity relative to native semi-natural forests or plantations of native tree species remain incompletely understood. Here, we compare the diversity of saproxylic beetles (Coleoptera) and true bugs (Hemiptera) between non-native Eucalyptus benthamii Maiden and Cambage (Camden white gum) and native Pinus taeda L. (loblolly pine) stands on the upper Coastal Plain of South Carolina, U.

Season of drought affects growth, but not nonstructural carbohydrates dynamics, in Pinus taeda saplings.

In temperate evergreen conifers, growth occurs mostly in summer but photosynthesis precedes year-round; thus, nonstructural carbohydrates (NSC) increase in winter but decrease in summer. Given that mild drought reduces growth but not photosynthesis, a drought in summer should increase NSCs more than one in winter. However, the active regulation hypothesis suggests that to increase future drought resilience, plants might downregulate growth to increase NSCs after a winter drought even if NSCs do not increase during the drought.

Modeling starch dynamics from seasonal variations of photosynthesis, growth, and respiration.

Nonstructural carbohydrates (NSCs) buffer differences in plant carbon supply (photosynthesis) and demand (respiration, growth, etc.) but the regulation of their dynamics remains unresolved. Seasonal variations in NSCs are well-documented, but differences in the time-average, amplitude, phase, and other characteristics across ecosystems and functional types lack explanation; furthermore, observed dynamics do not always match expectations.

Development of DNA methylation-based epigenetic age predictors in loblolly pine (Pinus taeda).

Biological ageing is connected to life history variation across ecological scales and informs a basic understanding of age-related declines in organismal function. Altered DNA methylation dynamics are a conserved aspect of biological ageing and have recently been modelled to predict chronological age among vertebrate species. In addition to their utility in estimating individual age, differences between chronological and predicted ages arise due to acceleration or deceleration of epigenetic ageing, and these discrepancies are linked to disease risk and multiple life history traits.

Tree crown injury from wildland fires: causes, measurement and ecological and physiological consequences.

The dead foliage of scorched crowns is one of the most conspicuous signatures of wildland fires. Globally, crown scorch from fires in savannas, woodlands and forests causes tree stress and death across diverse taxa. The term crown scorch, however, is inconsistently and ambiguously defined in the literature, causing confusion and conflicting interpretation of results.

Xylem transport of root-derived CO caused a substantial underestimation of belowground respiration during a growing season.

Previous research has indicated that a potentially large portion of root-respired CO can move internally through tree xylem, but these reports are relatively scarce and have generally been limited to short observations. Our main objective was to provide a continuous estimate of the quantity and variability of root-respired CO that moves either internally through the xylem (F ) or externally through the soil to the atmosphere (F ) over most of a growing season. Nine trees were measured in a Populus deltoides stand for 129 days from early June to mid-October.

Integration of ecosystem science into radioecology: A consensus perspective.

In the Fall of 2016 a workshop was held which brought together over 50 scientists from the ecological and radiological fields to discuss feasibility and challenges of reintegrating ecosystem science into radioecology. There is a growing desire to incorporate attributes of ecosystem science into radiological risk assessment and radioecological research more generally, fueled by recent advances in quantification of emergent ecosystem attributes and the desire to accurately reflect impacts of radiological stressors upon ecosystem function. This paper is a synthesis of the discussions and consensus of the workshop participant's responses to three primary questions, which were: 1) How can ecosystem science support radiological risk assessment? 2) What ecosystem level endpoints potentially could be used for radiological risk assessment? and 3) What inference strategies and associated methods would be most appropriate to assess the effects of radionuclides on ecosystem structure and function? The consensus of the participants was that ecosystem science can and should support radiological risk assessment through the incorporation of quantitative metrics that reflect ecosystem functions which are sensitive to radiological contaminants.

Stand development and other intrinsic factors largely control fine-root dynamics with only subtle modifications from resource availability.

Forest productivity depends on resource acquisition by ephemeral roots and leaves. A combination of intrinsic and environmental factors influences ephemeral organs; however, difficulties in studying belowground organs impede mechanistic understanding of fine-root production and turnover. To quantify factors controlling fine-root dynamics, we grew a deciduous hardwood (Populus deltoides Bartr.

Stored root carbohydrates can maintain root respiration for extended periods.

Tight coupling between below-ground autotrophic respiration and the availability of recently assimilated carbon (C) has become a paradigm in the ecophysiological literature. Here, we show that stored carbohydrates can decouple respiration from assimilation for prolonged periods by mobilizing reserves from transport roots to absorptive roots. We permanently disrupted the below-ground transfer of recently assimilated C using stem girdling and root trenching and measured soil CO efflux for over 1 yr in longleaf pine (Pinus palustris), a species that has large reserves of stored carbohydrates in roots.

A quantitative method for analyzing glycome profiles of plant cell walls.

Glycome profiling allows for the characterization of plant cell wall ultrastructure via sequential extractions and subsequent detection of specific epitopes with a suite of glycan-specific monoclonal antibodies (mAbs). The data are often viewed as the amount of materials recovered and coinciding colored heatmaps of mAb binding are generated. Interpretation of these data can be considered qualitative in nature as it depends on detecting subtle visual differences in antibody binding strength.

Cell Wall Ultrastructure of Stem Wood, Roots, and Needles of a Conifer Varies in Response to Moisture Availability.

The composition, integrity, and architecture of the macromolecular matrix of cell walls, collectively referred to as cell wall ultrastructure, exhibits variation across species and organs and among cell types within organs. Indirect approaches have suggested that modifications to cell wall ultrastructure occur in response to abiotic stress; however, modifications have not been directly observed. Glycome profiling was used to study cell wall ultrastructure by examining variation in composition and extractability of non-cellulosic glycans in cell walls of stem wood, roots, and needles of loblolly pine saplings exposed to high and low soil moisture.

Temporal and spatial patterns of internal and external stem CO2 fluxes in a sub-Mediterranean oak.

To accurately estimate stem respiration (R), measurements of both carbon dioxide (CO) efflux to the atmosphere (E) and internal CO flux through xylem (F) are needed because xylem sap transports respired CO upward. However, reports of seasonal dynamics of F and E are scarce and no studies exist in Mediterranean species under drought stress conditions. Internal and external CO fluxes at three stem heights, together with radial stem growth, temperature, sap flow and shoot water potential, were measured in Quercus pyrenaica Willd.

Seasonal and diel variation in xylem CO2 concentration and sap pH in sub-Mediterranean oak stems.

Since a substantial portion of respired CO2 remains within the stem, diel and seasonal trends in stem CO2 concentration ([CO2]) are of major interest in plant respiration and carbon budget research. However, continuous long-term stem [CO2] studies are scarce, and generally absent in Mediterranean climates. In this study, stem [CO2] was monitored every 15min together with stem and air temperature, sap flow, and soil water storage during a growing season in 16 stems of Quercus pyrenaica to elucidate the main drivers of stem [CO2] at different temporal scales.

Global patterns and predictors of stem CO2 efflux in forest ecosystems.

Stem CO2 efflux (ES) plays an important role in the carbon balance of forest ecosystems. However, its primary controls at the global scale are poorly understood and observation-based global estimates are lacking. We synthesized data from 121 published studies across global forest ecosystems and examined the relationships between annual ES and biotic and abiotic factors at individual, biome, and global scales, and developed a global gridded estimate of annual ES .

Poplar saplings exposed to recurring temperature shifts of different amplitude exhibit differences in leaf gas exchange and growth despite equal mean temperature.

Most investigations of plant responses to changes in temperature have focused on a constant increase in mean day/night temperature without considering how differences in temperature cycles can affect physiological processes and growth. To test the effects of changes in growth temperature on foliar carbon balance and plant growth, we repeatedly exposed poplar saplings (Populus deltoides × nigra) to temperature cycles consisting of 5 days of a moderate (M, +5 °C) or extreme (E, +10 °C) increase in temperature followed by 5 days of a moderate (M, -5 °C) or extreme (E, -10 °C) decrease in temperature, with respect to a control treatment (C, 23.4 °C).

Stem girdling affects the quantity of CO2 transported in xylem as well as CO2 efflux from soil.

There is recent clear evidence that an important fraction of root-respired CO2 is transported upward in the transpiration stream in tree stems rather than fluxing to the soil. In this study, we aimed to quantify the contribution of root-respired CO2 to both soil CO2 efflux and xylem CO2 transport by manipulating the autotrophic component of belowground respiration. We compared soil CO2 efflux and the flux of root-respired CO2 transported in the transpiration stream in girdled and nongirdled 9-yr-old oak trees (Quercus robur) to assess the impact of a change in the autotrophic component of belowground respiration on both CO2 fluxes.

Internal recycling of respired CO 2 may be important for plant functioning under changing climate regimes.

Recent studies have provided evidence of a large flux of root-respired CO 2 in the transpiration stream of trees. In our study, we investigated the potential impact of this internal CO 2 transport on aboveground carbon assimilation and CO 2 efflux. To trace the transport of root-respired CO 2, we infused a (13)C label at the stem base of field-grown Populus deltoides Bartr.

Assimilation of xylem-transported CO2 is dependent on transpiration rate but is small relative to atmospheric fixation.

The effect of transpiration rate on internal assimilation of CO2 released from respiring cells has not previously been quantified. In this study, detached branches of Populus deltoides were allowed to take up (13)CO2-labelled solution at either high (high label, HL) or low (low label, LL) (13)CO2 concentrations. The uptake of the (13)CO2 label served as a proxy for the internal transport of respired CO2, whilst the transpiration rate was manipulated at the leaf level by altering the vapour pressure deficit (VPD) of the air.

Transport of root-respired CO₂ via the transpiration stream affects aboveground carbon assimilation and CO₂ efflux in trees.

Upward transport of CO₂ via the transpiration stream from belowground to aboveground tissues occurs in tree stems. Despite potentially important implications for our understanding of plant physiology, the fate of internally transported CO₂ derived from autotrophic respiratory processes remains unclear. We infused a ¹³CO₂-labeled aqueous solution into the base of 7-yr-old field-grown eastern cottonwood (Populus deltoides) trees to investigate the effect of xylem-transported CO₂ derived from the root system on aboveground carbon assimilation and CO₂ efflux.

Root-derived CO(2) efflux via xylem stream rivals soil CO(2) efflux.

Respiration consumes a large portion of annual gross primary productivity in forest ecosystems and is dominated by belowground metabolism. Here, we present evidence of a previously unaccounted for internal CO(2) flux of large magnitude from tree roots through stems. If this pattern is shown to persist over time and in other forests, it suggests that belowground respiration has been grossly underestimated.