Extramatrical mycelial biomass is mediated by fine root mass and ectomycorrhizal fungal community composition across tree species.

In many ecosystems, a large fraction of gross primary production is invested in mycorrhiza. Ectomycorrhizal (ECM) mycelium is involved in regulating soil carbon and nutrient cycling. However, little is known about how mycelial biomass, production and turnover differ depending on ECM fungal community composition and associated tree species.

The response of coarse root biomass to long-term CO enrichment and nitrogen application in a maturing Pinus taeda stand with a large broadleaved component.

Elevated atmospheric CO (eCO ) typically increases aboveground growth in both growth chamber and free-air carbon enrichment (FACE) studies. Here we report on the impacts of eCO and nitrogen amendment on coarse root biomass and net primary productivity (NPP) at the Duke FACE study, where half of the eight plots in a 30-year-old loblolly pine (Pinus taeda, L.) plantation, including competing naturally regenerated broadleaved species, were subjected to eCO (ambient, aCO plus 200 ppm) for 15-17 years, combined with annual nitrogen amendments (11.

Biomass increases attributed to both faster tree growth and altered allometric relationships under long-term carbon dioxide enrichment at a temperate forest.

Increases in atmospheric carbon dioxide (CO ) concentrations are expected to lead to increases in the rate of tree biomass accumulation, at least temporarily. On the one hand, trees may simply grow faster under higher CO concentrations, preserving the allometric relations that prevailed under lower CO concentrations. Alternatively, the allometric relations themselves may change.

Mechanisms for minimizing height-related stomatal conductance declines in tall vines.

The ability to transport water through tall stems hydraulically limits stomatal conductance (g ), thereby constraining photosynthesis and growth. However, some plants are able to minimize this height-related decrease in g , regardless of path length. We hypothesized that kudzu (Pueraria lobata) prevents strong declines in g with height through appreciable structural and hydraulic compensative alterations.

Anatomical changes with needle length are correlated with leaf structural and physiological traits across five Pinus species.

The genus Pinus has wide geographical range and includes species that are the most economically valued among forest trees worldwide. Pine needle length varies greatly among species, but the effects of needle length on anatomy, function, and coordination and trade-offs among traits are poorly understood. We examined variation in leaf morphological, anatomical, mechanical, chemical, and physiological characteristics among five southern pine species: Pinus echinata, Pinus elliottii, Pinus palustris, Pinus taeda, and Pinus virginiana.

Evapotranspiration and water yield of a pine-broadleaf forest are not altered by long-term atmospheric [CO ] enrichment under native or enhanced soil fertility.

Changes in evapotranspiration (ET) from terrestrial ecosystems affect their water yield (WY), with considerable ecological and economic consequences. Increases in surface runoff observed over the past century have been attributed to increasing atmospheric CO concentrations resulting in reduced ET by terrestrial ecosystems. Here, we evaluate the water balance of a Pinus taeda (L.

Differential responses of Picea asperata and Betula albosinensis to nitrogen supply imposed by water availability.

A pot experiment was conducted to investigate the effects of nitrogen (N) addition (0, 20, 40 g N m-2 year-1, N0, N20, N40, respectively) on the growth, and biomass accumulation and allocation of coniferous and deciduous (Picea asperata Mast. and Betula albosinensis Burk.) seedlings under a range of soil moisture limitation (40%, 50%, 60%, 80% and 100% of field capacity, FC).

Dynamics of soil CO efflux under varying atmospheric CO concentrations reveal dominance of slow processes.

We evaluated the effect on soil CO efflux (F ) of sudden changes in photosynthetic rates by altering CO concentration in plots subjected to +200 ppmv for 15 years. Five-day intervals of exposure to elevated CO (eCO ) ranging 1.0-1.

Ecophysiological variation of transpiration of pine forests: synthesis of new and published results.

Canopy transpiration (E ) is a large fraction of evapotranspiration, integrating physical and biological processes within the energy, water, and carbon cycles of forests. Quantifying E is of both scientific and practical importance, providing information relevant to questions ranging from energy partitioning to ecosystem services, such as primary productivity and water yield. We estimated E of four pine stands differing in age and growing on sandy soils.

Informing climate models with rapid chamber measurements of forest carbon uptake.

Models predicting ecosystem carbon dioxide (CO ) exchange under future climate change rely on relatively few real-world tests of their assumptions and outputs. Here, we demonstrate a rapid and cost-effective method to estimate CO exchange from intact vegetation patches under varying atmospheric CO concentrations We find that net ecosystem CO uptake (NEE) in a boreal forest rose linearly by 4.7 ± 0.

The carbon bonus of organic nitrogen enhances nitrogen use efficiency of plants.

The importance of organic nitrogen (N) for plant nutrition and productivity is increasingly being recognized. Here we show that it is not only the availability in the soil that matters, but also the effects on plant growth. The chemical form of N taken up, whether inorganic (such as nitrate) or organic (such as amino acids), may significantly influence plant shoot and root growth, and nitrogen use efficiency (NUE).

A test of the hydraulic vulnerability segmentation hypothesis in angiosperm and conifer tree species.

Water transport from soils to the atmosphere is critical for plant growth and survival. However, we have a limited understanding about many portions of the whole-tree hydraulic pathway, because the vast majority of published information is on terminal branches. Our understanding of mature tree trunk hydraulic physiology, in particular, is limited.

Stem compression reversibly reduces phloem transport in Pinus sylvestris trees.

Manipulating tree belowground carbon (C) transport enables investigation of the ecological and physiological roles of tree roots and their associated mycorrhizal fungi, as well as a range of other soil organisms and processes. Girdling remains the most reliable method for manipulating this flux and it has been used in numerous studies. However, girdling is destructive and irreversible.

How eco-evolutionary principles can guide tree breeding and tree biotechnology for enhanced productivity.

Tree breeding and biotechnology can enhance forest productivity and help alleviate the rising pressure on forests from climate change and human exploitation. While many physiological processes and genes are targeted in search of genetically improved tree productivity, an overarching principle to guide this search is missing. Here, we propose a method to identify the traits that can be modified to enhance productivity, based on the differences between trees shaped by natural selection and 'improved' trees with traits optimized for productivity.

Increases in atmospheric CO2 have little influence on transpiration of a temperate forest canopy.

Models of forest energy, water and carbon cycles assume decreased stomatal conductance with elevated atmospheric CO2 concentration ([CO2]) based on leaf-scale measurements, a response not directly translatable to canopies. Where canopy-atmosphere are well-coupled, [CO2 ]-induced structural changes, such as increasing leaf-area index (LD), may cause, or compensate for, reduced mean canopy stomatal conductance (GS), keeping transpiration (EC) and, hence, runoff unaltered. We investigated GS responses to increasing [CO2] of conifer and broadleaved trees in a temperate forest subjected to 17-yr free-air CO2 enrichment (FACE; + 200 μmol mol(-1)).

Nitrogen-addition effects on leaf traits and photosynthetic carbon gain of boreal forest understory shrubs.

Boreal coniferous forests are characterized by fairly open canopies where understory vegetation is an important component of ecosystem C and N cycling. We used an ecophysiological approach to study the effects of N additions on uptake and partitioning of C and N in two dominant understory shrubs: deciduous Vaccinium myrtillus in a Picea abies stand and evergreen Vaccinium vitis-idaea in a Pinus sylvestris stand in northern Sweden. N was added to these stands for 16 and 8 years, respectively, at rates of 0, 12.

Sustained effects of atmospheric [CO2] and nitrogen availability on forest soil CO2 efflux.

Soil CO2 efflux (Fsoil ) is the largest source of carbon from forests and reflects primary productivity as well as how carbon is allocated within forest ecosystems. Through early stages of stand development, both elevated [CO2] and availability of soil nitrogen (N; sum of mineralization, deposition, and fixation) have been shown to increase gross primary productivity, but the long-term effects of these factors on Fsoil are less clear. Expanding on previous studies at the Duke Free-Air CO2 Enrichment (FACE) site, we quantified the effects of elevated [CO2] and N fertilization on Fsoil using daily measurements from automated chambers over 10 years.

Organic nitrogen uptake of Scots pine seedlings is independent of current carbohydrate supply.

In boreal forests, seedling establishment is limited by various factors including soil nitrogen (N) availability. Seedlings may absorb N from soil in a variety of inorganic and organic forms; however, the energy and thus carbohydrate requirements for uptake and assimilation of N vary with N source. We studied the importance of current photoassimilates for the acquisition and allocation of different N sources by Scots pine (Pinus sylvestris (L.

Hydraulic limits on maximum plant transpiration and the emergence of the safety-efficiency trade-off.

Soil and plant hydraulics constrain ecosystem productivity by setting physical limits to water transport and hence carbon uptake by leaves. While more negative xylem water potentials provide a larger driving force for water transport, they also cause cavitation that limits hydraulic conductivity. An optimum balance between driving force and cavitation occurs at intermediate water potentials, thus defining the maximum transpiration rate the xylem can sustain (denoted as E(max)).

On the complementary relationship between marginal nitrogen and water-use efficiencies among Pinus taeda leaves grown under ambient and CO2-enriched environments.

Background And Aims: Water and nitrogen (N) are two limiting resources for biomass production of terrestrial vegetation. Water losses in transpiration (E) can be decreased by reducing leaf stomatal conductance (g(s)) at the expense of lowering CO(2) uptake (A), resulting in increased water-use efficiency. However, with more N available, higher allocation of N to photosynthetic proteins improves A so that N-use efficiency is reduced when g(s) declines.

Causality and persistence in ecological systems: a nonparametric spectral granger causality approach.

Abstract Directionality in coupling, defined as the linkage relating causes to their effects at a later time, can be used to explain the core dynamics of ecological systems by untangling direct and feedback relationships between the different components of the systems. Inferring causality from measured ecological variables sampled through time remains a formidable challenge further made difficult by the action of periodic drivers overlapping the natural dynamics of the system. Periodicity in the drivers can often mask the self-sustained oscillations originating from the autonomous dynamics.

Effects of stomatal delays on the economics of leaf gas exchange under intermittent light regimes.

• Understory plants are subjected to highly intermittent light availability and their leaf gas exchanges are mediated by delayed responses of stomata and leaf biochemistry to light fluctuations. In this article, the patterns in stomatal delays across biomes and plant functional types were studied and their effects on leaf carbon gains and water losses were quantified. • A database of more than 60 published datasets on stomatal responses to light fluctuations was assembled.