Species‐specific transpiration responses to intermediate disturbance in a northern hardwood forest

Intermediate disturbances shape forest structure and composition, which may in turn alter carbon, nitrogen, and water cycling. We used a large‐scale experiment in a forest in northern lower Michigan where we prescribed an intermediate disturbance by stem girdling all canopy‐dominant early successional trees to simulate an accelerated age‐related senescence associated with natural succession. Using 3 years of eddy covariance and sap flux measurements in the disturbed area and an adjacent control plot, we analyzed disturbance‐induced changes to plot level and species‐specific transpiration and stomatal conductance. We found transpiration to be ~15% lower in disturbed plots than in unmanipulated control plots. However, species‐specific responses to changes in microclimate varied. While red oak and white pine showed increases in stomatal conductance during postdisturbance (62.5 and 132.2%, respectively), red maple reduced stomatal conductance by 36.8%. We used the hysteresis between sap flux and vapor pressure deficit to quantify diurnal hydraulic stress incurred by each species in both plots. Red oak, a ring porous anisohydric species, demonstrated the largest mean relative hysteresis, while red maple, bigtooth aspen, and paper birch, all diffuse porous species, had the lowest relative hysteresis. We employed the Penman‐Monteith model for LE to demonstrate that these species‐specific responses to disturbance are not well captured using current modeling strategies and that accounting for changes to leaf area index and plot microclimate are insufficient to fully describe the effects of disturbance on transpiration.Key PointsPlot level scaling of evaporation from sap flux evaluated with eddy fluxDisturbance changes intradaily transpiration dynamicsHydraulic strategy causes species‐specific transpiration differencesPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110637/1/jgrg20315.pd

Bench-to-bedside review : targeting antioxidants to mitochondria in sepsis

Peer reviewedPublisher PD

Active Disk Building in a local HI-Massive LIRG: The Synergy between Gas, Dust, and Star Formation

HIZOA J0836-43 is the most HI-massive (M_HI = 7.5x10^10 Msun) galaxy detected in the HIPASS volume and lies optically hidden behind the Milky Way. Markedly different from other extreme HI disks in the local universe, it is a luminous infrared galaxy (LIRG) with an actively star forming disk (>50 kpc), central to its ~ 130 kpc gas disk, with a total star formation rate (SFR) of ~20.5 Msun yr^{-1}. Spitzer spectroscopy reveals an unusual combination of powerful polycyclic aromatic hydrocarbon (PAH) emission coupled to a relatively weak warm dust continuum, suggesting photodissociation region (PDR)-dominated emission. Compared to a typical LIRG with similar total infrared luminosity (L_TIR=10^11 Lsun), the PAHs in HIZOA J0836-43 are more than twice as strong, whereas the warm dust continuum (lambda > 20micron) is best fit by a star forming galaxy with L_TIR=10^10 Lsun. Mopra CO observations suggest an extended molecular gas component (H_2 + He > 3.7x10^9 Msun) and a lower limit of ~ 64% for the gas mass fraction; this is above average compared to local disk systems, but similar to that of z~1.5 BzK galaxies (~57%). However, the star formation efficiency (SFE = L_IR/L'_CO) for HIZOA J0836-43 of 140 Lsun (K km s^{-1} pc^2)^{-1} is similar to that of local spirals and other disk galaxies at high redshift, in strong contrast to the increased SFE seen in merging and strongly interacting systems. HIZOA J0836-43 is actively forming stars and building a massive stellar disk. Its evolutionary phase of star formation (M_stellar, SFR, gas fraction) compared to more distant systems suggests that it would be considered typical at redshift z~1. This galaxy provides a rare opportunity in the nearby universe for studying (at z~0.036) how disks were building and galaxies evolving at z~1, when similarly large gas fractions were likely more common.Comment: Accepted for publication in The Astrophysical Journal. 16 pages, 8 figure

The sulfur pathway and diagnosis of sulfate depletion in grapevine

Sulfur is an essential nutrient to all plant species. Plants assimilate sulfur in a well-described pathway, which has been taken up by roots. Regulatory mech- anism has been the subject of many research papers. However, recent studies highlighted differences between crop plants and the model plant Arabidopsis thaliana. Our work focuses on the identification of genes involved in the sulfur metabolism in the Vitis vinifera genome, and their response to sulfur deficiency and other abiotic stress endured by grapevine in the field, namely water stress. Here, we describe the identification and brief characterization of the first assimilation enzymes involved in the sulfur pathway, the enzyme responsible for sulfur activa- tion, ATP sulfurylase (ATPS), and the two enzymes that reduce sulfate to sulfide, Adenosine 50-phosphosulate reductase (APR) and Sulfite reductase (SiR). A reduc- tion was observed in the number of ATPS and APR isoforms identified in V. vinifera genome when compared to A. thaliana or Glycine max genomes. Two ATPS isoforms were present in the Vitis genome, of which only ATPS1 transcript was detected in the tested tissues, and one APR isoform, suggesting an absence of redundancy in the role of both enzymes. ATPS1, APR and SiR transcript level was up-regulated in response to 2 days exposure to sulfur deficiency in V. vinifera cell cultures, which was completely reversed by the addition of GSH to the culture medium. Apparently, oxidative stress triggered GSH has a pivotal role in the regulation of ATPS1, APR and SiR transcription level, since their up-regulation was observed in mRNA from field grapevine berries under water stress, which is known to induce oxidative stress.info:eu-repo/semantics/publishedVersio

Forest Biomass Density across Large Climate Gradients in Northern South America is related to Water Availability but not with Temperature

Understanding and predicting the likely response of ecosystems to climate change are crucial challenges for ecology and for conservation biology. Nowhere is this challenge greater than in the tropics as these forests store more than half the total atmospheric carbon stock in their biomass. Biomass is determined by the balance between biomass inputs (i.e., growth) and outputs (mortality). We can expect therefore that conditions that favor high growth rates, such as abundant water supply, warmth, and nutrient-rich soils will tend to correlate with high biomass stocks. Our main objective is to describe the patterns of above ground biomass (AGB) stocks across major tropical forests across climatic gradients in Northwestern South America. We gathered data from 200 plots across the region, at elevations ranging between 0 to 3400 m. We estimated AGB based on allometric equations and values for stem density, basal area, and wood density weighted by basal area at the plot-level. We used two groups of climatic variables, namely mean annual temperature and actual evapotranspiration as surrogates of environmental energy, and annual precipitation, precipitation seasonality, and water availability as surrogates of water availability. We found that AGB is more closely related to water availability variables than to energy variables. In northwest South America, water availability influences carbon stocks principally by determining stand structure, i.e. basal area. When water deficits increase in tropical forests we can expect negative impact on biomass and hence carbon storage

Constraints on anomalous QGC's in e+e−e^{+}e^{-} interactions from 183 to 209 GeV

The acoplanar photon pairs produced in the reaction e(+) e(-) - → vvyy are analysed in the 700 pb(-1) of data collected by the ALEPH detector at centre-of-mass energies between 183 and 209 GeV. No deviation from the Standard Model predictions is seen in any of the distributions examined. The resulting 95% C.L. limits set on anomalous QGCs, a(0)(Z), a(c)(Z), a(0)(W) and a(c)(W), are -0.012 lt a(0)(Z)/Lambda(2) lt +0.019 GeV-2, -0.041 lt a(c)(Z)/Lambda(2) lt +0.044 GeV-2, -0.060 lt a(0)(W)/Lambda(2) lt +0.055 GeV-2, -0.099 lt a(c)(W)/Lambda(2) lt +0.093 GeV-2, where Lambda is the energy scale of the new physics responsible for the anomalous couplings

Observations of stem water storage in trees of opposing hydraulic strategies

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/116368/1/ecs2201569165.pd