Adaptation of stomatal conductance, photosynthesis and water-use efficiency at shoot and canopy scales in adjacent stands of Dacrycarpus dacrydioides and Podocarpus totara.

We tested an approach to estimate daily canopy net photosynthesis, A, based on estimates of transpiration, E, using measurements of sap flow and water-use efficiency, ω, by measuring δ13C in CO2 respired from shoots in the canopies of two conifers (Podocarpaceae) native to New Zealand. The trees were planted in adjacent 20-year-old stands with the same soil and environmental conditions. Leaf area index was lower for Dacrycarpus dacrydioides D.

Soil microbial sensitivity to temperature remains unchanged despite community compositional shifts along geothermal gradients.

Climate warming may be exacerbated if rising temperatures stimulate losses of soil carbon to the atmosphere. The direction and magnitude of this carbon-climate feedback are uncertain, largely due to lack of knowledge of the thermal adaptation of the physiology and composition of soil microbial communities. Here, we applied the macromolecular rate theory (MMRT) to describe the temperature response of the microbial decomposition of soil organic matter (SOM) in a natural long-term warming experiment in a geothermally active area in New Zealand.

Temperature sensitivity of decomposition decreases with increasing soil organic matter stability.

Evaluation of the temperature sensitivity of soil organic matter (SOM) decomposition is critical for forecasting whether soils in a warming world will lose or gain carbon and, therefore, accelerate or mitigate climate warming. It is usually described, using Arrhenius kinetics, as increasing with the stability of the substrate in laboratory conditions, where substrate availability is non-limiting and where chemical recalcitrance, therefore, predominantly regulates stability. However, conditions of non-limiting subtrate availability are rare in the undisturbed soil, where physicochemical protection of substrates may control their stability.

Irrigation increases forage production of newly established lucerne but enhances net ecosystem carbon losses.

In New Zealand, dairy farming faces increasing scrutiny for its environmental impacts, including those on soil carbon (C) stocks; hence, alternative management practices are required. One such practice is usage of deep-rooting forage, such as lucerne (Medicago sativa L.).

Nitrous Oxide Fluxes, Soil Oxygen, and Denitrification Potential of Urine- and Non-Urine-Treated Soil under Different Irrigation Frequencies.

Despite increased use of irrigation to improve forage quality and quantity for grazing cattle ( Linnaeus), there is a lack of data that assess how irrigation practices influence nitrous oxide (NO) emissions from urine-affected soils. Irrigation effects on soil oxygen (O) availability, a primary controller of NO fluxes, is poorly understood. It was hypothesized that increased irrigation frequency would result in lower NO emissions by increasing soil moisture and decreasing soil O concentrations.

Effects of soil warming and nitrogen addition on soil respiration in a New Zealand tussock grassland.

Soil respiration (RS) represents a large terrestrial source of CO2 to the atmosphere. Global change drivers such as climate warming and nitrogen deposition are expected to alter the terrestrial carbon cycle with likely consequences for RS and its components, autotrophic (RA) and heterotrophic respiration (RH). Here we investigate the impacts of a 3°C soil warming treatment and a 50 kg ha(-1) y(-1) nitrogen addition treatment on RS, RH and their respective seasonal temperature responses in an experimental tussock grassland.

Roots affect the response of heterotrophic soil respiration to temperature in tussock grass microcosms.

Aims And Background: While the temperature response of soil respiration (R(S)) has been well studied, the partitioning of heterotrophic respiration (R(H)) by soil microbes from autotrophic respiration (R(A)) by roots, known to have distinct temperature sensitivities, has been problematic. Further complexity stems from the presence of roots affecting R(H), the rhizosphere priming effect. In this study the short-term temperature responses of R(A) and R(H) in relation to rhizosphere priming are investigated.

Rapid changes in δ¹³C of ecosystem-respired CO₂ after sunset are consistent with transient ¹³C enrichment of leaf respired CO₂.

The CO₂ respired by darkened, light-adapted, leaves is enriched in ¹³C during the first minutes, and this effect may be related to rapid changes in leaf respiratory biochemistry upon darkening. We hypothesized that this effect would be evident at the ecosystem scale. High temporal resolution measurements of the carbon isotope composition of ecosystem respiration were made over 28 diel periods in an abandoned temperate pasture, and were compared with leaf-level measurements at differing levels of pre-illumination.

A dynamic soil chamber system coupled with a tunable diode laser for online measurements of delta13C, delta18O, and efflux rate of soil-respired CO2.

High frequency observations of the stable isotopic composition of CO(2) effluxes from soil have been sparse due in part to measurement challenges. We have developed an open-system method that utilizes a flow-through chamber coupled to a tunable diode laser (TDL) to quantify the rate of soil CO(2) efflux and its delta(13)C and delta(18)O values (delta(13)C(R) and delta(18)O(R), respectively). We tested the method first in the laboratory using an artificial soil test column and then in a semi-arid woodland.

Alternate mRNA splicing in multiple human tryptase genes is predicted to regulate tetramer formation.

Tryptases are serine proteases that are thought to be uniquely and proteolytically active as tetramers. Crystallographic studies reveal that the active tetramer is a flat ring structure composed of four monomers, with their active sites arranged around a narrow central pore. This model explains why many of the preferred substrates of tryptase are short peptides; however, it does not explain how tryptase cleaves large protein substrates such as fibronectin, although a number of studies have reported in vitro mechanisms for generating active monomers that could digest larger substrates.

Spatial and temporal scaling of intercellular CO2 concentration in a temperate rain forest dominated by Dacrydium cupressinum in New Zealand.

Seven methods, including measurements of photosynthesis (A) and stomatal conductance (g(s)), carbon isotope discrimination, ecosystem CO2 and water vapour exchange using eddy covariance and the use of a multilayer canopy model and ecosystem Keeling plots, were employed to derive estimates of intercellular CO2 concentration (Ci) across a range of spatial and temporal scales in a low productivity rain forest ecosystem dominated by the conifer Dacrydium cupressinum Lamb. in New Zealand. Estimates of shoot and canopy Ci across temporal scales ranging from minutes to years were remarkably similar (range of 274-294 micromol mol(-1)).

Collection and storage of CO2 for 13C analysis: An application to separate soil CO2 efflux into root- and soil-derived components.

Soil surface CO2 efflux is comprised of CO2 from (i) root respiration and rhizosphere microbes and (ii) heterotrophic respiration from the breakdown of soil organic matter (SOM). This efflux may be partitioned between these sources using delta13C measurements. To achieve this, continuous flow isotope ratio mass spectrometry can be used and, in conjunction with 10 mL septum-capped vials, large numbers of samples may be analysed using a Finnigan MAT Delta(plus)XP interfaced to a Gas Bench II.

Effects of cigarette smoke on degranulation and NO production by mast cells and epithelial cells.

Exhaled nitric oxide (eNO) is decreased by cigarette smoking. The hypothesis that oxides of nitrogen (NOX) in cigarette smoke solution (CSS) may exert a negative feedback mechanism upon NO release from epithelial (AEC, A549, and NHTBE) and basophilic cells (RBL-2H3) was tested in vitro. CSS inhibited both NO production and degranulation (measured as release of beta-hexosaminidase) in a dose-dependent manner from RBL-2H3 cells.

IL-15 induces mast cell migration via a pertussis toxin-sensitive receptor.

IL-15 induces proliferation, inhibits apoptosis and increases IL-4 production in murine mast cells. There is evidence that these activities are mediated via the uncharacterised receptor, IL-15R-X, rather than the classical three-chain IL-15 receptor. Effects of IL-15 on important aspects of mast cell biology, such as migration and degranulation, are unknown.

Photosynthesis and reflectance indices for rainforest species in ecosystems undergoing progression and retrogression along a soil fertility chronosequence in New Zealand.

Measurements of photosynthesis at saturating irradiance and CO2 partial pressure, Amax, "adjusted" normalised difference vegetation index, RaNDVI, and photochemical reflectance index, RPRI, were made on trees sampled along a soil chronosequence to investigate the relationship between carbon uptake and ecosystem development in relation to nutrient availability. Measurements were made on the three most dominant species at six sites along the sequence in South Westland, New Zealand with soil age ranging from < 6 to 120,000 years resulting from the retreat of the Franz Josef glacier. The decrease in soil phosphorus availability with increasing soil age and high soil nitrogen availability at the two youngest sites, due to the presence of a nitrogen-fixing species, provided marked differences in nutrient availability.

Variation in the degree of coupling between delta13C of phloem sap and ecosystem respiration in two mature Nothofagus forests.

Day-to-day variability in the carbon isotope composition of phloem sap (delta13Chd) and ecosystem respiratory CO2 (delta13CR) were measured to assess the tightness of coupling between canopy photosynthesis (delta13Chd) and ecosystem respiration (delta13CR) in two mature Nothofagus solandri (Hook. f.) forests in New Zealand.

Mast cell accumulation and cytokine expression in the tight skin mouse model of scleroderma.

The tight skin (Tsk) mouse develops many pathological changes seen in human scleroderma, such as increased collagen content and mast cell density. Although associations between mast cell expansion and skin fibrosis have been reported, the mechanisms underlying mast cell accumulation remain unclear. In this study, we have measured the density of skin mast cells in Tsk mice and their normal littermates (pa/pa) of 4-36 weeks of age, and in the skin heterografted between Tsk and pa/pa mice.

Involvement of chymase-mediated angiotensin II generation in blood pressure regulation.

Angiotensin I-converting enzyme (ACE) inhibitors are thought to lower blood pressure in hypertensive patients, mainly by decreasing angiotensin II (Ang II) formation. Chymase, a human mast cell protease, has recently been proposed to play a role in blood pressure regulation because of its Ang II-forming activity. Here we show that the predominant chymase mRNA species in the mouse aorta are those for types 4 and 5 isoforms, and that both are efficient Ang II-forming enzymes.

Delta tryptase is expressed in multiple human tissues, and a recombinant form has proteolytic activity.

Tryptases are neutral serine proteases selectively expressed in mast cells and have been implicated in the development of a number of inflammatory diseases including asthma. It has recently been established that the number of genes encoding human mast cell tryptases is much larger than originally believed, but it is not clear how many of these genes are expressed. A recent report suggested that the transcript for at least one of these genes, originally named mMCP-7-like tryptase, is not expressed.