No detectable aerobic methane efflux from plant material, nor from adsorption/desorption processes

In early 2006, Keppler et al. (Nature, 439:187–191) reported a novel finding that plant leaves, and even simple organic materials, can release methane under aerobic conditions. We investigated here whether the reported methane release might simply arise from methane desorption from sample surfaces after prior exposure to higher methane concentrations. We exposed standard cellulose filter papers (i.e. organic material with a high surface area) to atmospheric methane concentration and then transferred them to a low-methane atmosphere. Our results suggest that any desorption flux was extremely small (−0.0001±0.0019 ngCH<sub>4</sub> kgDW<sup>−1</sup> s<sup>−1</sup>) and would play no quantitatively significant role in modifying any measured methane fluxes. <br> <br> We also incubated fresh detached leaves of several species and intact <i>Zea mays</i> seedlings under aerobic and low-light conditions. After correcting for a small measured methane influx into empty chambers, measured rates of methane emission by plant materials were zero or, at most, very small, ranging from −0.25±1.1 ngCH<sub>4</sub> kgDW<sup>−1</sup> s<sup>−1</sup> for <i>Zea mays</i> seedlings to 0.10±0.08 ngCH<sub>4</sub> kgDW<sup>−1</sup> s<sup>−1</sup> for a mixture of freshly detached grasses. These rates were much smaller than the rates originally reported by Keppler et al. (2006)

Development of an environmental effects and tourist flow data management system

There is increasing concern about the environmental sustainability of tourism based on natural attractions. We have developed a preliminary computer-based data management system that integrates information about tourists and their use of natural assets with information about how indicators of asset health respond to increasing visitor numbers. First, we collected data on tourist flows between demand (natural attractions) and supply (visitor nodes) sites for the West Coast of New Zealand. Second, we studied a variety of natural asset types in an attempt to develop models describing relationships between visitor numbers and impacts from these visits. These data were then combined to produce the environmental effects and tourism flows data management system for the West Coast. We modelled tourist flows to a range of assets, including the Franz Josef and Fox glaciers, Lake Matheson, the Okarito white heron colony, Pancake Rocks, the Cape Foulwind seal colony and a range of caves in the Buller area. Some assets, e.g., the white heron colony, are already nearing biophysical capacity, while others are not, e.g., the glaciers.This research was funded by the Foundation for Research, Science and Technology under contract LINX0007

Pondering the propulsion of peaches in Provence

International audienc

The effects of long-term, partial shading on growth and photosynthesis in Pinus radiata D. Don trees

Two 8-year-old Pinus radiata trees growing in a dry-land plantation forest were subjected to a partial shading treatment for 2 years in order to investigate the responses of photosynthesis and tree growth to a long-term reduction in illuminated leaf area. The lower 60% of the crown of shaded trees was surrounded by 50% neutral density shade cloth. This reduced radiation absorption by 13% for the trees as a whole compared to the control trees during the first year, while modelled annual whole-canopy photosynthesis was 9% lower, and was strongly regulated by seasonal soil water availability, temperature and irradiance. The shaded trees responded by increasing carbon partitioning to the branches, at the expense of the stem, As a result, basal area growth of the shaded trees was almost 50% lower than that for control trees. In the second year, the effects of the shade cloth on absorbed radiation, photosynthesis and growth were reduced. This occurred because of needle abscission below the shade cloth and rapid branch and leaf area growth above the shade cloth, while the lower foliage on the control trees became increasingly self-shaded. Allocation to stem growth increased in the shaded trees, resulting in similar relative basal area increment between shaded and control trees. The difference in modelled whole- canopy photosynthesis was smaller in the second year. This was partly due to the reduced effect of the shade cloth, but also to a significant summer drought, which severely reduced stomatal conductance, photosynthesis and stem growth in both shaded and control trees. Seasonal root-zone water deficits at this site reduce annual carbon assimilation by around 40%, and increase the proportions of carbon assimilation occurring in spring, autumn and winter. (C) 2002 Elsevier Science B.V. All rights reserved

Energy use associated with tourism in New Zealand

Energy consumption and concomitant greenhouse gas emissions are seen as a major threat to sustainability within the tourism sector. In countries such as New Zealand, where tourism is an expanding sector, it is important to determine tourism's contribution to the national 'energy bill' and to identify potential areas for improvement

Modeling photosynthesis in olive leaves under drought conditions

We quantified parameters for a model of leaf-level photosynthesis for olive, and tested the model against an independent dataset. Specific temperature-dependence parameters of the model for olive leaves were measured, as well as the relationship of the model parameters with area-based leaf nitrogen (N) content. The effect of soil water deficit on leaf photosynthesis was examined by applying two irrigation treatments to 29-year-old trees growing in a plantation: drip irrigation sufficient to meet the crop water requirements (I) and dry-farming (D). In both treatments, leaves had a higher photosynthetic capacity in April than in August. In August, photosynthetic capacity was lower in D trees than in I trees. Leaf photosynthetic capacity was linearly and positively related to leaf N content on an area basis (Na) and to leaf mass per unit area (LMA), and the regression slope varied with irrigation treatment. The seasonal reduction in Na was used in the model to predict photosynthesis under drought conditions. Olive leaves showed a clear limitation of photosynthesis by triose phosphate utilization (TPU) even at 40°C, and the data suggest that olive invests fewer resources in TPU than other species. The seasonal decrease in photosynthetic capacity moderated the stomatal limitation to carbon dioxide (CO2) fixation as soil water deficit increased. Further, it enabled leaves to operate close to the transition point between photosynthetic limitation due to RuBP carboxylation capacity and that due to RuBP regeneration capacity, and resulted in a near constant value of internal CO2 concentration from April to August. Under well watered conditions, N-use efficiency of the olive leaves was enhanced at the expense of reduced water-use efficiency.Financial support was provided by Spanish CICYT, Project HID96-342- CO4-01, and an MEC fellowship to Antonio Díaz-Espejo.Peer Reviewe

Effects of crown development on leaf irradiance, leaf morphology and photosynthetic capacity in a peach tree

absen

Effects of crown development on leaf irradiance, leaf morphology and photosynthetic capacity in a peach tree

absen

The effects of long-term, partial shading on growth and photosynthesis in Pinus radiata D. Don trees

Two 8-year-old Pinus radiata trees growing in a dry-land plantation forest were subjected to a partial shading treatment for 2 years in order to investigate the responses of photosynthesis and tree growth to a long-term reduction in illuminated leaf area. The lower 60% of the crown of shaded trees was surrounded by 50% neutral density shade cloth. This reduced radiation absorption by 13% for the trees as a whole compared to the control trees during the first year, while modelled annual whole-canopy photosynthesis was 9% lower, and was strongly regulated by seasonal soil water availability, temperature and irradiance. The shaded trees responded by increasing carbon partitioning to the branches, at the expense of the stem, As a result, basal area growth of the shaded trees was almost 50% lower than that for control trees. In the second year, the effects of the shade cloth on absorbed radiation, photosynthesis and growth were reduced. This occurred because of needle abscission below the shade cloth and rapid branch and leaf area growth above the shade cloth, while the lower foliage on the control trees became increasingly self-shaded. Allocation to stem growth increased in the shaded trees, resulting in similar relative basal area increment between shaded and control trees. The difference in modelled whole- canopy photosynthesis was smaller in the second year. This was partly due to the reduced effect of the shade cloth, but also to a significant summer drought, which severely reduced stomatal conductance, photosynthesis and stem growth in both shaded and control trees. Seasonal root-zone water deficits at this site reduce annual carbon assimilation by around 40%, and increase the proportions of carbon assimilation occurring in spring, autumn and winter. (C) 2002 Elsevier Science B.V. All rights reserved