Abstract: Reduced-impact logging (RIL) has many demonstrated benefits to the industrial logging operations for which they were developed. It is less clear whether these gains remain consistent in smallholder forest systems that increasingly play an important role in global conservation and that target a broader suite of outputs in their management schemes. We evaluate potential ecological consequences of five RIL components (pre-harvest inventories, harvest intensity, cutting cycles, skid trail planning, and liana cutting) when applied to small-scale operations in the Brazilian Amazon and provide suggestions for modifications to RIL guidelines for smallholder systems. Rapid assessment inventories of the entire landholding should be a part of crop tree selection to minimize inbreeding and recruitment failure. Additionally, while community-based taxonomists accurately identify species to common names, botanical samples must be verified with herbarium specimens to avoid market and ecological problems when multiple species share a single common name. We advocate that smallholder managers move beyond an emphasis on RIL guidelines, while still incorporating its basic tenets into practical application. Based on our analysis, this would include evaluating benefits of particular RIL components and assessing potential advantages that smallholders have over industrial operations. We suggest incorporating anthropogenically-generated forest patches of varying sizes and successional stages into a more formalized management system, incorporating and expanding on traditional ecological knowledge acquired over generations, and integrating enrichment plantings and tending of regeneration. (c) 2006 Published by Elsevier B.V.

Abstract: A study of total Hg concentration in the foliage of the canopy was carried out in two remote areas in French Guiana. The sampled canopy is representative of the French Guiana canopy. The concentration in the foliage, 64+/-14 ng g(-1) (dry wt.), is used to estimate the annual input of total Hg to the soil through the litterfall, found to be 45+/-10 mug m(-2) y(-1). As translocation is negligible, mercury in the canopy originates mainly from atmospheric uptake by the leaves and this litterfall deposit represents a direct atmospheric input from the background atmospheric load into the soil. (C) 2003 Elsevier Science B.V. All rights reserved.

Abstract: Comparisons were made among Douglas-fir forest, aspen (broad leaf deciduous) forest and wheatgrass (C-3) grassland for ecosystem-level water-use efficiency (WUE). WUE was defined as the ratio of photosynthetic CO2 assimilation rate and evapotranspiration (ET) rate. The ET data measured by eddy covariance were screened so that they overwhelmingly represented transpiration. The three sites used in this comparison spanned a range of vegetation (plant functional) types and environmental conditions within western Canada. When compared in the relative order Douglas-fir (located on Vancouver Island, BC), aspen (northern Saskatchewan), grassland (southern Alberta), the sites demonstrated a progressive decline in precipitation and a general increase in maximum air temperature and atmospheric saturation deficit (D-max) during the mid-summer. The average (+/- SD) WUE at the grassland site was 2.6 +/- 0.7 mmol mol(-1), which was much lower than the average values observed for the two other sites (aspen: 5.4 +/- 2.3, Douglas-fir: 8.1 +/- 2.4). The differences in WUE among sites were primarily because of variation in ET. The highest maximum ET rates were approximately 5, 3.2 and 2.7 mm day(-1) for the grassland, aspen and Douglas-fir sites, respectively. There was a strong negative correlation between WUE and D-max for all sites. We also made seasonal measurements of the carbon isotope ratio of ecosystem respired CO2 (delta(R)) in order to test for the expected correlation between shifts in environmental conditions and changes to the ecosystem-integrated ratio of leaf intercellular to ambient CO2 concentration (c(i)/c(a)). There was a consistent increase in delta(R) values in the grassland, aspen forest and Douglas-fir forest associated with a seasonal reduction in soil moisture. Comparisons were made between WUE measured using eddy covariance with that calculated based on D and delta(R) measurements. There was excellent agreement between WUE values calculated using the two techniques. Our delta(R) measurements indicated that c(i)/c(a) values were quite similar among the Douglas-fir, aspen and grassland sites, despite large variation in environmental conditions among sites. This implied that the shorter-lived grass species had relatively high c(i)/c(a) values for the D of their habitat. By contrast, the longer-lived Douglas-fir trees were more conservative in water-use with lower c(i)/c(a) values relative to their habitat D. This illustrates the interaction between biological and environmental characteristics influencing ecosystem-level WUE. The strong correlation we observed between the two independent measurements of WUE, indicates that the stable isotope composition of respired CO2 is a useful ecosystem-scale tool to help study constraints to photosynthesis and acclimation of ecosystems to environmental stress.

Abstract: Question: To establish a habitat classification based on functional group co-occurrence that may help the drawing up of conservation plans. Location: Riverine forest fragments in the Grand-duche de Luxembourg, Europe. Methods: Forest fragments were surveyed for their abundance of vascular plants. These were clustered into emergent groups according to 14 life-traits related to plant dispersal, establishment and persistence. Forest fragments were classified according to similar distribution of the identified emergent groups. Environmental factors were related to the emergent group richness in each forest type using generalized linear models. Results: Contrary to former species centred classifications, only two groups of forests, each with clearly different emergent group composition and conservation requirements, were detected: (1) swamp forests characterized by anemogamous perennials, annuals and hydrochorous perennials and (2) moist forests characterized by barochorous perennials, small geophytes and zoochorous phanerophytes. From a conservation point of view, priority should be given to large swamp forest with intact flooding regimes. This is in accordance with the high wind and water dispersal capacities of their typical emergent groups. For the moist forests, conservation priorities should be high forest connectivity and historical continuity since dispersal and establishment of their characteristic emergent groups are highly limited. Conclusions: The described methodology, situated at an intermediate integration level between the individual species and whole community descriptors, takes advantage of both conservation plans built for single species and the synthetic power of broad ecological measures.

Abstract: It is well known that trees adapt their supportive tissues to changes in loading conditions, yet little is known about how the vascular anatomy is modified in this process. We investigated this by comparing more and less mechanically loaded sections in six species of tropical trees with two different rooting morphologies. We measured the strain, vessel size, frequency and area fraction and from this calculated the specific conductivity, then measured the conductivity, modulus of elasticity and yield stress. The smallest vessels and the lowest vessel frequency were found in the parts of the trees subjected to the greatest stresses or strains. The specific conductivity varied up to two orders of magnitude between mechanically loaded and mechanically unimportant parts of the root system. A trade-off between conductivity and stiffness or strength was revealed, which suggests that anatomical alterations occur in response to mechanical strain. By contrast, between-tree comparisons showed that average anatomical features for the whole tree seemed more closely related to their ecological strategy.