Projecting future N2O emissions from agricultural soils in Belgium

This study analyses the spatial and temporal variability of N₂O emissions from the agricultural soils of Belgium. Annual N₂O emission rates are estimated with two statistical models, MCROPS and MGRASS, which take account of the impact of changes in land use, climate, and nitrogen‐fertilization rate. The models are used to simulate the temporal trend of N₂O emissions between 1990 and 2050 for a 10′ latitude and longitude grid. The results are also aggregated to the regional and national scale to facilitate comparison with other studies and national inventories. Changes in climate and land use are derived from the quantitative scenarios developed by the ATEAM project based on the Intergovernmental Panel on Climate Change‐Special Report on Emissions Scenarios (IPCC‐SRES) storylines. The average N₂O flux for Belgium was estimated to be 8.6 × 10⁶ kg N₂O‐N yr⁻¹ (STD = 2.1 × 10⁶ kg N₂O‐N yr⁻¹) for the period 1990–2000. Fluxes estimated for a single year (1996) give a reasonable agreement with published results at the national and regional scales for the same year. The scenario‐based simulations of future N₂O emissions show the strong influence of land‐use change. The scenarios A1FI, B1 and B2 produce similar results between 2001 and 2050 with a national emission rate in 2050 of 11.9 × 10⁶ kg N₂O‐N yr⁻¹. The A2 scenario, however, is very sensitive to the reduction in agricultural land areas (−14% compared with the 1990 baseline), which results in a reduced emission rate in 2050 of 8.3 × 10⁶ kg N₂O‐N yr⁻¹. Neither the climatic change scenarios nor the reduction in nitrogen fertilization rate could explain these results leading to the conclusion that N₂O emissions from Belgian agricultural soils will be more markedly affected by changes in agricultural land areas.     

Regulation of Submergence-induced Enhanced Shoot Elongation in Oryza sativa L.

Rice (Oryza sativa L.) is the only cereal that can be cultivatedin the frequently flooded river deltas of South-East and SouthAsia. The survival strategies used by rice have been studiedquite extensively and the role of several phytohormones in theelongation response has been established. Deep-water rice cultivarscan diminish flooding stress by rapid elongation of their submergedtissues to keep up with the rising waters. Other rice cultivarsmay react by mechanisms of submergence tolerance. Aerenchymaand aerenchymatous adventitious roots are formed that facilitateoxygen diffusion to prevent anaerobic conditions in the submergedtissues. This paper discusses the molecular aspects of the mechanismthat leads to shoot elongation (leaves of seedlings and internodes),the regulation of which involves metabolism of, and interactionsbetween, ethylene, gibberellins and abscisic acid. Finally,the importance of new techniques in future research is assessed.Current molecular technology can reveal subtle differences ingene activity between tolerant and non-tolerant cultivars, andidentify genes that are involved in the regulation of submergenceavoidance and tolerance.     

Survival of dried eukaryotes (anhydrobiotes) after exposure to very high temperatures

Organisms that tolerate essentially complete dehydration are said to be in anhydrobiosis, and can be referred to as anhydrobiotes. Those organisms are of great ecological and medical importance, but also provide models for the study of a variety of biological phenomena. We examined the tolerance of selected eukaryotic anhydrobiotes to high temperatures using slow (∼4 °C min⁻¹) and rapid (∼100 °C min⁻¹) heating to 110, 120, 130, and 140 °C. Test organisms were then either returned to storage temperatures close to 22 °C (preheating), or held at those high temperatures for an additional 10 min. Some anhydrobiotes survived slow heating to 130 °C, whereas rapid heating led to a dramatic reduction in survival. None of these organisms encounter anywhere near these high temperatures in nature, so tolerance is not an obvious result of adaptation to current or recent conditions. We speculate that tolerance could have been achieved during the much earlier evolution of these organisms, and has been retained up to the present.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 15–22.     

Nutrient transfer between parafluvial interstitial water and river water: influence of gravel bar heterogeneity

1. Nutrient concentrations in interstitial water springs at the downstream ends of two gravel bars in the River Rhône were measured in order to estimate the importance of nutrient inputs [nitrate, dissolved organic carbon (DOC), biodegradable and refractory fractions of DOC] from the parafluvial zone (saturated sediments adjacent to the wetted channel, i.e. interstitial habitats of gravel bars) to the river as well as seasonal variations in these inputs.
2. Compared with surface water, parafluvial water had lower concentrations of DOC (especially the refractory fraction) and generally higher concentrations of nitrate. These differences were at their lowest during winter.
3. The influence of gravel bar geomorphological heterogeneity (grain size and spatial distribution of fine sediments) on parafluvial inputs was studied in terms of nutrient content and biofilm characteristics along transects across the gravel bars.
4. A gravel bar located in a stable area of the river had low transversal heterogeneity and acted as a sink for DOC and as a source of nitrate. The low fine sediment content and the high oxygenation of interstitial water must have enabled aerobic processes such as mineralization of organic matter and nitrification to occur.
5. In contrast, gravel bars located in a degradation zone of the river had a spatially variable structure, acting as a sink for DOC and nitrate because localized accumulation of fine sediment and ensuing hypoxic conditions induced anaerobic processes such as denitrification.
6. This study highlights the important influence of geomorphological heterogeneity in gravel bars for nutrient transformations as well as nutrient exchanges between parafluvial interstitial systems and the adjacent river over a seasonal cycle.     

Variability in diapause propensity within populations of a temperate insect species: interactions between insecticide resistance genes and photoperiodism

Temperate insects generally use day length as a reliable cue for long-term seasonal changes in their environment. Significant variation in photoperiodism between and within populations is thought to be associated with genetic variation resulting from local adaptation. In this study, we investigated whether genetic variation associated with selection for insecticide resistance may be a source of divergence in the photoperiodic timing of diapause through pleiotropic interactions. Critical photoperiods for diapause induction were estimated in one susceptible and two insecticide-resistant homozygous strains of the codling moth Cydia pomonella , as well as in their reciprocal F₁ progeny. Diapause responses to naturally decreasing day length were subsequently followed in the laboratory strains and in two field populations of C. pomonella in south-eastern France. We found higher critical photoperiods for diapause induction in homozygous resistant individuals than in both homozygous susceptible and heterozygous ones. This partly explained the significantly earlier timings of diapause found in homozygous resistant individuals of both laboratory and field populations of C. pomonella under natural photoperiods, relative to those found in both homozygous susceptible and heterozygous ones. We assume that adaptive genetic changes associated with selection for insecticide resistance may generate substantial variation in the seasonal timing of diapause, an essential ecological feature of the fitness of insecticide resistance genes in this species.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 83 , 341–351.     

Evaluation of the Efficacy of Florida Key Deer Translocations

Abstract: The endangered Florida Key deer (Odocoileus virginianus clavium) is endemic to the Lower Florida Keys. In recent years, habitat fragmentation and restricted dispersal have resulted in small, isolated herds on some islands. Recovery biologists proposed translocations to increase the island herds that had declined or remained low; however, efficacy of Key deer translocations had yet to be evaluated. Our objective was to evaluate survival, ranges, reproduction, and dispersal of translocated deer. During 2003–2005, we translocated 39 adult or yearling deer to Sugarloaf (approx. 19 km from trap site; 10 M, 14 F) and Cudjoe (approx. 15 km from trap site; 6 M, 9 F) keys. We kept deer in large, high-fenced holding pens (Sugarloaf = 7.7 ha, Cudjoe = 10.7 ha) on the destination islands for 3–6 months (i.e., soft release). We observed low mortality (n = 6 mortalities) of translocated deer with average annual survival (S) of 0.796 for both sexes. We found translocated deer had larger seasonal ranges than did resident deer (i.e., those located on Big Pine and No Name keys). In evaluating effects of acclimation period on ranges and dispersal, we found no difference in 95% ranges or 50% core areas ≤4 month postrelease versus 4–8 months postrelease. We found, however, postrelease dispersal distances were dependent on time kept in pen. Only 2 of 39 (5%) translocated deer left the destination islands by the end of the study. With high survival and low dispersal indicating success, we credit soft release translocation in establishing deer herds on Sugarloaf and Cudjoe keys. Our data support translocations as an effective strategy for creating sustainable outer-island Key deer herds.