Mortality of silver fir and Norway Spruce in the Western Alps — a semi-parametric approach combining size-dependent and growth-dependent mortality

Question

Tree mortality can be modeled using two complementary covariates, tree size and tree growth. Tree growth is an integrative measure of tree vitality while tree diameter is a good index of sensitivity to disturbances and can be considered as a proxy for tree age which may indicate senescence. Few mortality models integrate both covariates because classical model calibration requires large permanent plot data-sets which are rare. How then can we calibrate a multivariate mortality model including size and growth when permanent plots data are not available?

Location

To answer this question, we studied Abies alba and Picea abies mortality in the French Swiss and Italian Alps.

Method

Our study proposes an alternative semi-parametric method which includes a random sample of living and dead trees with diameter and growth measurements.

Results

We were able to calibrate a mortality model combining both size-dependent and growth-dependent mortality. We demonstrated that A. alba had a lower annual mortality rate (10%) than P. abies (18%) for low growth (< 0.2 mmyear^?1). We also demonstrated that for higher diameters (DBH ≥ 70 cm), P. abies had a higher mortality rate (0.45%) than A. alba (0.32%).

Conclusion

Our results are consistent with the mechanisms of colonization-competition trade-off and of successional niche theory which may explain the coexistence of these two species in the Alps. The method we developed should be useful for forecasting tree mortality and can improve the efficiency of forest dynamics models.     

Regional characterization of the long-term change in soil organic carbon under intensive agriculture

Abstract. To study the change in soil organic carbon (SOC) since it was recorded during the Belgian National Soil Survey some 40 years ago, we recently revisited 939 locations still under use as arable land. The study area comprised almost the entire province of West Flanders (about 3000 km²) characterized by profound changes in its arable land management. Taking the increased ploughing depth (by 9.8 cm on average) into account, a significant (P= 0.001) increase of the SOC content by 0.2% on average was found. Expressed as an amount, the SOC in the topsoil rose by 9.3 t/ha on average, representing an increase of 25%. This is comparable with the conversion of arable land into grassland for 2 to 3 decades. Geostatistical tools were used to map the SOC at the two times of observation. These showed that most of the spatial variation occurred within about 4 km. Since the community level is the smallest spatial resolution on which agricultural statistics are gathered officially, a detailed modelling of the change in SOC was impossible. However, by selecting communities with extreme changes in SOC, we found indications that the major source of increase in SOC was due to the large increase in pig breeding.     

Discrimination of Cognacs and other distilled drinks by mid-infrared spectropscopy

Mid-infrared spectroscopy was applied to the analysis and discrimination of Cognacs and other distilled drinks (Armagnacs, whiskies, brandies, bourbons, rums, and counterfeit products). Strong correlations were found between dry extract spectra, polyphenolic dry extract spectra, and the total polyphenol concentration of samples, notably of Cognacs. Principal component analysis applied to spectral data made it possible to emphasize the importance of dry extract data when a distinction is made between Cognacs and Armagnacs, whiskies, bourbons, and rums, and of polyphenol concentration when Cognacs, brandies, and counterfeit products are separated. Ninety-six percent of samples in the test set were correctly assigned to Cognacs and non-Cognacs by partial least-squares discriminant analysis.     

Structuring of some basic pedological processes

In the first section, the author presents a detailed analysis of fundamental processes of pedological evolution in the light of the latest findings as to biogeochemical, mineralogical and granulometric aspects of pedogenesis on crystalline aluminosilicate rocks. This analysis is based on the nature of various geochemical weathering phenomena, on the one hand, and on problems related to the organization of plasmic elements (pédoplasmation) and their possible transfers as particles, on the other. With reference to the latter aspect, two major types of “pedogenesis” may be considered: “associative” pedogenesis in which plasma-skeleton links are kept, and “dissociative” pedogenesis in which plasma—skeleton links are disrupted and plasma is redistributed.Then, in the second section, a structuring of fundamental pedogenetic processes is proposed, based on the observation of three major phyla at the earth surface.Phylum I: Process with predominant biogeochemical evolution without plasma formation or with plasma destruction.Phylum II: Process with predominant biogeochemical evolution with plasma formation and reorganization in situ.Phylum III: Process with predominant textural evolution with plasma mobilization and redistribution.     

Manipulating the N release from N labelled celery residues by using straw and vinasses

The aim of this laboratory study was to investigate the effect of straw and vinasses on the nitrogen (N) mineralization-immobilization turnover of celery residues during two periods (each simulating a time period from autumn till spring) under laboratory conditions. During the first period (1-198 d), ¹⁵N-labelled celery residues (1.1 g dry matter (DM) kg⁻¹ soil) were incubated together with straw (8.1 g DM kg⁻¹ soil), aiming to immobilize the N released from celery residues, followed by an incorporation of vinasses (1.9 g DM kg⁻¹ soil) after 84 d, with a view to remineralizing the immobilized celery-N. During the second period (198-380 d), the experimental set-up was repeated, except that non-labelled celery residues were used. Total N, mineral N and their ¹⁵N enrichments as well as microbial biomass N were determined at regular time intervals. During both periods, mixing celery residues with straw significantly increased microbial biomass N (90.5 and 40.5 mg N kg⁻¹ extra compared to celery only treatment) and decreased the amount of mineral N (reduction of 56.1 and 45.9 mg N kg⁻¹ soil compared to celery only treatment) and the celery-derived mineral ¹⁵N (0% of mineral celery-derived ¹⁵N in straw treatment compared to 35% of mineral celery-derived ¹⁵N in celery only treatment). After maximum immobilization, a natural remineralization (without addition of vinasses) of 32.2 (at day 198) and 11.1 mg N kg⁻¹ soil (at day 380) occurred in the straw treatment, but the mineral N content remained significantly lower than in the celery only treatment during the complete experiment, and the amount of remineralized celery-¹⁵N was very low (5.4% of celery-derived ¹⁵N after 380 d). Vinasses caused no real priming effect, although it did slightly increase the amount of remineralized celery-¹⁵N (+6.4% of celery-derived ¹⁵N at day 380 compared to the straw treatment), probably due an apparent added N interaction caused by displacement reactions with the soil microbial biomass.     

Root-growth response of winter barley to subsoiling

Root growth of winter barley was studied on 2 Belgian silt loam soils after subsoiling to 60 cm depth. In the first field (well-drained) rooting depth increased significantly after removal of a plough pan. At the flowering stage, total root weight in the soil layers between 25–50 cm and 50–75 cm was 125% and 325%, respectively, higher on the subsoiled plots than on the control. The P₂O₅ and K₂O concentrations in the roots were significantly increased by 20% and 40%, respectively. In the second field (imperfectly drained) with initially relatively high bulk densities in the subsoil, the influence of subsoiling was negligible. In this study, the clearly-shown root-growth retardation that resulted in a lower yield on the control, seemed to be caused by the high penetration resistance in the plough sole (> 3MPA) rather than poor aeration status induced by the high bulk densities.     

Rapid seedlings regeneration from seeds and vegetative propagation with sucker and rhizome of Eremospatha macrocarpa (Mann & Wendl.) Wendl and Laccosperma secundiflorum (P. Beauv.) Kuntze

To develop efficient seedling production methods for Laccosperma secundiflorum and Eremospatha macrocarpa, a study was conducted to examine regeneration using offsets combined with several physical and chemical treatments of seeds. Offsets categorized into small, medium and large diameters, were planted in three conditions: shaded and open nursery, and greenhouse. We tested sucker from E. macrocarpa, and sucker and rhizome from L. secundiflorum. For both species, high viability percentage (ranging from 55% to 100%) were observed for small and medium suckers planted in shaded nursery and greenhouse, against less than 49% for sucker planted in open nursery. The mean seedling emergence times were estimated to 84, 77 and 75 days after planting (DAP) for small, medium and large sucker of L. secundiflorum, respectively under open nursery condition, and 76, 75, 95 DAP for small, medium and large suckers of the same species, respectively in shaded condition. Greenhouse has a significant positive effect on E. macrocarpa seedlings emergence time. For this species, the mean seedling emergence times were estimated to 43 DAP for small sucker and 76, 93 DAP for medium and large suckers. No seedling was obtained from rhizome planted in all the growing conditions tested. Concerning seed dormancy breaking, germination percentages and rates were determined for 13 treatments. The best treatments were pre-soaking unscarified seeds for 4 days in 1.01 g l⁻¹ and 0.10 g l⁻¹ KNO₃, with 79% and 68% of germination, respectively and in 3.46 × 10⁻³ g l⁻¹ GA₃ for 68% of germination. These methods are suggested to improve germination of L. secundiflorum seeds. Successful and recommended methods for E. macrocarpa are pre-soaking scarified seeds in 3.46 × 10⁻³ g l⁻¹ and 3.46 × 10⁻⁴ g l⁻¹ GA₃, 96% and 94% of germination, respectively. Dormancy, probably a combination of mechanical and chemical dormancy, is present in the two species.     

CoRoT measures solar-like oscillations and granulation in stars hotter than the Sun

Oscillations of the Sun have been used to understand its interior structure. The extension of similar studies to more distant stars has raised many difficulties despite the strong efforts of the international community over the past decades. The CoRoT (Convection Rotation and Planetary Transits) satellite, launched in December 2006, has now measured oscillations and the stellar granulation signature in three main sequence stars that are noticeably hotter than the sun. The oscillation amplitudes are about 1.5 times as large as those in the Sun; the stellar granulation is up to three times as high. The stellar amplitudes are about 25% below the theoretic values, providing a measurement of the nonadiabaticity of the process ruling the oscillations in the outer layers of the stars.     

Mutations in a human ROBO gene disrupt hindbrain axon pathway crossing and morphogenesis

The mechanisms controlling axon guidance are of fundamental importance in understanding brain development. Growing corticospinal and somatosensory axons cross the midline in the medulla to reach their targets and thus form the basis of contralateral motor control and sensory input. The motor and sensory projections appeared uncrossed in patients with horizontal gaze palsy with progressive scoliosis (HGPPS). In patients affected with HGPPS, we identified mutations in the ROBO3 gene, which shares homology with roundabout genes important in axon guidance in developing Drosophila, zebrafish, and mouse. Like its murine homolog Rig1/Robo3, but unlike other Robo proteins, ROBO3 is required for hindbrain axon midline crossing.