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Purpose The impact of vermicompost on tree-soil systems is not yet fully understood. This study aimed to comparatively investigate the effects of chemical fertilizer, compost and vermicompost on soil enzymatic activities, seedling mycorrhizal colonization, growth and nutrition of one exotic tree species (radiata pine, Pinus radiata D. Don) and two native tree species (mānuka, Leptospermum scoparium and tōtara, Podocarpus totara). Methods A 12-month-long pot trial was set up in the glasshouse with a factorial design of three tree species (radiata pine, tōtara and manuka) by six treatments, including T1-control, T2-chemical fertilizer, T3-HS compost, T4-HS vermicompost, T5-LS vermicompost and T6-CM vermicompost. We assessed the main effects and interactions of treatment and species on soil chemical and biological properties, plant growth and nutritional responses. Results Compared to the untreated control (T1), application of vermicomposts (T4-T6) and compost (T3) significantly improved soil chemical properties and enzymatic activities, and increased total seedling dry weight by 160–260%, shoot concentrations of nitrogen (N) by 54–97% and phosphorus (P) by 61–91%. Vermicomposts were comparable to diammonium phosphate (DAP) applied at 133 kg N ha−1 (T2) in stimulating the growth of native species (mānuka and tōtara) without negative impact on mycorrhizal colonization, with T5 being better than DAP (T2) in promoting mānuka growth. However, application of vermicompost alone was less effective than DAP in stimulating the exotic radiata pine growth. Overall, soil activities of dehydrogenase, urease, acid phosphatase and invertase were significantly and positively correlated to total C and N and exchangeable Ca and Mg. Conclusion The increased growth of three tree species after application of vermicomposts was mainly related to improved N and P nutrition associated with enhanced root growth and soil enzymatic activities. Our findings imply that the vermicomposting products from septic tank waste could be a promising alternative to inorganic fertilizers in land application or greenhouse potting media of native tree species.

Forests provide essential ecosystem services such as wood production and soil carbon storage, which can be influenced by forest management. Fertilization and understory removal (UR) are common practices set up in managed forests to reduce tree mortality and relieve trees from their main limitations, but their effects on belowground functioning and soil carbon storage are still unclear. In this study, we investigated the effects of fertilization, UR and their interaction on the carbon stored in the ecosystem and soil enzyme activities in two different moorlands in southwestern France (dry and wet moorlands) planted with maritime pines (Pinus pinaster Ait.). Our results showed that fertilization had a positive effect on tree biomass in the wet moorland, but did not affect soil organic carbon stocks. In contrast, UR had a positive influence on tree biomass in both sites, whereas it had a strong negative effect on soil organic carbon stocks in the dry moorland only. Furthermore, we found that carbon-related enzyme activities were not affected by fertilization, but decreased with UR in the dry moorland. When looking at the carbon pools, we found that fertilization increased total carbon stocks in the wet moorland due to an increase in aboveground biomass. In contrast, UR did not affect total carbon stocks in the dry moorland due to compensatory effects with an increase of carbon stored in the aboveground biomass coupled to a decrease of carbon stored in the soil. These results highlight the importance of adapting forest practices depending on the environmental context.

An increasing number of studies demonstrate that tree species biodiversity can affect primary productivity and nutrient cycling in forests due to several factors, such as complementarity, facilitation or selection effects. For instance, resource partitioning in soils has been found to allow a more optimized nutrient uptake in mixed species plots compared with monocultures. However, how these effects will be modified by climate change – such as water availability – is not as well understood, especially in deep soil layers. Therefore, we specifically asked how water availability may influence the effect of tree mixtures on soil microorganism activity by measuring extracellular enzyme activities (EEAs) and available nutrients along the soil profile (down to 90 cm) in a 10-year-old plantation in southwestern France, which manipulates tree species composition (Pinus pinaster and Betula pendula, in monocultures and in mixed plots) and irrigation. Our results showed that EEAs directly depend on tree species composition and water conditions in interaction with soil depth; we found a positive effect of mixing birch and pine on carbon and nitrogen-related EEAs at an intermediate soil depth (15–30 cm soil layer), while the effect of increasing water availability increased phosphorus-related EEAs mostly in the upper soil layers (0–30 cm). However, we found no significant interactive effect between tree diversity and water availability on EEAs, underlying that the negative effect of lower water availability cannot be offset by the positive effect of mixing tree species. Differences in EEAs and available nutrients along the soil profile highlight the importance to look at different soil depths to better understand how nutrient cycling may be affected by increasing tree diversity and changes in water availability.

International audience; •Background and aims - Large, persistent seed banks contribute to the invasiveness of non-native plants, and maternal plant size is an important contributory factor. We explored the relationships between plant vegetative size (V) and soil seed bank size (S) for the invasive shrub (Ulex europaeus) in its native range and in non-native populations, and identified which other factors may contribute to seed bank variation between native and invaded regions. •Methods - We compared the native region (France) with two regions where Ulex is invasive, one with seed predators introduced for biological control (New Zealand) and another where seed predators are absent (La Réunion). We quantified seed bank size, plant dimensions, seed predation, and soil fertility for six stands in each of the three regions.•Key results - Seed banks were 9 to 14 times larger in the two invaded regions compared to native France. We found a positive relationship between current seed bank size and actual plant size, and that any deviation from this relationship was probably due to large differences in seed predation and/or soil fertility. We further identified three possible factors explaining larger seed banks in non-native environments: larger maternal plant size, lower activity of seed predators and higher soil fertility. •Conclusions - In highlighting a positive relationship between maternal plant size and seed bank size, and identifying additional factors that regulate soil seed bank dynamics in non-native ranges, our data offer a number of opportunities for invasive weed control. For non-native Ulex populations specifically, management focusing on 'S' (i.e. the reduction of the seed bank by stimulating germination, or the introduction of seed predators as biological control agents), and/or 'V' (i.e. by cutting mature stands to reduce maternal plant biomass) offers the most probable combination of effective control options.

This study has been supported by the French Dynamos project [ANR-07-BLAN-0222-01] and the Italian POLIGRID project [CUP B65B0900002007]; International audience; In this study, we evaluated trimethylsilyl (TMS) derivatives as derivatization reagents for the compound-specific stable carbon isotope analysis of soil amino acids by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). We used non-proteinogenic amino acids to show that the extraction-derivatization-analysis procedure provides a reliable method to measure delta C-13 values of amino acids extracted from soil. However, we found a number of drawbacks that significantly increase the final total uncertainty. These include the following: production of multiple peaks for each amino acid, identified as di-, tri- and tetra-TMS derivatives; a number of TMS-carbon (TMS-C) atoms added lower than the stoichiometric one, possibly due to incomplete combustion; different TMS-C delta C-13 for di-, tri- and tetra-TMS derivatives. For soil samples, only four amino acids (leucine, valine, threonine and serine) provide reliable delta C-13 values with a total average uncertainty of 1.3 parts per thousand. We conclude that trimethylsilyl derivatives are only suitable for determining the C-13 incorporation in amino acids within experiments using C-13-labelled tracers but cannot be applied for amino acids with natural carbon isotope abundance until the drawbacks described here are overcome and the measured total uncertainty significantly decreased.

Nitrogen supply to Merlot vines (Vitis vinifera L.), grown under controlled conditions, affected must quality and the anthocyanin content in berry skins irrespective of vegetative growth. High N supply delayed fruit maturation; berries had a higher arginine and a lower anthocyanin content with relatively more abundant acylated anthocyanins compared to berries of vines supplied with low N. During maturation the anthocyanin content in the skin of berries decreased; this was more significant in high-N vines. It is concluded that high nitrogen supply affects the metabolic pathway of anthocyanins in different ways, e.g. it delays the quantitative and qualitative biosynthesis and enhances their degradation during the final steps of berry maturation., VITIS - Journal of Grapevine Research, Vol. 42 No. 2 (2003): Vitis

International audience

International audience; The dynamics of sugar (hexose) concentration in ripening grape berries (Vitis vinifera L.) were simulated with a refined mechanistic model. Changes in sugar concentration were reproduced by the sum of sugar import (S), sugar metabolism (M) and water budget (W). S and W were derived from model inputs of fresh and dry mass, and M was simulated with a relative metabolism rate describing the depletion of hexose. The relative metabolism rate was associated with the relative growth rate of dry mass with a coefficient (k) that was constant for a given cultivar under various growth conditions (temperature, water supply, and source–sink ratio) but varied with genotype. The k value was ~20% higher for cv. Merlot than for cv. Cabernet Sauvignon, indicating more imported sugars would be depleted by Merlot than Cabernet Sauvignon. The model correctly simulated the negative effect of lowered leaf-to-fruit ratio and the positive effect of water shortage on sugar concentration. Sensitivity analysis revealed that the present model was weakly sensitive to k because of sugar accumulation being predominantly controlled by S, with M relatively small (~20%) with respect to the increment of sugar concentration. Model simulation indicated that the decreasing leaf-to-fruit ratio reduced S more than M and W, causing a net decrease in sugar concentration. In contrast, the water shortage decreased S less than M and W, resulting in a net increase in sugar concentration.

International audience; Theoretical plant growth models postulate that the relative rates of shoot and root growth are largely modulated by signals related to carbon and nitrogen status of the plant. To test this experimentally, 6-week-old vegetative cuttings of grapevine (Vitis vinifera L. cv Merlot) were grown aeroponically in different controlled conditions of irradiance (13.8, 8.4 and 5.3 mol PAR m(-2) day(-1)) and/or nitrogen nutrition (0.15 1.20 and 7.11 mM N). Total non-structural carbohydrates (TNC) and amino acids (FAA) in leaves and roots were analysed 0, 6 and 28 days after treatment initiation. Both whole-plant biomass accumulation as well as C and N contents were highly responsive to light and N availability. At day 28, plant dry weight was significantly reduced in shaded vines (-35% of that of the control plants) and stimulated under the high it-radiance environment (+30%). Deprivation of N enhanced root growth (+51%) at the expense of above-ground growth, whereas leaf dry weight was significantly greater in the high-N treatment than in the control. Vines grown under low-N and high irradiance conditions had the highest root-to-shoot ratios and those grown under low light and high N the lowest. Finally, redistribution of biomass among vegetative vine parts was significantly related to different indicators of the vine C:N status measured either at the whole-plant (N concentration) or at the organ level (TNC:FAA ratio), suggesting that root-to-shoot biomass partitioning was controlled by some aspect of plant C:N balance. Such relationships will be useful to improve allocation rules in a process-based growth model of grapevine. (c) 2005 Elsevier B.V. All rights reserved.

Grapevine nitrogen status was assessed by nitrogen content in leaf blade and petiole at veraison, in must at harvest and in pruned wood in December. The comparison of these indicators were done in vineyards bearing adults plants in the Atlantic and Mediterranean climates. Soil nitrogen offer were changed by soil grass cover, fertilization and irrigation. Leaf blade nitrogen (LBN) content cannot be simply predicted from soil texture, training characteristics and climate. Petiole and wood nitrogen content was less precise indicators compared to LBN content per unit dry weight. LBN content based on unit of leaf area usually constant along the growing season provides a complementary information on the leaf photosynthetic capacity and nitrogen availability for grapevine in summer. LBN content informs on the early growth grapevine access to soil and reserve nitrogen.Must and leaf blade nitrogen contents are significantly correlated. But it is shown that must N content is also changed by the yield and the soil capacity to provide nitrogen to the grapevine in summer. A simple predicting model of N in must is proposed. It is based on the availability of N in spring and summer and the positive effect of spring N on berry set up. Leaf blade and must N content considered both provided a complementary information on the grapevine N nutrition along the season.Sampling conditions for LBN content was tested. Primary leaves of a rank above 6 are very similar in N content and most representative of the grapevine N status. The LBN content on a leaf area basis is a more versatile expression because less variable along the growing season. The expressions of LBN content on the dry weight and leaf area can be obtained from a simple analysis by sampling leaf disks.