The effects of Douglas-fir on tree-specific arthropod communities in mixed species stands with European beech and Norway spruce

The ecological effects of planting exotic Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] in Central Europe are still poorly understood. The aim of this study was to answer the question of whether Douglas-fir affects tree specific arthropod communities in different mature forest types (Douglas-fir, spruce and beech dominated) in Southern Germany. Therefore, arthropod communities of stem and tree crown strata of Douglas-fir and spruce (Picea abies L.) were sampled in the years 1999–2001 using arboreal photo-eclectors and flight interception traps. Statistical analysis was conducted for all species and focused on conifer specialists at three levels: (1) species diversity, (2) guild structure and (3) community structure. Within the stem stratum, species diversity was significantly higher on spruce than on Douglas-fir independent of year and stand composition. This could not be explained by a single feeding guild, rather by species changing strata during the vegetation period. In contrast, species diversity in tree crowns was approximately the same for both conifer species. However, communities in Douglas-fir crowns were conspicuously different from those in spruce crowns, especially in the Douglas-fir dominated stand type. While zoophagous insects exhibited higher activity on Douglas-fir in 2000, xylophagous beetles were more abundant on spruce in 2001. In European beech stands with widely spaced Douglas-fir trees, the site specific and broad-leaved tree related fauna might be maintained. In addition, Douglas-fir with its resource of Adelges cooleyi and crowns that overtop the broad-leaved tree canopy, offer additional resources for several aphidophagous and thermophile species.     

Modeling spatial variability in the life-cycle costs of low-volume forest roads

Cost estimation is probably the most decisive factor in the process of computer-aided, preliminary planning for low-volume road networks. However, the cost of construction is normally assumed to be route-independent for a specific project area, resulting in sub-optimal layouts. This is especially true for mountainous terrain and in areas with unstable subsoil. Here, we present a model for more accurately estimating spatial variability in road life-cycle costs, based on terrain surface properties as well as geological properties of the subsoil. This parametric model incorporates four structural components: embankment, retaining structures, pavement, and drainage and stream-crossing structures. It is linked to a geo-database that allows users to derive location-specific parameter values as input. In applying this model, we have demonstrated that variability in costs ranges widely for mountainous areas, with the most expensive construction being approximately five times greater there than on more favorable sites. This variability strongly affects the optimal layout of a road network. First, when location-specific slope gradients are considered, costs are reduced by about 17% from those calculated via currently available engineering practices; when both slope gradient and geotechnical formations are included, those costs are decreased by about 20%. Second, the length of the road network is increased by about 4% and 10% respectively, compared with current practices.     

Effects of the needle bladder rust (Chrysomyxa rhododendri) on Norway spruce: implications for subalpine forests

Norway spruce trees in the subalpine forests of the European Alps are frequently attacked by the needle rust Chrysomyxa rhododendri. The obligate parasite undergoes a complex life cycle with a host shift between rhododendrons (Rhododendron sp.) and Norway spruce [Picea abies (L.) Karsten] and causes a yellowing and defoliation of the current-year needles in summer. Infected trees show several anatomical, morphological and physiological modifications, including a decrease in pigment content and net photosynthesis of infected needles, lower biomass production and reduced radial and height growth. The consequences are diminished timber yield and cripple growth. Because of repeated heavy infections in recent years, forest managers report increasing difficulties in both natural regeneration and afforestation at high elevation sites, where rhododendrons occur. This review gives a summary of the present knowledge about the effects of C. rhododendri infections on Norway spruce, including so far unpublished findings and with particular attention to the phenomena of resistant trees. Implications for subalpine forests and counter strategies are discussed.     

Yield decrease in sugar beet caused by reduced tillage and direct drilling

In a long-term series of on-farm tillage trials (10 loessial sites in southern and eastern Germany; annual mouldboard ploughing 0.25–0.3 m deep, mulching with a rigid-tine cultivator 0.1–0.15 m deep, direct drilling with no tillage except seedbed preparation for sugar beet solely) sugar beet yield was significantly decreased by direct drilling compared to ploughing. This study was conducted to (i) show that the lower plant density caused by mulching and direct drilling contributes to yield decrease but explains effects just partially, and (ii) determine the relation between soil structural properties and sugar beet yield. In 2003–2005 plant density experiments (53,000, 65,000 and 82,000 plants ha^?1) were introduced to tillage plots on five selected environments. Yield and soil structural properties of four layers representing 0–0.43 m soil depth were determined.White sugar yield (WSY) significantly declined with direct drilling compared to ploughing treatment, whereas mulching treatment diminished WSY less pronounced. Moreover, decreasing plant density significantly lowered WSY. No interactions between tillage and plant density occurred, revealing that both factors additively affected WSY.Decreasing tillage depth increased penetration resistance (PR) and dry bulk density (DBD), and diminished air filled pore volume (AFPV) in the topsoil down to 0.27 m depth. Several soil structural parameters were closely correlated with each other as well as WSY. Variation of single parameters explained up to 60% of WSY variance attributed to tillage. Combining DBD from 0.03 to 0.07 m depth, average PR from 0.03 to 0.27 m and AFPV from 0.03 to 0.18 m soil depth explained 77% of the tillage effect. Nevertheless, multi-collinearity of soil physical parameters allowed no clear conclusions on the cause-and-effect mechanisms.Conclusively, lowered plant density and soil structure degradation due to reduced tillage may independently decrease sugar beet yield. When grown on loessial soils this crop requires mechanical loosening down to 0.15–0.20 m depth to produce high yields.     

Yield and quality of pectins extractable from the peels of thai mango cultivars depending on fruit ripeness

Pectins, recovered from the peels of four mango ( Mangifera indica L.) cultivars by mimicking industrial techniques, were evaluated in terms of yield, composition, macromolecular properties, and technofunctional quality. Freeze-dried peels of mature-green fruits, after major mesocarp softening, and at full ripeness were extracted using hot acid. The pectins were precipitated in propan-2-ol and their crude yields quantified as alcohol-insoluble substance. Like apple pomace, the dried peels provided hardly acetylated (DAc < 6.3%) rapid-set to ultrarapid-set high-methoxyl pectins at starch-adjusted yields of 11-21 g/100 g. However, despite similar high molecular weight fractions and galacturonic acid/rhamnose ratios, their average molecular weight was markedly reduced by a characteristic, almost monodisperse fraction of 16000-19000. Expanded galactans, indicated by galactose/rhamnose ratios of 15-24 mol/mol, probably represented arabinogalactan side-chain fragments withstanding hot-acid extraction at pH 1.5 and 2.0, as implied by arabinose/galactose ratios of 8-15 and 33-56 mol/100 mol, respectively. Limited galacturonic acid contents made the mango peel pectins less valuable than commercial apple pectins with regard to gelling capacity and thickening properties. Whereas starch and matrix glycan fragments almost completely degraded during ripening, depolymerization of pectins and galactans was insignificant. Technofunctional properties, modulated by extraction at different pH values, were ascribed to structural differences influencing macromolecular entanglements.     

Analysis of ammonia losses after field application of biogas slurries by an empirical model

Due to energy crises and stricter environmental regulations, renewable energy sources like bio‐methane produced by anaerobic digestion (biogas) become increasingly important. However, the application of slurries produced by biogas fermentation to agricultural land and subsequent ammonia emission may also create environmental risks to the atmosphere and to N‐limited ecosystems. Evaluating ammonia loss from agricultural land by model simulation is an important tool of agricultural‐systems analysis. The objective of this study was the systematical comparison of ammonia volatilization after application of two types of biogas slurries containing high amounts of energy crops in comparison with conventional animal slurries and to investigate the relative importance of factors affecting the emission process through an empirical model. A high number of ammonia‐loss field measurements were carried out in the years 2007/08 in biogas cropping systems in N Germany. The study consisted of simultaneous measurement of NH₃ losses from animal and biogas slurries in multiple‐plot field experiments with different N‐fertilization levels. The derived empirical model for the calculation of NH₃ losses based on explanatory variables gave good predictions of ammonia emission for both biogas and pig slurries. The root mean square error (RMSE) and mean bias error (MBE) of the empirical model for validation data were 2.19 kg N ha^–1 (rRMSE 29%) and –1.19 kg N ha^–1, respectively. Biogas slurries produced highest NH₃ emissions compared to the two animal slurries. In view of the explanatory variables included in the model, total NH$ _4^+ $ application rate, slurry type, temperature, precipitation, crop type, and leaf‐area index were important for ammonia‐volatilization losses.     

Enhanced non-extractable residue formation of 14C-metalaxyl catalyzed by an immobilized laccase

We studied the influence of an immobilized laccase from Trametes versicolor on non-extractable residue (NER) formation of the systemic fungicide ¹⁴C-metalaxyl in soil. We added the enzyme (130 mU/g DW) to soil sterilized by gamma irradiation and observed that the amount of NER (6.3 % of applied radioactivity) after 10 days of incubation was enhanced about twofold compared to the sterile soil without laccase addition. Residues formed within samples without enhanced enzyme activity were mainly bound via ester linkages to all fractions of humic matter, i.e., fulvic acids, humic acids, non-humines, and humines, respectively. In contrast, residues formed in presence of immobilized laccase were more strongly bound by covalent linkages such as ether and C-C bonds, especially to humic acids. After chemical degradation of the humic matter, it could be observed that all NER contained the first major transformation product, i.e., metalaxyl acid. The findings underline that the residue formation of metalaxyl in soil may be partly catalyzed by immobilized extracellular oxidative enzymes through oxidative coupling reactions within the humic matter.     

The use of organic and mineral fertilizers in reforestation and in revitalization of declining protective forests in the alps

BIOSOL BIOSOL and BACTOSOL are registered trademarks of Biochemie Ges.m.b.H., Kundl, Austria. and BACTOSOL BIOSOL and BACTOSOL are registered trademarks of Biochemie Ges.m.b.H., Kundl, Austria. organic fertilizers based on residue from commercial antibiotic production, were tested as an alternative to mineral fertilizers in reforestation and in revitalization of Norway spruce stands (Picea abies) affected by forest decline. Due to its slow release of N and its stimulation of root growth, the organic fertilizer was superior to mineral fertilizer in enhancing growth of spruce planted in nutrient poor soil with low nutrient retention capacity, especially when combined with magnesium carbonate fertilizer. In mature stands, basal area increment responded positively and significantly to both mineral fertilizer and BIOSOL. So far no pronounced effects of fertilizer treatment on seed production and viability were observed. Fertilization in the moderate amounts employed had no adverse effects on microbial activity in the soil and mycorrhizal status and thus seems to be a safe method to increase tree vigor without dramatically changing site parameters.