Nutrient cycling and soil leaching in eighteen pure and mixed stands of beech (Fagus sylvatica) and spruce (Picea abies)

Studies on the combined effects of beech–spruce mixtures are very rare. Hence, forest nutrition (soil, foliage) and nutrient fluxes via throughfall and soil solution were measured in adjacent stands of pure spruce, mixed spruce–beech and pure beech on three nutrient rich sites (Flysch) and three nutrient poor sites (Molasse) over a 2-year period. At low deposition rates (highest throughfall fluxes: 17 kg N ha⁻¹ year⁻¹ and 5 kg S ha⁻¹ year⁻¹) there was hardly any linkage between nutrient inputs and outputs. Element outputs were rather driven by internal N (mineralization, nitrification) and S (net mineralization of organic S compounds, desorption of historically deposited S) sources. Nitrate and sulfate seepage losses of spruce–beech mixtures were higher than expected from the corresponding single-species stands due to an unfavorable combination of spruce-similar soil solution concentrations coupled with beech-similar water fluxes on Flysch, while most processes on Molasse showed linear responses. Our data show that nutrient leaching through the soil is not simply a “wash through” but is mediated by a complex set of reactions within the plant–soil system.     

An analysis of employment patterns of domestic migrants and immigrants in a Rustbelt city: A study of Buffalo-Niagara Falls

This study evaluates employment patterns of domestic migrants and immigrants and also explores the role of ethnic niching for Asian and African American recent arrivals in the context of local structural transformation (e.g., the shift from manufacturing to services). Employment patterns are examined for industry-occupation groups using the 5% Public Use Micro Sample of the 2000 U.S. Decennial Census and the 2006–2010 of the American Community Survey. The study area is a Rustbelt city that has suffered from population loss: the Buffalo-Niagara Falls MSA. Location quotients and shift-share analysis are used to classify employment shifts into four industry-occupation groups: growing, transforming, declining, and emerging. Logistic regressions are estimated to identify the role of various demographic factors and ethnic niches on the employment of recent arrivals in the above four industry-occupation groups. The results show that the employment of recent arrivals vary by migration status and ethnicity. The role of ethnic niches is especially important in declining industry-occupation groups. The analytical framework can be used to understand where and how migrants, both domestic and immigrants, find work. Future studies can focus on the pros and cons of ethnic niching (e.g., barriers to suitable jobs, ethnic entrepreneurship through niche experience) as structural transformation continues across U.S. regions, especially with new technologies.     

Release of C and N from roots of peas and oats and their availability to soil microorganisms

Nutrient mobilisation in the rhizosphere is driven by soil microorganisms and controlled by the release of available C compounds from roots. It is not known how the quality of release influences this process in situ. Therefore, the present study was conducted to investigate the amount and turnover of rhizodeposition, in this study defined as root-derived C or N present in the soil after removal of roots and root fragments, released at different growth stages of peas (Pisum sativum L.) and oats (Avena sativa L.). Plants were grown in soil columns placed in a raised bed under outdoor conditions and simultaneously pulse labelled in situ with a ¹³C-glucose-¹⁵N-urea solution using a stem feeding method. After harvest, ¹³C and ¹⁵N was recovered in plant parts and soil pools, including the microbial biomass. Net rhizodeposition of C and N as a percentage of total plant C and N was higher in peas than in oats. Moreover, the C-to-N ratio of the rhizodeposits was lower in peas, and a higher proportion of the microbial biomass and inorganic N was derived from rhizodeposition. These results suggest a positive plant-soil feedback shaping nutrient mobilisation. This process is driven by the C and N supply of roots, which has a higher availability in peas than in oats.     

Effects of acid anion additions (trifluoroacetate and bromide) on soil solution chemistry of a northern hardwood forest soil

Experimental plots within the Hubbard Brook Experimental Forest, NH, were treated with sodium trifluoroacetate (TFA) and lithium bromide (Br), to study the impact of TFA alone and in the presence of increased anion concentrations (e.g. acid deposition) on the soil solution chemistry of a northern hardwood forest soil. Trifluoroacetate is a major atmospheric degradation product of replacement compounds of chlorofluorocarbons (CFC) and Br is widely used as a hydrologic tracer. Calculated drainage losses via soil water flow were less than 60% of inputs, added during the summer, and TFA and Br were temporarily retained in the soil until fall. The initial indication of an acid input of the treatments (HTFA, HBr) in the Bs2 horizon, which reflects stream water chemistry as well, was an increase of base cations in the soil solution, decreasing the soil's acid neutralizing capacity. Thereafter, trifluoroacetate and Br concentrations peaked after the peak in base cations, synchronous with peaks in H⁺ and Al concentrations. Organic anions, nitrate and chloride played the major role in accompaning base cations out of the solum. Sulfate retention at soil adsorption sites was increased by the presence of TFA and Br, reducing its role as a mobile anion of base cations in this experiment. Relative retention of anions for the whole profile of this northern hardwood forest soil was estimated by correlation analyses and input-output balances in decreasing order on an equivalant basis: SO₄ > TFA = Br ≥ Cl > NO₃ > organic anions. Recovery from acid additions were recorded within several weeks after the treatments were stopped. Evaluating the impact of added chemical compounds to soils must be considered within the context of linkages among element cycles and pools.     

Assessing the Effectiveness of Functional Genetic Screens for the Identification of Bioactive Metabolites

A common limitation for the identification of novel activities from functional (meta) genomic screens is the low number of active clones detected relative to the number of clones screened. Here we demonstrate that constructing libraries with strains known to produce bioactives can greatly enhance the screening efficiency, by increasing the “hit-rate” and unmasking multiple activities from the same bacterial source.     

Distribution of the timber quality attribute ‘knot surface’ in logs of Fagus sylvatica L. from pure and mixed forest stands

European Journal of Forest Research - Research on mixed forests has mostly focused on tree growth and productivity, or resistance and resilience in changing climate conditions, but only rarely on...     

Correction to: Climatic factors controlling stem growth of alien tree species at a mesic forest site: a multispecies approach

European Journal of Forest Research -     

Carotenoid absorption in humans consuming tomato sauces obtained from tangerine or high-beta-carotene varieties of tomatoes

Tomato sauces were produced from unique tomato varieties to study carotenoid absorption in humans. Tangerine tomatoes, high in cis-lycopene, especially prolycopene (7Z,9Z,7'Z,9'Z), and high-beta-carotene tomatoes as an alternative dietary source of beta-carotene were grown and processed. Sauces were served after 2 week washout periods and overnight fasting for breakfast to healthy subjects (n = 12, 6M/6F) in a randomized crossover design. The serving size was 150 g (containing 15 g of corn oil), tangerine sauce containing 13 mg of lycopene (97.0% as cis-isomers) and high-beta-carotene sauce containing 17 mg of total beta-carotene (1.6% as the 9-cis-isomer) and 4 mg of lycopene. Blood samples were collected 0, 2, 3, 4, 5, 6, 8, and 9.5 h following test meal consumption and carotenoids determined in the plasma triacylglycerol-rich lipoprotein fraction by HPLC-electrochemical detection. Baseline-corrected areas under the concentration vs time curves (AUC) were used as a measure of absorption. AUC0-9.5h values for total lycopene in the tangerine sauce group were 870 +/- 187 (nmol.h)/L (mean +/- SEM) with >99% as cis-isomers (59% as the tetra-cis-isomer). The AUC0-9.5h values for total beta-carotene and lycopene after consumption of the high-beta-carotene sauce were 304 +/- 54 (4% as 9-cis-carotene) and 118 +/- 24 (nmol.h)/L, respectively. Lycopene dose-adjusted triacylglycerol-rich lipoprotein AUC responses in the tangerine sauce group were relatively high when compared to those in the literature and the high-beta-carotene group. The results support the hypothesis that lycopene cis-isomers are highly bioavailable and suggest that special tomato varieties can be utilized to increase both the intake and bioavailability of health-beneficial carotenoids.