Identity of mass-flowering crops moderates functional trait composition of pollinator communities

Landscape Ecology - Pollinator declines and functional homogenization of farmland insect communities have been reported. Mass-flowering crops (MFC) can support pollinators by providing floral...     

Growth response of Ficus benjamina to limited soil volume and soil dilution in a skeletal soil container study

The interactive effects of rooting volume and nutrient availability in a skeletal soil medium designed to meet street tree and pavement needs were observed in a containerized experiment. Benjamin fig (Ficus benjamina L.) was grown in a stone-soil blended skeletal soil material (CU-Soil™) and compared to a loam soil. The same topsoil used as the soil component in the skeletal soil material was used as the sole component in the comparison soil-only treatment.Plants grown in the skeletal soil material had reduced leaf tissue N content and depressed growth compared with plants grown in non-diluted soil. No other mineral deficiencies were found. Leaf number, chlorophyll concentration, shoot weight, and root characteristics were all affected.Reduced growth from soil dilution could be offset by the provision of an enlarged rooting volume for root development. Large containers of skeletal soil were observed to have smaller root systems compared to equivalent net volumes of loam soil at the first two harvest dates of the study. By the end of the study, the large containers of skeletal soil were observed to have developed larger root systems compared to equivalent net volumes of loam soil; resulting in comparable leaf N levels and total plant dry matter. Plants in skeletal soil had lower shoot: root ratios at the end of the study. Investing resources to further root growth in times of nutrient shortages is a probable plant reaction as evidenced by differences in specific root length between treatments. The study allowed a method for directly partitioning the containerization effect by having equivalent amounts of soil over two volumes.     

Biochar‐compost substrates in short‐rotation coppice: Effects on soil and trees in a three‐year field experiment

Both biochar and compost may improve carbon sequestration and soil fertility; hence, it has been recommended to use a mixture of both for sustainable land management. Here, we evaluated the effects of biochar–compost substrates on soil properties and plant growth in short rotation coppice plantations (SRC). For this purpose, we planted the tree species poplar, willow, and alder in a no‐till field experiment, each of them amended in triplicate with 0 (= control) or 30 Mg ha^?1 compost or biochar–compost substrates containing 15% vol. (TPS15) and 30% vol. biochar (TPS30). For three years running, we analyzed plant growth as well as soil pH, potential cation exchange capacity (CEC), stocks of soil organic carbon (SOC), total N, and plant‐available phosphate and potassium oxide.Biochar‐compost substrates affected most soil properties only in the topsoil and for a limited period of time. The CEC and total stocks of SOC were consistently elevated relative to the control. After three years the C gain of up to 6.4 Mg SOC ha^?1 in the TPS30 plots was lower than the added C amount. Especially in the case of TPS30 treatment, C input was characterized by the greatest losses after application, although the black carbon of the biochar was not degraded in soil. Additionally, tree growth and woody biomass yield did not respond at all to the treatments. Overall, there were few if any indications that biochar–compost substrates improve the performance of SRC under temperate soil and climate conditions. Therefore, the use of biochar for such systems is not recommended.     

Effect of temperature on the expression of cytoplasmic male sterility in cultivated barley (Hordeum vulgare L.)

Twenty‐three cytoplasmic male sterile BC₁F₁ barley lines were exposed to varying temperature treatments (TTs) to examine the effect of temperature on the stability of the expression of cytoplasmic male sterility (cms). The TTs used for this test were: (i) controlled low‐temperature treatment of 16°C (CL), (ii) controlled medium‐temperature treatment of 21–24/16–17°C day/night (CM) and (iii) ambient glasshouse‐temperature treatment of 24–41/16–17°C day/night (AG). The expression of cms was found to be variably influenced by temperature and by the genetic background of the cms recipient lines. Ten cms lines exhibited consistently complete male sterility over TTs, indicating that these lines are completely under cms genes control, while other lines showed partial revision to fertility across different TTs with profound influence of warm temperatures (CM and AG) in breaking down the cms in barley.     

Nitrogen Mineralization Potential as Influenced by Microbial Biomass,Cotton Residues and Temperature

Integrating information on nitrogen (N) mineralization potentials into a fertilization plan could lead to improved N use efficiency. A controlled incubation mineralization study examined microbial biomass dynamics and N mineralization rates for two soils receiving 56 and 168 kg N ha^?1 in a Panoche clay loam (Typic Haplocambid) and a Wasco sandy loam (Typic Torriorthent), incubated with and without cotton (Gossypium hirsutum L.) residues at 10 and 25°C for 203 days. Microbial biomass activity determined from mineralized carbon dioxide (CO₂) was higher in the sandy loam than in clay loam independent of incubation temperature, cotton residue addition and N treatment. In the absence of added cotton residue, N mineralization rates were higher in the sandy loam. Residue additions increased N immobilization in both soils, but were greater in clay loam. Microbial biomass and mineralization were significantly affected by soil type, residue addition and temperature but not by N level.     

Potential of acrylamide formation,sugars, and free asparagine in potatoes: a comparison of cultivars and farming systems

Glucose, fructose, sucrose, free asparagine, and free glutamine were analyzed in 74 potato samples from 17 potato cultivars grown in 2002 at various locations in Switzerland and different farming systems. The potential of these potatoes for acrylamide formation was measured with a standardized heat treatment. These potentials correlated well with the product of the concentrations of reducing sugars and asparagine. Glucose and fructose were found to determine acrylamide formation. The cultivars showed large differences in their potential of acrylamide formation which was primarily related to their sugar contents. Agricultural practice neither influenced sugars and free asparagine nor the potential of acrylamide formation. It is concluded that acrylamide contents in potato products can be substantially reduced primarily by selecting cultivars with low concentrations of reducing sugars.     

A concept of Gleyization and its role in the pedogenesis

Three simple factors ‐ excessive moistening, anaerobic microflora and organic matter, are indispensable and sufficient conditions for gley formation. This process is always characterised by a non‐silicate iron loss from the soil fine earth or soil plasma. Gley formation takes place under conditions of stagnant or stagnant‐percolative water regimes.

In the second case gley formation induces a drastic acidification of the mineral soil part, lessivage, removal of iron, aluminium, calcium, magnesium, bleaching of the soil fine earth, and it appears the features of soil with eluvial, acid, bleached horizons. Therefore soils with such horizons should be regarded as manifestations of gley formation in conditions stagnant ‐percolative water regime on acid, neutral or leached parent material. Under influence of stagnant water regimes Fe of mineral substrat is removed and unconsiderable eluviation of Ca and Mg takes place. pH of parent material does not change or has the trend to increase. In this case does not arise a soil with bleached horizons.     

Soil physical properties of selected soil series in relation to compaction and erosion on farmers’ fields at Abeokuta,southwestern Nigeria

This study evaluated physical properties of selected soil series and their implications on the soil compaction and erosion in Abeokuta, southwestern Nigeria. Daily rainfall data (1999–2007) were collected to estimate the rainfall erosivity. Seven soil series (Iwo, Iseyin, Ekiti, Jago, Okemesi, Apomu, and Egbeda) were sampled from 0–15, 15–30, and 30–50 cm depths for particle size distribution, organic carbon, pH, upper plastic limit, and compactibility (Proctor test). Microtopographical changes along and across toposequences of two farmers’ fields cleared mechanically and manually, respectively, were monitored using the erosion pin method. Mean annual erosivity (EI30) was high (7646 MJ mm ha^?1 hr^?1). Particle size, organic carbon, and pH were similar (p ≥ 0.05), while upper plastic moisture was ≤?2% among different soil series. Soil-moisture density curves indicated a maximum bulk density of 1.77–1.99 g cm^?3 for a moisture range of 7.6–14%; while the soils were prone to compaction at low moisture content. Microtopographic changes were found between –2 and 0 cm and –8 and –2 cm on mechanically and manually cleared farmland, respectively. Spatial dependence showed that the soil erosion could be predicted within 5–8 m distance. To avoid erosion and compaction, soil water content should be less than 7.6% before the introduction of mechanical tillage.     

Sub-optimal study design has major impacts on landscape-scale inference

Landscape-scale processes (e.g. habitat loss) are major drivers of the global biodiversity crisis, but the complexity and size of landscapes makes study design at this scale difficult. However, the impact of statistical problems associated with sub-optimal study design on inferences drawn from landscape-scale studies is poorly understood. Here, we examine how three common statistical ‘pitfalls’ associated with sub-optimal study design – (1) using landscapes that overlap in space; (2) using only a portion of the potential range of the landscape predictor variable(s) of interest; (3) failing to account for correlations among landscape predictor variables – affect the inferred relationships between the abundances of six species of anurans and the amount of forest in the landscape using a large (n = 1141) empirical dataset from Wisconsin and Michigan, USA. We show that sub-optimal study design alone can be sufficient to cause a switch in the sign of the inferred relationship between a species response and landscape structure, and that using only a portion of the potential range of a predictor variable, and correlations between predictor variables, are particularly likely to affect inferences. Our results also provide the first evidence of a non-monotonic relationship between forest amount and gray treefrog abundance, and suggest that inconsistencies in the literature about the inferred relationships between anuran presence/abundance and forest amount in the Great Lakes basin are likely largely due to sampling design issues. Increased attention to study design is therefore necessary for the development of robust generalizations in landscape ecology.