How much influence does landscape-scale physiography have on air temperature in a mountain environment?

Spatio-temporal patterns of temperature in mountain environments are complex due to both regional synoptic-scale and landscape-scale physiographic controls in these systems. Understanding the nature and magnitude of these physiographic effects has practical and theoretical implications for the development of temperature datasets used in ecosystem assessment and climate change impact studies in regions of complex terrain. This study attempts to quantify the absolute and relative influence of landscape-scale physiographic factors in mediating regional temperatures and assess how these influences vary in time. Our approach was to decompose the variance in in situ temperature measurements into components associated with regional free-air temperature estimates and local physiographic effects. Near-surface air temperature data, collected between 1995 and 2006 from 16 meteorological stations in the Lake Tahoe region of California, USA were regressed against free-air temperature (North American Regional Reanalysis dataset) for the same period. Residuals from this fit represent spatial deviations from the regional mean and were modeled as a function of physiographic position on the landscape using variables derived from terrain analysis techniques. Linear models relating temperature residuals to physiographic variables explained roughly 10–90% of the variance in temperature residuals and had root mean squared error of 1.2–2.0 °C, depending upon the type of measurement and time of year. Results demonstrate that: (1) regional temperature patterns were the principle driver of surface temperatures explaining roughly 70–80% of the variance in in situ measurements; (2) the remaining variance was largely explained by spatial variability in landscape-scale physiographic variables; (3) the influence of physiographic drivers varied seasonally and was influenced by regional conditions. Periods of well-mixed atmospheric conditions lend themselves to the use of simple elevation-based lapse rate models for temperature estimation whereas other physiographic effects become more prominent during periods of enhanced atmospheric stability; and lastly (4) small differences in temperature due to landscape position, when integrated over time, can have a prominent effect on water balance and thus hydrologic and ecologic processes.     

Reprint of “Soil extracellular enzyme dynamics in a changing climate”

Assays for extracellular enzyme activity (EEA) have become a common tool for studying soil microbial responses in climate change experiments. Nevertheless, measures of potential EEA, which are conducted under controlled conditions, often do not account for the direct effects of climate change on EEA that occur as a result of the temperature and moisture dependence of enzyme activity in situ. Likewise, the indirect effects of climate on EEA in the field, that occur via effects on microbial enzyme producers, must be assessed in the context of potential changes in plant and soil faunal communities. Here, EEA responses to warming and altered precipitation in field studies are reviewed, with the goal of evaluating the role of EEA in enhancing our understanding of soil and ecosystem responses to climate change. Seasonal and interannual variation in EEA responses to climate change treatments are examined, and potential interactions with elevated atmospheric CO₂, increased atmospheric N deposition and changes in disturbance regimes are also explored. It is demonstrated that in general, soil moisture manipulations in field studies have had a much greater influence on potential EEA than warming treatments. However, these results may simply reflect the low magnitude of soil warming achieved in many field experiments. In addition, changes in plant species composition over the longer term in response to warming could strongly affect EEA. Future challenges involve extending studies of potential EEA to address EEA responses to climate change in situ, and gaining further insights into the mechanisms, such as enzyme production, stabilization and turnover, that underlie EEA responses.     

Salinity effects on annual bedding plants in a peat‐perlite medium and solution culture

Annual vinca (Catharanthus roseus (L.) G. Don ‘Pink Carpet'), geranium (Pelargonium x hortorum L. H. Bailey ‘Jackpot'), and marigold (Tagetes erecta L. ‘First Lady') were grown in a sphagnum peat moss and perlite medium. Plants were irrigated with solutions of different salinity by the addition of 0.0, 1.0, 2.0, 4.0, and 8.0 g/1 of a NaCl and CaCl₂ mixture resulting in solution electrical conductivity (EC) values of about 1.3, 3.0, 4.5, 7.9, and 13.9 ds/m, respectively. In another experiment marigold and geranium were grown in solution culture containing the same salt mixture at 0.0, 1.0, 4.0, and 8.0 g/1 with EC values of 1.4, 3.0, 7.4, and 12.5 ds/m, respectively. All species showed some salinity tolerance up to 2.0 g/1 in peat‐perlite and 1.0 g/1 in solution culture as growth reductions were below 10% and no foliar injury occurred. Foliar injury occurred on marigold and geranium, but not annual vinca, at 4.0 and 8.0 g/1 in both growing media. On a concentration basis, recently mature leaves sampled from marigold grown in peat‐perlite contained more chloride (Cl) but less sodium (Na) than geranium and annual vinca. However results of the solution culture experiment showed that, with the exception of 1.0 g/1 treatment, geranium and marigold plants absorbed the same amount of Cl and Na when content was expressed on a mg/g dry weight basis. The low Na concentration in marigold leaves was a reflection of restricted translocation of Na from the roots to the shoots.     

Starter fertilizer effects on grain sorghum hybrids grown on a soil high in residual phosphorus in a no‐tillage environment

Conservation tillage crop production systems have become common in the central Great Plains because they reduce soil erosion and increase water‐use efficiency. The high residue levels associated with no‐tillage systems can cause soils to be cool and wet which can reduce nutrient uptake and growth of crops. Starter fertilizer applications have been effective in improving nutrient uptake even on soils high in available nutrient elements. Resent research indicates that corn (Zea mays L.) hybrids differ in their responses to starter fertilizer. No information is currently available concerning grain sorghum [Sorghum bicolor (L.) Moench] hybrid response to starter fertilizer. The objective of this study was to evaluate grain sorghum hybrid responses to starter fertilizer in a no‐tillage environment on a soil high in available phosphorus (P). This field experiment was conducted from 1995 to 1997 at the North Central Kansas Experiment Field, located near Belleville, on a Crete silt loam soil (fine, montmorillonitic, mesic, Pachic Arguistoll). Treatments consisted of 12 grain sorghum hybrids and two starter fertilizer treatments. Fertilizer treatments were starter fertilizer [34 kg nitrogen (N) and 34 kg P₂O₅ ha^‐1] or no starter fertilizer. Starter fertilizer was applied 5 cm to the side and 5 cm below the seed at planting. Immediately after planting, N was balanced on all plots to give a total of 168 kg N ha^‐1. In all three years of the experiment, grain yield, total P uptake (grain plus stover), grain moisture content at harvest, and days to mid‐bloom were affected by a hybrid x starter fertilizer interaction. Starter fertilizer consistently increased yields, reduced harvest grain moisture, improved total P uptake, and reduced the number of days needed from emergence to mid‐bloom of Pioneer 8505, Pioneer 8522Y, Pioneer 8310, Dekalb 40Y, Dekalb 48, Dekalb 51, Dekalb 55, and Northrup King 524, buthadno effect on Pioneer 8699, Dekalb 39Y, Northrup King 383Y, and Northrup King 735. When averaged over the three years, starter fertilizer increased grain yield of responding hybrids (hybrids in which the 3‐year average grain yield was significantly increased by the application of starter fertilizer) by 920 kg ha^‐1. In responding hybrids, starter fertilizer reduced grain moisture at harvest by 54 g kg¹ and also shortened the period from emergence to mid‐bloom by five days. Starter fertilizer increased V6 stage aboveground dry matter production and N and P uptake of all hybrids tested. Results of this work show that in high residue production systems even on soils high in available P, starter fertilizer can consistently increase yield of some hybrids, whereas other hybrids are not affected.     

Can phosphorus fertilizers sparingly soluble in water decrease phosphorus leaching loss from an acid peat soil?

The potential risk of phosphorus (P) loss in surface run‐off can be decreased using sparingly soluble forms of P fertilizer (e.g. reactive phosphate rock (RPR)). However, it is unclear whether RPR can decrease P loss in leachate, especially when applied to soils with a small anion storage capacity (viz. P sorption capacity) and pH. Our hypothesis was that at low soil pH, the solubility of RPR would increase and result in P losses in leachate similar to those receiving single superphosphate (SSP), but at higher pH, less P would be lost from soils receiving RPR than SSP. Lysimeters containing a crushed, sieved acid mesic Organic (viz. peat) subsoil (30–60 cm) were limed to pH 4.5, 5.5 or 6.5 and treated with SSP or RPR at rates of 0, 50, 100 or 200 kg P/ha. Lysimeters were sown with ryegrass and watered over 12 months under controlled conditions and the leachate collected. Losses of filtered (< 0.45 μm) reactive inorganic P (FRP) and unreactive or organic P (FUP) in leachate were greatest for pH 4.5 treatments and least for the pH 6.5 treatments. The difference in FRP and FUP leachate losses in RPR‐ and SSP‐treated soils was smaller at pH 4.5 and 5.5, and increased at pH 6.5 as losses from soils receiving RPR decreased compared to those receiving SSP. The results suggest that RPR can be used as a strategy to decrease P losses in leachate from an acid Organic soil with small P sorption capacity when limed to > pH 5.5.     

Can differences in soil community composition after peat meadow restoration lead to different decomposition and mineralization rates?

Reducing decomposition and mineralization of organic matter by increasing groundwater levels is a common approach to reduce plant nutrient availability in many peat meadow restoration projects. The soil community is the main driver of these processes, but how community composition is affected by peat meadow restoration is largely unknown. Furthermore, it is unclear whether restoration induced changes could lead to altered decomposition and mineralization rates. We determined soil community composition in restored peat meadows with different groundwater levels and soil pH. This composition was subsequently used in food web model calculations of C and N mineralization rates to assess whether differences in soil community composition may have contributed to differences in decomposition and mineralization rates observed between these meadows.Community composition of micro-organisms, Collembola and Enchytraeidae differed considerably between meadows and were correlated with differences in groundwater levels and soil pH. Collembolan and enchytraeid species from wet and neutral environments were more abundant at meadows with higher groundwater levels. Lower fungal to bacterial PLFA ratios and higher numbers of protozoa indicated an increased importance of the bacterial part of the food web at meadows with higher groundwater levels. Food web model calculations suggested that the observed changes in community composition would lead to higher rates of C and N mineralization at meadows with high groundwater levels. Results from modeling were consistent with field measurements of C mineralization, but not with measurements of N mineralization.We conclude that understanding changes in soil community composition in response to specific restoration measures may help us to better understand ecosystem responses to wetland restoration schemes, especially regarding soil biogeochemical processes.     

The versatile,changing, and advancing roles of fish in sediment toxicity assessment—a review

Purpose  

Sediments serve as integral and dynamic parts of our aquatic systems. Within the last 15 to 20 years, however, the scientific community has begun noticing deterioration of sediment quality at an alarming rate worldwide. Sediments are now harboring hazardous pollutants that can directly influence water quality, thereby creating very stressful conditions for aquatic life. As a consequence, global efforts were initiated in the early 1970s, to find ways to assess sediment quality. Because of their obvious ecological and economic significance, fish have remained a major taxonomic group for appraising the general quality of aquatic systems. However, for sediment risk assessment, fish have lagged behind invertebrates due to their mobility and generally, pelagic lifestyle. To our knowledge, this is the first paper that comprehensively presents and reviews the versatile role of fish in assessing the state of health of aquatic sediments.     

Potentially bioavailable metals in sediment from a tropical polymictic environment—Rio Grande Reservoir,Brazil

Background, aim and scope  Although many recent studies have focused on sediment potential toxicity, few of them were performed in tropical shallow aquatic environments. Those places can suffer short-time variations, especially due to water column circulations generated by changes in temperature and wind. Rio Grande reservoir is such an example; aside from that, it suffers various anthropogenic impacts, despite its multiple uses. Materials and methods  This work presents the first screening step for understanding sediment quality from Rio Grande reservoir by comparing metal content using three different sediment quality guidelines. We also aimed at verifying any possible spatial heterogeneity. Results and discussion  We found spatial heterogeneity varying according to the specific metal. Results showed a tendency for metals to remain as insoluble as metal sulfide (potentially not bioavailable), since sulfide was in excess and sediment physical–chemical characteristics contribute to sulfide maintenance (low redox potential, neutral pH, low dissolved oxygen, and high organic matter content). On the other hand, metal concentrations were much higher than suggested by Canadian guidelines and regional background values, especially Cu, which raises the risk of metal remobilization in cases of water circulation. Further study steps include the temporal evaluation of AVS/SEM, a battery of bioassays and the characterization of organic compounds.     

Acrylamide: a dietary carcinogen formed in vivo?

Acrylamide, a chemical formed during heating of human foods, reacts with N-terminal valine in hemoglobin (Hb) and forms stable reaction products (adducts). These adducts to N-terminal valine in Hb have been used to estimate daily intake of acrylamide. Daily intake of acrylamide estimated from Hb adduct levels was higher than daily intake estimated from dietary questionnaires, possibly indicating other sources of exposures. Therefore, in this study the possible endogenous formation of acrylamide was investigated by treating mice with FeSO 4, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-hydrochloric acid (MPTP), or methamphetamine (METH). Acrylamide Hb adducts were determined, and a significant increase ( p < 0.05) in acrylamide Hb adduct levels was observed 24 h following treatment with FeSO 4 and 72 h following treatment with MPTP or METH. The results of this study show that acrylamide Hb adduct levels are increased in mice treated with compounds known to induce free radicals, thus suggesting the endogenous production of acrylamide.     

The growth of tagestes erecta,petunia hybrida nana compacta and myosotis alpestris in a range of peat‐based container media

Abstract

The dry matter yield and nitrogen content of marigold (Tagestes erecta), petunia (Petunia hybrida nana compacta) and forget‐me‐not (Myosotis alpestris) plants growing in a range of peat‐based container media amended with different proportions of either sand, perlite, pumice, sawdust, bark chips or soil were studied under glasshouse nursery conditions.

Plant responses differed between species as manifested by their different correlations with measured moisture and aeration characteristics of the media. Marigold and petunia were adversely affected by excessive moisture content as demonstrated by their negative correlation with micropore water and container capacity. However, forget‐me‐not, being adapted to relatively high moisture regimes, responded adversely to increased aeration.     

Breakfast eating and overweight in a pre-school population: is there a link?

OBJECTIVES: To analyse the socio-economic factors related to breakfast eating, the association between breakfast eating and overweight, and to gain a more thorough understanding of the relationship between these two elements in a population-based cohort of 4.5-year-old children. We hypothesised that a relationship could be observed between breakfast skipping and overweight independently of socio-economic factors such as ethnicity, maternal education, single parenting and family income. DESIGN: A population-based study whereby standardised nutritional interviews were conducted with each child's parent. The children's height and weight were taken by a trained nutritionist and parents were asked about their child's breakfast eating. SETTING: The analyses were performed using data from the Québec Longitudinal Study of Child Development (1998-2002), conducted by Santé Québec (Canada). SUBJECTS: Subjects were 1549 children between the ages of 44 and 56 months, with a mean age of 49 months. RESULTS: Almost a tenth (9.8%) of the children did not eat breakfast every day. A greater proportion of children with immigrant mothers (19.4% vs. 8.3% from non-immigrant mothers), with mothers with no high school diploma (17.5% vs. <10% for higher educated mothers) and from low-income families (15% for income of $39,999 or less vs. 5-10% for better income) did not eat breakfast every day. Not eating breakfast every day nearly doubled the odds (odds ratio=1.9, 95% confidence interval 1.2-3.2) of being overweight at 4.5 years when mother's immigrant status, household income and number of overweight/obese parents were part of the analysis. CONCLUSION: Although our results require replication before public policy changes can be advocated, encouraging breakfast consumption among pre-school children is probably warranted and targeting families of low socio-economic status could potentially help in the prevention of childhood obesity.     

Barley yield and weed development as affected by crop sequence and tillage systems in a semi‐arid environment

Abstract

In order to monitor barley and weed development on a loamy sand soil subjected to different agronomic practices, field experiments were conducted for three growing seasons (1992–95) in a semi‐arid agrosystem in central Spain. For eight years, independent plots were managed with three crop sequences: barley (Hordeum vulgare L.)?vetch (Vicia sativa L.); barley? sunflower (Helianthus annuus L.); and a barley monoculture. In all cases, two tillage systems were implemented: no‐tillage and conventional tillage. In the years with standard rainfall (400 mm) an improvement in growth‐related cultivation variables and yield components of barley were observed in plots under barley?vetch rotation and/or conventional tillage. In drier conditions (<350 mm) the growth rate, crop yield and yield components of barley tended to improve under the no‐tillage system. Barley?vetch rotation and/or conventional tillage increased nitrate‐nitrogen (NO₃‐N) content in barley plants. Similar results were found for the concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg). In addition, the plots under crop rotation showed a weed biomass with a high concentration of N, K, and Ca in comparison with plots under monoculture. The lack of spring herbicide treatment in the no‐tillage plots led to a 3‐fold increase in weed density compared with the plots under conventional tillage.     

Selenium in agriculture: a nutrient or contaminant for crops?

Selenium (Se) is an essential nutrient for animals, humans, and microorganisms, but its role in the plants needs further exploration. It is considered beneficial at low levels, but is toxic at higher levels, and there is a fine boundary between these concentrations. Generally, Se levels less than 1 mg kg^?1 have been found to be beneficial for the plants while higher levels cause toxicity in most of the agricultural crops. At low concentrations, Se can act as a plant growth regulator, antioxidant, anti-senescent, abiotic stress modulator, and defensive molecule against pathogens in plants. At higher concentrations, plants show various toxic symptoms, which include stunting of growth, chlorosis, withering, and drying of leaves, decreased protein synthesis premature and even death of the plant. The roles of selenium as enhancer and inhibitor of plant growth in various agricultural crops are discussed here with recent updates. Biofortification of some crops with Se using agronomic and genetic approaches is being explored to cultivate them in the regions having Se-deficiency in foods. Strategies of phytoremediation of Se in hyperaccumulators and transgenic plants overexpressing enzyme/proteins to increase Se tolerance are also described.     

The Cuban homegarden ‘conuco’: a perspective environment for evolution and in situ conservation of plant genetic resources

Summary Cuban homegardens are called conucos. On the basis of new case studies additional information is provided about these conucos, their history, composition and importance. They and other gardens of similar type are characterized as suitable environment for in situ conservation and for the continuation of evolutionary processes.     

Assessing arbuscular mycorrhizal plant metal uptake and soil metal bioavailability among ‘dwarf’ sunflowers in a stratified compartmental growth environment

Using the micronutrient zinc (Zn) as a metal contaminant, a stratified compartmental pot greenhouse experiment involving ‘dwarf’ sunflowers and an arbuscular mycorrhizal (AM) fungus was designed to assess the role of AM symbiosis toward plant growth and metal uptake, and to differentiate its impact toward edaphic parameters across different soil strata. Consistent with previous hypotheses, AM plants contained up to 40% lower metal concentrations in their shoots than non-AM plants, particularly at the highest soil Zn levels (200 and 400 mg Zn kg^?1 dry soil); this, corresponding with an enhanced growth status among AM plants. Upon assessing the soil Zn concentrations and pH, AM treatments also tended to have higher soil Zn levels and more alkaline conditions compared to non-AM treatments. This was found especially in the topmost soil stratum where AM root colonization was deemed most active as evidenced by a higher frequency of extraradical hyphae, vesicles, and arbuscules. Together, these effects were putatively linked to the AM-induced mechanism of metal biosorption known to modulate soil nutrient bioavailability and even delay the onset of metal toxicity.     

How well does a botanical garden collection of a rare palm capture the genetic variation in a wild population?

Conservation is increasingly central to the botanic garden mission. Living plant collections are important components of conservation. Critical evaluation of living conservation collections with population genetic analysis can directly inform ex situ conservation strategy. Here, we quantify the degree of genetic variation captured through a population-based collection protocol, and explore optimal sampling for ex situ conservation. An extensive living collection derived from one population of Leucothrinax morrisii (Arecaceae) provided a model system. We compared 58 specimens from the ex situ collection with 100 individuals from throughout the parent population via 6 ISSR loci. Random bootstrapped resamples of the data were made to model differently structured ex situ collections. Mean diversity (He) differed little between the collection (0.204) and the population (0.216), and genetic distance (D) was very close (0.036). Very few private alleles were found between the collection and the population. Allelic capture, as measured by percent of private alleles, was greater than 94%. Resampled collections of different sizes captured from 48% to 94% of alleles. Pairwise comparison of bootstrapped resamples suggests that increasing the representation of half-sibling groups does not significantly increase allele capture. Increase in allele capture with increasing sample size is greatest at low resample sizes, and showed diminishing returns as resample size increased. No appreciable increase in allele capture was gained through maintaining different half-sibling groups. These data inform sampling for ex situ conservation purposes, and recommend sample sizes of at least 15 individuals, with the upper limit based on resources.     

Longitudinal patterns in bird reporting rates in a threatened ecosystem: Is change regionally consistent?

Work in many parts of the world has discussed the decline of biodiversity in regions dominated by agriculture. We report the results of a major study documenting the longitudinal profiles of birds between 1998 and 2009 within 66 patches of temperate woodland in a heavily cleared and grazed agricultural region of south-eastern Australia. Many researchers have forecast the loss of bird biota from this region and others that also were formerly dominated by temperate woodland.We had sufficient high quality data to analyse the longitudinal profiles of reporting rates for 76 of the 116 individual bird species recorded in our 12-year study. Unexpectedly, only four of the 76 species analysed (5.6%) exhibited a significant negative linear decrease in reporting rate. More surprisingly, 32 (42.1%) exhibited a significant positive linear increase in reporting rate, including several taxa of conservation concern. These increases occurred despite a series of below-average rainfall years. Reporting rates were too low to formally model long-term trends in some other bird species widely considered to be of conservation concern such as the Diamond Firetail (Stagonopleura guttata) and Speckled Warbler (Chthonicola sagittata).Many authors have used functional (and other) groups to forecast bird species likely to be lost from Australia’s temperate woodlands. However, we found no clear links between life history attributes and long-term trend patterns of species.Our findings contrast with recent findings from other temperate woodland-dominated regions in eastern Australia where losses in bird populations have been documented. However, they parallel other investigations such as in central New South Wales. These similarities among, and differences between, studies suggest regional differences in temporal patterns in bird population dynamics. Many of the observed changes in reporting rates were positive and they provide hope that forecast future losses of a large proportion of existing temperate woodland bird assemblages in south-eastern Australia may not be realised uniformly in all regions.     

Is overweight a risk factor for wheezing in pre-school children? A study in 14 Brazilian communities

OBJECTIVE: To evaluate the association between overweight and wheezing in pre-school children in 14 small Brazilian communities. METHODS: Cross-sectional epidemiological study, conducted between 2001 and 2002. A sample of 3453 children under 5 years of age was taken from nine communities in the state of Bahia and five in the state of S?o Paulo. Data on housing, family and children were obtained by applying structured questionnaires in loco. Weight and height for each child were also measured. The association between wheezing and overweight was assessed by unconditional logistic multivariate regression models. RESULTS: Overweight children had a greater frequency of wheezing and an odds ratio of 2.57 (95% confidence interval 1.51-4.37) was estimated after controlling for several potential confounding variables. The magnitude of the risk was not affected by several different model specifications. CONCLUSION: Excess weight is associated with increased risk for wheezing in this population of children below 5 years of age.     

Reactions to soil acidification in microarthropods: Is competition a key factor?

Summary Acidification of raw humus soil in coniferous forest areas leads to characteristic changes in the microarthropod community. Certain species are calciophilic and decrease in abundance, while others are acidophilic and increase in abundance. The simplest explanation for these changes is that population levels are directly related to soil pH. This hypothesis was tested by growing small populations of selected species in monoculture at different pH levels. Three acidophilic species were tested, the collembolan Mesaphorura yosii, the oribatid mite Nothrus silvestris, and the astigmatid mite Schwiebea cf. lebruni. A slightly calciophilic collembolan, Isotomiella minor, was also included. For all species, population growth was lowest in acidified raw humus. Even acidophilic species seem to have an optimum at a high pH. It is assumed that their success in low-pH soils is due to their ability to compete under these conditions. Competition may be a key factor in microarthropod reactions to soil acidification.Dedicated to the late Prof. Dr. W. Kühnelt