Changes in species richness and composition in European acidic grasslands over the past 70 years: the contribution of cumulative atmospheric nitrogen deposition

Our study investigates the negative impact of nitrogen (N) deposition on species richness in acidic grasslands, based on a temporal comparison of vegetation data spanning a period of almost 70 years. We compiled a large data base of plots assigned to the Violion caninae grassland type, composed of managed, but unfertilized semi-natural grasslands on nutrient-poor, acidic soils. In total 1114 plots, mainly from Great Britain, the Netherlands and Germany, were compiled, dating back to 1939. Environmental site information included geographical and soil (mean Ellenberg values) variables as well as estimates of cumulative N and sulphur (S) deposition since 1939. Statistical analyses were carried out separately for the data subsets from the three regions. In all regions, the vegetation differentiation was mainly related to soil acidity and nutrient availability, as well as to the year of sampling and the cumulative amounts of N and S deposition. Plot-species richness of vascular plants and bryophytes (analysed for Great Britain only) decreased with time and analyses suggest these are affected by various factors, notably soil pH, but also latitude and cumulative N deposition. The latter explained more of the variation in species number than the year of sampling and cumulative S deposition, which supports the interpretation that the decline in species richness is mainly caused by increasing N availability and less by altered management and soil acidification. For Great Britain and Germany, cumulative N deposition showed a strong negative relationship with several biodiversity measures, especially the proportion of dicots, whereas it was positively related to the proportion of grass species. In general, our results give temporal evidence for the negative effect of N deposition on species richness in semi-natural vegetation.     

Inter‐regional comparison of land‐use effects on stream metabolism

1. Rates of whole‐system metabolism (production and respiration) are fundamental indicators of ecosystem structure and function. Although first‐order, proximal controls are well understood, assessments of the interactions between proximal controls and distal controls, such as land use and geographic region, are lacking. Thus, the influence of land use on stream metabolism across geographic regions is unknown. Further, there is limited understanding of how land use may alter variability in ecosystem metabolism across regions. 2. Stream metabolism was measured in nine streams in each of eight regions (n = 72) across the United States and Puerto Rico. In each region, three streams were selected from a range of three land uses: agriculturally influenced, urban‐influenced, and reference streams. Stream metabolism was estimated from diel changes in dissolved oxygen concentrations in each stream reach with correction for reaeration and groundwater input. 3. Gross primary production (GPP) was highest in regions with little riparian vegetation (sagebrush steppe in Wyoming, desert shrub in Arizona/New Mexico) and lowest in forested regions (North Carolina, Oregon). In contrast, ecosystem respiration (ER) varied both within and among regions. Reference streams had significantly lower rates of GPP than urban or agriculturally influenced streams. 4. GPP was positively correlated with photosynthetically active radiation and autotrophic biomass. Multiple regression models compared using Akaike’s information criterion (AIC) indicated GPP increased with water column ammonium and the fraction of the catchment in urban and reference land‐use categories. Multiple regression models also identified velocity, temperature, nitrate, ammonium, dissolved organic carbon, GPP, coarse benthic organic matter, fine benthic organic matter and the fraction of all land‐use categories in the catchment as regulators of ER. 5. Structural equation modelling indicated significant distal as well as proximal control pathways including a direct effect of land‐use on GPP as well as SRP, DIN, and PAR effects on GPP; GPP effects on autotrophic biomass, organic matter, and ER; and organic matter effects on ER. 6. Overall, consideration of the data separated by land‐use categories showed reduced inter‐regional variability in rates of metabolism, indicating that the influence of agricultural and urban land use can obscure regional differences in stream metabolism.     

THE EFFECTS OF SODIUM CHLORIDE ON HIGHER PLANTS

(1) This review concentrates on the effect of sodium chloride on the growth of higher plants, being primarily concerned with relatively high concentrations i.e. 50 mmol 1^-1 and above, though something is also said about those instances when sodium acts as a micronutrient. Emphasis is placed on particular species or genera for which enough information is available to discuss possible mechanisms. (2) Trace amounts of sodium are required for the growth of plants using the C₄ pathway of carbon fixation and may also be important in plants with Crassulacean acid metabolism. (3) The increased growth of Beta vulgaris brought about by sodium chloride can in part be explained by a sparing effect on potassium. However, growth is still increased when sufficient potassium is available. Complementary studies with rubidium indicate that the hormone balance in the plant may be changed. Sodium chloride also increases the level of sucrose in storage roots and allows beet plants to withstand water stress more readily, possibly by increased turgor pressure. (4) Sodium chloride increases production of dry matter in C₄ species of Atriplex under conditions of low relative humidity because water loss is reduced and photo-synthesis hardly affected. (5) Succulence in many plants is stimulated by salinity. The essential basis of the phenomenon is an increased water potential gradient between the leaf and the external medium. In some instances, it is the accumulation of chloride which is important; in others it is the accumulation of cations, when potassium can be as effective as sodium. (6) Salinity reduces the final area achieved by growing leaves. Most of the studies have been made on Phaseolus vulgaris and an important early event is the reduction in the rate of expansion of the epidermal cells and this may be accompanied by a decrease in their number. Reduction of epidermal cell size is a result of water stress; sodium chloride may directly affect cell division, though water stress cannot be ruled out. Whether salinity brings about inhibition of cell division depends upon the calcium content of the medium – a high content is accompanied solely by a reduction in epidermal cell size. (7) Hormones, as yet unspecified, may play an important part in response of a growing leaf to salinity. However, there is no evidence that sodium chloride per se has an effect on hormone balance within the plant. So far, any measured changes in levels of specific hormones can be ascribed to the osmotic effects of the saline medium. (8) Two estimates by flux analysis of cytoplasmic concentration of sodium in plants growing in conditions of high salinity give a value of around 150 mmol 1^-1. There is no similar information for chloride. Other techniques (histochemistry and X-ray micro-probe analysis) give questionable information. (9) There is now extensive information to show that enzymes of halophytes (other than ATPases) do not differ significantly from those of other higher plants with respect to their sensitivity in vitro to sodium chloride. There is a need for further work with respect to the activity of enzymes in the presence of those metabolites which have the highest cytoplasmic concentration. (10) Sodium-stimulated ATPases have been isolated from plant cells but their distribution amongst higher plants is restricted. (11) There are a number of reports of changed metabolism brought about by saline treatments but it is not clear how far the effects of sodium chloride and water stress are confounded. (12) Sodium appears to increase the sucrose levels in sugar beet by an inhibitory effect on product starch-granule-bound ADP-glucose starch synthase. (13) Reversal of a sodium pump located at the plasmalemma might have an effect on cell turgor. (14) Sodium (like other monovalent cations) causes loss of materials from plant cells, possibly through an effect on carrier proteins; calcium prevents this from happening. Calcium also allows plants to grow better in saline conditions by a depression of sodium uptake by and transport within the plant. The properties and composition of the membranes of mesophytes and halophytes need to be compared. (15) A saline medium exerts a major effect on plant growth through water stress to which a halophyte must adapt. As well as this, the cytoplasmic concentration of sodium chloride must be kept lower than the total cellular concentration of the salt. Unless this happens, it is likely that enzymic activity will be reduced due, in some instances, to an unspecific effect of a high concentration of monovalent cations and/or chloride and in other instances to competition between sodium and other cations, specifically potassium, for activation sites on enzymes, e.g. pyruvate kinase. (16) Further work is required to separate the osmotic effects from the specific effect of sodium chloride after it has entered the plant. As well as this, it has become clear that more information is needed about the mineral nutrition of halophytes.     

Effects of Radiotransmitter Necklaces on Behaviors of Adult Male Western Burrowing Owls

Abstract: We studied the behavioral effects of necklace-style radiotransmitters on breeding male western burrowing owls (Athene cunicularia hypugaea) in 2 areas of northwestern Texas, USA, in 2004 and 2005. We tested the hypothesis that transmittered owls would spend time interacting with their necklaces and as a result spend less time in vigilance and resting activities than would nontransmittered owls. Nontransmittered owls (n = 6) spent significantly more time being vigilant (P = 0.007) than did transmittered owls (n = 3) in 2004, who spent significant amounts of time interacting with their necklaces. In 2005, behaviors of transmittered owls (n = 8) were significantly different (P < 0.001) from control individuals (n = 4), but behaviors did not vary consistently by treatment period (prenecklace vs. necklace vs. postnecklace periods). Behavioral activity budgets varied considerably among individuals. Although the owls spent a significant amount of time interacting with their necklaces, they appeared to habituate to the presence of the transmitters within a relatively short period (<1week), and necklaces did not affect survivorship or fitness in the short-term.     

Mini-exon Gene Sequences Define Six Groups within the Genus Crithidia

ABSTRACT. To develop molecular markers for lower trypanosmatids, we have examined the mini-exon gene repeats of 17 isolates that were classified as Crithidia by traditional methods. Representative repeats were amplified by polymerase chain reaction and the amplification products were cloned and used as hybridization probes against genomic DNA. Six hybridization groups of Crithidia were defined on the basis of the DNA blotting experiments. The three endosymbiont-bearing species ( C. deanei, C. desouzai and C. oncopelti ) and C. acanthocephali each belonged to single-member hybridization groups, while the C. fasciculata group contained additional named and undesignated species. The Crithidia lucilae thermophila probe hybridized to multiple undesignated isolates. The DNA sequence of the cloned products revealed that the specificity of the hybridization probes was due to substantial differences in the intron and the non-transcribed spacer regions. These data indicate substantial heterogeneity within the mini-exon gene locus of the taxon Crithidia .     

Life history plasticity of Nemoura trispinosa (Plecoptera: Nemouridae) along a permanent-temporary water habitat gradient

1. The life history of the small herbivorous stonefly Nemoura trispinosa Claassen was studied in a variety of small springs in southern Ontario, Canada. Nymphs generally were able to tolerate a wide range of environmental conditions and were found in 78% of habitats sampled, although population densities differed markedly. 2. Life-cycle patterns varied from a univoltine, slow seasonal type to a univoltine, fast seasonal type with extended egg development. In one, highly stable, spring the life cycle was semivoltine. Inter-year variation was studied for 5 years in one spring and was found to be low relative to among-spring variation. 3. Differences in the life history traits of N. trispinosa populations from our spring series were most probably an expression of phenotypic plasticity rather than of genetic differentiation. 4. Maximum annual water temperature was the factor most influential on nymphal growth rate (non-linear relationship), whereas range in generation time was related to the degree of habitat permanence.     

Phenotypic Variation and Systemic Cancer in the FAMMM Syndrome

Familial atypical multiple mole melanoma (FAMMM) syndrome, a cancer-associated genodermatosis, is a dominantly inherited heterogeneous disorder with variable expressivity of both its cutaneous and cancer phenotypes. By using a verified historical review technique of cancer documentation (idout patient health records, pathology reports/slides, autopsy reports/slides, and death certificates) of all anatomic sites in all members of a modified nuclear pedigree (first-degree relatives plus maternal and paternal grandparents, aunts, and uncles) over several generations, we showed that the FAMMM syndrome is similar to the majority of autosomal dominant inherited cancer-associated genodermatoses and has excessive risk for cancer of multiple anatomic sites. With respect to the FAMMM syndrome, these cancers involved the breast, respiratory tract, gastrointestinal system, the eye (intraocular melanoma), and the lymphatic system. These FAMMM pedigrees showed some of the following distinctive characteristics of hereditary cancer: 1) integral patterns of cancer within and between pedigrees; 2) early age of onset of cancer; 3) prolonged survival of some pedigree members with cancer; and 4) an excess of multiple primary melanomas and cancers of variable anatomic sites. The presence of these features indicates that these cancers of variable anatomic sites may be etiologically associated with the FAMMM syndrome. Heterogeneity should be investigated in FAMMM pedigrees with attention to consistent differences in size and distribution of atypical lesions, age at cancer onset, and pattern of tumor occurrences. The occurrence of FAMMM pedigrees in the general population or among pedigrees of probands with atypical nevi is not known. The occurrence of systemic cancers in these FAMMM pedigrees requires the development of cancer surveillance programs that are specifically modified to the particular cancer pattern of each pedigree.