Effects of ultraviolet radiation on litter decomposition depend on precipitation and litter chemistry in a shortgrass steppe ecosystem

We examined the effect of altered levels of ultraviolet (UV) radiation (280–400 nm) and different amounts of precipitation on the decomposition rates of litter of contrasting carbon to nitrogen ratio (C : N) in a 3-year field experiment in a shortgrass steppe (SGS) ecosystem. UV radiation was either blocked or passed under clear plastic tents where precipitation was applied to simulate a very dry or very wet year. These treatments minimized or maximized the abiotic component (UV) or the biotic component (biological activity of decomposer organisms) of decomposition to assess potential interactions between the two. Initial litter chemistry varied in response to having been grown under ambient or elevated atmospheric CO₂ concentrations. While precipitation and litter chemistry were the most important drivers in decomposition in this system, UV radiation increased decomposition rates under dry conditions in litter with higher C : N ratios. Exposure to UV radiation slightly increased the amount of holocellulose that was lost from the litter. UV exposure did not affect the decomposition of the lignin fraction. Increased decomposition with UV radiation was accompanied by a decrease in N immobilization over the summer months. These results suggest that the effects of UV radiation on decomposition rates may be primarily abiotic, caused by direct photochemical degradation of the litter. Our results demonstrate that the role of UV radiation in litter decomposition in semiarid systems depends on the aridity of the system and the chemistry of the litter.     

The genus Coperonus Wilson, 1989 (Crustacea: Isopoda: Asellota: Munnopsidae)

This paper presents a revision of the natatory isopod genus Coperonus (Munnopsidae, Lipomerinae). A key to identify all seven known species of the genus is provided. Four new species are described and Coperonus frigida (Vanhöffen, 1914) is redescribed on the basis of the type material. The biogeography of Coperonus is described.
In dieser Arbeit wird die Gattung Coperonus (Munnopsidae, Lipomerinae), deren Vertreter sich durch gute Schwimmfähigkeit auszeichnen, revidiert. Ein Bestimmungsschlüssel für alle sieben bisher bekannten Arten ist in der Arbeit enthalten. Es werden vier neue Arten beschrieben und Coperonus frigida (Vanhöffen, 1914) wird anhand des Typenmaterials nachbeschrieben. Auβerdem wird in der Arbeit die Biogeographie von Coperonus dargestellt.     

New Asellota from the Antarctic deep sea (Crustacea, Isopoda, Asellota), with descriptions of two new genera

Two new genera, Reductosoma gen.n. (Desmosomatidae) and Desmostylis gen.n. (Desmosomatidae), and five new species are described from the Maud Rise and the Gunnerus Ridgc, Antarctica. Two new species of the Desmosomatidae (Eugerdellatinae and Desmosomatinae) are described: Reduetosoma gunnera gen. et sp.n. and Desmosoma hesslera sp.n.; one species of the Munnopsidae (Eurycopinae), Disconectes colernuni sp.n.; and two species of the Macrostylidae from the Antarctic deep sea, Desmostylis obscurus gen. et sp.n. and Macrostylis sarsi sp.n. Comments on the phylogeny and zoogeography are given.     

Changes in Agriculture and Abundance of Snow Geese Affect Carrying Capacity of Sandhill Cranes in Nebraska

ABSTRACT The central Platte River valley (CPRV) in Nebraska, USA, is a key spring-staging area for approximately 80% of the midcontinent population of sandhill cranes (Grus canadensis; hereafter cranes). Evidence that staging cranes acquired less lipid reserves during the 1990s compared to the late 1970s and increases in use of the CPRV by snow geese (Chen caerulescens) prompted us to investigate availability of waste corn and quantify spatial and temporal patterns of crane and waterfowl use of the region. We developed a predictive model to assess impacts of changes in availability of corn and snow goose abundance under past, present, and potential future conditions. Over a hypothetical 60-day staging period, predicted energy demand of cranes and waterfowl increased 87% between the late 1970s and 1998–2007, primarily because peak abundances of snow geese increased by 650,000 and cranes by 110,000. Compared to spring 1979, corn available when cranes arrived was 20% less in 1998 and 68% less in 1999; consequently, the area of cornfields required to meet crane needs increased from 14,464 ha in 1979 to 32,751 ha in 1998 and 90,559 ha in 1999. Using a pooled estimate of 88 kg/ha from springs 1998–1999 and 2005–2007, the area of cornfields needed to supply food requirements of cranes and waterfowl increased to 65,587 ha and was greatest in the eastern region of the CPRV, where an estimated 54% of cranes, 47% of Canada geese (Branta canadensis), 45% of greater white-fronted geese (Anser albifrons), and 46% of snow geese occurred during ground surveys. We estimated that a future reduction of 25% in available corn or cornfields would increase daily foraging flight distances of cranes by 27–38%. Crane use and ability of cranes to store lipid reserves in the CPRV could be reduced substantially if flight distance required to locate adequate corn exceeded a physiological maximum distance cranes could fly in search of food. Options to increase carrying capacity for cranes include increasing accessibility of cornfields by restoring degraded river channels to disperse roosting cranes and increasing wetland availability in the Rainwater Basin to attract snow geese using the CPRV.     

Quantum relations in photoreactivation of Colpidium

1. The amount of visible or long ultraviolet light (UV) required to photoreactivate Colpidium colpoda injured with known dosages of short UV (2654 A) was determined. 2. The effect of the short UV was tested by the delay in division of exposed animals compared to controls. Photoreactivation was tested by the effect of postillumination on the delay of division of treated colpidia compared to controls. 3. Colpidia were used in two physiological states: well fed and starved in balanced medium for 48 hours. The latter are much more sensitive to short UV although less susceptible of photoreactivation. 4. Photoreactivation occurred over the entire span from 3350 A to 4350 A for the well fed colpidia, from 3130 A to 5490 (green) for starved colpidia. 5. The photoreactivating effect of a single quantum of blue (4350 A) or long UV (3660 A) delivered per quantum of 2654 A used to injure colpidia was too slight to be considered significant. The effect of 10 quanta was usually more pronounced, but only after 100 quanta had been delivered was the photoreactivation nearly maximal for well fed colpidia. 6. The quantum requirement for maximal photoreactivation of the starved animals was greater at all wave lengths tried: 3660, 4050, 4350, and 5460 A being of the order of 800 incident quanta per incident quantum of 2654 A. 7. The transmission of UV(2654 A), blue, yellow, and red light by a suspension of colpidia was determined. 8. Large dosages of blue, violet, or long UV were slightly injurious to starved colpidia. In a few cases large dosages of 3660 A killed starved colpidia, especially after a non-lethal dose of short UV(2654 A). 9. Photoreactivation seems to be a balance between the slight injurious effect produced by the visible light or UV of long wave lengths and the injury produced by short wave length UV. 10. Possible reasons for the large number of quanta of photoreactivating light required per quantum of short UV are discussed.     

Accumulation of Anthocyanins and Flavones during Bud and Flower Development in Campanula isophylla Moretti

In the blue flowers of Italian bellflower (Campanula isophyllaMoretti), the formation of anthocyanins progresses from simpleunacylated anthocyanins, delphinidin 3–glucoside and bisdeacylplatyconin,through a series of progressively-acylated and glycosylatedcompounds, including diacylated violdelphin and monodeacylcampanin,to the triacylated campanin. In this study, anthocyanin andflavone contents were very low in buds until a few days beforeanthesis, after which they increased rapidly. Bisdeacylplatyconinand luteolin 7-O -glucoside peaked 2 d before anthesis. Themore complicated luteolin glucosides peaked 2 d after anthesis,slightly preceding monodeacylcampanin and campanin. Total anthocyanincontent peaked approx. 5 d after anthesis followed by a slowdecline. The highest total flavone content was reached at anthesis,after which it remained almost constant, but with some changesin the proportion of individual compounds. In the investigationtwo phenotypes were used, types B and C. Acylation of monodeacylcampaninto campanin is blocked in type B, but not in type C plants.Conversion of bisdeacylplatyconin into acylated anthocyaninswas shown to be slower in type C than in type B plants. Campanula isophylla ; Campanulaceae; Italian bellflower; anthocyanin; flavone; biosynthesis; flower development     

Empirical geographic modeling of switchgrass yields in the United States

Switchgrass (Panicum virgatum L.) is a perennial grass native to the United States that has been studied as a sustainable source of biomass fuel. Although many field‐scale studies have examined the potential of this grass as a bioenergy crop, these studies have not been integrated. In this study, we present an empirical model for switchgrass yield and use this model to predict yield for the conterminous United States. We added environmental covariates to assembled yield data from field trials based on geographic location. We developed empirical models based on these data. The resulting empirical models, which account for spatial autocorrelation in the field data, provide the ability to estimate yield from factors associated with climate, soils, and management for both lowland and upland varieties of switchgrass. Yields of both ecotypes showed quadratic responses to temperature, increased with precipitation and minimum winter temperature, and decreased with stand age. Only the upland ecotype showed a positive response to our index of soil wetness and only the lowland ecotype showed a positive response to fertilizer. We view this empirical modeling effort, not as an alternative to mechanistic plant‐growth modeling, but rather as a first step in the process of functional validation that will compare patterns produced by the models with those found in data. For the upland variety, the correlation between measured yields and yields predicted by empirical models was 0.62 for the training subset and 0.58 for the test subset. For the lowland variety, the correlation was 0.46 for the training subset and 0.19 for the test subset. Because considerable variation in yield remains unexplained, it will be important in the future to characterize spatial and local sources of uncertainty associated with empirical yield estimates.