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Aim: The controls of gross radiation use efficiency (RUE), the ratio between gross primary productivity (GPP) and the radiation intercepted by terrestrial vegetation, and its spatial and temporal variation are not yet fully understood. Our objectives were to analyse and synthesize the spatial variability of GPP and the spatial and temporal variability of RUE and its climatic controls for a wide range of vegetation types. Location: A global range of sites from tundra to rain forest. Methods: We analysed a global dataset on photosynthetic uptake and climatic variables from 35 eddy covariance (EC) flux sites spanning between 100 and 2200 mm mean annual rainfall and between -13 and 26°C mean annual temperature. RUE was calculated from the data provided by EC flux sites and remote sensing (MODIS). Results: Rainfall and actual evapotranspiration (AET) positively influenced the spatial variation of annual GPP, whereas temperature only influenced the GPP of forests. Annual and maximum RUE were also positively controlled primarily by annual rainfall. The main control parameters of the growth season variation of gross RUE varied for each ecosystem type. Overall, the ratio between actual and potential evapotranspiration and a surrogate for the energy balance explained a greater proportion of the seasonal variation of RUE than the vapour pressure deficit (VPD), AET and precipitation. Temperature was important for determining the intra-annual variability of the RUE at the coldest energy-limited sites. Main conclusions: Our analysis supports the idea that the annual functioning of vegetation that is adapted to its local environment is more constrained by water availability than by temperature. The spatial variability of annual and maximum RUE can be largely explained by annual precipitation, more than by vegetation type. The intra-annual variation of RUE was mainly linked to the energy balance and water availability along the climatic gradient. Furthermore, we showed that intra-annual variation of gross RUE is only weakly influenced by VPD and temperature, contrary to what is frequently assumed. Our results provide a better understanding of the spatial and temporal controls of the RUE and thus could lead to a better estimation of ecosystem carbon fixation and better modelling. © 2009 Blackwell Publishing Ltd.

To purchase or authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1365-2745.2007.01282.x Byline: ROY H. A. VAN GRUNSVEN (*[dagger]), WIM H. VAN DER PUTTEN ([double dagger]s.), T. MARTIJN BEZEMER ([double dagger]s.[paragraph]), WIL L. M. TAMIS (**), FRANK BERENDSE ([dagger]), ELMAR M. VEENENDAAL (1) Keywords: climate envelope; distribution; ecosystem functioning; enemy release; global change; invasive plants; pathogens; range shift; soil; thermophylic Abstract: Summary As a result of global warming, species may spread into previously cool regions. Species that disperse faster than their natural enemies may become released from top-down control. We investigated whether plants originating from southern Europe and recently established in north-western Europe experience less soil pathogen effects than native species. We selected three plant species originating from southern Europe that have immigrated into the Netherlands and three similar native Dutch species. All six plant species were grown in sterilized soils with a soil inoculum collected from the rhizospheres of field populations. As a control we grew a series of all six plant species with a sterilized rhizosphere inoculum. We harvested the plants, added the conditioned soil to sterilized soil and grew a second generation of all six plant species in order to test for each plant pair feedback effects from the conditioned soil communities to conspecifics and heterospecifics. The effect of the soil community is dependent on plant species, and is dependent on soil fertility in only one of the three pairs. Soil conditioning caused less biomass reduction to exotic plant species than to native species, suggesting that exotic immigrants are less exposed to soil pathogens than similar native plant species. Our results suggest that plant species that expand their range as a result of climate change may become released from soil pathogenic activity. Whether the exotics are released from soil pathogens, or whether they experience enhanced benefit from mutualistic symbionts remains to be studied. We conclude that range expansion may result in enemy release patterns that are similar to artificially introduced invasive exotic plant species. The escape from enemies through range shifts changes key biotic interactions and complicates predictions of future distribution and dominance. Author Affiliation: ([dagger])Nature Conservation and Plant Ecology Group, Wageningen University and Research Centre, Droevendaalsesteeg 3a, 6708 PB Wageningen, The Netherlands, ([double dagger])Netherlands Institute of Ecology (NIOO-KNAW), Centre for Terrestrial Ecology, Heteren, The Netherlands, (s.)Laboratory of Nematology, Wageningen University and Research Centre, PO Box 8123, 6700 ES Wageningen, The Netherlands, (s.)Laboratory of Entomology, Wageningen University and Research Centre, PO Box 8031, 6700 EH Wageningen,The Netherlands, (**)Nationaal Herbarium Nederland/Leiden University Branch, PO Box 9514, 2300 RA Leiden, The Netherlands Article History: Received 24 January 2007; accepted 13 June 2007Handling Editor: Marcel van der Heijden Article note: (*) Author to whom correspondence should be addresed: Roy H. A. van Grunsven. Tel.: +31 317 483659. Fax: +31 317 419000. E-mail: royvangrunsven@gmail.com.

Background: Forest and savanna vegetation in the zone of transition (ZOT) contain distinct woody species due to fire, drought and herbivory barriers that constrain forest species from invading adjacent savannas and vice-versa. Little is known if these barriers cause divergence in species composition between the overstorey and understorey strata in these vegetation types. Aim: We investigated woody species composition across overstorey and understorey strata in the ZOT and explored the relationship between soil fertility and species composition patterns. Methods: We sampled overstorey and understorey woody species and determined soil nutrient concentrations in twenty-five 20 m × 20 m plots in a ZOT in Ghana. Results: Forest and savanna species dominated the overstorey and understorey of their respective environments. However, species composition was decoupled between the overstorey and understorey strata in both forest and savanna vegetations. Few savanna and forest species had individuals co-occurring in both overstorey and understorey such that ~65% of the dominant species was limited to only one stratum. Soil fertility had little effect on these patterns. Conclusion: These patterns indicate that, forest and savanna species face significant recruitment barriers in their respective environments, suggesting that requirements for juvenile establishment may differ from recruitments to the canopy layer. [ABSTRACT FROM AUTHOR]

Levels of artificial night lighting are increasing rapidly worldwide, subjecting nocturnal organisms to a major change in their environment. Many moth species are strongly attracted to sources of artificial night lighting, with potentially severe, yet poorly studied, consequences for development, reproduction and inter/intra-specific interactions., Here, we present results of a field-based experiment where we tested effects of various types of artificial lighting on mating in the winter moth ( Operophtera brumata, Lepidoptera: Geometridae). We illuminated trunks of oak trees with green, white, red or no artificial LED light at night, and caught female O. brumata on these trunks using funnel traps. The females were dissected to check for the presence of a spermatophore, a sperm package that is delivered by males to females during mating., We found a strong reduction in the number of females on the illuminated trunks, indicating artificial light inhibition of activity. Furthermore, artificial light inhibited mating: 53% of females caught on non-illuminated trunks had mated, whereas only 13%, 16% and 28% of the females that were caught on green, white and red light illuminated trunks had mated respectively., A second experiment showed that artificial night lighting reduced the number of males that were attracted to a synthetic O. brumata pheromone lure. This effect was strongest under red light and mildest under green light., This study provides, for the first time, field-based evidence that artificial night lighting disrupts reproductive behaviour of moths, and that reducing short wavelength radiation only partly mitigates these negative effects. [ABSTRACT FROM AUTHOR]

Background:As a consequence of climate warming, many organisms are shifting their range towards higher latitudes and altitudes. As not all do so at the same speed, this may disrupt biotic interaction. Release from natural enemies through range expansion can result in invasiveness, whereas loss of mutualists can reduce plant vigour and fitness. One of the most important groups of plant symbiotic mutualists is the arbuscular mycorrhizal fungi (AMF). Aims:We used greenhouse experiments to test whetherTragopogon dubius, a species that has recently expanded its range northward and colonised the Netherlands, is able to associate with the same AMF as the native congenerT. pratensis. Methods:In soils collected from four locations in the new range ofT. dubiuswe compared the density of infective AMF propagules associating with both plant species, as well as AMF colonisation of the roots. The AMF community structure in the roots of these species was also analysed using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). Results:Tragopogon dubiusandT. pratensisdid not differ in any of these characteristics. Conclusions:We therefore conclude that the range-shiftingT. dubiusis as effective in the formation of mycorrhiza as the native congener. [ABSTRACT FROM PUBLISHER]

The article presents a study on the Heath trap method with six watt actinic light source to attract nocturnal insect moths. Topics discussed include comparison-based on light trap between moth family Erebidae, Geometridae and Noctuidae, analysis of moths recapture by linear model of binomial distribution and effect of environmental condition factors such as distance, temperature and moon phase on recapture of moths.

Climate warming causes range shifts of many species toward higher latitudes and altitudes. However, range shifts of host species do not necessarily proceed at the same rates as those of their enemies and symbionts. Here, we examined how a range shifting plant species performs in soil from its original range in comparison with soil from the expansion range. Tragopogon dubius is currently expanding from southern into north-western Europe and we examined how this plant species responds to soil communities from its original and expansion ranges. We compared the performance of T. dubius with that of the closely related Tragopogon pratensis, which has a natural occurrence along the entire latitudinal gradient. Inoculation with the rhizosphere soil from T. dubius populations of the original range had a more negative effect on plant biomass production than inoculation with rhizosphere soil from the expansion range. Interestingly, the nonrange expander T. pratensis experienced a net negative soil effect throughout this entire range. The effects observed in this species pair may be due to release from soil born enemies or accumulation of beneficial soil born organisms. If this phenomenon applies broadly to other species, then range expansion may enable plants species to show enhanced performance. [ABSTRACT FROM AUTHOR]

We investigated differences in physiological and morphological traits between the tall and short forms of mopane (Colophospermum mopane (Kirk ex Benth.) Kirk ex J. Léonard) trees growing near Maun, Botswana on a Kalahari sandveld overlying an impermeable calcrete duricrust. We sought to determine if differences between the two physiognomic types are attributable to the way they exploit available soil water. The tall form, which was located on deeper soil than the short form (5.5 versus 1.6 m), had a lower leaf:fine root biomass ratio (1:20 versus 1:6), but a similar leaf area index (0.9-1.0). Leaf nitrogen concentrations varied between 18 and 27 mg g-1 and were about 20% higher in the tall form than in the short form. Maximum net assimilation rates (Asat) occurred during the rainy seasons (March--April 2000 and January--February 2001) and were similar in the tall and short forms (15-22 µmol m-2 s-1) before declining to less than 10 µmol m-2 s-2 at the end of the rainy season in late April. As the dry season progressed, Asat, soil water content, predawn leaf water potential (Ψpd) and leaf nitrogen concentration declined rapidly. Before leaf abscission, Ψpd was more negative in the short form (-3.4 MPa) than in the tall form (-2.7 MPa) despite the greater availability of soil water beneath the short form trees. This difference appeared attributable to differences in root depth and density between the physiognomic types. Stomatal regulation of water use and carbon assimilation differed between years, with the tall form having a consistently more conservative water-use strategy as the dry season progressed than the short form. [ABSTRACT FROM AUTHOR]

To estimate the relative contributions of woody and herbaceous vegetation to savanna productivity, we measured the 13C/12C isotopic ratios of leaves from trees, shrubs, grasses and the surface soil carbon pool for 22 savannas in Australia, Brazil and Ghana covering the full savanna spectrum ranging from almost pure grassland to closed woodlands on all three continents. All trees and shrubs sampled were of the C3 pathway and all grasses of the C3 pathway with the exception of Echinolaena inflexa (Poir.) Chase, a common C3 grass of the Brazilian cerrado. By comparing the carbon isotopic compositions of the plant and carbon pools, a simple model relating soil δ13C to the relative abundances of trees + shrubs (woody plants) and grasses was developed. The model suggests that the relative proportions of a savanna ecosystem's total foliar projected cover attributable to grasses versus woody plants is a simple and reliable index of the relative contributions of grasses and woody plants to savanna net productivity. Model calibrations against woody tree canopy cover made it possible to estimate the proportion of savanna productivity in the major regions of the world attributable to trees + shrubs and grasses from ground-based observational maps of savanna woodiness. Overall, it was estimated that 59% of the net primary productivity (Np) of tropical savannas is attributable to C4 grasses, but that this proportion varies significantly within and between regions. The C4 grasses make their greatest relative contribution to savanna Np in the Neotropics, whereas in African regions, a greater proportion of savanna Np is attributable to woody plants. The relative contribution of C4 grasses in Australian savannas is intermediate between those in the Neotropics and Africa. These differences can be broadly ascribed to large scale differences in soil fertility and rainfall. [ABSTRACT FROM AUTHOR]

We studied the spatial and temporal habitat use of impala in Botswana's Okavango Delta at landscape level with the aid of satellite imagery, with minimal fieldwork. We related remotely sensed vegetation to impala habitat preferences, by first distinguishing three vegetation types through a multi-temporal classification, and dividing these into subclasses on the basis of their Normalized Difference Vegetation Index (NDVI). This indicator for abundance and greenness of biomass was assessed for wet and dry season separately. Similarly, habitat use was assessed for both seasons by allocating vegetation classes to bimonthly impala observations. Impala distribution patterns coincided with NDVI-based subclasses of the landscape, nested within broad vegetation types, to which impala did not show a marked seasonal response. We suggest that this methodology, using limited field data, offers a functional habitat classification for sedentary herbivores, which appears particularly valuable for application in extensive areas with high spatial variability, but with restricted access. [ABSTRACT FROM PUBLISHER]

We studied the seasonal variation in carbon dioxide, water vapour and energy fluxes in a broad-leafed semi-arid savanna in Southern Africa using the eddy covariance technique. The open woodland studied consisted of an overstorey dominated by Colophospermum mopane with a sparse understorey of grasses and herbs. Measurements presented here cover a 19-month period from the end of the rainy season in March 1999 to the end of the dry season September 2000. During the wet season, sensible and latent heat fluxes showed a linear dependence on incoming solar radiation ( I) with a Bowen ratio ( β) typically just below unity. Although β was typically around 1 at low incoming solar radiation (150 W m−2) during the dry season, it increased dramatically with I, typically being as high as 4 or 5 around solar noon. Thus, under these water-limited conditions, almost all available energy was dissipated as sensible, rather than latent heat. Marked spikes of CO2 release occurred at the onset of the rainfall season after isolated rainfall events and respiration dominated the balance well into the rainfall season. During this time, the ecosystem was a constant source of CO2 with an average flux of 3–5 μmol m−2 s−1 to the atmosphere during both day and night. But later in the wet season, for example, in March 2000 under optimal soil moisture conditions, with maximum leaf canopy development (leaf area index 0.9–1.3), the peak ecosystem CO2 influx was as much as 10 μmol m−2 s−1. The net ecosystem maximum photosynthesis at this time was estimated at 14 μmol m−2 s−1, with the woodland ecosystem a significant sink for CO2. During the dry season, just before leaf fall in August, maximum day- and night-time net ecosystem fluxes were typically −3 μmol m−2 s−1 and 1–2 μmol m−2 s−1, respectively, with the ecosystem still being a marginal sink. Over the course of 12 months (March 1999–March 2000), the woodland was more or less carbon neutral, with a net uptake estimated at only about 1 mol C m−2 yr−1. The annual net photosynthesis (gross primary production) was estimated at 32.2 mol m−2 yr−1. [ABSTRACT FROM AUTHOR]

Rapidly increasing levels of light pollution subject nocturnal organisms to major alterations of their habitat, the ecological consequences of which are largely unknown. Moths are well-known to be attracted to light at night, but effects of light on other aspects of moth ecology, such as larval development and life-history, remain unknown. Such effects may have important consequences for fitness and thus for moth population sizes. To study the effects of artificial night lighting on development and life-history of moths, we experimentally subjected Mamestra brassicae (Noctuidae) caterpillars to low intensity green, white, red or no artificial light at night and determined their growth rate, maximum caterpillar mass, age at pupation, pupal mass and pupation duration. We found sex-specific effects of artificial light on caterpillar life-history, with male caterpillars subjected to green and white light reaching a lower maximum mass, pupating earlier and obtaining a lower pupal mass than male caterpillars under red light or in darkness. These effects can have major implications for fitness, but were absent in female caterpillars. Moreover, by the time that the first adult moth from the dark control treatment emerged from its pupa (after 110 days), about 85% of the moths that were under green light and 83% of the moths that were under white light had already emerged. These differences in pupation duration occurred in both sexes and were highly significant, and likely result from diapause inhibition by artificial night lighting. We conclude that low levels of nocturnal illumination can disrupt life-histories in moths and inhibit the initiation of pupal diapause. This may result in reduced fitness and increased mortality. The application of red light, instead of white or green light, might be an appropriate measure to mitigate negative artificial light effects on moth life history.

Variations in leaf mass per unit area (Ma) and foliar concentrations of N, P, C, K, Mg and Ca were determined for 365 trees growing in 23 plots along a West African precipitation gradient ranging from 0.29 to 1.62m a-1. Contrary to previous studies, no marked increase in Ma with declining precipitation was observed, but savanna tree foliar [N] tended to be higher at the drier sites (mass basis). Generally, Ma was slightly higher and [N] slightly lower for forest vs savanna trees with most of this difference attributable to differences in soil chemistry. No systematic variations in [P], [Mg] and [Ca] with precipitation or between trees of forest vs savanna stands were observed. We did, however, find a marked increase in foliar [K] of savanna trees as precipitation declined, with savanna trees also having a significantly lower [K] than those of nearby forest. These differences were not related to differences in soil nutrient status and were accompanied by systematic changes in [C] of opposite sign. We suggest an important but as yet unidentified role for K in the adaption of savanna species to periods of limited water availability; with foliar [K] being also an important factor differentiating tree species adapted to forest vs savanna soils within the 'zone of transition' of Western Africa.