The invasive potential of Australian banksias in South African fynbos: A comparison of the reproductive potential of Banksia ericifolia and Leucadendron laureolum

Abstract Several taxa of the Australian Proteaceae have invaded South African fynbos and require costly management programmes to bring under control. Banksia spp. have been introduced only recently to fynbos regions. The invasive potential of Banksia ericifolia (Proteaceae) was investigated by comparing its recruitment potential with that of an indigenous proteaceous shrub, Leucadendron laureolum. Both species are overstorey shrubs that are killed by fire and rely on canopy-stored seeds (serotiny) for recruitment. Eight year old B. ericifolia shrubs produced an average of 16 500 seeds per plant, which is thirty times more than the average of 570 seeds produced by 10 year old L. laureolum shrubs. The seed bank of B. ericifolia was not only larger than that of L. laureolum (1098 vs 525 viable seeds m^?2 projected canopy cover), but also considerably larger than that described for the species in its native environment (200–330 seeds m^?2 in a 9 year old stand north of Sydney). Leucadendron laureoleum released most of its seed a few days after the cones were burnt, whereas seed release in B. ericifolia was spread over 12 weeks. The seeds of B. ericifolia had lower wingloading and fall rates than L. laureolum and were dispersed over greater distances. The relative seedling growth rates of the two species were very similar (0.03 g per day), but below-ground biomass was greater and proteoid roots were more developed in B. ericifolia seedlings than in L. laureolum after 100 days. Four year old B. ericifolia plants growing in the field had attained over twice the height of indigenous pro-teoids and accumulated up to 10 times the fresh biomass of L. xanthoconus, a species which is ecologically similar to L. laureolum. The Bioclimatic Prediction System (BIOCLIM) was used to create a bioclimatic profile of B. ericifolia and identify climatically suitable areas in the Cape Province. Results show that its potential distribution covers most fynbos areas in the southwestern Cape. It is concluded that B. ericifolia has the potential to be highly invasive in fynbos.     

Food,microhabitat, or both? Macroinvertebrate use of leaf accumulations in a montane stream

1. Leaf packs in streams may serve as food and substrate to many macroinvertebrates, but the relative importance of these two functions has not been disentangled. To test the hypothesis that leaf packs are colonized primarily for their food value rather than as microhabitat, the colonization of leaf packs of red alder and of polyester cloth in a natural stream was compared. 2. Species of shredders showed large differences in the colonization of the two types of leaf pack with almost no use of artificial leaf packs. Non-shredders were also more abundant on natural leaf packs, however, they colonized artificial leaf packs six to eighty times proportionally more than shredders. 3. The effect of different leaf types was virtually eliminated for non-shredders when the amount of fine parriculate detritus (food for many non-shredders) trapped in the leaf pack was added to the analysis as a covariate. Therefore, to non-shredders, leaf types differed only in the retention of fine particulate organic matter. 4. Comparisons of the use of both kinds of leaf packs in riffles versus pools revealed that significantly fewer animals colonized pool leaf packs. 5. These results suggest that food value, and not microhabitat, is the primary determinant of leaf pack use for most shredders and non-shredders.     

Microcrustacea in flowing water: experimental analysis of washout times and a field test

1. Flow-chamber experiments were conducted to evaluate the ability of microcrustacea to maintain position in moving water. These results were compared to distributions of zooplankton and water velocity in a stream pool to determine the relationship of animal density to water movement and swimming ability. 2. Cladocerans exhibited negative rheotaxis (directed behaviour against a current) but poor ability to maintain position at velocities >2.5cm s^?1. Daphnia and Scapholeberis were better at avoiding washout than Moina and Diaphanosoma. At velocities <2.5cm s^?1Eucyclops (Cyclopoida) tended to exhibit no rheotaxis. 3. Washout of Daphnia was complete at velocities >2.5cm s^?1, Scapholeberis >3.2cm s^?1 and Eucyclops >7.75 cm s^?1. Washout time of Daphnia and Scapholeberis was positively related to body size and negatively to water velocity and possession of eggs. Washout was inversely related to water velocity for Eucyclops. 4. Highest densities of microcrustacea in a stream pool were found in non-flowing or downstream zones of the pool. Benthic (Hydracarina, harpacticoid copepods, ostracods) and fast-swimming (cyclopoids) forms were most common in flowing zones. Facultatively benthic Cladocera were abundant in regions of no flow. Rotifers and immature copepods were most abundant at the downstream end of the pool. 5. Behavioural mechanisms for remaining in stream pools at times of high flow appear to include: (i) flow avoidance (Simocephalus, Chydorus, Scapholeberis and cyclopoids), (ii) use of benthic habitat (ostracods, harpacticoids, Hydracarina), (iii) strong swimming ability (cyclopoids).     

Exceptional preservation in Lower Devonian coalified fossils from the Welsh Borderland: a new genus based on reniform sporangia lacking thickened borders

Reniform sporangia, comprising two equal valves and containing retusoid spores, recovered from Lower Old Red Sandstone strata of Devonian age ( micrornatus-newportensis Spore Biozone: lower Gedinnian lower Lochkovian) on North Brown Clee Hill in the Welsh Borderland are placed in Resilitheca salopensis gen. et sp. nov. Conventional compression fossils from Targrove, Ludlow of fertile axes showing isotomous branching with limited overtopping are considered conspecific because the terminal reniform sporangia contain the same spores. Spore ultrastructure is described using scanning and transmission electron microscopy. Sections show faint traces of lamellae. Particles associated with spores and sporangium wall are compared with the globules of pteridophytes and Ubisch bodies of angiosperms, and related to the development of the sporangium. The new plants are compared with Cooksonia caledonica Edwards known only from impressions, and with Renalia Gensel showing far more pronounced pseudomonopodial branching.     

Morphology and Morphogenesis of Fuscheria terricola n. sp. and Spathidium muscorum (Ciliophora: Kinetofragminophora)1

The morphology and morphogenesis of the kinetofragminophoran soil ciliates, Fuscheria terricola n. sp. and Spathidium muscorum Dragesco & Dragesco-Kerneis, 1979, are described. Stained specimens (protargol) are characterized biometrically. The new species differs from the other species of the genus in its body size, body shape, number of kineties, length of extrusomes, and habitat. Both species have telokinetal stomatogenesis, which commences with a proliferation of kinetosomes at those kineties which bear the brosse. Fuscheria terricola does not have a complex perioral ciliature; indeed, it might be that this species has only monokinetids. Thus only a proliferation of kinetosomes and the separation of the kineties takes place in the prospective division furrow. In contrast, S. muscorum differentiates short dikinetid kinetofragments in the region of the division furrow, which are arranged to form the perioral kinety of the opisthe in the intermediate and late stages of the stomatogenesis. The right part of the perioral kinety develops first. This and other studies show that telokinetal stomatogenesis proceeds very differently depending on the differentiation of the oral ciliature; however, detailed studies on the morphogenesis of kinetofragminophoran ciliates are still too few in number for subtypes to be defined.     

Contribution of N2O to the greenhouse gas balance of first-generation biofuels

In this study, we analyze the impact of fertilizer‐ and manure‐induced N₂O emissions due to energy crop production on the reduction of greenhouse gas (GHG) emissions when conventional transportation fuels are replaced by first‐generation biofuels (also taking account of other GHG emissions during the entire life cycle). We calculate the nitrous oxide (N₂O) emissions by applying a statistical model that uses spatial data on climate and soil. For the land use that is assumed to be replaced by energy crop production (the ‘reference land‐use system’), we explore a variety of options, the most important of which are cropland for food production, grassland, and natural vegetation. Calculations are also done in the case that emissions due to energy crop production are fully additional and thus no reference is considered. The results are combined with data on other emissions due to biofuels production that are derived from existing studies, resulting in total GHG emission reduction potentials for major biofuels compared with conventional fuels. The results show that N₂O emissions can have an important impact on the overall GHG balance of biofuels, though there are large uncertainties. The most important ones are those in the statistical model and the GHG emissions not related to land use. Ethanol produced from sugar cane and sugar beet are relatively robust GHG savers: these biofuels change the GHG emissions by −103% to −60% (sugar cane) and −58% to −17% (sugar beet), compared with conventional transportation fuels and depending on the reference land‐use system that is considered. The use of diesel from palm fruit also results in a relatively constant and substantial change of the GHG emissions by −75% to −39%. For corn and wheat ethanol, the figures are −38% to 11% and −107% to 53%, respectively. Rapeseed diesel changes the GHG emissions by −81% to 72% and soybean diesel by −111% to 44%. Optimized crop management, which involves the use of state‐of‐the‐art agricultural technologies combined with an optimized fertilization regime and the use of nitrification inhibitors, can reduce N₂O emissions substantially and change the GHG emissions by up to −135 percent points (pp) compared with conventional management. However, the uncertainties in the statistical N₂O emission model and in the data on non‐land‐use GHG emissions due to biofuels production are large; they can change the GHG emission reduction by between −152 and 87 pp.     

Action Potentials in Lupinus angustifolius L. Shoots: IV. APPLICATION OF THERMAL STIMULI AND INVESTIGATIONS ON THE CONDUCTION PATHWAYS OF THE EXCITATION

The character of action potentials induced by thermal or electricalstimulation and their blocking by removal of a ring of tissuefrom the shoot as well as the spread of these potentials inthe Lupinus shoot were investigated. The appearance of anothertype of excitation was noted as a graded response occurringlocally. This potential was termed graded potential (GP). Itappears in tissues in which action potentials (AP) are not observed. It is proposed that two interrelated types of reaction to stimulioccur in various types of plant tissue.