The steppe pika Ochotona pusilla in Britain, and a new northerly record

The known localities for steppe pika Ochotona pusilla, which occurred in Britain during Late Pleistocene times, are reviewed. A previously misidentified lower jaw, from Helsfell Cave in the Lake District, Cumbria extends the known range of this species in Britain 100 km further north.     

Methane emission from Texas rice paddy soils. 1. Quantitative multi-year dependence of CH4 emission on soil, cultivar and grain yield

Methane emissions at different rice productivity levels were observed from Texas rice paddy soils during the years 1991–95. Analysis of field measurements showed that seasonal methane emission (E) was strongly dependent on soil, cultivar, and rice grain yield. The relationship can be quantitatively described by E (g m^–2) = 0.048 × SI × VI × GY. SI is a soil index to characterize the relative effect of soil texture on emission and is linked with soil sand percentage. VI is a variety index to identify the intervarietal difference in methane emission and is related to the amount of methane emission per unit grain yield. GY is grain yield (g m^–2). Constant 0.048 was derived from the measurements of 10 cultivars planted in 1993. Computed emission applying the relationship is well matched with measured data. The comparison of computed with measured seasonal methane emission over an 80-day period using a total of 32 data sets yields a correlation coefficient r ² of 0.800. In addition, the ratio of seasonal methane emission to net primary productivity was calculated on a carbon to carbon basis, which produces an average value of 2.8%, ranging from 1.2% to 5.4%. A further investigation indicated that the ratio is soil and variety dependent and can be quantitatively explained by C[CH₄]/C[NPP] (%) = 3.21 × SI × VI + 0.12 ( r ² = 0.738, n = 32). Under the condition of 30% soil sand, this ratio is ≈ 3% for the majority of cultivars.     

Annual ryegrass toxicity: parasitism of Lolium rigidum by a seedgall forming nematode (Anguina sp.)*

Infection of annual ryegrass (Lolium rigidum) by Anguina sp. resulted in replacement of seeds by bottle-shaped galls, each containing several hundred quiescent, second-stage larvae. The biology of the nematodes, including the emergence of larvae from galls, survival in soil, and movement into and development within the host plant, has been examined. Larvae were not able to leave the galls during the dry summer, but emerged within soil 2–6 wk after normal autumn rains and following partial decay of the gall rind. Emergence took place over several months, and not all larvae emerged in any one year; they were able to survive over summer in soil both within and outside the galls. Under suitable moisture conditions, host plants were infested by larvae which climbed up the outer surfaces, became lodged within leaf sheaths, and then gradually moved towards the centre of the plant. Larvae which reached the central or axillary meristems prior to flowering were carried up with the elongating inflorescence, and attacked developing floret primordia. The nematodes developed rapidly to the adult stage, and eggs were being laid within galls by the time the inflorescence had emerged. Second-stage larvae hatched quickly and were the only live stage remaining after the ryegrass had died.