| 词汇 | example_english_heather |
| 释义 | Examples of heatherThese examples are from corpora and from sources on the web. Any opinions in the examples do not represent the opinion of the Cambridge Dictionary editors or of Cambridge University Press or its licensors. Few larvae were found in dew droplets or concealed within heather leaflets; most larvae were recovered from the plant surface. They vary from heather moorland to agrostis pastures invaded by gorse and bracken. This may be particularly important since heather is a structurally complex plant. The percentage cover of grasses, bracken, heather, and moss was estimated using ten randomly positioned 0.25 m2 quadrats. This should reduce the possible variability associated with heather stand age and the actual amount of heather present in the vegetation. However, all the seedbank data were derived from sites where heather was the dominant species, usually in the mature phase. All three figures were estimated from stands of mature heather with c. 100% cover. As he says, 'many a heather-covered hillside is a gravestone to a once awe-inspiring volcano'. To examine whether larval migration was as efficient on heather as on a monocotyledon or on a structurally simple dicotyledon we undertook a second experiment. Significantly more larvae of both nematode species were recovered in the region of the heather than the grass or controls. In the first group of eight trays, five heather stems were planted at distances 2, 4, 6, 8 and 10 cm from the centre. The highest numbers were recovered from the heather stems; the lowest numbers were recovered from the wheat stems (fig. 3). After constant exposure, significantly more larvae were recovered from heather than from either of the control plants. The heather stems had been trimmed so that each had a vertical stem that extended 7 cm above the soil surface. This implies that the structural complexity of heather causes no problems for the infective larvae. However, more larvae were recovered from soil closest to caecal faeces in trays with heather present than in trays without (fig. 2). The plant-derived material was identified as a combination of heather and grasses originating adjacent to the snowfield. The other treatments were alcohol alone, water alone, and a perfume called 'heather' in alcohol solution. This suggested that larvae might respond to a cue or stimulus produced by heather, which may also influence their horizontal migration. The ones used in the analysis represented a subsample of the available data; only sites with a heather cover of 75% or more were selected. In this way, the parasite may remain in the seed bank when heather is too old and quickly reappears after management, such as mowing, turf-cutting or burning. This is surprising, as one would expect fewer and not more larvae in the soil of trays with heather present if larvae were adapted to climb heather. Thus, in contrast to the hypothesis that larvae select heather to ascend, we can propose the null hypothesis that larvae simply migrate towards the closest vegetation. However, the relatively large distances the larvae would have to travel on heather would mean the larvae would spend a great deal of time not exposed to the definitive host. These examples are from corpora and from sources on the web. Any opinions in the examples do not represent the opinion of the Cambridge Dictionary editors or of Cambridge University Press or its licensors. |
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