Non-cultivated Areas Research Articles

Changes in earthworm populations following cultivation of undisturbed and former opencast coal-mining land

Earthworm response to a single cultivation sequence was assessed. Cropping and management of cultivated land was similar to that of non-cultivated areas. Effects were measured in a trial on recently replaced opencast mining land. A subsequent survey investigated responses to cultivation on both replaced and undisturbed land at periods since cultivation ranging from 1.5 to 7.5 years. On undisturbed land, adverse effects of cultivation, if any, were short-lived, with numbers of all species, but particularly deep-burrowing species, having recovered or increased after 3 years. However, on replaced land the initial adverse effect appeared to be larger, and recovery from this effect was delayed until at least 5 years after tillage. Different species present ( Lumbricus terrestris/ Aporrectodea longa, Lumbricus rubellus/festivus, Aporrectodea caliginosa/Octalasion tyrtaeum and Allolobophora chlorotica) also varied in the extent of the initial reduction and in their rate of recovery. Reasons for different responses to cultivation and implications for the management of replaced land are considered.

The fate of Mus domesticus demes after destruction of their habitats

To test our hypothesis that gene flow has the potential to prevent genetic isolation of crib populations separated by several kilometres, we caught and marked 137 house mice leaving six cribs being emptied of corn. In an attempt to recapture the mice, we set traps just after crib emptying and again, where feasible, 1–2 months later, in areas surrounding cribs (trap-nights/trap-area in hectares:cultivated fields, 3834/29.4; non-cultivated areas, 2238/4). Additional trapping was carried out near nine empty cribs and in eight cultivated fields (3304 trap-nights, 17.7 ha trap-area), each more than 120 m from cribs. After the six cribs were emptied, we recaptured 11% of the crib mice (distance from the crib:mean 81 m, range 0–570 m). In refuge habitats, away from cribs, a breeding population existed and three crib females bred there after emptying of cribs. In demonstrating long dispersal distances and breeding populations away from cribs, our data support the hypothesis that gene flow is potentially large enough to prevent genetic isolation of crib populations separated by expanses of cultivated and uncultivated terrain. The influence of decreased recruitment on gene migration is unclear. Potential predators on nestlings, such as Norway rats, deermice, shrews and voles, escaped from and were trapped outside cribs.

Distribution of the Melon Fly, Dacus cucurbitae (Diptera: Tephritidae), and Host Plants on Kauai, Hawaiian Islands

Distribution of the melon fly, Dacus cucurbitae Coquillett, was determined by trapping males at 330 sites throughout the island of Kauai. Melon flies were most numerous at coastal trap sites, particularly along the south and west coasts. The Waimea Valley site located on the southwest coast was the one with the highest trap catch. Lowest catches were made at the highest elevations at the center of the island. Trap catches declined sharply with increasing rainfall and increasing elevation. However, during the seasonal peak in abundance in late summer, a few flies were trapped in the higher elevations where no host plants were present. These flies were evidently migrating rather than breeding flies. Melon fly distribution was related to distribution of its host plants. Distribution of the fly was largely along coastal areas of the island where host plants were present in commercial and backyard gardens. The melon fly was also present in noncultivated areas where the wild host, Momordica balsamina L., was located along edges of fields and roadsides.

Sensibilité des milieux et impacts des activités humaines sur le massif du Ventoux

A map depicting the fragility of the environment has been drawn up (see Appendix), which distinguishes two main groups. 1) Areas of natural vegetation with low human influence. These include : a) the mature forests. These are poorly represented (only 5300 ha) due to previous overexploitation ; b) the pre-climax forest stages (mainly coniferous) covering about 1000 ha ; c) “degraded” habitats (scrub and grassland), which are mapped in terms of their value as pasture. Scrub covers about 2800 ha, and grassland about 1200 ha. These natural ecosystems make up about half of the non-cultivated areas. 2) Areas with severe human pressure. This pressure may be due to one of several activities. Extensive reafforestation has been carried out since about 1860 (much of the natural forest having been destroyed by then), so that the new forests now cover the other half of the non-cultivated areas. In addition to native species, the exotics Pinus nigra ssp. austriaca and Cedrus atlantica have been widely planted. The cultivated areas are restricted to the foot of the mountain, although sheep are grazed to much higher altitudes. The type of agriculture is related to the natural vegetation series being exploited, and in most places is tending towards monoculture (mainly of vines, fruit-trees or lavender). Other human pressures include housing, roads, military activities and tourism ; industry is very limited in extent. The Mont Ventoux shows a fairly balanced relationship between man and his environment for several reasons. 1) Forest is by far the dominant vegetation type (covering about 75% of the massif). 2) The areas of non-climax and degraded vegetation are relatively restricted in extent, and have a considerable landscape value and economic importance. 3) The impact of forestry and agriculture is negligible, since these areas harmonise remarkably well with the natural landscape. 4) There has been no excessive development of other human activities, although the increasing number of holiday homes is a potential threat.

Occurrence and establishment of Pythium in soils

Species of Pythium were isolated from cultivated soils by using susceptible host seedlings as baits, but could not be found in soils taken from woodland or other non-cultivated areas. No isolates were obtained from very acid soils in which Trichoderma viride was particularly abundant. The behaviour of inocula of Pythium mamillatum in a cultivated (native) soil, and in a woodland (alien) soil was assessed by means of the host test described. Maize meal added to the cultivated soil became colonized by P. mamillatum after only 2 days, indicating, that under these conditions, the parasite behaves as a saprophytic ‘sugar fungus’. In the alien woodland soil P. mamillatum did not colonize maize meal. After neutralization of this acid soil with lime, however, the fungus rapidly utilized the material. The parasite could not be grown in culture at the low pH value of the alien soil. The behaviour of vegetative hyphae of P. mamillatum in these contrasting soils was studied by the glass-fibre tape technique. In native, cultivated soil, oospores and resting sporangia were formed abundantly, whereas in alien woodland soil these bodies were not produced. Thus the inability of Pythium hyphae to produce a resting phase may prevent long-term survival of the parasite in alien soils. This effect was shown to be due to low pH value of the soil, which may directly limit the normal life cycle of Pythium in acid woodland soils.