Study

Plant-insect communities and predator-prey ratios in field margin strips, adjacent crop fields, and fallows

  • Published source details Denys C. & Tscharntke T. (2002) Plant-insect communities and predator-prey ratios in field margin strips, adjacent crop fields, and fallows. Oecologia, 130, 315-324.

Actions

This study is summarised as evidence for the following.

Action Category

Create uncultivated margins around intensive arable or pasture fields

Action Link
Farmland Conservation

Leave headlands in fields unsprayed (conservation headlands)

Action Link
Farmland Conservation

Plant nectar flower mixture/wildflower strips

Action Link
Farmland Conservation
  1. Create uncultivated margins around intensive arable or pasture fields

    A replicated study from April to September 1995 near Göttingen, Germany (Denys & Tscharntke 2002) found higher predator abundance (mainly spiders Araneae) and higher predator-prey ratios in 6-year-old than in 1-year-old naturally developed field margins. In addition, predator-prey ratios were higher in large, naturally developed fallows than in the field margins. These results emphasize the importance of habitat age and area for the establishment of natural enemy populations. However, arthropod species richness in naturally developed margins did not differ from other margins types. Potted plants of mugwort Artemisia vulgaris (four pots per margin) and red clover Trifolium pratense (three pots per margin) were used to study plant-arthropod communities. Red clover pots were also set out in winter wheat fields at 4, 8 and 12 m distances adjacent to strips sown with cereal and wildflower mix. Red clover pots were set out in April 1995. On five visits in June and July 1995, flower heads of red clover were sampled, dissected and the larvae and pupae of arthropods feeding inside the plants reared in the lab for species determination. Results from the same study are also presented in (Denys 1997, Denys et al. 1997).

  2. Leave headlands in fields unsprayed (conservation headlands)

    A replicated study from April to September 1995 in five types of field margin around four cereal fields near Göttingen, Germany (Denys & Tscharntke 2002) (same study as (Denys 1997, Denys et al. 1997)) found that unsprayed margins sown with cereals (conservation headlands) suppressed the colonization of aggressive weeds. However, abundance of predators (mainly spiders (Araneae)) and predator prey ratios in cereal sown margins were lower than in six-year-old naturally developed margins. Arthropod abundance, diversity and predator-prey ratios in the cereal margins did not differ from the rest of the studied margin types. The following margin types (3 m-wide, 100-150 m long) were studied: one-year old naturally developed, six-year old naturally developed, sown with mixture of 19 wildflower species, sown with phacelia Phacelia spp. mixture, and control strips sown with winter wheat or oats. Potted plants of mugwort Artemisia vulgaris (four pots per margin) and red clover Trifolium pratense (three pots per margin) were used to study plant-arthropod communities. Mugwort pots were set out in May and visited weekly to count all arthropods living on the plants, leaf miners and galls that had colonized the plants. In September, the plants were dissected and all larvae and pupae living inside the plants were individually reared in the lab to estimate parasitization rates. Red clover pots were set out in April. At five visits in June and July, flower heads were sampled, dissected and larvae and pupae were reared in the lab for species determination.

     

  3. Plant nectar flower mixture/wildflower strips

    A replicated study from April to September 1995 near Göttingen, Germany (Denys & Tscharntke 2002) (same study as Denys 1997, Denys et al. 1997) found that sown wildflower strips had higher plant species richness and could suppress the abundance of aggressive arable weeds. However, arthropod species richness and abundance in wildflower strips did not differ from the other margin types. Both the abundance and species richness of arthropods found on red clover Trifolium pratense plants in wheat fields decreased with increasing distance from the margins, however the decrease in abundance was less pronounced in fields with sown wildflower strips where dispersal from the margin into the field was higher than for control margins. Five margin types (3 m wide, 100-150 m long) around four cereal fields were studied: sown with a mixture of 19 wild flower species, sown with a phacelia Phacelia tanacetifolia mixture, one-year-old naturally developed, six-year-old naturally developed, control strips sown with winter wheat or oats. Potted plants of mugwort Artemisia vulgaris (four pots/margin) and red clover (three pots/margin) were used to study plant-arthropod communities. Red clover pots were also arranged in cereal fields at 4, 8 and 12 m from wildflower strips to assess dispersal. Mugwort pots were set out in May and visited weekly to count all arthropods feeding inside the plants, leaf miners and galls. In September, the plants were dissected and all larvae and pupae found inside the plants were individually reared in the lab to estimate parasitization rates. Red clover pots were set out in April. At five visits in June and July, flower heads were sampled, dissected and larvae and pupae found inside the plants were reared in the lab for species determination.

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