Holzner


Die Bodenkultur - Journal for Land Management, Food and Environment

W. HOLZNER:

Weed-Types

A Classification of Ruderals and Segetals Using Complex Biological-ecological Criteria

Part one: "Annual and Biennial" Species

Summary

14 "weed-types" were described regarding as many characteristics as possible, particularly germination habit, growth form, life form, site requirements, distribution area, and sociological properties:

A. Flowering and seed-set soon after germination; reproductive phase continues as long as environment is favourable; not such a pronounced seasonality as with other annuals.

B. Poor competitors, flowering and seed-set in spring followed by death.

C. Competitive summer-annuals, prefering rich soils, with large seed bank (great seed longevity).

D. Weak summer-annuals of cool areas and acid soils.

E. Tiny summer-annuals on soils that are very wet after winter.

F. Weak summer-annuals requiring warm summers.

G. Strong (competitive) summer-annuals requiring high soil-temperatures for germination and warm summers.

H. Winter-annual segetals ripening their seeds in summer.

I. Specialists with crop mimicry, seeds distributed as impurities of grain.

J. Small, modest winter-/summer-annuals.

K. Larger species, very flexible regarding life-span and the relationship vegetative/reproductive phase - both depending on the germination time.

L. Modest winter-annuals (rarely summer-annual) with seed dispersal over long distances.

M. Modest "biennials", requiring light for germination, with seed-bank of very long life (dispersal in time).

N. "Biennials" prefering better soils, germinating without light, seed dispersal in space, practically no seed bank; protective features and agents against big herbivores.

The strategy, (theoretical) niche and the site properties of all these types are described, the question of the origin (primary site) discussed and some examples are given for each type. From this biological considerations conclusions on the agricultural importance (weediness) of the species can be drawn.