Critical analysis of goal references for selection forests in the Black Forest region based on steady-state models.

The objective of the present paper is to critically analyze goal references for single tree selection forests ('Plenterwaelder') in the Black Forest g rowth region deduced in model-studies by PRODAN (1944, 1949) regarding the database (increment values and harvesting strategies) and the model base (c ompetition representation and model logic). Using inventory data of the permanent inventory plots in Baden-Wurttemberg as a basis, site-specific hight-curves are constructed from height-measurem ents of silver fir and Norway spruce taken from the sample surveys in selec tion forests. These hight-curves are compared with the hight-tariffs of PRO DAN (1949) and are assigned to site-indices. Subsequently the site units in the 'regional groups' are assigned to steady-state standing volumes for se lection forests ("Plenterwald-Gleichgewichtsvorrate") as suggested by PRODA N (1949). The steady-state volumes for the investigated site-units are loca ted between 280 m(3) and 440 m(3) per hectar. In addition, the selection fo rests of four regional groups are classified according to their number of s tems in the medium diameter size-class (25 cm to 50 cm dbh) and the big dia meter class (> 50 cm dbh) in a diagramm by MITSCHERLICH (1952). It can be s hown that the selection forests in the investigation area are characterized by a lack of small-sized stems. A critical review of the goal-references used by PRODAN (1949) demonstrates that the steady-state volumes are based on increment-curves, which lie esp ecially in the small-size diameter range (< 20 cm dbh), far above the resul ts of recent research by SPIECKER (1986) and research in Switzerland (SCHUT Z, 1989). In addition, the assumed harvest-strategies for the construction of the model-curves by PRODAN (1949) differentiate clearly from surveys mad e by SPIEKKER (1986) in experimental plots and from research findings in Sw itzerland (SCHUTZ, 1989). Finally, general logical problems of the used ste ady-state model are discussed and a proposal for a new definition of the st eady-state for selection forests is provided.