Introduction

        CRYPTOS, the Cooperative Redwood Yield Output Simulator, is an inter-
active computer program designed to simulate growth and yield redwood and
Douglas-fir forest stands found in the north coastal region of California. 
The objective of the User's Guide is to describe the operation of the CRYPTOS
program. Further detail on the architecture of the simulator and the 
development of the growth models contained in the CRYPTOS program are 
reported by Krumland and wensel (1980, 1981) and Krumland (1982). Volume 
tables used are given by Wensel and Krumland (1983); site indices in Wensel
and Krumland (1986), and mortality estimates by Krumalnd, Dye, and Wensel 
(1978). The program, written in sandard FORTRAN 77 code (ANSI, 1978), is 
operational on the following systems:

Range and applicability

        The CRYPTOS program can be applied to real or imagined forest stands 
of any size/age composition. However, it is recognized that the theoretical
projection capabilities of the CRYPTOS program may be somewhat heroic and
some forecasting situations may be without empirical supporting data. Such
unsupported simulations may be use of the user, but a brief discussion of
the range of stand conditions used to build the growth models will provide
the user with an understanding of the foundation upon which CRYPTOS rests.

        The growth models imbedded in the CRYPTOS program have been 
developed from the records of an extensive collection of permanent growth
plots located in Del Norte, Humboldt, and Mendocino counties. The majority
of growth plots were located in the coastal zone that is subject to fog 
influence and is commonly referred to as the northern redwood region. By 
basal area, the average composition of sample plots was approximately 60
percent young-growth redwood, 25 percent other young-growth conifers 
(primarily Douglas-fir), amd the remainder being comprised of residual old
growth and hardwoods. The main species groups (young-growth redwood, Douglas-
fir, and tan oak) ranged in composition from zero to 100 percent although
single-species compositions greater than  70 percent were mostly restricted
to redwood. Very few stands composed of trees under 15 years of breast high 
age or over 90 years of age were sampled. In terms of stocking, over 85 
percent of the sample plots had between 50 and 450 trees per acre. About 70
percent of the sample plots were from apparently even-aged stands with the
remainder being from two-storied or multi-aged conditions. About 25 percent
of the growth plots had been partially harvested prior to growth sampling.

        For stand conditions comparable to the sample data, extensive 
testing of the CRYPTOS model has indicated a reasonal compliance between
simulated yields and empirical growth plot development. Detailed tests are 
described by Krumland (1982). The relability of the CRYPTOS model beyond
these sample ranges is currently unknown and users who are contemplating 
using the model in such situations are cautioned to do some additional
checking.