TRUFFLE PRODUCTION IN OLD-GROWTH AND MATURE FIR STANDS IN NORTHEASTERN CALIFORNIA

Few studies have examined fruiting patterns of hypogeous fungi, and re lationships between sporocarp production of hypogeous fungi and forest habitat components such as organic soil depth and amounts of decayed wood are poorly understood. We sampled sporocarps of hypogeous fungi ( truffles) in four old-growth (> 200 years) and four paired, mature (ca 100 years) fir (Abies spp.) stands during four sample periods in 1993 and three sample periods in 1994 in the Lassen National Forest in nor theastern California. Truffles were collected from 4-m(2) circular plo ts systematically located at 36 grid points per stand during-each samp le period. Habitat characteristics were measured in 50.3-m(2) circles centered at each grid point in 1993. We found a total of 46 truffle sp ecies in 30.4% of the 2016 total plots, and the total standing dry wei ght of truffles was equivalent to 2.43 kg ha(-1). Total frequency and biomass of truffles and number of truffle species did not differ signi ficantly between stand types in 1993 or 1994, but species composition did. We found no significant associations between measures of total tr uffle abundance and measures of habitat structure and composition at t he 0.25-ha grid scale or at the 50.3-m(2) habitat plot scale. At the s cale of the 4-m(2) truffle plot, plots with decayed wood were more lik ely to have truffles than plots without decayed wood during the final sample period of each year, but the association was significant only i n 1993. Mean organic soil depth was greater in plots with truffles tha n plots without truffles in each sample period in both years, but rank ed values were only marginally significant in one sample period. Goodn ess-of-fit tests to the Poisson distribution indicated that individual truffles had clumped distributions, but we could not reject the null hypothesis of random distribution of truffle collections. Our results indicate that total truffle production had recovered from stand-replac ement wildfire in the mature stands, and that total truffle abundance was not strongly associated with habitat characteristics within the ra nge of habitat variation exhibited in these stands. Individual species , however, were associated with old-growth stands and others with matu re stands. (C) 1997 Elsevier Science B.V.