Decline of Old‐Growth Redwood Forests in Relation to Some Soil Microbiological Processes

Abstract

Observations on a number of old—growth coast redwood Sequoia sempervirens (D. Don) Endl. forests indicated unusual features of stand decline. To test the hypothesis that this decline resulted from some deterioration in the forest—site relationship, a series of studies was made on forest soils under old—growth redwood and at various stages of the hardwood succession following logging. Proliferation of redwood seedling roots was restricted in old—growth redwood soil and some evidence of seedling susceptibility to a root pathogen was found. Soil respiration patterns indicated that the availability of carbonaceous material from the organic matter in a form suitable for microbial digestion may be the primary factor limiting biological activity. The end results may be failure of, or abnormalities in, the process of nitrogen mineralization, and the establishment of an edaphic condition in which pathogens can attack seedling roots. Although nitrogen was found to be strongly immobilized in soils from an age sequence of tan oak developed on former redwood sites, it seems possible that tan oak litter could stimulate a higher level of microbial activity and so accelerate the decomposition of redwood humus. Deterioration in both the soil microbiological processes and the plant—soil relationship in a redwood forest are discussed in terms of the long—term incorporation of redwood litter into the soil.

The endophytic fungal community in leaves of a coastal redwood population diversity and spatial patterns

“…Some of tbe recorded species are able to attack seeds and seedlings of coastal redwood and could be responsible in part for the low seedling establishment in natural stands, wbich has been attributed to fungus attack, i.e. damping-off and root rot (Muelder & Hansen, 1961;Florence, 1965;Davidson, 1971). These weak pathogens could be very important as natural selection agents eliminating debilitated or susceptible individuals or attacking seeds and seedlings.…”

Compensatory Recruitment, Growth, and Mortality as Factors Maintaining Rain Forest Tree Diversity

“…Indirect deleterious influences, via natural enemies such as microorganisms, fungi, herbivores, etc., are a third possibility. Florence andCrocker (1962), Florence (1965), and Webb et al (1967) suggested that microorganisms associated with roots may have deleteriously affected tree seedlings, although direct interference by toxins from the roots themselves was not ruled out. For natural enemies to produce the observed compensatory trends in growth and mortality between nearest neighbors they probably need to be relatively species specific in their attacks.…”

“…Beals ( 1965) studied 20 remnant stands of Lebanon cedar and found that: "cedar seedlings thrive under hardwood trees and shrubs but not under cedar trees, so that some disturbance is apparently necessary for cedar-forest regeneration." Florence and Crocker ( 1962) and Florence (1965) found that in Eucalyptus pilularis in Australia and Sequoia sempervirens in California, growth of seedlings was poor in soil taken from beneath adults. However if the microorganisms were killed by irradiation, seedling growth was greatly improved.…”

Nitrogen and Lignin Control of Hardwood Leaf Litter Decomposition Dynamics

“…Slow rates of litter decomposition can result in the accumulation of large nutrient stocks in a soil's surface horizons, and nutrient limitations for primary producers (Siren 1955, Weetman 1962, Heilman and Gessel 1963, Florence 1965, Watt and Heinselman 1965, Heilman 1966, Miller 1969, Adams et al 1970, Lamb 1971. The rate of litter decomposition is influenced by a number of factors including moisture, temperature, and nature of the microorganisms and soil fauna active in the decomposition process (Tenney and Waksman 1929, Witkamp 1971, Meentemeyer 1978).…”