Cascade Head Research Articles

Comparison of methods for estimating soil nitrogen transformations in adjacent conifer and alder–conifer forests

Nitrogen transformations were examined in two pairs of adjacent, 55-year-old forests dominated by conifers (primarily Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco)) and by conifers and nitrogen-fixing red alder (Alnusrubra Bong.). Nitrogen availability was examined in aerobic and anaerobic incubations in the laboratory, and with resin-core and buried-bag incubations in the field. Rates of nitrogen mineralization and immobilization were examined in the field incubations using [15N]ammonium. Net nitrogen mineralization in a year-long series of resin-core incubations of forest floor plus 0–0.15 m depth soil was about 9 kmol•ha−1•year−1 for the two alder–conifer stands, but almost nil in the conifer stand at the low-productivity Wind River site, and 2.1 kmol•ha−1•year−1 in the conifer stand at the high-productivity Cascade Head site. The 15N pool dilution experiment showed that buried-bag incubations demonstrated more differences among stands than did resin cores; resin cores typically gave greater rates than buried bags. Previous estimates of nitrogen budgets were coupled with net mineralization estimates to examine how well the estimated fluxes balanced at an ecosystem scale. This tabulation of the complete nitrogen cycles showed substantial discrepancies, prompting caution in interpretation of some of the differences among the stands.

Factors Determining Differences in Soil pH in Adjacent Conifer and Alder‐Conifer Stands

AbstractTree species may differ in their influence on biogeochemical cycles, leading to differing rates of soil acidification. Over time, quantitative and qualitative changes develop in the characteristics of the soil exchange complex. Three such characteristics regulate soil pH: (i) the quantity of acids present, which can be represented as the total cation‐exchange capacity (CEC); (ii) the degree of dissociation of the acids, commonly called base saturation; and (iii) the affinity of the acids for H+, or acid strength, which represents the composite pKa (negative log of the acid ionization constant) of the exchange complex. We examined the importance of these three factors in explaining the differences in soil pH between adjacent stands of conifers [primarily Douglas fir, Pseudotsuga menziesii (Mirbel) Franco] and conifers mixed with N‐fixing red alder (Alnus rubra Bong.). At a low‐productivity site (Wind River, WA), the pH of 0 to 0.15 m of soil from both alder‐conifer and conifer stands averaged 4.3 in 0.01 M CaCl2. The pH values were the same, however, only because higher base saturation in the alder‐conifer stand was offset by greater acid strength. At a more productive site (Cascade Head, OR), soil pH (in 0.01 M CaCl2) averaged 3.7 in the alder‐conifer stand but 4.4 in the conifer stand. The difference in pH resulted primarily from greater acid strength of soil organic matter under alder, and secondarily from lower base saturation of the exchange complex. These results underscore the importance of considering qualitative changes in soil organic matter as factors driving changes in soil pH and other parameters.

Retention of needles and seeds on logs in Picea sitchensis – Tsuga heterophylla forests of coastal Oregon and Washington

Logs are a major seedbed in Picea sitchensis – Tsuga heterophylla forests; therefore, the interception and retention of seeds on these surfaces is a potential limitation on tree recruitment. The ability of log surfaces within Picea – Tsuga forests to retain needles and seeds was studied at Cascade Head Experimental Forest, Oregon. Moss- and litter-covered surfaces retained many (48–98%) of the seeds and needles placed on them, but rotten wood, sound wood, and bark of Tsuga heterophylla, Picea sitchensis, and Pseudotsuga menziesii retained few (0–8%). Examination of logs mapped in five Picea sitchensis – Tsuga heterophylla stands in Oregon and Washington indicated a mean projected log cover of 9.9%. Thin (<5 cm) and thick (>5 cm) moss mats were the most abundant log surfaces and covered 59 and 25% of the logs, respectively. Analysis of data on seedbed coverage, retentive characteristics, and seedbed-specific seedling survival indicated approximately 1% of a seed cohort would survive the 1st year on log surfaces.

Tree Seedlings on Logs in Picea‐Tsuga Forests of Oregon and Washington

Logs are the major seedbed for trees in coastal Picea sitchensis–Tsuga heterophylla forests. Field experiments were conducted at Cascade Head, Oregon, and Hoh River, Washington, to examine pathogens, predation, competition, and standing water as causes for this close seedling–log association. More seedlings survived on log blocks than on soil blocks, regardless of whether the blocks were raised or placed flush with the soil surface. Standing water was therefore an unlikely cause of the seedling–log association. Comparisons of plots protected from and exposed to predation revealed that predation was minor and of equal intensity on soils and logs. Sterilizing soils did not consistently increase seedling survival above controls. Clearing ground–layer vegetation from soil plots significantly increased the survival of conifer seedlings compared with that on uncleared soils. The seed penetration rates through moss mats indicated that <1% of the seedlings germinated within moss mats. Competition with herbs and mosses on the forest floor therefore appears to be responsible for the disproportionate number of tree seedlings found on logs. Recently fallen logs represent sites where competition is low enough for tree seedling recruitment within many Picea–Tsuga forests.

The influence of litter and humus accumulations and canopy openness on Piceasitchensis (Bong.) Carr. and Tsugaheterophylla (Raf.) Sarg. seedlings growing on logs

The influence of litter and humus accumulations on the surface of logs and canopy openness upon growth and survival of Piceasitchensis (Bong.) Carr. and Tsugaheterophylla (Raf.) Sarg. seedlings was tested experimentally at Cascade Head Experimental Forest, near Otis, Oregon. This was done by adding litter and humus to the surface of freshly fallen logs. Survival rates of both species increased asymptotically as litter accumulations on logs increased. Mean maximum survival was 58% for Picea and 34% for Tsuga. Picea seedling survival peaked when tree canopy cover ranged from 70 to 80% with lower survival at either higher or lower values. Tsuga survival was highest under closed canopies. Seedling growth increased as litter–humus accumulation and canopy openness increased.

The Higher Fungi of Oregon's Cascade Head Experimental Forest and Vicinity: I. The Genus Phaeocollybia (Agaricales) and Notes and Descriptions of Other Species in the Agaricales

The Higher Fungi of Oregon's Cascade Head Experimental Forest and Vicinity: I. The Genus Phaeocollybia (Agaricales) and Notes and Descriptions of Other Species in the Agaricales

The Higher Fungi of Oregon's Cascade Head Experimental Forest and Vicinity—I. The Genus Phaeocollybia (Agaricales) and Notes and Descriptions of Other Species in the Agaricales

The Higher Fungi of Oregon's Cascade Head Experimental Forest and Vicinity—I. The Genus Phaeocollybia (Agaricales) and Notes and Descriptions of Other Species in the Agaricales

Rainfall at Sea

DURING the winter 1969–1970 we installed an 8 inch tipping-bucket recording rain gauge on a large spar-buoy, Totem, located at 45° 04′ N latitude 124° 44′ W longitude. This is about 56 km west of Cascade Head, Oregon. The water caught in the gauge was retained on the buoy and measured at intervals of approximately 1 month. Four such measurements of total rain were collected between November 22,1969, and April 6, 1970. Table 1 gives the measured rainfall at the buoy for these four periods, as well as measured rainfall at selected sites on the Oregon coast. During two of the periods the rain gauge recording functioned properly and we were thus able to obtain a chronology of the rainfall.

Report of Committee on Evaporation And Transpiration, 1947–1948

For this report it was suggested that, if the committee members did not have current research progress to report, they might contribute their comments on the following topic: Gains in water content of soil or snow during rainless periods. The results are presented below.In some localities where fogs are prevalent, drip from the trees may be an important source of water for the soil when no precipitation is recorded in rain gage in a standard exposure. An outstanding example comes from the Cascade Head Field Station of the Pacific Northwest Forest Experiment Station, which is located close to the Oregon coast. During an aggregate of 142 foggy days, when the precipitation recorded in a, standard gage amounted to 25.19 inches, the average of the catch in three gages under a dense stand of sitka spruce and western hemlock 150 ft high, amounted to 35.42 inches. The excess of 11.23 inches, or 0.08 inch per day, resulted from fog drip from the trees.