<Citation> <Acknowledgement> <Disclaimer> Griffiths, R. 2002. Chemical and biochemical characteristics of soils along transects in stands with different vegetation and successional characteristics in the Andrews Experimental Forest, 1996. Long-Term Ecological Research. Forest Science Data Bank, Corvallis, OR. [Database]. Available: http://andlter.forestry.oregonstate.edu/data/abstract.aspx?dbcode=SP021. Accessed 2024-11-21. Data were provided by the HJ Andrews Experimental Forest research program, funded by the National Science Foundation's Long-Term Ecological Research Program (DEB 2025755), US Forest Service Pacific Northwest Research Station, and Oregon State University. While substantial efforts are made to ensure the accuracy of data and documentation, complete accuracy of data sets cannot be guaranteed. All data are made available "as is". The Andrews LTER shall not be liable for damages resulting from any use or misinterpretation of data sets.
To better understand the effects vegetation has on forest soils, we established a number of sampling transects running from old-growth (OG) forests into stands with different vegetation or transects within different vegetation types without an OG component. Each transect was made up of 75 meter segments in both the OG and “treatment” stands. Soil samples and field observations were made at 5 meter-intervals along these segments. Where indicated, the OG portion of the transect acted as a pseudocontrol. The types of vegetation assemblages studied were: (1) a 26 year-old young stand (YS), (2) 6 sites showing normal to fast recovery (FAST) ranging in age from 29 to 36 years, (3) 5 sites showing slow recovery (SLOW) after clear-cutting ranging in age from 27 to 36 years, (4) 4 degraded (DEGRAD) sites ranging in age from 26 to 35 years, (5) 2 grass sites (GRASS), 26 years and undisturbed, and (6) a bracken fern site (FERN) aged at 26 years.
Of these, the DEGRAD, GRASS and FERN sites showed much higher levels of denitrification potential than the other sites suggesting that mineralized fixed nitrogen was being lost from these sites at higher rates than the other vegetation types. Ectomycorrhizal mats were also essentially absent from sites as well. The concentration of living roots was highest in the YS and GRASS sites. The lowest concentrations of labile or biologically active organic carbon as measured by laboratory respiration rates, was found in the DEGRAD sites. The lowest levels of mineralizable (labile) organic nitrogen were found in the FERN site. Litter depth was lowest in the YS and GRASS sites and highest in the FERN site. There were a number of differences found between FAST and SLOW sites that reflected the different NNP activities in these stands. The concentration of ectomycorrhizal mats was greater in the FAST stands. Additionally, litter depth, field respiration rates were all greatest in the FAST stands, all of these patterns would be expected from stands with greater NPP. The concentration of mineralizable nitrogen, extractable ammonium and denitrification potentials were all lowest in the FAST stands suggesting that more organic nitrogen is being cycled and utilized by the faster growing trees. The higher concentration of mycorrhizal mats in these sites could provide the mechanism for cycling organic nitrogen a more rapid rate that in the SLOW sites where they are not as numerous.
