Using Soil Stable Isotopes, 13C and 15N, Properties for Interpreting Effects of Forest Understory Vegetation Removal on Nutrient Cycling

Özet

Öz Forest harvesting and understory vegetation management may disturb the ecological integrity of forest ecosystems. The aim of this study is to analyze the soil stable isotopes, d13C and d15N properties for interpreting effects of forest understory vegetation removal on nutrient cycling. The study utilized a previously established project where the understory vegetation was differentially controlled in Douglas-fir plantations located in the pacific coast of Oregon, USA. Treatments included levels of salmonberry (Rubus spectabilis Pursh) and herbaceous vegetation control. A control plot received no vegetation removal (DFC). On one of the plots, shrubs were completely removed, leaving only herbs and Douglas-fir (DFH). Another plot received complete removal of shrubs and herbs, leaving only Douglas-fir (DFO). Soil samples were collected on each plot at 5th and 15th year of the stand establishment. Soil were sub-sampled for separation of light (LF)- and heavy-fraction (HF) organic material. Stable isotopes 13C and 15N of the LF and HF were analyzed for their 13C and 15N stable isotope values. Total understory vegetation removal significantly enriched soil d15N on DFO sites (P < 0.09) at age 5 yr. The presence of understory vegetation had significant effects on organic matter decomposition and soil nutrient cycling.