A study on fine‐root dynamics in response to nutrient applications in a Norway spruce stand using the minirhizotron technique

Abstract

AbstractMinirhizotrons with high resolution were used to investigate how the fine‐root turnover rate is influenced by extra nitrogen input to a Norway spruce stand. The stand was subjected to repeated application of ammonium sulphate (NS) and nitrogen‐free fertilizers (V), the latter containing macro and micro nutrients other than nitrogen. Data were collected and analysed during a one‐year period, 3–4 years after the start of fertilizer additions.A significant interaction of data x treatment (P < 0.001) in root‐length production and mortality was found between treatments. However, the total production in the NS and V treated plots was not significantly higher than in the C plots. The annual net production (production minus mortality) was higher in NS than V plots, while net production in the V plots was lower than in the C plots. The NS and V treatments resulted in a higher total root‐length mortality than the C plots during the period of study. Winter root‐mortality was higher in the V plots than in the C and NS plots. No root‐length mortality occurred from June to August in the V plots, while root‐length mortality in the C and NS plots during this period was 56% and 55% of annual root mortality, respectively.The NS application increased the production of white roots while the V treatment decreased the mortality of white roots. The mortality of white roots during August 1991 to August 1992 in the V plots was only 8% of total fine root mortality compared with 30% in the C and 60% in the NS plots. The NS and V applications resulted in a larger root diameter than in the C plots.