Assessing fine-root biomass and production in a Scots pine stand - comparison of soil core and root ingrowth core methods

Soil core and root ingrowth core methods for assessing fine-root (< 2 mm) b iomass and production were compared in a 38-year-old Scots pine (Pinus sylv estris L) stand in eastern Finland. 140 soil cores and 114 ingrowth cores w ere taken from two mineral soil layers (0-10 cm and 10-30 cm) during 1985-1 988. Seasonal changes in root biomass (including both Scots pine and unders torey roots) and necromass were used for calculating fine-root production. The Scots pine fine-root biomass averaged annually 143 g/m(2) and 217 g/m(2 ) in the upper mineral soil layer, and 118 g/m(2) and 66 g/m(2) in the lowe r layer of soil cores and ingrowth cores, respectively. The fine-root necro mass averaged annually 601 g/m(2) and 311 g/m(2) in the upper mineral soil layer, and 196 g/m(2) and 159 g/m(2) in the lower layer of soil cores and i ngrowth cores, respectively. The annual fine-root production in a Scots pin e stand in the 30 cm thick mineral soil layer, varied between 370-1630 g/m( 2) in soil cores and between 210 - 490 g/m(2) in ingrowth cores during thre e years. The annual production calculated for Scots pine fine roots, varied between 330-950 g/m(2) in soil cores and between 110 - 610 g/m(2) in ingro wth cores. The horizontal and vertical variation in fine-root biomass was s maller in soil cores than in ingrowth cores. Roots in soil cores were in th e natural dynamic state, while the roots in the ingrowth cores were still e xpanding both horizontally and vertically. The annual production of fine-ro ot biomass in the Scots pine stand was less in root ingrowth cores than in soil cores. During the third year, the fine-root biomass production of Scot s pine, when calculated by the ingrowth core method, was similar to that ca lculated by the soil core method. Both techniques have sources of error. In this research the sampling interval in the soil core method was 6-8 weeks, and thus root growth and death between sampling dates could not be accurat ely estimated. In the ingrowth core method, fine roots were still growing i nto the mesh bags. In Finnish conditions, after more than three growing sea sons, roots in the ingrowth cores can be compared with those in the surroun ding soil. The soil core method can be used for studying both the annual an d seasonal biomass variations. For estimation of production, sampling shoul d be done at short intervals. The ingrowth core method is more suitable for estimating the potential of annual fine-root production between different site types.