Seasonal patterns of fine root dynamics and their contribution to net primary production in hinoki cypress (Chamaecyparis obtusa) and konara oak (Quercus serrata) forests

Key message Fine root and litterfall are major contributor of NPP and fine root production may reflect forest productivity in a warm-temperate forest in Japan. Abstract Forest ecosystems play an important role as the major carbon sink on land, with fine root dynamics and litterfall representing major carbon fluxes. The objectives of this research were to estimate NPP including annual fine root production values, to investigate fine root dynamics and the relationships between above– and belowground organs in konara oak (Quercus serrata) and hinoki cypress (Chamaecyparis obtusa) forests. Litterfall was collected seasonally for 1 year from June 2013. The ingrowth core method and the sequential soil core method were applied with a root litterbag experiment to estimate fine root (< 2 mm) production (FRP), mortality (FRM), and decomposition (FRD) for 1 year (from 2013 to 2014), using the continuous inflow estimate method and the simplified decision matrix. The total NPP ranged from 8.2 to 13.9 (t ha− 1 yr− 1), and the sum of aboveground litterfall and FRP accounted for 60% of the total NPP on average, confirming the significance of above- and belowground litter for the forest NPP as a source of detritus for the decomposer system. In hinoki cypress stand, fine root biomass peaked in the end of winter while fine root necromass showed the highest peak in late summer. In konara oak stand, only very fine root (< 0.05 mm) biomass and necromass demonstrated significant seasonal patterns. The seasonal patterns of fine root production did not differ between forest types and root diameter classes. We found a possible relationship between above- and belowground production and fine root production tended to be high in productive forests. This study improves our understanding of different patterns of carbon dynamics between temperate broadleaved and coniferous forest ecosystems.

Root Mass and Elemental Concentrations in an Irish Oak Woodland

Fine roots (< 2 mm diameter) are key for nutrient and carbon cycling in forests but less well studied for oak than other European trees. To better understand controls on root mass and nutrient concentrations in oak stands, a study was conducted at Glendalough in Ireland. Roots were removed from soils and measured for biomass, length and nutrient concentrations along with soil nutrients. Fine root mass was 360 gm-2 and comparable to other oak stands. Whilst root N concentrations were high, P concentrations were low and N, P, K, Mg, but not C or Ca were at greater concentrations in fine roots compared to coarse (2-5 mm) roots. The root Ca:Al ratio suggested Al toxicity although this was less marked in organic-rich soils. Neither root mass nor root nutrient concentrations showed particularly strong correlations with soil nutrients or pH. Whilst this data agrees well with other similar studies, improved analysis by separating live and dead roots will further advance our understanding of controls on forest fine root dynamics.

An affordable, fully-automated minirhizotron system for observing fine-root dynamics

&lt;div&gt; &lt;div&gt; &lt;div&gt; &lt;p&gt;For the understanding of the carbon cycle in terrestrial ecosystems as well as of plant stress responses to drought and hypoxia, the study of fine root dynamics plays an important role. However, the number of relevant studies is still limited, which may be due, among other things, to the high costs of commercial minirhizotron systems. Here, we present an affordable (&lt;500 &amp;#8364;) and fully automated minirhizotron system, utilizing new developments in low-cost electronics and 3D-printing. The camera system is based on a Raspberry Pi and can be controlled by the user via a Python-based GUI. The open source character of the program also allows it to be adapted to the needs of the user or other requirements. The camera is controlled automatically by a stepper motor, which allows the precise recording of images at defined depths. The highest possible resolution is 3280 x 2464 pixels (8 MP) for an image area of about 2.5 cm x 2.5 cm, thus allowing the imaging of even root hairs and fungal hyphae. The structural components were manufactured using 3D printing. To protect against moisture, the camera and drive system are installed in a waterproof acrylic tube (60 mm diameter), which in turn is inserted into the rhizotron tubes (70 mm diameter) used in the field, making it possible to use the system in humid ecosystems.&lt;/p&gt; &lt;/div&gt; &lt;/div&gt; &lt;/div&gt;