Individual-based measurement and analysis of root system development: case studies forLarix gmeliniitrees growing on the permafrost region in Siberia

Abstract

We present results of individual-based root system measurement and analysis applied for Larix gmelinii trees growing on the continuous permafrost region of central Siberia. The data of root excavation taken from the three stands were used for the analyses; young (26 years old), mature (105 years old), and uneven-aged over-mature stand (220 years old). In this article, we highlight two topics:(1) factors affecting spatio-temporal pattern of root system development, and (2) interactions between aboveground (i.e., crown) and belowground (i.e., root) competition. For the fi rst topic, the detailed observation of lateral roots was applied to one sample tree of the overmature stand. The tree constructed a superfi cial (<30 cm in depth) and rather asymmetric root system, and each lateral root expanded mainly into elevated mounds rather than depressed troughs. This indicated that spatial development of an individual root system was largely affected by microtopography (i.e., earth hummocks). For these lateral roots, elongation growth curves were reconstructed using annual-ring data, and annual growth rates and patterns were compared among them. The comparison suggested that temporal root system development is associated with differences in carbon allocation among the lateral roots. For the second topic, we examined relationships between individual crown projection area (CA) and horizontal rooting area (RA) for the sample trees of each stand. RA was almost equal to CA in the young stand, while RA was much larger (three or four times) than CA in the mature and overmature stands. Two measures of stand-level space occupation, crown area index (aboveground: CAI; sum of CAs per unit land area) and rooting area index (belowground: RAI; sum of RAs), were estimated in each stand. The estimates of RAI (1.3-1.8 m 2 m −2 ) exceeded unity in all stands. In contrast, CAI exceeded unity (1.3 m 2 m −2 ) only in the young stand, and was much smaller (<0.3 m 2 m −2 ) in the two older stands. These between-stand differences in RAI-CAI relationships suggest that intertree competition for both aboveground and belowground spaces occurred in the young stand, but only belowground competition still occurred in the two older stands. Based on this fi nding, we hypothesized that competition below the ground may become predominant as a stand ages in L. gmelinii forests. Methodological limitations of our analysis are also discussed, especially for the analysis using the two indices of space occupation (CAI, RAI).

Sap flow changes in relation to permafrost degradation under increasing precipitation in an eastern Siberian larch forest

“…According to a root excavation survey of Larix gmelinii undertaken in central Siberia (Kajimoto et al ., ), the majority of lateral roots expanded into elevated mounds of soil rather than depressed troughs when waterlogged soil conditions were persistent. The tamarack larch ( Larix laricina ) and black spruce ( Picea mariana ), other boreal conifer species distributed in Canada, also developed shallow root systems in response to waterlogged conditions, with tap roots aborted at the tip portions when the water table was high (Lieffers and Rothwell, ).…”

Root system traits of Norway spruce, Scots pine, and silver birch in mixed boreal forests: an analysis of root architecture, morphology, and anatomy

“…They also determine the actual extent of segregation, or overlap of the belowground influence areas of different trees (Kajimoto et al 2007). The configuration of parts of the root system within the influence area may deviate greatly between tree species and during the ontogeny of an individual (Fitter 1991, Hodge 2004, Hodge et al 2009).…”

Sampling Method and Tree-Age Affect Soil Organic C and N Contents in Larch Plantations

“…Under a deeper soil sampling depth, the SOC and SON estimates (storage and concentration) were accompanied by moderate SOC increases or sharper SON decreases from the 20-40 years to the >40 years age-group. Previous soil studies in larch forests were focused on the more dynamic surface soil (0-20 cm), which also contains the highest root density [39,40]. However, this focus may have overlooked the importance of deep soil, which is significant given that SOM and nutrient storage in deep soils are important for forest vegetation with deep root systems [41,42], such as the larch trees studied in this paper.…”