Radial Growth and Anatomic Structure of the Trunk Wood of Healthyand Stag-Headed Larch Trees on Permafrost
Presented here are the results of radial growth dynamics and xylotomic structure along the trunk of healthy and stag-headed Dahurian larch trees (Larix gmelinii (Rupr.) Rupr.), growing in the even-aged forest stand (64°19′23″ N, 100°13′28″ E) on permafrost on a north-facing slope. Annual rings width, as well as tracheids' lumens and walls radial size were measured on 1/4, 1/2 and 3/4 of the trunks' height and directly near the top, for 25 intact and stag-headed trees. A negative gradient of the aforementioned parameters from root to top was discovered, that was especially evident in stag-headed trees. Annual rings on the upper part of the trunk has undergone anatomic modifications over the last 20 years: disturbance of the tracheids' order, thinning of walls of the earlier and late tracheids'. Using the climatic moving response functions of the radial growth it was found that the trees on north-facing slope suffer from water shortage from the end of May until the twenties of June. The presence of both stag-headed and healthy trees on the north-facing slope can be explained by a high variability of the soil's hydrothermal properties due to a high degree of the moss-lichens layer's tessellation. With time, the sensitivity of certain trees to a water shortage can lead to their tops drying out.