## 5 Discussion
### Wildfire and Larch Dominance in the Permafrost  
Burned areas regularly include a mosaic of living tree clusters because of relief complexity which allows trees to survive stand-replacing fires. In addition, the larch itself is resistant to fires and can restore itself after consecutive fires (Figure 9a). That refugia serves as a seed source for larch regeneration. Moreover, already-ripe seeds in the mother canopy also supply the burns with seeds because the cones open in winter or spring. Wind and melt water spread the winged, light larch seeds into burned bare surfaces that are suitable for seeds rooting. Regeneration abundance is facilitated via soil enrichment with phosphorus, potassium, nitrogen, and other nutrients, as well as via improved soil aeration and drainage and a deeper active layer. Upper canopy elimination improves the light regime, which is important for the photophilic larch (Figure 11d). Larch trees can survive multiple fires. With a one-year lag after a fire, surviving trees experience increased growth (Figure 9c). Over time, larch growth on permafrost decreases due to the seasonal melting layer decrease caused by the growth of the moss and lichen matrix, a heat insulator, with consequent active layer shrinking. The growth of that matrix also decreases seedling establishment because the matrix traps larch seeds and prevents seed rooting. The decrease in nutrients supply also leads to growth decrease(Figure 9b). Larch trees fall into stagnation, awaiting the next fire that will be facilitated via fuel accumulation, dry weather, and increased warming-driven lightning ignitions. Thus, periodic fires determine the larch dominance within the permafrost zone. Fires formed the larch forest as a mosaic of semi, even-age stands at different phases of post-fire succession. We observed a contrasting response to fires in the continuous permafrost and at the southern lowland boundary of the larch range. In the first case, larch seedlings are typically vigorous and abundant (up to \(>\)500,000 per ha), while under the mother canopy, the regeneration number is two-three orders lower (Table 2). Alongside larch, birch (_Betula_ spp.) and alder (_Duschekia fruticosa_) also participate in regeneration, although more often within wind-sheltered relief features. Earlier, it was shown that burns also served as \"starting places\" for Siberian pine (_Pinus sibirica_) trees in climate-driven northward migration as well as for the other relatively less cold-tolerant species, e.g., _Abies sibirica_, _Pica obovata_[43]. Within the southern part of the larch range, larch regeneration is less successful; the number of seedlings is two orders lower than on the northern site (Tables 3 and 4). Even in the case of abundant regeneration, the majority of seedlings (up to 80%) are represented by hardwood species (Table 4). Amplified burning in the south may lead to the transformation of larch forests into grass and shrub communities within discontinuous and patched permafrost zones (Figure 12b). We suggested that permafrost melting potentially decreases larch-dominance by increasing the proportion of relatively southern species (e.g., birch and aspen) in the forests structure. Permafrost melting also leads to the formation of ponds and bogs as well as grass communities [44], although the geography and dynamics of these events needs more study. At the same time, in the southern highlands, larch is migrating into alpine tundra and increasing growth [25]. The other potential consequence of permafrost melting is substitution of _L. gmelinitii_ by _L. sibirica_ due to differences in fire adaptation strategies. Thus, _L. sibirica_ is protected against surface fires by thick bark that provides thermal isolation to living tissues while the roots are located in rather deep soil; whereas _L. gmelinitii_ has thinner bark since it is grows mostly within permafrost where the majority of mortality is caused via thermal damage to roots that are located within the thin active layer (up to 30 cm or less).