Vegetation near the soil.

no this is inconsequential. i'd continue to use a proper RH relative to temperature and not adjust for it whatsoever. a little more airflow near the trunk might help, but it really isn't a problem. the overall growth and health of the plant is more important. any roots will air prune. they won't develop exposed to light and air.

lower RH won't stop it. soil level RH is going to be higher regardless. Just pinch em off, can also burry that part of the stem so it grows roots vs branches. The little white bumps/warts/knots are potentional root sites.

no, bro. Its just roots trying to develop. The plant doesnt know feel where the soil ends

white lumps are perfectly normal for cannabis plants and is not a disease, deficiency or problem of any sort and does not require any treatment at all. The white bumps are where roots would grow from if your plant was to accumulated humus/compost or even fallen leaves, around the stem that cause dark and damp conditions favourable to inducing new root growth. Cannabis is an opportunistic plant and these secondary root formation (potential) sites demonstrate how she has adapted to boosting growth later in life by the possible accumulation of matter around her stem that would then allow her to boost her water and nutrient scavenging ability and increase her health and growing potential. Pretty smart indeed! What occurs is that basal cells programmed for root growth will accumulate near the base of the stem, they being the white lumps that have for now developed a hard crust as indicated by the white colour of the bumps. If the crusted over white bumps are softened from the moisture of accumulated matter around the stem and it buries the white lumps, roots will then burst forth from the white lumps to supplement the plants water and nutrient needs. Usually a single woody type of root will emerge from the white lumps rather than fibrous multi branched roots. Many people who have mulched their plants, especially outdoors, will be aware of this phenomenon.