In Moray, for instance, David I drew the troublesome district into his direct sphere through claiming of castles as royal property and the settling of English nobility explicitly loyal the king, and not local ties in mid-12th century. In spite of the fact that most historians agree that from the 11th century through the 13th marks at minimum a greater formalization of feudalistic hierarchical relationships and structures, the wholesale adoption of the classic manorial feudalism as an explanation for Scottish rural economy has been widely criticized. Barrell claims that unlike in England, where the Norman Conquest enabled the monarchy to redefine societal relationships through the major expropriation of native lords, Scotland was never conquered. Therefore, the settlers introduced into Scotland were on top of existing socio-economic structures forcing the new population to tread carefully over established practices. In addition, Susan Reynolds argued that land was not held as a grant from the king, but rather engaged in military service and paid taxes commiserate with their economic and societal standing. Another obstacle frequently used to limit the applicability of feudal terminology to Scotland during this period was the relative importance of pastoralism, especially in the Northern and Western Highlands, over sedentary farming. The inability to tie the peasantry to the land in much of Scotland, like in England, limited the lord's ability to extract economic resources and exert political control over from the peasantry. Significant inroads were being made in Scottish agricultural practices during the High Middle Ages. This can partly be attributed to the Medieval Warm Period. This climatic change resulted in warmer, drier conditions throughout Northern Europe. Farming in Scotland therefore could be expanded into higher altitudes that were previously too cold for agriculture and valleys that were prone to floods or marsh conditions. The expansion of agricultural production capability was accompanied by improvements in labor saving technologies that increased crop yields and pastoral output. These included the carruca-type plough, which was more effective at plowing tougher soil, improved animal harnesses that shortened the time required for clearance in woodlands, and water mills that “freed more time and concomitantly more labor... which could then be applied to other activities.” These factors in congruence directly led to the expansion of agriculture into new areas and the intensification of existing arable lands that increased annual yields and indirectly caused an increase in population. In practice, this expansion into new lands manifested itself in the form of assarts. Assarts were lands that were newly cultivated from land formerly considered ‘waste.’ There were several different versions of the expansion.