marl is the upper most layer of soil.
marl is the upper most layer of soil.
what is the upper most layer of soil?
marl
in soil science, agriculture and gardening, hardpan or soil pan is a dense layer of soil, usually found below the uppermost topsoil layer. there are different types of hardpan, all sharing the general characteristic of being a distinct soil layer that is largely impervious to water. some hardpans are formed by deposits in the soil that fuse and bind the soil particles. these deposits can range from dissolved silica to matrices formed from iron oxides and calcium carbonate. others are man-made, such as hardpan formed by compaction from repeated plowing, particularly with moldboard plows, or by heavy traffic or pollution.
hardpan
the depth of the organic soil layer is one of the controls on permafrost, leading to a generalization of two domains in boreal forest: thick soil layer and thin soil layer. thick organic soil insulates the subsoil from warmer summer temperatures and allows for permafrost to develop. although permafrost keeps ground moist during winter, during summer months upper organic soil horizons will become desiccated. as average temperatures increase, permafrost is melting at a faster rate and, correspondingly, the length of the fire season is increasing. when the fire-free interval (ffi) is decreased, the loss of the sol may result in a domain change to a thin soil layer, leading to less carbon storage in the soil, greater fire vulnerability, and decreased permafrost. in black spruce forests, decreased ffi can ruin successional trajectories by opening the door for deciduous trees and shrubs to invade, which also further increases fire vulnerability.
fire and carbon cycling in boreal forests