You should have 30 samples each time to fulfil the central limit theorem. It is the true and final answer! :)

I am going to assume you are in USA, possibly in Montana. Most states have mapped soils by soil series found within the boundaries of the state. You also have a few National Forests, and sometimes they are mapped to more detail. S ome wetlands have organic soils, some mineral soils, some wetlands are depressional or isolated features that vary in depth and composition, others are more uniform, spread over broad areas. The soils mapping may help you to stratify your existing sample sites, and give you some added data of the variances within the soil series. The US Corps of a Engineers have their Delineation Manual for wetlands and added info on hydric soils. Understanding the soil series, definitive horizon depths, may have some importance on how to describe and sample these soils for specific criteria such as bulk density. Advice from a state or federal soil scientist who has mapped soils to hydric series may be helpful. Wetlands that have been disturbed or drained, farmed, etc. may still exhibit some wetland characteristics, but may not be representative as the undesturbed ones. (My lpad is acting up so must go)

Some wetlands as pecosins are high in organic and fibric materials, and difficult to get the sample core to be retained. Sometimes saturated or inundated samples don’t come out well with coring. A fishery biologist developed a sampling tool that would freeze the stream substrate materials so a frozen core could be extracted using a come along I think to help extract, and then the sample could be covered in paraffin if desired to maintain its structure. As far as past disturbance, we found that the old aerial photos may be helpful as well as LiDAR coverage can help locate linear indicators such as old drainage ditches or logging roads that would otherwise go unnoticed. Wetlands accumulate organic, so natural disturbances from fire, floods, etc. can either remove or add excess organic materials or sediments. Some wetlands within the floodplain may have buried organic features (histic epipedon). The describing details or soil hydric history needed for some wetlands may go to depths of 4 feet or more.