What is the ruling on someone who experienced a wet dream during a wilderness trip and did not have enough water for a full ritual bath (ghusl), so he limited himself to washing the male organ and then performed tayammum (dry ablution)? Is that sufficient for purification, and are there any consequences?

If the available water is insufficient for ablution (wudu) or ritual bathing (ghusl (definition)), or if the person needs it for drinking or other necessities, then they may perform tayammum (definition) (dry ablution) and their prayer will be valid. This is based on the Almighty's saying: "So fear Allah as much as you are able," and the Prophet's (peace be upon him) saying: "You must use pure earth, for it will suffice you." However, if the water was immediately sufficient for ghusl and he did not perform it, then he must repeat the prayers, unless there was an excuse such as extremely cold weather.