The allocation is part of a more generic concept, that is, management. When you manage resources you must also allocate resources to services. Management instead,  is more generic and comprehends other tasks as well, for example, monitoring, service admission, fulfilment of the SLAs, etc.

Thanks Rafael Brundo Uriarte.

Dear Mohammad

the resource management includes : data gathering, resource discovery, choosing best resource and resource allocation.

the resource allocation is final level of a resource management strategy.

In a mathematical point of view, resource allocation is included in Resource management.