I would suggest a query with sub-queries as the source, but I am fearful
that it wouldn't work with your field names

SELECT Year, Location, ProdCategory, Sum(Pounds) asTotalPounds
FROM Pounds
GROUP BY Year, Location, ProdCategory

SELECT Year, Location, ProdCategory, Sum(Hours) asTotalHours
FROM Hours
GROUP BY Year, Location

Then using those two queries

SELECT P.Year,  P.Location, P.ProdCategory
, P.TotalPounds, H.TotalHours
FROM QueryOne as P INNER JOIN QueryTwo as H
On P.Year = H.Year
and P.Location = H.Location
and P.ProdCategory = H.ProdCategory

All in one if your field names and table names consist of only letters,
numbers, and underscore characters might be as follows.

SELECT P.Year,  P.Location, P.ProdCategory
, P.TotalPounds, H.TotalHours
FROM (
   SELECT Pounds.Year, Pounds.Location, Pounds.ProdCategory
   , Sum(Pounds.Pounds) asTotalPounds
    FROM Pounds
   GROUP BY Pounds.Year, Pounds.Location, Pounds.ProdCategory
    ) as P INNER JOIN
   (
   SELECT Hours.Year, Hours.Location, Hours.ProdCategory
   , Sum(Hours.Hours) asTotalHours
   FROM Hours
  GROUP BY Hours.Year, Hours.Location
   ) as H
On P.Year = H.Year
and P.Location = H.Location
and P.ProdCategory = H.ProdCategory