This paper presents improved algorithms for matroid-partitioning probl
ems, such as finding a maximum cardinality set of edges of a graph tha
t can be partitioned into k forests, and finding as many disjoint span
ning trees as possible. The notion of a clump in a matroid sum is intr
oduced, and efficient algorithms for clumps are presented. Application
s of these algorithms are given to problems arising in the study of th
e structural rigidity of graphs, the Shannon switching game, and other
s.