Physical Setting

Area Occupied: 90.9 acres (36.8 hectares)
Stand Size:

Small, isolated stands.

Landscape Position:

Low concave slopes that retain moisture, and moist, cool, shady ravines.


Fertile, fine to loamy soils or groundwater-influenced soils.

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Rock Creek Park

This lush-looking forest is often found immediately upslope of the floodplains of streams on concave slopes. Soils in which the Basic Mesic Hardwood Forest grows tend to be deep because they are in places where soil is not very easily washed away. They also hold more moisture than soils on hilltops, ridgelines, or convex slopes. However, they are well drained, not saturated like the soils in the park’s Red Maple Seepage Swamp or (at times) the Tuliptree Small-Stream Floodplain Forest.

Soils in the Basic Mesic Hardwood Forest are relatively fertile because in many places they are underlain by bedrock rich in basic elements such as calcium and magnesium. Ecobit: Defining Terms: "Basic" and "Acidic" These rocks are typically igneous rocks that can be described as mafic—that is, full of dark minerals that are sources of calcium and magnesium such as biotite, hornblende, and pyroxene. Rocks in the park with these minerals include gabbro and tonalites that are rich in mafic minerals such as biotite, hornblende, and garnet.

These relatively fertile, well-drained soils are fairly uncommon in the park, found mostly west of where the Laurel Formation bedrock lies, on the opposite side of a geologic fault.

Occasionally, small patches of Basic Mesic Hardwood Forest can be found in the middle of areas that are otherwise underlain by acidic bedrock, such as the metasedimentary Laurel or Sykesville Formation (as seen in Battery Kemble Park). These may occur

  • where soils are influenced by unmapped blocks of basic igneous rock that were trapped in the acidic bedrock during its formation, or
  • where slope processes have transported nutrient-rich sediments downslope from areas of basic rock intrusions, or
  • where otherwise acidic soils receive calcium-rich groundwater that has percolated through basic rock on its gravity-led underground journey.

Exceptionally large trees may be a clue to enriched groundwater or soils.