Re-Evaluating the Role of a Minor Nutrient in the Productivity and Composition of Northern Hardwood Forests.

Natural gradient studies and nutrient addition experiments show that northern hardwood forests in northeastern North America are responsive to base cation nutrients such as calcium and magnesium. However, responses are species-specific. Sugar maple is responsive to calcium while American beech is indifferent and black cherry may respond negatively to calcium additions. Depending on species composition, stand productivity may or may not be responsive. Nutrient limitations may not always express themselves in as a growth response. Photosynthetic and water use efficiency, seedling germination and survival, and resistance to damage by episodes of insect outbreaks or severe weather are affected by calcium nutrition. Interactions among nutrients or between nutrients and other elements complicate assessment of the role of minor nutrients such as calcium. Magnesium is another essential nutrient whose availability usually co-varies with calcium. Depending on geologic parent materials and primary mineral stoichiometry, different parts of the region may be more or less susceptible to calcium versus magnesium limitation. Aluminum is a non-nutrient whose availability interferes with base cation uptake. Manganese is an essential trace nutrient but may act antagonistically to base cation nutrition when in high concentrations. Future forest soil research will need to take a closer look at interactions between nutrients, between species, and among multiple processes when assessing the potential for nutrient limitations.