Decomposition of Four Species of Leaf Litter in Response to Nitrate Manipulation

Triska, F. J.; Sedell, J. R.

Decomposition of Four Species of Leaf Litter in Response to Nitrate Manipulation

1976

Triska, F. J. | Sedell, J. R.

Input of leaf litter and other allochthonous debris constitute the biological energy base of small watershed streams. The relationship of decomposition rate to nitrate inputs of a 3—4 fold magnitude was tested in three replicate experimental streams. Such a magnitude of nitrate inputs simulated possible input effects of nitrogen fertilization or logging, two common forest practices. At the levels tested, no significant increase in decomposition rate was observed on any of four litter species as a result of nitrate addition. Common parameters measured included weight loss, changes in carbon quality, absolute changes in nitrogen content, and microbial respiration measured as O_2 consumption. Results were partially confounded by growth of filamentous green algae during spring. As a result of chemical O_2 demand or leaf pack envelopment by the decaying algal mat, °° of the total O_2 consumption was not related to litter decomposition. Although not related to increases in nitrate concentration in water, decomposing litter did exhibit a twofold increase in nitrogen content following initial leaching. The mechanism of this increase, whether by biological or chemical means, remains uninvestigated.

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