Decomposition of four species of leaf litter in response to nitrate manipulation

Input of leaf litter and other allochthonous debris constitute the biologicalenergy base of small watershed streams. The relationship of decomposition rate to nitrateinputs of a 3-4 fold magnitude was tested in three replicate experimental streams. Such amagnitude of nitrate inputs simulated possible input effects of nitrogen fertilization or logging,two common forest practices. At the levels tested, no significant increase in decompositionrate was observed on any of four litter species as a result of nitrate addition. Commonparameters measured included weight loss, changes in carbon quality, absolute changes innitrogen content, and microbial respiration measured as 0, consumption. Results were partiallyconfounded by growth of filamentous green algae during spring. As a result of chemical 0,demand or leaf pack envelopment by the decaying algal mat, //3 of the total 0, consumptionwas not related to litter decomposition.
Although not related to increases in nitrate concentration in water, decomposing litter didexhibit a twofold increase in nitrogen content following initial leaching. The mechanism ofthis increase, whether by biological or chemical means, remains uninvestigated.
Key words: Decomposition; lignin; litter; nitrate; respiration; Washington; weight loss.