Urbanization has significantly altered water temperature and vegetation in urban watersheds. In order to understand the control of temperature and sources on organic carbon/nutrients release or decomposition, dried leaves of pine, elm, willow, grape vine, silver maple and red maple and algae were leached at 4 and 20ºC for 90 hours, and the leachates were then decomposed at the two temperatures for 252 hours. 

Results/Conclusions

The results show that, dissolved organic carbon (DOC) of all samples increased during leaching process and then decreased during decomposition; the rates of leaching and decomposition decreased with increasing time of incubation, and temperature significantly enhanced the leaching and decomposition rates.   The changes in total dissolved nitrogen (TDN) and phosphorus (TDP) were similar to that of DOC.  But, loss of TDN was observed during late stage of leaching, and TDN was all in organic form except for the algae, suggesting likelihood of denitrification.  In contrast, TDP experienced minor change during decomposition process, and soluble reactive phosphorus (SRP) was a more important form than dissolved organic phosphorus (DOP).  The ratio of TDN to TDP was less than 1 for all the leaf samples, suggesting relative enrichment of phosphorus relative to nitrogen during the processes.  Among the samples, silver maple and red maple were highest in the yields of DOC at the end of leaching with 20ºC (approximately 112 mg g^-1), followed by grape vine and willow (72-77 mg g^-1), elm and algae (21-29 mg g^-1), and the pine had the lowest value (5 mg g^-1); the highest yield of TDN was observed in algal sample at 4ºC.   During the decomposition period, approximately 70% of DOC from algae and elm were lost at 20ºC, and the amount decreased along willow, silver maple, grape vine and red maple; only <20% of DOC was lost at 4ºC.  Flocculation of dissolved organic matter was likely one of the most important mechanisms for the DOC loss during the decomposition process.   Changes in temperature and vegetation due to urbanization likely affect organic matter and nutrient export from urban watershed.