Precipitation and air temperature control the variations of dissolved organic matter along an altitudinal forest gradient, Gongga Mountains, China.

Dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) contribute significantly to C and N cycling in forest ecosystems. Little information is available on the variations in the DOC and DON concentrations and depositions in bulk and stand precipitation within forests along an altitudinal gradient. To determine the temporal variations in the DOC and DON concentrations and depositions in different forests and the spatial variations along the elevation gradient, the DOC and DON concentrations and depositions were measured in bulk precipitation, throughfall, and stemflow within three forest types, i.e., broadleaf forest (BLF), broadleaf-coniferous forest (BCF), and coniferous forest (CF), during the wet season (May to October) on Gongga Mountain, China, in 2015. The concentrations of bulk precipitation in BLF, BCF, and CF were 3.92, 4.04, and 2.65 mg L-1, respectively, for DOC and were 0.38, 0.26, and 0.29 mg L-1, respectively, for DON. BCF had the highest DOC deposition both in bulk precipitation (45.12 kg ha-1) and stand precipitation (98.52 kg ha-1), whereas the highest DON deposition was in BLF (3.62 kg ha-1 bulk precipitation and 4.11 kg ha-1 stand precipitation) during the study period. The meteorological conditions of precipitation and air temperature significantly influenced the dissolved organic matter (DOM) depositions along the elevation gradient. The leaf area index did not show any correlation with DOM depositions during the growing season.