[Profile nutrient distribution and sedimentary characteristics in typical marshes of Sanjiang Plain].

Profile distribution characteristics of organic carbon (C), total nitrogen (N), total phosphorus (P) and total sulfur (S) were studied in two typical marshes including Carex lasiocarpa marsh and Phragmites australis marsh in the Sanjiang Plain. Sedimentary characteristics of typical mashes were analyzed. The results showed that vertically these soil chemical elements also varied, showing obvious stratification and enrichment. In a soil profile, soil organic C under both vegetation communities gradually decreased; soil total N first increased and then decreased under both; total P under Carex lasiocarpa first decreased and then increased, whereas it decreased with the increasing depth under Carex lasiocarpa; total S was reduced with increasing depth under both marshes. Total N, total P and total S were all strongly correlated with soil organic C (P < 0.01); soil organic C was strongly correlated with bulk density (P < 0.01). Our study also illustrated that the vegetation types had different influences for organic C, total N, total P and total S of the marsh profiles. Environmental 137Cs and 210Pb dating techniques were applied to determine recent sedimentation rates, and the constant rate of supply (CRS) was applied to deduce the age of sediment core, and the results showed that the mean sedimentation rate was 0.33 cm x a(-1), and the sedimentation fluxes ranged 0.03-0.48 g x (cm2 x a)(-1) [Mean = 0.29 g x (cm2 x a) -1].

[Seasonal dynamics of hydrochemical characteristics of streams under different forest types].

Stream water samples under the Korean pine broad-leaved forest, spruce-fir forest, and larch plantation in Liangshui Nature Reserve of Xiaoxing' an Mountains were collected monthly from March to October 2006 to study the dynamic changes of their hydrochemical characteristics. The results indicated that the content of major cations in the streams was in the sequence of Ca2+ > Na+ > K+ > Mg2+, and that of anions was HCO3(-) > SO4(2-) > NO3(-) > Cl(-). The average content of Na+, Ca2+, Mg2+, Fe2+ and Fe3+ was in the order of spruce-fir forest > larch plantation > Korean pine broad-leaved forest, while that of K+ was in the order of larch plantation > spruce-fir forest > Korean pine broad-leaved forest. The average monthly content of anions in stream water was the highest under larch plantation.

[Profile distribution and accumulation characteristics of organic carbon and total nitrogen in typical marshes in Sanjiang Plain].

The study on the profile distribution and accumulation characteristics of organic carbon (C) and total nitrogen (N) in two typical marshes in Sanjiang Plain showed that on the sediment profiles of Carex lasiocarpa marsh and Phragmites communis marsh, there existed distinct deposition horizon and illuviation horizon. In deposition horizon (0-60 cm), the average contents of organic C and total N were about 96 and 184 g x kg(-1), and 7.4 and 17.6 g x kg(-1), respectively, while in illuviation horizon, they were at low level. The contents of organic C and total N were exponentially decreased with increasing depth, and had significant correlations with bulk density (P < 0.01). The organic C density was the highest at the depth of 20-40 cm. In the deposition horizon of the two marshes, the stocks of organic C and total N were 1.83 x 10(4) and 1.73 x 10(4) t x km(-2), and 1.45 x 10(3) and 1.67 x 10(3) t x km(-2), respectively, and at the depth of 0-100 cm, they were 2.86 x 10(4) and 2.62 x 10(4) t x km(-2), and 2.18 x 10(3) and 2.49 x 10(3) t x km(-2), respectively. Vegetation type had definite effects on the content and stock of organic C and total N in the marsh profiles.