[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].

Differential anatomical responses to elevated CO2 in saplings of four hardwood species.

To determine whether an elevated carbon dioxide concentration ([CO(2)]) can induce changes in the wood structure and stem radial growth in forest trees, we investigated the anatomical features of conduit cells and cambial activity in 4-year-old saplings of four deciduous broadleaved tree species - two ring-porous (Quercus mongolica and Kalopanax septemlobus) and two diffuse-porous species (Betula maximowicziana and Acer mono) - grown for three growing seasons in a free-air CO(2) enrichment system. Elevated [CO(2)] had no effects on vessels, growth and physiological traits of Q. mongolica, whereas tree height, photosynthesis and vessel area tended to increase in K. septemlobus. No effects of [CO(2)] on growth, physiological traits and vessels were seen in the two diffuse-porous woods. Elevated [CO(2)] increased larger vessels in all species, except B. maximowicziana and number of cambial cells in two ring-porous species. Our results showed that the vessel anatomy and radial stem growth of Q. mongolica, B. maximowicziana and A. mono were not affected by elevated [CO(2)], although vessel size frequency and cambial activity in Q. mongolica were altered. In contrast, changes in vessel anatomy and cambial activity were induced by elevated [CO(2)] in K. septemlobus. The different responses to elevated [CO(2)] suggest that the sensitivity of forest trees to CO(2) is species dependent.

Changes in petiole hydraulic properties and leaf water flow in birch and oak saplings in a CO2-enriched atmosphere.

Water relations in woody species are intimately related to xylem hydraulic properties. High CO(2) concentrations ([CO(2)]) generally decrease transpiration and stomatal conductance (g(s)), but there is little information about the effect of atmospheric [CO(2)] on xylem hydraulic properties. To determine the relationship between water flow and hydraulic structure at high [CO(2)], we investigated responses of sun and shade leaves of 4-year-old saplings of diffuse-porous Betula maximowicziana Regel and ring-porous Quercus mongolica Fisch. ex Ledeb. ssp. crispula (Blume) Menitsky grown on fertile brown forest soil or infertile volcanic ash soil and exposed to 500 micromol CO(2) mol(-1) for 3 years. Regardless of species and soil type, elevated [CO(2)] consistently decreased water flow (i.e., g(s) and leaf-specific hydraulic conductivity) and total vessel area of the petiole in sun leaves; however, it had no effect on these parameters in shade leaves, perhaps because g(s) of shade leaves was already low. Changes in water flow at elevated [CO(2)] were associated with changes in petiole hydraulic properties.

[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.

Needle life span, photosynthetic rate and nutrient concentration of Picea glehnii, P. jezoensis and P. abies planted on serpentine soil in northern Japan.

We investigated the adaptation of three spruce species (Picea glehnii Masters, P. jezoensis Carr. and P. abies Karst.) to growth in northern Japan on serpentine soils (characterized by high concentrations of heavy metals and Mg, a low Ca/Mg ratio and low fertility) and fertile brown forest soils. Among species, seedling survival on serpentine soil was highest in P. glehnii. Shoot growth of P. glehnii was similar whether grown on serpentine or brown forest soil, whereas shoot growth of the other species was significantly less on serpentine soil than on brown forest soil. On serpentine soil, needle life span of P. glehnii was at least 3 years longer than that of the other two species. Needle area per shoot of P. glehnii was significantly higher on serpentine soil than on brown forest soil up to a shoot age of 8 years. In all three species, light-saturated photosynthetic rate (Pmax) decreased with needle age independently of soil type. However, on serpentine soil, Pmax in P. glehnii was higher, particularly in older needles, than in the other species. Furthermore, on serpentine soil, needle concentrations of nitrogen and phosphorus were higher in P. glehnii than in the other species. We conclude that P. glehnii is better adapted to serpentine soil than P. jezoensis and P. abies at least in part because of its greater needle life span and higher needle nutrient concentrations.