Song Chang-chun

Effects of water gradients on soil enzyme activity and active organic carbon composition under Carex lasiocarpa marsh

The responses of soil enzyme activity of freshwater marsh, microbial biomass carbon (MBC), dissolved organic carbon (DOC) and aboveground biomass to water gradients were studied with Carex lasiocarpa pot culture experiment. The relationships between soil enzyme activity and MBC, DOC and aboveground biomass were discussed. The water gradients were W1, 15 cm; W2, −5 cm; W3, −5–5 cm; W4, submerged. The results indicated that acid phosphatase, invertase and urease activities were decreased with the increase of water level, while catalase activity was increased with moisture content increasing. Drying-wetting alternation (W3) increased soil enzyme activities if compared with W1. MBC content followed the order of W3 > W1 > W2 > W4, and the activities of invertase, urease and catalase were significantly positively correlated with MBC (p W1 > W3 > W2, and the activities of urease and acid phosphatase were most significantly negatively correlated with DOC (p < 0.01). In addition, drying-wetting alternation promoted the growth of Carex lasiocarpa. When water submerged plants, the growth of Carex lasiocarpa was significantly inhibited. The aboveground biomass was positively related to soil enzyme activities. There were close relationships between the activities of invertase, urease and catalase and the growth situation of Carex lasiocarpa.

Sustainable agriculture development in saline-alkali soil area of Songnen Plain, Northeast China

There is great potential for agriculture in saline-alkali soil area in Songnen Plain, Northeast China. But the sustainable crop production in this area has been restricted by a few of main factors, such as less precipitation, higher evaporation and frequent drought, high salinity and alkalinity, high exchangeable sodium content and poor infiltration of the soil, and insufficiency and low availability in nutrition. It is also considered that there are a few of favorable conditions for agricultural development in this region, such as sufficient light and heat resources, rich ground water resources, plenty of manure produced by livestock, and so on. At the same time, scientific management and measurements have been employed; rational irrigation and drainage system has been established; reclamation, amendment and fertilization of soil, and suitable strategies of cropping practices have been made for the sustainable development of agriculture. Great progress has been made during 1996 – 2000.

Carbon dynamics of wetland in the Sanjiang plain

Methane (CH4) and carbon dioxide (CO2) emission was measured from mires in the Sanjiang Plain, Northeast China, by using a static chamber technique during free snow-covered periods. The seasonal mean emission of CH4 was 12.4mg/(m2·h) and the emission range of CO2 was 8.7–16.6g/(m2·d) (gross CO2 flux) during plant growth period. CO2 emission rate in the day was stronger than that at night, and the daily peak appears at 19:00. The mire plants in the Sanjiang Plain begin to sprout at the end of April. The aboveground biomass of the mire plants increased from zero to the peak from July to September and showed single peak form. The aboveground biomass of Carex lasiocarpa (464.8g/m2) was lower than that of Deyeuxia platyphylla (530.8g/m2), but the underground biomass was higher than that of Deyeuxia platyphylla. Gross CO2 flux showed the significance positive correlation relationship with plant biomass. Gross CO2 flux and CH4 emission were also correlated with soil temperature (0–5cm) and water temperature. However, the highest CH4 emission rate lagged behind the highest soil temperature in the root area during plant growth period. The data also indicated that wet and warm conditions during the early spring led to greater value of CH4 emission flux. Inundation is the necessary condition for the existence of methane bacteria, but there is no significant positive correlation between the inundation depth and CH4 emission rate in this region. Within the same growing season and under the same inundation condition, the variations of CH4 emission rate could be markedly different.

CENOZOIC VOLCANISM AND GEOTHERMAL RESOURCES IN NORTHEAST CHINA

This paper is concentrated on Cenozoic volcanism and geothermal resources in Northeast China. There are a lot of Cenozoic volcanoes, a large area of volcanic rocks, a large number of active faults and rich geothermal resources in Northeast China. The time and space characteristics of Cenozoic volcanism and the space distribution characters of hot springs and high geothermal flux regions in Northeast China are described and discussed on the basis of geological, geothermal, drilling and volcanological data. It is revealed that the hot springs and high geothermal flux regions are related to the Cenozoic volcanism, rifting and faulting in Northeast China. It is especially emphasized that the hot springs and high geothermal anomaly areas are controlled by active deep faults. It is proposed that the Cenozoic volcanism regions, rift basins, active fault belts, activated plate suture zones and large earthquake occurrence points are the best areas for prospecting geothermal resources. The geothermal resources in younger volcanic zones are richer than those in older volcanic belts. The hot springs and active or activated faults might be a very good clue for looking for geothermal resources.

Hydroponic uptake and distribution of nitrobenzene in Phragmites australis: potential for phytoremediation.

Phragmites australis was grown hydroponically in nutrient solutions containing nitrobenzene to examine the potential for treatment of contaminated waters through phytoremediation. The hydroponic solutions and plant tissue were sampled each day during the five day growth period and tested for nitrobenzene. Plant tissue analysis included both rhizome and shoot sections of the plant. The average half lives and disappearance rate of nitrobenzene in the nutrient solution was 1.85 days and 88.10%, respectively. The levels of nitrobenzene in rhizomes and shoots of Phragmites australis increased with higher exogenous concentrations. For the highest treatment, nitrobenzene measurements in the rhizome tissue were much higher than the plant shoots until the third day. Shoot sections initially showed elevated concentrations and then decreased. This variation is presumably due to the translocation of the target compound from the rhizomes to shoots. Our findings indicate that Phragmites australis removed nitrobenzene from the hydroponic solutions and accumulated the compound within the plant tissue. This activity makes Phragmites australis a good candidate species for the phytoremediation of nitrobenzene contaminated waters.Phragmites australis was grown hydroponically in nutrient solutions containing nitrobenzene to examine the potential for treatment of contaminated waters through phytoremediation. The hydroponic solutions and plant tissue were sampled each day during the five day growth period and tested for nitrobenzene. Plant tissue analysis included both rhizome and shoot sections of the plant. The average half lives and disappearance rate of nitrobenzene in the nutrient solution was 1.85 days and 88.10%, respectively. The levels of nitrobenzene in rhizomes and shoots of Phragmites australis increased with higher exogenous concentrations. For the highest treatment, nitrobenzene measurements in the rhizome tissue were much higher than the plant shoots until the third day. Shoot sections initially showed elevated concentrations and then decreased. This variation is presumably due to the translocation of the target compound from the rhizomes to shoots. Our findings indicate that Phragmites australis removed nitrobenzene from the hydroponic solutions and accumulated the compound within the plant tissue. This activity makes Phragmites australis a good candidate species for the phytoremediation of nitrobenzene contaminated waters.

Is Moss Stoichiometry Influenced by Microtopography in a Boreal Peatland of Northeast China

To examine the effects of microtopography on the stoichiometry of carbon (C), nitrogen (N) and phosphorus (P) in mosses along the hummock-hollow gradient in boreal peatlands, we investigated species-level C׃N, C׃P and N׃P ratios of five mosses (Sphagnum magellanicum, S. perichaetiale, S. palustre, S. girgensohnii and Aulacomnium palustre) in the hummocks, hollows and their intermediate zones, and then assessed community-level spatial patterns in a boreal ombrotrophic peatland of north of the Great Xing’an Mountain, Northeast China. The results show that at the species level, C׃N, C׃P and N׃P ratios of the selected Sphagnum mosses remained stable in the hummock-hollow complexes due to unchanged C, N and P concentrations, whereas the non-Sphagnum moss (A. palustre) in the hummocks and intermediate zones had lower P concentrations and thus greater C׃P ratios than that in the hollows. At the community level, moss N concentration and C׃N ratio remained constant along the hummock-hollow gradient, whereas hummocks and intermediate zones had higher community-level moss C׃P and N׃P ratios than hollows because of greater C and lower P concentrations. These findings imply that the effects of microtopography on moss C׃N׃P stoichiometry are scale-dependent and reveal spatial heterogeneity in C and nutrient dynamics. These results provide a more comprehensive understanding of biogeochemical cycles in boreal peatlands.

Coupling analyses of fragile eco-environment in the west of the Songnen Plain

The fragile eco-environment is a special type of ecosystem, its response to the change of environmental conditions is very susceptive. So it is rather prone to be disturbed under unfavorable conditions. Human activity has greatly changed the geo-chemical process in the ecosystem, thus caused a series of positive and negative effects. In the ecosystem, especially in the fragile eco-environment, different systems and regimes are interconnected and interdetermined. For the suntainable development of ecosystem and the protection and rational utilization of resources, it is of great importance to study these internal relationships and seek rational regulation and control measures. This paper takes the fragile eco-environment in the west of the Songnen Plain as an example. Based on the study of the topograph, physiognomy, soil, vegetation and their geographic distribution in the landscape, the paper explains the structure of the ecologic landscape and quantifies the ecologic geo-chemical processes under different landscape conditions. In addition, the paper also tries making coupling analyses of the ecologic succession and the landscape geochemical environment. And in the paper, some research results are given.

Genetic types and characteristics of ground ice in Northeast China

The southern limit of permafrost in northeast China oversteps that in the other regions of Eurasia by a few degrees of latitude. There are 11 types of ground ice found within the studied region, including vein ice, massive bedrock ice, lava caves ice and so on. The water for the formation of the ground ice comes from various sources: precipitation, surface water, soil water, and ground water. The ground ice types coexist with the surrounding environment. The correlation and distribution features of the original types of ground ice, their surrounding environments are analyzed for the theoretical study of ground ice formation, engineering control of hazards in ice-rich areas and the prediction of changing conditions.The southern limit of permafrost in northeast China oversteps that in the other regions of Eurasia by a few degrees of latitude. There are 11 types of ground ice found within the studied region, including vein ice, massive bedrock ice, lava caves ice and so on. The water for the formation of the ground ice comes from various sources: precipitation, surface water, soil water, and ground water. The ground ice types coexist with the surrounding environment. The correlation and distribution features of the original types of ground ice, their surrounding environments are analyzed for the theoretical study of ground ice formation, engineering control of hazards in ice-rich areas and the prediction of changing conditions.