Lu Xianguo

Distribution characteristics of dissolved organic carbon in annular wetland soil-water solutions through soil profiles in the Sanjiang Plain,Northeast China

Overwhelming evidence reveals that concentrations of dissolved organic carbon (DOC) have increased in streams which brings negative environmental impacts. DOC in stream flow is mainly originated from soil-water solutions of watershed. Wetlands prove to be the most sensitive areas as an important DOC reserve between terrestrial and fluvial biogeosystems. This reported study was focused on the distribution characteristics and the controlling factors of DOC in soil-water solutions of annular wetland, i.e., a dishing wetland and a forest wetland together, in the Sanjiang Plain, Northeast China. The results indicate that DOC concentrations in soil-water solutions decreased and then increased with increasing soil depth in the annular wetland. In the upper soil layers of 0-10 cm and 10-20 cm, DOC concentrations in soil-water solutions linearly increased from edge to center of the annular wetland (R2 = 0.3122 and R2 = 0.443). The distribution variations were intimately linked to DOC production and utilization and DOC transport processes in annular wetland soil-water solutions. The concentrations of total organic carbon (TOC), total carbon (TC) and Fe(II), DOC mobility and continuous vertical and lateral flow affected the distribution variations of DOC in soil-water solutions. The correlation coefficients between DOC concentrations and TOC, TC and Fe(II) were 0.974, 0.813 and 0.753 respectively. These distribution characteristics suggested a systematic response of the distribution variations of DOC in annular wetland soil-water solutions to the geometry of closed depressions on a scale of small catchments. However, the DOC in soil pore water of the annular wetland may be the potential source of DOC to stream flow on watershed scale. These observations also implied the fragmentation of wetland landscape could bring the spatial-temporal variations of DOC distribution and exports, which would bring negative environmental impacts in watersheds of the Sanjiang Plain.

Influence of environment and substrate quality on the decomposition of wetland plant root in the Sanjiang Plain, Northeast China.

The litterbag method was used to study the decomposition of wetland plant root in three wetlands along a water level gradient in the Sanjiang Plain, Northeast China. These wetlands are Calamagrostis angustifolia (C.aa), Carex meyeriana (C.ma) and Carex lasiocarpa (C.la). The objective of our study is to evaluate the influence of environment and substrate quality on decomposition rates in the three wetlands. Calico material was used as a standard substrate to evaluate environmental influences. Roots native to each wetland were used to evaluate decomposition dynamics and substrate quality influences. Calico mass loss was statistically different among the three wetlands in the upper soil profile (0-10 cm) and in the lower depth range (10-20 cm). Hydrology, temperature and pH all influence calico decomposition rates in different ways at different depths of the soil profiles. The decomposition rates of native roots declined differentially with the increase of depth in the soil profiles. The mass loss of native roots showed a statistical decrease among the three wetlands in the upper soil profile (0-10 cm) and in the lower depth range (10-20 cm) as C.ma wetland > C.aa wetland > C.la wetland. Both the C:P ratio and N:P ratio were positively interrelated with decomposition rates. Decomposition rates were negatively related to initial P concentration in all three wetlands, indicating that P concentration seems to be an important factor controlling the litter loss.

Early-stage litter decomposition and its influencing factors in the wetland of the Sanjiang Plain, China

Abstract Using the litter bag technique, the decomposition rates and their influencing factors were studied by investigating three wetland macrophytes, Calamagrostics angustifolia, Carex meyeriana and Carex lasiocapa, in Sanjiang Plain, Northeast China. It was revealed that C. lasiocapa lost 28.91% of its weight, C. angustifolia lost 31.98% and C. meyeriana lost 32.99% after 164 days. Another finding was that the amount of organic carbon in the litter of C. angustifolia and C. lasiocapa fluctuated, but continuously decreased in that of C. meyeriana. However, all the three types of litter released organic carbon. Nitrogen was released substantially from the litter of both C. angustifolia and C. meyeriana, but accumulated in the litter of C. lasiocapa. Phosphorus concentrations in all the three types of litter apparently decreased first and then slightly increased. Overall, P release was observed in all the three types of litter. The C/N and C/P ratios varied significantly in the decomposition process. The decomposition rates and nutrient content variations were simultaneously influenced by the quality of the litter as well as the environmental factors in the Sanjian Plain, but they were more strongly affected by the quality of the litter.

A study on marsh evapotranspiration in the Sanjiang plain

The Sanjiang Plain is situated in northeast China. It is one of the areas where marshes are distributed concentratedly and widely in China.Carex lasiocarpa marsh and the marsh withCarex lasiocarpa as dominative species are distributed widely. We choseCarex lasiocarpa marsh as observation object in 1990 and 1991. Marsh evapotranspiration includes transpiration of marsh plants and evaporation of water surface. We used evaporimeters to observe the water level, and calculated the water level amplitude. The evapotranspiration of the marsh is one or two times more than the evaporation of water surface in growing season. The larger the vegetation coverage, the greater the daily evapotranspiration. When the vegetation coverage of marsh is less than 10%, the daily evapotranspiration of marsh is close to the evaporation of water surface. The difference between the evapotranspiration of marsh and the evaporation of water surface in sunny days is more than that in cloudy days.

CUMULATIVE EFFECTS OF DIFFERENT CULTIVATING PATTERNS ON PROPERTIES OF ALBIC SOIL IN SANJIANG PLAIN

This paper studied the cumulative effects of different cultivating patterns on the properties of albic soils in the Sanjiang Plain using correlation analysis. The results showed that the physical and chemical properties of the albic soil changed greatly when it was cultivated as farmland. As for physical properties of the soil, bulk density and specific gravity increased gradually, the porosity and field capacity decreased gradually year by year, but they increased after being abandoned. As for chemical properties, pH increased, organic matter and other nutrients decreased with increasing of the cultivating years. For the albic soil cultivated with forage, the cumulative effects were apparently strengthened with the increase of cultivating years, especially for the bulk density, total porosity, capillary porosity and capillary moisture capacity. Moreover, fertilization also had great effects on the albic soil. Applying magnetism fertilizer improved the physical properties such as bulk density, soil moisture and porosity, raised the utilization rate of nitrogen and phosphorus fertilizer. Compared with nutrient fertilizer, utilization of the magnetism fertilizer made production increase by 5.9%–13.9%. At the same time, using organic material and loosing the albic layer could improve not only the physical, chemical and biological properties of the cultivating layer, but also the ill properties of the albic layer, thus making organic carbon and heavy fraction carbon contents increase, and biological activity increase obviously.

Wetlands in China: Feature, value and protection

The estimated total area of wetland in China is more than 25.9 million hectares including about 11.9 million hectares of marshes and bogs, 9.1 million hectares of lake and about 2.2 million hectares of coastal salt marshes and mudflats. The area of wetland is equivalent to 2.7% of the land surface. China also has 2.7 million hectares of shallow sea water (less 5m in depth at low tide). Marshes and bogs are equivalent 1.3% of the land surface. Only three provinces (regions)—Qinghai, Xizang (Tibet) and Heilongjiang — have a larger total area of marsh and bog. According to the structure, type and development of wetland in different river basins, wetland can be classified nine main regions. The experiments indicate that the coefficient of the marsh to regulate flood is similar to that of lakes. Wetlands occupy 17.8% of the Sanjiang Plain area, the annual carbon contribution is 0.78 × 104t. Carbon released from marsh soil return into atmosphere is 3.95 × 106t/a. At present there is a sharp contradiction between population growth and natural resources shortage, causing wetland to be exerted with huge pressures and serious threats.

Soil-surface CO2 fluxes in a Deyeuxia angustifolia wetland in Sanjiang Plain, China

In many temperate-zone ecosystems, seasonal changes in environmental and biological factors influence the dynamics and magnitude of surface–atmosphere exchange. Research was conducted between July and October 2001 to measure growing season surface-layer fluxes of CO2 in a Deyeuxia angustifolia dominated wetland on the Sanjiang Plain in northeastern China. Seasonal fluctuation and daily change in soil-surface CO2 fluxes were measured as well as the edaphic factors controlling CO2 fluxes. Soil-surface CO2 fluxes were measured with a closed-chamber system. The results revealed that there were both seasonal fluctuations and daily change in CO2 fluxes. The ranges of measured soil-surface CO2 flux were 0.208 – 1.265 g CO2m−2h−1. Soil-surface CO2 fluxes averaged 0.620 g CO2 m−2h−1. An analysis of several edaphic factors including soil temperature and soil moisture of the D. angustifolia wetland showed that there was a significant relationship between flux and temperature (R2 = 0.77).

Relationship between plant species diversity and patch characteristics in a marsh in the Sangjiang Plain, China–Using Yaluhe farm as an example

Abstract Based on Quick Bird satellite image data, the present study examined small-scale herbaceous community patches in the marsh of the Sanjiang Plain and measured patch characteristics such as the area, perimeter and shape by GPS. The coenological characteristics of the patches were investigated using quadrat method, and the vascular plant species were recorded using transect method. A total of 219 plant species were recorded, which represents 12.2% of the vascular flora in Heilogjiang Province. Our results showed that species number S correlated with patch area and perimeter; richness index (R) correlated with patch perimeter; Simpson index (D) correlated with patch area and perimeter area; Shannon-Wiener index (H′) correlated with patch area, perimeter and perimeter area; Evenness index (Jsw) correlated with perimeter area. Both S and R have significant difference between different size of patches. Plant diversity in the small-scale herbaceous communities tended to increase with the patch area and p...

The flood of the Nenjiang river and the Songhua river in 1998 and the comprehensive management of the river basins

In the summer of 1998, an exceptionally serious flood, with the characteristics of high water level, large volume of flow, long duration and serious losses caused by the disaster, occurred in the Nenjiang River basin and the Songhua River basin. Greater flood peak occurred three times in the trunk stream of the Nenjiang River for the floods occurred in its tributaries one after another. At Jiangqiao Hydrometric Station, the water level was 141.90 m and the rate of flow was 12 000 m3/s. The flood is ranged to a catastrophic one, which occurs once in 50 years. Ranged to a catastrophic flood at Qiqihar Hydrometric Station that occurs once in 400 years, its water level, 0.89 m higher than the former alltime highest, was 149.30 m and the corresponding rate of flow was 14 800 m3/s. The water level that exceeded the all-time highest lasted for 7 days. At Harbin Hydrometric Station, the water level, 0.59 m higher than the former all-time highest, was 120.89 m and the corresponding rate of flow was 17 400 m3/s. The water level that exceeded the all-time highest lasted for 9 to 10 days. The flood here is ranged to a catastrophic one, which occurs once in 150 years. The flood of the Nenjiang River damaged 456 × 104 ha of crops and 115 × 104 rooms and the direct loss of economy exceeded 40 billion yuan(RMB). The main reasons of the flood are great rainfall, long flood season, unreasonable land use, regional ecological environment degradation and lack of water control projects. It is obvious that the following measures are greatly needed: the comprehensive management of the river basins; the formulation of development planning of the river basins, especially the water control projects; the development of agriculture based on ecological security.

Carbon cycle of marsh in the Sanjiang plain

The Sanjiang Plain of China is a low plain. Its total area is 10.89×104 km2 and marsh area takes up 10.20%. Marsh is a kind of vegetation type with strong carbon-fixing ability among the terrestrial ecosystem and carbon cycle performing in the form of carbon dioxide. This paper discusses the fixation of atmospheric CO2 by marsh plant; the transfer of carbon from marsh to atmosphere; the change of CO2 and vertical transfer of CO2 near atmosphere of the earth; the carbon flow among marsh plants, soil and atmosphere. Some scientific data about the biological production, carbon content of marsh plants and the capacity for releasing and fixing are used to explain the carbon cycle of marsh in the Sanjiang Plain.