The carbon （C）, nitrogen （N） and phosphorus （P） variations of a temperate wetland soil under continuous cultivation for 40 yr were determined and evaluated in the Sanjiang Plain, Northeast China. The results sho...The carbon （C）, nitrogen （N） and phosphorus （P） variations of a temperate wetland soil under continuous cultivation for 40 yr were determined and evaluated in the Sanjiang Plain, Northeast China. The results showed that the soil organic carbon （SOC） and total nitrogen （TN） contents in each soil layer decreased sharply after cultivation for 2-3 yr, and exhibited minor differences after cultivation for 11 yr, which showed an exponential decline curve with the increase of cultivation years. The reduction rates of carbon and nitrogen reserves were 14.79% and 28.53% yr^-1 at the initial reclamation stages of 2-3 yr and then decreased to 2.02-3.08% yr^-1 and 1.98-2.93% yr^-1 after cultivation for 20 yr, respectively. Soil total phosphorus （TP） reserves decreased within cultivation for 5 yr, and then gradually restored to the initial level after cultivation for 17 yr. Both SOC and TN could be restored slightly when the farmland was left fallow for 8 yr after reclamation for 11 yr, whereas TP had no significant difference. These results demonstrated that wetland cultivation was one of the most important factors influencing on the nutrient fate and reserves in soil, which could lead to the rapid nutrient release and slow restoration through abandon cultivation, therefore protective cultivation techniques preventing nutrients from loss should be immediately established after wetland reclamation.展开更多
Reclamation is one of the fastest-growing land use type developed in coastal areas and has caused degradation and loss of coastal wetlands as well as serious environmental problems. This paper was aimed at monitoring ...Reclamation is one of the fastest-growing land use type developed in coastal areas and has caused degradation and loss of coastal wetlands as well as serious environmental problems. This paper was aimed at monitoring the spatiotemporal patterns of coastal wetlands and reclamation in the Yangtze Estuary during the 1960s and 2015. Satellite images obtained from 1980 to 2015 and topography maps of the 1960 s were employed to extract changes of reclamation and coastal wetlands. Area-weight centroids were calculated to identify the movement trend of reclamation and coastal wetlands. The results show that from the 1960 s to 2015, the net area of natural wetlands declined by 574.3 km^2, while man-made wetlands and reclamation increased by 553.6 and 543.9 km^2, respectively. During the five study phases, the fastest areal change rate natural wetlands was –13.3 km^2/yr in the period of 1990–2000, and that of man-made areas was 24.7 km^2/yr in the same period, and the areal change rate of reclamation was 27.6 km^2/yr in the period of 2000–2010. Conversion of coastal wetlands mainly occurred in the Chongming Island, Changshu City and the east coast of Shanghai Municipality. Reclamation was common across coastal areas, and was mainly attributed to settlement and man-made wetlands in the Chongming Island, Lianyungang City and the east coast of Shanghai Municipality. Natural wetlands turned into farmlands and settlement, and man-made wetlands gained from reclamation of farmlands. The centroid of natural wetlands generally moved towards the sea, man-made wetlands expanded equally in all directions and inland, and the centroid of reclamation migrated toward Shanghai Municipality. Sea level rise, erosion-deposition changes, and reclamation activities together determine the dynamics of the Yangtze Estuary wetlands. However, reclamation activities for construction of ports, industries and aquaculture are the key causes for the dynamics. The results from this study on the dynamics of coastal wetlands and reclamation are valuable for local government to put forward sustainable land use and land development plans.展开更多
To evaluate the influence of wetland reclamation on vertical distribution of carbon and nitrogen in coastal wetland soils, we measured the soil organic carbon(SOC), soil total nitrogen(STN) and selected soil propertie...To evaluate the influence of wetland reclamation on vertical distribution of carbon and nitrogen in coastal wetland soils, we measured the soil organic carbon(SOC), soil total nitrogen(STN) and selected soil properties at five sampling plots(reed marsh, paddy field, corn field, forest land and oil-polluted wetland) in the Liaohe River estuary in September 2013. The results showed that reclamation significantly changed the contents of SOC and STN in the Liaohe River estuary(P < 0.001). The SOC concentrations were in the order: oil-polluted wetland > corn field > paddy field > forest land > reed marsh, with mean values of 52.17, 13.14, 11.46, 6.44 and 6.16 g/kg, respectively. STN followed a similar order as SOC, with mean values of 1351.14, 741.04, 632.32, 496.17 and 390.90 mg/kg, respectively. Interaction of reclamation types and soil depth had significant effects on SOC and STN, while soil depth had significant effects on SOC, but not on STN. The contents of SOC and STN were negatively correlated with pH and redox potential(Eh) in reed marsh and corn field, while the SOC and STN in paddy field had positive correlations with electrical conductivity(EC). Dissolved organic carbon(DOC), ammonium nitrogen(NH_4^+-N) and nitrate nitrogen(NO_3~–-N) were also significantly changed by human activities. NH_4^+-N and NO_3~–-N increased to different degrees, and forest land had the highest NO_3~–-N concentration and lowest DOC concentration, which could have been caused by differences in soil aeration and fertilization. Overall, the results indicate that reed harvest increased soil carbon and nitrogen release in the Liaohe River Estuary, while oil pollution significantly increased the SOC and STN; however, these cannot be used as indicators of soil fertility and quality because of the serious oil pollution.展开更多
Land cover change plays an essential role in the alternation of soils properties. By field investigation and applying satellite images, land cover information in the Shelihu wetland was carried out in an area of 2,819...Land cover change plays an essential role in the alternation of soils properties. By field investigation and applying satellite images, land cover information in the Shelihu wetland was carried out in an area of 2,819 hm2 in 1985, 1995, 2000, 2005, 2010 and 2011, respectively, in Horqin Sandy Land. A total of 57 soil sampling sites across Shelihu were chosen in wet meadow （CL0）, cropland （CL） and sandy land （SL） according to the spatial characteristics of water body change. Soil texture, organic carbon （SOC）, total nitrogen （TN） and total phosphorus （TP） contents, electrical conductivity （EC） and pH were measured at the soil depths of 0-10, 10-20 and 20-40 cm to examine the influence of agricultural conversion and continuous cultivation on soil properties. The results showed that the study area was covered by water body in 1985, which gradually declined afterwards and then reclaimed rapidly at a mean annual rate of 132.1 hm2/a from wet meadow to cropland since 1995. In 2011, water body was drained and the area was occupied by 10.8% of CL0, 76.9% of CL and 12.3% of SL. Large amounts of SOC, TN and TP were accumulated in the above depths in CL0. Soil in CL0 also had higher EC and silt and clay fractions, lower pH than in SL and CL. Soil in SL was seriously degraded with lower contents of SOC, TN and TP than in CL and CL0. SOC, TN content and EC in CL decreased with the increase of cultivation age, while pH showed a reverse trend with significance at plough horizon. The agricultural conversion in Shelihu was driven by the comprehensive factors of precipitation reduction, economic development and intense competitions for irrigation water. Continuous cultivation in this process is not sustainable because of SOC degradation and nutrient content reduction. The key point is that conventional tillage and removal of residuals induced further land degradation. Wetland reclamation for immediate economic interests led to greater costs in the long-term environmental restoration in Horqin Sandy Land.展开更多
The rapid development of mariculture in China in recent decades has satisfied people's demand of seafood, and has made a great contribution to economic development. However, mariculture has also caused some negati...The rapid development of mariculture in China in recent decades has satisfied people's demand of seafood, and has made a great contribution to economic development. However, mariculture has also caused some negative impacts on the eco-environment. By statistically analyzing national data(as well as data for four main provinces) regarding the mariculture area and cultivation species in China since reform and opening up, the historical evolution of mariculture during the past 40 years was analyzed, the driving factors related to policy, market and technology innovation were discussed, and the potential impacts of mariculture on the coastal eco-environment were also illustrated. The statistical results indicated that the maricultural area increased radically during the past 40 years, from 1979(116.47 × 10~3 ha) to 2012(2205.65 × 10~3 ha), with an increase of nearly 20-fold. Shandong Province represented the fastest-growing region, with an increase of 31-fold. Moreover, the cultivated species had gradually become diversified. Initially, shellfish and algae were major species, and then it developed to various species including fish, and currently shellfish and crustaceans were the major species. The development of mariculture was driven by government policies, market economy and technology innovation. Rapid development of mariculture also caused significantly adverse impacts on the eco-environment of the coastal regions. For example, the sea reclamation for mariculture decreased the area and function of coastal wetlands and the contaminants originating from mariculture destroyed the coastal aquatic environment. Fortunately, the implementation of ‘13 th Five-Year Fisheries Planning' is expected to help both improve the seafood quality and reduce the contamination in coastal aquatic environment. This current study will provide reference for management and structure adjustment of mariculture in the future.展开更多
基金supported by the National Natural Science Foundation of China(41071056)the Discovery Research Project of Chinese Academy of Sciences(KZCX2-YW-309)
文摘The carbon （C）, nitrogen （N） and phosphorus （P） variations of a temperate wetland soil under continuous cultivation for 40 yr were determined and evaluated in the Sanjiang Plain, Northeast China. The results showed that the soil organic carbon （SOC） and total nitrogen （TN） contents in each soil layer decreased sharply after cultivation for 2-3 yr, and exhibited minor differences after cultivation for 11 yr, which showed an exponential decline curve with the increase of cultivation years. The reduction rates of carbon and nitrogen reserves were 14.79% and 28.53% yr^-1 at the initial reclamation stages of 2-3 yr and then decreased to 2.02-3.08% yr^-1 and 1.98-2.93% yr^-1 after cultivation for 20 yr, respectively. Soil total phosphorus （TP） reserves decreased within cultivation for 5 yr, and then gradually restored to the initial level after cultivation for 17 yr. Both SOC and TN could be restored slightly when the farmland was left fallow for 8 yr after reclamation for 11 yr, whereas TP had no significant difference. These results demonstrated that wetland cultivation was one of the most important factors influencing on the nutrient fate and reserves in soil, which could lead to the rapid nutrient release and slow restoration through abandon cultivation, therefore protective cultivation techniques preventing nutrients from loss should be immediately established after wetland reclamation.
基金Under the auspices of National Program on Key Basic Research Project(No.2013CB430401)
文摘Reclamation is one of the fastest-growing land use type developed in coastal areas and has caused degradation and loss of coastal wetlands as well as serious environmental problems. This paper was aimed at monitoring the spatiotemporal patterns of coastal wetlands and reclamation in the Yangtze Estuary during the 1960s and 2015. Satellite images obtained from 1980 to 2015 and topography maps of the 1960 s were employed to extract changes of reclamation and coastal wetlands. Area-weight centroids were calculated to identify the movement trend of reclamation and coastal wetlands. The results show that from the 1960 s to 2015, the net area of natural wetlands declined by 574.3 km^2, while man-made wetlands and reclamation increased by 553.6 and 543.9 km^2, respectively. During the five study phases, the fastest areal change rate natural wetlands was –13.3 km^2/yr in the period of 1990–2000, and that of man-made areas was 24.7 km^2/yr in the same period, and the areal change rate of reclamation was 27.6 km^2/yr in the period of 2000–2010. Conversion of coastal wetlands mainly occurred in the Chongming Island, Changshu City and the east coast of Shanghai Municipality. Reclamation was common across coastal areas, and was mainly attributed to settlement and man-made wetlands in the Chongming Island, Lianyungang City and the east coast of Shanghai Municipality. Natural wetlands turned into farmlands and settlement, and man-made wetlands gained from reclamation of farmlands. The centroid of natural wetlands generally moved towards the sea, man-made wetlands expanded equally in all directions and inland, and the centroid of reclamation migrated toward Shanghai Municipality. Sea level rise, erosion-deposition changes, and reclamation activities together determine the dynamics of the Yangtze Estuary wetlands. However, reclamation activities for construction of ports, industries and aquaculture are the key causes for the dynamics. The results from this study on the dynamics of coastal wetlands and reclamation are valuable for local government to put forward sustainable land use and land development plans.
基金Under the auspices of National Basic Research Program of China(No.2012CB956100)National Natural Science Foundation of China(No.41301085)
文摘To evaluate the influence of wetland reclamation on vertical distribution of carbon and nitrogen in coastal wetland soils, we measured the soil organic carbon(SOC), soil total nitrogen(STN) and selected soil properties at five sampling plots(reed marsh, paddy field, corn field, forest land and oil-polluted wetland) in the Liaohe River estuary in September 2013. The results showed that reclamation significantly changed the contents of SOC and STN in the Liaohe River estuary(P < 0.001). The SOC concentrations were in the order: oil-polluted wetland > corn field > paddy field > forest land > reed marsh, with mean values of 52.17, 13.14, 11.46, 6.44 and 6.16 g/kg, respectively. STN followed a similar order as SOC, with mean values of 1351.14, 741.04, 632.32, 496.17 and 390.90 mg/kg, respectively. Interaction of reclamation types and soil depth had significant effects on SOC and STN, while soil depth had significant effects on SOC, but not on STN. The contents of SOC and STN were negatively correlated with pH and redox potential(Eh) in reed marsh and corn field, while the SOC and STN in paddy field had positive correlations with electrical conductivity(EC). Dissolved organic carbon(DOC), ammonium nitrogen(NH_4^+-N) and nitrate nitrogen(NO_3~–-N) were also significantly changed by human activities. NH_4^+-N and NO_3~–-N increased to different degrees, and forest land had the highest NO_3~–-N concentration and lowest DOC concentration, which could have been caused by differences in soil aeration and fertilization. Overall, the results indicate that reed harvest increased soil carbon and nitrogen release in the Liaohe River Estuary, while oil pollution significantly increased the SOC and STN; however, these cannot be used as indicators of soil fertility and quality because of the serious oil pollution.
基金funded by the National Natural Science Foundation of China (41071185,41171414)the National Science and Technology Support Program (2011BAC07B02)
文摘Land cover change plays an essential role in the alternation of soils properties. By field investigation and applying satellite images, land cover information in the Shelihu wetland was carried out in an area of 2,819 hm2 in 1985, 1995, 2000, 2005, 2010 and 2011, respectively, in Horqin Sandy Land. A total of 57 soil sampling sites across Shelihu were chosen in wet meadow （CL0）, cropland （CL） and sandy land （SL） according to the spatial characteristics of water body change. Soil texture, organic carbon （SOC）, total nitrogen （TN） and total phosphorus （TP） contents, electrical conductivity （EC） and pH were measured at the soil depths of 0-10, 10-20 and 20-40 cm to examine the influence of agricultural conversion and continuous cultivation on soil properties. The results showed that the study area was covered by water body in 1985, which gradually declined afterwards and then reclaimed rapidly at a mean annual rate of 132.1 hm2/a from wet meadow to cropland since 1995. In 2011, water body was drained and the area was occupied by 10.8% of CL0, 76.9% of CL and 12.3% of SL. Large amounts of SOC, TN and TP were accumulated in the above depths in CL0. Soil in CL0 also had higher EC and silt and clay fractions, lower pH than in SL and CL. Soil in SL was seriously degraded with lower contents of SOC, TN and TP than in CL and CL0. SOC, TN content and EC in CL decreased with the increase of cultivation age, while pH showed a reverse trend with significance at plough horizon. The agricultural conversion in Shelihu was driven by the comprehensive factors of precipitation reduction, economic development and intense competitions for irrigation water. Continuous cultivation in this process is not sustainable because of SOC degradation and nutrient content reduction. The key point is that conventional tillage and removal of residuals induced further land degradation. Wetland reclamation for immediate economic interests led to greater costs in the long-term environmental restoration in Horqin Sandy Land.
基金Under the auspices of National Key Basic Research Program of China(No.2013CB430401)National Key Research and Development Program of China(No.2016YFC0500404-4)Youth Innovation Promotion Association CAS(No.2017274)
文摘The rapid development of mariculture in China in recent decades has satisfied people's demand of seafood, and has made a great contribution to economic development. However, mariculture has also caused some negative impacts on the eco-environment. By statistically analyzing national data(as well as data for four main provinces) regarding the mariculture area and cultivation species in China since reform and opening up, the historical evolution of mariculture during the past 40 years was analyzed, the driving factors related to policy, market and technology innovation were discussed, and the potential impacts of mariculture on the coastal eco-environment were also illustrated. The statistical results indicated that the maricultural area increased radically during the past 40 years, from 1979(116.47 × 10~3 ha) to 2012(2205.65 × 10~3 ha), with an increase of nearly 20-fold. Shandong Province represented the fastest-growing region, with an increase of 31-fold. Moreover, the cultivated species had gradually become diversified. Initially, shellfish and algae were major species, and then it developed to various species including fish, and currently shellfish and crustaceans were the major species. The development of mariculture was driven by government policies, market economy and technology innovation. Rapid development of mariculture also caused significantly adverse impacts on the eco-environment of the coastal regions. For example, the sea reclamation for mariculture decreased the area and function of coastal wetlands and the contaminants originating from mariculture destroyed the coastal aquatic environment. Fortunately, the implementation of ‘13 th Five-Year Fisheries Planning' is expected to help both improve the seafood quality and reduce the contamination in coastal aquatic environment. This current study will provide reference for management and structure adjustment of mariculture in the future.
