The Longgan Lake is a shallow mesotrophic macrophyte-dominated lake. According to the high-resolution diatom research from its sediment core, the diatom community succession was built, and the total phosphorus (TP) an...The Longgan Lake is a shallow mesotrophic macrophyte-dominated lake. According to the high-resolution diatom research from its sediment core, the diatom community succession was built, and the total phosphorus (TP) and chlorophyll-a (Chl-a) concentration were quantitatively reconstructed for the past 2000 years, based on the diatom-TP and diatom-Chla transfer functions. The shifts of diatom assemblages also mirrored the developments of aquatic plant, reflecting the characters of aquatic ecosystem evolution. The inferred epilimnetic TP concentration fluctuated within a small range of 36 to 62μg/L, indicating the lake remained a relative stable mesotrophic status in the long historical period. The periodical variations of the diatom assemblage and trophic status suggest a mitigating function of shallow macrophyte-dominated lakes to nutrient input. The changes of lakes’ trophic status don’t linearly respond to the human disturbance in the catchment. The dynamics mechanism of phosphorus in macrophyte-dominated lakes, as inferred from diatoms, will provide a scientific foundation for the prediction of trophic status change in a shallow lake, as well as the lake ecological restoration and management decisions.展开更多
Wetland is the conjunction of lake and terrene where human activities are concentrated. From the viewpoints of material transport and cycling in the terrene-lake system, wetland is the buffer where sand and mud, heavy...Wetland is the conjunction of lake and terrene where human activities are concentrated. From the viewpoints of material transport and cycling in the terrene-lake system, wetland is the buffer where sand and mud, heavy metals, pollutants and nutrients are tarried. In this paper, we provide a case study based on the temporal and spatial distribution of elements in the Wangling River catchment, a small sub-catchment of Longgan Lake in the middle reaches of the Yangtze River. We have found that wetland can buffer major heavy metals such as Cr, Cu, etc. significantly, but has a little buffer function to some active elements such as Fe and Mn, which are always transported as solutions. Human activities not only influence the distribution of elements, but also weaken the buffer function of wetland. Intensive human activities in the Longgan Lake area in the past 70 years have been recorded in stream, wetland and lake sediments, especially the human activity events such as deforesting and reclaiming on a large scale in 1958 and the 1980’s. Human activities caused the increase of sedimentation rates since the 1950’s, as well as the increase of elements’ concentrations. The extensive use of fertilizers and pesticides since the 1960’s have led to the increase of total P concentrations. Increasing SO-2 emission accelerate the process of cation exchange in soil, and enhance the leaching of Mn out of soils. Permanent storing of water causes the soil gleyification that also intensifies the leaching of Mn. These are two major reasons for the obvious increase of manganese concentrations in recent 20 years in Longgan Lake. Intensive human activities since the 1950s’ have intensified the population in this region and thus destroyed the buffer function of wetland.展开更多
基金the Scientific Innovation Projects of Chinese Academy of Sciences(KZCX1-SW-12)andthe 973 projects(2002CB412300)
文摘The Longgan Lake is a shallow mesotrophic macrophyte-dominated lake. According to the high-resolution diatom research from its sediment core, the diatom community succession was built, and the total phosphorus (TP) and chlorophyll-a (Chl-a) concentration were quantitatively reconstructed for the past 2000 years, based on the diatom-TP and diatom-Chla transfer functions. The shifts of diatom assemblages also mirrored the developments of aquatic plant, reflecting the characters of aquatic ecosystem evolution. The inferred epilimnetic TP concentration fluctuated within a small range of 36 to 62μg/L, indicating the lake remained a relative stable mesotrophic status in the long historical period. The periodical variations of the diatom assemblage and trophic status suggest a mitigating function of shallow macrophyte-dominated lakes to nutrient input. The changes of lakes’ trophic status don’t linearly respond to the human disturbance in the catchment. The dynamics mechanism of phosphorus in macrophyte-dominated lakes, as inferred from diatoms, will provide a scientific foundation for the prediction of trophic status change in a shallow lake, as well as the lake ecological restoration and management decisions.
文摘Wetland is the conjunction of lake and terrene where human activities are concentrated. From the viewpoints of material transport and cycling in the terrene-lake system, wetland is the buffer where sand and mud, heavy metals, pollutants and nutrients are tarried. In this paper, we provide a case study based on the temporal and spatial distribution of elements in the Wangling River catchment, a small sub-catchment of Longgan Lake in the middle reaches of the Yangtze River. We have found that wetland can buffer major heavy metals such as Cr, Cu, etc. significantly, but has a little buffer function to some active elements such as Fe and Mn, which are always transported as solutions. Human activities not only influence the distribution of elements, but also weaken the buffer function of wetland. Intensive human activities in the Longgan Lake area in the past 70 years have been recorded in stream, wetland and lake sediments, especially the human activity events such as deforesting and reclaiming on a large scale in 1958 and the 1980’s. Human activities caused the increase of sedimentation rates since the 1950’s, as well as the increase of elements’ concentrations. The extensive use of fertilizers and pesticides since the 1960’s have led to the increase of total P concentrations. Increasing SO-2 emission accelerate the process of cation exchange in soil, and enhance the leaching of Mn out of soils. Permanent storing of water causes the soil gleyification that also intensifies the leaching of Mn. These are two major reasons for the obvious increase of manganese concentrations in recent 20 years in Longgan Lake. Intensive human activities since the 1950s’ have intensified the population in this region and thus destroyed the buffer function of wetland.
