Increasing cases of lake eutrophication globally have raised concerns among stakeholders,and particularly in China.Evaluating the causes of eutrophication in waterways is essential for effective pollution prevention a...Increasing cases of lake eutrophication globally have raised concerns among stakeholders,and particularly in China.Evaluating the causes of eutrophication in waterways is essential for effective pollution prevention and control.Xiao Xingkai Lake is part of and connected to Xingkai(Khanka)Lake,a boundary lake between China and Russia.In this study,we investigated the spatio-temporal variabilities in water quality(i.e.,dissolved oxygen(DO),total nitrogen(TN),total phosphorus(TP),chemical oxygen demand(CODMn)and ammonium-nitrogen(NH4+-N))in Xiao Xingkai Lake,from 2012 to 2014,after which a Trophic Level Index was used to evaluate trophic status,in addition to the factors influencing water quality variation in the lake.The DO,TN,TP,CODMn and NH4+-N concentrations were 0.44-15.57,0.16-5.11,0.01-0.45,0.16-48.31,and 0.19-0.78 mg/L,respectively.Compared to the Environmental Quality Standards for surface water(GB 3838-2002)in China,the lake transitioned to an oligotrophic status in 2013 and 2014 from a mesotrophic status in 2012,TN and TP concentrations were the key factors influencing water quality of Xiao Xingkai Lake.Non-para-metric test results showed that sampling time and sites had significant effects on water quality.Water quality was worse in summer and in tourism and aquaculture areas,followed by agricultural drainage areas.Furthermore,lake water trophic status fluctuated between medium eutrophic and light eutrophic status from September 2012 to September 2014,and was negatively correlated with water level.Water quality in tourism and aquaculture sites were medium eutrophic,while in agricultural areas were light eutrophic.According to the results,high water-level fluctuations and anthropogenic activities were the key factor driving variability in physicochemical parameters associated with water quality in Xiao Xingkai Lake.展开更多
Soil aggregate stability,as an important indicator of soil functions,may be affected by seasonal freezing and thawing(SFT)and land use in high cold and wet regions.Therefore,comprehensive understanding the effects of ...Soil aggregate stability,as an important indicator of soil functions,may be affected by seasonal freezing and thawing(SFT)and land use in high cold and wet regions.Therefore,comprehensive understanding the effects of SFT on aggregate stability in orchards during winter and spring is crucial to develop appropriate management strategies that can effectively alleviate the degradation of soil quality to ensure sustainable development of orchard ecosystems.To determine the mechanism of degradation in orchard soil quality,the effects of SFT on the stability of water-stable aggregates were examined in apple-pear orchards(Pyrus ussuriensis var.ovoidea)of four different ages(11,25,40,and 63 yr)on 0 to 5%slopes before freezing and after thawing from October 2015 to June 2016 in Longjing City,Yanbian Prefecture,Northeast China,involving a comparison of planted versus adjacent uncultivated lands(control).Soil samples were collected to investigate water-stable aggregate stability in three incremental soil layers(0–20,20–40 and 40–60 cm).In the same samples,iron oxide,organic matter,and clay contents of the soil were also determined.Results showed that the destructive influences of SFT on water-stable aggregates were more pronounced with the increased orchards ages,and SFT exerted severe effects on water-stable aggregates of older orchards(40 and 63 yr)than juvenile orchards.Undergoing SFT,the soil instability index and the percentage of aggregate destruction increased by mean 0.15 mm and 1.86%,the degree of aggregation decreased by mean 1.32%,and the erosion resistance weakened,which consequently led to aggregate stability decreased.In addition,soil free,amorphous,and crystalline iron oxide as well as soil organic matter and clay contents are all important factors affecting the stability of water-stable aggregates,and their changes in their contents were consistent with those in the stability of water-stable aggregates.The results of this study suggest that long-term planting fruit trees can exacerbate the damaging effects of SFT on aggregate stability and further soil erosion increases and nutrient losses in an orchard,which hider sustainable use of soil and the productivity orchards.展开更多
基金Under the auspices of the National Natural Science Foundation of China(No.41771120,41771550)the National Basic Research Program of China(No.2012CB956100)。
文摘Increasing cases of lake eutrophication globally have raised concerns among stakeholders,and particularly in China.Evaluating the causes of eutrophication in waterways is essential for effective pollution prevention and control.Xiao Xingkai Lake is part of and connected to Xingkai(Khanka)Lake,a boundary lake between China and Russia.In this study,we investigated the spatio-temporal variabilities in water quality(i.e.,dissolved oxygen(DO),total nitrogen(TN),total phosphorus(TP),chemical oxygen demand(CODMn)and ammonium-nitrogen(NH4+-N))in Xiao Xingkai Lake,from 2012 to 2014,after which a Trophic Level Index was used to evaluate trophic status,in addition to the factors influencing water quality variation in the lake.The DO,TN,TP,CODMn and NH4+-N concentrations were 0.44-15.57,0.16-5.11,0.01-0.45,0.16-48.31,and 0.19-0.78 mg/L,respectively.Compared to the Environmental Quality Standards for surface water(GB 3838-2002)in China,the lake transitioned to an oligotrophic status in 2013 and 2014 from a mesotrophic status in 2012,TN and TP concentrations were the key factors influencing water quality of Xiao Xingkai Lake.Non-para-metric test results showed that sampling time and sites had significant effects on water quality.Water quality was worse in summer and in tourism and aquaculture areas,followed by agricultural drainage areas.Furthermore,lake water trophic status fluctuated between medium eutrophic and light eutrophic status from September 2012 to September 2014,and was negatively correlated with water level.Water quality in tourism and aquaculture sites were medium eutrophic,while in agricultural areas were light eutrophic.According to the results,high water-level fluctuations and anthropogenic activities were the key factor driving variability in physicochemical parameters associated with water quality in Xiao Xingkai Lake.
基金Under the auspices of National Natural Science Foundation of China(No.31460117,41877024)。
文摘Soil aggregate stability,as an important indicator of soil functions,may be affected by seasonal freezing and thawing(SFT)and land use in high cold and wet regions.Therefore,comprehensive understanding the effects of SFT on aggregate stability in orchards during winter and spring is crucial to develop appropriate management strategies that can effectively alleviate the degradation of soil quality to ensure sustainable development of orchard ecosystems.To determine the mechanism of degradation in orchard soil quality,the effects of SFT on the stability of water-stable aggregates were examined in apple-pear orchards(Pyrus ussuriensis var.ovoidea)of four different ages(11,25,40,and 63 yr)on 0 to 5%slopes before freezing and after thawing from October 2015 to June 2016 in Longjing City,Yanbian Prefecture,Northeast China,involving a comparison of planted versus adjacent uncultivated lands(control).Soil samples were collected to investigate water-stable aggregate stability in three incremental soil layers(0–20,20–40 and 40–60 cm).In the same samples,iron oxide,organic matter,and clay contents of the soil were also determined.Results showed that the destructive influences of SFT on water-stable aggregates were more pronounced with the increased orchards ages,and SFT exerted severe effects on water-stable aggregates of older orchards(40 and 63 yr)than juvenile orchards.Undergoing SFT,the soil instability index and the percentage of aggregate destruction increased by mean 0.15 mm and 1.86%,the degree of aggregation decreased by mean 1.32%,and the erosion resistance weakened,which consequently led to aggregate stability decreased.In addition,soil free,amorphous,and crystalline iron oxide as well as soil organic matter and clay contents are all important factors affecting the stability of water-stable aggregates,and their changes in their contents were consistent with those in the stability of water-stable aggregates.The results of this study suggest that long-term planting fruit trees can exacerbate the damaging effects of SFT on aggregate stability and further soil erosion increases and nutrient losses in an orchard,which hider sustainable use of soil and the productivity orchards.
