In Western Africa, the growth of cities has led to natural resource pollution, especially air pollution. Urban forests play a key role in filtering atmospheric particles and pollutants through the canopy before reachi...In Western Africa, the growth of cities has led to natural resource pollution, especially air pollution. Urban forests play a key role in filtering atmospheric particles and pollutants through the canopy before reaching the soil. This study aims to quantify heavy metal fluxes in an urban forest in the district of Abidjan in order to assess its role in the protection of natural resources. A monitoring of wet deposition (throughfall and open field rain) and litterfall was carried out for six months in the urban forest of the National Floristic Center located in Abidjan, C<span style="white-space:nowrap;">?</span>te d’Ivoire. The results show that the soil of this urban forest is a ferralsol type characterized by a sandy-clay texture and a low load of coarse elements. The annual litterfall is estimated to 12.16 ± 0.71 t<span style="white-space:nowrap;">·</span>ha<sup>-1</sup><span style="white-space:nowrap;">·</span>yr<sup>-1</sup>, similar to other tropical forests. Annual quantities of rain and throughfall are in the range of the rainfall recorded in the district of Abidjan (2013 ± 152 and 1773 ± 51 mm). Chemical analyses showed that litter and rainfall contain Mn, Zn, Ni, Cr, Cd and Hg. Manganese and Zn are the most abundant elements and Hg the least abundant in both rainfall and litter. The main source of input of the heavy metals into the urban forest soil is associated with biological recycling through the litter. The litterfall contributes to metal fluxes in soil 10<sup>9</sup> times greater than metal fluxes carry by wet depositions (open field rain and throughfall). However, a detailed study of rainfall showed that the forest canopy constitutes a barrier for the transfer of heavy metal to urban soil. This is indicated by a decrease in heavy metal content from open field rain to throughfall. Consequently, this study recommends the creation and maintenance of urban forests to increase biomass canopy and improve atmospheric air quality for West African cities undergoing constant change and development.展开更多
To reveal the biological characteristics of urban forest soil and the effects of soil enzyme on soil fertility as well as the correlation between physicochemical properties and enzyme activities,44 urban forest soil p...To reveal the biological characteristics of urban forest soil and the effects of soil enzyme on soil fertility as well as the correlation between physicochemical properties and enzyme activities,44 urban forest soil profiles in Nanjing were investigated.Basic soil physicochemical properties and enzyme activities were analyzed in the laboratory.Hydrogen peroxidase,dehydrogenase,alkaline phosphatase,and cellulase were determined by potassium permanganate titration,TTC(C_(19)H_(15)N_(4)·Cl)colorimetry,phenyl phosphate dinatrium colorimetry,and anthrone colorimetry,respectively.The result showed that soil pH,organic carbon(C),and total nitrogen(N)had great effects on hydrogen peroxidase,dehydrogenase,and alkaline phosphatase activities in 0–20 cm thick soil.However,pH only had great effect on hydrogen peroxidase,dehydrogenase,and alkaline phosphatase activities in 20–40 cm thick soil.Hydrogen peroxidase,dehydrogenase,and alkaline phosphatase were important biological indicators for the fertility of urban forest soil.Both in 0–20 cmand 20–40 cmsoil,soil enzyme system(hydrogen peroxidase,dehydrogenase,alkaline phosphatase,and cellulase)had a close relationship with a combination of physicochemical indicators pH,organic C,total N,available K,available P,cation exchange capacity(CEC),and microbial biomass carbon(C_(mic)).The more soil enzyme activities there were,the higher the fertility of urban forest soil.展开更多
Urban forest soil infiltration, affected by various factors, is closely related with surface runoff. This paper studied the effect of urban forest types, vegetation configuration and soil properties on soil infiltrati...Urban forest soil infiltration, affected by various factors, is closely related with surface runoff. This paper studied the effect of urban forest types, vegetation configuration and soil properties on soil infiltration. In our study, 191 typical plots were sampled in Changchun City, China to investigate the soil infiltration characteristics of urban forest and its influencing factors. Our results showed that the steady infiltration rates of urban forest soil were highly variable. High variations in the final infiltration rates were observed for different vegetation patterns and compaction degrees. Trees with shrubs and grasses had the highest infiltration rate and trees with bare land had the lowest infiltration rate. In addition, our results showed that the soil infiltration rate decreased with an increase in the bulk density and with a reduction in the soil organic matter content and non-capillary porosity. The soil infiltration rate also had significantly positive relationships with the total porosity and saturated soil water content. Urban soil compaction contributed to low soil infiltration rates. To increase the infiltration rate and water storage volume of urban forest soil, proper techniques to minimize and mitigate soil compaction should be used. These findings can provide useful information for urban planners about how to maximize the water volume of urban forest soil and decrease urban instantaneous flooding.展开更多
Soil N transformations using the polyvinyl chloride (PVC) closed-top tube in situ incubation method were studied in Nanchang urban forests of the mid-subtropical region of China in different months of 2007. Four plo...Soil N transformations using the polyvinyl chloride (PVC) closed-top tube in situ incubation method were studied in Nanchang urban forests of the mid-subtropical region of China in different months of 2007. Four plots of 20 m × 20 m were established in four different plant communities that represented typical successional stages of forest development including shrubs, coniferous forest, mixed forest and broad- leaved forest. Average concentrations of soil NH4^+-N from January to December were not different among the four plant communities. The concentrations of soil NO3^--N and mineral N, and the annual rotes of ammonification, nitrification and net N-mineralization under the early successional shrub community and coniferous forest were generally lower than that of the late successional mixed and broad-leaved forests (p〈0.05). Similar differences among the plant communities were also shown in the relative nitrification index (NH4^+-N/NO3^--N) and relative nitrification intensity (nitrification rate/net N-mineralization rate). The annual net N-mineralization rate was increased from younger to older plant communities, from 15.1 and 41.4 kg.ha^-1.a^-1 under the shrubs and coniferous forest communities to 98.0 and 112.9 kg.ha^-1.a^-1 under the mixed and broad-leaved forests, respectively. Moreover, the high annual nitrification rates (50-70 kg.ha^-1.a^-1) and its end product, NO3-N (2.4-3.8 mg·kg^-1), under older plant communities could increase the potential risk of N loss. Additionally, the temporal patterns of the different soil N variables mentioned above varied with different plant community due to the combined affects of natural biological processes associated with forest maturation and urbanization. Our results indicated that urban forests are moving towards a state of"N saturation" (extremely niUification rate and NO3^--N content) as they mature.展开更多
As the process of urbanization advances across the country, so does the importance of urban forests, which include both trees and the soils in which they grow. Soil microbial biomass, which plays a critical role in nu...As the process of urbanization advances across the country, so does the importance of urban forests, which include both trees and the soils in which they grow. Soil microbial biomass, which plays a critical role in nutrient transformation in urban ecosystems, is affected by factors such as soil type and the availability of water, carbon, and nitrogen. The aim of this study was to characterize residual forest patches and open fields in residential areas in the City of Knoxville. A field study was conducted to investigate tree species diversity and determine spatial and temporal soil characteristics along an urban-to-rural gradient. Tree diversity did not differ significantly for residential urban and rural plots in Knoxville, Tennessee. Biologically, there was no indication that soils were affected by tree diversity, in terms of soil microbial biomass C/N along an urban-to-rural gradient in Knoxville residential plots. Rural soils did differ physically from urban soils, cation exchange capacity (CEC) and soil moisture content (GSM). Similarly, physical soil properties such as bulk density, both urban and rural sites were negatively correlated with tree diversity. Results indicate that although the urban-rural gradient is subject to urban environmental stressors, the urban ecosystem is resilient in maintaining the ecosystem functions of more natural systems.展开更多
文摘In Western Africa, the growth of cities has led to natural resource pollution, especially air pollution. Urban forests play a key role in filtering atmospheric particles and pollutants through the canopy before reaching the soil. This study aims to quantify heavy metal fluxes in an urban forest in the district of Abidjan in order to assess its role in the protection of natural resources. A monitoring of wet deposition (throughfall and open field rain) and litterfall was carried out for six months in the urban forest of the National Floristic Center located in Abidjan, C<span style="white-space:nowrap;">?</span>te d’Ivoire. The results show that the soil of this urban forest is a ferralsol type characterized by a sandy-clay texture and a low load of coarse elements. The annual litterfall is estimated to 12.16 ± 0.71 t<span style="white-space:nowrap;">·</span>ha<sup>-1</sup><span style="white-space:nowrap;">·</span>yr<sup>-1</sup>, similar to other tropical forests. Annual quantities of rain and throughfall are in the range of the rainfall recorded in the district of Abidjan (2013 ± 152 and 1773 ± 51 mm). Chemical analyses showed that litter and rainfall contain Mn, Zn, Ni, Cr, Cd and Hg. Manganese and Zn are the most abundant elements and Hg the least abundant in both rainfall and litter. The main source of input of the heavy metals into the urban forest soil is associated with biological recycling through the litter. The litterfall contributes to metal fluxes in soil 10<sup>9</sup> times greater than metal fluxes carry by wet depositions (open field rain and throughfall). However, a detailed study of rainfall showed that the forest canopy constitutes a barrier for the transfer of heavy metal to urban soil. This is indicated by a decrease in heavy metal content from open field rain to throughfall. Consequently, this study recommends the creation and maintenance of urban forests to increase biomass canopy and improve atmospheric air quality for West African cities undergoing constant change and development.
基金The research was funded by Introduce Abroad Advance Forestry Technology Plan(948 plan)of State Forestry Administration of China(Grant No.2005-4-17)Social Development Foundation of Jiangsu Province of China(Grant No.BS2007064)+1 种基金National“11th Five”Science and Technology support plan of Forestry of China(Grant No.2006BAD03A16)Natural Science Foundation of Jiangsu Province of China(Grant No.BK2001208).
文摘To reveal the biological characteristics of urban forest soil and the effects of soil enzyme on soil fertility as well as the correlation between physicochemical properties and enzyme activities,44 urban forest soil profiles in Nanjing were investigated.Basic soil physicochemical properties and enzyme activities were analyzed in the laboratory.Hydrogen peroxidase,dehydrogenase,alkaline phosphatase,and cellulase were determined by potassium permanganate titration,TTC(C_(19)H_(15)N_(4)·Cl)colorimetry,phenyl phosphate dinatrium colorimetry,and anthrone colorimetry,respectively.The result showed that soil pH,organic carbon(C),and total nitrogen(N)had great effects on hydrogen peroxidase,dehydrogenase,and alkaline phosphatase activities in 0–20 cm thick soil.However,pH only had great effect on hydrogen peroxidase,dehydrogenase,and alkaline phosphatase activities in 20–40 cm thick soil.Hydrogen peroxidase,dehydrogenase,and alkaline phosphatase were important biological indicators for the fertility of urban forest soil.Both in 0–20 cmand 20–40 cmsoil,soil enzyme system(hydrogen peroxidase,dehydrogenase,alkaline phosphatase,and cellulase)had a close relationship with a combination of physicochemical indicators pH,organic C,total N,available K,available P,cation exchange capacity(CEC),and microbial biomass carbon(C_(mic)).The more soil enzyme activities there were,the higher the fertility of urban forest soil.
基金Under the auspices of Excellent Young Scholars of Northeast Institute of Geography and Agroecology,Chinese Academy of Sciences(No.DLSYQ 13004)Chinese Academy of Sciences/State Administration of Foreign Experts Affairs International Partnership Program for Creative Research Teams(No.KZZD-EW-TZ-07-09)Strategic Priority Research Program of Chinese Academy of Sciences(No.KFZD-SW-302-03)
文摘Urban forest soil infiltration, affected by various factors, is closely related with surface runoff. This paper studied the effect of urban forest types, vegetation configuration and soil properties on soil infiltration. In our study, 191 typical plots were sampled in Changchun City, China to investigate the soil infiltration characteristics of urban forest and its influencing factors. Our results showed that the steady infiltration rates of urban forest soil were highly variable. High variations in the final infiltration rates were observed for different vegetation patterns and compaction degrees. Trees with shrubs and grasses had the highest infiltration rate and trees with bare land had the lowest infiltration rate. In addition, our results showed that the soil infiltration rate decreased with an increase in the bulk density and with a reduction in the soil organic matter content and non-capillary porosity. The soil infiltration rate also had significantly positive relationships with the total porosity and saturated soil water content. Urban soil compaction contributed to low soil infiltration rates. To increase the infiltration rate and water storage volume of urban forest soil, proper techniques to minimize and mitigate soil compaction should be used. These findings can provide useful information for urban planners about how to maximize the water volume of urban forest soil and decrease urban instantaneous flooding.
基金supported by grants from the National Natural Science Foundation of China (Nos. 30960311 &30600473)
文摘Soil N transformations using the polyvinyl chloride (PVC) closed-top tube in situ incubation method were studied in Nanchang urban forests of the mid-subtropical region of China in different months of 2007. Four plots of 20 m × 20 m were established in four different plant communities that represented typical successional stages of forest development including shrubs, coniferous forest, mixed forest and broad- leaved forest. Average concentrations of soil NH4^+-N from January to December were not different among the four plant communities. The concentrations of soil NO3^--N and mineral N, and the annual rotes of ammonification, nitrification and net N-mineralization under the early successional shrub community and coniferous forest were generally lower than that of the late successional mixed and broad-leaved forests (p〈0.05). Similar differences among the plant communities were also shown in the relative nitrification index (NH4^+-N/NO3^--N) and relative nitrification intensity (nitrification rate/net N-mineralization rate). The annual net N-mineralization rate was increased from younger to older plant communities, from 15.1 and 41.4 kg.ha^-1.a^-1 under the shrubs and coniferous forest communities to 98.0 and 112.9 kg.ha^-1.a^-1 under the mixed and broad-leaved forests, respectively. Moreover, the high annual nitrification rates (50-70 kg.ha^-1.a^-1) and its end product, NO3-N (2.4-3.8 mg·kg^-1), under older plant communities could increase the potential risk of N loss. Additionally, the temporal patterns of the different soil N variables mentioned above varied with different plant community due to the combined affects of natural biological processes associated with forest maturation and urbanization. Our results indicated that urban forests are moving towards a state of"N saturation" (extremely niUification rate and NO3^--N content) as they mature.
文摘As the process of urbanization advances across the country, so does the importance of urban forests, which include both trees and the soils in which they grow. Soil microbial biomass, which plays a critical role in nutrient transformation in urban ecosystems, is affected by factors such as soil type and the availability of water, carbon, and nitrogen. The aim of this study was to characterize residual forest patches and open fields in residential areas in the City of Knoxville. A field study was conducted to investigate tree species diversity and determine spatial and temporal soil characteristics along an urban-to-rural gradient. Tree diversity did not differ significantly for residential urban and rural plots in Knoxville, Tennessee. Biologically, there was no indication that soils were affected by tree diversity, in terms of soil microbial biomass C/N along an urban-to-rural gradient in Knoxville residential plots. Rural soils did differ physically from urban soils, cation exchange capacity (CEC) and soil moisture content (GSM). Similarly, physical soil properties such as bulk density, both urban and rural sites were negatively correlated with tree diversity. Results indicate that although the urban-rural gradient is subject to urban environmental stressors, the urban ecosystem is resilient in maintaining the ecosystem functions of more natural systems.