Climate change and food security are among the pressing challenges facing humanity in the 21</span><sup><span style="font-family:Verdana;">st</span></sup><span style="fo...Climate change and food security are among the pressing challenges facing humanity in the 21</span><sup><span style="font-family:Verdana;">st</span></sup><span style="font-family:Verdana;"> century. Soil organic carbon (SOC) stocks, total nitrogen (TN), texture, and bulk density (BD) are important soil properties, which control climate change. Three land use systems (smallholder </span></span><span style="font-family:Verdana;">farmlands</span><span style="font-family:Verdana;">, grazing land</span><span style="font-family:Verdana;">s</span><span style="font-family:Verdana;">, and forest lands) that coexist in the </span><span style="font-family:Verdana;">Bamenda Highlands (BH) influence ecosystem</span><span style="font-family:Verdana;"> services and induce soil degradation with the loss of SOC. The objective of this study was to evaluate the variation of SOC and some soil physicochemical properties as affected by the three land use systems (LUS). A total of 21 composite soil samples collected from 7 microclimatic zones of BH following “S” shape plots to the depth of 0 - 30 cm, were analysed for moisture content (MC), SOC, TN, BD, available phosphorus (Av.P), pH and texture. The results revealed that grazing land had the lowest mean sand content (40.79 ± 4.07). Mean MC, TN</span><span style="font-family:Verdana;"> and</span><span style="font-family:Verdana;"> SOC (%) content were significantly higher </span><span style="font-family:""><span style="font-family:Verdana;">(</span><i><span style="font-family:Verdana;">p</span></i><span style="font-family:Verdana;"> < 0.05) </span></span><span style="font-family:Verdana;">in forest land than those </span><span style="font-family:Verdana;">in</span><span style="font-family:Verdana;"> the grazing land </span><span style="font-family:Verdana;">and smallholder farmlands</span><span style="font-family:Verdana;">. Conversely, BD and Av.P were significantly higher</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">(</span><i><span style="font-family:Verdana;">p</span></i><span style="font-family:Verdana;"> < 0.05)</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">in smallholder farmlands than grazing and forest lands probably due to different</span><span style="font-family:Verdana;"> litter accumulation and agricultural practices. </span><span style="font-family:""><span style="font-family:Verdana;">Moisture content and TN revealed positive significant correlations (</span><i><span style="font-family:Verdana;">p</span></i></span><span style="font-family:""> </span><span style="font-family:Verdana;"><</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">0.05) with SOC, while BD and Av.P revealed negative significant correlations (</span><i><span style="font-family:Verdana;">p</span></i></span><span style="font-family:""> </span><span style="font-family:Verdana;"><</span><span style="font-family:""> </span><span style="font-family:Verdana;">0.05)</span><span style="font-family:Verdana;">. Mean SOC density in </span><span style="font-family:Verdana;">smallholder farmlands (132.91 ± 9.48 tC/ha)</span><span style="font-family:Verdana;"> was </span><span style="font-family:Verdana;">the </span><span style="font-family:""><span style="font-family:Verdana;">lowest among the three land use types. Losses in CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> equivalence, as a result of land use change </span></span><span style="font-family:Verdana;">from forest lands to smallholder farmlands</span><span style="font-family:Verdana;"> w</span><span style="font-family:Verdana;">ere</span><span style="font-family:Verdana;"> 137.33 t/ha while that from </span><span style="font-family:Verdana;">grazing lands to smallholder farmlands were</span><span style="font-family:Verdana;"> 109.13 t/ha. </span><span style="font-family:""><span style="font-family:Verdana;">Total organic carbon (TOC) stocks differed significantly (</span><i><span style="font-family:Verdana;">p</span></i></span><span style="font-family:""> </span><span style="font-family:Verdana;"><</span><span style="font-family:""> </span><span style="font-family:Verdana;">0.05) from smallholder farmlands (10.73 Mt) to forest lands (91.13 Mt)</span><span style="font-family:Verdana;">. A sustainable farming</span><span style="font-family:""><span style="font-family:Verdana;"> technique that enhances SOC sequestration and minimizes soil CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> emissions is therefore recommended to replace tillage ridges formation commonly practiced by smallholder farmers.展开更多
Rainwater characteristics can reveal emissions from various anthropogenic and natural sources into the atmosphere. The physico-chemical characteristics of 44 monthly rainfall events （collected between January and Dec...Rainwater characteristics can reveal emissions from various anthropogenic and natural sources into the atmosphere. The physico-chemical characteristics of 44 monthly rainfall events （collected between January and December 2012） from 4 weather stations （Bamenda, Ndop plain, Ndawara and Kumbo） in the Bamenda Highlands （BH） were investigated. The purpose was to determine the sources of chemical species, their seasonal inputs and suitability of the rainwater for drinking. The mean pH of 5 indicated the slightly acidic nature of the rainwater. Average total dissolved solids （TDS） were low （6.7 mg/L）, characteristic of unpolluted atmospheric moisture/air. Major ion concentrations （mg/L） were low and in the order K＋ 〉 Ca2＋ 〉 Mg2~ 〉 Na＋ for cations and NO3 〉〉 HCO3 〉 SO] 〉 CI- 〉 PO3- 〉 F- for anions. The average rainwater in the area was mixed Ca-Mg-SO4-CI water type. The CI-/Na＋ ratio （1.04） was comparable to that of seawater （1.16）, an indication that N a＋ and CI originated mainly from marine （Atlantic Ocean） aerosols. High enrichments of Ca2＋, Mg2＋ and SO2- to Na＋ ratios relative to seawater ratios （constituting 44% of the total ions） demonstrated their terrigenous origin, mainly from Saharan and Sahelian arid dusts. The K＋/Na＋ ratio （2.24）, which was similar to tropical vegetation ash （2.38）, and NO3 was essentially from biomass burning. Light （〈 100 mm） pre-monsoon and post-monsoon convective rains were enriched in major ions than the heavy （〉 100 mm） monsoon rains, indicating a high contribution of major ions during the low convective showers. Despite the acidic nature, the TDS and major ion concentrations classified the rainwater as potable based on the WHO guidelines.展开更多
文摘Climate change and food security are among the pressing challenges facing humanity in the 21</span><sup><span style="font-family:Verdana;">st</span></sup><span style="font-family:Verdana;"> century. Soil organic carbon (SOC) stocks, total nitrogen (TN), texture, and bulk density (BD) are important soil properties, which control climate change. Three land use systems (smallholder </span></span><span style="font-family:Verdana;">farmlands</span><span style="font-family:Verdana;">, grazing land</span><span style="font-family:Verdana;">s</span><span style="font-family:Verdana;">, and forest lands) that coexist in the </span><span style="font-family:Verdana;">Bamenda Highlands (BH) influence ecosystem</span><span style="font-family:Verdana;"> services and induce soil degradation with the loss of SOC. The objective of this study was to evaluate the variation of SOC and some soil physicochemical properties as affected by the three land use systems (LUS). A total of 21 composite soil samples collected from 7 microclimatic zones of BH following “S” shape plots to the depth of 0 - 30 cm, were analysed for moisture content (MC), SOC, TN, BD, available phosphorus (Av.P), pH and texture. The results revealed that grazing land had the lowest mean sand content (40.79 ± 4.07). Mean MC, TN</span><span style="font-family:Verdana;"> and</span><span style="font-family:Verdana;"> SOC (%) content were significantly higher </span><span style="font-family:""><span style="font-family:Verdana;">(</span><i><span style="font-family:Verdana;">p</span></i><span style="font-family:Verdana;"> < 0.05) </span></span><span style="font-family:Verdana;">in forest land than those </span><span style="font-family:Verdana;">in</span><span style="font-family:Verdana;"> the grazing land </span><span style="font-family:Verdana;">and smallholder farmlands</span><span style="font-family:Verdana;">. Conversely, BD and Av.P were significantly higher</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">(</span><i><span style="font-family:Verdana;">p</span></i><span style="font-family:Verdana;"> < 0.05)</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">in smallholder farmlands than grazing and forest lands probably due to different</span><span style="font-family:Verdana;"> litter accumulation and agricultural practices. </span><span style="font-family:""><span style="font-family:Verdana;">Moisture content and TN revealed positive significant correlations (</span><i><span style="font-family:Verdana;">p</span></i></span><span style="font-family:""> </span><span style="font-family:Verdana;"><</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">0.05) with SOC, while BD and Av.P revealed negative significant correlations (</span><i><span style="font-family:Verdana;">p</span></i></span><span style="font-family:""> </span><span style="font-family:Verdana;"><</span><span style="font-family:""> </span><span style="font-family:Verdana;">0.05)</span><span style="font-family:Verdana;">. Mean SOC density in </span><span style="font-family:Verdana;">smallholder farmlands (132.91 ± 9.48 tC/ha)</span><span style="font-family:Verdana;"> was </span><span style="font-family:Verdana;">the </span><span style="font-family:""><span style="font-family:Verdana;">lowest among the three land use types. Losses in CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> equivalence, as a result of land use change </span></span><span style="font-family:Verdana;">from forest lands to smallholder farmlands</span><span style="font-family:Verdana;"> w</span><span style="font-family:Verdana;">ere</span><span style="font-family:Verdana;"> 137.33 t/ha while that from </span><span style="font-family:Verdana;">grazing lands to smallholder farmlands were</span><span style="font-family:Verdana;"> 109.13 t/ha. </span><span style="font-family:""><span style="font-family:Verdana;">Total organic carbon (TOC) stocks differed significantly (</span><i><span style="font-family:Verdana;">p</span></i></span><span style="font-family:""> </span><span style="font-family:Verdana;"><</span><span style="font-family:""> </span><span style="font-family:Verdana;">0.05) from smallholder farmlands (10.73 Mt) to forest lands (91.13 Mt)</span><span style="font-family:Verdana;">. A sustainable farming</span><span style="font-family:""><span style="font-family:Verdana;"> technique that enhances SOC sequestration and minimizes soil CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> emissions is therefore recommended to replace tillage ridges formation commonly practiced by smallholder farmers.
基金sponsored by the Japanese Government under the MONBUKAGAKUSHO Scholarship from the Ministry of Education, Culture, Sports, Science and Technology (MEXT)
文摘Rainwater characteristics can reveal emissions from various anthropogenic and natural sources into the atmosphere. The physico-chemical characteristics of 44 monthly rainfall events （collected between January and December 2012） from 4 weather stations （Bamenda, Ndop plain, Ndawara and Kumbo） in the Bamenda Highlands （BH） were investigated. The purpose was to determine the sources of chemical species, their seasonal inputs and suitability of the rainwater for drinking. The mean pH of 5 indicated the slightly acidic nature of the rainwater. Average total dissolved solids （TDS） were low （6.7 mg/L）, characteristic of unpolluted atmospheric moisture/air. Major ion concentrations （mg/L） were low and in the order K＋ 〉 Ca2＋ 〉 Mg2~ 〉 Na＋ for cations and NO3 〉〉 HCO3 〉 SO] 〉 CI- 〉 PO3- 〉 F- for anions. The average rainwater in the area was mixed Ca-Mg-SO4-CI water type. The CI-/Na＋ ratio （1.04） was comparable to that of seawater （1.16）, an indication that N a＋ and CI originated mainly from marine （Atlantic Ocean） aerosols. High enrichments of Ca2＋, Mg2＋ and SO2- to Na＋ ratios relative to seawater ratios （constituting 44% of the total ions） demonstrated their terrigenous origin, mainly from Saharan and Sahelian arid dusts. The K＋/Na＋ ratio （2.24）, which was similar to tropical vegetation ash （2.38）, and NO3 was essentially from biomass burning. Light （〈 100 mm） pre-monsoon and post-monsoon convective rains were enriched in major ions than the heavy （〉 100 mm） monsoon rains, indicating a high contribution of major ions during the low convective showers. Despite the acidic nature, the TDS and major ion concentrations classified the rainwater as potable based on the WHO guidelines.
