The ecological effects of eucalypt plantations(EPs) have garnered increasing attention.To understand their effect on soil quality at a landscape scale,and to determine whether soil quality parameters differ due to different stand types,we evaluated soil characteristics in twenty-one groups of EPs,Pinus massoniana Lamb.plantations(PMPs) and natural broadleaved forests(NBFs)across Guangdong Province,China.Both the physical characteristics of soil hydrology and the properties of soil nutrients in A and B horizons were determined.Results showed that,compared to NBFs,EPs and PMPs produced a shallower litter layer,reduced canopy density,higher soil bulk density,significantly lower total porosity,non-capillary porosity,total water volume,and hygroscopic water in the A horizon(P<0.05).Moreover,total N,available K,and soil organic carbon(SOC) in EPs and PMPs were significantly lower than in NBFs.EPs and PMPs did not differ significantly in N,P or K content,but PMPs had significantly lower SOC and boron in the A horizon than EPs.Low p H and poor capacity to buffer acidification generally occurred in all cover types.Both EPs and PMPs showed a decline in soil properties relative to NBFs,but EPs and PMPs exhibited no significant difference.These results indicate that actions are needed to ameliorate the potential negative effects on soil quality in forestry plantations.
空气负离子(Negative air ion,NAI)是综合反映空气质量的重要指标,对人类的生活环境具有重大意义。该研究选定广东车八岭国家级自然保护区内10个典型观测点,在5月份(夏季)和10月份(秋季)进行NAI观测。结果表明:保护区内NAI浓度较高,均高于700个·cm^(-3);各观测点的NAI浓度基本呈现水体>森林>草坪>楼内的规律;秋季10个观测点的NAI浓度从高到低依次为博物馆旁河中央、漂流起点、小瀑布口、小瀑布支柱、针阔混交林、针叶林、博物馆前草坪、单竹坑、吊桥、办公楼内;观测点漂流起点、小瀑布口、小瀑布支柱、博物馆旁河中央的NAI水平与单竹坑、吊桥、博物馆前草坪、办公楼内、针阔混交林、针叶林均有显著差异。夏季各观测点的NAI浓度从高到低依次为小瀑布口、博物馆旁河中央、小瀑布支柱、漂流起点、针阔混交林、针叶林、单竹坑、博物馆前草坪、吊桥、办公楼内,其中观测点漂流起点、小瀑布口、小瀑布支柱、博物馆旁河中央显著高于其它地点,观测点针阔混交林、针叶林显著高于单竹坑、吊桥、博物馆前草坪、办公楼内,观测点办公楼内显著低于其他点。区内NAI浓度受到季节、水体、植被类型等因子的影响。
