We studied the depth distribution of periphyton,growing on inundated dead trees in Kenyir Lake,Malaysia in June 1995.The algal floral composition and structure manifested changes down the depth gradient in terms of sp...We studied the depth distribution of periphyton,growing on inundated dead trees in Kenyir Lake,Malaysia in June 1995.The algal floral composition and structure manifested changes down the depth gradient in terms of species richness,abundance,diversity and cell density.In regression analysis,all these algal attributes were negatively correlated with the depth gradients at P<0.05.In terms of species richness,the bacillariophytes showed dominance over the cyanophytes and chlorophytes;whereas with respect to standing crop,the cyanophytes showed dominance over the bacillariophytes and chlorophytes.The chlorophyll a was higher at the mid and bottom-depths than the surface-depth in both the downstream and upstream sites,which showed that vertical productivity or biomass accumulation was greater in low light irradiance.The product-moment correlation analysis showed that conductivity,turbidity,dissolved oxygen,reactive phosphate and ammonium-nitrogen were highly correlated with the algal assemblage data.However,photosynthetic active radiation(PAR) showed poor correlation with the community data.These observations have cast some light on the autoecological characteristics,habitat preferences and environmental responses of tropical periphytic communities.展开更多
Laboratorial incubation and field experiments were conducted on soils ranging in texture from sandy loam toclay and in PH from 3 .6 to 9.0 to determine the agronomic effectiveness of single superphosphate (SSP), fused...Laboratorial incubation and field experiments were conducted on soils ranging in texture from sandy loam toclay and in PH from 3 .6 to 9.0 to determine the agronomic effectiveness of single superphosphate (SSP), fused magne-sium phosphate (FMP)and partially acidulated phosphate rock (PAPR)on 8 field crops. The results showed that thepottern of available P released from SSP was fixing -releasing-fixing-steady state, while that of PAPR was shortlyfixing-slowly releasing-fixing-steady state And the PAPR . SSP and FMP were equally effective as judged by yield, Puptake by plants and extractable P in soils after crop harvesting. The PAPR used as basal fertilizer was more effectivethan that as top dressing, and its residual effect was also obvious.展开更多
基金Supported by the Goverment of Malaysia,Intensified Research in Priority Areas(IRPA Project)(No.50258-J3)
文摘We studied the depth distribution of periphyton,growing on inundated dead trees in Kenyir Lake,Malaysia in June 1995.The algal floral composition and structure manifested changes down the depth gradient in terms of species richness,abundance,diversity and cell density.In regression analysis,all these algal attributes were negatively correlated with the depth gradients at P<0.05.In terms of species richness,the bacillariophytes showed dominance over the cyanophytes and chlorophytes;whereas with respect to standing crop,the cyanophytes showed dominance over the bacillariophytes and chlorophytes.The chlorophyll a was higher at the mid and bottom-depths than the surface-depth in both the downstream and upstream sites,which showed that vertical productivity or biomass accumulation was greater in low light irradiance.The product-moment correlation analysis showed that conductivity,turbidity,dissolved oxygen,reactive phosphate and ammonium-nitrogen were highly correlated with the algal assemblage data.However,photosynthetic active radiation(PAR) showed poor correlation with the community data.These observations have cast some light on the autoecological characteristics,habitat preferences and environmental responses of tropical periphytic communities.
文摘Laboratorial incubation and field experiments were conducted on soils ranging in texture from sandy loam toclay and in PH from 3 .6 to 9.0 to determine the agronomic effectiveness of single superphosphate (SSP), fused magne-sium phosphate (FMP)and partially acidulated phosphate rock (PAPR)on 8 field crops. The results showed that thepottern of available P released from SSP was fixing -releasing-fixing-steady state, while that of PAPR was shortlyfixing-slowly releasing-fixing-steady state And the PAPR . SSP and FMP were equally effective as judged by yield, Puptake by plants and extractable P in soils after crop harvesting. The PAPR used as basal fertilizer was more effectivethan that as top dressing, and its residual effect was also obvious.
