| In order to explain the effect of vegetation restoration on soil phosphorus availability, phosphorus sorption and desorption properties of different soil layers soils from natural secondary forest in typical black soil region were studied by measuring and analyzing the maximum adsorption amount (Qm), maximum buffer capacity (MBC), desorption and desorption rate and et al. Based on this experiment, phosphorus adsorption and desorption properties of soils from soil and water conservation plantations, such as Scots Pine(Pinus sylvestris var. mongolica), Manchurian Ash (Fraxinus mandshurica), Poplar(Populus nigra var. italica×P. cathayan), and natural grassland in typical black soil region were studied by measuring and analyzing the maximum adsorption capacity (Qm), phosphorus sorption index (PSI), readily desorbable phosphorus (RDP) and desorption amount and et al.We also investigated the phosphorus sorption and desorption properties of soils from21.30,40,52-year-old Larch (Larix gmelini) plantations and natural secondary forest in typical black soil region by measuring, calculating and analyzing the maximum adsorption capacity (Qm), maximum buffer capacity (MBC) and desorption amount and rate and et al. Through measuring and analyzing the contents of total P, available phosphorus and phosphorus fractionations of Soil and water conservation plantations, such as Larch(Larix gmelini). Manchurian Ash(Fraxinus mandshurica), Scots Pine(Pinus sylvestris var. mongolica) and Poplar(Populus nigra var. italica×P. cathayan) plantations, this paper aimed to approach the P fractionations and availability. The results may serve as theoretical basis for the efficiency of vegetation restoration.The results showed that:Langmuir equation is the best one to describe the sorption data showing a similar adsorption mechanism in natural secondary forest soil profile layer; Natural secondary forest soil phosphorus maximum adsorption capacity (Qm) varied from442.21～857.23mg/kg; Qm was showed the trend of increased in the soil depth of0-60cm then decreased after increased in the range of60～180cm soil, and those in the soil depth of0～20cm were significantly lower than those of140～180cm (p<0.05); Adsorption saturation (DPS) was contrary; Desorption and desorption rate were higher during soil depth of0-20cm, and could significantly improve the utilization of phosphorus by reducing the adsorption, and increasing the desorbing level, but those of the soil depth of140～180cm were weak. Phosphorus from natural secondary forest during soil depth of0～20cm could be supplied easily, and weaked with increasing soil depth, then decreased the utilization.Forest soil phosphorus maximum adsorption capacity (Qm) varied from636.54to725.77mg/kg during soil depth of0～40cm. Phosphorus sorption index (PSI), adsorption intensity factor (K) and maximum buffer capacity (MBC) were significantly lower than natural grass (p<0.05). Capacity of soil phosphorus desorption and desorption rate were higher in all three forests and the soil readily desorbable phosphorus (RDP) is3.06-4.63times higher than that of natural grassland (p<0.05). Soil and water conservation plantations, especially Manchurian Ash Plantation, could significantly improve the utilization of phosphorus by reducing the adsorption, and increasing the desorbing level.The adsorption content and rate of phosphorus were higher than natural secondary forest with a phosphorus addition rate of200-2400mg/kg during soil depth of0-10cm. Soil phosphorus maximum adsorption capacity (Qm) varied from692.24to759.41mg/kg. Phosphorus maximum adsorption capacity (Qm), adsorption intensity factor (K) and maximum buffer capacity (MBC) were first increased with the increasing age, and then decreased. Those of30-year-old Larch (Larix gmelini) plantations were significantly higher than that of others (p<0.05). The amounts of soil phosphorus desorption and desorption rate were fist reduced with increasing age, and then increased. Those of52-year-old larch plantation were highest, and could easily increase the desorbing level into soil solution, but30a were lowest. Larch plantation could not always improve or reduce the utilization of phosphorus.52-year-old larch plantation showed a strong fixation capacity, and30a released easily to soil, but those didn’t reach the level of natural secondary forest.The concentrations of total P, available P and P fractionations in Manchurian Ash and Poplar plantations were higher significantly than others (p<0.05); Organic P of soil is the major in all four forests, and NaOH-Po representing moderately labile Organic phosphorus was higher than other P fractionations, comprising on the average58.88%of the total soil P; there was lower content of the labile phosphorus (H2O-P and NaHCO3-P); Organic matter was strongly correlated with total P, available P all P fractions, except NaHCO3-Po. Soil P fractions were positively correlated among each other (p<0.05), but only weakly correlated with NaHCO3-Po. Manchurian Ash and Poplar plantations could significantly improve the utilization of phosphorus. It can provide reference for vegetation restoration evaluation in typical black soil region. |
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