ABSTRACT
This study examined the characteristics of phosphorus (P) adsorption and desorption in surface soil (0-10 cm) of a secondary forest after selective cutting disturbance at three levels of intensity (low, medium, high) in order to reveal the effects of different disturbance intensities on soil P adsorption and desorption. Maximum adsorption amount (Qm), adsorption intensity factor, maximum buffer capacity, maximum desorption amount, average desorption rate and readily desorptable phosphorus were measured. Qm in the focal forests was 1383.93-1833.34 mg·kg-1, and Qmin forests with middle and high disturbance intensities was significantly higher than that in forests with low disturbance intensity and in primary forests. P adsorption intensity was 0.024-0.059 L·mg-1, and forests with high and low disturbance intensities increased the P adsorption intensity significantly. The maximum buffer capacity varied from 35.68 to 97.97 L·kg-1, with the highest value found in the forest with the highest disturbance intensity. Selective cutting significantly reduced the potential for phosphorus supply in the forest soils. The maximum desorption amount, average desorption rate and readily desorptable phosphorus content in the focal forests were 526.32-797.54 mg·kg-1, 14.7%-25.5% and 1.79-5.41 mg·kg-1, respectively, indicating that the ability of soil to release phosphorus significantly decreased with increasing disturbance intensity. Selective cutting changed the phosphorus adsorption and desorption characteristics by reducing the supply and release of soil phosphorus.
Subject(s)
Phosphorus/pharmacokinetics , Pinus/physiology , Soil/chemistry , Adsorption , China , Forests , TreesABSTRACT
In order to clarify the effects of selective cutting on soil phosphorus availability in Korean pine broad-leaved forest, surface soil (0-10 cm) samples from original Korean pine broad-leaved forest and natural forests with mild, medium and intensive cutting disturbances were collected. The Sui modified Hedley phosphorus fractionation method was used to continuously extract soil samples and analyzed the differences and changes of soil phosphorus fractions from different experimental stands. The results showed that the soil total phosphorus content of Korean pine broad-leaved forest varied from 1.09 to 1.66 g·kg-1, with the original stand and intensive cutting disturbance stand being the maximum and minimum one, respectively. The differences of soil total phosphorus content among cutting disturbance levels were significant. The Olsen phosphorus and phosphorus activation coefficients changed with an amplitude of 7.26-17.79 mg·kg-1 and 0.67%-1.07%, respectively. Both of them significantly decreased with the increase of selective cutting disturbance level. The concentrations of all P fractions except HCl-Po, i.e., H2O-Pi, NaHCO3-P, NaOH-P, HCl-Pi, Residual-P, decreased with increasing cutting disturbance levels compared with original forest. The correlation coefficient between H2O-Pi and soil Olsen phosphorus was the highest (0.98), though it only accounted for 1.5%-2.2% of the total phosphorus. NaOH-P content contributed to more than 48.0% of the total phosphorus, acknowledged as the potential source of soil phosphorus. In conclusion, selective cutting disturbance could constrain phosphorus storage and soil phosphorus availabi-lity of the Korean pine broad-leaved forests by significantly reducing the content of soil inorganic phosphorus and NaOH-Po, and such trends were positively dependent on the intensity of selective cutting.
Subject(s)
Forests , Phosphorus , Soil/chemistry , China , Pinus , TreesABSTRACT
An investigation was conducted on the living tree volume, coarse woody debris (CWD) loading, and composition of Larix gmelinii forest along a human disturbance gradient, i.e., no disturbance (natural larch forest), one-time disturbance (natural forest was disturbed once only), and two-time disturbance (natural forest was disturbed two times consecutively), on the northern slope of Greater Hinggan Mountains. The results showed that under no disturbance, one-time disturbance, and two-time disturbance, the average living tree volume of L. gmelinii forest was 161.6, 138.3, and 114. 8 m3 x hm(-2), and the average CWD loading was 69.77, 36.64 and 32.61 m3 x hm(-2), respectively. In natural L. gmelinii forest, most of CWD was of 20-40 cm diameter class, among which, fallen logs occupied 72%, and snags and stumps occupied 28% ; while in one-time and two-time disturbance L. gmelinii forests, most CWD was of 10-30 cm diameter class, with the fallen logs, snags, and stumps occupied 70%, 14% and 16%, and 57%, 15% and 28%, respectively. Human disturbance reduced the CWD loading of L. gmelinii forest and altered the composition of the CWD.
