关键词: 城市绿地系统, 稳定同位素, CO₂浓度, 车流量, 来源

Abstract: Soil quality plays an important role in maintaining long-term productivity of forests. In this study, we measured 24 soil factors, including seven soil physical properties, 12 soil chemical properties and five soil enzyme activities, in Moso bamboo forests harvested in different strip clearcuttings (with strip width of 3, 6, 9 and 12 m, designated as D1, D2, D3, D4 respectively) and with traditional selective logging (CK). Those factors were selected as soil quality assessment indicators. We compared soil properties among different treatments, and used principal component analysis (PCA) to construct the minimum data set of soil quality assessment. The results showed that soil bulk density (BD) in 0-10 cm soil layer of strip logging treatments was significantly lower than that of CK. The minimum waterholding capacity, capillary moisture capacity and capillary porosity in 10-20 cm layer of strip logging treatments were significantly higher than those of CK. The contents of soil organic matter (SOM), nitrogen, and phosphorus in 0-40 cm layer in strip logging treatments were higher than those of CK. There was significant difference in soil total P content between strip logging treatments and the CK. Soil protease activities in D3 and D4 were higher than that in other treatments. Soil invertase activity in D2 was the highest. The cumulative contribution rate of six principal components extracted by PCA was 78.39%. In combination with vector constant modulus (Norm) value, six soil characters, i.e. SOM, BD, acid phosphatase activity, C:N, C:P and non-capillary porosity, were selected to construct the minimum data set. The ranking of soil quality assessment value was in the order of D4, D2, D3, D1 and CK. In the short term, strip clearcutting promoted the release of soil nutrients in Moso bamboo forest, with larger logging widths performed better effects. However, the influence of strip clearcutting on soil properties may be a longer-term process, which requires continuous monitoring and evaluation, so as to provide a theoretical basis for reasonable choice of strip widths of clearcutting for Moso bamboo forests.

Key words: urban green space system, stable isotope, CO₂ concentration, traffic volume, source.