Long-term logging residue loadings affect tree growth but not soil nutrients in lodgepole pine forests Wu, Jianping; Wei, Xiaohua; Waterhouse, Michaela; Qi, Guang
Both above- and below-ground characteristics are affected by logging residue loadings. Long-term monitoring of tree growth and soil nutrients was conducted. We found that tree growth but not soil nutrients were affected. There were dynamic relationships between tree growth and logging residue loadings.; Methods
The experiment was conducted near Satah Mountain (52o28’N, 124o43’W), located about 110 km northwest of Alexis Creek, west-central British Columbia, Canada. The region has a mean annual precipitation which varies between 300 and 800 mm, and much of it comes as snow during the winter. The mean annual temperature is 1.3°C and the snowing cover is usually from November to April. Four experimental treatments were randomly arranged into five blocks which are over 100 ha each in lodgepole pine plantations. Four 20 m × 20 m plots were established in each block.The treatments were (1) removal of all logging residues (N, 0 Mg ha-1), removed manually; (2) logging residue loading similar to whole-tree-harvesting residuals left on site (W, 35-45 Mg ha-1); (3) logging residue loading similar to stem-only-harvesting residuals left on site (S, 60-70 Mg ha-1); and (4) logging residue loading similar to double that of stem-only-harvesting and more similar to disease and insects killed stands (D, 100-120 Mg ha-1). The N, W, S, and D treatments were randomly assigned to the plots within each block and no further measurements of the debris weight change over time were made.
For tree height and base diameter data, we sampled in each plot were measured 10 times (years 1, 2, 3, 5, 6, 9, 10, 11, 14 and 19) over the study period (1996 to 2015). The units for data is cm.
For soil nutrients data, we sampled in each plot in 2001, 2006 and 2015. All soil samples were collected from 0-20 cm mineral layer. All soil samples were analyzed for total carbon (C), total nitrogen (N), available phosphorus (P) and exchangeable cations (Ca, K, Mg).
For foliar nutrients, we sampled in each plot in 2015. Foliage samples were analyzed for N, P, Ca, K, Mg, Zn, Cu, B and sulphur (S). Soil and foliage samples were analyzed at the chemistry laboratory of the British Columbia Ministry of Forests, Lands and Natural Resource Operations following their standard analytical protocols (Carter and Gregorich 2006). C and N were analyzed by elemental analyzer (Thermo Electron Corporation, MA, USA), metal elements mentioned above were analyzed by inductively coupled plasma mass spectrometer (ICP-MS, Agilent, Santa Clara, CA, USA) and available P was measured with a UV-visible spectrophotometer after extraction with acid-ammonium fluoride solution.