Growth and biomass of Populus irrigated with landfill leachate

Abstract

Resource managers are challenged with waste disposal and leachate produced from its degradation. Poplar (Populus spp.) trees offer an opportunity for ecological leachate disposal as an irrigation source for managed tree systems. Our objective was to irrigate Populus trees with municipal solid waste landfill leachate or fertilized well water (control) (N, P, K) during the 2005 and 2006 growing seasons and test for differences in tree height, diameter, volume, and biomass of leaves, stems, branches, and roots. The trees were grown at the Oneida County Landfill located 6 km west of Rhinelander, Wisconsin, USA (45.6°N, 89.4°W). Eight clones belonging to four genomic groups were tested: NC13460, NC14018 [(Populus trichocarpa Torr. & Gray × Populus deltoides Bartr. ex Marsh) × P. deltoides ‘BC₁’]; NC14104, NC14106, DM115 (P. deltoides × Populus maximowiczii A. Henry ‘DM’); DN5 (P. deltoides × Populus nigra L. ‘DN’); NM2, NM6 (P. nigra × P. maximowiczii ‘NM’). The survival rate for each of the irrigation treatments was 78%. The total aboveground biomass ranged from 0.51 to 2.50 Mg ha⁻¹, with a mean of 1.57 Mg ha⁻¹. The treatment × clone interaction was not significant for tree diameter, total volume, dry mass of the stump or basal roots, or root mass fraction (P > 0.05). However, the treatment × clone interaction was significant for height, total tree dry mass, aboveground dry mass, belowground dry mass, and dry mass of the leaves, stems + branches (woody), and lateral roots (P < 0.05). There was broad clonal variation within the BC₁ and DM genomic groups, with genotypes performing differently for treatments. In contrast, the performance of the NM and DN genomic groups was relatively stable across treatments, with clonal response to irrigation being similar regardless of treatment. Nevertheless, selection at the clone level also was important. For example, NC14104 consistently performed better when irrigated with leachate compared with water, while NC14018 responded better to water than leachate. Overall, these data will serve as a basis for researchers and resource managers making decisions about future leachate remediation projects.

Introduction

Poplars (Populus spp.) have been extensively studied in short rotation woody biomass production systems for multiple uses such as fiber, fuel and environmental benefits (Dickmann, 2001, Isebrands and Karnosky, 2001, Coleman and Stanturf, 2006). Exemplary traits that have contributed to the success of such uses include: ease of rooting, quick establishment, fast growth, and elevated rates of photosynthesis and water usage (Ceulemans et al., 1992, Pontailler et al., 1999, Zalesny et al., 2006). Broad genetic diversity among poplar genomic groups and selection of specific genotypes within such groups increase the potential enhancement of growth and establishment for various uses across heterogeneous sites (Heilman and Stettler, 1985, Heilman et al., 1994). The combination of appropriate cultural practices and well-suited genotypes helps to maximize poplar performance for improved biomass yields (Buhler et al., 1998, Stanturf et al., 2001).

Environmental benefits have been realized from poplar culture when used as components in riparian buffers along streams (Schultz et al., 2004) and as vegetative filters for phytoremediation applications (Licht and Isebrands, 2005). Several phytoremediation projects utilized wastewater in the form of landfill leachate as an irrigation and fertilization source for poplar trees (Shrive et al., 1994, Erdman and Christenson, 2000, Zalesny and Bauer, in press). Proper clonal selection practices must be utilized given the genetic variability within the genus Populus (Rajora and Zsuffa, 1990, Eckenwalder, 1996) and the variable concentrations of inorganic and organic components in the leachate (Gettinby et al., 1996). Leachate production occurs through natural degradation processes aided by the movement of water through the landfill profile (Christensen and Kjeldsen, 1989). Due to the variation associated with residential, commercial, and industrial waste material, the leachate is highly variable and compositional changes occur seasonally and annually (Shrive et al., 1994, Kjeldsen et al., 2002).

A great deal of information has been reported using poplars for short rotation forestry (Heilman, 1999, Riemenschneider et al., 2001), but there are relatively fewer reports about using poplars for leachate phytoremediation systems. Thus, researchers and resource managers need information that is currently lacking about tree establishment with leachate irrigation. Such information will help increase the success of using poplars for remedial benefits, especially with ecologically damaging contaminants such as those found in most leachate. Overall, the use of short rotation woody crop management for remediation supports improved environmental quality and secondary benefits such as carbon sequestration, a harvestable product, aesthetic improvements, and erosion control (Isebrands and Karnosky, 2001, Duggan, 2005).

This project expands on our previous work investigating phyto-recurrent selection, which was defined as a method using crop and tree improvement strategies to identify and select superior performing clones for remediation projects (Zalesny et al., in press). Clonal selections were made after three successive cycles of evaluation (i.e. three separate greenhouse studies) testing 23 traits relating to height growth, leaf development, and root initiation at 14 (cycle 1; 25 clones), 45 (cycle 2; 12 clones), and 30 (cycle 3; 12 clones) days after planting. The best eight clones were selected for testing in the current in situ study (cycle 4) out of the original 25 genotypes belonging to six distinct genomic groups: (1) (Populus trichocarpa Torr. & Gray × Populus deltoides Bartr. ex Marsh) × P. deltoides ‘BC₁’; (2) P. deltoides × P. deltoides ‘DD’; (3) P. deltoides ‘D’; (4) P. deltoides × Populus maximowiczii A. Henry ‘DM’; (5) P. deltoides × Populus nigra L. ‘DN’; (6) P. nigra × P. maximowiczii ‘NM’.

The overall objective of all phyto-recurrent selection cycles was to test the effectiveness of poplars for uptake of inorganic and organic contaminants found in landfill leachate. More specifically, the objective of the current study was to test for differences in growth and biomass distribution of eight Populus clones when irrigated with municipal solid waste landfill leachate or fertilized well water (control) (N, P, K) for two growing seasons. In addition to actual phytoremediation success, tree growth and biomass accumulation are important for evaluating the overall effectiveness of the biological attenuation system. These data will serve as a basis for researchers and resource managers making decisions about future leachate remediation projects.