Effects of Litter Addition on Ectomycorrhizal Associates of a Lodgepole Pine ( Pinus contorta ) Stand in Yellowstone National Park

Abstract

Increasing soil nutrients through litter manipulation, pollution, or fertilization can adversely affect ectomycorrhizal (EM) communities by inhibiting fungal growth. In this study, we used molecular genetic methods to determine the effects of litter addition on the EM community of a Pinus contorta stand in Yellowstone National Park that regenerated after a stand-replacing fire. Two controls were used; in unmodified control plots nothing was added to the soil, and in perlite plots perlite, a chemically neutral substance, was added to maintain soil moisture and temperature at levels similar to those under litter. We found that (i) species richness did not change significantly following perlite addition (2.6 ؎ 0.3 species/core in control plots, compared with 2.3 ؎ 0.3 species/core in perlite plots) but decreased significantly (P < 0.05) following litter addition (1.8 ؎ 0.3 species/core); (ii) EM infection was not affected by the addition of perlite but increased significantly (P < 0.001) in response to litter addition, and the increase occurred only in the upper soil layer, directly adjacent to the added litter; and (iii) Suillus granulatus, Wilcoxina mikolae, and agaricoid DD were the dominant organisms in controls, but the levels of W. mikolae and agaricoid DD decreased significantly in response to both perlite and litter addition. The relative levels of S. granulatus and a fourth fungus, Cortinariaceae species 2, increased significantly (P < 0.01 and P < 0.05, respectively) following litter addition. Thus, litter addition resulted in some negative effects that may be attributable to moisture-temperature relationships rather than to the increased nutrients associated with litter. Some species respond positively to litter addition, indicating that there are differences in their physiologies. Hence, changes in the EM community induced by litter accumulation also may affect ecosystem function.Ectomycorrhizal (EM) fungi play a significant role in uptake and distribution of nutrients in temperate forest ecosystems, including the pine-dominated forests of the northern Rocky Mountains and Yellowstone National Park (9,13,14,40,42). Forest development often is fire driven and progresses from reestablishment of Pinus contorta (lodgepole pine) via serotinous cones through mixed P. contorta-Picea engelmannii (Engelmann spruce) or P. contorta-Abies lasiocarpa (subalpine fir) stands, depending on the soil conditions (41, 45). In the absence of fire, this progression to spruce-fir stands occurs in approximately 300 years. Litter accumulates and adds to the fire potential with the addition of the second tree species, and it continues to increase until fire reduces the fuel load.Fungal fruiting body (mushroom) assessments of EM fungal diversity indicate that patterns of EM diversity change during forest development. For example, after seedling establishment in young birch stands, EM fungal species diversity is relatively high. As stands age, the EM fungus species composition changes, the EM fungal diversity decreases, and a diffe...

Growth and Mycorrhizal Community Structure ofPinus sylvestrisSeedlings following the Addition of Forest Litter

“…Depending on the litter type, a number of interacting factors may be present, including physical constraints on root growth, water relations, allelopathic chemical leaching from the litter, and nutrient availability (39). The amount of litter and the way the litter is introduced into the soil (as a layer deposited on the soil surface [12] or thoroughly mixed with the soil [31]) may also be of importance.…”

Site properties have a stronger influence than fire severity on ectomycorrhizal fungi and associated N-cycling bacteria in regenerating post-beetle-killed lodgepole pine forests

“…Soil moisture and temperature levels were found to impact ECM community structure to a larger extent than soil nutrient status on lodgepole pine roots (Cullings and New 2003 ). Field studies of ECM associated with black spruce (Robertson et al 2006 ) and subalpine fir (Kranabetter et al 2009 ) also found variations in ECM community structure due to differences in moisture.…”

“…The sandy nature of dry soil sites could result in increased leaching on these sites, leading to lower levels of nitrate. Although nitrate levels were higher in wet soils, they were still considered low compared to typical levels (Ryan and Waring 1992; Cullings and New 2003; Douglas et al 2005. This may be due to the higher fungal biomass in wet soils capturing nitrate (Martin et al 2000 ).…”

Forest litter as the mulch improving growth and ectomycorrhizal diversity of bare-root Scots pine (Pinus sylvestris) seedlings

“…However, data regarding the effect of litter addition on ECM colonization and community structure are inconsistent. Both positive and negative effects of forest litter amendment have been observed in different experiments (Brearley et al 2003, Cullings et al 2003, Aučina et al 2007). …”