Response of Sugar Maple to Calcium Addition to Northern Hardwood Forest

Abstract

Watershed budget studies at the Hubbard Brook Experimental Forest (HBEF), New Hampshire, USA, have demonstrated high calcium depletion of soil during the 20th century due, in part, to acid deposition. Over the past 25 years, tree growth (especially for sugar maple) has declined on the experimental watersheds at the HBEF. In October 1999, 0.85 Mg Ca/ha was added to Watershed 1 (W1) at the HBEF in the form of wollastonite (CaSiO3), a treatment that, by summer 2002, had raised the pH in the Oie horizon from 3.8 to 5.0 and, in the Oa horizon, from 3.9 to 4.2. We measured the response of sugar maple to the calcium fertilization treatment on W1. Foliar calcium concentration of canopy sugar maples in W1 increased markedly beginning the second year after treatment, and foliar manganese declined in years four and five. By 2005, the crown condition of sugar maple was much healthier in the treated watershed as compared with the untreated reference watershed (W6). Following high seed production in 2000 and 2002, the density of sugar maple seedlings increased significantly on W1 in comparison with W6 in 2001 and 2003. Survivorship of the 2003 cohort through July 2005 was much higher on W1 (36.6%) than W6 (10.2%). In 2003, sugar maple germinants on W1 were approximately 50% larger than those in reference plots, and foliar chlorophyll concentrations were significantly greater (0.27 g/m2 vs. 0.23 g/m2 leaf area). Foliage and fine-root calcium concentrations were roughly twice as high, and manganese concentrations twice as low in the treated than the reference seedlings in 2003 and 2004. Mycorrhizal colonization of seedlings was also much greater in the treated (22.4% of root length) than the reference sites (4.4%). A similar, though less dramatic, difference was observed for mycorrhizal colonization of mature sugar maples (56% vs. 35%). These results reinforce and extend other regional observations that sugar maple decline in the northeastern United States and southern Canada is caused in part by anthropogenic effects on soil calcium status, but the causal interactions among inorganic nutrition, physiological stress, mycorrhizal colonization, and seedling growth and health remain to be established.

Decreased water flowing from a forest amended with calcium silicate

“…Transpiration could increase either because of an increased number of stomata (i.e., more foliage on existing trees and new regeneration) or increased water-loss rate from stomata. Our evidence of increased LAI, and past measurements of greater crown density (11), foliar biomass (29), and seedling regeneration (30) at HBEF following Ca addition suggests that this ET response was because of an increased number of stomata. (Fig.…”

Non-climatic constraints on upper elevational plant range expansion under climate change

“…The availability of the major soil nutrients-nitrogen, phosphorus and potassium (as well as soil water content)-show, if anything, a tendency to increase with elevation (soil characteristics shown in the electronic supplementary material, figure S3). This suggests that our studied system probably does not suffer from acid deposition-induced nutrient limitations (specifically, calcium, magnesium and manganese) that have caused sugar maple declines in some other northeastern North American forests [28,30]. As reduced regeneration on high elevation soils is probably not a result of nutrient or moisture deficiency, it follows that biotic factors may play an important role, and indeed we observed an increasing incidence of fungal infection on the roots of emerging seedlings at higher elevations, consistent with previous evidence of fungal pathogens as a mortality agent of sugar maple [48].…”

“…While the absence of any growth reduction in seedlings established at high elevation ( figure 4) is not what one would expect if AM fungi were lacking at high-elevation sites, it is possible that insufficient AM colonization upon germination contributed to seedling mortality by other causes. The relationships between AM fungi, nutrient acquisition, edaphic factors and sugar maple growth are not clear [28,52], and additional research is needed to discern the precise role of antagonistic versus beneficial fungi in controlling sugar maple's elevational distribution.…”

“…Establishment of sugar maple is favoured by well-drained loam soils with pH of 5.5-7.3, but the species can tolerate a range of soil textures provided they are neither too dry nor too shallow [22]. Research on nutritional requirements indicates that sugar maple survival, growth and reproduction can be limited by low soil concentrations of calcium and magnesium [28,29], which can become depleted following acid deposition [29,30].…”

Seedling mycorrhizal type and soil chemistry are related to canopy condition of Eucalyptus gomphocephala

“…This may allow new approaches to manage the decline. For example, applying calcium improved the health status of sugar maple (Hugget et al 2007) and mycorrhizal colonization (Juice et al 2006). A bioassay approach was adopted using E. gomphocephala seedlings to probe for compatible mycorrhizal fungi in soil cores from 12 field study sites representative of tuart decline.…”