Natural and anthropogenic drivers of calcium depletion in a northern forest during the last millennium

Abstract

The pace and degree of nutrient limitation are among the most critical uncertainties in predicting terrestrial ecosystem responses to global change. In the northeastern United States, forest growth has recently declined along with decreased soil calcium (Ca) availability, suggesting that acid rain has depleted soil Ca to the point where it may be a limiting nutrient. However, it is unknown whether the past 60 y of changes in Ca availability are strictly anthropogenic or partly a natural consequence of long-term ecosystem development. Here, we report a high-resolution millennial-scale record of Ca and 16 other elements from the sediments of Mirror Lake, a 15-ha lake in the White Mountains of New Hampshire surrounded by northern hardwood forest. We found that sedimentary Ca concentrations had been declining steadily for 900 y before regional Euro-American settlement. This Ca decline was not a result of serial episodic disturbances but instead the gradual weathering of soils and soil Ca availability. As Ca availability was declining, nitrogen availability concurrently was increasing. These data indicate that nutrient availability on base-poor, parent materials is sensitive to acidifying processes on millennial timescales. Forest harvesting and acid rain in the postsettlement period mobilized significant amounts of Ca from watershed soils, but these effects were exacerbated by the long-term pattern. Shifting nutrient limitation can potentially occur within 10,000 y of ecosystem development, which alters our assessments of the speed and trajectory of nutrient limitation in forests, and could require reformulation of global models of forest productivity.

The ecological impacts of lakewater calcium decline on softwater boreal ecosystems

“…However, evaluating the consequences of Ca concentrations falling below critical thresholds will require detailed information regarding historical conditions. Therefore, future Ca decline analyses should focus on reconciling the current disagreement between paleolimnological and biogeochemical modeling efforts regarding the relationship between current Ca concentrations and pre-industrial levels, while remaining mindful of the possibility that declines in Ca availability in recent decades may be occurring on top of Ca depletion processes operating on much longer time-scales (Leys et al 2016). Limitations inherent to the paleolimnological analyses of cladoceran remains (i.e.…”

Wildfires and geochemical change in a subalpine forest over the past six millennia

“…Data were measured as counts of photons emitted that are unique to each element, and were calibrated with the mudrock calibration (Rowe et al 2012), which is a combination of 200 standards of similar matrix (grain-size, homogeneity) and composition, to obtain a concentration value (mg/100 mg of dried powdered lacustrine sediment). Repeatability of this method was tested on a previous set of lacustrine sedimentary samples and analytical error was ±2% for both major and trace elements (Leys et al 2016).…”

Conversion from temperate secondary forests into plantations (Larix spp.): Impact on belowground carbon and nutrient pools in northeastern China

“…Juice et al () observed that Ca addition to declining sugar maples increased maple health, growth, and survivorship. Furthermore, Leys et al () also showed that forest growth decreased with reduced available soil Ca content in the northeastern United States. Similarly, Mg deficiencies have been observed in many regions of European forests (Armbruster, MacDonald, Dise, & Matzner, ).…”