A meta-analysis of the effects of nitrogen additions on base cations: Implications for plants, soils, and streams

Nitrogen additions mobilize soil base cations in two tropical forests

“…. If nutrients are lost, N additions may ultimately negatively affect plant growth, as has been observed in boreal and temperate forests (Lucas et al 2011). In contrast, plant uptake and retention of newly mobilized nutrients could stimulate plant growth and increase cation cycling rates, at least in the short term, if these nutrients are limiting.…”

“…Thus, plant uptake is unlikely to remove added N from soils, so effects on base cation mobility are likely to be faster and larger than in N-poor sites. Indeed, the three tropical Chinese sites included in the above metaanalysis showed greater cation mobilization with N fertilization compared to temperate and boreal ecosystems (Lu et al 2009;Lucas et al 2011). Because highly weathered soils are already poor in rockderived nutrients (Walker and Syers 1976), mobilization and loss of cations from humid tropical forests are likely to have rapid negative consequences for plant productivity.…”

“…Over decadal timescales, numerous studies have shown that N fertilization and acid deposition can lead to declines in soil extractable cations (Hogberg et al 2006;Huntington 2005;Saarsalmi and Malkonen 2001), reduced foliar cation concentrations (Elvir et al 2005;Minocha et al 2000), and watershed-scale cation export (Fernandez et al 2003), although some sites show no change in cation cycling (Ingerslev et al 2001;Nilsen 2001;Nohrstedt 2001;Yanai et al 1999). Overall, a meta-analysis of 107 primarily temperate and northern sites showed that N additions generally increase mobilization of exchangeable base cations into soil solution and stream water, with parallel declines in soil extractable cations (Lucas et al 2011). Often, these effects of added N on cation leaching are delayed for decades in temperate sites, because increased plant uptake initially removes added N from soils (Currie et al 1999;Hogberg et al 2006).…”

Divergent Responses of Soil Buffering Capacity to Long-Term N Deposition in Three Typical Tropical Forests with Different Land-Use History

“…These findings have been verified well in large areas of Europe and North American, where there has been high atmospheric N deposition during the last decades. 3,5,20,23,64 There are several reasons for these divergent response patterns in tropical climate.…”

“…32 In contrast to temperate ecosystems, Al buffering is often suggested in the tropics, because of the depleted base cation pool. [5][6][7]11,20,36 As a result, conclusions based on studies conducted in temperate regions are of little relevance for the tropics under elevated N deposition. 37,38 To our knowledge, there also have been no investigations comparing responses of soil buffering capacity to long-term N deposition between forest ecosystems with different land-use history from either temperate or tropical regions.…”