Nitrogen Saturation in Northern Forest Ecosystems

Storage and Turnover of Organic Matter in Soil

“…Changes in vegetation allocation strategy, litter quality, and soil microbes can lead to large C losses belowground that more than offset C gains associated with increased aboveground productivity (Mack et al 2004). Any benefits of N-deposition are expected to reach a saturation point, after which productivity levels off, and eventually diminishes due to other nutrient limitations or increased susceptibility to stresses such as pollution, frost damage, or disease (Agren and Bosatta 1988;Aber et al 1989). …”

Ecological issues related to N deposition to natural ecosystems: research needs

“…Decomposition of organic matter may be affected by N deposition. Many studies have reported increased litter decomposition rates as a result of N fertilization of forests I (Aber et al, 1989;Fenn, 1991), while other studies have reported slower decomposition (Adams and Angradi, 1996;Magill and Aber, 1998). Finally, there is some evidence that elevated N deposition may also inhibit methane production (Neff et al, 1994;West et al, 1998).…”

“…A number of variables have been used to assess N saturation and N status of ecosystems. Export of nitrate in streamwater is one that is commonly used (Aber et al, 1989;Stoddard, 1994;. However, natural streamwater concentrations and export of nitrate are not well quantified for all natural ecosystems, nor is it an applicable indicator for all ecosystems.…”

“…Specifically, I was asked to identify available N, the system may be considered N-saturated, research needs. From a very informal survey of colleagues although there are several definitions of N saturation (Agren in forest soils, and fi-om my own review, I have placed these and Bosatta, 1988;Aber et al, 1989;Stoddard, 1994). research needs into five categories: (1) the nitrogen cycle, Generally, N-saturated ecosystems can be thought of as (2) carbon cycling, (3) effects on arid and other neglected those with a long-term amelioration of N limitations on ecosystems, (4) effects on complex ecosystems and combiotic activity, along with a decrease in N retention capacity.…”

The composition, spatial patterns, and influencing factors of atmospheric wet nitrogen deposition in Chinese terrestrial ecosystems

“…It was estimated that the production of reactive N increased from 15 Tg N in 1860 to 156 Tg N in 1995, with a further increase up to 187 Tg N in 2005 (Galloway et al, 2008). On the one hand, atmospheric N deposition has a positive effect on maintaining plant productivity of terrestrial ecosystems through enhancing the N availability (Fleischer et al, 2013;Reay et al, 2008;Thomas et al, 2010;Ti et al, 2012); on the other hand, excessive N deposition has negative impacts on ecosystem health and services, such as N saturation (Aber et al, 1989;Kopacek et al, 2013), soil acidification (Bowman et al, 2008;Maljanen et al, 2013;Vitousek et al, 1997), and loss of biodiversity (Bobbink et al, 2010;Stevens et al, 2004).…”