Long term effect of nitrogen addition on understory community in a Chinese boreal forest

Effects of nitrogen addition on leaf nutrient stoichiometry in an old‐growth boreal forest

“…S2, Table S2). This was because of the nitrophilic character of graminoids (Bobbink et al 2010) and was consistent with the substantial increase in abundance previously reported at our site (Du 2017, Xing et al 2019).…”

“…However, 6 yr of N addition increased the N:P ratio up to 22.0, which was higher than 20, and thus, D. angustifolia should be P‐limited and its growth under the high N treatment should be less than or equal to the control at best. The grass abundance under the high N treatment was higher than that of the control (Du 2017, Xing et al 2019), which implied that P limitation for the grasses might not be the case. In fact, D. angustifolia was able to maintain its leaf P content under high soil N availability (Fig.…”

“…Nutrient stoichiometry might be a better measure of forest health (Mcnulty et al 1996), and N:P ratios have been used widely to indicate nutrient limitation (Vitousek et al 2010). Because the grass D. angustifolia experienced a substantial increase in abundance under the high N treatment (Du 2017, Xing et al 2019), we expected that its leaf stoichiometry might be less affected by N addition than that of the shrubs. In contrary, the N:P ratio of the grass D. angustifolia showed the largest magnitude of changes (Fig.…”

“…Different species in the same ecosystem may show diverse responses to increased N deposition due to differences in nutrient use strategies (Mao et al 2017), and this response may also differ across plant functional groups, such as tree, shrub, and grass; thus, the community nutrient index can serve as a promising indicator of the nutrient status at the community level (Du 2017). With increasing N deposition, a commonly reported phenomenon is an increase in the understory grass abundance (Nordin et al 2009, Bobbink et al 2010, Gilliam et al 2016, Xing et al 2019), suggesting that the leaf nutrient stoichiometry of grasses might be less affected by increased soil N availability. It is imperative to incorporate both overstory and understory plants and their multiple nutrient responses to better understand the effect of N deposition on forest health.…”

Overall supply level, not the relative supply of nitrogen and phosphorus, affects the plant community composition of a supratidal wetland in the Yellow River Delta

“…The results correspond principally with our first hypothesis (H 1 ). The concentration of soil inorganic N and available P often increase with corresponding increasing N and P input amounts (Huang et al, 2018;Xing et al, 2019). For the input amounts of N are always several folds higher than P in our experiment (Table 1) as well as in the real world (Penuelas et al, 2012(Penuelas et al, , 2013, the gap of N input among supply levels is much higher than among supply ratios, while the difference degree between the gap of P input among supply levels and the gap among supply ratios is not so much as N. Therefore, supply level affected soil inorganic N more than supply ratio but just had roughly equal effect intensity on soil available P. For soil N:P ratio was more correlated to available P (r = −0.653, n = 144, P b 0.01) than to inorganic N (r = 0.563, n = 144, P b 0.01) according to the Pearson correlation analysis across 4 years, correspondingly, supply ratio affected more on soil N:P than supply level, with higher supply ratio having higher soil N:P ratio.…”