Nitrogen addition promotes terrestrial plants to allocate more biomass to aboveground organs: A global meta‐analysis

Abstract

A significant increase in reactive nitrogen (N) added to terrestrial ecosystems through agricultural fertilization or atmospheric deposition is considered to be one of the most widespread drivers of global change. Modifying biomass allocation is one primary strategy for maximizing plant growth rate, survival, and adaptability to various biotic and abiotic stresses. However, there is much uncertainty as to whether and how plant biomass allocation strategies change in response to increased N inputs in terrestrial ecosystems. Here, we synthesized 3516 paired observations of plant biomass and their components related to N additions across terrestrial ecosystems worldwide.Our meta-analysis reveals that N addition (ranging from 1.08 to 113.81 g m −2 year −1 ) increased terrestrial plant biomass by 55.6% on average. N addition has increased plant stem mass fraction, shoot mass fraction, and leaf mass fraction by 13.8%, 12.9%, and 13.4%, respectively, but with an associated decrease in plant reproductive mass (including flower and fruit biomass) fraction by 3.4%. We further documented a reduction in plant root-shoot ratio and root mass fraction by 27% (21.8%-32.1%) and 14.7% (11.6%-17.8%), respectively, in response to N addition. Meta-regression resultsshowed that N addition effects on plant biomass were positively correlated with mean annual temperature, soil available phosphorus, soil total potassium, specific leaf area, and leaf area per plant. Nevertheless, they were negatively correlated with soil total N, leaf carbon/N ratio, leaf carbon and N content per leaf area, as well as the amount and duration of N addition. In summary, our meta-analysis suggests that N addition may alter terrestrial plant biomass allocation strategies, leading to more biomass being allocated to aboveground organs than belowground organs and growth versus reproductive trade-offs. At the global scale, leaf functional traits may dictate how plant species change their biomass allocation pattern in response to N addition.

The Impact of Nitrogen Application on Leaf and Root Functional Traits of Davidia involucrata Saplings

“…Additionally, we found that N application significantly decreased root biomass and the ratio of root to leaf biomass (Figure 3b,c). These results suggest that D. involucrata saplings allocate less biomass to roots and more to leaves under N application conditions (Figure 3), which are in line with a recent global meta-analysis [66]. This response implies that D. involucrata saplings do not need to invest more biomass in roots under N application conditions, and increasing leaf biomass can enhance leaf photosynthetic rates and improve plant adaptation abilities to N application.…”

Trade‐off in the partitioning of recent photosynthate carbon under global change

“…Yue et al (2021) discovered that N addition significantly increased the root mass fraction and had no significant effect on leaf and stem mass fraction. In contrast, Feng et al (2023) reported a noteworthy increase in both leaf and stem mass fraction of terrestrial plant under N addition, while the root mass fraction was decreased by 14.7%. Unlike biomass, newly assimilated C can be utilized in various ways: it may be stored as carbohydrates, facilitate tissue growth, or serve as an energy source for plants (Halford, 2010).…”

“…Furthermore, N addition can also stimulate biomass allocation to nutrient organs. Under ample N supply, terrestrial plants augment both specific leaf areas and leaf areas per plant, thus enhancing their light‐capturing capabilities (Feng et al., 2023). These results are consistent with previous findings and support the optimal partitioning theory, which suggests that more assimilated C is allocated to aboveground tissues when nutrient limitation is alleviated (Grechi et al., 2007; Reynolds & Thornley, 1982).…”

“…In contrast, Feng et al. (2023) reported a noteworthy increase in both leaf and stem mass fraction of terrestrial plant under N addition, while the root mass fraction was decreased by 14.7%.…”

Responses of Soil Nitrogen Pools to Litter Input Under Nitrogen Addition: A Meta‐Analysis

“…N deposition, an important driver of global changes, generally increases soil N pools but decreases soil P pools (Deng et al., 2017; Jian et al., 2016; Lu et al., 2011; Luo et al., 2022). It is significantly altering the quantity and quality of litter input by regulating plant primary production and nutrient allocation (H. Feng et al., 2023; LeBauer & Treseder, 2008; Xia & Wan, 2008). These changes increase the complexity and uncertainty in predicting how soil N and P pools respond to litter input.…”