Leaf Functional Traits of Two Species Affected by Nitrogen Addition Rate and Period Not Nitrogen Compound Type in a Meadow Grassland

Nitrogen (N) deposition rates are increasing in the temperate steppe due to human activities. Understanding the plastic responses of plant dominant species to increased N deposition through the lens of multiple traits is crucial for species selection in the process of vegetation restoration. Here, we measured leaf morphological, physiological, and anatomical traits of two dominant species (Stipa glareosa and Peganum harmala) after 3-year N addition (0, 1, 3, and 6 g N m−2 year−1, designated N0, N1, N3, and N6, respectively) in desert steppe of Inner Mongolia. We separately calculated the phenotypic plasticity index (PI) of each trait under different N treatments and the mean phenotypic plasticity index (MPI) of per species. The results showed that N addition increased the leaf N content (LNC) in both species. N6 increased the contents of soluble protein and proline, and decreased the superoxide dismutase (SOD) and the peroxidase (POD) activities of S. glareosa, while increased POD and catalase (CAT) activities of P. harmala. N6 increased the palisade tissue thickness (PT), leaf thickness (LT), and palisade-spongy tissue ratio (PT/ST) and decreased the spongy tissue–leaf thickness ratio (ST/LT) of S. glareosa. Furthermore, we found higher physiological plasticity but lower morphological and anatomical plasticity in both species, with greater anatomical plasticity and MPI in S. glareosa than P. harmala. Overall, multi-traits comparison reveals that two dominant desert-steppe species differ in their plastic responses to N addition. The higher plasticity of S. glareosa provides some insight into why S. glareosa has a broad distribution in a desert steppe.

Section: Discussionsupporting

confidence: 93%

Section: Discussionsupporting

confidence: 93%

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Two Dominant Herbaceous Species Have Different Plastic Responses to N Addition in a Desert Steppe

Guo

Zuo²,

Hu³

et al. 2022

“…Study of a semi-arid grassland revealed that the stem-leaf biomass ratio is more responsive to grazing, while the specific leaf area is more sensitive to N enrichment (Zheng et al, 2022). Further investigations have indicated that the addition of N has a negative effect on the leaf dry matter content (Mao et al, 2014;Zheng et al, 2017;Sun et al, 2022). However, there is no consensus on the responses of specific leaf area, leaf P and N concentrations to N addition between different species (Huang et al, 2008;Zhang et al, 2018;Su et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Shrub encroachment alters plant trait response to nitrogen addition in a semi-arid grassland

Liu

Yang

et al. 2023

Encroachment of shrubs over large regions of arid and semi-arid grassland can affect grassland traits and growth under a background of increasing nitrogen (N) deposition. However, the effects of N input rates on species traits and the growth of shrubs on grasslands remain unclear. We examined the effects of six different N addition rates on the traits of Leymus chinensis in an Inner Mongolia grassland encroached by the leguminous shrub, Caragana microphylla. We randomly selected 20 healthy L. chinensis tillers within shrubs and 20 tillers between shrubs in each plot, measuring the plant height, number of leaves, leaf area, leaf N concentration per unit mass (LNCmass), and aboveground biomass. Our results showed that N addition significantly enhanced the LNCmass of L. chinensis. The aboveground biomass, heights, LNCmass, leaf area, and leaf number of plants within the shrubs were higher than those between shrubs. For L. chinensis growing between shrubs, the LNCmass and leaf area increased with N addition rates, leaf number and plant height had binomial linear relationships to N addition rates. However, the number of leaves, leaf areas and heights of plants within shrubs did not vary under various N addition rates. Structural Equation Modelling revealed N addition had an indirect effect on the leaf dry mass through the accumulation of LNCmass. These results indicate that the response of dominant species to N addition could be regulated by shrub encroachment and provide new insights into management of shrub encroached grassland in the context of N deposition.

“…As plant economic spectrum predicts, species with the traits capable of acquiring resource rapidly (e.g., high N concentration, specific leaf area, and photosynthetic rate) would compete for resource more strongly under N enrichment ( Wright et al, 2004 ; La Pierre and Smith, 2015 ). Recent studies have revealed inconsistent responses of plant functional traits to nutrient addition, while some studies showed that N addition enhanced leaf N concentration, chlorophyll concentration and specific leaf area, thus leading to a marked increase in photosynthetic rates ( Tatarko and Knops, 2018 ; Zheng et al, 2018 ; Sun et al, 2022 ). Others found no effect of N addition on leaf mass area, area-based concentrations of foliar N and chlorophyll concentrations ( Hu and Wan, 2019 ).…”

Section: Introductionmentioning

confidence: 99%

Tipping point of plant functional traits of Leymus chinensis to nitrogen addition in a temperate grassland

Yang

Zhang²,

Zhang

et al. 2022

Self Cite

It has widely been documented that nitrogen (N) enrichment stimulates plant growth and modifies plant functional traits in the terrestrial ecosystem. However, it remains unclear whether there are critical transitions or tipping points for the response of plant growth or traits to N enrichment, and how these responses differ to different N forms. We chose the native, perennial clonal grass, Leymus chinensis in Inner Mongolia steppe, and conducted a field experiment, in which six N addition rates (0, 2, 5, 10, 20, and 50 g N m–2 year–1) and five N compound types [NH4NO3, (NH4)2SO4, NH4HCO3, CO(NH2)2, slow-release CO(NH2)2] are considered. Here, we found that the different N compound types had no significant effect on the growth of L. chinensis. N addition rate significantly increased plant aboveground biomass and leaf nitrogen concentration, whereas decreased leaf dry matter content. The tipping point for N-induced aboveground biomass increase was at 10 g N m–2 year–1, and the changes in functional traits were at N addition rates of 20 g N m–2 year–1. Our findings suggested that the responses of aboveground biomass and functional traits to N addition were asymmetric, in which responses in aboveground biomass were more sensitive than that in functional traits. The differential sensitivity of aboveground biomass and functional traits of L. chinensis occurred to N deposition highlights the importance of functional traits in mediating ecosystem functioning in the face of N deposition, regardless of which chemical forms dominate in the deposited N.