Effects of Increased N Deposition on Leaf Functional Traits of Four Contrasting Tree Species in Northeast China

Abstract

Northeast China is persistently affected by heavy nitrogen (N) deposition. Studying the induced variation in leaf traits is pivotal to develop an understanding of the adaptive plasticity of affected species. This study thus assesses effects of increased N deposition on leaf morphological and anatomical traits and their correlation among and with biomass allocation patterns. A factorial experiment was conducted utilizing seedlings of two gymnosperms (Larix gmelinii, Pinus koraiensis) and two angiosperms (Fraxinus mandshurica, Tilia amurensis). Leaf mass per area and leaf density decreased and leaf thickness increased under high N deposition but trait interrelations remained stable. In gymnosperms, leaf mass per area was correlated to both leaf thickness and area, while being correlated to leaf density only in angiosperms. Epidermis, mesophyll thickness, conduit and vascular bundle diameter increased. Despite the differences in taxonomic groups and leaf habits, the common patterns of variation suggest that a certain degree of convergence exists between the species’ reaction towards N deposition. However, stomata pore length increased in angiosperms, and decreased in gymnosperms under N deposition. Furthermore, biomass and leaf mass fraction were correlated to leaf traits in gymnosperms only, suggesting a differential coordination of leaf traits and biomass allocation patterns under high N deposition per taxonomic group.

Correlation of Leaf and Root Traits of Two Angiosperm Tree Species in Northeast China under Contrasting Light and Nitrogen Availabilities

“…A pronounced C limitation under L− might thus explain the lack of leaf trait acclimation (besides LMF) to nitrogen addition. Under L+ conditions, our results were partially in line with previous studies reporting a significantly decreased LMA [26] but contrasted others which reported an increase in the leaf area and/or no significant change in LMA [63,67] under increased N fertilization. However, plant traits in general, and leaf traits in specific, were known to change largely during ontogeny [66].…”

“…These contrasting findings were related to the very low leaf densities discovered, which enabled both species to develop more and larger-sized leaves despite an increased leaf thickness. Previously, some studies indicated that LMA was either equally dependent on the variation of LT and LD [62], was strongly reliant on LT [26,45], or linked to LT and leaf volume per area (LVA) [63,64]. Our results indicated that the variation in LMA across the studied species depended strongly on LD, supporting the former findings.…”

“…The two N fertilization levels were set as 0 g N m −2 yr −1 (N−) and 10 g N m −2 yr −1 additional N (N+). Ammonium nitrate (NH 4 NO 3 ) was applied, dissolved in irrigation water, in two split doses on the soil surface-50% in June and 50% in July [26]. The fertilization level of N+ plots was set to correspond to the N deposition levels measured in the region, i.e.,~28-100 kg N ha −1 yr −1 [41]; thus, the N+ treatment corresponded to 200%-400% of regular N input.…”

“…Recently, however, gap sizes were reported to affect the chemistry (in particular increasing N and reducing lignin concentrations) rather than the biomass and morphology of the gap-facing fine roots of Fagus orientalis Lipsky [22]. Above ground, increased N availability often significantly decreases LMA and leaf density (LD) while the leaf thickness (LT) increases [26]. Besides effects on nutrient availability, light availability may also have an indirect impact on fine-roots via modified evapotranspiration rates under different microclimatic conditions [4,25].…”

Intraspecific differences in plant functional traits are related to urban atmospheric particulate matter

“…2a , compared with T1, the leaf thickness of T2 and T3 were significantly increased, and the difference reached a significant level ( p < 0.05) and an extremely significant level ( p < 0.01). Leaf thickness is generally considered as a valuable characteristic, which may be related to resource acquisition, water conservation and assimilation [ 41 ]. Leaf tissue thickness was positively correlated with leaf water use efficiency, and is also closely related to leaf water storage capacity [ 42 ].…”