Trade‐off between root nitrogen acquisition and shoot nitrogen utilization across 13 co‐occurring pasture grass species

Abstract

Summary 1.Although plant nitrogen (N) strategies may play an important role for community structure and ecosystem functioning, there is not a clear understanding of the link between N acquisition by roots and N utilization by shoots. Particularly, it is unclear how the co-variations between size-and physiology-related traits determine N acquisition and N utilization at the plant scale. 2. We used 13 co-occurring temperate pasture grasses to study inter-specific variations in above-ground N yield and in root N acquisition and shoot N utilization traits. N acquisition traits concerned root influx capacities for and , root mass and specific root area in ingrowth cores. N utilization traits concerned leaf life span, leaf N content, leaf N resorption, mean residence time of N and leaf N use efficiency. 3. We found evidence for three trade-offs across species concerning root N acquisition: (i) root mass increased when specific root area declined; (ii) an increase in root area was observed when total N influx capacity decreased; and (iii) root influx capacity increased when capacity declined. 4. High total root uptake capacity gave rise to high leaf N content and was associated across species to low leaf N use efficiency. Tall grasses were characterized by high shoot N yield, high root biomass and high leaf N use efficiency. Physiology-related traits and size-related traits were generally found independent. 5. Our study demonstrates how size and N uptake related root traits are associated to major axes of plant specialization ((i) plant size and (ii) conservation vs. exploitation of N) which were previously identified based on shoot traits. Contrasted N strategies were segregated across species according to four combinations along these two axes.

Grass strategies and grassland community responses to environmental drivers: a review

“…At the local scale of low-mountain grasslands, Maire et al (2009) further showed in a study with 13 perennial grasses that N-exploitative species are characterized by high leaf nitrogen content, high root uptake capacity and low leaf N use efficiency, while N-conservative species exhibit the opposite trait syndrome. The positive correlation between root uptake capacity and leaf nitrogen content has been also evidenced in other studies (Poorter et al 1991;Wright and Westoby 2000).…”

“…Across species, some plant functional traits are related to each other and co-vary along axes of specialization (Díaz et al 2004) while others are independent (Maire et al 2009(Maire et al , 2013a. Understanding whether these co-variations occur or not leads to the functional strategy concept.…”

“…However, the type of nutrient is critical because it affects the strategies used by the species to acquire nutrients and the importance of biotic interactions (Schellberg and Pontes 2012). For instance, at local scale, grass species can exhibit strategic preferences in root uptake capacities between NO 3 -and NH 4 + to coexist within a given community, with dominant species preferring nitrate and stabilized rare species preferring ammonium (Maire et al 2009). At the global scale, it has been recently shown that strategies of nitrogen and water acquisition are independent.…”

“…its numerical value or categorical type, captures a plant function and modulates its fitness (Violle et al 2007). For instance, a large plant height has been linked to high light interception rates (Violle et al 2007), large root density is related to high nutrient absorption and high leaf nutrient content indicates low plant nutrient efficiency (Maire et al 2009). Further, a large seed mass is an important predictor of establishment success, and seed output is an important predictor of dispersal (Westoby et al 2002).…”

Turion production and nutrient reserves in Potamogeton crispus are influenced by sediment nutrient level

“…Indeed, even small variations in nutrient availability can create large differences in plant growth and reproductive output (Sugiyama & Bazzaz 1998, Bonser & Aarssen 2003. Plant size, biomass allocation, plant structure, and total rhizome length all vary substantially according to sediment nutrients (Stoll et al 1998, Müller et al 2000, Vojtíšková et al 2004, Maire et al 2009). These traits may determine both the ongoing fitness of plants and the performance of future propagules.…”