Mean Residence Time Of Nitrogen Research Articles

Nitrogen Use Efficiency for Growth of Fagus crenata Seedlings Under Elevated Ozone and Different Soil Nutrient Conditions

Ozone is a phytotoxic gaseous air pollutant and its negative effects on forest production are a major concern. To understand the effects of ozone on forest production, it is important to clarify the nitrogen use efficiency (NUE) for tree growth under elevated ozone conditions, because nitrogen is a primal limiting factor of forest production in many cool-temperate forests. Soil nutrient conditions are considered factors affecting ozone susceptibility of tree growth. Therefore, in the present study, we investigated the effects of ozone on NUE for the growth of Siebold’s beech (Fagus crenata Blume) seedlings grown under different soil nutrient conditions. Seedlings of Siebold’s beech were grown under three gas treatments (charcoal-filtered air or ozone at 1.0 or 1.5 times the ambient concentration) in combination with three soil nutrient conditions (non-fertilised, low-fertilised or high-fertilised) for two growing seasons. Based on the dry mass and nitrogen concentration in each plant organ, we calculated NUE and its components, including nitrogen productivity (NP) and the mean residence time of nitrogen (MRT) during the second growing season. Ozone did not decrease the NUE of the seedlings during the second growing season, whereas leaf level photosynthetic nitrogen use efficiency (PNUE), a component of NP, was decreased by ozone. On the other hand, the soil nutrient supply decreased the NUE of the seedlings. Reductions in both NP and MRT were attributed to the decrease in NUE because of soil nutrient supply, whereas PNUE did not respond to soil nutrient supply. There was no significant interaction of ozone and soil nutrient supply on the NUE, or its components, of the seedlings. Our results indicated that there is a difference in the response between the NUE for individual growth and that of leaf level PNUE of Siebold’s beech seedlings to ozone and soil nutrient supply.

Growth and nitrogen use in Xanthium canadense grown in an open or in a dense stand

Plants develop branches profusely when grown solitarily, while less so when grown in a dense stand. Such changes in architecture are associated with changes in dry mass allocation and nitrogen use. Here, we studied what traits in plant growth and nitrogen use were influenced by different light climates in the stand. Annual plants (Xanthium canadense) were grown solitarily or in a dense stand. Dry mass growth was analyzed as the product of the net assimilation rate (NAR) and leaf area (LA). Nitrogen use efficiency (NUE) was analyzed as the product of nitrogen productivity (NP) and the mean residence time (MRT) of nitrogen. These growth variables were further factorized into their components. Solitary plants maintained a high NAR, whereas plants in the dense stand decreased the NAR due to mutual shading. Plants in the dense stand developed a larger LA with a higher specific leaf area than solitary plants. Solitary plants had higher NUE due to higher NP. A temporal increase in NUE was attributed to the increase in MRT of nitrogen. Light climate was different between solitary and dense-stand plants, but they took up a comparable amount of nitrogen and used it differently in response to the given light climate. NUE was thus demonstrated to be a useful tool for analyzing the mechanism leading to different N use in plant growth.

Nitrogen use efficiency revisited

Nitrogen use efficiency (NUE) was originally defined as the dry mass productivity per unit N taken up from soil. The term was subsequently redefined as the product of nitrogen productivity (NP) and mean residence time of nitrogen (MRT). However, this redefinition was found to contradict the original definition under certain conditions, and confusion arose when the MRT defined for a steady-state system was applied to a system that was actually not at steady state. As MRT is the expected length of time that a unit of N newly taken up from soil is retained before being lost, it can be translated into the plant nitrogen duration (PND) divided by the total N uptake. This MRT is determined equally well for a steady state- and a non-steady state system and is in accordance with the original definition of NUE. It can be applied to a herbaceous perennial stand (that was at a steady state) and to an annual stand (that was not at a steady state) to determine NUE. NUE is also applicable when plant growth and reproduction are analyzed in relation to N use.

Whole‐canopy nitrogen‐use efficiency of pioneer species in early secondary forest succession in Vietnam

AbstractThe size hierarchy among plants during forest succession can be influenced by differences in nitrogen‐use efficiency (NUE). During succession, soil nitrogen availability decreases, which increases the importance for species to use nitrogen efficiently. We compare whole‐canopy‐NUE and its underlying traits among pioneer species in a tropical forest over the first years of succession. At the leaf level, potential photosynthetic NUE (PPNUE: light‐saturated photosynthetic rate/leaf N content) was partly positively correlated with species growth rate but not to species height. Canopy‐NUE differed two‐fold among species. The species with the highest PPNUE and growth rate but with a small stature had a high canopy‐NUE and the tallest species had a low canopy‐NUE. Differences in canopy‐NUE appeared to be largely determined by leaf life span (LLS) and nitrogen resorption. A high LLS or a high resorption resulted in a high mean residence time of nitrogen and thus a high canopy‐NUE. Canopy‐NUE of a species was different between successional stands that differed in age and thus in height, leaf‐area index, and resource availability. Thus, an increase in competitive pressure with succession did cause some changes in the use of nitrogen, except for one species. Species that are generally considered part of the same functional group (pioneer trees) can differ considerably in NUE and its underlying traits.

Soil water status influences plant nitrogen use: a case study

We studied differences in nitrogen use efficiency (NUE) among six species [Calamagrostis epigejos (L.) Roth., Carex duriuscula C.A. Mey., Phragmites communis (L.) Trin., Salix gordejevii Y.L. Chang, Salix cheilophila Schneid., and Typha minima Funk.] growing in two contrasting habitat types, i.e., a riverine wetland with high water supply and a riparian zone with low water supply. The two sites were different in soil water supply, but not in nitrogen supply. Here, NUE was defined as the total net primary production per unit nitrogen absorbed. There was no significant difference in NUE between the species growing in the riverine wetland (Carex duriuscula, P. communis, S. cheilophila, T. minima) and the species growing in the river bank (Carex duriuscula, Calamagrostis epigejos, P. communis, S. gordejevii). We further analyzed NUE as the product of the nitrogen productivity (A, the rate of dry matter production per unit of nitrogen in the plant) and the mean residence time of nitrogen (MRT, the period of time a unit of nitrogen is present in the plant). The species growing in the riverine wetland had larger A but lower MRT than the species growing in the river bank. There was an inverse relationship between A and MRT. Consequently, NUE was similar among species and habitats. These results suggested that environmental factors, such as soil water supply, can influence N use by plants.

Effect of Nitrogen Supply on the Nitrogen Use Efficiency of an Annual Herb, Helianthus annuus L.

Abstract: Nitrogen use efficiency (NUE) is the product of nitrogen productivity (NP) and the mean residence time of nitrogen (MRT). Theory suggests that there should be a trade-off between both components, but direct experimental evidence is still scarce. To test this hypothesis, we analyzed the effect of varying nitrogen supply levels on NUE and its two components (NP, MRT) in Helianthus annuus L., an annual herb. The plants investigated were subjected to six nitrogen levels (0, 2, 4, 8, 16, and 32 g N/m2). Total plant production increased substantially with increasing nitrogen supply. Nitrogen uptake and loss also increased with nitrogen supply. Nitrogen influx (rin) and outflux (rout) were defined as the rates of nitrogen uptake and loss per unit aboveground nitrogen, respectively. Both rm and rout increased with increasing nitrogen supply. In addition, rm was far higher than rout. Consequently, the relative rate of nitrogen increment (rin-rout) also increased with nitrogen supply. There were marked differences between treatments with respect to parameters related to the stress resistance syndrome: nitrogen pool size, leaf nitrogen concentration, and net aboveground productivity increased with nitrogen supply. Plants at high nitrogen levels showed a higher NP (the growth rate per unit aboveground nitrogen) and a shorter MRT (the inverse of rout), whereas plants at low nitrogen levels displayed the reverse pattern. Shorter MRT for plants at high nitrogen levels was caused by the abscission of leaves that contained relatively large fractions of total plant nitrogen. We found a negative relationship between NP and MRT, the components of NUE, along the gradient of nitrogen availability, suggesting that there was a trade-off between NP and MRT. The NUE increased with increasing nitrogen availability, up to a certain level, and then decreased. These results offer support for the hypothesis that adaptation to infertile habitats involves a low nitrogen loss (long MRT in the plant) rather than a high NUE per se. The higher NUE at the plant level was a result, in part, of greater nitrogen resorption during senescence. We suggest that a long MRT (an index of nitrogen conservation) is a potentially successful strategy in nitrogen-poor environments. (Managing editor: Ya-Qin HAN)

Soil type affects nitrogen conservation in foliage of small Pinus sylvestris L. trees

Nutrient conservation in plants and soil fertility may be intricately linked. We studied nitrogen conservation in small Scots pine (Pinus sylvestrisL.) trees growing in stands on organogenic Dystric Histosols and on mineral Podzols. Nitrogen-resorption efficiency (NRE) and proficiency (NRP) of senescent needles, and mean residence time of nitrogen (MRT) were studied in relation to needle surface area, needle longevity, and leaf mass per area (LMA). Trees on Podzols had higher nitrogen concentration in green needles than the trees on Dystric Histosols, but the nitrogen concentration of yellowing needles was similar for trees on both soil types. NRE averaged 65±3.5% (mean±SD) and 56±7.2% for the trees on Podzols and Dystric Histosols, respectively. Neither NRP (0.44±0.05% and 0.35±0.07%, respectively) nor MRT (8.4±2.3 and 6.1±1.2 years) differed significantly between the stands on the two soil types. Mean needle surface area was significantly smaller in trees on Dystric Histosols (76±29 mm2) than on Podzols (131±38 mm2), whereas needle longevity varied between 2 and 4 years independently of the soil type. Trees invested, on average, the same amount of dry matter per unit of needle area on both soil types. Growth of trees, measured as increment of shoot length, was more restricted on Dystric Histosols (55±18 mm yr−1) than on Podzols (184±44 mm yr−1). The results of the correlation analysis applied to pooled data were inconsistent with the relations between traits of stress resistance syndrome observed in inter-specific comparisons. The study indicated that Scots pine trees relocated nitrogen from senescent foliage more efficiently on mineral Podzols than on organogenic Dystric Histosols, but the minimum nitrogen concentration of needles appeared to be similar on both soil types.

Variation in nitrogen‐use traits within and between five Carex species growing in the lowland mires of northern Japan

Summary Theory suggests that there should be a trade‐off between nitrogen productivity (A) and mean residence time of nitrogen in plant tissues (MRT), and that this trade‐off depends on the N availability of the habitats. To test this, we studied A, MRT and nitrogen‐use efficiency (NUE, reciprocal of N concentration in the dead shoot) in wetland Carex species sampled from seven lowland mires in Japan. The NUE and MRT of unproductive species that usually grow in acidic and N‐poor habitats exceeded those of productive species that are abundant in weakly acidic and N‐rich habitats. Except for the most productive species, C. lyngbyei, interspecific differences in A were small, irrespective of productivity. Intraspecific variation in A was relatively large in contrast to those in NUE and MRT. Within each species, no parameter correlated with the concentration of total dissolved nitrogen (TDN) in the soil water. Although NUE and MRT of the plants growing in the weakly acidic habitats correlated negatively with TDN, they were constantly high in the acidic habitats regardless of the TDN concentration. Responses of A did not correlate with TDN concentration of soil water in either acidic or weakly acidic habitats. A trade‐off between A and MRT in the five Carex species was not detected in relation to habitat N richness. We suggest that soil water acidity dominates the ecological performance of the Carex species, and that the trade‐off between A and MRT does not necessarily apply to wetland vegetation.

Evidence for increased sensitivity to nutrient and water stress in a fast-growing hybrid willow compared with a natural willow clone.

The hypothesis that fast-growing breeds of willow (Salix spp.) are more sensitive to nutrient and water stress and less efficient in nutrient- and water-use than slower-growing natural willow clones was tested. Cuttings of a natural clone of S. viminalis L. collected in Sweden (L78183) and a hybrid clone of S. schwerinii E. Wolf. x S. viminalis L. ("Tora") were grown outdoors in pots under various experimental conditions in a full-factorial design. The experimental conditions included three fertilization, two irrigation and two temperature regimes. Classical growth analysis techniques, based on an initial and a final harvest, were used as a screening method, together with calculation of intrinsic water-use efficiency (foliar carbon isotope ratio; delta13C). In addition, nitrogen-use efficiency was calculated as the product of nitrogen productivity and mean residence time of nitrogen on an annual basis. There were significant differences in plant structural parameters (leaf area ratio, specific leaf area) and water-use efficiency between the clones. Furthermore, several clone x treatment interaction effects on various growth parameters indicated that the clones adapted to specific environments in different ways. "Tora" plants produced up to 25% more shoot biomass than plants of the natural clone in response to high rates of fertilization and irrigation, whereas clone ranking was reversed in most other treatments. The results support the hypothesis that fast-growing hybrids are more sensitive to nutrient and water stress than slower-growing natural clones. The hypothesis that natural clones have higher resource-use efficiency than fast-growing hybrids was supported with respect to water, but not nitrogen.

Nitrogen uptake and use by competing individuals in a Xanthium canadense stand

We studied differences in nitrogen uptake and use for plant growth among individuals competing in a natural dense stand of an annual herb, Xanthium canadense. Larger individuals took up more nitrogen than proportionately to their size, indicating that the competition for soil nitrogen was asymmetric among individuals, although it was more symmetric than the competition for light. The rate of nitrogen loss of individuals also increased with plant size. While smaller individuals shared smaller fractions of total plant nitrogen in the stand, they had higher nitrogen concentrations per unit mass. "Turnover" rates of nitrogen influx (rin) and outflux (rout) were defined as the rates of nitrogen uptake and loss per unit aboveground nitrogen, respectively. rin was higher in larger individuals, whereas rout was higher in smaller individuals. Consequently, the relative rate of nitrogen increment (rin-rout) was higher in larger individuals, whereas it was around zero in the smallest individuals. The mean residence time of nitrogen (MRT), defined as the inverse of rout, was longer in larger individuals. Nitrogen productivity (NP), i.e. the growth rate per unit aboveground nitrogen, was higher in larger individuals. As the product of lifetime MRT and NP gives the nitrogen use efficiency (NUE), defined as biomass production per unit flux of nitrogen, higher MRT and NP observed in larger individuals would have contributed to their higher lifetime NUE. Shorter MRT in smaller individuals was caused by the abscission of leaves which contained relatively large fractions of total plant nitrogen. Xanthium canadense, as a competitive ruderal, tended to produce leaves at higher positions to acquire higher light levels at the expense of older leaves rather than to modify their productive structure to efficiently use low light levels as observed in shade-tolerant species.

Interspecific and intraspecific differences in shoot and leaf lifespan of four Carex species which differ in maximum dry matter production.

The effect of N supply on shoot and leaf lifespan was investigated in established stands of four herbaceous Carex species which differed in maximum dry matter production. These species were, in rank order of increasing maximum dry matter production (per unit ground area): Carex diandra≤C. rostrata<C. lasiocarpa≤C. acutiformis. The observed patterns of shoot and leaf turnover were compared with data on leaf characteristics and nitrogen use efficiency indices of these species. There was no consistent difference in shoot production (number of shoots produced per unit ground area) between species with low production and those with high production: Carex diandra (low production) and C. lasiocarpa (high production) had high shoot production, while shoot production in c. rostrata (low production) and C. acutiformis (high production) was much lower. The rank order of the mean lifespan of shoots was: C. diandra<C. rostrata≤C. lasiocarpa<C. acutiformis. Thus, the lifespan of shoots increased with increasing maximum dry matter production of these Carex species. In all species, increased N supply led to a significant reduction in shoot lifespan. The reduction of shoot lifespans in response to enhanced N supply will result in increased nutrient turnover rates in these species. There was no consistent difference in the number of leaves produced per shoot between low-production and high-production species. C. diandra and C. lasiocarpa had relatively low leaf production, while C. rostrata and C. acutiformis had relatively high leaf production per shoot. Thus, this pattern is opposite to the pattern in shoot production. The rank order of the mean lifespan of leaves was: C. diandra<C. rostrata<C. acutiformis≤C. lasiocarpa. This implies that the high-production species had longer mean leaf lifespans than the low-production species. Mean leaf lifespan was not significantly affected by enhanced N supply, except in C. diandra, where leaf lifespan decreased in response to enhanced N supply. Shoot lifespans did not show any significant relation with the specific leaf area (SLA, leaf area per unit leaf mass) or the leaf area ratio (LAR, leaf area per unit plant mass) of the species under study. There was, however, a negative relation (r 2=0.71) with the nitrogen concentration in the leaves. Shoot lifespans were positively related (r 2=0.79) with whole-plant nitrogen use efficiency (NUE, dry matter production per unit N-loss) and with the mean residence time of nitrogen (MRT, the average time-span during which a unit of nitrogen is present in the plant) (r 2=0.78), but not with the nitrogen productivity (A, annual dry matter production per unit N in the plant). Leaf lifespan was positively related with the mean residence time of nitrogen in the plants (r 2-0.70). For all the other parameters, there were no significant relations with leaf lifespan. From these results we conclude that: (1) at the stand level, shoot and leaf lifespans are positively related with maximum dry matter production; and (2) shoot and leaf lifespan are important determinants of whole-plant nitrogen economy.

Nitrogen Use Efficiency of Carex Species in Relation to Nitrogen Supply

We studied the effect of nitrogen supply (3.3 and 20.0 g°m—2°yr—1) on the nitrogen use efficiency (NUE) of three Carex species that differ in maximum growth rate. The rank order of maximum growth rate of these species is: Carex diandra @&lt; Carex rostrata &lt; Carex acutiformis. We distinguished two components of NUE: the mean residence time of nitrogen (MRT) in the plant and the nitrogen productivity (A). In this concept, NUE equals the product of MRT and A, and thus equals total productivity divided by the total N loss in litter. The N productivity (A) of C. diandra was significantly higher than that of C. rostrata and C. acutiformis. In each species A decreased strongly at enhanced N supply. The MRT of N differed substantially between species, but was not significantly affected by N supply. Contrary to what is generally found, the species with the lowest maximum growth rate (C. diandra) had the highest N turnover rate (lowest MRT), while the species with the highest maximum growth rate (C. acutiformis) had the lowest N turnover rate (highest MRT). In all species, the NUE decreased with increasing N supply. As a result of the observed patterns in N productivity and mean residence time, the species with the lowest maximum growth rate (C. diandra) had the lowest nitrogen use efficiency, while the species with the highest maximum growth rate (C. acutiformis) had the highest NUE. These results are not in agreement with the generally observed patterns in NUE along gradients of primary productivity. Comparisons of the results of this study with those of other studies show that generalizations of patterns of NUE along gradients of primary productivity should explicitly take into account which growth forms are compared (evergreen species vs. deciduous species, or [congeneric] species with the same growth form). Moreover, this study shows that factoring NUE into its components is a useful tool in the analysis of the adaptive significance of the N economy of plants.