Leaf Nutrient Traits Research Articles

Changes in leaf nutrient traits and photosynthesis of four tree species: effects of elevated [CO2], N fertilization and canopy positions

Aims Leaf traits of trees exposed to elevated [CO2] in association with other environmental factors are poorly understood in tropical and subtropical regions. Our goal was to investigate the impacts of elevated [CO2] and N fertilization on leaf traits in southern China. Methods Four tree species, Schima superba Gardn. et Champ. (S. superba), Ormosia pinnata (Lour.) Merr (O. pinnata), Castanopsis hystrix AC. DC. (C. hystrix) and Acmena acuminatissima (Blume) Merr. et Perry (A. acuminatissima) were studied in a factorial combination of atmospheric [CO2] (ambient at ;390 lmol mol 1 and elevated [CO2 ]a t;700 lmol mol 1 ) and N fertilization (ambient and ambient + 100 kg N ha 1 year 1 ) in open-top chambers in southern China for 5 years. Leaf mass per unit leaf area (LMA), leaf nutrient concentration and photosynthesis (Asat) were measured. Important Findings Results indicated that leaf traits and photosynthesis were affected differently by elevated [CO2] and N fertilization among species. Elevated [CO2] decreased LMA in all species, while N fertilization did not affect LMA. Leaf mass-based N concentration (NM) was significantly greater in O. pinnata and C. hystrix grown in elevated [CO2] but was lower in S. superba. Leaf mass-based P concentration (PM) was significantly greater in C. hystrix and A. acuminatissima exposed to elevated [CO2] but was lower in S. superba. N fertilization significantly increased PM in O. pinnata but decreased PM in S. superba. Photosynthetic stimulation in O. pinnata, C. hystrix and A. acuminatissima was sustained after 5 years of CO2 fumigation. N fertilization did not modify the effects of elevated [CO2] on photosynthesis. Leaf traits (NM ,N A ,P M ,P A) and light-saturated photosynthesis were decreased from the upper to lower canopy. Canopy position did not alter the responses of leaf traits and photosynthesis to elevated [CO2]. Results suggest that photosynthetic stimulation by elevated [CO2] in native species in subtropical regions may be sustained in the long term.

Trait-based community assembly of understory palms along a soil nutrient gradient in a lower montane tropical forest

Two opposing niche processes have been shown to shape the relationship between ecological traits and species distribution patterns: habitat filtering and competitive exclusion. Habitat filtering is expected to select for similar traits among coexisting species that share similar habitat conditions, whereas competitive exclusion is expected to limit the ecological similarity of coexisting species leading to trait differentiation. Here, we explore how functional traits vary among 19 understory palm species that differ in their distribution across a gradient of soil resource availability in lower montane forest in western Panama. We found evidence that habitat filtering influences species distribution patterns and shifts community-wide and intraspecific trait values. Differences in trait values among sites were more strongly related to soil nutrient availability than to variation in light or rainfall. Soil nutrient availability explained a significant amount of variation in site mean trait values for 4 of 15 functional traits. Site mean values of leaf nitrogen and phosphorus increased 37 and 64%, respectively, leaf carbon:nitrogen decreased 38%, and specific leaf area increased 29% with increasing soil nutrient availability. For Geonoma cuneata, the only species occurring at all sites, leaf phosphorus increased 34% and nitrogen:phosphorus decreased 42% with increasing soil nutrients. In addition to among-site variation, most morphological and leaf nutrient traits differed among coexisting species within sites, suggesting these traits may be important for niche differentiation. Hence, a combination of habitat filtering due to turnover in species composition and intraspecific variation along a soil nutrient gradient and site-specific niche differentiation among co-occurring species influences understory palm community structure in this lower montane forest.

Changes in leaf nutrient traits in a wildfire chronosequence

The effect of wildfire on ecosystem function is gaining interest since climate change is expected to increase fire frequency and intensity in many forest systems. Fire alters the nutritional status of forest ecosystems, affecting ecosystem function and productivity, but further studies evaluating changes in leaf nutrient traits induced by forest wildfires are still needed. We used a 17-year-old Pinus canariensis wildfire chronosequence to elucidate the nature of nutrient limitations in natural and unmanaged pine forest in the Canary Islands. Pine needles were sampled in winter and spring and analysed for N and P concentrations. As expected, we found the lowest leaf N and leaf P in recently burned plots. However, the leaf N:P ratio was higher in burned versus unburned plots, suggesting that the decrease in P availability due to the fire is larger than that of N. For all leaf traits and sampling dates, leaf trait values in burned plots matched those observed in unburned plots 17 years after a fire. The N:P ratio found in P. canariensis needles was one of the lowest values reported in the literature for woody species, and suggests that all pine trees in the chronosequence are unambiguously limited by low N availability. Our results show that these N-limited pine forests retained N more efficiently than P 4 years after a wildfire; however, leaf N recovery is slower than P recovery, suggesting that the mechanisms responsible for pine N limitation operate continuously in these forests.

Spatial patterns of leaf nutrient traits of the plants in the Loess Plateau of China

The spatial patterns of leaf nutrient traits of plants in seven sites, Yangling, Yongshou, Tongchuan, Fuxian, Ansai, Mizhi and Shenmu, standing from south to north in the Loess Plateau of China, were studied. The results showed that of the 126 plant samples in the Loess Plateau, the mean leaf organic carbon (C), nitrogen (N), phosphorus (P) and potassium (K) were 43.8, 2.41, 0.16 and 1.67%, respectively, and ranked in the order of C > N > K > P. Leaf C, N, P and K ranged from 32.6 to 54.8%, 0.82 to 4.58%, 0.06 to 0.35%, and 0.24 to 4.21%, respectively. The mean leaf C/N, C/P and N/P ratios were 21.2, 312 and 15.4, respectively. It is indicated that leaf N in the Loess Plateau was significantly higher than those in Chinese and global flora, but leaf P was significantly lower than that in global flora, which resulted in a higher N/P ratio in the Loess Plateau. The results also showed that leaf C, N, P, K, C/N and C/P ratios varied significantly among the seven life-form groups, which were trees, shrubs, herbages, evergreen trees, deciduous trees, C-3 and C-4 herbages, but leaf N/P ratio differed little among the seven life-forms. In the sampled species in the Loess Plateau, leaf C was negatively correlated with leaf N, P and K, while leaf N, P and K were positively correlated with one another. In general, leaf N/P ratio increased as the latitude and annual solar radiation increased and the mean annual rainfall and mean annual temperature decreased.