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Leaf Nitrogen Concentration (leaf + nitrogen_concentration)
Selected AbstractsLight gains and physiological capacity of understorey woody plants during phenological avoidance of canopy shadeFUNCTIONAL ECOLOGY, Issue 4 2005C. K. AUGSPURGER Summary 1Carbon gain during phenological avoidance of canopy shade by an understorey plant depends on the extent of avoidance, the leaf stage during avoidance, and whether young and old leaves can exploit greater light availability in spring and autumn. 2For Asimina triloba (L.) Dunal., Aesculus glabra Willd., Acer saccharum Marsh., Lindera benzoin (L.) Blume and Carpinus caroliniana Walt. in a deciduous forest in Illinois, USA, spring avoidance with leaves at full size ranged from 0 days for Asimina to 24 days for Aesculus, and brought 36,98% of estimated total annual irradiance. Autumn avoidance was non-existent to minimal in all species. 3Total chlorophyll reached maximum concentrations at the middle of leaf life span, and declined well before senescence. Leaf nitrogen concentrations and net photosynthetic capacity both peaked in youngest leaves during spring avoidance, and were low in old leaves during autumn avoidance. 4Aesculus had especially high photosynthetic capacity during precanopy closure, while Asimina had relatively low capacity in its later developing leaves. 5Young leaves of species with phenological avoidance can enhance C gain, while old leaves in autumn do not. Thus phenological avoidance in spring may enhance the persistence of understorey woody individuals of some species. [source] Responses of leaf nitrogen concentration and specific leaf area to atmospheric CO2 enrichment: a retrospective synthesis across 62 speciesGLOBAL CHANGE BIOLOGY, Issue 7 2002Xiwei Yin Abstract Knowledge of leaf responses to elevated atmospheric [CO2] (CO2 concentration) is integral to understanding interactions between vegetation and global change. This work deals with responses of leaf mass-based nitrogen concentration (Nm) and specific leaf area (SLA). It assesses the statistical significance of factors perceived as influential on the responses, and quantifies how the responses vary with the significant factors identified, based on 170 data cases of 62 species compiled from the literature. Resultant equations capture about 41% of the variance in the data for percent responses of Nm and SLA, or about 95% of the variance for Nm and SLA at 57,320% normal [CO2]; these performance statistics also hold for leaf area-based N concentration and specific leaf weight. The equations generalize that: (i) both Nm and SLA decline as [CO2] increases; (ii) proportional decline of Nm is greater with deciduous woody species and with plants of normally low Nm, increases with pot size in growth chamber and greenhouse settings and with temperature and photosynthetic photon flux density (PPFD), and is mitigated by N fertilization; and (iii) proportional decline of SLA depends on pot size and PPFD similarly to Nm, increases with leaf life span and water vapour pressure deficit in enclosed experiments, and decreases with prolonged exposure to elevated [CO2] among broadleaf woody species in field conditions. The results highlight great uncertainty in the percent-response data and reveal the potential feasibility to estimate Nm and SLA at various magnitudes of elevated [CO2] from a few key plant and environmental factors of broad data bases. [source] Prediction of species response to atmospheric nitrogen deposition by means of ecological measures and life history traitsJOURNAL OF ECOLOGY, Issue 1 2002Martin Diekmann Summary 1The main objective of this study was to predict the responses of vascular plant species to atmospheric nitrogen deposition and enhanced soil nitrogen levels. The study was carried out in deciduous forests located in three regions of southern Sweden. The abundance of vascular plants, as well as soil pH and nitrogen mineralization rates, were studied in a total of 661 sample plots. 2We calculated an ecological measure (Ndev value) for all species based on their observed vs. expected nitrification ratios at a given soil pH, and compared its accuracy in predicting abundance changes with results using life history traits. Data from long-term field studies and fertilization experiments were used for validation. 3Ndev values were positively correlated between neighbouring regions. Values for the southernmost region (Skćne) were also positively related to the changes in species frequency observed in large-scale flora surveys and permanent plot studies in that area and with species changes reported from Central Europe. Values from one of two other regions were also consistent. Ndev values from Skćne (but no other region) predicted species responses in short-term fertilization experiments. 4No life history trait was as good a predictor as Ndev, although plant height, leaf anatomy, leaf nitrogen concentration and phenology showed significant correlations. Attributes related to taxonomy, life form, relative growth rate and habitat type showed no agreement with the changes in species abundance. 5We predict that species with the following attribute syndrome will increase in abundance in response to enhanced nitrogen levels: those favoured by a high soil nitrification ratio relative to other species at a given soil pH, tall stature, hydro- to helomorph anatomy, high leaf nitrogen concentration and a late phenological development. [source] Acclimation of photosynthetic capacity to irradiance in tree canopies in relation to leaf nitrogen concentration and leaf mass per unit areaPLANT CELL & ENVIRONMENT, Issue 3 2002P. Meir Abstract The observation of acclimation in leaf photosynthetic capacity to differences in growth irradiance has been widely used as support for a hypothesis that enables a simplification of some soil-vegetation-atmosphere transfer (SVAT) photosynthesis models. The acclimation hypothesis requires that relative leaf nitrogen concentration declines with relative irradiance from the top of a canopy to the bottom, in 1 : 1 proportion. In combination with a light transmission model it enables a simple estimate of the vertical profile in leaf nitrogen concentration (which is assumed to determine maximum carboxylation capacity), and in combination with estimates of the fraction of absorbed radiation it also leads to simple ,big-leaf' analytical solutions for canopy photosynthesis. We tested how forests deviate from this condition in five tree canopies, including four broadleaf stands, and one needle-leaf stand: a mixed-species tropical rain forest, oak (Quercus petraea (Matt.) Liebl), birch (Betula pendula Roth), beech (Fagus sylvatica L.) and Sitka spruce (Picea sitchensis (Bong.) Carr). Each canopy was studied when fully developed (mid-to-late summer for temperate stands). Irradiance (Q, ”mol m,2 s,1) was measured for 20 d using quantum sensors placed throughout the vertical canopy profile. Measurements were made to obtain parameters from leaves adjacent to the radiation sensors: maximum carboxylation and electron transfer capacity (Va, Ja, ”mol m,2 s,1), day respiration (Rda, ”mol m,2 s,1), leaf nitrogen concentration (Nm, mg g,1) and leaf mass per unit area (La, g m,2). Relative to upper-canopy values, Va declined linearly in 1 : 1 proportion with Na. Relative Va also declined linearly with relative Q, but with a significant intercept at zero irradiance (P < 0·01). This intercept was strongly related to La of the lowest leaves in each canopy (P < 0·01, r2 = 0·98, n= 5). For each canopy, daily lnQ was also linearly related with lnVa(P < 0·05), and the intercept was correlated with the value for photosynthetic capacity per unit nitrogen (PUN: Va/Na, ”mol g,1 s,1) of the lowest leaves in each canopy (P < 0·05). Va was linearly related with La and Na(P < 0·01), but the slope of the Va : Na relationship varied widely among sites. Hence, whilst there was a unique Va : Na ratio in each stand, acclimation in Va to Q varied predictably with La of the lowest leaves in each canopy. The specific leaf area, Lm(cm2 g,1), of the canopy-bottom foliage was also found to predict carboxylation capacity (expressed on a mass basis; Vm, ”mol g,1 s,1) at all sites (P < 0·01). These results invalidate the hypothesis of full acclimation to irradiance, but suggest that La and Lm of the most light-limited leaves in a canopy are widely applicable indicators of the distribution of photosynthetic capacity with height in forests. [source] Seven-Year Results of Thinning and Burning Restoration Treatments on Old Ponderosa Pines at the Gus Pearson Natural AreaRESTORATION ECOLOGY, Issue 2 2004Kimberly F. Wallin AbstractWe examined the 7-year effects of three restoration treatments on leaf physiology and insect-resistance characteristics of pre-settlement age ponderosa pines (Pinus ponderosa Dougl. ex Laws.) at the Gus Pearson Natural Area (GPNA) in northern Arizona. Restoration treatments were: (1) thinned in 1993 to approximate pre-Euro-American settlement stand structure, (2) thinned plus prescribed burned in 1994 and 1998, and (3) untreated control. Tree physiological and insect-resistance characteristics were measured in year 2000, 7 years after thinning, using the same procedures as an earlier study performed in 1996. Consistent with the 1996 results, pre-dawn water potential in 2000 was consistently lower in the control than both thinned treatments. Both thinned treatments continued to have increased foliar nitrogen concentration in leaves 7 years after treatment. However lower leaf nitrogen concentration in the thinned and burned compared with the thinned treatment suggests lower nitrogen availability to trees in repeatedly burned plots. Analysis of leaf gas exchange characteristics and carbon isotope content (,13C) suggests continued stimulation of photosynthesis by both thinning treatments. Differences among treatments in resin volume, a measure of bark beetle resistance, depended on season of measurement. Trees in both thinning treatments continued to have increased leaf toughness, a measure of resistance to insect folivores. Our results show that many beneficial effects of restoration treatments on carbon, water, and nitrogen relations and insect-resistance characteristics of pre-settlement ponderosa pines continue to be expressed 7 years after treatment at the GPNA. [source] Protected raspberry production accelerates onset of oviposition by vine weevils (Otiorhynchus sulcatus)AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 3 2010Scott N. Johnson 1Soft fruit production is increasingly reliant on crops that are grown under the protection of plastic tunnels, which may also affect insect communities as a result of localized climate change and changes to host plant physiology and chemistry. In particular, insect development rates may differ from field populations, making it more difficult to target control measures. 2The present study investigated how protected environments affected adult vine weevil (Otiorhynchus sulcatus) feeding and reproduction on red raspberry (Rubus idaeus). We focused on the period between adult emergence and the onset of oviposition (i.e. the pre-reproductive period), which represents the optimal period for control. 3Tunnels were up to 4 °C warmer than field plantations in 2008, with plants growing significantly faster (50% increase in height and 16% increase in leaf area) than field grown plants. The carbon/nitrogen ratio in leaves was higher in tunnels (12.07) than the field (10.89) as a result of a significant decrease in nitrogen concentrations (3.40 and 3.90 mg g,1, respectively). 4Over 4 weeks, weevils consumed significantly more foliage in tunnels (370.89 mg) than weevils in the field (166.68 mg), suggesting compensatory feeding to counteract lower leaf nitrogen concentrations. Weevils in tunnels achieved sexual maturity 8 days earlier than those in the field and produced 20-fold more eggs by the time they were 5 weeks old. 5Applying a degree-day model showed good agreement between predicted and observed pre-reproductive periods for weevils in tunnels (36 and 30 days, respectively) and in field plots (41 and 38 days, respectively). [source] | ||||||||||