Extreme defoliation reduces tree growth but not C and N storage in a winter-deciduous species
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Background and Aims There is a growing concern about how forests will respond to increased herbivory associated with climate change. Carbon (C) and nitrogen (N) limitation are hypothesized to cause decreasing growth after defoliation, and eventually mortality. This study examines the effects of a natural and massive defoliation by an insect on mature trees' C and N storage, which have rarely been studied together, particularly in winter-deciduous species. Methods Survival, growth rate, carbon [C, as non-structural carbohydrate (NSC) concentration] and nitrogen (N) storage, defences (tannins and total polyphenols), and re-foliation traits were examined in naturally defoliated and non-defoliated adult trees of the winter-deciduous temperate species Nothofagus pumilio 1 and 2 years after a massive and complete defoliation caused by the caterpillar of Ormiscodes amphimone (Saturniidae) during summer 2009 in Patagonia. Key Results Defoliated trees did not die but grew significantly less than non-defoliated trees for at least 2 years after defoliation. One year after defoliation, defoliated trees had similar NSC and N concentrations in woody tissues, higher polyphenol concentrations and lower re-foliation than non-defoliated trees. In the second year, however, NSC concentrations in branches were significantly higher in defoliated trees while differences in polyphenols and re-foliation disappeared and decreased, respectively. Conclusions The significant reduction in growth following defoliation was not caused by insufficient C or N availability, as frequently assumed; instead, it was probably due to growth limitations due to factors other than C or N, or to preventative C allocation to storage. This study shows an integrative approach to evaluating plant growth limitations in response to disturbance, by examining major resources other than C (e.g. N), and other C sinks besides storage and growth (e.g. defences and re-foliation).Keywords:
Condensed tannin
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Increases in leaf mass per area (LMA) are commonly observed in response to environmental stresses and are achieved through increases in leaf thickness and/or leaf density. Here, we investigated how the two underlying components of LMA differ in relation to species native climates and phylogeny, across deciduous and evergreen species. Using a phylogenetic approach, we quantified anatomical, compositional and climatic variables from 40 deciduous and 45 evergreen Quercus species from across the Northern Hemisphere growing in a common garden. Deciduous species from shorter growing seasons tended to have leaves with lower LMA and leaf thickness than those from longer growing seasons, while the opposite pattern was found for evergreens. For both habits, LMA and thickness increased in arid environments. However, this shift was associated with increased leaf density in evergreens but reduced density in deciduous species. Deciduous and evergreen oaks showed fundamental leaf morphological differences that revealed a diverse adaptive response. While LMA in deciduous species may have diversified in tight coordination with thickness mainly modulated by aridity, diversification of LMA within evergreens appears to be dependent on the infrageneric group, with diversification in leaf thickness modulated by both aridity and cold, while diversification in leaf density is only modulated by aridity.
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Leaf growth patterns were studied in three pairs of evergreen and deciduous species, occuiring at an elevation of 2025-2150 m in the Kumaon Himalaya. Leaf initiation occurred earlier in evergreens with an exception of Litsea umbrosa . Peak leaf pool size was attained earlier in deciduous species (June to early July), while later (October) in evergreen species. Rate of leaf expansion was higher in deciduous species. Specific leaf mass in the initial period was higher in evergreen species than in deciduous species. Leaf area was higher in deciduous species as compared to evergreen species, while root length/leaf area unit was greater in evergreen species.
Evergreen forest
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Leaf demography was studied in 9 trees (6 Evergreen (ES), 1 Semideciduous (SD) and 2 Deciduous (DS)) and 10 shrubs (7 Evergreen (ES) and 3 Deciduous (DS)) occurring between 350 to 2500 m elevation in the Kumaun Himalaya, India. Although each species had its own pattern about seasonality of leaf recruitment, it was possible to group the species based on leaf expansion behavior. The result shows the leaf expansion rate was greater for deciduous species compared to Evergreen species. The percent leaf area after four weeks of expansion was also greater for deciduous species.
Evergreen forest
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Stomatal Conductance
Ecophysiology
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Generally, deciduous and evergreen trees coexist in subtropical forests, and both types of leaves are attacked by numerous insect herbivores. However, trees respond and defend themselves from herbivores in different ways, and these responses may vary between evergreen and deciduous species. We examined both the percentage of leaf area removed by herbivores as well as the percentage of leaves attacked by herbivores to evaluate leaf herbivore damage across 14 subtropical deciduous and evergreen tree species, and quantified plant defenses to varying intensities of herbivory. We found that there was no significant difference in mean percentage of leaf area removed between deciduous and evergreen species, yet a higher mean percentage of deciduous leaves were damaged compared to evergreen leaves (73.7% versus 60.2%). Although percent leaf area removed was mainly influenced by hemicellulose concentrations, there was some evidence that the ratio of non-structural carbohydrates:lignin and the concentration of tannins contribute to herbivory. We also highlight that leaf defenses to varying intensities of herbivory varied greatly among subtropical plant species and there was a stronger response for deciduous trees to leaf herbivore (e.g., increased nitrogen or lignin) attack than that of evergreen trees. This work elucidates how leaves respond to varying intensities of herbivory, and explores some of the underlying relationships between leaf traits and herbivore attack in subtropical forests.
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We analyzed the ratio of evergreen to deciduous trees in eight urban parks based on the landscape plant resources survey of Beijing. The results show that the ratio and projected area ratio of evergreen to deciduous trees among the eight urban parks were different because of different characteristics of parks. But the ratio of evergreen to deciduous trees was mainly below 1∶1 with an average ratio of 1∶3, and the ratio of projected area was 1∶2, indicating that there are more deciduous trees than evergreen trees in urban parks, and the change of seasonal phase is obvious.
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Study was made on C,N,P content in leaf of evergreen and deciduous trees in evergreen broad-leaved forest at E’mei Mountain,Sichuan province and relationship among them.The result showed that mean content of C,N,P in evergreen species was respectively 42.30%,1.46% and 0.10%,while that in deciduous one was 41.078%,1.59% and 0.12%.N content in the tested forest leaves had close relation with P content,while no evident relation between C and N,C and P.The average N and P ratio in leaf from evergreen species was 14.48 and 13.61 from deciduous ones,indicating low adaptive faculty to local ecological environment.
Evergreen forest
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Acorn
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Abstract Aims Generally, deciduous and evergreen trees coexist in subtropical forests, and both types of leaves are attacked by numerous insect herbivores. However, trees respond to and defend themselves from herbivores in different ways, and these responses may vary between evergreen and deciduous species. To understand tree responses to leaf herbivore attack under varying intensities of herbivory. Methods We examined both the percentage of leaf area removed by herbivores as well as the percentage of leaves attacked by herbivores to evaluate leaf herbivore damage across 15 subtropical deciduous and evergreen trees, quantified plant responses to varying intensities of herbivory and analyzed both leaf herbivore attack and leaf traits among species. Results We have found that there was a higher intensity of herbivory on deciduous species than evergreen species, both as percentage of leaf area removed and the percentage of leaves attacked. In addition, leaf herbivory was positively correlated with defensive traits (concentrations of tannin and lignin), and negatively correlated with nutrient content (ratios of NSC:lignin and NSC:cellulose), which may be largely attributed to long-term and frequent insect herbivore stress and potentially evolutionary arms races between plants and insects. Conclusions This study highlights that leaf responses to varying intensities of herbivory differed widely among subtropical plant species and there was a stronger defensive response for deciduous trees to leaf herbivore attack than that of evergreen trees. These results have implications for better understanding plant responses and defenses to varying intensities of herbivory, and reveal several underlying relationships between leaf traits and herbivory.
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