Evergreen Tree Species Research Articles

Leaf magnetic properties as a method for predicting heavy metal concentrations in PM2.5 using support vector machine: A case study in Nanjing, China

The aim of this study was to establish a method for predicting heavy metal concentrations in PM2.5 (particulate matter with a diameter of less than 2.5 μm) using support vector machine (SVM) models combined with magnetic properties of leaves. In this study, PM2.5 samples and the leaves of three common evergreen tree species were collected simultaneously during four different seasons in Nanjing, China. A SVM algorithm was used to establish models for the prediction of airborne heavy metal concentrations based on leaf magnetic properties, with or without meteorological factors and pollutant concentrations as input variables. Results showed that the annual average PM2.5 concentration was 58.47 μg/m3. PM2.5 concentrations, leaf magnetic properties, and nearly all airborne heavy metals had higher concentrations in winter than in spring, summer, or fall. Ferrimagnetic minerals preponderant in dust-loaded leaves were sampled from the three tree species. Models using magnetic properties of leaves from Ligustrum lucidum Ait and Osmanthus fragrans Lour yielded better prediction effects than those based on the leaves of Cedar deodara G. Don, showing relatively higher correlation coefficient (R) values and lower errors in both training and test stages. Fe and Pb concentrations were well-simulated by the prediction models, with R values > 0.7 in both training and test stages. By contrast, the concentrations of V, Co, Sb, Tl, and Zn were relatively poor-simulated, with most R values < 0.7 in both training and test stages. Predictions for the main urban areas of Nanjing showed that the highest heavy metal concentrations occurred near industrial and traffic pollution sources. Our results provide a cost-effective approach for the prediction of airborne heavy metal concentrations based on the biomagnetic monitoring of tree leaves.

Size-dependent variations in individual traits and trait scaling relationships within a shade-tolerant evergreen treespecies.

The plant size-trait relationship is a fundamental dimension in the spectrum of plant form and function. However, it remains unclear whether the trait scaling relationship within species is modified by tree size. Investigating size-dependent trait covariations within species is crucial for understanding the ontogenetic constraints on the intraspecific economic spectrum and, more broadly, the structure and causes of intraspecific trait variations. We measured eight morphological, stoichiometric, and hydraulic traits for 604 individual plants of a shade-tolerant evergreen tree species, Litsea elongata, in a subtropical evergreen forest of eastern China. Individual trait values were regressed against tree basal diameter to evaluate size-dependent trait variations. Standardized major axis regression was employed to examine trait scaling relationships and to test whether there was a common slope and elevation in the trait scaling relationship across size classes. Small trees tended to have larger, thinner leaves and longer, slenderer stems than larger trees, which indicates an acquisitive economic strategy in juvenile trees. Leaf nitrogen concentrations increased with plant size, which was likely due to a high ratio of structural to photosynthetic nitrogen in the evergreen leaves of large trees. Bivariate trait scaling was minimally modified by tree size, although the elevation of some relationships differed between size classes. Our results suggest that there are common economic and biophysical constraints on intraspecific trait covariation, independent of tree size. Small and large trees tend to be located at opposite ends of an intraspecific plant economic spectrum.

Start codon targeted (SCoT) polymorphism for evaluation of genetic diversity of wild population of Maytenus emarginata

Maytenus emarginata (Willd.) Ding Hou (family Celastraceae), an evergreen and multipurpose tree species of Indian Thar Desert, is a promising source of anticancer agents i.e. sesquiterpene pyridine alkaloid Emarginatine B and Emarginatine F. The knowledge of the genetic diversity of M. emarginata is important for the selection of appropriate genotype with medicinal interest. However, the genetic analysis or breeding system of M. emarginata remains unrevealed, therefore, it is difficult to draw any conclusion regarding its natural genetic diversity, gene flow or genetic differentiation. In the present investigation, start codon targeted polymorphism technique was used first time to examine the genetic diversity of M. emarginata. A total of 51 individuals comprising seven populations, collected from the larger geographical area of arid, semiarid and sub humid regions of western Rajasthan, India, were tested for existing natural genetic diversity in M. emarginata. Of 36 primers screened, 12 SCoT markers produced a total 156 amplicons ranging from 8 to 17 per primer, of which 114 (73%) were polymorphic. Average polymorphic information content, Nei’s gene diversity (h), Shannon index (I) and Percentage of polymorphic loci (Pp) were 0.517, 0.171, 0.257 and 49.54, respectively. Results revealed high level of genetic differentiation (Gst − 0.223) and the gene flow v (Nm − 1.74) in M. emarginata populations. Analysis of molecular variance showed that percent molecular variance was higher within population (84%) than among population (16%). The cluster analysis carried out by unweighted pair-group with arithmetic mean and the principal coordinate analysis showed high genetic variation among the genotypes and clustered all 51 genotypes into four major clusters while two genotypes in separate groups. High degree of genetic diversity in genotypes/populations may be useful in conservation program and selection of appropriate genotypes for exploitation of this important tree of Indian Thar desert.

Mosses Are Better than Leaves of Vascular Plants in Monitoring Atmospheric Heavy Metal Pollution in Urban Areas

Mosses and leaves of vascular plants have been used as bioindicators of environmental contamination by heavy metals originating from various sources. This study aims to compare the metal accumulation capabilities of mosses and vascular species in urban areas and quantify the suitability of different taxa for monitoring airborne heavy metals. One pleurocarpous feather moss species, Haplocladium angustifolium, and two evergreen tree species, Cinnamomum bodinieri Osmanthus fragrans, and substrate soil were sampled in the urban area of different land use types in Wuhan City in China. The concentrations of Ag, As, Cd, Co, Cr, Cu, Mn, Mo, Ni, V, Pb, and Zn in these samples were analyzed by inductively coupled plasma mass spectrometry. The differences of heavy metals concentration in the three species showed that the moss species was considerably more capable of accumulating heavy metals than tree leaves (3 times to 51 times). The accumulated concentration of heavy metals in the moss species depended on the metal species and land use type. The enrichment factors of metals for plants and the correlations of metals in plants with corresponding metals in soil reflected that the accumulated metals in plants stemmed mostly from atmospheric deposition, rather than the substrate soil. Anthropogenic factors, such as traffic emissions from automobile transportation and manufacturing industries, were primarily responsible for the variations in metal pollutants in the atmosphere and subsequently influenced the metal accumulation in the mosses. This study elucidated that the moss species H. angustifolium is relatively more suitable than tree leaves of C. bodinieri and O. fragrans in monitoring heavy metal pollution in urban areas, and currently Wuhan is at a lower contamination level of atmospheric heavy metals than some other cities in China.

Morinda citrifolia L. (Rubiaceae): a multi-purpose tree for coastal ecosystems and its variability in Konkan region of India

Noni (Morinda citrifolia L.) or Indian mulberry is an evergreen tree species of coastal tropics and has several uses as herbal medicine, cosmetic, vegetable, animal feed, dye and timber. It is a storehouse of useful phytochemicals including caprylic acid, damnacanthal, lineolic acid, morindine, octonic acid and xeronine. The species is hardy, tolerant to shade and salinity hence suitable for marginal lands of tropical coastal ecosystem. Nineteen accessions of noni were collected across the Konkan coast of Goa and Maharashtra states of western India. They are conserved in Indian National Gene Bank assigned with national identity as indigenous collection (IC) numbers viz., IC 0595272 to IC 0595277; IC 0598228 to IC 0598231; IC 0598515 to IC 0598516; IC 0598232 to IC 0598235; IC 0612951 to IC 0612953. The field grown germplasm accessions were characterised using quantitative traits of stem, leaf, flower, fruit and seeds. High degree of variation was recorded for fruit weight and number of seeds per fruit. The results are discussed in the light of evolution, dispersal and utilization. This report aims to summarize the various reports on uses, composition of phytochemcials, and diversity of noni to harness its utilization by increasing human inhabitants in tropical coastal lands.

Are storage and tree growth related? Seasonal nutrient and carbohydrate dynamics in evergreen and deciduous Mediterranean oaks

Seasonal dynamics of branch carbohydrates differed sharply between coexisting evergreen and deciduous Mediterranean oaks. Branch carbon storage was crucial in the evergreen, while it played a minor role in the deciduous oaks. The aim of this study was to describe the seasonal dynamics of nutrients and NSC in relation to the aboveground phenology of coexisting winter-deciduous (Quercus faginea) and evergreen (Quercus ilex subsp. ballota) oak species, and to analyse the relationship between the resource budget of branches and shoot growth. Monthly concentrations of nitrogen (N), phosphorus (P), potassium (K) and non-structural carbohydrates (NSC) plus the aboveground phenology of branches were measured over 2 years. We also analysed the correlation between the resource budget of branches prior to the growing season and the subsequent shoot and stem growth. Seasonal branch nutrient dynamics could be explained by shoot growth phenology, showing similar patterns across species. However, NSC dynamics varied between the two species, owing to the differences in leaf phenology and the contrasting role of branches as storage sites. NSC and N branch storage were crucial for the early stages of shoot growth in the evergreen trees. Accordingly, branch N and NSC storage pools in late winter correlated positively with spring growth, and NSC concentrations dropped during bud burst in all branch organs of Q. ilex. Contrastingly, branch NSC concentrations of the deciduous Q. faginea were only marginally affected by spring growth and no relationship was observed between branch N and NSC stores prior to bud burst. These results challenge previous assumptions on the lower relevance of branch NSC storage for the spring growth of evergreen trees and call for further studies where closely related pairs of coexisting evergreen and deciduous tree species are compared.

Effects of light and topography on regeneration and coexistence of evergreen and deciduous tree species in a Chinese subtropical forest

Abstract Evergreen broad‐leaved forests are widely distributed in eastern Asia with evergreen broad‐leaved (EBL) and deciduous broad‐leaved (DBL) tree species coexisting under the same climatic regime, raising questions as to the underlying mechanisms. Since EBL and DBL species differ in leaf life span, a key component of resource economic strategies, their coexistence might be attributed to regeneration niche partitioning across habitats varying in resource supply. We investigated the effects of variation in insolation and topography on regeneration of EBL and DBL species in a subtropical EBL forest of eastern China after an ice storm that caused severe canopy disturbance. Using a mixed‐effects modelling framework and census data from 2011 to 2014 on 8,548 wild seedlings of 123 species, we quantified habitat preferences of EBL and DBL species during post‐disturbance regeneration and how their survival and height relative growth rates varied among habitats. The relative density of DBL seedlings (proportional to all seedlings) was greater in habitats with greater (canopy gaps) compared to habitats with lesser (understorey) insolation and increased with canopy gap size. However, DBL seedlings were not more frequent in higher (valleys) compared to lower (ridges) fertility habitats. Although DBL seedlings exhibited larger differences in growth between higher and lower resource habitats than EBL seedlings, their growth rates did not increase with canopy gap size. Seedlings of EBL species had high survival in all habitats, but larger DBL seedlings survived equally well on ridges. Consequently, the relative density of DBL seedlings declined in valleys, so that by 2014 it became more similar in valley and ridge habitats, whereas it remained higher in gaps than in the understorey, and especially in larger gaps. Synthesis. Specialization on contrasting topographic habitats is considered the primary mechanism mediating coexistence between deciduous broad‐leaved and evergreen broad‐leaved species. Our results, however, suggest this may not always be true, since seedlings of deciduous broad‐leaved and evergreen broad‐leaved species partitioned regeneration niches based on light more so than topography. We propose that coexistence of deciduous broad‐leaved and evergreen broad‐leaved species can strongly depend upon canopy disturbance to create a mosaic of habitat patches, including high light gaps favouring regeneration of deciduous broad‐leaved species.

Impact of environmental factors on the decoupling coefficient and the estimation of canopy stomatal conductance for ever-green broad-leaved tree species

Impact of environmental factors on the decoupling coefficient and the estimation of canopy stomatal conductance for ever-green broad-leaved tree species

First detection of Vespa velutina nigrithorax (Hymenoptera: Vespidae) in the Balearic Islands (Western Mediterranean): a challenging study case

The yellow-legged hornet, Vespa velutina nigrithorax is an Invasive Alien Species introduced into Europe in 2004, and is currently present in France, Italy, Spain, Portugal, Germany, and Belgium. It was also recently introduced in the United Kingdom and Switzerland. Here we present the first detection of V. velutina in the westernmost Mediterranean islands (Majorca, Balearic archipelago). In October 2015, a specimen of hornet, which was later identified as V. velutina, was sent to the laboratory of Zoology at the University of the Balearic Islands by a beekeeper from the locality of Soller (northwest of Majorca). After the identification, and in coordination with the local authorities, an intensive survey was implemented in the area of first detection using sticky traps baited with protein and nest detection by directly observing the flight route of adult hornets from two or three feeding points. The first nest was detected on 30th October 2015 and was entirely removed. The next year, nine other nests were located from August to November 2016 in the same area and again, all of them were removed entirely. It is the first report on an island of destroying nests as a means of controlling the spread, a scenario very different to mainland Europe. All nests were detected in evergreen tree species (pines, holm oaks, and common cypress) in the “Serra de Tramuntana”, a mountain range located in the north-west of the island of Majorca (3667 km2), which is situated 176 km off the mainland. Considering the presumably early stage of the invasion of V. velutina in Majorca, the size of the island, and the confinement of the detection area, we consider that this species could be eradicated if resources and a specific program for eradication in Majorca are implemented in coordination with all involved partners.

Management Practice of Cinnamomum tamala in Eladi VDC of Syangja, Nepal

Cinnamomum tamala is a moderate sized evergreen tree species which is used as spices in Indian subcontinent. In Nepal, it is found between 500- 2000 m above sea level. Its English name is Indian cassia lignea or Cinnamon. Leaves and bark of the species contain aromatic oil and are used as spices. The status and distribution of this species has less explored so this study has been carried out to assess the resource base and management practice at Eladi VDC of Syangja district. The researcher estimated the existing stand of Sinkauli, its annual increment, the annual allowable harvest, density, relative density, frequency, relative frequency and abundance along with its ethnobotanical uses. Community forests, National forest and private forest consisting of Sinkauli stands were inventoried based on the stratified random sampling. The scattered trees in the farmland and marginal land were enumerated and mesured. The measurement of DBH were stratified into different size groups at the interval of 5 cm DBH class and at 5 years interval of age classes. Altogether 98 trees were sampled from 0.14 ha area. For the measurement of fresh weight and air-dried weight of bark and foliage, thirty two sample trees representing the Sinkauli stand, were felled and measured.&#x0D; Data were analyzed by using different statistical tools like mean, diagrams, flowcharts, and pie chart. The density, relative density, frequency, relative frequency, abundance and growing stock are 13171, 55.34%, 100%, 11.7%, 13171, 700 trees/ha respectively. The air-dried weight to fresh weight ratio of bark of C. tamala is found to be 0.5210 and that of leaf is 0.5721. From this VDC, 345 trees of average age could be harvested with which 2944 kg bark and 2409 kg of leaves could be extracted annually. Based on the existing price at the local market, Rs 1177,60 from bark (RS 40/ Kg) and Rs 36130 from foliage (Rs 15/ Kg) could be earned annually.&#x0D; As people are less aware about the importance of C.tamala and the resource is dwindling from natural stand, the awareness program for its proper management, cooperation among different stakeholders, provision of economic market, and development of proper monitoring and evaluation program are recommended for the sustainable management of C.tamala stands.

Effect of mass of organic layers on variation in 137Cs distribution in soil in different forest types after the Fukushima nuclear accident

ABSTRACT Forests over a wide area were contaminated with radiocesium following the Fukushima nuclear accident in March 2011. Most radiocesium in the forests migrated into the soil a year after the accident and it is therefore necessary to clarify the distribution pattern of radiocesium in soil to evaluate the actual state and possible future changes of the radiocesium cycle in forest ecosystems. We investigated the stock and vertical distribution patterns of 137Cs in soil under evergreen and deciduous tree species from 2012 to 2014 in a mountainous area in Fukushima Prefecture. The 137Cs stock in soil was higher in evergreen forests than in deciduous forests. This was likely caused by the difference in tree leaf biomass at the time of the initial deposition, when deciduous trees were defoliated. The organic layer (particularly the humified layer) retained 137Cs in high concentration and stock, indicating limited migration of 137Cs into the mineral layer during the study period. This may reflect the incorporation of 137Cs into organic matter and the retention of fungi in the organic layer. Analyses of these data and those from other studies conducted in regions contaminated by the accident showed that the ratio of radiocesium stock in the organic layer to the total amount in soil was positively correlated with the mass of the organic layer (organic layers with a mass of >2.0 kg/m2 retained more than 50% of total radiocesium). Thus, the status of the organic layer is an important factor regulating the downward migration of radiocesium.

Effects of elevated O3 on physiological and biochemical responses in three kinds of trees native to subtropical forest in China during non-growing period.

Numerous studies have documented the negative effects of ozone (O3) on tree species in growing season, however, little is done in non-growing season. Three evergreen tree species, Phoebe bournei (Hemsl.) Yang (P.bournei), Machilus pauhoi Kanehira (M.pauhoi) and Taxus chinensis (Pilger) Rehd (T.chinensis), were exposed to non-filtered air, 100nmolmol-1 O3 air (E1) and 150nmolmol-1 O3 air (E2) in open-top chambers in subtropical China. In the entire period of experiment, O3 fumigation decreased net photosynthesis rate (Pn) through stomatal limitation during the transition period from growing to non-growing season (TGN), and through non-stomatal limitation during the period of non-growing season (NGS) in all species tested. Meanwhile, O3 fumigation reduced and delayed the resilience of Pn in all species tested during the transition period from non-growing to growing season (TNG). O3 fumigation significantly decreased chlorophyll contents during NGS, whereas no obvious injury symptoms were observed till the end of experiment. O3 fumigation induced increases in levels of malondialdehyde, superoxide dismutase, total phenolics and reduced ascorbic acid, and changes in four plant endogenous hormones as well in all species tested during NGS. During NGS, E1 and E2 reduced Pn by an average of 80.11% in P.bournei, 94.56% in M.pauhoi and 12.57% in T.chinensis, indicating that the O3 sensitivity was in an order of M.pauhoi>P.bournei>T.chinensis. Overall, O3 fumigation inhibited carbon fixation in all species tested during NGS. Furthermore, O3-induced physiological activities also consumed the dry matter. All these suggested that elevated O3, which is likely to come true during NGS in the future, will adversely affect the accumulation of dry matter and the resilience of Pn during TNG in evergreen tree species, and further inhibit their growth and development in the upcoming growing season.

Manipulative experiments demonstrate how long-term soil moisture changes alter controls of plant water use

Tree transpiration depends on biotic and abiotic factors that might change in the future, including precipitation and soil moisture status. Although short-term sap flux responses to soil moisture and evaporative demand have been the subject of attention before, the relative sensitivity of sap flux to these two factors under long-term changes in soil moisture conditions has rarely been determined experimentally. We tested how long-term artificial change in soil moisture affects the sensitivity of tree-level sap flux to daily atmospheric vapor pressure deficit (VPD) and soil moisture variations, and the generality of these effects across forest types and environments using four manipulative sites in mature forests. Exposure to relatively long-term (two to six years) soil moisture reduction decreases tree sap flux sensitivity to daily VPD and relative extractable water (REW) variations, leading to lower sap flux even under high soil moisture and optimal VPD. Inversely, trees subjected to long-term irrigation showed a significant increase in their sensitivity to daily VPD and REW, but only at the most water-limited site. The ratio between the relative change in soil moisture manipulation and the relative change in sap flux sensitivity to VPD and REW variations was similar across sites suggesting common adjustment mechanisms to long-term soil moisture status across environments for evergreen tree species. Overall, our results show that long-term changes in soil water availability, and subsequent adjustments to these novel conditions, could play a critical and increasingly important role in controlling forest water use in the future.

How important is woody tissue photosynthesis in EuCahetus dunnii Maiden and Osmanthus fragrans (Thunb.) Lour. under O3 stress?

Numerous studies have demonstrated the negative effects of elevated O3 on leaf photosynthesis. Within trees, a portion of respired CO2 is assimilated by woody tissue photosynthesis, but its response to elevated O3 remains unclear. Saplings of two evergreen tree species, EuCahetus dunnii Maiden (E. dunnii) and Osmanthus fragrans (Thunb.) Lour. (O. fragrans), were exposed to non-filtered air (NF), 100nmolmol-1 O3 air (E1) and 150nmolmol-1 O3 air (E2) in open-top chambers from May 5 to September 5, 2016 (8h a day; 7days a week) in subtropical China. In this study, O3 fumigation significantly reduced leaf net photosynthesis rate in both two tree species on most measurements. However, compared with leaf net photosynthesis rate, woody tissue gross photosynthesis rate showed less negative response to O3 fumigation and was even stimulated to increase. Refixation rate reflects the utilization efficiency of the respired CO2 by woody tissue photosynthesis. During the experiment period, E1 and E2 both increased refixation rate in O. fragrans compared with NF. Whereas for E. dunnii, E1 increased refixation rate until 81days after starting of fumigation and then decreased it, and E2 decreased it all the time. Refixation rate had a significant positive correlation with woody tissue chlorophyll contents, indicating that the response of refixation rate to elevated O3 may relate to chlorophyll contents. All these suggested that under O3 fumigation, when atmospheric CO2 uptake and fixation by leaf is limited, woody tissue photosynthesis can contribute more to the total carbon assimilation in trees. The findings help to understand the significance of woody tissue photosynthesis under elevated O3 conditions.

Whole-tree distribution and temporal variation of non-structural carbohydrates in broadleaf evergreen trees.

Non-structural carbohydrates (NSCs) form a fundamental yet poorly quantified carbon pool in trees. Studies of NSC seasonality in forest trees have seldom measured whole-tree NSC stocks and allocation among organs, and are not representative of all tree functional types. Non-structural carbohydrate research has primarily focussed on broadleaf deciduous and coniferous evergreen trees with distinct growing seasons, while broadleaf evergreen trees remain under-studied despite their different growth phenology. We measured whole-tree NSC allocation and temporal variation in Eucalyptus obliqua L'Hér., a broadleaf evergreen tree species typically occurring in mixed-age temperate forests, which has year-round growth and the capacity to resprout after fire. Our overarching objective was to improve the empirical basis for understanding the functional importance of NSC allocation and stock changes at the tree- and organ-level in this tree functional type. Starch was the principal storage carbohydrate and was primarily stored in the stem and roots of young (14-year-old) trees rather than the lignotuber, which did not appear to be a specialized starch storage organ. Whole-tree NSC stocks were depleted during spring and summer due to significant decreases in starch mass in the roots and stem, seemingly to support root and crown growth but potentially exacerbated by water stress in summer. Seasonality of stem NSCs differed between young and mature trees, and was not synchronized with stem basal area increments in mature trees. Our results suggest that the relative magnitude of seasonal NSC stock changes could vary with tree growth stage, and that the main drivers of NSC fluctuations in broadleaf evergreen trees in temperate biomes could be periodic disturbances such as summer drought and fire, rather than growth phenology. These results have implications for understanding post-fire tree recovery via resprouting, and for incorporating NSC pools into carbon models of mixed-age forests.

Do temperate tree species diversity and identity influence soil microbial community function and composition?

Studies of biodiversity–ecosystem function in treed ecosystems have generally focused on aboveground functions. This study investigates intertrophic links between tree diversity and soil microbial community function and composition. We examined how microbial communities in surface mineral soil responded to experimental gradients of tree species richness (SR), functional diversity (FD), community‐weighted mean trait value (CWM), and tree identity. The site was a 4‐year‐old common garden experiment near Montreal, Canada, consisting of deciduous and evergreen tree species mixtures. Microbial community composition, community‐level physiological profiles, and respiration were evaluated using phospholipid fatty acid (PLFA) analysis and the MicroResp™ system, respectively. The relationship between tree species richness and glucose‐induced respiration (GIR), basal respiration (BR), metabolic quotient (qCO 2) followed a positive but saturating shape. Microbial communities associated with species mixtures were more active (basal respiration [BR]), with higher biomass (glucose‐induced respiration [GIR]), and used a greater number of carbon sources than monocultures. Communities associated with deciduous tree species used a greater number of carbon sources than those associated with evergreen species, suggesting a greater soil carbon storage capacity. There were no differences in microbial composition (PLFA) between monocultures and SR mixtures. The FD and the CWM of several functional traits affected both BR and GIR. In general, the CWM of traits had stronger effects than did FD, suggesting that certain traits of dominant species have more effect on ecosystem processes than does FD. Both the functions of GIR and BR were positively related to aboveground tree community productivity. Both tree diversity (SR) and identity (species and functional identity—leaf habit) affected soil microbial community respiration, biomass, and composition. For the first time, we identified functional traits related to life‐history strategy, as well as root traits that influence another trophic level, soil microbial community function, via effects on BR and GIR.

Leaf habit of tree species does not strongly predict leaf litter decomposition but alters climate-decomposition relationships

Leaf habit of tree species (evergreen versus deciduous) is proposed to be an important determinant of leaf litter decomposition, but it remains largely understudied as to how climatic regulation of litter decomposition differs between leaf habits. We isolated the relative role of climate and leaf habit in leaf litter decomposition by investigating the latitudinal pattern of leaf litter decomposition for Chinese broad-leaved tree species. Litter decomposition rate decreased with latitude, which was largely driven by mean annual temperature (MAT). Evergreen and deciduous broad-leaved tree species shared similar decomposition rate where they coexisted. Leaf litter decomposition of evergreen broad-leaved tree species was more sensitive to MAT than that of the deciduous species, whereas leaf litter decomposition of the deciduous trees was more sensitive than that of the evergreen to mean annual precipitation. Climatic variables explained more variation in leaf litter decomposition than did leaf habit alone. Our findings support the conventional paradigm that climate is a dominant regulator of leaf litter decomposition over broad geographical scales, notwithstanding recent studies calling into question this paradigm. While leaf habit alone does not predict leaf litter decomposition very well where both evergreen and deciduous species coexisted, the direction and strength of shift in leaf litter decomposition diverged between leaf habits across the climatic gradient. These findings underscore the urgent need to consider the impacts of changes in leaf habits when predicting leaf litter decomposition in response to climate change.

Seasonal and diel variations in the activity of canopy insect herbivores differ between deciduous and evergreen plant species in a tropical dry forest

This study evaluated whether herbivorous insects can be expected to have particular adaptations to withstand the harsh dry season in tropical dry forests (TDFs). We specifically investigated a possible escape in space, with herbivorous insects moving to the few evergreen trees that occur in this ecosystem; and escape in time, with herbivores presenting an increased nocturnal rather than diurnal activity during the dry season. We determined the variation in the free-feeding herbivorous insects (sap-sucking and leaf chewing) between seasons (beginning and middle of both rainy and dry seasons), plant phenological groups (deciduous and evergreen trees) and diel period (diurnal and nocturnal) in a Brazilian TDF. We sampled a total of 5827 insect herbivores in 72 flight-interception traps. Contrary to our expectations, we found a greater herbivore diversity during the dry season, with low species overlap among seasons. In the dry season, evergreen trees supported greater richness and abundance of herbivores as compared to deciduous trees. Insects were also more active at night during the dry season, but no diel differences in insect abundance were detected during the rainy season. These results indicate that the strategies used by insect herbivores to withstand the severe climatic conditions of TDFs during the dry season include both small-scale escape in space and time, with evergreen trees playing a key role in maintaining resident insect herbivore populations in TDFs. Relatively more nocturnal activity during the dry season may be related to the avoidance of harsh climatic conditions during the day. We suggest that the few evergreen tree species occurring in the TDF landscape should be especially targeted for protection in this threatened ecosystem, given their importance for insect conservation.

Physiological and biochemical responses of Machilus ichangensis Rehd. et Wils and Taxus chinensis (Pilger) Rehd. to elevated O3 in subtropical China

Considerable researches have documented the negative effects of ozone on woody species in North America and Europe; however, little is known about how woody tree species respond to elevated O3 in subtropical China, and most of the previous studies were conducted using pot experiment. In the present study, Machilus ichangensis Rehd. et Wils (M. ichangensis) and Taxus chinensis (Pilger) Rehd. (T. chinensis), evergreen tree species in subtropical China, were exposed to non-filtered air (NF), 100nmolmol-1 O3 (E1) and 150nmolmol-1 O3 (E2), in open-top chambers under field conditions from 21st March to 2nd November 2015. In this study, O3 fumigation significantly reduced net photosynthesis rate (Pn) in M. ichangensis in the three measurements and in T. chinensis in the last measurement. Also, non-stomatal factors should be primarily responsible for the decreased Pn. O3 fumigation-induced increase in malondialdehyde, superoxide dismutase, and reduced ascorbic acid levels indicated that antioxidant defense mechanism had been stimulated to prevent O3 stress and repair the oxidative damage. Yet, the increase of antioxidant ability was not enough to counteract the harm of O3 fumigation. Because of the decrease in CO2 assimilation, the growth of the two tree species was restrained ultimately. The sensitivity of the two tree species to O3 can be determined: M. ichangensis>T. chinensis. It suggests a close link between the rising O3 concentrations and the health risk of some tree species in subtropics in the near future.

Improving the classification of six evergreen subtropical tree species with multi-season data from leaf spectra simulated to WorldView-2 and RapidEye

ABSTRACTRemote sensing offers a feasible means to monitor tree species at a regional level where species distribution and composition is affected by the impacts of global change. Furthermore, the temporal resolution of space-borne multispectral sensors offers the ability to combine phenologically important phases for the optimization of tree species classification. In this study, we determined whether multi-seasonal leaf-level spectral data (winter, spring, summer, and autumn) improved the classification of six evergreen tree species in the subtropical forest region of South Africa when compared to a single season, for hyperspectral data, and reflectance data simulated to the WorldView-2 (WV2) and RapidEye (RE) sensors. Classification accuracies of the test data were assessed using a Partial Least Square Random Forest algorithm. The accuracies were compared between single seasons and multi-season classification and across seasons using analysis of variance and post-hoc Tukey Honest Significant Difference tests. The average overall accuracy (OA) of the leaf-level hyperspectral data ranged from a minimum of 90 ± 3.5% in winter to a maximum of 92 ± 2.7% in summer, outperforming the simulated reflectance data for the WV2 and RE sensors with an average OA of between 8 and 10 percentage points (p < 0.02, Bonferroni corrected). The use of data from multiple seasons increased the average OA and decreased the number of species pair confusions for the simulated multispectral classifications. The producer’s and user’s accuracies of the hyperspectral classification were >82% and showed no significant change using multi-season data. Multiple seasons may therefore be beneficial to multispectral sensors with ≤8 bands, yet remains to be tested at canopy level, for other species and climatic regions.