Pest and disease incidence of coniferous species in Taman Saujana Hijau,Putrajaya urban park,Malaysia

Taman Saujana Hijau(TSH),Putrajaya is a 41-ha urban park planted with various coniferous species from around the world.Insect pests and disease incidences of this park are unknown and there is a need for an evaluation of the health status of this urban park.This study assessed the level of pest and disease incidents of coniferous species in 12 plots of 7 species(Araucaria bidwilii,Araucaria haterophylla,Araucaria cunninghamii,Pinus caribaea,Pinus merkusii,Podocarpus polystachyus,and Podocarpus costalis).Termites,canker disease,and foliar disease are three major problems.The highest pest and disease incidence(PnDI)was foliar disease with a 0.49 coefficient correlation between the total number of trees and the PnDI,followed by canker disease with 0.40,and termites with 0.36.Of the seven conifers,A.haterophylla was the most infected followed by A.bidwilii and A.cunninghamii.It was concluded that the incidence of pests and diseases in TSH was moderate.To our knowledge,this may be the first baseline inventory of pests and diseases of coniferous species in Malaysia.

The Limiting Effect of Deep Soil Water on Evapotranspiration of a Subtropical Coniferous Plantation Subjected to Seasonal Drought

Seasonal drought is a common occurrence in humid climates.The year 2003 was the driest year during the period 1985-2011 in southeastern China.The objective of this study was to elucidate the impact of the exceptional drought in 2003,compared with eddy flux measurements during 2004-11,on the dynamics of evapotranspiration （ET） and related factors,as well as their underlying mechanisms,in a subtropical coniferous plantation in southeastern China.It was found that daily ET decreased from 5.34 to 1.84 mm during the intensive drought period and recovered to 4.80 mm during the subsquent recovering drought period.Path analysis indicated that ET was mainly determined by canopy conductance and deep soil water content （50 cm） during the intensive drought and recovering drought periods,respectively.The canopy conductance offset the positive effect of air vapor pressure deficit on ET when suffering drought stress,while the canopy conductance enhanced the positive effect of air temperature on ET during the late growing season.Because the fine roots of this plantation are mainly distributed in shallow soil,and the soil water in the upper 40 cm did not satisfy the demand for ET,stomatal closure and defoliation were evident as physiological responses to drought stress.

Abiotic and biotic drivers of species diversity in understory layers of cold temperate coniferous forests in North China

Understory plants are important components of forest ecosystems and play a crucial role in regulating community structures,function realization,and community succession.However,little is known about how abiotic and biotic drivers affect the diversity of understory species in cold temperate coniferous forests in the semiarid climate region of North China.We hypothesized that(1)topographic factors are important environmental factors affecting the distribution and variation of understory strata,and(2)different understory strata respond differently to environmental factors;shrubs may be significantly affected by the overstory stratum,and herbs may be more affected by surface soil conditions.To test these hypotheses,we used the boosted regression tree method to analyze abiotic and biotic environmental factors that influence understory species diversity,using data from 280 subplots across 56 sites in cold temperate coniferous forests of North China.Elevation and slope aspect were the dominant and indirect abiotic drivers affecting understory species diversity,and individual tree size inequality(DBH variation)was the dominant biotic driver of understory species diversity;soil water content was the main edaphic factors affecting herb layers.Elevation,slope aspect,and DBH variation accounted for 36.4,14.5,and 12.1%,respectively,of shrub stratum diversity.Shrub diversity decreased with elevation within the range of altitude of this study,but increased with DBH variation;shrub diversity was highest on north-oriented slopes.The strongest factor affecting herb stratum species diversity was slope aspect,accounting for 25.9%of the diversity,followed by elevation(15.7%),slope(12.2%),and soil water content(10.3%).The highest herb diversity was found on southeast-oriented slopes and the lowest on northeast-oriented slopes;herb diversity decreased with elevation and soil water content,but increased with slope.The results of the study provide a reference for scientific management and biodiversity protection in cold temperate coniferous forests of North China.

Active organic carbon pool of coniferous and broad-leaved forest soils in the mountainous areas of Beijing

In order to explore the effects of different forest types on active soil carbon pool, the amounts and density of soil organic carbon （SOC） were studied at different soil horizons under typical coniferous and broad-leaved forests in the mountainous area of Beijing. The results showed that the amount of total SOC, readily oxidizable carbon and particulate organic carbon decreased with increasing depths of soil horizons and the amounts at depths of 0-10 cm and 10-20 cm in broad-leaved forest was clearly higher than that in coniferous forests. The trend of a decrease in SOC density with increasing depth of the soil horizon was similar to that of the amount of SOC. However, no regular trend was found for SOC density at different depths between coniferous forest and broad-leaved forests. The ratio of readily oxidizable carbon to total amount of SOC ranged from 0.36-0.45 and the ratio of particulate organic carbon to total amount of SOC from 0.28-0.73; the ratios decreased with increasing depths of soil horizons. Active SOC was significantly correlated with total SOC; the relationship between readily oxidizable carbon and particulate organic carbon was significant. A broad-leaved forest may produce more SOC than a coniferous forest.

How do nitrogen-limited alpine coniferous forests acquire nitrogen?A rhizosphere perspective

Background:Alpine coniferous forest ecosystems dominated by ectomycorrhizal(ECM)tree species are generally characterized by low soil nitrogen(N)availability but stabilized plant productivity.Thus,elucidating potential mechanisms by which plants maintain efficient N acquisition is crucial for formulating optimized management practices in these ecosystems.Methods:We summarize empirical studies conducted at a long-term field monitoring station in the alpine coniferous forests on the eastern Tibetan Plateau,China.We propose a root-soil interaction-based framework encompassing key components including soil N supply,microbial N transformation,and root N uptake in the rhizosphere.Results:We highlight that,(i)a considerable size of soil dissolved organic N pool mitigates plant dependence on inorganic N supply;(ii)ectomycorrhizal roots regulate soil N transformations through both rhizosphere and hyphosphere effects,providing a driving force for scavenging soil N;(iii)a complementary pattern of plant uptake of different soil N forms via root-and mycorrhizal mycelium-pathways enables efficient N acquisitions in response to changing soil N availability.Conclusions:Multiple rhizosphere processes abovementioned collaboratively contribute to efficient plant N acquisition in alpine coniferous forests.Finally,we identify several research outlooks and directions to improve the understanding and prediction of ecosystem functions in alpine coniferous forests under on-going global changes.

Effect of thinning intensity on understory herbaceous diversity and biomass in mixed coniferous and broad-leaved forests of Changbai Mountain

Background:Herbs are an important part of the forest ecosystem,and their diversity and biomass can reflect the restoration of vegetation after forest thinning disturbances.Based on the near-mature secondary coniferous and broad-leaved mixed forest in Jilin Province Forestry Experimental Zone,this study analyzed seasonal changes of species diversity and biomass of the understory herb layer after different intensities of thinning.Results:The results showed that although the composition of herbaceous species and the ranking of importance values were affected by thinning intensity,they were mainly determined by seasonal changes.Across the entire growing season,the species with the highest importance values in thinning treatments included Carex pilosa,Aegopodium alpestre,Meehania urticifolia,and Filipendula palmata,which dominated the herb layer of the coniferous and broad-leaved mixed forest.The number of species,Margalef index,Shannon-Wiener index and Simpson index all had their highest values in May,and gradually decreased with months.Pielou index was roughly inverted“N”throughout the growing season.Thinning did not increase the species diversity.Thinning can promote the total biomass,above-and below-ground biomass.The number of plants per unit area and coverage were related to the total biomass,above-and below-ground biomass.The average height had a significantly positive correlation with herb biomass in May but not in July.However,it exerted a significantly negative correlation with herb biomass in September.The biomass in the same month increased with increasing thinning intensity.Total herb biomass,above-and below-ground biomass showed positive correlations with Shannon-Winner index,Simpson index and Pielou evenness index in May.Conclusions:Thinning mainly changed the light environment in the forest,which would improve the plant diversity and biomass of herb layer in a short time.And different thinning intensity had different effects on the diversity of understory herb layer.The findings provide theoretical basis and reference for reasonable thinning and tending in coniferous and broad-leaved mixed forests.

Species Diversity Based on Vertical Structure as Indicators of Artificial Restoration for Coniferous Forests in Southwest China

Five indices of species richness, species diversity and species evenness were used to assess a diversity of four types of coniferous forests undergone different artificial regeneration time. The study was based on the vertical structure of forests, involving growth-forms of total plants as well as vertical layers of woody plants. The results showed that, except for the fourth layer of woody plants, the vertical structure of the four forests exhibited significant difference in terms of their species richness, species diversity and species evenness, suggesting that a species diversity index provided more detailed information and was a better index reflecting the regeneration processes in this region. It was recommended that silvicultural management of artificially regenerated forests should be strengthened to conserve the biodiversity of the forests, optimize forest structure and, in the long run, promote sustainable development of forest ecosystems.

Responses of soil Collembolans to vegetation restoration in temperate coniferous and broad-leaved mixed forests

A total of 900 soil samples were collected from five habitats,including primary coniferous broad-leaved mixed forests,secondary coniferous broad-leaved mixed forests,secondary broad-leaved forests,secondary shrub forests,and cutover lands in spring,summer,and autumn to quantify responses of soil Collembolans(springtails)to the restoration of vegetation of temperate coniferous and broad-leaved mixed forests.The results reveal that the taxonomic composition of Collembolans varied in the different stages of vegetation restoration.Seasonal variations were in regard to their abundance and richness.High similarities existed in Collembola communities at different stages of vegetation restoration,and distribution patterns of Collembola taxa displayed an evenness throughout all habitats.Soil Collembolans tended to gather on litter layers and soil surface;the highest abundance was found in the upper 5 cm soil layer during the initial stages of vegetation recovery.Tomocerus,Proisotoma,and Folsomia genera responded positively to the restoration of vegetation.However,responses of Ceratophysella and Parisotoma genera were negative.In addition,the Onychiuridae family did not respond to the vegetation restoration process.It was concluded that restoration of vegetative cover can increase the abundance of soil Collembolans,but different genera respond differently.

ORDINATION AND GRADIENT ANALYSIS OF CONIFEROUS FOREST IN DAXINGANLING

In this paper,the quantitative approach is applied on the study of coniferous forestbased on the data which were collected by the field investigation in Daxinganling region.The mainpurpose is objectively to show the position of communities in the space and the relationship be-tween the community and environment.By means of ordination,it is found that dahurian larch for-est,mongolian scots pine forest and korean fir forest lie in different positions. Gradient analysis ofthree dominant types of conigerous forest has revealed the difference of ecological amplitude,thedifference is one of the important reasons that determine the different communities in the differentenvironment.

Analysis of solute preferential transport in a dark coniferous forest ecosystem of Gongga Mountain,Sichuan Province,southwestern China

We selected a dark coniferous forest ecosystem of Gongga Mountain in the upper reaches of the Yangtze River as our research area to study the preferential flow and solute preferential transport by adding the tracers KNO3 and KBr to the self-made soil column equipment in different ways to examine density and volume changes of inflows and outflows of a mass input （impulse input） and a stable, well-distributed input （step input））. The results showed that this dark coniferous forest ecosystem of Gongga Mountain is a typical area of preferential flow and solute preferential transport, a process that can be classified into five parts. A great amount of solute was transported at high speed as the result of preferential flow in the soil and caused the density of the solute in both deep water and in groundwater to rise rapidly, which definitely increased pollution in the deep soil layer.

In vitro cholinesterase inhibitory and antioxidant effect of selected coniferous tree species

Objective:To explore cholinesterase inhibitory and antioxidant effect of six coniferous trees(Abies bornmulleriana,Picea pungens,Juniperus communis,Cedrus libani,Taxus baccata,and Cupressus sempervirens var.horizantalis).Methods:Acetone(Ace),ethyl acetate(EtOAc),and ethanol(EtOH)extracts prepared from the needles and shoots of the six coniferous trees were screened for their acetylcholinesterase(AChE)and butyrylcholinesterasc(BChE)inhibitory activity at 100μg/mL.Antioxidant activity of the extracts was tested using 2,2-diphenyl-1-picrylhydrazyl(DPPH)and N,N-dimethyl-p-phenylendiamine(DMPD)radical scavenging,nietal-chelation capacity,ferric-(FRAP)and phosphomolibdenum-reducing antioxidant power(PRAP)assays.All of the assays were performed in ELISA microplate reader.Total phenol and flavonoid amounts in the extracts were determined spectrophotometrically.Results:Among thirty-six extracts in total,the shoot-Ace extract of Cupressus sempervirens var.horizantalis exerted the highest inhibition against AChE[(54.84±2.51)%],while the needle-Ace extract of Cedrus libani was the most effective in inhibiting BChE[(67.54±0.30)%].The highest DPPH radical scavenging effect,FRAP and PRAP was observed in the shoot-Ace and EtOAc extracts from Taxus baccata.whereas all the extracts showed a variable degree of scavenging effect against DPMD radical.The shoot-EtOAc extract of Cedrus libani had the highest metalchelation capacity[(58.04±0.70)%].The shoot extracts of Taxus baccata were determined to have the richest total phenol content,which may contribute to its marked antioxidant activity.Conclusions:The conifer species screened in this study may contain cholinesterase-inhibiting and antioxidant properties,which might be useful against Alzheimer's disease.

Electrochemically prepared coniferous leaf-like nickel black membrane for desalination by solar-thermal energy conversion

The structures of the solar-thermal membranes always influence the performance of light absorption and salt resistance in desalination.Inspired by the hierarchical structure of the coniferous leaves with excellent sunlight absorption in frigid regions,a coniferous leaf-like nickel black(L-Ni)membrane for desalination by solar-thermal energy conversion was prepared through electroplating method under a constant voltage.The light trapping effect of coniferous leaf-like structure led to the light absorption enhanced to 92%,the evaporation rate improved to 1.38 kg·m^(-2)·h^(-1),and the solar-vapor conversion efficiency of L-Ni membrane reaching up to 89.75%under 1 sun irradiation.The stability of the membrane was still excellent after 20 cycles desalination because the coniferous leaf-like structure could enhance the hydrophobicity(water contact angle:152°)of the L-Ni membrane,and it was beneficial to salt resistance.The promising performance of L-Ni membrane with coniferous leaf-like structure provides a possibility to replace the noble metal solar-thermal conversion materials.

Experimental study on N_2O and CH_4 fluxes from the dark coniferous forest zone soil of the Gongga Mountain, China

The static closed chamber technique is used in the study on the CH4 and N2O fluxes from the soils of primeval Abies fabri forest, the succession Abies fabri forest and the clear-cut areas of mid-aged Abies fabri forest in the Gongga Mountain from May 1998 to September 1999. The results indicate the following: (i) The forest soil serves as the source of atmospheric N2O at the three measurement sites, while the fluxes of CH4 are all negative, and soil is the sink of atmospheric CH4. The comparative relations of N2O emissions between the three sites are expressed as primeval Abies fabri forest > clear-cut areas > succession Abies fabri forest, and those of CH4 consumption fluxes are primeval Abies fabri forest > succession Abies fabri forest > clear-cut areas. (ii) Signifi-cant seasonal variations of N2O emission at various sites were observed, and two emission peaks of N2O occurr during summer (July—August) and spring (February—March), whereas N2O emission is relatively low in winter and spring (mid March—April). Seasonal variations of CH4 consumption at each measurement site fluctuate drastically with unclear regularities. Generally, CH4 consumption fluxes of succession Abies fabri forest and clear-cut areas are higher from mid May to late July but lower in the rest of sampling time, while the CH4 flux keeps a relatively high value even up to Sep-tember in primeval Abies fabri forest. In contrast to primeval Abies fabri forest, the CH4 absorbabili-ties of succession Abies fabri forest and clear-cut areas of mid-aged Abies fabri forest are weaker. Particularly, the absorbability of the clear-cut areas is even weaker as compared with the other two sites, for the deforestation reduces the soil absorbability of atmospheric CH4. (iii) Evident diurnal variation regularity exists in the N2O emissions of primeval Abies fabri forest, and there is a statistic positive correlation between the fluxes of N2O and air temperature (R=0.95, n=11, <0.01), and also the soil temperature of 5-cm layer (R=0.81, n=11, < 0.01), whereas the CH4 diurnal variation regularities are unclear and have no significant correlation with the soil temperature of 5-cm layer and air temperature.

Seasonal variation of CO_2 flux and its environmental factors in evergreen coniferous plantation

The effects of environmental factors on carbon flux were analyzed, the spatial and temporal variation of carbon flux was studied at the two heights of 23 m and 39 m with the eddy covariance technique, and the carbon budget was evaluated for evergreen coniferous plantation in the red earth hilly area during the year 2003. The results showed that photosynthetically active radiation (PAR) and soil temperature are essential factors strongly affecting the net ecosystem exchange (NEE); in the daytime, the response of NEE to PAR shows a rectangular hyperbola trend, and in the nighttime, the significant correlation was observed between soil temperature and soil respiration which was filtered using friction velocity. This ecosystem appeared as a carbon sink along the whole year of 2003, and the carbon flux showed the obvious seasonal fluctuation and diurnal variability. The seasonal peak of NEE occurred in May and June with the daily sum about 0.61-0.67 mg · CO2 · m-2 · s-1. For the severe drought in the mid-summer, the daily sum was 0.40-0.44 mg · CO2 · m-2 · s-1 in July which was only 2/3 of that in the last two months. For the lasted drought of the year, the nadir of NEE happened in the winder with the daily sum about -0.29 to -0.35 mg · CO2 · m-2 · s-1. The sink intensity of the ecosystem was about -0.553 to -0.645 kg · Cm-2 per year in 2003.

CO_2 flux evaluation over the evergreen coniferous and broad-leaved mixed forest in Dinghushan, China

The Dinghushan flux observation site, as one of the four forest sites of ChinaFLUX, aims to acquire long-term measurements of CO2 flux over a typical southern subtropical evergreen coniferous and broad-leaved mixed forest ecosystem using the open path eddy covariance method. Based on two years of data from 2003 to 2004, the characteristics of temporal variation in CO2 flux and its response to environmental factors in the forest ecosystem are analyzed. Provided two-dimensional coordinate rotation, WPL correction and quality control, poor energy-balance and underestimation of ecosystem respiration during nighttime implied that there could be a CO2 leak during the nighttime at the site. Using daytime (PAR 】 1.0μmol-1·m-2·s-1) flux data during windy conditions (u* 】 0.2 m·s-1), monthly ecosystem respiration (Reco) was derived through the Michaelis-Menten equation modeling the relationship between net ecosystem CO2 exchange (NEE) and photosynthetically active radiation (PAR). Exponential function was employed to describe the relationship between Reco and soil temperature at 5 cm depth (Ts05), then Reco of both daytime and nighttime was calculated respectively by the function. The major results are: (i) Derived from the Michaelis-Menten equation, the apparent quantum yield (α) was 0.0027±0.0011 mgCO2·μmol-1 photons, and the maximum photosynthetic assimilation rate (Amax) was 1.102±0.288 mgCO2·m-2·s-1. Indistinctive seasonal variation of o or Amax was consistent with weak seasonal dynamics of leaf area index (LAI) in such a lower subtropical evergreen mixed forest. (ii) Monthly accumulated Reco was estimated as 95.3±21.1 gC·m-2 mon-1, accounting for about 68% of the gross primary product (GPP). Monthly accumulated NEE was estimated as -43.2±29.6 gC·m-2·mon-1. The forest ecosystem acted as carbon sink all year round without any seasonal carbon efflux period. Annual NEE of 2003 and 2004 was estimated as -563.0 and -441.2 gC·m-2·a-1 respectively, accounting for about 32% of GPP.

A comparison between simulated and measured CO_2 and water flux in a subtropical coniferous forest

Using data from eddy covariance measurements in a subtropical coniferous forest, a test and evaluation have been made for the model of Carbon Exchange in the Vegetation-Soil-Atmosphere (CEVSA) that simulates energy transfers and water, carbon and nitrogen cycles based on ecophysiological processes. In the present study, improvement was made in the model in calculating LAI, carbon allocation among plant organs, litter fall, decomposition and evapotranspiration. The simulated seasonal variations in carbon and water vapor flux were consistent with the measurements. The model explained 90% and 86% of the measured variations in evapotranspiration and soil water content. However, the modeled evapotranspiration and soil water content were lower than the measured systematically, because the model assumed that water was lost as runoff if it was beyond the soil saturation water content, but the soil at the flux site with abundant rainfall is often above water saturated. The improved model reproduced 79% and 88% of the measured variations in gross primary production (GPP) and ecosystem respiration (Re), but only 31% of the variations in measured net ecosystem exchange (NEP) despite the fact that the modeled annual NEP was close to the observation. The modeled NEP was generally lower in winter and higher in summer than the observations. The simulated responses of photosynthesis and respiration to water vapor deficit at high temperatures were different from measurements. The results suggested that the improved model underestimated ecosystem photosynthesis and respiration in extremely condition. The present study shows that CEVSA can simulate the seasonal pattern and magnitude of CO2 and water vapor fluxes, but further improvement in simulating photosynthesis and respiration at extreme temperatures and water deficit is required.

Uncertainty analysis of CO_2 flux components in subtropical evergreen coniferous plantation

We present an uncertainty analysis of ecological process parameters and CO2 flux components (Reco, NEE and gross ecosystem exchange (GEE)) derived from 3 years’ continuous eddy covariance meas-urements of CO2 fluxes at subtropical evergreen coniferous plantation, Qianyanzhou of ChinaFlux. Daily-differencing approach was used to analyze the random error of CO2 fluxes measurements and bootstrapping method was used to quantify the uncertainties of three CO2 flux components. In addition, we evaluated different models and optimization methods in influencing estimation of key parameters and CO2 flux components. The results show that: (1) Random flux error more closely follows a dou-ble-exponential (Laplace), rather than a normal (Gaussian) distribution. (2) Different optimization meth-ods result in different estimates of model parameters. Uncertainties of parameters estimated by the maximum likelihood estimation (MLE) are lower than those derived from ordinary least square method (OLS). (3) The differences between simulated Reco, NEE and GEE derived from MLE and those derived from OLS are 12.18% (176 g C·m-2·a-1), 34.33% (79 g C·m-2·a-1) and 5.4% (92 g C·m-2·a-1). However, for a given parameter optimization method, a temperature-dependent model (T_model) and the models derived from a temperature and water-dependent model (TW_model) are 1.31% (17.8 g C·m-2·a-1), 2.1% (5.7 g C·m-2·a-1), and 0.26% (4.3 g C·m-2·a-1), respectively, which suggested that the optimization methods are more important than the ecological models in influencing uncertainty in estimated carbon fluxes. (4) The relative uncertainty of CO2 flux derived from OLS is higher than that from MLE, and the uncertainty is related to timescale, that is, the larger the timescale, the smaller the uncertainty. The relative uncertainties of Reco, NEE and GEE are 4%-8%, 7%-22% and 2%-4% respectively at annual timescale.

Ramet Population Structure of Fargesia nitida （Mitford） Keng f. et Yi in Different Successional Stands of the Subalpine Coniferous Forest in Wolong Nature Reserve

Forest structure and succession in Wolong Nature Reserve is influenced by the understory dwarf bamboo population. However, less is known about how the forest succession affects the dwarf bamboo population. To examine the bamboo ramet population growth of Fargesla nitida （Mltford） Keng f. et Yi and to determine how ramet population structure varies along the succession of coniferous forest, we sampled ramet populations of F. nitida from the following three successional stages： （i） a deciduous broad-leaved （BL） stand; （ii） a mixed broad-leaved coniferous （MI） stand; and （ill） a coniferous （CF） stand. We investigated the population structure, biomass allocation, and morphological characteristics of the bamboo ramet among the three stand types. Clonal ramets, constituting the bamboo population, tended to become short and small with succession. The ramet changed towards having a greater mass investment in leaves, branches and underground roots and rhizomes rather than in the culm. With respect to leaf traits, individual leaf mass and area in the BL stand were markedly bigger than those In both the MI and CF stands, except for no significant difference in specific leaf area. The age distribution showed that the bamboo population approached an older age with succession. The results demonstrate that the ramet population structure of F. nitida is unstable and its growth performance is inhibited by succession.

Assessing productivity and carbon sequestration capacity of subtropical coniferous plantations using the process model PnET-CN

A generalized, lumped-parameter ecological model PnET-CN was calibrated and validated for a subtropical coniferous plantation in southern China. PnET-CN model describes the biogeochemical cycles of carbon （C） and nitrogen （N） and can assist in estimating carbon sequestration potential. For validation of PnET-CN, data from coniferous forest plantations in southern China was used. Simulated daily gross primary productivity （GPP） from 2005 to 2007 agreed well with observations （R2=0.56, S.D.=0.009）. Simulations of monthly soil respiration （Rs） from 2005-2007 agreed well with Rs observations （R2=0.67, S.D. =0.03）. Simu- lated annual net primary productivity （NPP） from 1998-2006 was 803＋33 gCm 2a-1, about 4% higher than NPP observation （752＋51 gCm-2a-1）. Simulations of annual NEP from 2005-2007 only overestimate 9 gCm-2a-1 （4%）, 4 gCm 2a-1 （1%） and 34 gCm 2a-1 （8%） compared to NEP observations, respectively. Simulated annual foliar N concentration （FolNCon） （1.09%） is 10% lower than observed monthly FolNCon （0.87%-1.58%）. Simulated annual N leaching （0.26 gNm-2） is about 10% lower than leaching observation （0.29 gNm-2）. PnET-CN model validation indicates that PnET-CN is capable to simulate daily GPP, annual NPP, annual NEP, monthly Rs, annual FolNCon and annual nitrate N leaching for subtropical coniferous planta- tions in southern China. The results obtained from the validation test revealed that PnET-CN model can be used to simulate carbon sequestration of planted coniferous forests in southern China to a high level of precision. Sensitivity analysis suggests that great care should be taken in developing generalizations as to how forests will respond to a changing climate. PnET-CN performed satisfactorily in comparison to other models that have already been calibrated and validated in coniferous planted subtropical forests in China. Based on PnET-CN validation and its comparison to other models, future improvement of PnET-CN should focus on seasonal foliar N dynamics and the effects of water stress on autotrophic respirations in subtropical coniferous plantations in southern China.

Response of clonal plasticity of Fargesia nitida to different canopy conditions of subalpine coniferous forest

The aim of this study is to explore the effects of canopy conditions on clump and culm numbers,and the morphological plasticity and biomass distribution patterns of the dwarf bamboo species Fargesia nitida.Specifically,we investigated the effects of canopy conditions on the growth and morphological characteristics of F.nitida,and the adaptive responses of F.nitida to different canopy conditions and its ecological senses.The results indicate that forest canopy had a significant effect on the genet density and culm number per clump,while it did not affect the ramet density.Clumps tended to be few and large in gaps and forest edge plots,and small under forest understory plots.The ramets showed an even distribution under the closed canopy,and cluster distribution under gaps and forest edge plots.The forest canopy had a significant effect on both the ramets’biomass and biomass allocation.Favourable light conditions promoted ramet growth and biomass accumulation.Greater amounts of biomass in gaps and forest edge plots were shown by the higher number of culms per clump and the diameter of these culms.Under closed canopy,the bamboos increased their branching angle,leaf biomass allocation,specific leaf area and leaf area ratio to exploit more favourable light conditions in these locations.The spacer length,specific spacer length and spacer branching angles all showed significant differences between gaps and closed canopy conditions.The larger specific spacer length and spacer branching angle were beneficial for bamboo growth,scattering the ramets and exploiting more favourable light conditions.In summary,this study shows that to varying degrees,F.nitida exhibits both a wide ecological amplitude and high degree of morphological plasticity in response to differing forest canopy conditions.Moreover,the changes in plasticity enable the plants to optimize their light usage efficiency to promote growth and increase access to resources available in heterogeneous light environments.