Impact of land-use management on nitrogen transformation in a mountain forest ecosystem in the north of Iran

Soil inorganic N is one of the most important soil quality indexes, which may be influenced by land-use change. The historical conversion of land-use from native vegetation to agriculture resulted in sharp declines in soil N dynamics. This study was conducted to determine the soil inorganic N concentrations and net N mineralization rate in four common types of land-uses in the mountain forest area in the north of Iran, namely arable land, pine plantation, ash plantation, and beech stand. The soil samples were taken from top mineral soil layer (5cm) in each site randomly (n=6) during August- September 2010. Beech stand and ash plantation showed significantly higher total nitrogen compared with arable land and pine plantation, while extractable NH 4 + -N concentration was significantly greater in Beech stand compare to arable soils (p<0.05). No significantly difference was found in Net N mineralization, net nitrification and net ammonification rates among different land-uses. Results showed that net N mineralization and ammonification were occurred just in the soil of Ash plantation during the incubation time. Our findings suggested that conversion of Hyrcanian forests areas to pine plantation and agricultural land can disrupt soil natural activities and affect extremely soil quality.     

Ecosystem carbon and nitrogen storage following farmland afforestation with black locust(Robinia pseudoacacia) on the Loess Plateau,China

Although afforestation of farmlands has been proposed as an effective method of carbon(C) sequestration, there remain uncertainties that deter us from developing a clear picture of C stocks in plantation ecosystems.This study investigated the dynamics of stand structure and plant diversity, and C and nitrogen(N) pools in trees,herbs, litter, and soil(0–100 cm depth) in black locust plantations aged 9, 17, 30, and 37 years, and in newly abandoned farmlands as pre-afforestation sites, on the Loess Plateau, China. Stand density decreased significantly, while tree diameter at breast height and height increased during stand development. The dominant species of the herb layer differed with age. Afforestation resulted in slight increases in tree C and N storage in plantations from 9 to 30 years of age, and then significantly increased from 30 to 37 years. Compared to pre-afforestation, C and N storage in soil decreased to minimum values in stands aged 17 and 9 years, respectively. The soil re-accumulated C and N during stand development, attaining equilibrium levels similar to those in pre-afforestation when stands reached about 30 years of age. Soil C and N storage in 37-year stands were 29 and 16% higher, respectively, than in pre-afforestation levels. However, C and N concentrations in the subsoil(20–40 cm) were still less than the preafforestation levels for stands of all ages(from 9 to 37 years). The relative contribution to the total ecosystem C and N pools increased in trees and decreased in soil during the observed period. Our results indicate that afforestation reduced soil C and N storage during the early stages of stand development. We conclude that the growing phase of an afforested stand over its initial 30 years is important for C and N sequestration by black locust due to the C and N storage that result from recovered soil quality and an increase in tree biomass.     

Ways to improve low-benefit black locust forests in Loess Plateau

This paper presents a general standard for the low-benefit black locust （Robinia pseudoacacia L.） torests m Loess Plateau based on defining the concept of “tri-low forest”, and emphasizes the major factors which result in low-benefit black locust, such as, lack of soil moisture of forest and nutrient, breaching the principle of matching tree species to sites, and high density of forests. Based on different characteristics of low-benefit forests, following the principle of “adjusting measures to local conditions, giving priority to ecological benefits, assisting with economic benefits”, the authors put forward some technical ways to reform low-benefit black locust forests, for example, taking measurements of collecting runoff and storing water, lowering the forest density, introducing mixed forests and transforming species, directive breeding and so on.     

Carbon,nitrogen and phosphorus stoichiometry in Pinus tabulaeformis forest ecosystems in warm temperate Shanxi Province,north China

Although carbon(C), nitrogen(N), and phosphorous(P) stoichiometric ratios are considered good indicators of nutrient excess/limitation and thus of ecosystem health, few reports have discussed the trends and the reciprocal effects of C:N:P stoichiometry in plant–litter–soil systems. The present study analyzed C:N:P ratios in four age groups of Chinese pine, Pinus tabulaeformis Carr., forests in Shanxi Province, China: plantation young forests(AY,20 year-old); plantation middle-aged forests(AM, 21–30 year-old); natural young forests(NY,30 year-old); and natural middle-aged forests(NM,31–50 year-old). The average C:N:P ratios calculated for tree, shrub, and herbaceous leaves, litter, and soil(0–100 cm) were generally higher in NY followed by NM,AM, and AY. C:N and C:P ratios were higher in litter than in leaves and soils, and reached higher values in the litter and leaves of young forests than in middle-aged forests;however, C:N and C:P ratios were higher in soils of middle-aged forests than in young forests. N:P ratios were higher in leaves than in litter and soils regardless of stand age; the consistent N:P14 values found in all forests indicated N limitations. With plant leaves, C:P ratios were highest in trees, followed by herbs and shrubs, indicating a higher efficiency in tree leaf formation. C:N ratios decreased with increasing soil depth, whereas there was no trend for C:P and N:P ratios. C:N:P stoichiometry of forest foliage did not exhibit a consistent variation according to stand age. Research on the relationships between N:P, and P, N nutrient limits and the characteristics of vegetation nutrient adaptation need to be continued.     

Soil respiration in paludified forests of European Russia

Soil respiration studies in paludified forests of the European part of Russia are quite rare in comparison with those of open peat bogs, which make long-term observations in this region highly relevant. In this study,soil CO_2 emissions were measured by the close chamber method in different microlandscapes of paludified forests.For four summer seasons with different environments, soil respiration ranged from 1078 to 248 mg CO_2 m~(-2) h~(-1) in a paludified spruce forest site with coarse woody debris to659–820 mg CO_2 m~(-2) h~(-1) in a paludified boggy pine forest. The most intensive soil respiration was observed during the hot summer of 2013 and the lowest in the hot and humid summer of 2016. Annual total soil CO_2 emissions in paludified forests in 2015–2016 were approximately 2000–3000 g CO_2 m~(-2). During the year, the lowest CO_2 emission values were observed from November to April(14–84 mg CO_2 m~(-2) h-1) and the maximum were in July and August(522–1205 mg CO_2 m-2 h-1). The contributions of CO_2 emissions in the cold November–Aprilperiod were 6–8.5%. The impacts of temperature on soil respiration were higher(r~2= 0.45–0.57) than those of groundwater levels(r~2= 0.17–0.49). Soil respiration in the paludified spruce forest and in the pine bog generally were higher than emissions from ecosystems with similar hydrothermal conditions in the boreal zone.     

Evaluation of regeneration potential of Pinus koraiensis in mixed pine-hardwood forests in the Xiao Xing’an Mountains, China

Large scale harvest of Korean pine(Pinus koraiensis) seeds as a food product in the mixed Korean pine-hardwood forest of northeastern China poses a serious threat to the sustainability and restoration of this endangered regional ecosystem.Seed collection over past decades greatly reduced the seed bank and subsequent seedling and sapling recruitment,and impacting a wide array of granivorous animals that rely on the pine seeds.We surveyed Korean pine seeds,including solid seeds(SS),insect consumed seeds(ICS) and other(animal) consumed(OCS) kernels,of the seed bank(forest floor and the top 10 cm of mineral soil),the seedlings and saplings from 1 m 2 sample plots in five forest types in Liangshui Nature Reserve(LNR) of the southern Xiao Xing’an Mountains in northeastern China to provide accurate information for assessing the Korean pine regeneration potential.The average number of pine seeds in the seed bank were 11.2 seeds/m 2,9.1 seeds/m 2,4.6 seeds/m 2,1.1 seeds/m 2,and 0.2 seeds/m 2 in Korean pine-basswood forest,mixed Korean pine-hardwood forest,mixed conifer-hardwood forest,white birch forests,and oak forests,respectively.In the first three forest types,percentages of SS(potentially viable seeds) were 11.2%,3.5% and 27.8%,respectively.The percentages of ICS(not viable seeds) were consistent at around 35%.The higher but variable percentages of OCS(not viable seeds) indicated high seed predation in these forests.Compared with other studies,we recorded higher percentages of seed damage,probably due to our survey approach and the increased depth of seed bank sampled in our study.Depletion of pine seeds in the seed bank greatly reduced seedling and sapling recruitment.Densities of pine seedlings varied from about 180 trees/ha in the mixed Korean pine-hardwood forest to about 5,400 trees/ha in the mixed conifer-hardwood forests and showed a high degree of spatial variation.Saplings were rare in the mixed Korean pine-hardwood forest,but ranged in the thousands in other forests.Large scale pine seed harvest has seriously threatened the sustainability of the mixed Korean pine-hardwood forest ecosystem.Scaling down the seed harvest or supplemental planting of pine saplings are urgently needed to maintain the health of the existing Korean pine forests and to restore this endangered ecosystem.     

Symbiotic nitrogen fixation in black locust (Robinia pseudoacacia L.) seedlings from four seed sources

We conducted a greenhouse experiment to investigate the role of seed source in growth and symbiotic nitrogen fixation of black locust (Robinia pseudoacacia L). Seeds from different sources were planted in the same environmental conditions and inoculated with a suspension of mixed Rhizobium. We used the modified 15 N isotope dilution method to estimate biological nitrogen fixation of Robinia trees. Different Robinia seed sources differed significantly in terms of tissue dry weight (50.6 80.1 g), total N (1.31-2.16 g) and proportion of nitrogen derived from the atmosphere ( 0-51%). A higher nitrogen fixation rate of Robinia trees was associated with higher dry weight. Moreover, the leaves of Robinia proved to adequately represent the nitrogen fixation capacity of entire plants. Our results confirmed that assessment of seed sources is a useful way to improve the nitrogen fixation capacity and therefore the growth rate of Robinia.     

The inventory of the carbon stocks in sub tropical forests of Pakistan for reporting under Kyoto Protocol

The United Nations Framework Convention on Climate Change (UNFCCC) requires reporting net carbon stock changes and anthropogenic greenhouse gas emissions, including those related to forests. This paper describes the status of carbon stocks in sub tropical forests of Pakistan. There are two major sub types in subtropical forests of Pakistan viz a viz Subtropical Chir Pine and Subtropical broad leaved forests. A network of sample plots was laid out in four selected site. Two sites were selected from sub tropical Chir Pine (Pinus roxburghii) forests and two from Subtropical broadleaved forests. Measurement and data acquisition protocols were developed specifically for the inventory carried out from 2005 to 2010. In total 261 plots (each of 1ha.) were established. Estimation of diameter, basal area, height, volume and biomass was carried out to estimate carbon stocks in each of the four carbon pools of above-and below-ground live biomass. Soil carbon stocks were also determined by doing soil sampling. In mature (~100 years old) pine forest stand at Ghoragali and Lehterar sites, a mean basal area of 30.38 and 26.11 m2·ha-1 represented mean volume of 243 and 197 m3·ha-1,respectively. The average biomass (t·ha-1) was 237 in Ghoragali site and 186 t·ha-1 in Lehterar site, which is equal to 128 and 100 t C ha-1 including soil C. However, on average basis both the forests have 114.5± 2.26 t·ha-1 of carbon stock which comprises of 92% in tree biomass and only 8% inthe top soils. In mixed broadleaved evergreen forests a mean basal area(m2·ha-1) was 3.06 at Kherimurat with stem volume of 12.86 and 2.65 at Sohawa with stem volume of 11.40 m3·ha-1. The average upper and understorey biomass (t·ha-1) was 50.93 in Kherimurat site and 40.43 t·ha-1 in Sohawa site, which is equal to 31.18 and 24.36 t C ha-1 including soil Cstocks. This study provides a protocol and valuable baseline data for monitoring biomass and carbon stocks in Pakistan’s managed and unmanaged sub-tropical forests.     

Patterns of biomass,carbon,and nitrogen storage distribution dynamics after the invasion of pine forests by Bursaphelenchus xylophilus (Nematoda: Aphelenchoididae) in the three Gorges Reservoir Region

Masson pine stands infected by Pine wilt disease(PWD) in the Three Gorges Reservoir Region of central China were surveyed to quantify the immediate responses and subsequent trajectories of biomass,carbon(C),and nitrogen(N) in stand-level major ecosystem compartments.The biomasses of above-and belowground tree components,as well as of the understory,forest floor,and mineral soil(0–40 cm),were determined within each stand.C and N storage were also estimated for each ecosystem compartment.Overstory biomass decreased steadily with the extent of PWD infection.Understory biomass ranged from1.97 to 4.16 Mg ha~(-1),and the observed value for forest floor biomass was 12.89–22.59 Mg ha~(-1).The highest mean C and N concentrations were found in the stem bark and needles of Masson pine,respectively,while the lowest were found in the semi-to fully decomposed layer of the forest floor and stem wood of Masson pine,respectively.The C and N storage of aboveground trees,tree roots,and the aboveground ecosystem decreased with the extent ofPWD infection.However,the C and N contents of the understory,forest floor,and total mineral soil initially declined after PWD infection before recovering over the following several years.Those result concluded that the biomass,C,and N storage of different forest ecosystem compartments have experienced certain variations following the PWD epidemic.This is vital to understand the shifts in stand-level C and N allocation in PWD-damaged forest stands,as well as for predicting the responses of regional and global C and N cycling.     

Forecasting the development of boreal paludified forests in response to climate change: a case study using Ontario ecosite classification

Background:Successional paludification,a dynamic process that leads to the formation of peatlands,is influenced by climatic factors and site features such as surficial deposits and soil texture.In boreal regions,projected climate change and corresponding modifications in natural fire regimes are expected to influence the paludification process and forest development.The objective of this study was to forecast the development of boreal paludified forests in northeastern North America in relation to climate change and modifications in the natural fire regime for the period 2011–2100.Methods:A paludification index was built using static(e.g.surficial deposits and soil texture)and dynamic(e.g.moisture regime and soil organic layer thickness)stand scale factors available from forest maps.The index considered the effects of three temperature increase scenarios(i.e.+1°C,+3°C and+6°C)and progressively decreasing fire cycle(from 300 years for 2011–2041,to 200 years for 2071–2100)on peat accumulation rate and soil organic layer(SOL)thickness at the stand level,and paludification at the landscape level.Results:Our index show that in the context where in the absence of fire the landscape continues to paludify,the negative effect of climate change on peat accumulation resulted in little modification to SOL thickness at the stand level,and no change in the paludification level of the study area between 2011 and 2100.However,including decreasing fire cycle to the index resulted in declines in paludified area.Overall,the index predicts a slight to moderate decrease in the area covered by paludified forests in 2100,with slower rates of paludification.Conclusions:Slower paludification rates imply greater forest productivity and a greater potential for forest harvest,but also a gradual loss of open paludified stands,which could impact the carbon balance in paludified landscapes.Nonetheless,as the thick Sphagnum layer typical of paludified forests may protect soil organic layer from drought and deep burns,a significant proportion of the territory has high potential to remain a carbon sink.     

刺槐尺蠖防治指标的研究

经过对刺槐的蓄叶量、叶面积、刺槐尺蠖食叶量、人工模拟摘叶对刺槐生长量影响等因子的调查分析，得出胸径D与刺槐蓄叶量M之间的关系式为M=135265．73 ＋ 13949．41D（相关系数r=0．976），刺槐叶面积与鲜重（长宽平均值）的关系：S=0．096W - 0．086（r=0．986），S=1．99L - 0．68（r=0．988），刺槐尺蠖幼虫期平均每头损叶量为295．45cm^2，根据CT=M＊H／Q（1-R）关系式，计算出不同径阶刺槐树的刺槐尺蠖的防治指标。     

日本黑松和赤松精英树半同胞家系生长及遗传参数分析

通过对泰山竹林寺景区引种27年生的日本黑松和赤松精英树半同胞家系生长特性和遗传参数的研究发现：（1）黑松生长量略优于赤松,它们的平均胸径分别为21．83cm和20．84cm,平均材积分别为0．264m^3和0．262m^3。从遗传特性上来看,黑松和赤松的胸径的家系h^2分别为0．7668和0．4404。（2）从家系间比较可知：黑松大岛6^#、黑松柳井3^#、当地黑松、黑松柳井2^#生长指标居于前4位,材积分别为0．4725m^3、0．3526m^3、0．3179m^3和0．3144m^3。赤松都浓3^#、赤松都浓2^#、赤松大岛1^#居于前列,材积分别为0．429m^3、0．343m^3和0．365m^3。     

Identification of Cylindrocladium sp. causing damping-off disease of Japanese black pine (Pinus thunbergii) and factors affecting the disease severity in a black locust (Robinia pseudoacacia)-dominated area

The regeneration of Japanese black pine (Pinus thunbergii) seedlings is inhibited in a black locust (Robinia pseudoacacia)-dominated area. We examined the presence of pathogenic fungi in Japanese black pine seedlings in the area in order to determine the effect of pathogenic fungi on the inhibition of regeneration. When Japanese black pine seedlings were planted in the soil obtained from a black locust-dominated area, all of the seedlings died under low-intensity light conditions, whereas 84% of the seedlings survived in the soil obtained from a Japanese black pine-dominated area under the same light conditions. One fungus was isolated from 48.7% of the dead pine seedlings and was identified as Cylindrocladium pacificum Kang, Crous & Schoch, based on the morphological characteristics, growth, and DNA analysis. This fungus was also isolated from 50% of the dead pine seedlings in 2005 and 66.7% of the seedlings in 2006—both were planted in a black locust-dominated area. The virulence of this fungus increased under high-nitrogen and/or low-intensity light conditions. These results reveal the possibility that the soil eutrophication and shading by the black locust are conducive to a severe damping-off disease and threaten the survival and regeneration of Japanese black pine seedlings.     

Effects of black locust on productivity and nitrogen nutrition of intercropped barley

Effects of black locust (Robinia pseudoacacia L.) on productivity and N nutrition of barley (Hordeum vulgare L.) were evaluated under various management regimes (2 soil types, 3 levels of N fertilizer, and 3 cropping systems — barley alone, and barley intercropped with trees pruned or unpruned).Intercropping did not affect productivity and N nutrition of barley in 1988 when trees were small. However, there was a significant yield decline in 1989 as the trees grew bigger. On average, productivity of the sole crop was 8% higher in both soil types. Pruning and mulching moderated the yield reduction compared with the unpruned treatment. Competition for soil moisture was considered a major constraint. Nonetheless, the overall productivity (barley+black locust) from the intercropped treatments was 53% higher than sole cropping.In 1989 and 1990, intercropped barley had significantly higher grain and straw N concentrations (%). In 1989, for example, grain N content was 11% higher than in the sole crop. Removal of trees in 1990 resulted in significant increase in productivity and N content of subsequent barley crop relative to continuous sole cropping. From N nutrition viewpoint, barley from previously intercropped treatments showed superior quality and it had, on average, 23% higher grain N content than the sole crop. This was attributed to N₂-fixation and N return by black locust. It was estimated that black locust contributed about 36 kg N ha^–1 to the system.This study underscores the role black locust is potentially capable of playing in the development of sustainable and low-input agricultural systems in temperate regions. Nonetheless, the study also illustrates the importance of the below and above-ground interactions that occur in intercropped systems and the need for further research in this area.     

胡枝子屑黑木耳培养料的配方筛选

在研发利用胡枝子屑为替代原料栽培黑木耳生产技术中,通过对不同替代料和不同配方的黑木耳菌丝生长速度、原基形成时间、采收时间、平均产量、生物学效率及子实体形态6个方面对比试验分析,筛选出了胡枝子屑栽培黑木耳最佳培养料配方.结果表明:胡枝子屑栽培黑木耳最佳培养料配方为胡枝子屑86.5％+麦麸10％+豆饼2％+石膏1％+石灰0.5％;胡枝子屑为原料配方生产的黑木耳产量显著大于杞柳配方(P＜0.05),与杞柳屑配方相比,产量增加12.50％ ～ 13.75％.     

Establishment of a transgenic system in fast-growing black locust (Robinia pseudoacacia L.)

The AhDREB1 gene, cloned from Atriplex hortensis L., was transferred into black locust (Robinia pseudoacacia L.) by an Agrobacterium-mediated transformation. The results suggest that stems of black locust sub-cultured in vitro for 20 d are suitable for genetic transformation. The optimum concentrations of kanamycin and cefotaxime were 30 and 150 mg.L-1, respectively. Impor-tant factors affecting the transformation efficiency were studied by means of a L9(34) orthogonal design. An effective system for ge-netic transformation in black locust was developed as follows: the stems were pre-cultured for 2 d, immersed in the Agrobacterium solution (OD6oo = 0.7) with 10 mg'L-1 acetosyringone for 21 min and then co-cultured for 2 d. The selection pressures, changing from low to high, could improve transformation efficiency. The transgenic plants were identified by a PCR method. The PCR results indicated that the AhDREB1 gene had been integrated into the genome of black locust and two lines of the transgenic plants were obtained.     

Characterization of black locust (Robinia pseudoacacia L.) heartwood extractives: identification of resveratrol and piceatannol

Robinia pseudoacacia L. heartwood is characterized by a very high natural durability. However, a significant difference was observed between the mature and juvenile heartwood, the latter presenting less durability against fungi decay, which could be attributed to lower extractive content. In order to elucidate this idea, extractives from mature and juvenile heartwoods of black locust trees were investigated. Results showed that extractive and phenolic contents were higher in mature than in juvenile heartwoods. The identification of phenolic compounds by UPLC–DAD–MS/MS revealed, for the first time, the presence of resveratrol and piceatannol. These two stilbenes as well as the flavonoid dihydrorobinetin were present at the highest level in mature heartwood, and as they are known antifungals, they could account for the great durability of mature heartwood. The stilbenes were detected in significant amounts particularly in mature heartwood where piceatannol reached a level tenfold higher than that reported for Japanese knotweed roots, the primary natural source of these stilbenes, whereas resveratrol level was comparable with reported values. As resveratrol and piceatannol receive increasing demand for nutraceutical, cosmetic and, possibly, pharmaceutical purposes, due to their beneficial health effects, this study underlines the use of R. pseudoacacia as a promising sustainable and economical source of resveratrol and piceatannol.     

Screening of fungicides for the management of wattle rust (Uromycladium acaciae) in Acacia mearnsii plantations,South Africa

South Africa has c. 110 000 ha planted to Acacia mearnsii (black wattle) with 85% of the revenue from the species obtained from the timber and 15% from the bark. From 2012/13 a wattle rust disease has spread throughout the black wattle plantation area in KwaZulu-Natal and from 2015 it was recorded in southern Mpumalanga. The pathogen affects trees of all age classes, causing a reduction in growth, as well as mortality with severe infection. No fungicides are currently registered in South Africa for the control of wattle rust. In October/November 2014, three black wattle trials were initiated in the KwaZulu-Natal Midlands and south-eastern Mpumulanga where fungicides were tested at varying rates for the control of wattle rust. The same trial design was used for all three trials and consisted of a 3 × 3 factorial with one additional control, replicated three times and laid out as a randomised complete block design. The factorial combination consisted of three fungicides (azoxystrobin + difenoconazole; azoxystrobin + cyproconazole; azoxystrobin) applied at three rates (×, 2× and ½ ×). The additional control was not treated with fungicides. Wattle rust had a significant and negative impact on tree growth, irrespective of site and/or previous infection. All fungicides tested, and at all rates applied, proved effective for the control of wattle rust. The optimum rate selected, timing and frequency of application will be based on a combination of prevention of resistance as well as optimisation of growth. For the most effective control of wattle rust, fungicides should be applied as a preventative, rather than corrective, measure. However, in cases of severe infestation, a corrective application could also be used to aid the management of wattle rust.     

Improving Acacia auriculiformis seedlings using microbial inoculant （Beneficial Microorganisms）

A microbial inoculant, known as effective microorganisms(EM), was applied to determine its efficacy on seed germination and seedling growth in the nursery of Acacia auriculiformis A Cunn. ex Benth. The seedlings were grown in a mixture of sandy soil and cow dung(3:1) and kept in polybags; EM was poured at different concentrations(0.1%, 0.5%, 1%, 2%, 5% and 10%). Seed germination rate and growth parameters of seedlings – shoot and root lengths, fresh and dry weights of shoots and roots, vigor, volume, and quality indices and sturdiness – were measured. The nodulation status influenced by EM was also observed, along with the measurement of pigment contents in leaves. The highest germination rate(72%) was observed in 2% EM solution while the lowest(55%) was found in control treatment. The highest shoot and root lengths(30.6 cm and 31.2 cm respectively) were recorded in 2% EM and were significantly(p 0.05) different from control. Both fresh and dry weights of shoots were maximum(8.66 g and 2.99 g respectively) in 2% EM, whereas both fresh and dry weights of root were maximum(2.56 g and 1.23 g respectively) in 5% EM solution. Although the highest vigor index, volume index, and sturdiness(4450, 628 and 67.5 respectively) were found in 2% EM, the highest quality index(0.455) was found in 5% EM solution. The nodule number was higher at a very low(0.5%) concentration of EM but it normally decreased with the increase of concentration. The contents of chlorophyll a, chlorophyll b, and carotenoid were maximum(43.26 mg?L-1, 13.56 mg?L-1and 17.99 mg?L-1 respectively) in 2% EM. Therefore, low concentration of EM(up to 2%)can be recommended for getting maximum seed germination and seedling development of A. auriculiformis in the nursery.     

杨树黑斑病测报模型的研究

在北京郊区黑杨林地内设置固定样地,进行杨树黑斑病Marssonina brunnea病原菌孢子捕捉和病情调查。运用数量化理论I系统分析了病情指数与气象因子之间的关系,结果表明:当平均气温20～28℃、平均相对湿度80%以上、降雨量为60 mm以上时,杨树黑斑病的病情发展迅速。同时建立了杨树黑斑病的数量化测报模型:^yi=-5.236 1x(1,1)+7.388 4x(1,2)-3.045 7x(1,3)-6.231 5x(2,1)-4.540 9x(2,2)+6.261 8x(2,3)+20.496 3x(2,4)+1.146 6x(3,1)+3.613 4x(3,2)+7.025 7x(3,3)+19.680 2x(3,4)。对测报模型检验的预测精度在88.49%～96.43%之间。