New insights into the carotenoid biosynthesis in Torreya grandis kernels

Torreya grandis is a characteristic rare economic tree species in subtropical mountainous areas. The nut has a variety of bioactive compounds, such as polyphenols and vitamins. However, the carotenoids compositions and its regulatory mechanisms underlying carotenoid biosynthesis in kernels remain unknown. Here, the major carotenoids in the kernel were analyzed. The result showed that lutein and β-carotene were the predominant carotenoids in the kernel, while low levels of a-carotenoid and zeaxanthin were detected. Lutein and β-carotene were decreased during the maturation of kernel. Expression analysis by RNA-seq and q RT-PCR indicated that the expressions of TgCYP97A3 and TgLCYB were also reduced during the maturation of kernel. The contents of lutein or β-carotene were obviously increased in tobacco transiently overexpressing TgCYP97A3 or TgLCYB. Moreover, DPPH radical scavenging activity and FRAP were also significantly enhanced. In addition, several MYB and WRKY transcription factors TgMYBS3, TgMYB48 and TgWRKY11 were identified to positively regulate the TgCYP97A3 expression, while TgMYB48, TgWRKY2 and TgWRKY11 could upregulate the TgLCYB expression. The illustration of carotenoids biosynthesis and its molecular mechanism in kernels not only provides a basis for understanding carotenoids biosynthesis in kernels, but also enables the use of molecular biotechnology to develop new health products rich in carotenoids based on T. grandis nuts.

Effect of slope position on leaf and fine root C,N and P stoichiometry and rhizosphere soil properties in Tectona grandis plantations

Little is known about C-N-P stoichiometries and content in teak(Tectona grandis)plantations in South China,which are mostly sited on hilly areas with lateritic soil,and the effect of slope position on the accumulation of these elements in trees and rhizosphere soils.Here we analyzed the C,N,P content and stoichiometry in leaves,fine roots and rhizosphere soils of trees on the upper and lower slopes of a 12-year-old teak plantation.The Kraft classification system of tree status was used to sample dominant,subdominant and mean trees at each slope position.The results showed that the C,N and P contents in leaves were higher than in fine roots and rhizosphere soils.The lowest C/N,C/P and N/P ratios were found in rhizosphere soils,and the C/N and C/P ratios in fine roots were higher than in leaves.Nutrient accumulation in leaves,fine roots and rhizosphere soils were significantly influenced by slope position and tree class with their interaction mainly showing a greater effect on rhizosphere soils.Leaf C content and C/N ratio,fine root C and P contents,and C/N and C/P ratios all increased distinctly with declining slope position.The contents of organic matter(SOM),ammonium(NH4+-N),nitrate-nitrogen(NO3--N)and available potassium(AK)in rhizosphere soils were mainly enriched on upper slopes,but exchange calcium(ECa),available phosphorus(AP),and pH were relatively lower.Variations in the C,N and P stoichiometries in trees were mainly attributed to the differences in rhizosphere soil properties.N and P contents showed significant positive linear relationships between leaf and rhizosphere soil,and C content negative linear correlation among leaves,fine roots and rhizosphere soils.Chemical properties of rhizosphere soils,particularly C/N and NH4+-N,had significant effects on the leaf nutrients in trees on the upper slope.Correspondingly,rhizosphere soil properties mainly influenced fine root nutrients on the lower slope,and soil AK was the major influencing factor.Overall,these results offer new insights for the sustainability and management of teak plantations in hilly areas.

Understory plant diversity and phenolic allelochemicals across a range of Eucalyptus grandis plantation ages

Allelopathy is an important mechanism in Eucalyptus plantations that causes detrimental impacts on understory diversity.Phenolic compounds are the main allelochemicals suppressing understory plants.However,the dynamic changes in phenolic allelochemicals and their relationship with understory diversity with increasing age of Eucalyptus plantations remain largely unclear.In this study,the understory plant diversity was assessed and phenolic compounds identified from leaf litter,roots,and rhizosphere soil samples in a Eucalyptus grandis plantation at two-year intervals for ten years using ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS).The abundance and diversity of under story plant species were lowest in 4-year-old plantations and increased significantly with age.Seven phenolic acids and 10 flavonoids were identified from leaf litter,roots,and rhizosphere soils.Most of the potential phenolic allelochemicals,such as salicylic acid,gallic acid,4-hydroxybenzoic acid,and epicatechin,were more abundant in younger plantations,especially at4 years old.The concentrations of phenolic compounds in the rhizosphere zone were significantly lower than in litter and root samples and did not change significantly with an increase in age.Notably,phenolic compounds contributed more to the variation in the understory plants than soil factors.Hydroxyphenyllactic acid,ellagic acid,quercetin,salicylic acid,and 4-hydroxybenzoic acid were the main phenolic compounds explaining the variation in plant diversity with plantation age.These findings indicate that young E.grandis plantations,especially at four years of age,merit a greater focus because of their lower understory plant diversity and higher allelopathic potential.

Tectona grandis (Teak Tree) Young Leaf Extract as a Histological Stain

Stains are applied to impart contrast to the tissue and identify particular features of interest. However, the use of synthetic dyes as staining reagents has been associated with significant human health challenges and pollution of the ecosystem. These developments have necessitated a shift towards using natural dyes that are eco-friendlier and readily available. We investigated the staining reaction patterns of teak tree leaves (Tectona grandis) dye extracts and explored their suitability as a cytoplasmic stain in micromorphological assessments. Dye extracts were prepared using acetone, methanol, and ethanol as solvents from air-dried (under shade) teak tree young leaves. The dye extracts were applied as a counterstain and evaluated against eosin in formalin-fixed paraffin-embedded (FFPE) bovine tissue sections at varying concentrations and different staining times. Teak tree leaves (Tectona grandis) dye extracts produced relatively varying staining intensities of reddish-brown cytoplasmic coloration when used on bovine tissue at different concentrations and staining times comparable to eosin and with blue-purple hematoxylin nuclear stain. The present study showed that Tectona grandis leaf dye extracts provide an excellent cytoplasmic staining pattern and can be used as an alternative counterstain in routine H&E staining techniques.

Effects of Torreya grandis Root Rot on Seedling Growth and Screening of Its Chemical Control Agents

[Objectives]This study was conducted to prevent the occurrence of root rot disease in Torreya grandis and improve the yield and quality of T.grandis.[Methods]One-year-old and two-year-old seedlings of Torreya grandis‘Xifei’and‘Cufei’were inoculated with the root rot pathogen Fusarium fujikuroi,and the changes in photosynthesis,chlorophyll content,malondialdehyde,and defense enzyme system(superoxide dismutase,peroxidase,and catalase)activity in leaves of T.grandis seedlings were investigated using water as a control.Meanwhile,the control effects of 80%carbendazim wettable powder,64%metalaxyl·mancozeb wettable powder,430 g/L tebuconazole suspension and 30%difenoconazole·cyproconazole EC on root rot in T.grandis were investigated.[Results]After inoculation with the pathogen F.fujikuroi,the net photosynthetic rates and transpiration rates in leaves of T.grandis‘Xifei’and‘Cufei’decreased,and the contents of chlorophyll decreased,while the contents of malondialdehyde increased,and the contents of superoxide dismutase and catalase increased with time.However,peroxidase showed a high activity in T.grandis‘Cufei’only,but a trend of"increasing-decreasing-increasing"in T.grandis‘Xifei’.Among the four chemical control agents,64%metalaxyl·mancozeb wettable powder had the best control effect on root rot of T.grandis caused by the pathogenic fungus F.fujikuroi.[Conclusions]The net photosynthetic rate,transpiration rate,chlorophyll content,malondialdehyde content,superoxide dismutase activity and catalase activity could all be used as screening indicators for T.grandis varieties resistant to root rot.Meanwhile,64%metalaxyl·mancozeb wettable powder could be used as a control agent for root rot on T.grandis.

巨桉(Eucalyptus grandis)人工林土壤动物群落对采伐干扰的初期响应

为了解采伐干扰对巨桉（Eucalyptus grandis）人工林土壤动物的影响,于2005～2007年采用手捡法和干湿漏斗法对四川省洪雅县巨桉人工林采伐干扰前和采伐干扰后土壤动物群落进行调查,采伐干扰前四季共获土壤动物4775头,分属4门11纲27目,采伐干扰后获土壤动物4640头,分属4门10纲23目。采伐干扰后秋季（10月）、冬季（1月）和春季（4月）土壤动物个体数较采伐干扰前分别上升224头、368头和443头,而夏季（7月）下降了1170头。采伐干扰前巨桉人工林土壤动物个体数与类群数季节变化趋势基本一致,而采伐干扰后土壤动物类群数变化受土壤动物个体数变化的影响较小。与采伐干扰前相比,采伐干扰后枯落物层各季节土壤动物密度均低于采伐前,0～5 cm土层土壤动物密度与干扰前呈相反的变化趋势,其波动较5～10 cm和10～15 cm土层大。采伐干扰后土壤动物类群数四季共减少4个,采伐干扰前后土壤动物优势类群类群数波动小,采伐后常见类群类群数上升（除冬季外）,稀有类群对采伐干扰较敏感,其类群数下降幅度较大。采伐干扰前后同功能种团均以杂食性和腐食性土壤动物为主,两者百分比之和均在89%以上。密度-类群指数（DG）和多样性指数（H′）的变化趋势相似,采伐干扰前后的变化趋势相反,表明采伐干扰对巨桉人工林土壤动物季节变化有较大影响。

化橘红挥发油对罗汉果斑枯病菌的抑制作用及机理

采用平板抑菌法结合盆栽防治试验测定化橘红(Citri grandis Exocarpium)挥发油对罗汉果(Siraitia grosvenorii)斑枯病菌(Stagonosporopsis cucurbitacearum)的抑制活性。通过显微观察病原菌菌丝体的形态及测定挥发油处理病原菌菌丝体后处理液的电导率及可溶性蛋白质含量变化情况,探究化橘红挥发油的抑菌机理。平板抑菌结果表明,化橘红挥发油稀释≤1 000倍对罗汉果斑枯病病原菌菌丝生长的抑制率均达100.0%,显著高于80%多菌灵可湿性粉剂稀释1 000倍的抑制率(88.7%)。盆栽试验结果表明,化橘红挥发油稀释1 000倍,45%戊唑·咪鲜胺乳油和10%苯醚甲环唑乳油对罗汉果斑枯病病斑扩展的抑制率均在80.0%以上,且均显著高于80%多菌灵可湿性粉剂的抑制率(70.68%)。显微镜下观察发现,经化橘红挥发油处理7 d的病原菌菌丝呈念珠状膨大并有断裂现象。菌丝体与化橘红挥发油共培养结果表明,混合液的电导率及可溶性蛋白质含量均随着化橘红挥发油处理浓度的加大、互作时间的延长而提高;浓度为2.0 g/L的化橘红挥发油与病原菌菌丝共培养48 h,培养液的电导率为279.208μS/cm,为各处理最大值;挥发油终质量分数0.2%、作用60 h后,培养液中的可溶性蛋白质含量达90.6μg/mL,为各处理的最大值。

A Study of the Distribution and Accumulation of Major Nutrient Elements in Different Densities of Eucalyptus grandis

This study was conducted to investigate the distribution and accumulation of major elements of 5-year-old Eucalyptus grandis forests with the densities of 556 trees/hm2 and 1 667 trees/hm2. The results showed that： （1） The distribution of ma- jor nutrient element contents in various organs of the E. grandis with the 2 densi- ties was nearly the same, and the ranked order was leaf〉tree trunk〉branch or branchlet〉fruit〉bark. （2） From the distribution of nutrient elements and organic mat- ter in the trunk, P, K, Mg and Ca contents presented basically a trend of increasing with the trunk height increasing. And the organic matter content increased with the trunk height increasing in the low density stand, while the result was opposite in the high density stand. Furthermore, N content increased with the trunk height increas- ing in the low density stand, but the content in the high density stand exhibited a trend of decreasing at first, increasing then and increasing at the last. （3） From the distribution of biomass, the ranked order was tree trunk〉bark or branch〉branchlet〉 leaf〉fruit. And （4） The accumulated amounts of major nutrient elements in various organs under the 2 stand densities was nearly same. Ca content was the highest in the 2 kinds of plantations, followed by N, K, Mg and P contents. Ca content was 601.78 kg/hm2 in the low density stand and 1 204. 43 kg/hm2 in the high density stand.

琯溪蜜柚果肉中类胡萝卜素组分的特征解析

琯溪蜜柚(Citrus grandis cv‘Guanximiyou’)因其汁多味甜、色泽丰富等特点,广受消费者欢迎。琯溪蜜柚果肉色素主要为类胡萝卜素,其组分和含量直接影响果实品质。研究蜜柚果肉类胡萝卜素组分特征及其在不同养分管理下的差异,可为通过养分管理提高果实品质提供科学依据。本研究首先利用液相色谱串联质谱(LC-MS/MS),分析果实汁胞中类胡萝卜素的组分;通过施化肥(CF)和有机肥(OF)处理,比较分析不同养分管理对类胡萝卜素的影响。结果表明,蜜柚汁胞共含23种类胡萝卜素,其中5种属于胡萝卜素、18种属于胡萝卜醇。汁胞中类胡萝卜素以胡萝卜素为主,质量分数为(346.27±69.39)μg/g,占比为98.98%。胡萝卜素中,以番茄红素为主,质量分数为(332.27±75.05)μg/g,占类胡萝卜素比例为95.97%。此外,养分管理显著影响汁胞类胡萝卜素的质量分数。与CF相比,OF处理番茄红素和E/Z-八氢番茄红素的质量分数分别增加了8.40%和16.48%,说明通过养分管理能够调控蜜柚果肉色素,为进一步调控果实品质提供参考依据。

Distribution and Accumulation of Nutrient Elements in Organic Tissue of Eucalyptus grandis Saplings

The biomass, macroelements （N, P, K, Ca, Mg） and microelements （Fe, Zn） contents were detected in organs of 1a-3a Eucalyptus grandis saplings, as well as their accumulated amount. Results showed that contents of nutrient elements varied greatly in different organs. Total contents of macroelements N, P, K, Ca and Mg in1a-3a E. grandis were distributed in the order of stem phloem, leaves 〉 branch- es, roots 〉 stem xylem. Accumulated amount of macroelements in 1a-3a E. grandis were in the order of leaves 〉 branches 〉 stem phloem 〉 roots or stem xylem 〉 stem xylem or roots. Accumulated amount law of nutrient elements was not affected by the plant age. Microelements Fe and Zn were mainly concentrated in the leaves and roots. The accumulation of macroelements was in the order of Ca 〉 N 〉 K 〉 Mg 〉 P; and the microelements was in the order of Fe 〉 Zn. Accumulated amounts of microelements in 1a-3a E. grandis were 12.45 136.19 and 420.23 g per plants, respectively. Among the annual net accumulated amount of nutrient ele- ments per plant in 1a-3a E. grandis, Ca element was the maximum, N and K ele- ments took the second and third places. Mg element was relatively small and P el- ement was the minimum.

Leaf Area Calculation Model of E.urophylla and E.grandis×E.urophylla

[Objective] The aim was to build an optimal leaf area measurement model of E. urophylla and E. grandis×E.urophylla. [Method] The correlation between leaf area and leaf＇s eigenvalue of E. urophylla and E. grandis×E.urophylla were studied. [Result] There was certain difference in leaf characteristics values between the 2 species. The leaf areas of E. urophylla and E. grandis×E.urophylla both had significant correlation with leaf length,leaf width,leaf perimeter,leaf length × leaf width,the ratio of leaf length to leaf width,shape factor,etc.,so the factors could be constructed into a regression model with leaf area. Among them,the best 2 models for leaf area calculation which were built by leaf length × leaf width of E. urophylla and E. grandis×E.urophylla both had relatively high accuracy and practical applications. [Conclusion] The research provides a simple and effective leaf area measurement method for studies on the 2 tree species.

Boll weevils in dry bolls:is there a performance disadvantage?

Background Anthonomus grandis grandis is the main cotton pest in the Americas,with the potential to become a pest in other continents.The insect uses the plant's reproductive organs for feeding,oviposition,and survival strategies in the off-season,sheltering in dry bolls.This study aimed to know the reproductive potential,feeding,longevity,and morphometric characteristics of boll weevils from dry bolls,squares,and traps.Adults were obtained from infested squares,dry bolls,and traps installed in cotton fields and the Caatinga area.Thirty weevil pairs were maintained in the laboratory to assess the oviposition,feeding holes,longevity,and morphometric measurements of the parental and F_(1) generations.Results In the parental generation,boll weevils from traps(the Caatinga area and cotton cultivation)showed greater reproductive potential.Boll weevils from squares and the Caatinga area showed greater feeding activity compared with those from cotton cultivation.Greater rostrum length,thorax+abdomen length,and abdomen width were observed in boll weevils from cotton cultivation and dry bolls.The origin of boll weevils parental generation did not affect progeny emergence time.The F_(1) generation of boll weevils showed significant differences in average longevity depending on the origin of different microhabitats.Furthermore,differences in rostrum lengths were observed,with the boll weevils coming from traps installed in cotton cultivation,the Caatinga area,and dry bolls being the largest.Regarding thorax+abdomen length and abdomen width,the highest values were observed in those from the Caatinga area and cotton cultivation.Conclusion It was proven that dry bolls did not affect the reproductive,feeding,and longevity performance of boll weevils,enabling better insect fitness(reproduction and size)in relation to those coming from squares.The use of dry bolls as off-season shelter is an important survival strategy for the boll weevil.

柚(Citrus grandis Osbeck cv.)MADS box基因的表达分析

以De novo转录组学方法分析柚(Citrus grandis Osbeck cv.)MADS box基因家族的基因.以特早熟龙柚(变异型)和琯溪蜜柚(参照型)嫩果(不超过5天)和新叶为材料,经过RNA提取、反转录、测序、组装得到Unigene序列.Unigene序列在Nr、Swiss-Prot、KEGG和COG四大数据库中进行比对,获得MADS box转录因子家族基因注释结果.采用数字基因表达标签(digital gene expression tag,DGE)技术,对样本中基因转录丰度以RPKM值表示,比较处理组和对照组的RPKM值,以倍性变化≥2确定差异表达基因(differentially expressed genes,DEGs).从特早熟龙柚和琯溪蜜柚嫩果和叶片中,总共注释到28个MADS box基因家族基因.在龙柚嫩果(FE)和蜜柚嫩果(FL)中表达的有25个,其中有6个属于差异表达基因.在龙柚叶片(LE)和蜜柚叶片(LL)中表达的有27个,其中有7个属于差异表达基因.注释到的28个MADS box基因家族基因在克莱门特柚(Citrus clementina)和中国甜橙(Citrus sinensis)报道过的分别有18个和20个,其中有5个基因既在中国甜橙和克莱门特柚都没有报道过,也没有发现在其它Citrus物种报道过.

Evaluation of Generalized Error Function via Fast-Converging Power Series

A generalized form of the error function, Gp(x)=pΓ(1/p)∫0xe−tpdt, which is directly associated with the gamma function, is evaluated for arbitrary real values of p>1and 0x≤+∞by employing a fast-converging power series expansion developed in resolving the so-called Grandi’s paradox. Comparisons with accurate tabulated values for well-known cases such as the error function are presented using the expansions truncated at various orders.

Purification and structural analysis of the toxin AP-Ⅰ from the pathogen of Bambusa pervariabilis × Dendrocalamopsis grandis blight

Bambusa pervariabilis Dendrocalamopsis grandis blight is caused by a toxin from the fungus Arthrinium phaeospermum （corda） M. B. Ellis. We used shaking culture in a modified Fries culture medium and methanol extraction to isolate the toxin. The optimal developing solvent mixture （methanol： ethyl acetate： H20 at 7：1.5：3） was selected using thin layer chromatography and used as the eluent for toxin purification by silica gel column chromatography. Two toxic fractions were identi- fied in the bioassay. A flaxen oil substance, AP-I, showed higher toxicity than a toxic white powder, AP-II. The more toxic AP-I was determined to be dibutyl phthalate （C16H2204, molecular weight of 278） by mass spectrome- try, nuclear magnetic resonance, and infrared spectropho- tometry. Dibutyl phthalate might contribute to the pathogenesis of bamboo blight.

Grandis电控节气门系统的原理和检修

详细介绍三菱Grandis线控电子节气门系统的组成、构造和工作原理,以及检修和自适应方法。并用维修实例加以说明。

Antidiabetic,antihyperlipidemic and antioxidant potential of methanol extract of Tectona grandis flowers in streptozotocin induced diabetic rats

Objective:To investigate antidiabetic,antihyperlipidemic and antioxidant activity of methanol extract of Tectona grandis(T.grandis) flowers(METGF) in streplozotocin(STZ) induced diabetic rats to supports its traditional use.Methods:Acute toxicity study of METGF was carried out in rat to determine its dose for the antidiabetic study.Oral glucose tolerance test(OGTT) was performed to evaluate METGF effect on elevated blood glucose level.Diabetes was induced in rats by administration of STZ(60 mg/kg,ip.) and it was confirmed 72 h after induction.METGF was orally given to the diabetic rats up to 28 days and blood glucose level were estimated each week.On 28 day of the experiment,diabetic rats were sacrificed after the blood collection for the biochemical parameters analysis and liver,kidney was collected to determine antioxidants levels.Results: In acute toxicity,METGF did not show toxicity and death up to a dose 2 000 mg/kg in rats. Administration of METGF 100 and 200 mg/kg significantly(P【0.001) reduced blood glucose levels in OGTT and STZ-induced diabetic rats.Both doses of METGF treatment significantly(P【0.001, P【0.01 and P【0.05) increased body weight,serum insulin,haemoglobin(Hb) and total protein levels in diabetic rats.Also,MEGTF treatment reduced elevated glycosylated haemoglobin(HbA1c) and other biochemical parameters levels significantly(P【0.001) in diabetic rats.Altered lipid profiles and antioxidants levels were reversed to near normal in diabetic rats treated with METGF. Conclusions:These results concluded that METGF possesses antidiabetic,antihyperglycemic and antioxidant activity which supports its traditional use.

Effects of Rest Grazing on Organic Carbon Storage in Stipa grandis Steppe in Inner Mongolia, China

This study was aimed to evaluate the potential effects of rest grazing on organic carbon storage in Stipa grandis steppe of Inner Mongolia, China. Using potassium dichromate heating method, we analyzed the organic carbon storage of plant and soil in Stipa grand＆ steppe after rest grazing for 3, 6, and 9 yr. The results indicated that as the rest grazing ages prolonged, the biomass of aboveground parts, litter and belowground plant parts （roots） of the plant communities all increased, meanwhile the C content of the biomass increased with the rest grazing ages prolonging. For RG0, RG3a, RG6a, and RG9a, C storage in aboveground vegetation were 60.7, 76.9, 82.8 and 122.2 g C m2, respectively; C storage of litter were 5.1, 5.8, 20.4 and 25.5 g C m^-2, respectively; C storage of belowground roots （0-100 cm） were 475.2, 663.0, 1 115.0 and 1 867.3 g C m^-2, respectively; C storage in 0-100 cm soil were 13.97, 15.76, 18.60 and 32.41 kg C m^-2, respectively. As the rest grazing ages prolonged, the organic C storage in plant communities and soil increased. The C storage ofbelowground roots and soil organic C was mainly concentrated in 0-40 cm soil body. The increased soil organic C for RG3a accounted for 89.8% of the increased carbon in vegetation-soil system, 87.2% for RG6a, and 92.6% for RG9a. From the perspective of C sequestration cost, total cost for RG3a, RG6,, and RG9a were 2 903.4, 5 806.8 and 8 710.2 CNY haq, respectively. The cost reduced with the extension of rest grazing ages, 0.15 CNY kg^-1 C for RG3a, 0.11 CNY kg-~ C for RG6a and 0.04 CNY kg℃ for RG9a. From the growth characteristics of grassland plants, the spring was one of the two avoided grazing periods, timely rest grazing could effectively restore and update grassland vegetation, and was beneficial to the sustainable use of grassland. Organic C storage for RG9a was the highest, while the cost of C sequestration was the lowest. Therefore, spring rest grazing should be encouraged because it was proved to be a very efficient grassland use pattern.

Eucalyptus grandis plantations:effects of management on soil carbon,nutrient contents and yields

The expansion of fast-growing tree plantations is a worldwide process,with consequences on soil fertility and soil carbon storage.Disparate results were found on the effects of afforestation with Eucalyptus on soil carbon and other nutrient contents.These discrepancies are usually caused by differences in climate,land use history,soil texture as well as by management related factors such as plantation age,number of rotations,method of establishment(plantation or coppice),harvest residue management and soil preparation.We studied the effect of plantation age,number of rotations,and method of establishment on soils and plant nutrient concentrations in Eucalyptus grandis plantations in NE Argentina on different textured soils.We also determined if yields changed with nutrient variations in soils,and compared soils under plantations to soils under grasslands they replaced.Thirty-one E.grandis stands of different ages,number of rotations and method of establishment were evaluated as well as eight grassland sites.Levels of carbon,nitrogen,phosphorus,potassium,calcium and magnesium were determined for soils and plants.Soil carbon and nitrogen decreased over the number of rotations and were more pronounced in soils with 50-60%sand than soils with>75%sand.Coppice stands showed higher soil carbon and nitrogen levels than plantations,suggesting a negative effect of site preparation before planting on soil nutrient conservation,especially in fine-textured soils.Foliar nutrient concentrations did not follow the trends observed for soil nutrients nor did they reflect nutrient limitations.There was no evidence of decreased yields over successive rotations.Soil carbon and nitrogen contents decrease when grasslands are replaced by E.grandis plantations,and therefore a yield limitation may occur in a medium to long-term frame,especially in stands re-established for short-rotation management.Harvest residue management and site preparation must be specifically designed for improving soil nutrient management.

Emission characteristics of carbon dioxide in the semiarid Stipa grandis steppe in Inner Mongolia, China

Using the static opaque chamber method, the soil respiration rates （SR） were measured through the continuous experiments in situ in semiarid Stipa grandis steppe in Xilin River Basin of Inner Mongolia, China from June 2001 to June 2003, in parallel, the difference between the SR and the ecosystem respiration rates （TER） were compared. The results indicated that the seasonal variations of the SR and TER were obvious with higher emissions in growing season and a relatively low efflux level in non-growing season, furthermore, the negative effluxes were found in the observation site in winter; the annual CO2 efflux of total ecosystem ranged from 160.5 gC/（m^2·a） to 162.8 gC/（m^2·a） and that of soil ranged from 118.7 gC/（m^2·a） to 152.3 gC/（m^2·a）. The annual SR accounted for about 74.0% to 93.5% of the annual TER, but the results of Analysis of Variance （ANOVA） indicated that the difference between the annual average TER and SR did not reach the significance level of 0.05. The TER was under similar environmental controls as SR, in growing seasons of drought years, the variations of soil moisture at 0-10 cm and 10-20 cm depth could account for 79,1% 95.6% of the changes of the SR and TER, but in non-growing season, more than 75% of the variations of the SR and TER could be explained by the changes of the ground temperature of soil surface layers.