Effects of urbanization and forest type on species composition and diversity,forest characteristics,biomass carbon sink,and their associations in Changchun,Northeast China:implications for urban carbon stock improvement

Differences in forest attributes and carbon sequestration of each organ and layer between broadleaved and conifer forests of central and outer urban areas are not well-defined,hindering the precise management of urban forests and improvement of function.To clarify the effect of two forest types with different urbanization intensities,we determined differences in vegetation composition and diversity,structural traits,and carbon stocks of 152 plots(20 m×20 m)in urban park forests in Changchun,which had the largest green quantity and carbon density effectiveness.We found that 1.1-fold thicker and healthier trees,and 1.6-to 2.0-fold higher,healthier,denser,and more various shrubs but with sparser trees and herbs occurred in the central urban forests(p<0.05)than in the outer forests.The conifer forests exhibited 30–70%obviously higher tree aboveground carbon sequestration(including stem and leaf)and 20%bigger trees,especially in the outer forests(p<0.05).In contrast,1.1-to 1.5-fold higher branch stocks,healthier and more diverse trees were found in broadleaved forests of both the inner and outer forests(p<0.05).Plant size and dominant species had similarly important roles in carbon stock improvement,especially big-sized woody plants and Pinus tabuliformis.In addition,a higher number of deciduous or needle species positively affected the broadleaved forest of the central urban area and conifer forest of the outer urban area,respectively.These findings can be used to guide precise management and accelerate the improvement of urban carbon function in Northeast China in the future.

Adaptations of the floral characteristics and biomass allocation patterns of Gentiana hexaphylla to the altitudinal gradient of the eastern Qinghai-Tibet Plateau

This study addressed the floral component traits and biomass allocation patterns of Gentiana hexaphylla as well as the relationships of these parameters along an elevation gradient(approximately 3700 m, 3800 m, 3900 m, and 4000 m) on the eastern Qinghai-Tibet Plateau. The plant height, floral characteristics, and biomass allocation of G. hexaphylla were measured at different altitudes after field sampling, sorting, and drying. Plant height was significantly greater at 3700 m than that at other elevations. Flower length was significantly greater at 4000 m than that at other elevations, whereas the flower length at low elevations showed no significant differences. Corolla diameter increased with altitude, although the difference was not significant between 3800 m and 3900 m. Variations in biomass accumulation, including the aboveground, photosynthetic organ, flower and belowground biomasses, showed non-linear responses to changes in altitude. The aboveground and photosynthetic organ biomasses reached their lowest values at 4000 m, whereas the belowground and flower biomassreached minimum values at 3700 m. The sexual reproductive allocation of G. hexaphylla also increased with altitude, with a maximum observed at 4000 m. These results suggest that external environmental factors and altitudinal gradients as well as the biomass accumulation and allocation of G. hexaphylla play crucial roles in plant traits and significantly affect the ability of this species to adapt to harsh environments. The decreased number of flowers observed at higher altitudes may indicate a compensatory response for the lack of pollinators at high elevations, which is also suggested by the deformed flower shapes at high altitudes. In addition, the individual plant biomass(i.e., plant size) had significantly effect on flower length and corolla diameter. Based on the organ biomass results, the optimal altitude for G. hexaphylla in the eastern Qinghai-Tibet Plateau is 3800 m, where the plant exhibits minimum propagule biomass and asexual reproductive allocation.

Effects of drip irrigation modes on growth and physiological characteristics of Arabica coffee under different N levels

The objective of this study was to obtain the water-saving and efficient production mode of Arabica coffee. The effects of three drip irrigation modes,conventional drip irrigation( CDI),alternate drip irrigation( ADI) and fixed drip irrigation( FDI) on growth,photosynthetic characteristics,biomass accumulation and irrigation water use efficiency of Arabica coffee were investigated under three nitrogen levels,high nitrogen( NH),middle nitrogen( NM) and low nitrogen( NL). The results show that there was a significant Logistic curve between the plant height,the stem diameter of Arabica coffee and growth days. Compared with CDI,ADI had no significant effects on leaf net photosynthetic rate,stomatal conductance,instantaneous water use efficiency and biomass accumulation above ground of Arabica coffee,while FDI decreased significantly,ADI and FDI increased irrigation water use efficiency by 50. 59% and 32. 85%,respectively. Compared with NH,with the reduction of N application rate,net photosynthetic rate,stomatal conductance,biomass accumulation above ground and irrigation water use efficiency decreased by 6. 81%-12. 30%,13. 70%-22. 69%,9. 61%-16. 67% and 9. 78%-15. 64%,respectively. Compared with CDINH,ADINHdecreased net photosynthesis rate and the stomatal conductance not significantly,other treatments decreased by 9. 16%-19. 22%,14. 49%-32. 91%,and decreased biomass accumulation above ground by 8. 26%-27. 34% except ADINH,and increased irrigation water use efficiency by 16. 46%-60. 95% except CDINMand CDINL. Therefore,alternate drip irrigation under high N level( ADINH) is the best water and nitrogen coupling mode of young Arabica coffee tree for water efficiency.

Characteristics of Plant Communities in Three Kinds of Typical Alpine Meadows in Haibei Region,Qinghai Province

[ Objective ] The paper was to understand the characteristics of plant communities in three kinds of typical alpine meadows in Haibei Region, Qinghai Province. [ Method] The characteristics and diversity of plant communities in typical alpine meadow, including Kobresia humilis, PotentiUafruticose and Kobresia menyuanica, were studied, with Menyuan studfarm in Haibei region of Qinghai Province as an example. [ Result] Results showed that the three kinds of plant communities in alpine meadows presented complex structure; the diversity index had close relationship with the evenness index; there were fewer common species and higher species replacement rate among different alpine meadow communities ; the aboveground biomass of K. humilis alpine meadow was 1.62 and 1.69 times of P. fruticose and K. menyuanica meadows, respectively; the underground biomass mainly distributed in the 0 - 10 cm soil layer, and the vertical spatial distribution structure was ＂T＂ type; the aboveground and underground biomass were negatively correlated. [ Conclusion] The paper will provide basis for protection and further use of different grassland plant communities in Haibei Region, Qinghai Province.

Variation of soil physical-chemical characteristics in salt-affected soil in the Qarhan Salt Lake,Qaidam Basin

Soil salinization has adverse effects on the soil physical-chemical characteristics.However,little is known about the changes in soil salt ion concentrations and other soil physical-chemical characteristics within the Qarhan Salt Lake and at different soil depths in the surrounding areas.Here,we selected five sampling sites(S1,S2,S3,S4,and S5)alongside the Qarhan Salt Lake and in the Xidatan segment of the Kunlun Mountains to investigate the relationship among soil salt ion concentrations,soil physical-chemical characteristics,and environmental variables in April 2019.The results indicated that most sites had strongly saline and very strongly saline conditions.The main salt ions present in the soil were Na^(+),K^(+),and Cl^(-).Soil nutrients and soil microbial biomass(SMB)were significantly affected by the salinity(P<0.05).Moreover,soil salt ions(Na^(+),K^(+),Ca2+,Mg^(2+),Cl^(-),CO_(3)^(2-),SO_(4)^(2-),and HCO_(3)^(-))were positively correlated with electrical conductivity(EC)and soil water content(SWC),but negatively related to altitude and soil depth.Unlike soil salt ions,soil nutrients and SMB were positively correlated with altitude,but negatively related to EC and SWC.Moreover,soil nutrients and SMB were negatively correlated with soil salt ions.In conclusion,soil nutrients and SMB were mainly influenced by salinity,and were related to altitude,soil depth,and SWC in the areas from the Qarhan Salt Lake to the Xidatan segment.These results imply that the soil quality(mainly evaluated by soil physical-chemical characteristics)is mainly influenced by soil salt ions in the areas surrounding the Qarhan Salt Lake.Our results provide an accurate prediction of how the soil salt ions,soil nutrients,and SMB respond to the changes along a salt gradient.The underlying mechanisms controlling the soil salt ion distribution,soil nutrients,and SMB in an extremely arid desert climate playa should be studied in greater detail in the future.

Fine Root Distribution Characteristics of Populus cathayana Plantations at Different Ages in Alpine Sandy Land

[Objectives]The paper was to study the fine root distribution characteristics of Populus cathayana plantations at different ages in alpine sandy land.[Methods]With 5,10,15,20,and 25 years old P.cathayana plantation in the eastern margin of Gonghe Basin,Qinghai Province as the research objects,fine roots were collected by root core drilling method,and the differences of fine root biomass,root length density,average diameter and root tip number at the soil depths of 0-20,20-40,40-60,60-80 and 80-100 cm were analyzed.[Results]The total biomass density of P.cathayana plantation was mainly distributed in the soil layer of 0-60 cm,accounting for 76%of the entire soil layer,and its value increased with the increase in forest age.With the increase in different forest ages,the root length density,average diameter and root tip number of living fine roots in the soil layer of 0-60 cm accounted for 74%-81%of the entire soil layer,and the proportions in the soil layers of 60-80 and 80-100 cm were 9%-11%.The biomass density,root length density,average diameter and root tip number of living and dead fine roots of P.cathayana plantation increased with the increase of forest age.The root length density,average diameter and root tip number of P.cathayana fine roots showed a linear function change trend with the growth of forest age,which could be described by the linear function equation y=ax+b(a>0).The analysis results showed that the root length density,average diameter and root tip number of P.cathayana were significantly correlated with the total biomass density of fine roots,and the root length density and average diameter had an extremely positive correlation with the total biomass density.[Conclusions]In the future,P.cathayana plantation should be properly tended to promote the development of fine roots and maximize its ecological benefits.

降香黄檀中幼林树冠生物量研究

研究降香黄檀(Dalbergia odorifera T.Chen)人工林树冠生物量的分布特征,可以为合理的评估林分生物量和调整树冠结构提供理论依据。本研究以海南东方市林龄为10~12 a的降香黄檀人工林为研究对象,设置2种不同立地条件样地(S_(1)和S_(2)),对4.5 m以上样木截冠处理,采用分层切割法和全量称重法获取树冠层各器官生物量,建立各器官最优生物量拟合方程。结果表明:(1)冠层各器官中生物量大小顺序为裸枝>枝皮>叶片;裸枝、枝皮和冠层总生物量为S_(1)>S_(2),叶片生物量则为S_(1)<S_(2)。(2)随着冠层层次的增高,S_(1)和S_(2)裸枝和枝皮生物量均呈波浪形变化,其中S_(1)表现为先增加再下降,而S_(2)则与之相反;叶片生物量整体呈先上升再下降的趋势,其中S_(1)集中分布在树冠中上层,S_(2)主要分布在下层。S_(1)较S_(2)树冠上层生长竞争更激烈,已出现冠层严重的自然稀疏,叶生物量逐渐由下层转移至中上层。(3)生物量最优拟合模型为幂函数形式,分别为树冠总生物量[y=3.904(D^(2)H)^(1.247)]、冠裸枝[y=1.901(D2H)^(1.28)]、冠枝皮[y=0.734(D2H)^(1.276)]、叶片(y=3.86D^(2.791))。

Nanostructured N-doped carbon materials derived from expandable biomass with superior electrocatalytic performance towards V^(2+)/V^(3+) redox reaction for vanadium redox flow battery

Vanadium redox flow battery(VRFB)is one of the most promising large-scale energy storage systems,which ranges from kilowatt to megawatt.Nevertheless,poor electrochemical activity of electrode for two redox couples still restricts the extensive applications of VRFB.Compared with V^(2+)/V^(3+)redox reaction,V^(2+)/V^(3+)reaction plays a more significant role in voltage loss of VRFB owing to slow heterogeneous electron transfer rate.Herein,N-doped carbon materials derived from scaphium scaphigerum have been developed as negative electrocatalyst by hydrothermal carbonization and high-temperature nitridation treatments.The undoped carbon material hardly has electrocatalytic ability for V^(2+)/V^(3+)reaction.Based on this,N-doped carbon materials with urea as nitrogen source exhibit excellent electrocatalytic properties.And the material nitrided at 850°C(SSC/N-850)exhibits the best performance among those from700 to 1000℃.SSC/N-850 can accelerate the electrode process including V^(2+)/V^(3+)reaction and mass transfer of active ions due to the large reaction place,more active sites,and good hydrophilicity.The effect of catalyst on comprehensive performance of cell was evaluated.SSC/N-850 can improve the charge-discharge performance greatly.Utilization of SSC/N-850 can lessen the electrochemical polarization of cell,further resulting in increased discharge capacity and energy efficiency.Discharge capacity and energy efficiency increase by 81.5%and 9.8%by using SSC/N-850 as negative catalyst at 150 m A cm^(-2),respectively.Our study reveals that the developed biomass-derived carbon materials are the low-cost and efficient negative electrocatalyst for VRFB system.

New Insights in the Ash Melting Behavior and Improvement of Biomass Energy Pellets Using Flour Bond

New insight was obtained in the effect of ash composition on the ash melting behavior of biomass products. It was shown that there is a good correlation between the amounts of calcium （Ca）, silicon （Si） and potassium （K） of the ash and the ash melting temperature （Tmelt） of bio-energy products like wood, agro and sludge pellets （n = 164）. Using PCA and linear regression analyses a good prediction of the Tmelt can be obtained by using an easy to use formula： Ln [Tmelt] = 7.24 - 0.33 × Si - 0. 70 × K ＋ 1.28 × K × Ca （variance accounted for is 72%）. The new formula give much better predictions of the ash Tmelt of wood pellets and other solid bio-energy or biofuel products than previous fits. As expected Ca plays an important positive role. K and Si sink the Tmelt. Other metals play a less dominant role, such as iron （Fe）, aluminium （Al） and magnesium （Mg）. The new insight was put into practice by showing that by adding FlourBond, a pressing aid high in Ca, the Tmelt of wood pellet ash can be increased. It is envisaged that an elevated ash Tmelt reduces the risk of slagging of solid biofuels.

Fractal analysis of canopy architectures of Acacia angustissima, Gliricidia sepium, and Leucaena collinsii for estimation of aboveground biomass in a short rotation forest in eastern Zambia

A study was conducted at Msekera Regional Agricultural Research Station in eastern Zambia to （1） describe canopy branching properties of Acacia angustissima, Gliricidia sepium and Leucaena collinsii in short rotation forests, （2） test the existence of self similarity from repeated iteration of a structural unit in tree canopies, （3） examined intra-specifie relationships between functional branching characteristics, and （4） determine whether allometric equations for relating aboveground tree biomass to fractal properties could accurately predict aboveground biomass. Measurements of basal diameter （Din0） at 10em aboveground and total height （H）, and aboveground biomass of 27 trees were taken, but only nine trees representative of variability of the stand and the three species were processed for functional branching analyses （FBA） of the shoot systems. For each species, fractal properties of three trees, includ- ing fractal dimension （Dfract）, bifurcation ratios （p） and proportionality ratios （q） of branching points were assessed. The slope of the linear re- gression ofp on proximal diameter was not significantly different （P 〈 0.01） from zero and hence the assumption that p is independent of scale, a pre-requisite for use of fraetal branching rules to describe a fraetal tree canopy, was fulfilled at branching orders with link diameters 〉1.5 cm. The proportionality ration q for branching patterns of all tree species was constant at all scales. The proportion of q values 〉0.9 （fq） was 0.8 for all species. Mean fraetal dimension （Df^ct） values （1.5-1.7） for all species showed that branching patterns had an increasing magnitude of intricacy. Since Dfraet values were 〉1.5, branching patterns within species were self similar. Basal diameter （D10）, proximal diameter and Dfraet described most of variations in aboveground biomass, suggesting that allometric equa- tions for relating aboveground tree biomass to fractal properties could accurately predict aboveground biomass. Thus, assessed Acacia, Gliri- cidia and Leucaena trees were fractals and their branching propertiescould be used to describe variability in size and aboveground biomass.

Influence of topography,soil properties and plant community on the biomass of Abies georgei var.smithii seedlings in Southeast Tibet

Biomass of seedlings at different developing stages of growth is important information for studying the response of species to site conditions.The objectives of this study was to explore the distribution characteristics of AGB(above-ground biomass)and BGB(below-ground biomass)of Abies georgei var.smithii seedlings of different ages,and investigate the effects of topography(slope aspect,altitude),plant community characteristics(crown density,species diversity,etc.),and soil properties(soil physical and chemical properties)on the biomass and its allocation.Seedlings in five age classes(1–2,3–4,5–6,7–8,and 9–10 years old)were collected by full excavation from 6 elevations(3800 m,3900 m,4000 m,4100 m,4200 m,4300 m)on the north and south slopes of Sejila Mountain in Tibet.15seedlings of each age class were investigated at one altitude.The individual effects of seedling age(SA)and the interaction effects of SA,slope aspect(SL),and elevation(EG),namely,SL×EG,SL×SA,EG×SA,and SL×EG×SA,had significant effects on the AGB of the seedlings(p<0.05),whereas BGB was only significantly affected by SA(p<0.001).The AGB and BGB of the seedlings showed a binomial growth trend with the increase in seedling age,and had an allometric relationship at different elevations,α(allometric exponential)varied from 0.913 to 1.046 in the northern slope,and from 1.004 to 1.268 in the southern slope.The biomass of seedlings on the northern slope was remarkably affected by stand factors,with a contribution rate of 47.8%,whereas that on the southern slope was considerably affected by soil factors with a contribution rate of 53.2%.The results showed that age was the most important factor affecting seedling biomass.The allometric pattern of seedling biomass was relatively stable,but in a highaltitude habitat,A.georgei var.smithii seedlings increased the input of BGB.Understanding seedling biomass allocation and its influencing factors is useful for evaluating plants’ability to acquire resources and survival strategies for adaptation to the environment in Tibet Plateau.

桉木屑颗粒燃料固体桥结构构建与燃烧特性研究

在成型燃料内部构建固体桥结构可有效改善其物理品质,利用不同粒径桉木屑构建了具有固体桥结构的颗粒燃料,并进一步研究了颗粒燃料的燃烧特性。提出的构建方法为同种原料不同粒径混配成型,在电子压力机上进行了粒径(0,1 mm]原料混配粒径(4 mm, 5 mm]原料的颗粒压缩成型实验,结果显示混配量5%~10%时颗粒内部长粒径粒子的交叉缠绕,可形成适量的固体桥结构,短粒径粒子填充饱满,粒子间结合紧密。较佳的混配量为5%,颗粒具有较高的松弛密度,为1 074.79 kg/m^(3),最高的Meyer强度,为23.93 MPa,最低的比能耗,为27.06 kJ/kg,平衡含水率为11.65%,吸水速率k为0.015 3 min^(-1)。在热分析仪上进行了成型颗粒燃烧实验,颗粒燃烧过程较为平稳且有所延长,在升温速率10~40℃/min的范围内,着火温度Ti在246.60~265.00℃之间,最大失重速率(dm/dτ)_(1max)在-6.84~-29.10%/min之间,综合燃烧指数S在7.26×10^(-12)~1.09×10^(-10)min^(-2)·K^(-3)之间。在X射线荧光光谱仪上分析了颗粒灰分的元素组成,预测颗粒燃烧时具有中等或较高的结渣沾污趋势。

铅胁迫对地黄生长及光合特性的影响

为了阐明铅(Pb)胁迫对地黄生长量及光合特征的影响,探讨药用植物对重金属胁迫的响应机制,以‘北京3号’地黄为试验材料,采用土培盆栽试验,以自然土壤加水为对照(0 mg·kg^(-1)),设置5个外源Pb浓度(50、100、200、300和400 mg·kg^(-1))处理,分析不同Pb浓度处理对地黄不同生长时期的生长量、叶片光合色素含量、光合参数和叶绿素荧光参数的影响。结果表明,高浓度Pb处理抑制了地黄叶片数、叶长、叶宽和叶厚的增长,光合色素含量和叶绿素荧光参数在整个生育期内随Pb浓度的升高均表现为先升高后降低,当Pb浓度高于200 mg·kg^(-1)时,电子传递速率、光合量子产量、最大荧光和初始荧光均显著降低;随Pb浓度的升高,地黄叶片的净光合速率、气孔导度和胞间CO_(2)浓度在地黄膨大初期至膨大前期逐渐降低,在膨大中期至收获期则表现为先升高后降低;蒸腾速率在整个生育期内随Pb浓度的升高呈下降趋势;地黄的光合特性对Pb的耐受性总体表现为50 mg·kg^(-1)处理>100 mg·kg^(-1)处理>0 mg·kg^(-1)处理>200 mg·kg^(-1)处理>300 mg·kg^(-1)处理>400 mg·kg^(-1)处理。综上所述,当Pb浓度低于200 mg·kg^(-1)时,地黄通过吸收光能、增强光合作用对抗Pb胁迫,当Pb浓度过高时,地黄光合作用减弱,对地黄的生长产生显著的抑制作用。研究比较了不同Pb浓度处理对地黄不同生育期生长量及光合特征的影响,解析了地黄对Pb元素的抗性机制,以期为农田土壤的安全利用及地黄的种植管理提供重要技术参考。

制浆纤维原料固废物基颗粒燃料的燃烧性能分析及改善

利用农业废弃草类植物进行制浆造纸可缓解中国制浆造纸工业面临的纤维原料短缺压力,将制浆过程产生的纤维原料废渣和制浆废液溶出物等固体废弃物进行颗粒燃料制备是实现工业固废物资源化利用的有效途径。为了解制浆过程不同纤维原料废渣的燃烧特性,将制浆过程备料工段产生的纤维原料废渣通过压缩成型技术制备了颗粒燃料,利用热重仪、扫描电镜、X射线衍射仪、热分析-红外-气质联用仪对不同纤维原料废渣固废物制备的颗粒燃料的燃烧特性进行了分析比较,研究探讨了添加制浆废液对颗粒燃料燃烧性能的改善效果。结果表明,草类纤维原料废渣基颗粒燃料因不可燃杂质含量较高,固定碳含量较低,其燃烧性能稍差于木材废渣基颗粒燃料;草类纤维原料废渣基颗粒燃料中的碱金属元素与硅元素在高温下反应生成结渣性金属硅酸盐类颗粒灰分;草类废渣基颗粒燃料因不可燃杂质含量较高导致固定碳不完全燃烧,增加了燃烧排放气体中CO气体成分。基于资源化利用制浆过程溶出物和改善颗粒燃料的燃烧性能,将10.28%固形物含量的制浆废液/麦草废渣混合物压缩制备颗粒燃料,颗粒燃料的综合燃烧指数为2.50×10^(-7)%^(2)/(min^(2)·℃~3),燃烧活化能为59.88 kJ/mol,与麦草废渣基颗粒燃料相比,燃烧指数提高了171.74%,燃烧活化能降低了22.72%,麦草废渣基颗粒燃料的燃烧性能得到明显改善。研究结果可为制浆造纸过程固体废弃物的资源化利用提供理论参考。

毛乌素沙地羊柴人工林生物量特征及固碳能力研究

为了巩固和提升沙地生态系统的碳汇能力,本研究选择毛乌素沙地羊柴(Corethroden‐dron fruticosum)人工林为研究对象,分析了不同林龄羊柴人工林的植被层、枯落物层、土壤层的生物量及碳密度特征。结果显示:羊柴地上生物量从8 a生到17 a生增加了1.76倍,而草本层生物量、枯落物层生物量差异不显著。羊柴的平均碳含量为48.11%,草本层的平均碳含量为42.83%,枯落物层的碳含量为42.29%。随着林龄增加,羊柴人工林碳密度显著增加(P<0.05),灌木层碳密度增长了175%,草本层增长了6.89%,枯落物层增长了15.12%,土壤有机碳含量增长了16.69%。研究表明,不同林龄的林分生物量存在较大差异,开展不同环境条件、林分结构下植被的生物量及碳密度研究,可为准确估算林分固碳能力提供科学依据。

光照与水分对骆驼蓬形态特征和生物量的影响

为探究骆驼蓬苗期对光照和水分的响应,采取光照和水分双因素控制试验,通过大田种植的方式,设置2种光照梯度(全光照T1、遮光T2),设置W1(1 d浇灌1次)、W2(7 d浇灌1次)、W3(14 d浇灌1次)3个水分处理梯度,每次浇灌量为15 L·m^(-2),分析不同光照与水分处理对骆驼蓬形态指标、生物量积累的影响。结果表明,骆驼蓬在全光照条件下长势均优于遮光处理,T1W1处理较T2W1处理骆驼蓬枝长、地径、叶片数和分枝数分别增加83.64%、67.21%、41.56%和116.34%,地上干重、地下干重分别增加250.77%和340.79%。遮光、高水分胁迫处理下骆驼蓬生长受限、叶片脱落、分枝减少,但无幼苗死亡现象。说明T1W1处理适宜骆驼蓬苗期生长,且骆驼蓬具有较强的适应能力,可作为光照充足地区的园林绿化及荒山绿化材料。

西藏三种木材生物质的燃烧特性及动力学分析

为了探讨西藏地区丰富的藏川杨、高山松和川滇高山栎3种木材生物质在燃烧过程中的反应机理,采用热重分析了三种木材的燃烧特性,通过Coats-Redfern积分法研究了其动力学特性。结果表明:3种木材生物质燃烧过程总体趋势一致,可分为失水干燥、生物质燃烧、焦炭燃烧和生物质燃尽共4个阶段,其中挥发分燃烧阶段失重占比最大。根据综合燃烧特性指数,川滇高山栎的燃烧特性最好,其次是藏川杨、高山松;随着升温速率增大,木材生物质的综合燃烧特性指数增大,燃烧速率增大,DTG曲线峰值增大,峰形变宽;藏川杨、高山松和川滇高山栎的最佳反应级数分别为1、2、2,相关系数均大于0.95。燃烧反应活化能从低到高分别为:藏川杨46.10 kJ/mol、高山松70.05 kJ/mol、川滇高山栎85.59 kJ/mol;频率因子从低到高依次为:藏川杨2.25×10^(4)min^(-1)、高山松3.99×10^(6)min^(-1)、川滇高山栎2.14×10^(7)min^(-1),该研究为优化燃烧过程和提高能源利用效率提供了理论依据。

南亚热带常绿阔叶林土壤微生物生物量碳氮年际动态特征及其影响因子

土壤微生物是土壤有机质和养分循环的主要驱动者,研究土壤微生物生物量碳氮变化、稳态特征及其对环境因子内在的长期响应机理具有重要意义。以南亚热带常绿阔叶林土壤为对象,对土壤微生物生物量碳和氮(MBC和MBN)、土壤有机碳(SOC)、总氮(TN)、总磷(TP)、可溶性碳(ROC)、速效氮(AN)、pH、土壤温度(ST)和土壤含水量(SWC)进行连续10年监测;应用方差分析、相关性和回归分析及稳态分析等探究MBC和MBN的年际变化和稳态特征及主要影响因素。研究结果表明:(1)旱季MBC和MBN含量分别在171.32—358.45和25.90—54.08 mg/kg区间波动,雨季分别在394.01—507.97和68.40—88.05 mg/kg区间波动;旱、雨季的MBC含量年际间变化显著(P<0.05),但MBN含量仅在旱季变化显著(P<0.05)。雨季MBC和MBN含量均显著高于旱季(P<0.01),且雨季的MBC和MBN含量是旱季的2倍以上。(2)旱、雨季的MBC与MBN之间均呈显著正相关(P<0.05)。在旱季,MBC和MBN均与ROC和AN含量显著正相关(P<0.05),此外,MBN含量也与TP(P<0.05)和SOC(P<0.01)显著正相关。在雨季,仅SOC与MBN呈显著正相关(P<0.05)。(3)在旱季,MBC含量变化主要受ROC(P<0.05)和AN(P<0.001)影响,MBN则受AN控制(P<0.05)。在雨季,AN(P<0.05)主导了MBC的变化,TP(P<0.05)和SOC(P<0.05)是MBN变异的主导因子。AN(P<0.001)和SOC(P<0.001)是旱、雨季土壤MBC和MBN变化的主导因子。(4)土壤MBC和MBC/MBN稳态指数在年际间均为绝对稳态型(P>0.05);雨季的MBN(P=0.685)为绝对稳态型,但旱季为非稳态(P<0.01,H>1)。雨季微生物熵显著高于旱季(P<0.01),表明土壤有机质质量及养分利用效率更高。综上,MBC和MBN含量受季节更替显著影响,且主要受土壤SOC和AN的影响;受旱季水分限制,MBN的稳态更差。

原料和热解温度对生物油分子蒸馏分离特性的影响

针对生物油组分复杂,难以直接应用的问题,该研究开展了不同生物油的分子蒸馏馏分分布规律的研究,并考察了不同原料和温度对生物油分子蒸馏分离特性的影响。热解液化试验结果表明,生物油组分以酸、醛、酮、酚、糖为主。随着热解温度的升高,松木生物油中轻质组分产率由21%不断降低至11%,而秸秆生物油中轻质组分产率稳定在20%左右。高温生物油各组分的平均分子自由程两极化程度加强,600℃制备轻质油蒸出比例最高,可以达到92%(松木)和86%(秸秆)。酚类化合物中酚羟基的数量可以影响其分离特性,较高的热解温度促进了酚羟基的产生,从而使酚类物质从蒸出部分(distillation fraction,DF)向残留部分(residual fraction,RF)中转移。分子蒸馏技术能够实现对不同生物油的有效分离,得到的DF中主要包含酸、酮和小分子酚类,RF则以糖和大分子酚为主,除了羟乙醛和苯并呋喃等化合物外,生物油中的大部分化合物的富集程度都可以达到90%以上。该研究可为快速热解生物油的分离及其后续提质研究提供一定的参考。