城市绿地中硬质铺装对臭椿天然更新的影响

[目的]调查研究天津市南开大学校园绿地内臭椿(Ailanthus altissima)的天然更新状况,为城市自然林营造和管理提供科学依据。[方法]采用样方法进行调查,研究了臭椿更新苗数量特征、地径级和高度级的分布特征,用方差均值比率(Cx)、丛生指标(I)、负二项参数(K)、平均拥挤度指数(m*)、聚块性指数(C)和格局指数(IΔ)6种聚集强度指数分析臭椿更新苗的空间分布格局。[结果](1)城市绿地内臭椿存在天然更新现象,其更新苗地径级频率高峰出现在2~3mm地径级,且随着地径级的增大和减小,更新苗数量减少。更新苗高度级频率分布呈"间歇"型,个体频率高峰出现在低高度级上,主要集中在2~4cm高度级内。(2)城市绿地内臭椿更新苗的空间分布表现为集群分布,其Cx,K,m*,C,I,IΔ分别为2.24,1.26,2.81,1.79,1.24,1.79。[结论]硬质铺装影响臭椿天然更新的距离特征及更新苗的空间分布。     

城市绿地中臭椿更新苗空间点格局及种间关联分析

[目的]探究城市绿地中臭椿更新苗的数量特征、存活情况及空间分布格局,为城市绿地生境下乔木的天然更新和人工干扰或促进更新提供理论依据。[方法]运用种群静态生命表,点格局分析法中的双关联函数G(r)、H(r)函数分析臭椿更新苗的生存状况,空间分布格局及各龄级间的空间关联性。[结果]更新苗种群结构存在波动性,存活曲线趋于DeeveyⅡ型,低龄级和中龄级个体数量丰富,个体死亡率和消失率在前期和后期较稳定,中期先减后增,超过第5龄级(8~10cm)后,个体死亡率和消失率出现高峰。[结论]一侧和两侧铺装样地在空间上都呈现出不同程度的聚集分布,聚集强度随尺度距离的增大呈减小趋势,一侧铺装样地在尺度接近3.7m处有转为随机分布的趋势。龄级间,小尺度内多表现为无关联,随着尺度增加呈正显著相关;两侧铺装有正关联的龄级组合比一侧铺装样地多;较大尺度上,用径级代表龄级的更新苗间相关关系越接近,正关联越强。     

福建三明不同更新方式的米槠林群落结构特征

 为了解采伐迹地米槠林群落的演替恢复过程,通过野外标准地群落调查和重要值计算,分析了福建三明不同更新方式的米槠林群落结构特征。主要结果如下:1)3个标准地共调查到乔木有天然更新13科16属20种;人促更新5科6属6种;人工造林1科1属1种。2)不同更新方式的米槠林落群中米槠种群径级分布呈天然更新:低径级的个体占的比重较大,随径级增大,立木株减少;人促更新:低径级个体占的比重极小,而中、高径级个体占的比重极大;人工造林:呈正态分布。3)不同更新方式的米槠林群落中米槠种群的垂直结构呈天然更新:自上而下的递增趋势;人促更新趋于正态分布;人工造林服从正态分布。3种更新方式的米槠林群落中的物种丰富度为天然更新>人促更新>人工造林。     

天津市临港城市湿地植物群落特征及多样性

[目的]探究城市湿地植被恢复的群落特征及物种多样性格局,为城市湿地保护和恢复策略的制订提供科学依据。[方法]采用样方法对天津临港恢复湿地的植物群落进行调查,计算群落植物种重要值,并利用组平均法聚类,分析物种多样性格局。[结果](1)乔灌草各层主要优势物种分别为国槐(Sophora japonica)、刺槐(Robinia pseudocaacia);柽柳(Tamarix chinensis)和芦苇(Phragmites australis),灌木层中的柽柳重要值最大。(2)植被划分为4组、17个群丛类型,过渡区广布种斑块频度最大(32.7%),以国槐+银杏群落(Sophora japonica+Ginkgo biloba)为主;滨水湿地斑块群落频度最小(17.3%),以柽柳—芦苇群落(Tamarix chinensis-Phragmites australis)为主。(3)Shannon-Wiener指数与Simpson指数总体变化趋势较一致,最高值均出现在金叶榆—紫穗槐(Ulmus pumila-Amorpha fruticosa)群落;Pielou均匀度指数≥0.8的样方占样方总数的53.8%;近水绿地斑块丰富度指数强度较大,物种复杂度高。(4)调查中发现有刺槐、旱柳(Salix matsudana)、火炬树(Rhust yphina)等乔木更新苗出现,出现明显的群落演替和自然更新现象。[结论]研究区植物种类丰富,近水绿地斑块物种多样性较高,但湿生植物群落总体优势不明显。     

哈尔滨市土壤保持服务价值时空演变及其驱动力

[目的] 土壤侵蚀是全球性的重要环境问题,严重制约了人类的生产和生活。定量研究土壤保持服务价值为区域水土保持措施的制定,哈尔滨市水土保持功能分区规划提供科学依据。[方法] 基于InVEST模型泥沙输移比例模块,对哈尔滨市2000,2010,2020年的土壤侵蚀量和土壤保持量进行评估,借助空间自相关法分析土壤保持量的空间聚集类型,并利用参数最优地理探测器揭示其空间异质性形成的驱动力。[结果] ①2000,2010,2020年哈尔滨市土壤保持量分别为2.18×10⁹,2.07×10⁹,2.77×10⁹ t,呈现先减少后增加的趋势,整体呈现"西低东高"的空间分布格局; ②土壤保持量呈现强烈的空间正相关,以低-低聚集和高-高聚集类型为主,低-低聚集类型面积呈现下降趋势,而高-高聚集类型则呈现先降低后上升的趋势; ③高程、降水量和坡度对哈尔滨市土壤保持量空间异质性的解释力最强,平均解释力分别为0.225 9,0.198 9,0.180 4,其中坡度和降水量与其他因子的交互作用,是研究区解释力最强的交互因素。[结论] 哈尔滨市应加强对城市西部和松花江沿岸的水土治理,同时维持城市北部和东部良好的水土状况,避免大规模的人类干扰活动。     

河南省森林碳汇价值时空特征及其影响因素

[目的] 分析河南省森林碳汇价值时空特征及影响因素,为促进河南省“碳达峰、碳中和”目标实现提供参考。[方法] 采用蓄积量扩展法和造林成本法评估2010-2020年河南省森林碳汇价值,分析其时间变化特征,运用莫兰指数探究其空间聚集特征,并构建扩展STIRPAT模型分析影响森林碳汇价值的因素。[结果] ①河南省森林碳汇价值在时间上呈现持续上升趋势,由2010年的4.18×10¹⁰元增加至2020年的6.71×10¹⁰元,在空间分布上呈现为“豫西、豫南高,豫东、豫北低”的态势,且存在显著的正向空间聚集效应,碳汇价值显著高值聚集区域分布在豫西和豫南地区,显著低值聚集区域仅有两处且分布散落。②除碳汇强度对河南省森林碳汇价值有负向作用外,森林面积比例、城镇化率、林业产业比例、人均GDP均产生正向影响作用,其中森林面积比例是推动研究区域森林碳汇价值增长的主要因素。[结论] 河南省森林碳汇价值潜力巨大,未来应分区域推进森林碳汇价值实现。     

吉林省森林生态系统服务价值评价

[目的]对2009—2013年吉林省的森林生态系统服务价值进行评价,为森林生态系统的可持续经营和管理提供依据。[方法]以第8次森林资源清查和吉林省林业调查规划院编制的8个林业局森林经营方案等数据为基础,建立森林生态系统服务评估指标体系和定量方法,采用价格倒算法推演森林涵养水源价格公式。[结果](1)2013年吉林省森林生态系统服务总价值为13 801.35亿元。(2)森林生态系统各服务价值排序为净化大气环境(10 225.91亿元,占总服务价值的74.09%)生物多样性维护(1 063.27亿元,占7.70%)涵养水源(997.70亿元,占7.23%)保育土壤(941.61亿元,占6.82%)农田/草场防护(564.75亿元,占4.09%)固碳释氧(8.12亿元,占0.06%)。[结论]在吉林省森林生态系统服务价值中,以净化大气环境、生物多样性维护和涵养水源服务价值最高。倒算法推演得到的结果较以往研究更贴合实际,有力地提升了森林涵养水源价值核算的准确性和合理性,也使森林涵养水源价值研究评价方法更加科学。     

辽河源典型森林类型的土壤水文效应

[目的]研究辽河源地区典型森林类型林下土壤的水文效应,为辽河源森林生态系统健康的监测和评价提供理论佐证。[方法]选取典型森林类型,采用不同入渗模型拟合各森林类型土壤的入渗过程。[结果](1)土壤容重变化范围为1.21~1.56g/cm3,油松中龄林最大,山杨成熟林最小;土壤总孔隙度变化范围为41.26%~54.38%,山杨成熟林最大,油松中龄林最小;(2)山杨成熟林土壤蓄水能力最强,为1 087.56t/hm2;油松中龄林土壤蓄水能力最小,为825.17t/hm2;(3)山杨成熟林稳渗速率最大,为1.33mm/min;(4)霍顿(Horton)入渗模型和菲利普(Philip)入渗模型能较好地反映各森林群落土壤入渗过程,但通用幂函数模型拟合结果较差。[结论]不同森林类型土壤均表现出随着土层深度的增加容重逐渐增加的现象,阔叶林林下土壤蓄水能力要强于针叶林,通过比较认为可以利用霍顿(Horton)模型作为研究该区森林土壤水文功能的重要手段。     

呼伦贝尔沙地樟子松更新苗分布特征研究

沙地樟子松在沙地上持续进行的天然更新对退化生态系统的植被恢复与重建,沙地生态系统各种效益的持续发挥,以及我国北方绿色生态屏障的建立都具有重要意义.本文通过调查发现,在呼伦贝尔沙地,天然分布的沙地樟子松更新状况良好,经常可以见到10～20龄的更新苗群丛.在不受干扰的情况下,樟子松单株下常见不同龄级的幼苗和幼树,其中6～10龄所占的比例最大,1～5龄次之,这与近年来干旱加剧和过度放牧的关系密切.随着林木单株的生长发育,从幼年期经青年期、壮年期到老年期,单株下方更新苗的密度逐渐增加,成熟单株下方更新苗的密度达到最大,以后渐趋平缓.过熟单株的结实率依然较高,但林下更新苗的数量略有减少.通过对沙地樟子松单株下的更新苗进行分布型计算,认为樟子松更新苗呈集群分布的格局.在不考虑樟子松单株的龄级和其生境特殊性的情况下,沙地樟子松单株下的更新苗集中分布在林冠下北偏东方向的一个扇形区域内,产生这种现象的主要原因是光照和风向的共同作用产生的.     

基于改进CASA模型的陕西省植被NPP遥感估算

[目的]探究陕西省陆地生态系统植被群落生产状况,分析陕西省植被NPP时空格局变化及影响因素,为准确评估陕西省陆地生态系统碳源/汇,实现区域生态可持续发展,达成碳中和目标提供参考依据。[方法]基于温度—植被干旱指数(Temperature Vegetation Dryness Index, TVDI)对CASA(Carnegie-Ames-Stanford Approach)模型水分胁迫因子进行改进,从而估算陕西省2010—2020年植被NPP,并利用热点分析法、趋势分析法以及地理探测器对陕西省植被NPP进行空间分布格局、年际变化趋势和驱动因子研究。[结果](1)陕西省NPP空间分布呈现南高北低、冷热点区域差异明显的特征;(2)陕西省2010—2020年NPP平均值介于331.02～416.34 gC/(m²·a),NPP均值在100～600 gC/(m²·a)占比最大,最低值和最高值区间占比不足20%;(3)全省2010—2020年83.3%的面积植被NPP值无显著变化,4.2%的面积呈增加状态,12.5%的面积NPP值呈下降趋势;(4)降水...     

Agricultural potential of Mediterranean grain and forage legumes: Key differences between and within Vicia species in terms of phenology, yield, and agronomy give insight into plant adaptation to semi-arid environments

In order to identify key adaptive traits which affect productivity in Mediterranean grain and forage legumes and simultaneously determine the agricultural potential of a wide range of Vicia species, germplasm collected from the wild throughout the eastern Mediterranean was grown under semi-arid conditions in Tel Hadya, Syria (313 mm growing season rainfall). These included species currently in use in Mediterranean agriculture, such as V. sativa L., as well as those more widely used in the past-such as V. ervilia L., but also a broad selection from Section Narbonensis (B. Fedtsch. ex Radzhi) Maxted, including V. narbonensis L, V. johannis Tamamsch., V. hyaeniscyamus Mout., V. serratifolia Jacq., and V. kalakhensis Khattab et al. V. faba, a near relative of the taxa in Section Narbonensis, was included as a domesticated control. Where applicable, a representative range of subspecies was used. Accessions were chosen from a wide range of habitats in terms of latitude (31.02–40.72 decimal^o), longitude (27.1–43.17 decimal^o), altitude (20–1510 m), rainfall (180–1700 mm/yr) and soil depth (5–50 cm) in order to maximise diversity within species. Agricultural potential was determined by measuring seed, hay and biological yield, as well as agronomic traits such as harvest index, standing crop height, and seed size. The comparative influence of phenology and key agronomic traits such as plant habit and seed size on productivity varied tremendously between species, depending on their reproductive strategies. In V. sativa and V. ervilia, the smaller seed species which rely on long vegetative phases and growing seasons to accumulate sufficient biomass to set seed, and in which there was comparatively little agronomic variation, phenology had a large impact on yield. In early emerging taxa such as V. ervilia and V. s. subsp. sativa, with built-in long vegetative phases and growing seasons, seed yield was negatively correlated with flower ing (r = –0.86 to –0.88), whereas the opposite was the case for later emerging taxa such as V. s. subsp. nigra (L.) Ehrh. (r = 0.95). Within V. narbonensis and relatives, the larger seeded Vicia species which rely on more conservative reproductive strategies where high seedling vigour associated with large seeds enables the species to enter reproductive phases relatively early, phenology had a much smaller impact on yield than did variation of key traits such as seed weight, plant habit and pod shattering. Among the undomesticated germplasm harvest indices ranged from 0.09–0.31, hay yields from 0.1–3.4 t/ha, seed yield from 0–2.0 t/ha, and dry matter at maturity from 1.6–6.5 t/ha. Sub-specific taxonomy was crucial in determining agronomic potential. V. narbonensis var. aegyptiaca Kornhuber ex Asch. et Schweinf. showed the most potential, combining an upright habit, large seeds (212 mg) and tendency to retain intact pods after maturity, with the highest yield, harvest index and crop height of all the wild Vicia species. V. sativa subsp. sativa, V. ervilia and V. narbonensis var. narbonensis were less productive, but still showed agricultural potential. The smaller seeded V. narbonensis, var. affinis, var. jordanica H. Schäf. and var. salmonea (Mout.) H. Schäf., and their close relatives V. johannis, V. hyaeniscyamus, V. serratifolia and V. kalakhensis have little to offer Mediterranean agriculture on the basis of poor agronomy.     

Changes in trace element speciation in kola north surface waters during snow melt

The powerful mass-flow of melt water during the brief period of spring thaw provides a surge of pollutants and causes extremely toxic short term conditions. Together with the increase in total metal concentrations during this period, a redistribution in metal speciation occurs that increases the proportion of more toxic forms. Concentrations of ion-exchangeable fractions of nickel (Ni), copper (Cu), aluminium (Al), and manganese (Mn) show strong negative correlations with pH. The sum of complex metal species shows a strong positive correlation with total organic carbon (TOC). A data analysis model based on relationships observed between key parameters and metal behaviour together with gidrological data allowed an assessmrnt of the metal impact on waterbodies from accumulated airborne pollution (Ni, Cu) as well as from accelerated leaching from watersheds (Al, Mn).     

On the Taxonomy of the Members of ‘Saccharum Complex’

The difficulty and problems encountered in the study of cultivated plants, in general and sugarcane, in particular has been indicated. In order to understand these problems, a brief review on the taxonomy of Saccharum and closely related taxa, namely, Erianthus, Sclerostachya, Narenga and Miscanthus (generally known as ‘Saccharum complex’) has been given. A short account on the important morphological features that are specific to sugarcane has also been stated as classification is commonly based on such morphological characters. A note has been added on the chromosome number, origin, and distribution of the species of ‘Saccharum complex’ members. Taxonomic keys have been devised for identification of the genera of Saccharinae and for the species of Saccharum and Erianthus occurring in India. A new combination, Sclerostachya fallax (Balansa) Amalraj et Balasundaram, has also been proposed.     

The major features of an infestation by the invasive weed legume gorse (Ulex europaeus) on volcanic soils in Hawaii

Gorse (Ulex europaeus) infestation occupies over 4,000 ha of agriculture and conservation lands on the southeastern slope of Mauna Kea on the Island of Hawaii. The aim of this investigation is to identify ecological features associated with this weed invasion by comparing the gorse-infested areas to the surrounding uninfested areas of this landscape. The soils within the gorse infestation are more acidic, resulting in higher levels of KCl-extractable Al and lower levels of Mehlich III-extractable Ca, Mg, Mn, and Zn. Yet, gorse accumulates higher concentrations of Ca, Zn and, Cu than the kikuyu grass (Pennesitum clandestinum), which is ubiquitous throughout the site. The Ca:Al and Mg:Al molar charge ratios of the soils are lowest within the epicenter of the gorse infestation, while the molar ratios are highest in the gorse apical stem tissues. All gorse plants are nodulated and have higher nitrogen contents than the surrounding kikuyu grass. Furthermore, the δ¹⁵N of the gorse stem tissues approaches 0‰, suggesting that nitrogen is being symbiotically fixed from the atmosphere. Characterization of the Bradyrhizobium isolated from gorse nodules shows similarities and distinctions to Bradyrhizobium isolated from the endemic legume koa (Acacia koa) within the same location. Population densities of the indigenous Bradyrhizobium are higher within the gorse rhizosphere than the kikuyu grass. Soil acidification, nutrient depletion, and symbiotic nitrogen fixation distinguish gorse-infested areas from the surrounding uninfested areas. These observations suggest that gorse has a competitive advantage over kikuyu grass under conditions of soil nutrient deficiency.     

Polymorphism of high molecular weight glutenin subunits in three species of Aegilops

A collection of 136 accessions of Aegilops umbellulata (39), Ae. comosa (75) and Ae. markgrafii (22) was analysed for high-molecular-weight (HMW) glutenin subunits composition. The homogeneity of the accessions was studied and 55.1% of the collection was homogeneous for HMW glutenin subunits (29 Ae. umbellulata, 33 Ae. comosa and 14 Ae. markgrafii). The HMW glutenin subunits of Ae. umbellulata are encoded by the Glu-U1 locus; in Ae. comosa results showed that this proteins are encoded at the 1M chromosome, and the locus was named Glu-M1. In Ae. markgrafii it was assumed that HMW glutenin subunits were encoded by an homoeologous locus and it was named Glu-C1. All the accessions of Ae. umbellulata and Ae. markgrafii expressed both, x-type and y-type subunits. Among the Ae. comosa accessions, only one expressed an x-type subunit alone. All the accessions of Ae. umbellulata and some of Ae. comosa had x-type glutenins of higher molecular weights than those commonly present in bread wheat. A total of 8 alleles were detected at the Glu-U1 locus, 11 at the Glu-M1 and 4 at the Glu-C1. The new HMW glutenin variation found in this work suggests their possible utilisation in breeding for wheat quality.     

Nematofauna associated with exotic and native leguminous plant species in West Africa: effect of<Emphasis Type="Italic"> Glomus intraradices</Emphasis> arbuscular mycorrhizal symbiosis

Ten leguminous trees, four exotic species (Australian Acacia) and six indigenous species (three Sahelian Acacia spp. and three Sesbania spp.), were grown for 4 months in a natural Sahelian soil inoculated with or without the endomycorrhizal fungus, Glomus intraradices. In control trials, the determinant factor structuring the soil nematode fauna was the plant species, related plants having a similar influence on the nematode community in the soil. Soil nematode abundance increased from exotic acacias (3.3 g^-1 dry soil) to native acacias (11.5 g^-1 dry soil) and Sesbania species (17.6 g^-1 dry soil). Plant feeding nematodes (mainly Scutellonema and Tylenchorhynchus) were significantly less abundant under exotic acacias (1.4 g^-1 dry soil) than under native acacias (7.2 g^-1 dry soil) or Sesbania species (7.3 g^-1 dry soil). Bacterial feeding nematode density increased from exotic acacias (1.2 g^-1 dry soil) to native acacias (3.0 g^-1 dry soil) and Sesbania species (7.7 g^-1 dry soil) as total densities. However, the differences in the structure of the nematode communities between plant groups were suppressed in the presence of the mycorrhizal fungus. In fact, no difference in nematode densities remained between plant groups when G. intraradices developed in several dominant taxa belonging to different trophic groups, particularly: Tylenchorhynchus, Apelenchina, Cephalobus and Dorylaimoidea. This study clearly indicated that inoculation with the arbuscular mycorrhizal fungus G. intraradices diminished the plant-specific effect on the structure of the soil nematode community.     

Powdery Mildew Resistance in a Collection of Chinese Barley Varieties

One hundred and forty-seven Chinese barley varieties maintained at the Gene Bank of the National Barley Improvement Centre, Zhejiang, and 84 progenies from these varieties were tested at the seedling stage for their reaction to 32 selected pathotypes of Blumeria graminis f. sp. hordei. Eighteen resistance spectra were identified comprising single or combined resistances from eight known (Ml(Bw), Ml(Ch), Mla7, Mla8, Mla9, Mla13, MlaRu4 and Mlg) and six unknown resistance genes. The most frequent gene was Ml(Bw), which was found in 69 varieties and previously detected in only a few European winter barley varieties. The genes Mla8 and Ml(Ch) were also often present, but other resistance genes were rare. After inoculation, considerably fewer pathogen colonies were observed in ‘Aiganqi’ and one line of ‘Tong5’. Twenty varieties were composed of lines with different resistance genes. China is likely to be a region of origin of the genes Ml(Bw), Mla7, as well as three unknown genes found in original landraces and perhaps another three unknown genes detected in cultivars bred in China. The resistances of varieties from the Zhejiang province and those originating from 11 other Chinese provinces were quite different. Unfortunately, none of the varieties are promising sources of resistance to powdery mildew and China does not seem to be a region suitable for identifying such sources.     

Genetic diversity of rhizobia associated with indigenous legumes in different regions of Flanders (Belgium)

We investigated the diversity of rhizobia isolated from different indigenous legumes in Flanders (Belgium). A total of 3810 bacterial strains were analysed originating from 43 plant species. Based on rep-PCR clustering, 16S rRNA gene and recA gene sequence analysis, these isolates belonged to Bradyrhizobium, Ensifer (Sinorhizobium), Mesorhizobium and Rhizobium. Of the genera encountered, Rhizobium was the most abundant (62%) and especially the species Rhizobiumleguminosarum, followed by Ensifer (19%), Bradyrhizobium (14%) and finally Mesorhizobium (5%). For two rep-clusters only low similarity values with other genera were found for both the 16S rRNA and recA genes, suggesting that these may represent a new genus with close relationship to Rhodopseudomonas and Bradyrhizobium. Primers for the symbiotic genes nodC and nifH were optimized and a phylogenetic sequence analysis revealed the presence of different symbiovars including genistearum, glycinearum, loti, meliloti, officinalis, trifolii and viciae. Moreover, three new nodC types were assigned to strains originating from Ononis, Robinia and Wisteria, respectively. Discriminant and MANOVA analysis confirmed the correlation of symbiosis genes with certain bacterial genera and less with the host plant. Multiple symbiovars can be present within the same host plant, suggesting the promiscuity of these plants. Moreover, the ecoregion did not contribute to the separation of the bacterial endosymbionts. Our results reveal a large diversity of rhizobia associated with indigenous legumes in Flanders. Most of the legumes harboured more than one rhizobial endosymbiont in their root nodules indicating the importance of including sufficient isolates per plant in diversity studies.