Altered vegetation structure and composition linked to fire frequency and plant invasion in a biodiverse woodland

Relationships between fire history, vegetation structure and composition, and invasion by introduced plant species have received limited attention in Australian woodlands. A study in a Mediterranean, fire adapted urban Banksia woodland remnant in the biodiversity hotspot of southwest Australia investigated: (1) Have significant changes occurred in the woodland tree canopy between 1963 and 2000? (2) Do correlations exist between fire frequency and canopy cover? (3) If there is a difference in the vegetation composition of Banksia woodland invaded by the South African Ehrharta calycina (PCe) and Pelargonium capitatum (PCp) compared to largely intact remnants (GC)? and (4) Do correlations exist between vegetation condition, composition, fire frequency and invasion? Aerial photography, processed in a Geographical Information System, was used to establish fire history and changes in canopy cover over time (1963–2000). PCe and PCp sites experienced the greatest number of fires, with a net reduction in canopy cover in all areas experiencing four or more fires (60% of all woodlands). Frequent fire corresponded with a decline in native cover, richness and diversity, a shift from native to introduced species, changes in the relative importance of fire response categories, and loss of native resprouting shrub cover. Life forms of introduced species, which included no trees, shrubs and perennial sedges, contrasted strongly with those of native species, which had poor representation of annual and perennial grasses. Clear ecological and conservation consequences due to the loss of species diversity, changes in fire ecology and invasion have occurred in the Banksia woodlands. This study provides an understanding of the invasion process, enhancing conservation knowledge to improve the adaptive management of the key threatening process of invasion in biodiverse communities.     

Net sulfur mineralization potential in Swedish arable soils in relation to long-term treatment history and soil properties

The long-term treatment effect (since 1957–1966) of farmyard manure (FYM) application compared with crop residue incorporation was investigated in five soils (sandy loam to silty clay) with regards to the net sulfur (S) mineralization potential. An open incubation technique was used to determine accumulated net S mineralization (S_AccMin) and a number of soil physical and chemical properties were determined. Treatments and soil differences in S_AccMin, as well as correlations with soil variables, were tested with single and multivariate analyses. Long-term FYM application resulted in a significantly (p = 0.012) higher net S mineralization potential, although total amounts of C, N, and S were not significantly (p < 0.05) increased. The accumulated S mineralization differed significantly (p < 0.05) between soils within this treatment. The measured soil variables were not significantly correlated to S_AccMin. Conclusively, different treatment histories influenced the quality (e.g., chemical composition) and cycling rate of the organic S pool, rather than its size.     

板栗土壤中微量营养元素地球化学特征

同时采用有效态和欧共体BCR(the Community Bureau of Reference)三步提取法对0-20 cm和20-40 cm土层中Ca,Mg,Fe,Zn,Cu,Mn进行形态分析,探索燕山山区板栗土壤中微量营养元索活性、形态分布特征和迁移能力.结果表明.栗粮间作会影响板栗对营养元素的吸收,且两层土壤中各元素活性相差不大;板栗纯林中0-20 cm土层的Cu,Zn活性明显高于20-40 cm土层;淋溶褐土和褐土性土两种土壤亚类,不同栽培制度对微量营养元素在板栗土壤中的形态分布特征影响不大.Cu,Zn,Fe主要以残渣态存在,Mn主要以可还原态和残渣态存在.且弱酸提取态高于其它元素.板栗土壤中元素的迁移能力排序为:Ca>Mg>Mn>Cu>Zn>Fe.     

张谷英村聚落景观公共空间类型及组成要素研究

湖南张谷英村始建于明代洪武年间,拥有中国罕见、特别的聚落景观。以张谷英村景观公共空间为研究对象,以景观公共空间类型和组成要素为研究内容,通过采取现场测绘、文献查阅的方法,总结得出村落景观公共空间有街巷空间、广场空间、公共绿地空间、住宅入口空间及墓地空间5类,景观空间组成要素有构成空间的底界面、侧界面、顶界面。其中街巷空间依据街巷等级尺度分为水街空间和巷道空间,以当大门段、百步三桥段、沿溪长廊段、民俗文化陈列馆段典型水街为列,得出水街的D/H＜1,空间富有亲切感和紧迫感;广场空间以民俗文化陈列馆前广场、下新屋前广场为研究对象,得出D/H=1~2,空间具有亲切感和围合感;公共绿地分布集中,景点突出;住宅入口空间分为临水入口和临路入口空间,空间多采取建筑后退形成阴角的处理方式,使空间的具有多变性。通过分析得出具有可识别度的张谷英村聚落景观公共空间,为新时代新农村公共空间的建设提供参考和借鉴。     

基于城乡建设用地增减挂钩的农村居民点整理现实潜力研究

农村居民点整理现实潜力分析是城乡建设用地增减挂钩专项调查工作的重要内容。笔者以江西省崇仁县孙坊镇为例,在现实潜力来源分析的基础上,以农村居民点斑块为评价单元,选取村庄状况、耕地适宜性和社会经济条件3个因素,及斑块规模、村庄破旧程度和耕地邻接度等8个指标进行综合评价,得出现实潜力类型。结果表明：迁移合并型农村居民点斑块是孙坊镇农村居民点整理的现实潜力来源,可分为易释放型、较易释放型、较难释放型、难释放型4种潜力类型。研究认为,现实潜力的释放应遵循先易后难原则,根据不同的潜力类型在时空上进行合理安排。     

Ecophysiological aspects and photosynthetic pathways in 105 plants species in saline and arid environments of Tunisia

In Tunisian arid regions, plant life forms, ecotypes, physiological types and photosynthetic pathways （03, 04 or CAM） remain unclear. Understanding the characters of these plant species could be important for land restoration. A literature survey was conducted for 105 plants species in arid regions of Tunisia. These plant species belong to several ecotypes： halophytes, xerophytes, gypsophytes, psamophytes, xero-halophytes, gypso-halophytes, psamo-halophytes, psamo-xerophytes, xero-gypsophytes and hygro-halophytes. The variation of photosynthetic pathway types in the 105 studied species shows that 56.2% were C3, 41.0% were C4, 1.9% were CAM and 1.0% were C3-CAM. The C3 pathway was more abundant in the halophytes, whereas the C4 one was more common in the xerophytes, gypsophytes, gyp- so-halophytes and psamo-halophytes. The ratio of C3 to C4 species （C3/C4 ratio） was 0.2 in the psamo-halophytes, 0.8 in the gypso-halophytes, 1.1 in the xerophytes, 1.6 in the xero-halophytes, 1.8 in the hygrohalophytes, 2.0 in the psamo- phytes and 3.8 in the halophytes. The annuals were mainly C3 plants whereas most of perennials were C4 ones. The C3/C4 ratio was 1.3 in succulent species and 1.4 in non-succulent species. Thus, succulence seems not to affect the distribution of C3 and C4 pathways within the studied plants. This investigation shows high percentages of C4 plants occurred in Tuni- sian arid regions. However, there were significant differences in their abundance among ecotypes. Basing on C3/C4 ratio, we can find that the abundance of the C4 pathway was in the following order： psamo-halophytes, gypso-halophytes, xe- rophytes, xero-halophytes, hygro-halophytes, psamophytes and halophytes. In Tunisian arid regions, C4 species were most abundant in xerophytes and less abundant in halophytes. In the Chenopodiaceae the number of C3 plants was 13 and the number of C4 species was 20 and in the Poaceae the number of C3 was 23 and the number of C4 was 19 species. Thus, the most C4 proportion was in the Chenopodiaceae a     

高职《养禽与禽病防治》课程的教学形式改革

[目的]适应新时期高职《养禽与禽病防治》课程改革的需要。[方法]从理论知识、实践能力和素质培养着手,根据学科发展和人才培养的趋势,对该课程教学内容、教学形式及实践性教学环节进行探讨和研究。[结果]该课程教学形式改革提高了教学效果,调动了学生的学习积极性、主动性,提高了学生的学习兴趣和解决实际问题的能力。[结论]该课程改革获得了成功。     

不同氮肥形态培土对烤烟生长及产量与品质的影响

[目的]研究不同氮肥形态培土对烤烟生长及中部叶品质影响,优化农业生产和保证烟叶质量。[方法]以烤烟品种云烟85为材料,不同氮肥形态及施肥方式对烤烟生长及经济性状以及中部叶烤后样品质的差异。[结果]中耕培土的同时,采取配套施肥对烤烟生长有利。以NO3--N处理的烟株表现出有助于烤烟揭膜后的早生快发,但后期生长状却不如NH4＋-N处理的烟株,两种处理的烤烟中部叶片物理特性皆不理想;NH4＋-N处理的烤烟氮肥利用率较强,烟碱含量较高,但由于其化学性质的特殊抑制了K的吸收,导致了烟叶中化学成分的不协调。[结论]NH4＋-N与NO3--N搭配施入的处理,烤烟生长状况最理想,化学成分协调,经济价值最高。     

中部地区经济发展的战略模式研究

在对我国几个区域性发展战略模式进行对比分析的基础上,提出了中部地区发展可选择的战略模式。     

南水北调中线工程对石家庄地下水水位的影响

系统分析研究区水文地质条件的基础上,建立了地下水系统数值模型,利用数值模型预测了在南水北调中线工程完成后对石家庄市区地下水位的影响,结果表明,市区地下水水位将得到回升,并逐渐趋于平稳。