Effect of Gap Size on Seedling Establishment of Tsuga longibracteata

Effects of three gaps which are large （118 m^2）, medium （86 m^2） and small （20 m^2）, respectively, and under canopy of Tsuga longibracteata forest on the seedling establishment of T. longibracteata were studied through seed burial experiments from December 2003 to January 2005 in Tianbaoyan National Nature Reserve of Fujian, China. The results showed that the area of gap had an evident effect on the seedling establishment of T. longibracteata. The seedling emergence rates of T. longibracteata in plots of large gap, medium gap, small gap and under canopy were 10%, 10%, 4% and 6%, representing an increasing trend along with the gap size increasing without a significant difference. Rain eroding and insects feeding were two main factors leading to seedling death. The larger the gap size was, the more seedlings were killed by rain erosion and the fewer seedlings were killed by insects feeding. The emergence time of seedlings was almost same in all plots while their death time was different respectively. The gap size had a significant impact on seedling survival rate. The seedling survival rate was highest in the medium gap plot （27.0%） and next to the highest in large gap plot （7.3%）, and seedling in small gap plot and under canopy plot died out after one growing season. Increased light supply in gaps was favorable for the seedlings growth and survival. Increased light supply in the large gap could enhance the growth of seedling leaf and root of T. longibracteata, and the seedling in turn allocated more dry mass to root and leaf, but it has little impact on the growth of stem. This research indicates that T. longibracteata is a pioneer species and its seedling establishment need a medium or large gap （〉50 m^2）.     

柚木嫩枝扦插

对柚木组培苗田间扦插扩繁的主要技术开展了研究.结果表明:不同无性系的萌条数量有显著差异,高的达14.8 条/月,低的5.5 条/月,平均9.1 条/月;从0.05～2.00 mg/L,随着IBA浓度的提高,生根率、根条数、总根长等生根指标均呈现有规律的变化;综合考虑各种生根指标,以IBA0.05 mg/L为最佳生根激素处理;扦插介质对柚木插穗生根有显著的影响,以泥炭土 黄心土按1∶1混合为最佳扦插介质;不同无性系的扦插成活率不同,从56.7%至90.0%,变动幅度大;随扦插季节变化,生根率和成活率均呈现有规律的变化,5～6月份的生根率中等,7～8月最高,9～10月份迅速下降,成活率随季节的变化也是两头低、中间高,6～8月的成活率最高,大于93%;综合考虑生根率、成活率和苗木生长期,5～8月份为柚木适宜的嫩枝扦插季节.     

Gas exchange of the lowest branches of young Scots pine: a cost-benefit analysis of seasonal branch carbon budget

A cost-benefit approach was developed to analyze the carbon budget of the lowest Scots pine (Pinus sylvestris L.) branches subject to abscission. In addition to within-branch growth and respiratory costs, the budget included an estimation of a branch's share of the maintenance respiration of the stem and root. A branch was considered productive if the budget was positive. Foliar gas exchange and woody-tissue respiration were non-destructively measured at monthly intervals during the growing season on the six lowest branches of 10-year-old Scots pine trees, to the moment when the branches died naturally. Photosynthetic light response and temperature response of respiration, together with measurements of canopy light conditions and meteorological data, were used to calculate seasonal carbon budgets for the branches. Maintenance respiration of stems and roots was estimated from published data. All but one of the branches studied were found to be nonproductive over the growing season. Following a decrease in photosynthetic capacity in July, the cumulative budget became negative and the branches died, indicating that a negative carbon budget corresponds with the onset of abscission of the lowest branches.     

Seasonal variation in the biomass and non-structural carbohydrate content of fine roots of teak (Tectona grandis L. f.) plantations in a dry tropical region

Seasonal variation in the biomass and total non-structural carbohydrate content (TNC) of fine roots of teak (Tectona grandis L. f.) were studied in 19- and 29-year-old plantations in a dry tropical region. Fine root TNC content was highest during the dry summer (May), and lowest in the early part of the rainy season (July). Generally, seasonal trends in TNC content were the opposite of those in fine root biomass. The TNC concentration of roots increased with diameter and decreased with soil depth. In the 19-year-old plantation, fine root TNC content was approximately 12% higher than in the 29-year-old plantation.     

Effects of overstorey canopy, plant-plant interactions and soil properties on Mediterranean maritime pine seedling dynamics

Seedling emergence, survival and early growth of the Mediterranean conifer P. pinaster were studied under closed canopy and open canopy (gaps) cover conditions in a Mediterranean forest of central Spain during two consecutive years (March 2008 to January 2010). Our main objective was to understand how overstorey structure, shrubs and soil properties influence recruitment in this species. Natural emergence and seedling survival were significantly better under closed canopy cover than under open canopy during the two consecutive years of the study; survival increased as radiation decreased. Proximity to shrubs under closed canopy cover was associated with lower mortality rates as well as a positive and apparently transitive effect on early growth. Amelioration of microclimatic conditions is hypothesized as the primary facilitation agent of those observed. Younger seedlings established during the spring of 2008 experienced higher mortality rates than older seedlings established before 2008, and soil properties affected seedling survival significantly. Water stress during summer appeared to be the main cause of seedling mortality in both years. Our study suggests that seedlings of shade-intolerant species may require overstorey cover to establish successfully, and that positive plant-plant interactions in forest communities may be more important than expected in the milder conditions provided by overstorey canopy cover.     

Effect of different pre-sowing treatments on seed germination percentage and growth performance of <Emphasis Type="Italic">Acacia auriculiformis</Emphasis>

Seed morphology, germination and seedlings growth of Acacia auriculiformis were studied. The experiment was conducted in the nursery of Forestry and Wood Technology Discipline, Khulna University, Bangladesh. Matured seeds of the species were collected from healthy trees of road side plantation from different areas of Khulna District, Bangladesh and treated with five pre-sowing treatments (control, immersion in cold water, immersion in hot water, scarification with sand paper and immersion in concentrated H₂SO₄). The average length, breadth and thickness were found to be (0.58±0.017) cm, (0.44±0.007) cm and (0.20±0.089) cm, respectively. Germination was conducted in polybags with a mixture of top soil, coconut husk, coarse sand, and fine sand in a ratio of 3:4:1:1. Results reveal that pre-sowing treatments influences the germination rates of seeds that significantly increase the percentage germination compared with those in control (43%) and cold water treatment (52%). The highest germination success rate was found 83% in hot water treatment followed by 78% in scarification with sand paper, and 75% with immersion in H₂SO₄. Germination started from 7 to 12 days and completed between 28 and 35 days period in all treatments. ANOVA showed the significant difference (p<0.05) among the treatments in seed germination, but no significant difference among treatment with regard to starting day, closing day and total germination period. In case of height and diameter growth, seedlings originated from the seeds with hot water treatment shows significantly higher in wet season (from May to July). Hot water treatment can be recommended on seed germination of the species in rural Bangladesh.     

Pasture production in a silvopastoral system in relation with microclimate variables in the atlantic coast of Spain

Grasses and legumes of high productivity and nutritional quality are a good alternative as pasture supplements in rangelands of low quality forage. Orchardgrass (Dactylis glomerata L. cv. `Artabro') and white clover (Trifolium repens L. cv. `Huia') are known as shade tolerant and low flammability species that have been successfully used in agroforestry systems in Galicia, both diminishing fire hazard compared with natural shrublands. In this study, annual and seasonal production of a grass mixture of both species was quantified during 3 years in a pinewood under different tree canopy covers. Regardless of cover, pasture production increased in summer, and decreased from fall to spring. We obtained a significant correlation between annual pasture production and light transmission through the tree canopy (R² = 0.96, P<0.05). Light transmittance through a maritime pine canopy (Pinus pinaster Ait.) was higher than through a Scots pine canopy (P. sylvestris L.), corresponding to 36–57% and 16–21% of full sunlight respectively. The highest herbage production was obtained in no tree stands and the lowest under a P. sylvestris canopy. Fluctuations inlight transmission, temperature and PAR (Photosynthetically Active Radiation) under tree canopy were less apparent compared with no tree stands. Variation in seasonal production was more pronounced in stands without trees, and appeared more uniform when percentage of light intercepted by tree canopy increased.This revised version was published online in November 2005 with corrections to the Cover Date.     

Seasonal dynamics and impact factors of urban forest CO<Subscript>2</Subscript> concentration in Harbin,China

CO₂ concentrations in different plant communities (larch, birch, lilac, and grassland) were measured during the growing season in the Heilongjiang Forest Botanical Garden to study diurnal variation, seasonal and annual dynamics and factors that impact CO₂ concentration in different spaces. CO₂ concentration in different communities in green lands had an obvious diurnal variation, chronically decreasing, and temperature influenced the lilac area and the grassland. Seasonally, CO₂ was lowest in the larch green land (344.03 ± 23.03 μmol/mol) and highest in the grassland (360.13 ± 22.43 μmol/mol). The overall trend in CO₂ concentration was autumn > spring > summer; temperature is the main factor controlling variation in CO₂ concentrations during the growing season; the CO₂ concentration at the larch, birch, lilac, and grassland types of sites was negatively correlated with land surface temperature and air temperature, and the CO₂ concentration at the larch and birch sites was positively correlated with atmospheric pressure. Without any obvious annual change law, further study and observation are needed.     

木瓜海棠长寿冠扦插技术研究

研究扦插部位、扦插基质、扦插时间以及植物生长调节剂对长寿冠扦插成活率的影响,结果表明:①中间枝段扦插成活率最高,顶部次之,基部成活率最低;②以泥炭∶珍珠岩∶蛭石=3∶2∶5的混合基质作为扦插基质的扦插成活率最高,为74.67%;③3—9月均能进行扦插,但以3—6月为最佳扦插时间,7—9月份进行扦插,需要注意加强光照、水分等管理;④NAA、IBA、GGR 500 mg.L-1和IAA1 000 mg.L-1处理插穗能提高扦插成活率10%以上。     

红皮云杉S_(3-0)苗龄型苗高年生长规律的研究

以红皮云杉S3-0苗龄型的苗木为对象,连续3 a观测年生长规律,结果表明:红皮云杉S3-0整个生长期可划分为4个阶段,分别为:生长初期,5月中下旬至6月上旬;生长速生期,6月上旬至7月上旬;生长未期,7月上旬至7月下旬或8月上旬;停止生长期,7月下旬或8月上旬。     

核桃楸不同种源苗期生长的研究

以长白山区具有代表性14个核桃楸种源为研究对象,分析不同播种方法对出苗率和保苗率影响,并进行不同种源苗期生长量观测。结果表明:种子沙藏春播和青果秋播对出苗率和保苗率影响不显著(P0.05),沙藏春播出苗率较高的是4#、5#、14#种源,而青果秋播出苗率较高的是7#、8#种源,其保苗率变化趋势与出苗率一致。经聚类分析,14个种源1、2 a生苗木生长可分为三类,其中第Ⅲ类4#、14#、13#、5#、8#种源苗木高生长和地径生长表现优良。     

Tree seedling survival and growth in logged and undisturbed seasonal deciduous forest fragments in central Brazil

We evaluated the survival and growth of Amburana cearensis, Cedrela fissilis, and Sterculia striata seedlings in three seasonally tropical dry forest fragments that were subjected to different logging levels (intact, intermediately and heavily logged). In each fragment, we planted 40 seedlings of each species and monitored these over a period of 1 year. The highest seedling survival rate (64%) occurred in the heavily logged fragment, which, however, also had the highest mortality risk for all species during the dry season. Only S. striata seedlings had different survival rates among the fragments. Height and diameter growth were higher at sites with higher canopy openness in the wet season. The survival and growth rates of seedlings planted in logged fragments indicate that this technique can be applied to restore and enrich logged forests of the Paran? River Basin.     

木质居室环境对哺乳动物一些生理指标的影响

用木材与木质材料组成的内装环境不但对居室的温度、湿度有调节作用,而且对动物体的生长、发育有一定的影响,这就是木材独有的环境学调节特性。近年来,中国台湾、日本和国内等学者相继开展了这方面的研究工作。王松永等(1997)、WangSongyong等(1994a ;1994b)对木质内装材料的房     

腾冲红花油茶不同无性系嫁接成活率研究

采用双向完全随机区组试验,选择1月、5月不同时间嫁接和39个无性系2因素,每区组嫁接株数不低于120株,设置3个试验重复,嫁接成活稳定后调查成活率及统计分析。结果表明:不同无性系间嫁接成活率差异显著,嫁接时间及无性系与嫁接时间交互作用达极显著水平。39个无性系中,其嫁接成活率最高达77.667%、最低值为9.167%;5月份较1月份更适合腾冲红花油茶嫁接;不同无性系与时间交互极显著,最高组合成活率达85.67%,最低值仅7.33%。     

树木-水稻农林系统中害虫的侵害

本文比较研究了10种水稻害虫在3个树种(Akashmoni,Jhau和Albida)与稻子混栽的农-林复合生态系统中的发生情况,通过3个树种的冠幅大小、透光率以及害虫发生程度相比较,提出农-林复合生态系统中,水稻害虫的发生与树冠的透光率呈密切的负相关关系。     

河流廊道绿带结构的温湿效应

选择北京北五环清河两侧不同结构类型(内部构成、郁闭度)的绿地作为研究对象,利用小尺度定量测定的技术方法,分析城市河流廊道绿地不同内部构成、不同郁闭度与温湿效应的关系,为河流廊道绿带建设提供科学依据.结果显示:1)温湿影响效应大小为乔-灌-草型＞乔-草型＞灌-草型＞草坪.当绿地内部构成为草坪时,降温增湿效应不明显;当绿地内部构成为灌-草型时,其降温增湿效应较明显;当绿地内部构成为乔-草型和乔-灌-草型时,其降温增湿效果明显.2)绿地的降温增湿效果,随着郁闭度的不断增加而逐渐增强.当绿地郁闭度为0.20～0.40时,绿地具有一定的降温增湿效应,但效应不明显;当绿地郁闭度大于0.40时,绿地降温效应明显;当绿地郁闭度超过0.60时,绿地增湿效应极其明显且趋于稳定.     

Plant Resources of the Traditional Homegardens in Bangladesh

Abstract

A vegetation survey in four regions (Deltaic, Dryland, Hilly and Plain) in Bangladesh was conducted over a period of 10 months from July 1992 to April 1993. Eighty homegardens (20 from each of the four regions) were assessed in terms of composition, dominance and uses of the perennial species. In total ninety-two perennial species were recorded for the set of 80 homegardens surveyed. From gardens in the Deltaic region 67 species were recorded. Corresponding figures were 56 for the Plain region, 54 for the Hilly region and 46 for the Dryland region. Species composition pattern indicated higher proportion of food and fruit producing species and the first five dominant species with the highest relative importance values were the fruit trees. Eight major uses of the homegarden plants were recorded.     

14C Allocation in tree-soil systems

We studied whole-tree C allocation with special emphasis on the quantification of C allocation to roots and root respiration. To document seasonal patterns of C allocation, 2-year-old hybrid poplar trees greater than 3 m tall were labeled with (14)CO(2) in a large Plexiglas chamber in the field, in July and September. Climate and CO(2) concentration were controlled to track ambient conditions during labeling. Individual tree canopy CO(2) assimilation averaged 3.8 micromol CO(2) m(-2) s(-1) (12.9 g C day(-1) tree(-1)) in July and 6.2 micromol CO(2) m(-2) s(-1) (9.8 g C day(-1) tree(-1)) in September. Aboveground dark respiration was 12% of net daytime C fixation in July and 15% in September. Specific activity of root-soil respiration peaked 2 days after labeling and stabilized to less than 5% of maximum 2 weeks later. Low specific activity of root-soil respiration and a labeled pool of root C demonstrated that current photosynthate was the primary source of C for root growth and maintenance during the growing season. Root respiration averaged 20% of total soil respiration in both July and September based on the proportion of labeled C respired to labeled C fixed. In July, 80% of the recovered (14)C was found above ground and closely resembled the weight distribution of the growing shoot. By September, 51% of the recovered (14)C was in the root system and closely resembled the weight distribution of different size classes of roots. The finding that the distribution of biomass and (14)C were similar verified that the C introduced during labeling followed normal seasonal translocation pathways. Results are compared to smaller scale labeling studies and the suitability of the approach for studying long-term C fluxes is discussed.     

白梭梭同化枝对干旱胁迫的生理生态响应

对白梭梭同化枝自然水分胁迫下的季节抗旱特征进行研究。结果表明:自然干旱胁迫条件下,不同生长发育时期同化枝的主导抗旱生理因子不同。5月31日至6月29日盛花期间,同化枝内源ABA含量甚微,气孔导度值与光合强度处于生长发育过程的最高水平,可溶性糖含量呈现下降趋势,而脯氨酸含量略有增加,植物通过渗透调节作用适应此阶段轻度干旱胁迫;6月29日至7月26日盛夏期间,ABA迅速积累,气孔导度值降为生长发育过程的最低值,叶绿素分解,可溶性糖与脯氨酸均呈现快速积累趋势,且可溶性糖积累强度大于脯氨酸;8月9日至8月22日同化枝生长发育后期,ABA急剧积累为生长发育过程的最高浓度,气孔导度值有所增大,脯氨酸和可溶性糖保持在高水平平稳变化。此阶段高浓度ABA调节植物生理过程适应干旱的效应受CTK、IAA两种内源激素的抑制,进而抑制脯氨酸和可溶性糖的继续积累。     

伯乐树1年生幼苗的光响应特征

采用自然全光照的16.72%(s17)、24.51%(s25)、36.49%(s36)和100%(s100)及林地下14.02%(s14)等5种光照强度,比较分析不同光照条件下的环境因子日变化、1年生幼苗成活率、生长量等指标,以期揭示幼苗对于夏季不同光照条件的光响应特征。结果表明:不同光照强度下,环境因子日变化显著不同,幼苗的成活率、形态和生理指标等均存在显著差异。极度弱光下(s17)幼苗生长迟缓;而全光照环境(s100)和较强光照下(s36)易造成幼苗的死亡;仅适度遮荫(s25)适于幼苗的生长;林下栽培(s14)的相对光照强度虽然较弱,但其各种小气候因子均明显优于无林地的其它光照条件,幼苗成活率、水分利用和平均净光合速率等指标均达到最优。建议抚育幼苗时应采用适宜的遮荫处理,可选择在中等郁闭度的林下(自然遮荫)或在大田中采用夏季单层遮荫。