Low- to moderate-severity historical fires promoted high tree growth in a boreal Scots pine forest of Norway

Abstract

Fire is the most important ecological factor governing boreal forest stand dynamics. In low- to moderate-severity fires, the post-fire growth of the surviving trees varies according to fire frequency, intensity and site factors. Little is known about the growth responses of Scots pine (Pinus sylvestris L.) following fires in boreal forests. We quantified changes in tree growth in the years following 61 historical forest fires (between 1210 and 1866) in tree-ring series collected from fire-scarred Scots pine trees, snags and stumps in Trillemarka nature reserve in south-central Norway. Basal area increment 10 years pre-, 5 years post-, and 11–20 years post-fire were calculated for 439 fire scars in 225 wood samples. We found a slight temporary growth reduction 5 years post-fire followed by a marked growth increase 11–20 years post-fire. Beyond 20 years post-fire, the long-term tree growth declined steadily up to approximately 120 years. Our results indicate that recurring fires maintained high tree growth in remnant Scots pines, most probably due to a reduction in tree density and thus decreased competition.     

基蘖肥氮不同比例对直播早稻群体动态、氮素吸收利用及产量形成的影响

以常规籼稻为供试材料,通过不同的基蘖肥用量处理研究了前中期氮(N)肥分配对直播早稻群体特征、N素吸收利用、产量形成以及经济效益的影响。结果表明:相同落谷量、总N量和穗肥N量下,基肥用量增加降低了出苗率和前期分蘖速度,最高分蘖数和有效穗数在N肥用量不足或过高时表现为随基肥用量的增加而降低,适宜施N量下则表现为先升后降的趋势;基肥用量增加降低了水稻生育后期功能叶的叶片含N量和叶面积指数,从而降低了水稻成熟期的植株N积累量以及穗部的N分配系数,N农学效率和N回收效率明显降低,N素转运率与基肥用量则存在着二次曲线关系;增加基肥用量使产量降低,净收益下降。本实验条件下,施N量为180 kg/hm2,基肥-蘖肥-穗肥的比例为35-40-25时,直播早稻的产量和经济收益最佳。     

追肥方式对温室滴灌番茄产量和水分利用效率的影响

通过2年的温室小区番茄栽培试验,研究了覆膜滴灌条件下滴灌追肥和刨穴追肥对番茄土壤水分利用率和产量的影响。结果表明,不同追肥方式对番茄产量有较大影响,滴灌追肥可以显著地增加番茄产量、提高水分利用效率。并从田间土壤水分时空变化、土壤养分有效性方面分析了引起差异的可能原因。     

Effect of slope and plant cover on run‐off,soil loss and water use efficiency of natural veld

Abstract

Run‐off and soil loss were monitored from a climax, subclimax and pioneer veld, each on a 5,9%, 4,1% and 2,1% slope, by means of a rainfall simulator on a Valsrivier soil form. With rainfall intensity, soil moisture content at the beginning of each rain storm, and soil texture the same for each treatment, plant cover and composition had a significant (positive) (P≤0,05) influence on the amount of soil loss and run‐off that occurred, as against the insignificant influence of the slope.

An average of 6,2 t/ha soil loss and 80,6% run‐off of the amount of water applied occurred from the pioneer veld (0,7% basal cover) on the steepest slope. In all the successional stages more run‐off and less soil loss occurred from wet soil than from dry soil. Significant (P≤0,01) relationships between basal and canopy cover were obtained with run‐off and soil loss.

The climax, subclimax and pioneer veld produced on average 0,57 g, 0,23 g and 0,07 g aboveground phytomass for each litre of water evapotranspirated.     

Microorganisms as driving factors for the community structure of testate amoebae along an altitudinal transect in tropical mountain rain forests

We investigated microbial biomass, fungal biomass and microbial community structure at three altitudes (1000, 2000 and 3000 m) and in two soil layers [L/F layer (Layer I) and underlying H/Ah layer (Layer II)] of tropical mountain rain forests in southern Ecuador. Basal respiration, microbial biomass and concentration of ergosterol generally declined from Layer I to Layer II and peaked at 2000 m. Compared to temperate forest ecosystems microbial biomass and ergosterol concentrations were generally low. Patterns in phospholipid fatty acids indicated that the composition of microbial communities markedly changed from Layer I to Layer II. These differences between layers decreased with increasing altitude. The concentration of the arbuscular mycorrhizal fungal marker PLFA 16:1ω5c decreased with altitude in Layer I but increased in Layer II. The fungal-to-bacterial ratio increased with altitude and was higher in Layer I than in Layer II. Presumably, low microbial biomass in soils of tropical forest ecosystems is due to high temperature associated with high respiration but also low litter quality, with the latter declining with altitude. These conclusions are supported by the fact that at higher altitude the microbial community changed from a bacterial-dominated to a fungal-dominated system. CCA showed that microbial biomass correlated closely with density of a number of putatively bacterial feeding testate amoeba species including Corythion dubium Taranek, 1871, Euglypha cristata Leidy, 1879, Trigonopyxis arcula Penard, 1912, Tracheleuglypha dentata Deflandre, 1928 and Trinema lineare Penard, 1890. Ergosterol concentrations, but not the PLFA 18:2ω6c, strongly correlated with the putatively fungal feeding species Phryganella acropodia (Hertwig, Lesser, 1874) Hopkinson, 1909. Generally, parallel to microbial biomass and ergosterol concentrations the density of testate amoebae peaked at 2000 m. However, compared to microbial parameters changes in testate amoebae communities between two layers were less pronounced. The data suggest that density and community structure of testate amoebae are driven by the availability of food resources (bacteria and fungi) which at high altitude decrease with increasing moisture and decreasing pH.     

生态环境因子对白芨生长发育的影响

研究不同栽培基质、根外追肥、光照条件对白芨(Bletilla striata (Thunb.) Reichb. f.)生长发育的影响,确定适宜的栽培基质配比、根外追肥施用方案以及光照条件,为其科学的栽培方式提供理论依据。选用三年生白芨作为试验材料,通过引种驯化、基质配比、根外追肥、光照条件等处理下白芨各农艺性状和叶绿素含量进行测定及比较分析,开展白芨引种和规范化栽培技术研究。结果表明,白芨在基质配比为农田原土：白沙=2:2的条件下栽植,其生长状况仅次于营养土,但成本低,有利于适应大田栽培;叶面喷施KH2PO4溶液可促进白芨的生长发育,尤以浓度为2‰时效果最显著;适当的遮阴度有利于白芨的生长发育,但当遮阴度达到70%以上时,白芨群体花期、单株开花量明显低于其他处理,抑制了白芨繁殖器官的发育。     

药剂拌种对春油菜白粉病和茎象甲的防效及对油菜产量的影响

为明确不同药剂拌种对春油菜出苗率、病虫害防效及产量的影响, 本文在3种不同种植密度下, 针对春油菜白粉病、油菜茎象甲, 选择25 g/L咯菌腈FSC、600 g/L吡虫啉SC、30%噻虫嗪SC、600 g/L吡虫啉SC+25 g/L咯菌腈FSC、30%噻虫嗪SC+25 g/L咯菌腈FSC进行了拌种处理试验。结果表明, 各拌种处理对春油菜的出苗有一定的影响, 其中600 g/L吡虫啉SC、30%噻虫嗪SC、600 g/L吡虫啉SC+25 g/L咯菌腈FSC、30% 噻虫嗪SC+25 g/L咯菌腈FSC拌种对春油菜出苗的影响大于25 g/L咯菌腈FSC拌种; 600 g/L吡虫啉SC+25 g/L咯菌腈FSC、30%噻虫嗪SC+25 g/L咯菌腈FSC拌种对白粉病和茎象甲的防效均高于单剂拌种; 600 g/L吡虫啉SC+25 g/L咯菌腈FSC拌种, 对春油菜白粉病的最高防效可达59.3%, 30%噻虫嗪SC+25 g/L咯菌腈FSC拌种对油菜茎象甲最高防效可达69.2%。白粉病病情指数与春油菜种植密度呈正相关, 拌种防效随密度增加而降低, 综合产量分析, 最佳种植密度为28.5万～34.5万株/hm2。     

氯虫苯甲酰胺拌种对稻纵卷叶螟的防治效果及安全性评价

为减少水稻抽穗前田间稻纵卷叶螟的化学防治次数及用药量，降低对天敌的伤害及农药残留，最终实现稻纵卷叶螟的简约化防控，采用氯虫苯甲酰胺对水稻种子进行拌种处理，室内测定了药剂拌种对种子发芽的安全性，并结合不同栽培模式下的田间试验，评价了不同用量下氯虫苯甲酰胺拌种对稻纵卷叶螟的控制时长及保叶效果，明确了药剂拌种对天敌蜘蛛的影响及最终残留情况。结果表明:当氯虫苯甲酰胺按有效成分用量30~120 g/hm2拌种时，对种子的发芽率及出苗均无影响。直播稻模式下，氯虫苯甲酰胺按有效成分60 g/hm2拌种，播种后110 d，其保叶效果仍高达97.13%；旱育手栽秧模式下，氯虫苯甲酰胺按有效成分90 g/hm2拌种，播种后108 d保叶效果为82%以上，旱育机插秧模式下按有效成分90~120 g/hm2拌种，播种后90 d保叶效果仍在95%以上；3种模式下拌种处理的保叶效果及持效期均远优于常规喷雾防治。研究表明，利用氯虫苯甲酰胺对水稻种子进行拌种处理，可有效控制水稻前期及中期稻纵卷叶螟的为害，降低后期田间虫口基数，并且对田间天敌蜘蛛安全性高，同时在收获的稻谷中未检出氯虫苯甲酰胺残留(残留量低于定量限0.000 8 mg/kg)。在江苏省丘陵地区粳稻区应用氯虫苯甲酰胺拌种处理，可确保水稻直至抽穗初期无需再进行稻纵卷叶螟的防治，并可显著减少后期稻纵卷叶螟虫源基数，实现稻纵卷叶螟的简约化防治。     

Preparation of Alginate-Based Biomaterials and Their Applications in Biomedicine

Alginates are naturally occurring polysaccharides extracted from brown marine algae and bacteria. Being biocompatible, biodegradable, non-toxic and easy to gel, alginates can be processed into various forms, such as hydrogels, microspheres, fibers and sponges, and have been widely applied in biomedical field. The present review provides an overview of the properties and processing methods of alginates, as well as their applications in wound healing, tissue repair and drug delivery in recent years.     

不同药剂拌种对小麦茎基腐病的初步研究

小麦是我国的主要粮食作物之一,由于常年秸秆还田及连作,造成小麦茎基腐病病菌有加重趋势,本文选用不同的杀菌剂进行小麦拌种,通过在小麦返青期、灌浆期、成熟期的调查,表明用6%立克秀悬浮种衣剂进行拌种防治小麦茎基腐病效果最好。