Seasonal Timing of Fire Alters Biomass and Species Composition of Northern Mixed Prairie

Fire plays a central role in influencing ecosystem patterns and processes. However, documentation of fire seasonality and plant community response is limited in semiarid grasslands. We evaluated aboveground biomass, cover, and frequency response to summer, fall, and spring fires and no fire on silty and clayey sites in semiarid, C₃-dominated grassland. The magnitude of change in biomass between years was greater than any differences among fire treatments. Still, differences existed among seasons of fire. Summer fire reduced non-native annual forb frequency (3% vs. 10% ± 2%) and Hesperostipa comata, reduced native annual forbs the first year, increased Poa secunda and bare ground, and increased Vulpia octoflora the second year. Fall fire increased grass biomass (1224 vs. 1058 ± 56 kg ? ha^? 1), but fall fire effects were generally similar to those of summer fire. Spring fire effects tended to be intermediate between no fire and summer and fall fire with the exception that spring fire was most detrimental to H. comata the first growing season and did not increase bare ground. All seasons of fire reduced litter, forb biomass, and frequency of Bromus japonicus and Artemisia spp., and they reduced H. comata, V. octoflora, and native annual forbs the first year, but increased basal cover of C₃ perennial grasses (2.2% vs. 0.6% ± 0.4%). Fire during any season increased dominance of native species compared with no fire (6.6% vs. 2.0% ± 1.0% basal cover) and maintained productivity. Seasonal timing of fire manipulated species composition, but increased C₃ perennial grass cover and native species dominance with fire during any season indicated that using fire was more important than the season in which it occurred. In addition, fire effects on the vegetation components tended to be counter to previously observed effects of grazing, suggesting fire and grazing may be complementary.     

Impact of push–pull cropping system on pest management and occurrence of ear rots and mycotoxin contamination of maize in western Kenya

Push–pull involves intercropping of cereals with Desmodium as a “push” crop and planting Napier grass/Brachiaria as the “pull” crop at the border. The technology has been reported to effectively control stemborers, striga weed, and fall armyworm (FAW), and to improve soil nutrition, resulting in increased grain yield. This study evaluated the impact of stemborer and FAW management using this technology on incidence of maize ear rots and preharvest contamination of grains with aflatoxin and fumonisin in western Kenya. The study was conducted during three cropping seasons on maize grown under the push–pull system and as a monocrop. Incidence of stemborer and FAW damage was determined as percentage of damaged plants, while incidence of ear rots was determined as percentage of ears with symptoms. At harvest, fungi were isolated from kernels and aflatoxin and fumonisin were quantified using enzyme-linked immunosorbent assay. Stemborer and FAW damage was significantly (p = .001) reduced by over 50% under the push–pull system. There was also a significant (p < .001) reduction in the incidence of Fusarium verticillioides (60%) and Aspergillus flavus (86%), which was reflected in a reduced incidence of ear rots (50%) with the push–pull system (p = .001). Fumonisin in maize from push-pull farms was significantly (p = .048) reduced (39%) but the technology had no significant (p > .05) effect on aflatoxin. The study showed that push–pull is an effective strategy for managing maize ear rots and fumonisins, and therefore could play a role in improving food safety among smallholder maize farmers in the region.     

Litter production,decomposition and nutrient mineralization dynamics of Ochlandra setigera: A rare bamboo species of Nilgiri Biosphere Reserve,India

Litter production, decomposition and nutrient release dynamics of Ochlandra setigera, a rare endemic bamboo species of Nilgiri biosphere were studied during 2011-2012 using the standard litter bag technique. Annual litter production was 1.981 t·ha-1 and was continuous throughout the year with monthly variations. Litterfall followed a triphasic pattern with two major peaks in November, 2011 and January, 2012 and a minor peak in July, 2011. The rate of decomposition in O. setigera was a good fit to the exponential decay model of Olson(1963). Litter quality and climatic conditions of the study site(maximum temperature, monthly rainfall and relative humidity) influenced the rate of decomposition. Nutrient release from the decomposing litter mass was in rank order N = Mg K = Ca P. Nutrient release from litter was continuous and it was in synchrony with growth of new culms. Study of litter dynamics is needed before introduction of a bamboo species into degraded or marginal lands or Agroforestry systems.     

森林凋落物分解研究进展

系统评述森林凋落物的分解过程、凋落物分解及养分释放的影响因素、分解研究的方法等.森林凋落物的分解既有物理过程,又有生物化学过程,一般由淋溶、自然粉碎、代谢作用等共同完成.凋落物分解过程先后出现分解速率较快和较慢2个阶段,元素迁移一般呈现淋溶-富集-释放的模式.凋落物分解主要受气候、凋落物性质、微生物和土壤动物的影响,气候是最基本的影响因素,常用实际蒸散(actual evapotranspiration简称AET)作为指标.凋落物分解速率呈明显的气候地带性,与温度、湿度等紧密相关.从全球尺度来讲,凋落物质量对分解速率的影响处于次要地位,但在同一气候带内因AET变化较小,则起了主导作用.N、P和木质素浓度、C/N、C/P、木质素与养分比值是常见的凋落物质量指标,其中C/N和木质素/N最能反映凋落物分解速率.凋落物化学性质对其分解的影响作用又与分解阶段有关.凋落叶中N、P、K初始浓度高使得初期分解较快,而后期分解放慢.土壤理化性质及微生物区系也将不同程度地影响凋落物分解.尼龙网袋法(litter bag method)操作简单,是野外测定森林凋落物分解速率最常用的方法.除此之外,缩微试验也得到了广泛应用.目前普遍采用的衡量凋落物分解速率大小的指标主要有CO2释放速率、凋落物分解系数(k值)及质量损失率.在此基础上提出了指数衰减、线性回归等模型来模拟凋落物分解过程.尽管对凋落物分解在森林生态系统C、N、P循环、土壤肥力维持等方面已进行了较深入的研究,但未来研究应侧重以下方向:长期的定位观测;采用相对统一的研究方法,获得可比性强的数据进行综合;深化凋落物分解机理研究;探讨全球气候变化对森林凋落物分解的影响;评价营林措施(如林分皆伐、造林、施石灰和肥料等)对凋落物分解与养分释放的调节作用.     

国外容器苗质量调控技术研究进展

近年来,由于造林重点由宜林地向困难立地转移,对苗木质量的要求也随之增高.文章系统总结近年来国外容器苗的质量调控技术及其对于我国困难立地植被恢复的重要意义,从指数施肥、秋季施肥、底部灌溉、短日照处理和夏季造林、修根技术、容器规格、冻藏和解冻等研究进展进行了论述总结.指数施肥的每次施肥量与植物生长节律和养分需求同步,施肥效果较优.秋季施肥能避免苗木的养分稀释效应,已被应用于很多树种.实施底部灌溉的植物生长不亚于上部灌溉的植物,而底部灌溉用水量少,氮肥淋溶小.夏季造林时,将正处于速生期的苗木进行短日照处理,诱导顶芽形成,促进根系发育,能提高苗木抗性和造林效果.苗木冻藏可使空气中自由态的水凝固成结晶态的冰,苗木感染病菌几率降低,因此冻藏成为针叶树种贮藏的标准方法.在当前研究热点的基础上,论文就未来研究方向进行展望.     

郑州地区不同秋眠级苜蓿品种的生产性能评价

引进15个不同秋眠级别的紫花苜蓿Medicago sativa品种,在郑州地区测定其生长第1年和第2年的鲜草产量、株高、叶茎比、营养成分等各项农艺性状指标,分析评价不同秋眠级别苜蓿品种的生产性能。结果表明：1）秋眠和半秋眠苜蓿的鲜草产量高于非秋眠苜蓿,每年刈割5次,所有品种第1茬＞第2茬＞第3茬＞第4茬＞第5茬。2）从产量和品质角度考虑, 秋眠级数为3的苜蓿王(Alfaking)、WL-324和秋眠级数为5的射手（Archer）最适合中原地区。因此郑州地区在苜蓿的育种和引种工作中,应主要考虑秋眠和半秋眠的高产品种的培育与引进。     

水稻立枯病与猝倒病的鉴别与防治

近几年,我国水稻立枯病与猝倒病愈来严重,了解水稻立枯病与猝倒病因,从病里上进行区别,总结猝倒病和立枯病的主要区别和防治方法,从不同角度治疗。     

球孢白僵菌400亿孢子／克防治美国白蛾药效试验

为解决当前美国白蛾在杨树上发生严重的问题,本研究以常用药剂灭幼脲25％悬浮剂为对照．在田间杨树上测试了2年球孢白僵菌400亿孢子／克可湿性粉剂在不同使用浓度下对美国白蛾的防治效果。结果表明,球孢白僵菌400亿孢子／克可湿性粉剂相对于灭幼脲25％悬浮剂表现出很好的防治效果,2年的防效均在90％以上。该试验结果为该药剂的产品登记以及为生产上选择适于防治美国白蛾的药剂种类提供了依据。     

橡胶不同品种对棒孢霉落叶病的抗性评价

对云南各主要植胶区采集、分离得到的7个橡胶树多主棒孢菌株进行致病性测定,获得强致病力菌株DF4。分别用菌丝体接种鉴定、分生孢子悬浮液接种鉴定和粗毒素接种鉴定相结合的方法,对云南植胶区的9个主栽橡胶品种进行抗病性评价。结果表明,不同接种体或不同接种方法获得的抗性评价结果大致相同,但是也存在一定的差异。     

不同秋眠级数苜蓿品种生物量特性的研究

对不同苜蓿品种的茎、叶及总生物量生长动态的研究表明,在一个生育期内,苜蓿的茎、叶及总生物量的动态变化符合逻辑斯蒂曲线。在该试验条件下,不同秋眠级数苜蓿品种的生物量积累潜力不同,中秋眠级数的苜蓿品种生物量积累的潜力最大,其次为低秋眠级数的苜蓿品种,高秋眠级数的苜蓿品种生物量积累的潜力最小;不同秋眠级数苜蓿品种对环境的敏感程度不同,高秋眠级数的苜蓿品种对环境的敏感程度大于低秋眠级数的苜蓿品种。