内蒙古大兴安岭北部原始林区森林火灾应急资源储备与调度研究

【目的】为更好地开展原始林区森林灭火工作,保护内蒙古大兴安岭北部原始林区森林生态资源。【方法】对内蒙古大兴安岭重点国有林管理局下辖的22个林业局,3个自然保护区的应急资源储备情况进行了整理,同时对北部原始林区森林火灾发生的时间规律和空间规律分别进行了分析,在此基础上采用ArcGIS软件,对内蒙古大兴安岭重点国有林管理局森林火灾应急资源的空间分布状况与内蒙古大兴安岭北部原始林区近5年森林火灾发生的空间分布状况进行了叠加分析,依据叠加分析的结果对内蒙古大兴安岭重点国有林管理局森林火灾应急资源空间分布的合理性进行了评判。【结果】叠加分析结果显示,目前内蒙古大兴安岭北部原始林区周边林业局森林火灾应急资源空间配置存在区域集聚以及北部原始林区附近应急资源配置不足等不合理问题。在对内蒙古大兴安岭重点国有林管理局森林火灾应急资源储备情况整理分析的基础上,创新性地提出了以应急物流系统所需时间最少和费用最小为目标进行优化的森林火灾应急资源分配模型。【结论】最后通过实例证明,该模型可以优化森林火灾应急物流系统中资源配置体系,为应急资源的合理调配提供了指导,对于实现科学决策指挥,保护北部原始林区森林生态资源具有一定的现实意义。     

采伐干扰下次生林灌木层主要树种的生态位动态

为探讨采伐干扰下的灌木层主要树种的生态适应性,用Levins、Schoener和Pianka等生态位测度公式定量分析闽北天然次生林采伐后灌木层主要树种生态位动态。结果表明:样地中黄绒润楠和刺毛杜鹃的生态位最大,属优势树种;甜槠、石栎和映山红为衰退树种,在林分生产作业中需加以保护。采伐干扰促进了灌木层主要树种的生态位释放,各树种的生态位宽度在伐后10~15 a达到峰值,随后下降,伐后20 a接近于未采伐林的生态位;各树种弱度和中度择伐的生态位宽度值约占其生态位宽度总值的50%。生态位重叠值在伐后10 a最大,随后下降,到伐后20 a趋于稳定状态。因此灌木层主要树种生态位的最优期为伐后10~15 a,最佳采伐干扰强度为弱度和中度择伐。     

粤北地区食用菌产业及其循环经济发展概述

从食用菌种类及其分布、产值、食用菌企业、食用菌产业循环经济发展情况等方面介绍了粤北地区食用菌产业发展现状,总结食用菌产业发展中存在的问题,如菌种问题突出,品牌意识缺乏;食用菌产业标准化落后;产品质量参差不齐,食品质量安全无保障;资源浪费严重;精深加工不足等,并提出相应的对策。     

广东典型稻田系统磷素径流流失特征

选择位于广东省增城、清远和高州地区的3个稻田试验点，于2008-2012年对稻田磷径流损失进行动态监测。结果表明，稻田径流事件主要发生在早稻季。常规施肥模式下稻田总磷径流浓度为0.02~1.56 mg·L^-1，11%~18%的径流样品总磷浓度超过地表水Ⅴ类水标准（0.4 mg·L^-1），施磷后14 d内降雨易导致稻田不同形态磷浓度出现峰值，具有一定环境污染风险。施磷不同程度增加稻田可溶性总磷径流负荷，对颗粒磷和总磷流失负荷无规律性影响。稻田磷径流负荷时空变化较大，常规施肥条件下可溶性总磷、颗粒磷、总磷年径流负荷分别为0.63~4.05、0.33~2.91、1.10~6.68 kg·hm^-2。本地区稻田磷流失系数为0.06%~6.81%，可溶性总磷是稻田磷径流流失主要形态。施肥量和降雨、径流量是影响本地区稻田磷径流损失的主要因子。     

Application of molybdenum fertilizer enhanced quality and production of alfalfa in northern China under non-irrigated conditions

Molybdenum (Mo) is an essential micro-mineral nutrient for plant growth and development. As an important legume forage, alfalfa (Medicago sativa) is frequently planted in marginal lands of northern China where water scarcity and infertile soil are limiting factors for alfalfa production. Mo plays an important role in nitrogen (N) metabolism in general and N fixation in legume species in particular. To evaluate the role of Mo fertilizer in alfalfa quality and production in semi-arid areas of northern China, we conducted a three-year field experiment in Inner Mongolia from 2012 to 2014. Mo fertilizer at the doses of 0, 150 g hm^?2, 300 g hm^?2yr^?1 was applied consecutively across the three years. Application of Mo at 300 g hm^?2yr^?1 significantly increased dry yield of alfalfa in 2014. Crude protein (CP) content of alfalfa without application of Mo exhibited a decline trend from 2012 to 2014. Application of Mo significantly enhanced total CP in 2012 and 2014, and delayed the reduction in total CP across the three years. In contrast to CP, Mo fertilizer had no significant effects on neutral detergent fiber and acid detergent fiber content. In addition, we found that nitrate reductase activity of alfalfa was increased by Mo fertilizer, which may account for the enhanced CP content in alfalfa. These findings highlight that application of Mo fertilizer can be an effective way to improve alfalfa production and quality in semi-arid areas in northern China.     

基于Meta-analysis的中国北方地区免耕玉米产量效应研究

【目的】定量分析免耕对中国北方地区玉米产量的时空效应和影响机制,为该地区免耕的科学应用和推广提供依据。【方法】以中国北方为研究区域,以传统耕作为对照,通过检索文献整合已发表的相关田间试验数据(截止2017年4月共获得68篇文献和82组试验数据,将数据按照区域(东北、华北和西北)、年降水量(500 mm和≥500 mm)、年均气温(10℃和≥10℃)、耕作模式(平作和垄作)、种植制度(连作和轮作)、是否秸秆还田、试验年份(2000年之前、2000—2009年和2010年之后)和免耕持续年限(1—2 a、3—5 a、6—9 a和≥10 a)进行分组),利用Meta-analysis方法系统探究免耕对玉米产量的时空效应与影响因素。具体分析过程包括异质性检验、综合效应量计算、发表偏倚检验、敏感性分析、累积Meta-analysis和亚组分析(影响因素分析)。【结果】与传统耕作相比,免耕总体上可显著提高玉米产量,平均增产率为3.1%(置信区间0.7%—5.5%,数据不存在发表偏倚和极端值)。2000年之前,免耕的累积增产效应不稳定(平均-0.7%—6.6%);2000年之后,免耕与传统耕作的累积产量差异逐渐由不显著变为显著。在东北地区,免耕表现出显著的增产效应(平均5.3%,置信区间1.5%—9.2%);而在华北和西北地区,免耕的增产效应不显著,分别为-2.6%—6.4%和-1.0%—6.4%。在年降水量500 mm、年均气温10℃的地区和轮作、秸秆还田条件下,免耕的增产率显著提高,平均分别为5.4%(置信区间1.7%—9.1%)、3.8%(置信区间0.8%—6.7%)、4.4%(置信区间1.3%—7.5%)和3.3%(置信区间0.8%—5.8%)。平作和垄作下,免耕的增产效应均不显著。2010年之后,免耕的增产效应显著提高(平均6.1%),且变幅较小(2.5%—9.7%)。随着免耕持续年限的延长,玉米增产率呈先增加后降低的趋势,当持续3—5 a时,免耕的增产效应显著且达到峰值(平均3.8%,置信区间1.6%—6.0%)。【结论】在年降水量较少或年均气温较低的区域,轮作或秸秆还田条件下,有利于发挥免耕的增产效应;东北地区较华北和西北地区更适宜免耕;3—5 a为较合理的免耕持续年限。     

Genetic differentiation in populations of Exserohilum turcicum from maize and sorghum in South Africa

Exserohilum turcicum is the causal agent of northern leaf blight, a devastating foliar disease of maize and sorghum. Specificity of E. turcicum to either maize or sorghum has been observed previously, but molecular evidence supporting host specialization is lacking. The aim of this study was to compare the genetic structure of E. turcicum isolates collected from adjacent maize and sorghum fields in Delmas and Greytown in South Africa. In addition, the mode of reproduction of this pathogen was investigated. Isolates from maize (N = 62) and sorghum (N = 64) were screened with 12 microsatellite markers as well as a multiplex mating type PCR assay. No shared haplotypes were observed between isolates from different hosts, although shared haplotypes were detected between isolates from maize from Delmas and Greytown. Population structure and principal coordinate analyses revealed genetic differentiation between E. turcicum isolates from maize and sorghum. Analysis of molecular variance indicated higher among‐population variation when comparing populations from different hosts, than comparing populations from different locations. Lack of shared haplotypes, high proportion of private alleles, greater among‐population variance between hosts than locations and significant pairwise population differentiation indicates genetic separation between isolates from maize and sorghum. The high haplotypic diversity in combination with unequal mating type ratios and significant linkage equilibrium indicates that both sexual and asexual reproduction contributes to the population genetic structure of E. turcicum in South Africa.     

气候变化对中国水稻生产的影响研究进展

水稻生产系统是响应气候变化最敏感的农业生态系统之一,本文综述了当前和未来气候变化对我国水稻生产的影响。气候变化背景下,我国水稻生长季的热量资源增多,辐射资源减少,降水不均一性加大。高温热害、干旱、暴雨和洪涝灾害发生更频繁,这可能降低水、热资源的有效性。气候变化使我国单季稻和双季稻潜在种植边界显著北移,导致单季稻、早稻和晚稻的主要生育期缩短。基于统计模型和水稻生长模型的研究结果表明,如果不考虑品种改良和栽培技术的进步,气候变化使单季稻、早稻和晚稻产量下降,但不同稻作区和方法间存在差异。我国水稻生产重心北移、实测生育期延长和产量增加的变化趋势,反映了水稻生产系统通过种植分布调整、品种改良和技术改进来适应气候变化的能力。未来气候变化将进一步导致水稻生育期缩短和产量下降,对我国水稻生产和粮食安全带来严峻挑战。仍需加强气候变化影响机制的研究及其在影响评估中的应用,减小影响评估的不确定性并增加其系统性,为制定有效的应对策略提供可靠的理论支持。     

兴宁市优质稻高产品种种植示范及其配套技术

近几年来兴宁市积极推广优质稻的生产,种植面积逐年增加。结合兴宁市优质稻栽培实践,总结了目前的示范推广情况,最后提出了配套的技术要点。     

Beaver dams,streamflow complexity,and the distribution of a rare minnow,Lepidomeda copei

Freshwater fishes are threatened globally, and often too little is known about threatened species to effectively guide their conservation. Habitat complexity is linked to fish species diversity and persistence, and degraded streams often lack habitat complexity. Beaver Castor spp., in turn, have been used to restore streams and increase habitat complexity. The northern leatherside chub Lepidomeda copei is a rare, small‐bodied, drift‐feeding minnow that has anecdotally been observed to use complex habitats associated with beaver dams in the western United States. To investigate this anecdote, we conducted fish and habitat surveys, the latter focusing on quantifying habitat complexity, in a sub‐basin of the Upper Snake River Basin in the USA. Complementary generalised linear model and path analyses revealed that northern leatherside chub occurred more often at sites with complex streamflows, and streamflows were more complex when beaver dams were present and pools were deeper. Northern leatherside chubs were also more likely to occur when temperatures were warmer, aquatic macrophytes were abundant and stream channels were narrow and deep. The linkage between chubs, complex streamflows and beaver dams needs to be evaluated more broadly to completely understand its role in the rangewide status of the species. However, it does suggests that increased use of beaver reintroductions and dam analogues for stream restoration could be a boon for the northern leatherside chub, but such efforts should be monitored to determine their effectiveness to help adapt beaver‐based restoration approaches to best benefit the species.