Trophic consequences of postfire logging in a wolf–ungulate system

Controversy surrounds postfire logging, often because of negative effects on snag-dependent wildlife species. Few studies, however, have examined effects on early-seral species that may benefit from postfire logging, nor effects on trophic relationships. We studied the effects of postfire logging on trophic dynamics between wolves (Canis lupus), three ungulate species and ungulate forage biomass during the first 3 years in a large burn in the Canadian Rockies, Alberta, Canada. We examined plant biomass and ungulate responses to two treatments (post- and prefire logging) compared to a burned but unlogged area (control). We evaluated resource selection for the three treatments by elk (Cervus elaphus) using radiotelemetry and for deer (Odocoileus spp.), moose (Alces alces), and, secondarily, elk using pellet counts. Elk resource selection was modeled as a function of the trade-off between wolf predation risk and herbaceous forage biomass to test for trophic impacts of postfire treatments. Postfire logging had transient effects on total herbaceous biomass; while forb biomass was reduced, increases in graminoid biomass more than compensated by the third year. Prefire logging areas were dominated by a few species, but had generally higher forage biomass by the third year. Ungulates avoided postfire and prefire logged areas despite greater herbaceous biomass. Only when we considered elk resource selection as a function of both forage and wolf predation risk was the extent to which trophic interactions affected by postfire logging revealed. Wolves selected proximity to roads and the higher forage biomass associated with postfire logging in open logged areas. This translated to the highest predation risk for elk in postfire logged areas. Thus, ungulates avoided postfire logged areas because of human alteration of top-down predation risk despite enhancements to bottom-up forage biomass. Managers should consider trophic consequences of postfire logging on the interactions among species when gauging logging effects on terrestrial ecosystems. Making use of existing roads, minimizing the construction of new roads, and managing road removal following postfire logging will help mitigate the negative effects of postfire logging on terrestrial ecosystems.     

云南景东县豆科固氮树种及根瘤菌资源调查

对云南景东县豆科固氮树种进行调查采集与鉴定,确认并记录70种与相应的根瘤菌(菌株)共生的豆科固氮树种.其中,云实亚科1属1种,含羞草亚科6属20种,蝶形花亚科23属49种.根瘤大小不一,形状各异,有球形、椭圆形、棒状、珊瑚状;表面颜色有浅黄色、棕黑色、棕色或黑色.对以活体保存的材料进行根瘤菌的分离、鉴定,获得并保存了分别与其中38种豆科树种相共生的根瘤菌菌株147株.调查表明,在景东县及云南南亚热带区域和热带区域,不仅拥有可供在多方面开发利用的豆科固氮树种,且具有丰富的可供科研和开发利用的根瘤菌资源.     

毕节地区植烟土壤肥力状况评价

2007～2008年对在毕节地区主要烟区采集的200个植烟土壤样品进行了土壤养分含量分析,结果表明:植烟土壤的有机质含量平均在27.70 g/kg,总体上处于适宜水平;pH值以偏酸性或中性为主;有效氮含量偏高;速效磷含量偏低;速效钾含量整体丰富,平均为158.42 mg/kg;土壤水溶性氯含量整体适宜。此外,针对土壤养分含量状况,提出了一些相应的改良措施。     

芥蓝芥子油苷提取条件优化研究

采用正交试验设计,研究了提取温度、提取剂甲醇浓度(V/V)、提取时间和待测物质与提取液比例(简称“物液比”) 对芥蓝菜薹中芥子油苷(总芥子油苷含量、总脂肪族芥子油苷和总吲哚族芥子油苷)提取效果的影响。结果表明,物液比和提取温度对总芥子油苷、总脂肪族芥子油苷和总吲哚族芥子油苷提取效果影响显著(P<0.05),而甲醇浓度和提取时间对芥子油苷提取率无显著影响(P>0.05)。综合考虑提取效果和成本,芥蓝中芥子油苷最佳提取条件为75℃,物液比1∶45(g∶mL),甲醇浓度70%,提取时间5 min。在该条件下,总芥子油苷提取量为8.31 μmol/g DW,总脂肪族芥子油苷提取总量为7.58 μmol/g DW,总吲哚族脂肪族芥子油苷提取总量为0.73 μmol/g DW。     

Reducing tillage intensity affects the cumulative emergence dynamics of annual grass weeds in winter cereals

Annual grass weeds such as Apera spica‐venti and Vulpia myuros are promoted in non‐inversion tillage systems and winter cereal‐based crop rotations. Unsatisfactory weed control in these conditions is often associated with a poor understanding of the emergence pattern of these weed species. The aim of this study was to investigate, understand and model the cumulative emergence patterns of A. spica‐venti, V. myuros and Poa annua in winter cereals grown in three primary tillage regimes: (i) mouldboard ploughing, (ii) pre‐sowing tine cultivation to 8–10 cm soil depth and (iii) direct drilling. Direct drilling delayed the cumulative emergence of A. spica‐venti and V. myuros (counted together) in contrast with ploughing, while the emergence pattern of P. annua was unaffected by the type of tillage system. The total density of emerged weed seedlings varied between the tillage systems and years with a higher total emergence seen under direct drilling, followed by pre‐sowing tine cultivation and ploughing. The emergence patterns of all species were differently influenced by the tillage systems, suggesting that under direct drilling, in which these species occur simultaneously, management interventions should first and foremost consider that A. spica‐venti and V. myuros emerge over a longer period to avoid control failures.     

Regional distribution and integrity of equine ovarian pre‐antral follicles

The goal of this study was to determine the distribution of pre‐antral follicles in the ovarian parenchyma of mares. For Experiment 1, each ovary was cut longitudinally at the greater curvature, performing two hemiovaries. After that, six fragments from each hemiovary were obtained, resulting in 12 fragments, which were divided into the innermost region of the parenchyma, the middle region and the outermost region. All the three obtained sections were cut transversally to obtain two fragments from each one. For Experiment 2, each ovary also submitted to a longitudinal cut on the greater curvature, forming two hemiovaries. Each hemiovary was sectioned into four symmetrical fragments, resulting in eight fragments per ovary. The fragments were related as being near to or far from the ovulatory fossa. The fragments of both experiments were immediately fixed in Carnoy for 12 hr and kept in 70% ethanol for 24 hr. Follicles were classified according to the stages of development and for morphological integrity according to oocyte morphology and granulosa cells. After the histological assessment, a total of 1,130 follicles were visualized from Experiment 1, being 1,054 (93.3%) primordial follicles and 76 (4.7%) follicles in development. The innermost region had the highest percentage of pre‐antral follicles compared to the other regions (p < .05). The middle and outermost regions showed higher percentages of intact primordial and developing follicles than the innermost region (p < .05). Considering Experiment 2, 938 follicles were found, being 894 (95.3%) primordial and 44 (4.7%) follicles in development. The region near the ovulatory fossa presented higher (58.7%; 551 of 938) follicular concentration compared to the region far from the ovulatory fossa (41.3%; 387 of 938; p < .05). As a conclusion, distribution of pre‐antral follicles in the equine ovary has a specific pattern through the parenchyma. Also, the follicular integrity differed in the studied ovarian areas.     

有机氮和无机氮配施对香料烟产值及上部叶品质的影响

在浙江绍兴烟区采用大田试验,研究了在等氮条件下,有机氮部分替代无机氮对香料烟产值及上部叶品质的影响。结果表明,在合适的有机氮和无机氮比例下,有利于香料烟的产量、产值及上等烟比例的提高,上部叶（A1）烟碱、总氮含量的减少,同时有利于上部烟叶总糖、还原糖、糖碱比、钾、氯、矿质元素的增加。对浙江绍兴烟区而言,有机氮和无机氮比例为50∶50时,香料烟产量、产值最高,上部烟叶的品质最好。     

祁连县小麦“3414”肥效试验

在中等肥力的地块进行小麦"3414"肥效试验,结果表明,该立地小麦最佳施肥量为纯N130.7kghm-2,P2O5131.1kghm-2,K2O60.0kghm-2。     

甜菜RAPD反应体系优化及亲缘关系研究

利用正交试验设计,从Mg~(2+)、dNTP、引物、Taq酶和模板5种因素5个水平上对甜菜RAPD反应体系进行优化,确立了适合甜菜RAPD反应体系:25μL反应体系中含1×Buffer、1.0 mmol/LMg~(2+)、1U Taq DNA聚合酶、0.25 mmol/LdNTP、0.4μmol/L随机引物和25 ngDNA模板。利用优化的RAPD反应体系对38个甜菜品种进行亲缘关系分析。结果表明,38个品种之间的多态性比较高,变异大。聚类图结果表明,38个甜菜品种遗传距离的变异范围在0.14～0.72。当以遗传距离0.50来划分时,可将38个品种分为两大类,以遗传距离0.40来划分时,又可以把第2大类分为6个亚类。结果显示,RAPD优化体系适合甜菜亲缘关系鉴定。     

高温胁迫对岷江百合幼苗耐热指数和理化特性的影响

为了探明岷江百合幼苗在高温胁迫下的生理反应,以离体扩繁的岷江百合幼苗为研究材料,对其进行了不同高温(37℃/30℃、42℃/37℃)和不同时间(0、4、8、16、32、48 h)处理,研究了高温胁迫对其耐热指数和有关生理生化指标(叶绿素、丙二醛、游离脯氨酸、可溶性蛋白含量和SOD活性)的影响.结果表明:随着温度的升高和处理时间的延长,植株的耐热指数不断下降,叶绿素含量减少,丙二醛(MDA)含量增加;42℃胁迫32 h后,游离脯氨酸、可溶性蛋白含量、SOD活性均达到最大值,分别比对照增加了0.66倍、1.77倍和9.78倍.但胁迫48 h后,指标显著下降,这说明,42℃间断胁迫48 h对植株产生了不可逆的的热伤害作用.