Long-term partial cutting impacts on Desmognathus salamander abundance in West Virginia headwater streams     

Kurtis R. Moseley  W. Mark Ford  John W. Edwards  Thomas M. Schuler 《Forest Ecology and Management》2008

To understand long-term impacts of partial cutting practices on stream-dwelling salamanders in the central Appalachians, we examined pooled abundance of Desmognathus fuscus and D. monticola salamanders (hereafter Desmognathus) in headwater streams located within long-term silvicultural research compartments on the Fernow Experimental Forest, Tucker County, West Virginia. We sampled Desmognathus salamanders in 12 headwater streams within silvicultural research compartments that have been subjected to partial cutting for approximately 50 years. We used an information-theoretic approach to test five a priori models explaining partial cutting effects at the compartment-level on Desmognathus abundance and eight a priori models explaining stream reach-scale habitat effects on Desmognathus abundance. Our modeling efforts resulted in the selection of two competing models explaining partial cutting effects on Desmognathus abundance at the compartment-level. The VOLUME model, which incorporated cumulative timber volume harvested within compartments, received the greatest support and indicated that Desmognathus abundance was impacted negatively by increased timber volume removal. The second model, LASTDISTURB, incorporating the single variable of time since last harvest activity, indicated that Desmognathus abundance increased with time since last harvest at the compartment-level. For stream reach-scale habitat variables, the EMBEDDED model incorporating the percent of embedded substrate within streams, received the strongest support for explaining Desmognathus abundance. Our results suggest that long-term partial cutting suppresses Desmognathus abundance, possibly by increasing stream sedimentation and thereby reducing available cover for juvenile and adult salamanders. However, these practices do not appear to have threatened long-term persistence of Desmognathus in central Appalachian headwater streams.  相似文献   

基于各粉路系统面粉和湿面筋含量快速确定面粉吸水率的初步研究     

曹颖妮  胡京枝  余大杰  张玲  郝学飞  赵光华  班宜辉  张正军 《麦类作物学报》2015,35(5):645-649

为准确预测小麦面团流变学特性测定过程中的吸水率,以河南省小麦区域试验参试品种(系)为材料,对各粉路系统出粉量、湿面筋含量、沉淀值和吸水率进行相关性分析.结果表明,各粉路面粉出粉量、湿面筋含量和沉淀值均与吸水率呈显著或极显著相关.以各粉路面粉出粉量为自变量(X),以吸水率为因变量(Y),进行逐步回归分析,建立方程Y=60.967-0.047X1-0.055X5 +0.006X6 +0.055X7.并以不同湿面筋含量对实验结果进行细分,初步总结出不同湿面筋含量所对应的吸水率大概值.  相似文献   

Comparative performance of recycling tunnel and conventional sprayers using standard and drift-mitigating nozzles in dwarf apple orchards     

L. Jamar  O. Mostade  B. Huyghebaert  O. Pigeon  M. Lateur 《Crop Protection》2010

The use of tunnel sprayers should be encouraged because they can potentially reduce pesticide input and drift in orchards. They could also allow smaller plot size in multifactorial trials in which fully randomized or randomized block designs are recommended. However, the effectiveness of plant protection products applied with tunnel sprayers cannot be reliably assessed without a thorough investigation into spray distribution in tree canopies. A set of three experiments was undertaken in an apple orchard to compare a new type of recycling tunnel sprayer with a standard axial fan sprayer, both of them fitted with either conventional hydraulic hollow cone nozzles (ATR) or drift-mitigating air induction cone nozzles (TVI). Its performance was assessed in terms of 1) spray deposit and coverage in the canopy, 2) sedimentation drift (spray drift to the ground) and 3) collection and recycling rate of the liquid sprayed in the tunnel. Artificial targets composed of cellulose papers and water-sensitive papers were used to evaluate the spray deposit and coverage at similar target positions for each treatment. A fluorescent dye was used as the spray tracer.  相似文献   

非参数投影寻踪回归在淤地坝坝地淤积预测中的应用     

陆克芬  刘延明  方崇 《安徽农业科学》2009,37(27):13382-13384

通过分析黄土高原淤地坝淤积量与相应次侵蚀性降雨指标的关系,提出了基于投影寻踪回归分析的淤地坝泥沙淤积量预测模型,利用实测资料对淤地坝泥沙淤积量进行预测。结果表明,该模型具有较高的拟合度和预测精度。  相似文献   

Efficacy of riparian buffers in mitigating local population declines and the effects of even-aged timber harvest on larval salamanders     

William E. Peterman  Raymond D. Semlitsch 《Forest Ecology and Management》2009

Headwater streams are an important and prevalent feature of the eastern North American landscape. These streams provide a wealth of ecosystem services and support tremendous biological diversity, which is predominated by salamanders in the Appalachian region. Salamanders are ubiquitous throughout the region, contributing a significant biomass that supports ecological and ecosystem processes. One of the greatest threats to salamanders is loss of headwater-riparian habitat through timber harvest. In this study, we measured larval salamander abundance at five headwater streams with different riparian buffer widths retained following logging. By sampling larval salamanders using leaf litter bags, we assessed the impacts of even-aged timber harvest on aquatic larval salamander abundances, where it was found that larvae are negatively impacted by increased stream sedimentation and a decrease in riparian buffer width. We found that retention of a 9-m buffer was effectively no different than complete removal of all riparian forest, and as such, current regulations to protect headwater streams are ineffectual. Furthermore, no significant differences were observed between the 30 m buffer treatment and uncut control treatments suggesting that a 30 m or larger riparian buffer may assuage the in-stream effects of riparian timber harvest. Management guidelines for Appalachian forests should be revised to accommodate the biology of plethodontid salamanders.  相似文献   

Sediment deposition in streams adjacent to upland clearcuts and partially harvested riparian buffers in boreal forest catchments     

David Kreutzweiser  Scott Capell  Kevin Good  Stephen Holmes 《Forest Ecology and Management》2009,258(7):1578-1585

The rates of fine sediment deposition were compared among three logged and three reference stream reaches 2–3 years before and 3–4 years after logging to assess the environmental impacts of partial harvesting as a novel riparian management strategy for boreal forest streams. The partial-harvest logging resulted in 10, 21 and 28% average basal area removal from riparian buffers at the three logged sites, adjacent to upland clearcut areas. No significant differences from pre-logging or reference-site sedimentation patterns were detected for two of the three logged sites. At the site with the most intense riparian logging (WR2), significant increases of 3–5 times higher than pre-logging or reference levels were detected in fine inorganic sediment (250–1000 μm) load and accumulation in the first year after logging, but no significant change was detected in fine organic sediments or very fine sediments (0.5–250 μm). The increased inorganic sediment deposition at WR2 was temporary with no significant differences from reference or pre-logging levels detectable by summer of the second post-logging year. Logging impacts on fine sedimentation in streams appeared to have been mitigated by careful logging practices including winter harvesting in riparian areas to reduce ground disturbance, and a tendency to avoid immediate (within 3–5 m) stream-side areas. Where it is feasible and advisable to conduct partial harvesting in riparian buffers of boreal forest streams, the logging can be conducted without posing significant risk of increased sediment inputs to streams when careful logging practices are followed.  相似文献   

Assessment of suspended solids dynamics and their effect in the irrigation networks in the Northern Jordan Valley     

Nassim Al-Abed  Fayez Abdulla  Ra’ed Zahrawi 《Irrigation and Drainage Systems》2007,21(1):45-59

This study aims to assess the suspended solids dynamics of the irrigation water, through total Suspended Solids (TSS) measures and field observations. Assessment is conducted along the distribution system in the Northern Jordan Valley. This study followed the water’s TSS conditions in the study area along its travel in King Abdullah Canal (KAC), in the pumping station (with all of its components) and in the delivery networks from the pumping station up to the farm units. TSS of the water in KAC fluctuates temporally and spatially. Pumping stations components performance with respect to TSS such as the bar rack, the static and the traveling screens, the settling basins and the well were evaluated. The design of settling basins showed acceptable specifications of the existing structure; however, management and operation conditions are the main concerns affecting their performance. This study showed the screens work with low efficiency because of operation faults and lack of maintenance especially for the traveling screen. Distribution network affects adversely the water’s TSS because of lack of flushing which enables sediments removal from the network, and prevents suspension process for the piled up sediments inside the network pipes. This study suggested using special points of low elevations in the network to flush piled up sediment out of the network. Finally, this study showed the flushing procedure the Jordan Valley Authority staff should take for cleaning the distribution network.  相似文献   

Prototype Testing of the Appurtenance for Settleable Solids In-raceway SeparaTion (ASSIST)     

Kevin B. Wong  Raul H. Piedrahita   《Aquacultural Engineering》2003,27(4):273-293

The most common type of rearing unit for rainbow trout produced in the US is the flow-through raceway. A water treatment structure, which can be readily retrofitted into existing raceways, was designed to create rotational currents to aid in the concentration and collection of particulate waste material in situ. The designed structure, referred to as the Appurtenance for Settleable Solids In-raceway SeparaTion (ASSIST), incorporated a drain line which diverts a small fraction of the raceway flow to continuously remove the uneaten feed and fecal material from the collection area located at the effluent end of the raceway. Continuous removal of the collected particulates minimizes the leaching of soluble material from the solids into the water column. Based on scale model tests using analogous waste material, the ASSIST is expected to remove 40–50% of the settleable solids generated in commercial rainbow trout aquaculture while diverting 5–10% of the raceway flow.  相似文献   

不埋式弹性基础薄板在集中荷载作用下的设计理论和基地强夯法的若干向题     

邓寿昌  吴震东 《湖南农业大学学报(自然科学版)》1989,(4)

本文对不埋式弹性基础薄板由文克勒假定所得微分方程的解答,提出M(x)之影响范围,从而推导出单向配筋时弹性基础薄板在集中荷载作用下一整套弯矩叠加计算公式,简化了弯矩的计算,并有足够的精确度,并对强夯法加固地基施工中综合论述了几个重要参数的选择,提出了自己的看法和若干应注意的问题。  相似文献   

小麦沉淀值的贮存稳定性研究初报          下载免费PDF全文

刘三才朱志华  张晓芳李为喜  刘方李燕 《麦类作物学报》2005,25(2):122-124

为了了解小麦在不同保存条件下沉淀值的变化特点,采用Zeleny分析法对京411、中优9844和Salgemma等三个小麦品种,在室温、室温 干燥器和低温等三种不同保存条件下做9个处理,分别进行了不同保存时间沉淀值的分析。结果表明,随着保存时间的延长,小麦沉淀值呈现明显的下降趋势,保存52周后平均下降了15.8%～21.9%;三种不同保存条件以低温保存效果最好,室温则较差。沉淀值的稳定性也表现出一定的品种效应。  相似文献