Freeze–thaw cycles on rock surfaces below the timberline in a montane zone: Field measurements in Kobugahara,Northern Ashio Mountains,Central Japan

Rock-surface temperatures were measured on a tor and a large block located below the timberline in the Kobugahara Highlands, an upland plateau composed of granodiorite in central Japan (36°N, E139°, 1300 m a.s.l.). Many blocks in the region originate from core stones distributed on the plateau, and there are several block streams in the valley bottoms. The tor is situated at the upper end of one of these block streams. The large block appears to have detached from another tor. The mean air temperature of the coldest month is − 4 °C. Rock-surface temperatures were recorded continually every 30 min from December 1, 2002 through December 13, 2004 by thermistor probes connected to miniature data loggers. The diurnal and the annual freeze–thaw cycles and effective freeze–thaw cycles were recorded at each site. The freezing index of rock-surface temperature showed a marked variability from year to year. In addition, differences in local conditions at observation sites within a given area greatly affected the rock-surface temperature. These are important considerations in relation to local weathering below the timberline.     

Soil microbial biomass and activity response to repeated drying-rewetting cycles along a soil fertility gradient modified by long-term fertilization management practices

The effects of repeated drying-rewetting (DRW) cycles on the microbial biomass and activity in soils taken from long-term field experiment plots with different fertilization (FERT) management practice histories were studied. We investigated the hypothesis that soil response to DRW cycles differs with soil fertility gradient modified by FERT management practices. The soils were incubated for 51 days, after exposure to either nine or three DRW cycles, or remaining at constant moisture content (CMC) at field capacity. We found that both DRW and FERT significantly affected soil properties including NH₄-N, NO₃-N, dissolved organic C (DOC), microbial biomass C (Cmic), basal soil respiration rate (BSR), urease activity (URE) and dehydrogenase activity (DHD). Except for NH₄-N and BSR, variation in the properties was largely explained by FERT, followed by DRW, and then their interaction. Irrespective of the soils' FERT treatment, repeated DRW cycles significantly raised the DOC and Cmic levels compared with CMC, and the DRW cycles also resulted in a significant decline in BSR and URE and increase in DHD, probably because the organisms were better-adapted to the drying and rewetting stresses. The variations in soil biological properties caused by DRW cycles showed a significantly negative relationship with the soil organic C content measured prior to the start of the DRW experiments, suggesting that soils with higher fertility are better able to maintain their original biological functions (i.e., have a higher functional stability) in response to DRW cycles.     

基于BP人工神经网络的冻土融沉系数预测方法研究

为促进人工冻结技术在地下工程地基处理中的推广应用，在综合分析人工冻土融沉系数影响因素的基础上，采用BP人工神经网络方法建立人工冻土融沉系数的预测模型。用南京地区典型土质淤泥质黏土、粉质黏土和粉砂的试验数据作为网络模型的学习训练样本和测试样本，对网络模型的预测结果与实测进行对比。结果表明，用人工神经网络方法预测人工冻土融沉系数，结果准确可靠，更接近于实际，是一种很好的预测人工冻土融沉系数的方法：     

基于地理信息系统的闽东南柑橘避冻分区及防冻措施研究

通过对福建省66个气象台站的纬度、海拔高度、距海岸线距离等因子与福建省东南部10年1遇极端最低气温之间进行相关和回归分析,研究地理因子对极端最低气温的影响,模拟出极端最低气温在福建省东南部的分布状态,从而确定闽东南柑橘避冻的气候分区,并进一步分析对柑橘防冻的措施;结果表明地理信息系统能很好的模拟闽东南柑橘避冻的气候分区特征,该特征为由东南向西北柑橘气候区划由最适宜种植区逐渐过渡到可能种植区,模拟结果中不存在柑橘不适宜种植区,在闽东南区内,极端最低气温与纬度基本上呈线性相关。     

互助农田渠道冻害原因及防治

分析了互助县农田渠道遭受冻害的原因，结果表明，因为在封冻季节进行冬灌和座低水灌溉，导致水渠产生冻胀损害，并提出了农田渠道防止遭受冻害的具体措施。     

Influence of crop management on eyespot development and infection cycles of winter wheat

Wheat was assessed at four crop growth stages for eyespot (anamorph Pseudocercosporella herpotrichoides, teleomorph Tapesia yallundae) in a series of field trials that studied the effects on disease frequency of five wheat management techniques (sowing date and density, nitrogen fertiliser dose and form, removal/burial of cereal straw). An equation expressing disease level as a function of degree-days was fitted to the observed disease levels. This equation was based on eyespot epidemiology and depended on two parameters illustrating the importance of the primary and the secondary infection cycles respectively. Cultural practices were classified according to the importance of their effects on disease, and these effects could be related to infection cycles and host plant architecture. Sowing date had the earliest and strongest effect; early sowing always increased disease frequency through the primary infection cycle, and its influence on the secondary cycle was variable. Disease frequency was increased by high plant density and/or a low shoot number per plant through primary infection; the secondary cycle was, however, decreased by a low shoot number per plant, which reduced late disease development at high plant density. High nitrogen doses increased disease levels and the severity of both infection cycles, but this effect was partly hidden by a simultaneous stimulation of tillering and thus an indirect decrease of disease incidence. When significant, ammonium (vs ammonium nitrate) fertiliser decreased eyespot levels and infection cycles whereas straw treatment (burial vs removal of straw from the previous cereal crop) had no effect.     

基于稀土氧化物示踪法探究冻融循环对黑土团聚体周转的影响

为区分土壤团聚体形成和破碎过程,阐明冻融循环对黑土土壤结构的影响,本文利用稀土氧化物（REOs）示踪技术,通过室内模拟实验,探究不同初始含水量（50 %田间持水量（T50） vs. 100 %田间持水量（T100））和冻融循环次数（0次、3次、6次、12次和20次）对团聚体粒径分布、平均质量直径（MWD）以及团聚体周转过程的影响。研究结果表明：同一初始含水量下,随着冻融循环次数的增加,MWD、>0.25 mm和<0.053 mm团聚体含量显著降低,0.25～0.053 mm团聚体含量显著增加（P < 0.05）。6次冻融循环后,T50处理下的MWD显著高于T100处理（P < 0.05）,5～2 mm和<0.25 mm团聚体含量无显著差异。除5～2 mm团聚体外,相邻粒级团聚体之间周转更为激烈;在同一冻融循环次数下,5～2 mm团聚体向0.25～0.053 mm团聚体的破碎量在T100处理下显著高于T50处理（P < 0.05）。冻融循环促进了>0.25 mm团聚体的破碎和＜0.053mm的团聚,表现为0.25-0.053mm团聚体的累积,该变化与土壤初始含水量无关。冻融循环过程中,MWD与各粒径团聚体相对形成量呈显著正相关,与其相对破碎量呈显著负相关（P < 0.05）。随着冻融循环次数的增加,各粒径团聚体周转时间显著增加（P < 0.05）。同一冻融循环次数下,>0.25 mm团聚体的周转时间高于<0.25 mm团聚体,T100处理下的团聚体周转时间显著高于T50处理（P < 0.05）。综上所述,冻融循环次数和土壤初始含水量通过影响团聚体形成和破碎过程改变土壤结构的稳定性。本研究结果可为进一步探究冻融循环下黑土土壤结构变化提供理论依据。     

黄河内蒙古河段冰凌研究与冰凌预报数据库系统的设计

在Ｗｉｎｄｏｗｓ操作平台上使用ＰｏｗｅｒＢｕｉｌｄｅrＶＢ编程语言设计黄河内蒙古河段冰凌研究与冰凌预报数据库系统的准则，功能及组成。该设计考虑了系统数据量大以及存储，查询等需求和系统升级的要求；系统具有数据间相互关系简单，层次少，能生成多种表格等特点。     

蔬菜冷冻贮藏营养成分变化的研究

对蔬菜冷冻贮藏营养成分变化的研究表明，随着冷冻贮藏时间的延长和温度的升高，蔬菜中４种维生素的损失率均不同程度地增加，损失规律基本一致。除杀菁瓠瓜外，低温处理使杀菁豇豆和未杀菁马齿苋中氨基酸态氮含量先升后降。低温处理有利于控制蔬菜中硝态氮的含量，但对可溶性总糖含量的影响却较小。     

Colonist farmers' perceptions of fertility and the frontier environment in eastern Amazonia

Colonists, unlike indigenous peoples, are often assumed tohave little knowledge of their environment. However, their perceptions of the environment and their knowledgeof natural resource systems have a significant impact on their farming practices. Farmers in the frontier regionof Marabá, Eastern Amazonia, understand nutrient cycling and the links between different components in farmingsystems. Diagrams drawn by farmers show very diversified systems, and farmers' knowledge of soilcharacteristics, including sub-surface features, and distribution in their localities is very detailed in comparison to pedologicalclassifications. However, knowledge about nutrient cycling is very uneven, even between farmers from the same area.Generally, farmers were found to have very detailed knowledge of environmental resources, but very patchyknowledge of processes and functions underlying systems, and this conforms to evolutionary models of ecologicalknowledge. Perceptions of change in soil fertility are related to the length of settlement, and are closelylinked to the presence of forest. Overall, the majority of farmers believe they will not be able to sustain cropping in thefuture, and as forest and fallow become scarce the most feasible option will be for them to move to other areas.Farmers are more optimistic about pasture, which is viewed as a more stable system, with the key to long-termsustainability being weed control. These findings imply that a high degree of information sharing between farmers andscientists is required to establish resource management strategies and social institutions to supportsustainable development strategies at the frontier.