Variable-retention harvests in the Pacific Northwest: A review of short-term findings from the DEMO study

In the Pacific Northwest (PNW) region of the contiguous United States, retention of live (green) trees in harvest units is an integral part of forest management practices on federal lands, yet the ecological benefits that result from various levels or patterns of retained trees remain speculative. The Demonstration of Ecosystem Management Options (DEMO) study was established to address these informational gaps. The experimental design consists of six treatments, each 13 ha in size, replicated at six locations (blocks) in western Washington and Oregon. Treatments represent strong contrasts in retention level (15–100% of original basal area) and pattern (trees dispersed vs. aggregated in 1-ha patches) in mature Douglas-fir (Pseudotsuga menziesii) forests. A wide variety of ecological responses and public perceptions of visual quality have been examined; this paper provides a comprehensive review of the short-term (1–7 years) results of these studies. Level of retention had a strong effect on many responses. At 15% retention, regardless of pattern, microclimate, ecological responses, and public perceptions of visual quality did not differ from those measured in the “clearcut” areas of aggregated treatments. In contrast to level of retention, pattern of retention had limited effect on most measures of biological response. Small changes within forest aggregates were balanced by large changes in adjacent harvested areas, thus on average, responses within aggregated treatments were comparable to those in dispersed treatments. Nevertheless, retaining trees in 1-ha aggregates provided several benefits over dispersed retention. Aggregates greatly reduced damage to and mortality of residual trees (particularly at lower levels of retention) and provided short-term refugia for forest organisms sensitive to disturbance or environmental stress (e.g., bryophytes and late-seral herbs). However, aggregates were susceptible to edge effects (e.g., elevated light and temperature), which may compromise their ability to serve as sources for recolonization of adjacent harvested areas. Collectively, our findings suggest that retention levels >15% are needed to effectively retain sensitive plants and animals, ameliorate harsh microclimatic conditions, and gain public acceptance of retention harvests in these forests. A combination of relatively large (≥1 ha) aggregates and dispersed trees at levels considerably greater than current minimum standards in the PNW may be the most effective strategy for sustaining a broad array of forest values in managed stands.     

兴安落叶松鞘蛾对寄主挥发物的反应

运用触角电位仪(EAG)和"Y"型嗅觉仪测试鞘蛾对落叶松9种挥发物,即R-α-蒎烯、S-α-蒎烯、β-蒎烯、罗勒烯、水芹烯、3-蒈烯、月桂烯、莰烯和叶醇的EAG和行为反应.结果表明:在0.4 mol·L-1浓度下,雌蛾除了对R-α-蒎烯、雄蛾除了对R-α-蒎烯和水芹烯没有明显EAG反应外,对其余挥发物的EAG反应与对照相比差异均达到显著水平(P＜0.05),并且雌、雄虫之间的EAG反应也存在一定的差异.利用"Y"型嗅觉仪测试鞘蛾对9种挥发物在0.000 4,0.004,0.04,0.4,0.8 mol·L-1这5个浓度梯度下的行为反应.结果表明:雌虫对S-α-蒎烯、S-β-蒎烯、水芹烯、3-蒈烯、月桂烯、叶醇这6种物质在一定浓度下表现出明显的趋向偏好(P＜0.05);雄虫对罗勒烯、月桂烯、莰烯、叶醇这4种物质在一定浓度下表现出明显的趋向偏好(P＜0.05).由于鞘蛾幼虫具有潜叶取食的特殊习性,为探索利用外源植物挥发物对其取食行为的调控作用,进一步筛选对雌虫有活性的挥发物成分,喷施到健康落叶松苗上,观察幼虫的取食行为.结果表明:喷施挥发物的样枝上,0.004 mol·L-1月桂烯造成幼虫的死亡虫数最少,与对照差异不显著(P＞0.05),其他样枝上幼虫死亡率较对照差异极显著(P＜0.01),表明挥发物可能对幼虫有致害作用,其中,S-α-蒎烯0.04 mol·L-1造成幼虫的死亡率最高,达86.67%.     

木蠹象对受疱锈菌侵染华山松树皮挥发物的EAG和行为反应

采用触角电位仪和"Y"型嗅觉仪分别研究了茶蔗生柱锈菌锈孢子、感疱锈病树皮、华山松健康树皮挥发性成分对华山松木蠹象的触角电生理和引诱活性.羽化3 d的木蠹象对3种挥发性成分在各浓度下都有明显的EAG反应,锈孢子的EAG反应值最大,健康树皮次之,感病树皮最小,且明显小于前二者.同时,嗅觉生测结果证明,锈孢子挥发性成分对木蠹象的引诱活性最低,平均引诱率不超过20%;同样,感病树皮挥发性成分除浓度为1:15外,其余引诱率都低于35%,二者对该虫总体表现出驱避活性;而健康树皮挥发性成分则有明显的引诱活性.EAG反应值与行为反应的趋向率具有一致性.     

椰甲截脉姬小蜂对4种棕榈科植物挥发物的行为反应研究

[目的]阐明4种棕榈科植物挥发物对椰甲截脉姬小蜂的引诱作用。[方法]用“Y”型嗅觉仪观测了椰甲截脉姬小蜂雌蜂对4种棕榈科植物（椰子Cocos nucifera,大王椰子Roystonea regia,槟榔Areca catechu和散尾葵Chrysalidocarpus lutescens）的行为反应。结果14种棕榈科植物未受害心叶和机械损伤心叶挥发物对椰甲截脉姬小蜂没有明显的吸引作用;每叶10头椰心叶甲3龄幼虫为害20—48h,幼虫-散尾葵心叶复合体、幼虫-槟榔心叶复合体和幼虫-椰子心叶复合体对椰甲截脉姬小蜂有明显的吸引作用;幼虫-大王棕心叶复合体仅在36、48h对椰甲截脉姬小蜂有明显的吸引作用;小于或大于这些时间范围,4种复合体对椰甲截脉姬小蜂都没有明显的吸引作用;相比之下,椰甲截脉姬小蜂对幼虫-椰子心叶复合体的趋向率稍强于其他3种复合体,但对4种复合体的行为反应没有明显差别。结论 椰心叶甲幼虫为害寄主植物心叶后,诱导的植物挥发物可引起椰甲截脉姬小蜂的寄主栖境定向行为。     

沙力河大桥静动载试验

沙力河大桥为先张法预应力混凝土空心板,通过现场静动力荷载试验,测得桥梁结构的力学指标和性能指标.对试验值与理论计算值进行比较分析,以评定该桥的实际承载能力及现有技术状况,进而验证该桥的设计质量,评定该桥的施工质量,并为该桥的竣工验收及后期的安全运营提供科学依据.     

3种彩色叶玉簪光合日变化

采用CIRAS-2光合测定仪测定3种彩叶玉簪的光合参数.光响应曲线应用叶子飘新模型进行拟合并求得光饱和点、光补偿点.结果表明:3种玉簪的光合速率均呈双峰曲线,峰值出现在10:00时和16:00时,且第1峰值大于第2峰值,均有明显的光合“午休”现象,这主要是受非气孔限制因素影响;其光饱和点、光补偿点分别在776.24 ～...     

不同植食性昆虫危害棉花后棉株5种防御基因表达变化

 【目的】了解棉花体内5种防御蛋白基因在棉花防御植食性害虫中的作用。【方法】使用定量PCR分别测定棉铃虫、斜纹夜蛾、甜菜夜蛾危害和机械损伤0（未处理的对照）、6、12、24、48、60 h后,多酚氧化酶（PPO）、叶绿体铜/锌超氧化物歧化酶、ATP合酶β亚基、捕光蛋白复合物Ⅱ、热激蛋白（Hsp70）等5种棉花防御蛋白基因表达量的变化。【结果】在4种危害处理试验中,多酚氧化酶、热激蛋白和叶绿体铜/锌超氧化物歧化酶对昆虫的取食危害应答较强,捕光蛋白复合物Ⅱ对机械损伤的应答较强,ATP合酶β亚基对昆虫的取食危害和机械损伤应答都较强。PPO对棉铃虫危害应答较快,对甜菜夜蛾危害的应答反应较为迟钝,对斜纹夜蛾的危害没有特异的应答。经过上述4种处理,棉花体内Hsp70表达量都有明显的反应,对棉铃虫和甜菜夜蛾危害反应上调较大。ATP合酶β亚基在受到对机械损伤和斜纹夜蛾危害后表达量下调,而在受到棉铃虫和甜菜夜蛾危害后表达量上调。捕光蛋白复合物Ⅱ在受到对机械损伤、甜菜夜蛾和斜纹夜蛾危害后表达量下调,而在受到棉铃虫危害后表达量上调。叶绿体铜/锌超氧化物歧化酶在受到对机械损伤和斜纹夜蛾危害后表达量下调,而在受到棉铃虫和甜菜夜蛾危害后表达量上调,该基因对斜纹夜蛾危害的应答较强,对甜菜夜蛾危害特异性应答较弱。【结论】棉花对于不同昆虫的危害所产生的应答响应不同,具有一定的专一性。     

松梢象对红松萜烯类挥发物的触角电位及行为反应

本文研究了松梢象对寄主红松挥发物组分S型α一蒎烯、R型α一蒎烯、卢一蒎烯、β一月桂烯、罗勒烯、莰烯、3一蒈烯及反一柠檬烯8种挥发物,在0．0004、0．004、0．04、0．4及0．8mol／L浓度下的触角电位反应及行为反应。结果表明：这8种挥发物单体在各浓度下均能引起松梢象的触角电位（EAG）反应,且相同挥发物EAG...     

Priming: it’s all the world to induced disease resistance

After infection by a necrotising pathogen, colonisation of the roots with certain beneficial microbes, or after treatment with various chemicals, many plants establish a unique physiological situation that is called the ‘primed’ state of the plant. In the primed condition, plants are able to ‘recall’ the previous infection, root colonisation or chemical treatment. As a consequence, primed plants respond more rapidly and/or effectively when re-exposed to biotic or abiotic stress, a feature that is frequently associated with enhanced disease resistance. Though priming has been known as a component of induced resistance for a long time, most progress in the understanding of the phenomenon has been made over the past few years. Here we summarize the current knowledge of priming and its relevance for plant protection in the field.     

Oligochitosan induces cell death and hydrogen peroxide accumulation in tobacco suspension cells

Oligochitosan has been shown to induce several plant defense responses. In the present work, the effect of oligochitosan on tobacco cell survival was investigated. The results showed that oligochitosan caused tobacco cell death in a dose-dependent manner. About 40.6 % tobacco cells died when cultured for 72 h after 500 μg ml⁻¹ oligochitosan treatment. Certain aspects of this cell death process appeared to be similar to apoptosis in animal cells. These included shrinkage of cytoplasm and condensation of chromatin. Oligochitosan also induced H₂O₂ accumulation in tobacco cell suspension culture. The role of H₂O₂ in the signal transduction that leads to cell death was investigated. Co-treatment of tobacco cells with oligochitosan and catalase inhibited H₂O₂ accumulation but did not inhibit the induction of cell death. The results suggested that apoptosis-like cell death of tobacco cells induced by oligochitosan is independent of H₂O₂ signal pathway.