Long-term realised and projected growth impacts caused by autumn gum moth defoliation of 2-year-old Eucalyptus nitens plantation trees in Tasmania,Australia

Insect damage to production forests has the potential to reduce financial returns by retarding tree growth and causing mortality, however, long-term realised quantification of these losses is rare. In order to help elucidate economic damage thresholds for making spray decisions we capitalised on a natural outbreak of autumn gum moth, Mnesampela privata, in a 2-year-old Eucalyptus nitens plantation. Following the partial chemical control of this insect outbreak we measured the tree growth variables diameter at breast height over bark and height of five differing tree defoliation classes for 75 months following tree damage. At the end of this period a threshold model was fitted to describe the relationship between tree defoliation and realised tree wood volumes. The model revealed that realised stand wood volume was not significantly affected up until defoliation exceeded 60% and then declined sharply after this defoliation level was reached. Further support for this defoliation threshold was evident from multiple comparisons among defoliation classes that showed 50% defoliated trees did not have significantly different wood volume compared to more lightly defoliated trees, but did have significantly greater wood volume compared to trees that were 72% or more defoliated. To determine if the realised differences in wood volume resulted in differences in yield over a plantation rotation the E. nitens growth model NITGRO was used to on-grow trees to age 15 years for a ‘best case’ (type 1 growth response, constant growth rates from last inventory until harvest) and ‘worst case’ (type 2 growth response, divergent growth rates from last inventory until harvest) scenario. The threshold model was then fitted to the outcomes of both scenarios and the economic consequences of defoliation were clearly dependent on the growth function assumed.     

摘脱收获复脱分离装置的试验研究

在专用的复脱分离试验装置上,对SG800摘脱机脱穗后的混合物,进行了多因素的性能试验,得出了复脱转筒线速度、凹板栅板间距、脱粒间隙、喂入量等诸因素,与未脱净率、破碎率、夹带损失率、含杂率和功耗等性能指标的相关性及其显著程度,作了因素水平参数组合的初步优选;并测定分析了复脱分离后排出物组成和各性能指标的轴向分布状况;探讨了改善复脱分离性能的途径。     

我国玉米收获机械发展现状及展望

介绍了玉米收获机械的发展过程,阐述了我国玉米收获机械的种类及特点,分析了当前玉米收获机械发展中存在的主要问题,同时提出了为提高玉米收获机械化水平所采取的主要措施。     

收获期对寒地青贮玉米营养价值的影响

以青贮玉米龙辐单208为材料,研究了寒地不同收割期对青贮玉米营养价值的影响。试验结果表明,随收获期推后,青贮玉米全株粗蛋白、粗纤维含量呈递减趋势,粗脂肪变化规律不明显。北方寒地青贮玉米适宜收获期为授粉后40～50d。     

The effect of harvest time and pre harvest treatment on the moisture content of Miscanthus × giganteus

This study aims to determine the most appropriate time to harvest Miscanthus × giganteus between January and April, over three possible harvest windows (Jan, Feb and Mar), relative to the harvest method being employed to cut the crop. The moisture content (MC) of biomass cut in January increased compared to the standing crop (control). From an initial MC of 53% in 2009 and 63% in 2010, the control was 12% and 13% lower than Cut Jan after 4 weeks of the treatment in respective years. The MC of Cut Feb was 19% lower than the control after 4 weeks in 2009. Despite Cut Feb being 4% higher than the control after one week in 2010, both treatments reached 34% MC after 3 weeks. A difference of 16% occurred between the Cut Mar and the control after one week in 2009 while in 2010 Cut Mar was 5% higher than the control after one week. Examining the relationship between stem MC, meteorological parameters and evapotranspiration showed that a combination of relative humidity and evaporation rate (Penman equation.) demonstrated the strongest relationship with crop MC. If harvesting early, lower MC can be achieved by cutting and collecting the crop immediately. An increase in the rate of moisture loss can be achieved later in spring by cutting the material and allowing it to dry for a period of time prior to collection if suitable drying conditions occur. An analysis across several sites showed that such conditions are most likely to occur in February.     

不同采收期对猕猴桃香气成分的影响

采用顶空固相微萃取法(Headspace Solid-Phase Micro-Extractions,HS-SPME),提取美味猕猴桃品种"米良1号"不同采收期果实的香气成分.经气相色谱-质谱联机分析,在10月18日、28日的果实中分别检测出51种、48种香气成分,占各自总峰面积的97.75%和98.36%.果实香气成分主要以酶类、醇类、醛类为主.在两种采收期果实中,除酯类物质呈下降趋势外,醇类、醛类、羧酸类及酮类等香气物质都呈上升趋势.     

不同采收期云南黄连中有效生物碱含量测定

通过比较不同采收季节云南黄连根茎、须根、叶中3种生物碱的含量,确定适宜的采收时间.采用高效液相色谱法,以云南黄连主要有效成分小檗碱、药根碱、巴马汀含量为评价指标,研究7个不同采收时间段云黄连根茎、须根、叶中有效成分含量变化,得出有效成分在根茎中含量最高,须根次之,叶片最低;有效成分在药用部位根茎中的含量在10月及11月最高,云南黄连的最佳采收期为10 -11月的结论.     

Contribution of cultivar,fertilizer and weather to yield variation of winter wheat over three decades: A case study in the North China Plain

Long-term field measured yield data provides good opportunity to assess the impacts of climate and management on crop production. This study used the yield results from a long-term field experiment (1979–2012) at Luancheng Experimental Station in the central part of the North China Plain (NCP) to analyze the seasonal yield variation of winter wheat (Triticum aestivum L.) under the condition of sufficient water supply. The yield change of winter wheat over the last 33 growing seasons was divided into three time periods: the 1980s, the 1990s, and the years of 2001–2012. The grain yield of winter wheat during the 1980s was relative stable. During the 1990s, the annual yield of this crop was continuously increased by 193 kg/ha/year (P < 0.01). While for the past 12 years, yield of winter wheat was maintained at relative higher level, but with larger seasonal yield variation than that back in 1980s. CERES-Wheat model was calibrated and was used to verify the effects of management practices on grain yield. Seven scenarios were simulated with and without improvements in management. The simulated results show that the yield of winter wheat was decreased by 5.3% during 1990s and by 9.2% during the recent 12 seasons, compared with that during 1980s, under the scenario that the yield of winter wheat was solely affected by weather. Seasonal yield variation caused by weather factors was around −39% to 20%, indicating the great effects of weather on yearly yield variation. Yield improvement by cultivars was around 24.7% during 1990s and 52.0% during the recent 12 seasons compared with that during 1980s. The yield improvement by the increase in soil fertility and chemical fertilizer input was 7.4% and 6.8% during the two periods, respectively. The initial higher soil fertility and chemical fertilizer input might be the reasons that the responses of crop production to the further increase in chemical fertilizer were small during the simulation period. Correlation analysis of the grain yield from the field measured data with weather factors showed that sunshine hours and diurnal temperature difference (DTR) were positively, and relative humidity was negatively related to grain yield of winter wheat. The climatic change trends in this area showed that the DTR and sunshine hours were declining. This type of climatic change trend might further negatively affect winter wheat production in the future.     

Local perceptions of Matsutake mushroom management, in NW Yunnan China

Matsutake mushrooms are among the most prized and expensive mushrooms on earth. Since the 1980s NW Yunnan Province has become the largest exporter of Matsutake in China, and money from their sale has become crucial to local livelihoods and to the provincial tax base. Amid fears of declining productivity, regulations have been enacted to control Matsutake harvest, though enforcement remains largely in the hands of harvesters themselves. Here, we measure local harvesters’ perceptions of the ecological determinants of mushroom productivity in contrast to that of the outsider conservation community. We interview 122 harvesters in eight villages in Diqing province, NW Yunnan to determine what is perceived to be detrimental to Matsutake yield, how yield can be improved in the future and who harvesters trust for information. Our results indicate that village leaders and forestry officials are overwhelmingly the most trusted sources for information. Mann and Whitney U tests show general consensus among villages, and MRPP analysis shows general consensus within villages. One village showed significantly higher levels of trust in NGOs. Of the 86% of harvesters who had perceived declining productivity trends over the past 10 years, soil disturbance, climate change, and habitat degradation were most often-cited as causal factors. Log-linear analysis showed almost no significant interactions between perceptions and harvester demographics. Environmental protection and reducing soil disturbance were most often-cited as potentially increasing future yields. We suggest that local and outsider knowledge are complimentary in this system, and that forestry officials and village leaders provide the best conduits for management information.     

不同筋性春小麦籽粒不同发芽程度下的品质分析

为了解穗发芽不同程度下对不同筋性春小麦品种品质的影响,该实验选取强筋小麦品种克春1号、克丰6号,中筋品种克旱16、克旱21,弱筋小麦品种新克旱9、克丰9为实验材料,利用人工智能气候培养箱模拟自然环境,人为控制种子发芽程度并测定相关数据,结果表明:出粉率在萌动状态下,强筋>中筋>弱筋,随着发芽程度的加深,出粉率并未表现出与小麦筋性相关的规律性;强筋粉降落值在萌动状态下,较正常状态下降幅度大于中筋粉,中筋粉大于弱筋粉;各筋性小麦品种其湿面筋含量、干面筋含量以及面筋指数均随发芽程度的加深,而降低。