Determining the optimal selective harvest strategy for mixed-species stands with a transition matrix growth model

An optimization model was developed to determine the optimal harvesting strategy needed for uneven-aged mixed-species stands in the Changbai Mountain region of northeast of China. The model takes into account four variables including residual basal area (RBA), the diameter of the largest tree, harvest cycle and a constant representing the ratio of the number of trees in a given diameter class to those in the next larger diameter class (‘q’). According to model simulations, under the objective of maximizing net revenue, the optimal harvesting strategy is defined when the residual basal area equals to 19 m² ha⁻¹, the diameter of the largest tree equals to 44 cm, q 1.3 and the harvest cycle equals to 20 years. If the objective is to maximize the total volume yield, the optimal harvesting strategy is defined when RBA equals to 13 m² ha⁻¹, the diameter of the largest tree equals to 36 cm and the constant ‘q’ equals to 1.9 and the harvest cycle equals to 15 years.     

采收成熟度对清香型烤烟质量的影响

[目的]找出2种不同特性的烤烟品种,不同部位成熟采收的外观差异对烤烟质量的影响。[方法]针对烤烟清香型质量风格,结合红花大金元与云烟85的烘烤特性,对不同部位的烟叶设置不同的采收标准,对烤后烟叶的品质进行检测。[结果]2个品种在不同采收标准下,烤后烟叶的质量变化有所差异。随采收成熟度的提高,2个品种的烤后烟叶总氮、烟碱、钾含量呈下降趋势,总糖、还原糖含量呈先上升下后降趋势,但变化幅度有所不同。在评吸质量上,红花大金元随着采收成熟度的提高,中、上部烟叶香气质、香气量有所增加,烟气浓度降低,上部烟叶杂气、刺激性增强。云烟85随着采收成熟度的提高,香气质、香气量有所增加,中下部烟气浓度有所降低,上部烟叶杂气、刺激性增强。[结论]研究可为烟农准确把握不同品种成熟采收的标准做指导,提高种烟的经济效益,同时也为满足卷烟工业对特色烟叶原料的需求及烤后烟叶的提质增香提供参考。     

桑树夏秋期不同采收程度对种茧育的影响

试验表明,在其他桑园管理措施一致的前提下,夏秋期留叶5～12片,能显著提高卵质及下代孵化率,适当提高4龄结茧率、虫蛹统一生命率及茧质。综合考虑桑叶的产量和质量,实际生产中,夏秋期留叶5-6片,既能保证桑叶产量,又能提高蚕种质量。     

黄土区长期施肥对小麦产量和养分吸收的影响

在长期定位试验基础上研究了施肥对小麦产量和养分吸收的影响。结果表明,合理的肥料配施不但可以大幅度增产,还可提高肥料的肥效,促进作物生长发育,增加小麦体内氮磷钾养分的积累。单施N和M肥料的增产作用不明显,单施P小麦减产38%,NP配施或氮磷肥与有机肥配施小麦产量显著提高,以NPM处理的小麦最高,为5980.0kghm-2,比对照增产4436kghm-2,增幅287.31%。肥料间以氮磷肥的交互作用最明显,连应值最高,为3859.5kghm-2;氮磷肥配施还可明显提高氮肥和磷肥的肥效,但有机肥肥效则以NM配施最高。小麦的综合长势以NM配施最好,株高略低于NPM配施,穗长、穗粒数、千粒重均有所增加;氮磷养分吸收总量以NPM配施为最高,钾养分吸收总量则以NM配施最高;氮收获指数以NM配施最高,为77%,磷收获指数以NP配施最高,为87%,钾收获指数以NP和NPM配施最高,为16%。     

施磷对西北沿黄灌耕灰钙土玉米/鹰嘴豆间作产量及种间相互作用的影响

本试验在西北沿黄有效磷含量较低的灌耕灰钙土上研究了田间施磷水平对单作和间作玉米、鹰嘴豆的根际酸性磷酸酶活性、产量和土地资源利用效率的影响。结果表明,在不施磷(P0)和施磷量为40kg·hm-2(P40)时,玉米/鹰嘴豆间作系统的生物学产量或经济产量的土地当量比(LER)均小于1,间作系统未表现出土地资源利用的优势,主要原因是鹰嘴豆产量降低;当施磷量为80kg·hm-2(P80)时,LER1,间作系统表现出土地资源利用优势。P0、P40和P80处理间作玉米产量分别比相应单作增产3%、12%和19%;间作鹰嘴豆产量P0和P40处理显著低于单作。从玉米出苗到鹰嘴豆收获的间作作物共生期内,间作玉米相对于鹰嘴豆具有较强的水分和养分等资源的竞争力(Amc0),从鹰嘴豆生长动态曲线可以看出,P0、P40处理这种竞争在共生期明显,P80处理竞争不明显。各施磷水平下,间作玉米的收获指数高于单作,而间作鹰嘴豆的收获指数低于单作。鹰嘴豆通过分泌酸性磷酸酶促进玉米对有机磷利用的种间互惠作用未体现,两次取样中,不施磷时,间作鹰嘴豆根际土壤的酸性磷酸酶活性低于单作。基于本研究,西北沿黄灌耕灰钙土施磷量为0和40kg·hm-2时,玉米/鹰嘴豆间作系统无明显的间作优势,磷肥量为80kg·hm-2时表现出较为明显的间作优势。     

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。     

制种高粱适宜收获时期研究

以高粱雄性不育系Ａ２Ｖ４Ａ为研究对象，对植株在不同成熟时期各器官的干物质积累动态进行了研究，并进行子粒收获产量比较。结果表明，高粱子粒在完熟期干物质的积累达到最高值，种子生活力也达到最高，此期是制种高粱的适宜收获时期。     

Effect of timing of a deficit-irrigation allocation on corn evapotranspiration, yield, water use efficiency and dry mass

Water regulations have decreased irrigation water supplies in Nebraska and some other areas of the USA Great Plains. When available water is not enough to meet crop water requirements during the entire growing cycle, it becomes critical to know the proper irrigation timing that would maximize yields and profits. This study evaluated the effect of timing of a deficit-irrigation allocation (150 mm) on crop evapotranspiration (ETc), yield, water use efficiency (WUE = yield/ETc), irrigation water use efficiency (IWUE = yield/irrigation), and dry mass (DM) of corn (Zea mays L.) irrigated with subsurface drip irrigation in the semiarid climate of North Platte, NE. During 2005 and 2006, a total of sixteen irrigation treatments (eight each year) were evaluated, which received different percentages of the water allocation during July, August, and September. During both years, all treatments resulted in no crop stress during the vegetative period and stress during the reproductive stages, which affected ETc, DM, yield, WUE and IWUE. Among treatments, ETc varied by 7.2 and 18.8%; yield by 17 and 33%; WUE by 12 and 22%, and IWUE by 18 and 33% in 2005 and 2006, respectively. Yield and WUE both increased linearly with ETc and with ETc/ETp (ETp = seasonal ETc with no water stress), and WUE increased linearly with yield. The yield response factor (ky) averaged 1.50 over the two seasons. Irrigation timing affected the DM of the plant, grain, and cob, but not that of the stover. It also affected the percent of DM partitioned to the grain (harvest index), which increased linearly with ETc and averaged 56.2% over the two seasons, but did not affect the percent allocated to the cob or stover. Irrigation applied in July had the highest positive coefficient of determination (R²) with yield. This high positive correlation decreased considerably for irrigation applied in August, and became negative for irrigation applied in September. The best positive correlation between the soil water deficit factor (Ks) and yield occurred during weeks 12-14 from crop emergence, during the “milk” and “dough” growth stages. Yield was poorly correlated to stress during weeks 15 and 16, and the correlation became negative after week 17. Dividing the 150 mm allocation about evenly among July, August and September was a good strategy resulting in the highest yields in 2005, but not in 2006. Applying a larger proportion of the allocation in July was a good strategy during both years, and the opposite resulted when applying a large proportion of the allocation in September. The different results obtained between years indicate that flexible irrigation scheduling techniques should be adopted, rather than relying on fixed timing strategies.     

Differential effect of cultivar and harvest date on nectarine colour,quality and consumer acceptance

The influence of nectarine cultivar and the harvest date on fruit colour, fruit size, fruit quality parameters, and consumer acceptance were assessed. The analyses were carried on cultivars with different fruit taste (acidity and sweetness), from 5-years-old trees at the IRTA-Experimental Station of Lleida (Spain). The six cultivars were grouped in three pairs in which each had a similar commercial harvest date. Each pair comprised by a non-acid cultivar and an acid cultivar, except the pair of ‘Big Top^®’ and ‘Mesembrine^®’, which included two non-acid cultivars. The nectarines were harvested at 8 days intervals on five harvest dates, three of which were before the commercial harvest date, one at commercial harvest and another 1 week after commercial harvest.