Stand establishment,root development and yield of winter wheat as affected by tillage and straw mulch in the water deficit hilly region of southwestern China

Good crop stand establishment and root system development are essential for optimum grain yield of dryland wheat （Triti-cum aestivumL.）. At present, little is known about the effect of tilage and straw mulch on the root system of wheat under dryland areas in southwestern China. The aim of this study was to evaluate the effect of three tilage treatments （no-til, NT; rotary til, RT; conventional til, CT） and two crop residue management practices （straw mulch, ML; non-straw mulch, NML） on stand establishment, root growth and grain yield of wheat. NT resulted in lower soil cover thickness for the wheat seed, higher number of uncovered seeds, lower percentage of seedling-less ridges and lower tiler density compared to RT and CT; ML resulted in higher tiler density compared to NML. Straw mulching resulted in more soil water content and root length density （RLD） at most of the growth stages and soil depths. The maximum RLD, root surface area density and root dry matter density were obtained under NT. In the topmost 10 cm soil layer, higher RLD values were found under NT than those under RT and CT. There were no signiifcant differences in the yield or yield components of wheat among the tilage treatments in 2011–2012, but NT resulted in a signiifcant higher yield compared to RT and CT in 2012–2013. Grain yield was signiifcantly higher in ML compared to in NML. A strong relationship was observed between the water-use efifciency and the grain yield. Both NT and ML proved beneifcial for wheat in term of maintaining higher tiler density, better soil water status and root growth, leading to a higher grain yield and enhanced water-use efifciency, especialy in a low rainfal year.

Late-entry commercial thinning effects on Pinus banksiana:growth, yield, and stand dynamics in Québec, Canada

We studied late-entry commercial thinning effects on growth, yield, and regeneration in a 48-year-old jack pine(Pinus banksiana Lamb.) stand. Applied thinning intensities were 27, 32, and 47% of merchantable basal area(BA) excluding skidding trails. After 15 years, mean diameter at breast height of surviving trees in the 47% BA removal increased by 4.9 cm(25%) compared to the unthinned control. The 47% BA removal also increased gross merchantable volume(GMV) tree-1by 46% compared to the control. The 27% BA removal had twice as much GMV ha-1compared to the 47% BA removal after15 years. Moreover, cumulative GMV ha-1was much higher in the 27% BA removal than in the unthinned control. The highest thinning intensity produced larger trees on average, while the lowest thinning intensity maximized volume production per hectare. Maintenance of acceptable growing stock throughout the 15-year period in the 27% BA removal could provide other ecosystem functions such as biodiversity enhancement or wildlife habitat by delaying senescence. Regeneration data showed that a shift in species composition occurred in the understory. After 15 years, the understory was dominated by black spruce(Picea mariana(Mill.) B.S.P.), white birch(Betula papyrifera Marsh.), and trembling aspen(Populus tremuloides Michx.). If regenerating jack pine is an objective after final overstory removal, additional efforts will be needed to re-establish this species.

不同松树树种段木栽培茯苓产量对林分郁闭度的响应

【目的】探明林分郁闭度和不同松树树种段木组合栽培对茯苓产量的影响,为提高茯苓栽培产量提供科学依据。【方法】以茯苓为研究对象,选择低、中、高3种郁闭度林分,分别采用湿地松、马尾松和火炬松3种松树段木栽培茯苓,考察松树不同松种与林分郁闭度组合处理茯苓菌核个数、单个鲜重和总鲜重,通过方差分析和多重比较筛选树种与林分郁闭度的最佳搭配方案。【结果】湿地松段木栽培茯苓水溶性多糖含量为0.49%,马尾松和火炬松段木栽培均为0.26%。湿地松和马尾松段木栽培,中郁闭度林分茯苓单个鲜重和总鲜重显著高于低郁闭度;火炬松段木栽培,高郁闭度林分茯苓总鲜重低于中郁闭度且显著低于低郁闭度。【结论】湿地松、马尾松和火炬松3种松树段木栽培的茯苓综合品质良好,其中,以湿地松段木栽培茯苓的可溶性多糖含量最高。3种郁闭度林分环境下最佳段木栽培搭配方式:低郁闭度林分+火炬松段木,中/高郁闭度林分+湿地松或马尾松段木。

不同含水率与静置时间下滩涂土壤流变特性试验

为了研究贝类养殖的滩涂土壤的流变属性和结构稳定性,采用旋转流变仪对不同含水率和不同静置时间的滩涂土壤进行了流变试验,通过单因素试验研究了各因素对滩涂土壤流变特性的影响,并分析了土壤剪切过程中的变化机理。同时,通过Response Surface Methodology中的Central Composite Design试验建立了屈服应力与含水率和静置时间之间的数值模型,并比较了含水率和静置时间对屈服应力产生的影响。结果表明:1)剪切过程中滩涂试样经过了弹塑性阶段、固液转化阶段和流体阶段,滩涂土壤表现出了静置时间越长,固液转化阶段就越长的性质,且剪切过程中表现出剪切稀化的性质。2)静置时间的增加会导致整体剪切应力和屈服应力同时增加,含水率的增加会导致整体剪切应力和屈服应力的降低,且滩涂土壤存在一个含水率分界点,此含水率分界点在64.5%~67.0%之间,当超过这个含水率分界点的试样的静置时间超过31 h时,试样的屈服应力基本不会再发生较大的波动,大小在2240~4380 Pa之间,此外,静置时间在0~53 h之间且含水率在62.0%~69.5%之间的试样的屈服应力在1870~5410 Pa之间。3)含水率对屈服应力的影响比静置时间的影响更加显著,模型的R^(2)为0.9534,并且在验证试验中,屈服应力的测量值与预测值之间的误差在15.0%以内,都说明了数值模型的可靠性。研究定性和定量地表征了滩涂土壤的流变特性,为滩涂贝类采收机械的研发和优化提供参考。

吉林省立木材积出材率表编制技术方案的研究

从样木的选取单位、要求与数量,到外业调查方法、内业立木材积、出材率表的计算方法与验证,以及最终形成立木材积、出材率表等方面,系统阐述吉林省立木材积、出材率表的编制过程,以期为全国各地编制立木材积、出材率表提供借鉴。

Competition-density effect of tree organs in Acacia auriculiformis stands

The competition-density (C-D) effects for mean mass for tree, stem, branch and leaf were analyzed in Acacia auriculiformis stands. Mean tree mass-density and mean organ mass-density were well explained by the C-D equation of tree and the C-D equation of tree organ, respectively. An equation describing the relationship between mean leaf area u and density was formulated that fit the u-data well. The relationship between mean tree mass w and the ratio of each organ to mean tree mass (wo/ w) was examined. With increasing w, the stem mass ratio wS/w increased, whereas the branch mass ratio wB/w and the leaf mass ratio wL/w decreased. The yield difference between the lowest-density stand and the high-density stand became greater with stand growth. However, the yield of the mid-density stand was slightly lower than the yield of the high-density stand during the experimental period. To produce the most desirable combination of demanding individual-tree size and relative high stem yield, the mid-density is recommended as proper planting density for future management of A. auriculiformis stands.

STUDY ON THE METHOD OF CONSTRUCTING VARIABLE-DENSITY YIELD TABLE

Growth of stand average DBH is discussed bassed on relationship between standgrowth and stand density.Growth equation of stand average DBH is fitted with data of 65 plotsand 130 stem analyses of site index 18 meter of old-growth Larch(Larix gmeliniiRupr.)collectedin Great Xing’an Mountain m Inner Monglia.Variable-density yield tables of old—growth Larchare constructed based on growth equation of stand average DBH and relationship between standaverage DBH and the other stand attributes.

Spruce forest stands in a stationary state

We present stationarity criteria for forest stands,and establish embodiments using a Norwegian empirical stand development model.The natural stationary states only slightly differ from the outcome of long-term simulations previously implemented using the same empirical model.Human interference in terms of diameter-limit cutting is introduced.Consequently,stationary states differing from the natural one appear.Standing volume,growth and monetary value appear low but the financial return rate may be significant.Volume yield and financial return clearly contradict each other,the former arising from harvesting large trees,the latter from frequent removal of small trees.An exponential tree size distribution does not appear to comply with the stationarity criterion.

Dependence of the Yield of Alfalfa on Plant Density and Diet

In this study, under conditions of enclosed soil, experiments were conducted on the dependence of the yield (weight of green mass) of alfalfa (Medicago) on plant density and diet. The experiments were carried out in five variants, in different values of the integrated density of plants and lasted 89 days. As a feed, specially prepared bio fertilizer was used and added with the calculation of 1 kg per 1 m2 of area. In the corresponding control variants, bio fertilizer was not used. Analysis of the experimental results showed that the feeding regime made it possible to obtain a maximum yield at higher integral density. At the same time, the increase in the weight of green mass when using bio fertilizers was about 36%.

抚育技术对金佛山方竹笋生长影响及其经济效益

以云南省威信县麟凤镇4年生金佛山方竹笋用林为研究对象,布设“施尿素+林分结构调整”(Ⅰ)、“施复合肥+林分结构调整”(Ⅱ)、“林分结构调整”(Ⅲ)和对照(CK)4个处理的田间试验,分析不同抚育措施对竹笋生长、产量、产值和经济效益的影响,筛选生态高效的抚育措施组合,为金佛山方竹笋用林合理经营提供科学依据。结果表明:(1)不同抚育措施对金佛山方竹笋生长影响明显,处理Ⅰ、Ⅱ、Ⅲ的出笋数量分别比CK提高146.15%、84.61%和69.23%,处理Ⅰ、Ⅱ的地径分别是CK的1.31倍、1.24倍;(2)不同抚育措施对金佛山方竹笋产量和经济效益影响显著,处理Ⅰ、Ⅱ、Ⅲ的竹笋产量分别是CK的5.35倍、3.22倍、1.65倍,经济效益分别较CK提高492.26%、205.59%、68.53%;(3)不同抚育措施与生态经济可持续发展关系密切,“施尿素+林分结构调整”是金佛山方竹笋用林高效培育技术措施的首选,“施复合肥+林分结构调整”则是生态高效培育的重要技术措施,“林分结构调整”具有经济实用、环境友好的特点,是生态培育的关键技术措施。

油茶低产林高接技术试验研究

为研发适宜湖北地区的油茶高接换冠技术,为油茶低产林改造提供技术支撑,以约40 a生实生油茶大树为砧木,采用四因素三水平九处理正交试验设计和撕皮接法,研究不同嫁接时间、不同嫁接部位、不同遮荫情况及不同嫁接品种对高接成活率的影响。结果表明:影响高接成活率因素的主次顺序为:嫁接时间>嫁接部位>遮荫情况>嫁接品种,嫁接因素最优水平分别为:6月下旬,在油茶树主干下部采用方块芽接法,对嫁接部位打灯笼罩,树体不遮荫,采用长林4号高接成活率可达到85.83%以上。

疏伐对促进红松果林生长与结实的影响研究

针对目前红松果林经营中产量偏低的现象,采取以疏伐为主的措施进行促进红松果林生长和结实的试验。结果表明,疏伐强度分别为45.35%和34.30%的两组试验地,其胸径生长量分别比对照(未经疏伐林分)提高189.7%和154.8%,冠幅生长量提高229.5%和189.5%,结实株率分别提高155%和100%。疏伐可促使红松种子品质明显提高,种子活力和千粒重比对照增加15.4%和8.95%,球果数量和重量增加8.5%和26%,出种率增加171%。强度疏伐(≥50%)可显著提高红松林木生长,促进其开花结实。

黔北大娄山区金佛山方竹林结构及其与竹笋产量的关系

金佛山方竹林结构与竹笋产量的关系是学界关注的热点。在大娄山金佛山方竹中心分布区海拔1600 m左右地带选择天然林和人工林共计5个试验点,定位观测竹笋收购期带壳笋、去壳笋产量、采笋株数及净笋比的动态变化。结果表明:1)依据主要生境因子及方竹林结构主要指标,将21个样地划分为5种方竹林类型;随海拔高度降低,人工林样地数量所占比例增大,土层厚度降低,样地数量和坡度呈“先升后降”的变化。2)不同类型竹林间,除竹林密度、乔木层植物高度及Simpson指数差异不显著外,其它林分结构指标及植物多样性指数均存在显著差异;在各类型竹林中,集约经营的人工林平均胸径及密度较大,乔木层植物平均胸径、高度及密度较小,无灌木层和草本层植物。3)不同类型竹林间,除土壤A层总孔隙度、土壤B层全磷量、速效磷量、毛管孔隙度及总孔隙度差异显著外,其他土壤理化指标差异不显著;在各类型竹林中,集约经营的人工林土壤肥力总量、有效量及孔隙度和其他类型竹林存在较大差异。4)不同类型竹林间,带壳笋产量、采笋株数及净笋比差异不显著,去壳笋产量在部分类型间差异显著;在各类型竹林中,集约经营的人工林带壳笋产量、去壳笋产量和采笋株数较小,净笋比较低。研究结果为认识低海拔地区金佛山方竹林结构与竹笋产量关系提供了科学依据。

林分密度和起源对不同年龄序列巨尾桉人工林生长及生产力的影响

通过分析6种林分密度和2种林分起源下1~7 a生巨尾桉(Eucalyptus grandis×E.urophylla)人工林的林分平均树高、胸径、单株材积和每hm^(2)蓄积量的总生长量、平均生长量和连年生长量,探索一定密度范围内巨尾桉的最适林分密度和起源方式,揭示林分密度和起源对林木生长和生产力的交互影响特征,为提高巨尾桉人工林培养质量和可持续经营提供理论参考.结果表明:1)随着林龄的增加,平均树高、胸径和单株材积的增长幅度逐渐减小,而每hm^(2)蓄积量增幅在造林后期有所提高,4 a时达到数量成熟;2)各林龄下,随着林分密度的增加,平均树高、胸径和单株材积总生长量减小,超过2 a时林分密度1050株/hm^(2)的总生长量显著(P<0.05)高于其他林分密度,每hm^(2)蓄积量则在1800株/hm^(2)下显著高于其他林分密度;3)植苗林的生长和生产力显著高于萌芽林,1050和1650株/hm^(2)适合植苗林的树高、胸径生长和单株材积积累,1800株/hm^(2)适合萌芽林生长和生产量积累.低密度造林(1050株/hm^(2))有利于巨尾桉个体树高、胸径和材积积累,易于大径材培育;高密度造林(1800株/hm^(2))有利于获得最高的蓄积量,提高林分生产力.本地区巨尾桉人工林的最适轮伐年龄为4~6 a.

保护性耕作对绿洲灌区冬小麦产量形成的影响

2004—2007年采用田间定位试验比较了传统耕作(T)、传统耕作+秸秆还田(TIS)、免耕不覆盖(NT)、免耕秸秆覆盖(NTS)和免耕立茬(NTSS)5种耕作模式在甘肃河西绿洲灌区对冬小麦干物质积累、灌浆特性、产量构成因素及水分利用效率(WUE)的影响。结果表明,NTS和NTSS延缓了冬小麦的生育进程,延长了其灌浆持续期;NTS及NTSS在冬小麦整个生长期都有最高的干物质积累量及相对生长率(RGR),较高的主茎穗平均灌浆速率和小麦籽粒充实指数,穗粒数和千粒重也较高,最终表现为产量和WUE显著提高。与T相比较,2004—2007年NTS和NTSS平均产量分别提高18.6%和23.8%,2005—2007年NTS、NTSS平均WUE分别提高26.8%和16.1%。因此,在沙尘暴发生频繁、水资源日益匮乏的甘肃河西灌区,以免耕秸秆覆盖或免耕立茬的方式种植冬小麦是有利于小麦节水增产及农业可持续发展的种植方式。

出苗期遇雨对不同播种方式棉花出苗及产量的影响

【目的】黄河流域棉花一般采用播后覆盖地膜、齐苗后人工放苗的传统播种方式,但人工放苗费工费时;膜上播种可以减免放苗环节,在少雨的西北内陆棉区已经广泛应用,但能否应用于黄河流域棉区取决于出苗时遇雨是否会影响棉花出苗。研究明确降雨对不同播种方式棉花出苗及产量的影响,为黄河流域棉区选择简便适用的播种方式,促进棉花轻简化生产提供参考。【方法】2014—2015年以陆地棉(Gossypium hirsutium L.)品种K836为试验材料,采用裂区设计,以人工模拟降雨(0和10 mm)为主区,以露地直播(SWM)、播后覆膜(SBM)、膜上播种(SAM)和双膜覆盖(SDM)4种播种方式为裂区,在山东省临清市研究了降雨和播种方式对棉花出苗率、产量及产量构成的影响。【结果】降雨和播种方式对棉花出苗、群体干物质、叶面积指数、单位面积铃数和产量均有显著的互作效应。未遭雨时,膜上播种和双膜覆盖的出苗率、群体干物质、叶面积指数、单位面积铃数和产量与传统播后覆膜相当,露地直播则分别降低了13.6%、19.0%、13.3%、24.7%和27.7%;遭遇降雨时,膜上播种的出苗率、群体干物质、叶面积指数、单位面积铃数和产量分别降低了32.2%、43.1%、26.3%、25.8%和29.2%,露地直播分别降低了42.8%、55.8%、47.2%、35.0%和40.1%,而双膜覆盖的相关指标与传统播后覆膜相当或略好。【结论】出苗期遭遇降雨显著影响膜上播种棉花的出苗和生长,导致减产;双膜覆盖无论是否遭遇降雨都能达到播后覆膜的效果。根据当地生态条件,特别是播种期降雨概率选择适宜的播种方式是保证一播全苗、夺取高产的重要措施。

16年生落叶松白桦纯林与混交林林分生长量及生物量对比

采用标准地调查法研究了大兴安岭加格达奇林业局落叶松、白桦纯林和混交林生长、生物量指标。研究结果表明:落叶松、白桦人工天然混交林较落叶松人工纯林和白桦天然纯林具有较大幅度的增产效益。混交林中落叶松、白桦生长表现均优于各自纯林,平均树高分别高出15.1%和20.5%,平均胸径分别高出8.0%和2.3%,平均单株材积分别增加11.5%和15.8%,林分总蓄积量分别增加14.7%和12.3%。混交林中乔木层生物量、干材生物量和枝叶生物量均显著高于落叶松纯林和白桦纯林,全林生物量也较落叶松纯林和白桦纯林有较大幅度的增加。

平衡施肥对毛竹笋产量的影响效应研究

对奉新县澡下林场毛竹笋材两用林进行平衡施肥的试验 ,研究了不同平衡施肥配方对毛竹笋材两用林出笋数量、产量和竹笋地径 3个产量因子的影响 ,并建立了 2 0 0 0年各处理小区内土壤养分元素N、P、K、Ca、Mg含量与 2 0 0 1年各处理小区单位面积竹笋平均产量的相关方程。试验结果表明 :各平衡施肥配方对平均地径、单位立竹出笋数的影响与进行垦复的对照差异不显著 ,2 0 0 1年各小区竹笋平均地径显著大于 1 997和1 999年的平均地径 ;各养分元素对单位面积竹笋产量的贡献率大小依次为 :N >Mg >P >Ca>K ;K肥对增加竹材直径和提高竹材质量有良好促进作用 ;以产笋为主要目的的竹林 ,最佳施肥配方为N1P1K2 ;以产材为主要目的的竹林 ,最佳施肥配方为N2 P1K2 。

基于林分结构和竹笋产量的有机材料覆盖雷竹林退化程度评价

为建立有机材料覆盖雷竹Phyllostachys praecox林退化程度评价体系,在浙江省临安市雷竹栽培区设置15个样点,在林分结构和竹笋产量等14项因子调查的基础上,进行主成分分析。研究表明,立竹年龄结构、立竹胸径和竹笋产量可作为雷竹林退化程度评价的主要指标;试验区有机材料覆盖雷竹林退化程度可分为4类6级:重度退化(Ⅰ级)、中度退化(Ⅱ,Ⅲ级)、轻度退化(Ⅳ,Ⅴ级)和正常(Ⅵ级)。重度、中度、轻度退化雷竹林所占比例分别为13.34%,26.66%,46.67%,未退化雷竹林仅占13.33%。有机材料覆盖易造成雷竹林立竹年龄结构不合理,立竹胸径减小,立竹整齐度、分布均匀度降低,竹林出现退化,竹笋产量显著下降。

林分生长模型研究的进展

本文叙述了林分生长模型的发展及目前研究方向;评价模型的分类方法和各种模型的关系及应用范围,强调模型系的相容性及完备性原则,指出近代模型往往是一个森林系统,大都含有多个被预测的变量和说明变量,必须注意因子间的关系,用高次、多项式方程决不是好方法。因子间的“相互预报”是模型中的大问题,方程组之间的“循环估计”往往产生有偏估计。