Growth, survival, and root system morphology of deeply planted Corylus colurna 7 years after transplanting and the effects of root collar excavation

Urban trees are frequently planted with their root collars and structural roots buried well below soil grade, either because of planting practices, nursery production practices, or both. These deeply planted structural roots can impair tree establishment and are thought to reduce tree growth, lifespan, and stability, although research has provided few and contradictory results on these questions to date. This study examines container-grown (55 L) Turkish hazel trees (Corylus colurna L.), planted either at grade, 15 cm below grade, or 30 cm below grade into a well-drained silt loam soil, over nearly 8 years. Five years after planting, in 2004, remediation treatments (root collar excavations) were performed on two replicates of each below-ground treatment. Subsequently, all trees were subjected to flooding stress by being irrigated to soil saturation for approximately 6 weeks. In 2006, flooding stress was repeated. Trees root systems were partially excavated in 2007, and root architecture was characterized. Deep planting did not affect trunk diameter growth over 8 years. Survival was 100% for the first 5 years; however, one 30 cm below grade tree died after flooding in 2004 and another died after the 2006 flooding. Photosynthesis was monitored during the 2004 flooding and all trees experienced decline in photosynthetic rates. There was an apparent slight delay in the decline for trees with excavated root collars and those planted at grade. Girdling roots reduced trunk taper and occurred primarily on unremediated trees planted 30 cm below grade.

Selected individual roots were excavated and followed from the root ball and were observed to gradually rise to the upper soil regions. Analysis of roots emerging from excavation trench faces indicated that vertical root distribution at approximately 1.25 m from the tree trunks was the same regardless of planting depth. Longterm consequences of planting below grade are discussed.     

Effects of Tillage and Fertilization on Biomass, Roots, N-Accumulation and Nodule Bacteria of Vetch (Vicia sativa cv. Alexander)

Field experiments were conducted to determine the effects of tillage (ploughing followed by one rotary hoeing (CT), rotary hoeing (MT) and no-tillage (NT)) and type of fertilization (NP 154/75 kg ha⁻¹, digested farmyard manure 30 t ha⁻¹) on growth (biomass and roots), N-accumulation and nodulation of vetch plants (Vicia sativa cv. Alexander) at different stages. The highest dry matter yields and root weight were determined for the NT and the lowest for the CT systems. The NT system promoted nodulation of vetch plants to a higher degree than the MT and CT systems. At the time just before harvesting, the N-accumulation in the above ground plants, was 54.3 for CT, 76.7 for MT, and 109.0 kg ha⁻¹ for NT, and the corresponding values at roots were 73.3, 112.0 and 173.3 kg ha⁻¹. Growth and nodulation of vetch plants was in general much better on farmyard manure plots than it was with the NP fertilization. The closest correlation coefficients between dry matter of biomass and roots on the one hand, and number of nodules and percentage N in roots on the other, were found with NT. The highest correlation between nodulation and percentage N in roots (r = 0.91***) was observed at the 128-days-old vetch plants. The highest correlation between the number of nodules and percentage N in biomass (r = 0.82**) was found at the beginning of the plants' flowering period. *, **, *** indicate significance at P = 0.05, 0.01 and 0.001 respectively.     

Field performance of containerized black spruce seedlings with root systems damaged by freezing or pruning

Roots of 2-year-old black spruce seedlings (Picea mariana [Mill.] B.S.P.) were exposed to freezing temperatures to destroy 20, 40, 60, and 80% of the root systems. For comparison, other root systems were pruned to eliminate the same proportions of roots. Treated and control seedlings were planted in spring 1992 at Forêt Montmorency (the Université Laval forest research station, 50 km north of Quebec City). From 1992 to 1995, survival, shoot height and stem diameter were measured. Mortality mainly occurred in 1993, the year after planting; pruned seedlings showed practically no mortality while seedlings with 20, 40, 60, and 80% of their root systems affected by frost showed mortality rates of 0, 6, 17, and 24%, respectively. Shoot height and stem diameter decreased with increasing root damage when compared to controls. After three years on the planting site, shoot height was reduced by 2, 8, 11, and 18% while stem diameter was reduced by 4, 21, 25, and 24% for 20, 40, 60, and 80% frost damage, respectively. For pruned seedlings, shoot height was increased by 3% at 20% damage and was decreased by 1, 3, and 13% for 40, 60, and 80% root damage while stem diameter was reduced by 1, 4, 8, 19% for 20, 40, 60, and 80% respectively. Use of damaged seedlings on the planting sites should be limited in order to reduce the cost of replacement planting.     

我国基层农机维修能力分析与维修质量提升途径

近年来,我国农业机械的使用量明显增加,为农业生产的顺利开展提供了有力保证,与此同时农机维修服务工作也得到了长足发展,但与农机技术和农机保有量的快速进步相比,基层农机维修能力仍不尽人意,全面提升基层农机维修能力意义重大.农机维修的质量直接关系到农业机械的使用状态,对于农业生产的顺利实施影响很大,为进一步提升我国农业机械化...     

土壤表土中植物根系影响其抗蚀性的模拟降雨试验研究——以张家口试验区为例

土壤中植物根系的存在可以增强土壤的抗蚀性,溅蚀量、贯入深度和被崩解的情况等都是土壤抗蚀性的反映。通过对人工添加根系、固有根系和缺少根系三种不同土壤类型,进行的溅蚀、贯入和崩解试验,发现具有植物根系的土壤,其崩解速率远比少根系或缺少根系的土壤为慢,而根系的多少则似乎与溅蚀、贯入不存在明显的关系,后者更多地取决于土壤的颗粒组成特性。     

Electrostatic method to separate roots from soil

Complete removal of roots from soil samples is a prerequisite for most of the chemical and biological analyses. A simple electrostatic method of separating roots from sieved, largely mineral soil substrates was optimized and examined by the addition of ¹⁴C labeled fine roots to sandy, silt loamy and clay loamy samples. Depending on soil texture, between 40% and 50% of fine roots can be removed from 100 g of sieved soil in less than 10 minutes. The root‐free soil substrate and the extracted roots can be used for analyzes or experiments immediately after the separation. The proportion of the mineral particles remaining in the root fraction depends on duration of separation, distance between the charged plate and the sample, and soil texture. The proportion of separated mineral particles is about 90%—95% (w/w) in sandy and 70%—85% in silt loamy and clay loamy substrates. The electrostatic method of root separation may take place before the analysis of C_t and N_t contents, and is suitable for soil samples preparation for incubation experiments.     

冬小麦根系对不同生育时期渍水胁迫的生物学响应

为了研究不同生育时期渍水逆境对北方地区生态条件下冬小麦根系及地上部生长发育的影响,进行了人工模拟小麦渍水试验。结果表明,各生育时期渍水均能使小麦上位次生根数量有所增加,根系POD活性在小麦生育前期也会因渍水而有所提高。但小麦根系总重、根系活力、根系SOD活性、单株绿叶面积、叶片氮、磷及叶绿素含量均因渍水而明显降低,根细胞过氧化产物MDA含量成倍增长。苗期、返青期、拔节期、孕穗期和灌浆期渍水20d分别导致小麦产量降低5.2%、20.8%、43.1%、61.8%和68.3%。     

污灌胁迫对春小麦抗氧化酶活性及根系与幼苗生长的影响

通过水培的方式研究了污水直接灌溉和净化处理后灌溉对小麦根系及幼苗生长影响。结果表明:(1)未处理污水浇灌的小麦幼苗与对照组相比,植株矮小,根短,根数少,茎、叶、根的干重、鲜重均明显降低。(2)污灌胁迫加速了小麦幼苗绿叶和根系的衰亡,并使根系活力明显下降,根系MDA含量水平显著上升。(3)污灌胁迫对小麦根系POD和SOD活性具有激活效应,但随胁迫时间的延长,污灌胁迫对SOD活性转为抑制效应,SOD活性迅速下降。(4)净化处理后的污水浇灌的小麦幼苗与对照没有明显差异。     

微灌毛管水力解析及优化设计的遗传算法研究

根据微灌毛管水力学特性,应用遗传算法理论和方法,提出微灌毛管水力解析及设计的新方法,建立了两种典型毛管水力解析和设计的遗传算法模型及求解方法,该方法可适用于非均匀坡度、不等间距及不等流量灌水器的毛管解析和设计。模拟计算结果表明,该方法具有较高的求解效率和计算精度。     

平邑甜茶延长根和吸收根抗凋亡基因的表达差异及其对2,4-D 的响应

 以3 年生平邑甜茶[Malus hupehensis（Pamp）Rehd. var. pinyiensis Jiang]盆栽树为材料,通过2,4-D 水溶液灌根处理,探讨了新根（延长根和吸收根）细胞死亡及其抗凋亡基因的表达特征。结果表明,在60 mg · L^-1 2,4-D 处理后的70 d 内,新根细胞死亡量和类caspase3/7（半胱天冬酶）活性先上升后下降,ATP 含量和根系活力的变化与之相反。平邑甜茶抗凋亡基因MhBAG、MhBI-1 与MhHSP70 在新根中均受2,4-D 诱导,随着2,4-D 处理时间的延长,MhBAG 基因的表达水平先下降后逐渐升高,MhBI-1 与MhHSP70 则先升高后下降。在2,4-D 处理下,吸收根细胞死亡量与根系活力的变化幅度明显高于延长根,吸收根MhBI-1 与MhHSP70 表达量的早期升高幅度大于延长根,表明吸收根细胞对2,4-D 的敏感性高于延长根;但在基因表达高峰时,延长根抗凋亡基因表达量的升高倍数明显高于吸收根,暗示延长根比吸收根有更强的抗凋亡能力。