Plant Stands Research Articles

Plant architecture and spatial structure of an early Permian woodland buried by flood waters, Sangre de Cristo Formation, New Mexico

Abstract Natural molds of 165 stems were found in life position in a 1 m-thick sandstone bed, lower Permian (Wolfcampian), Sangre de Cristo Formation, northern New Mexico. The sandstone represents a single flood event of a river sourced in the Ancestral Rocky Mountains. Most of the flood-buried plants survived and resumed growth. The stem affinities are uncertain, but they resemble coniferophytic gymnosperms, possibly dicranophylls. Stem diameters (N = 135) vary from 1 to 21 cm, with three strongly overlapping size classes. Modern forest studies predict a monotonically decreasing number (inverse square law) of individuals per size class as diameter increases. This is not seen for fossil stems ≤ 6 cm diameter, reflecting biases against preservation, exposure, and observation of smaller individuals. Stems ≥ 6 cm diameter obey the predicted inverse square law of diameter distribution. Height estimates calculated from diameter-to-height relationships of modern gymnosperms yielded heights varying from ~ 0.9 m to > 8 m, mean of ~ 3 m. Mean stand density is approximately 2 stems/m 2 (20,000 stems/hectare) for all stems > 1 cm diameter. For stems > 7.5 cm or > 10 cm diameter, density is approximately 0.24 stems/m 2 (2400 stems/hectare) and 0.14 stems/m 2 (1400 stems/hectare). Stem spatial distribution is random (Poisson). Mean all-stem nearest-neighbor distance (NND) averages 36 cm. Mean NND between stems > 7.5 cm and > 10 cm diameter is approximately 1.02 m and 1.36 m. NND increases in approximate isometry with stem diameter, indicating conformation to the same spatial packing rules found in extant forests and other fossil forests of varying ages. Nearest-neighbor distance distribution passes statistical testing for normality, but with positive skew, as often seen in extant NND distributions. The size-frequency distribution of the stems is similar to those of Jurassic, early Tertiary, and extant woodlands; the early Permian woodland distribution line has the same slope, but differs in that the overall size range increases over time (Cope's rule). The early Permian woodland is self-thinning; its volume versus density relationship shows a self-thinning exponent between − 1.25 and − 1.5, within the range seen in some extant plant stands (− 1.21 to − 1.7).

Possible environmental risks at commercial growing transgenic forage crops

The review considers the potential environmental risks associated with large-scale cultivation of various types of genetically modified forage crops. The results of the study of gene flow in forage grasses occurring in open ecosystems through the dissemination of transgenic pollen by wind and insects at different distances in the stands of forage plants. The necessary conditions for spatial isolation of transgenic and non-transgenic samples of forage crops from each other are described. The ecological, biological, and economic value of forage plants, as well as their ecological and environmental functions in agricultural landscapes, including the significant impact they have on the ecological status of ecological communities, contributing to the preservation and accumulation of organic matter in the biosphere are briefly discussed.

南亚热带格木、马尾松幼龄人工纯林及其混交林生态系统碳氮储量

PDF HTML阅读 XML下载 导出引用 引用提醒 南亚热带格木、马尾松幼龄人工纯林及其混交林生态系统碳氮储量 DOI: 10.5846/stxb201401030018 作者: 作者单位: 中国林业科学研究院,中国林业科学研究院,中国林业科学研究院,中国林业科学研究院,中国林业科学研究院热带林业实验中心 作者简介: 通讯作者: 中图分类号: 基金项目: 中国科学院碳专项(XDA05060100);林业公益性行业科研专项(201104006) Carbon and nitrogen storage in monoculture and mixed young plantation stands of Erythrophleum fordii and Pinus massoniana in subtropical China Author: Affiliation: Chinese Academy of Forestry,Chinese Academy of Forestry,Chinese Academy of Forestry,Chinese Academy of Forestry,Experimental Center of Tropical Forestry,Chinese Academy of Forestry Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:研究比较了南亚热带6年生格木(Erythrophleum fordii)、马尾松(Pinus massoniana)幼龄人工纯林及马尾松与格木混交林生态系统碳氮储量及其分配特征。结果表明,生态系统总碳储量依次为马尾松-格木混交林(137.75 t/hm2) >格木纯林(134.07 t/hm2) >马尾松纯林(131.10 t/hm2),总氮储量则为格木纯林(10.19 t/hm2) >马尾松-格木混交林(8.68 t/hm2) >马尾松纯林(7.01 t/hm2)。3种人工林生态系统碳氮库空间分布基本一致,绝大部分储存于0-100 cm土壤层,平均占生态系统总储量的81.49%和96.91%,其次为乔木层(分别占17.52%和2.69%),林下植被和凋落物层所占比例最小。林地土壤碳主要集中于表土层,其中0-30 cm土层平均碳储量为52.52 t/hm2,占土壤总碳储量(0-100 cm)的47.99%,土壤氮的分布则无明显规律。相比于纯林,与固氮树种混交的营林方式表现出更大的碳储存能力。3种幼龄人工林生态系统较低的地上与地下部分碳氮分配比,表明其仍具有较强的碳氮固持潜力。 Abstract:Carbon sequestration in forest ecosystems is recognized as a key mechanism for mitigating the accumulation of atmospheric carbon dioxide. However, both forest carbon pools and sequestration vary according to tree species, age of the stand, soil types, climate, environmental disturbances, and management practices. Tree species composition and management practices are important tools for increasing carbon storage in forest ecosystems. Plantation is becoming a key component of the world's forest resources and is playing an important role in sustainable forest management. Well-designed, multi-purpose plantations can reduce the pressure on natural forests and complement some ecological resources provided by natural forests in addition to mitigating climate change through direct carbon sequestration. Afforestation and reforestation are important measures for managing commercial forests in subtropical China. However, the large-scale development of monoculture plantations of coniferous species (e.g., Pinus massoniana and Cunninghamia lanceolata) and exotic species (Eucalyptus spp.) has caused a number of problems, such as the loss of biodiversity, degradation of soil fertility, reduction of ecosystem stability, and loss of ecological resources. Thus, some broad-leaved tree species with different functions (e.g., indigenous valuable broad-leaved species and nitrogen-fixing species) have been developed for restructuring the plantations. In this study, three young plantation stands (monoculture of Erythrophleum fordii, monoculture of P. massoniana and a mixed stand of the two species) were selected to study carbon and nitrogen storage in these ecosystems and their spatial distribution. The results showed that the total carbon storage of the mixed plantation stand was 137.75 t/hm2, higher than that of monoculture stands of E. fordii (134.07 t/hm2) and P. massoniana (131.10 t/hm2). Nitrogen storage was highest in E. fordii (10.19 t/hm2), followed by the mixed plantation (8.68 t/hm2), and then P. massoniana stands (7.01 t/hm2). The spatial distribution of carbon and nitrogen was identical in the three plantation stands, with the majority found in the 0-100 cm soil (occupying an average 81.49% and 96.91% of the total storage, respectively), followed by the above-ground biomass represented by the trees (17.52% and 2.69%, respectively), and the understory vegetation and litterfall. Soil organic carbon was mainly distributed in the top-soil, while soil nitrogen was irregularly distributed. Average organic carbon storage in 0-30 cm soil was 52.52 t/hm2 (47.99% of the total 0-100 cm soil storage). The mixed plantation stands showed a greater capacity for carbon storage in comparison to the other two monoculture stands. The above-/underground ratio of carbon and nitrogen suggested that these three young plantation stands had a high potential for carbon and nitrogen sequestration. The results are significant in that they provide scientific references for tree species selection and plantation management to enhance productivity and carbon sequestration in subtropical China. 参考文献 相似文献 引证文献

Responses of Canopy Reflectance, Light Interception, and Soybean Seed Yield to Replanting Suboptimal Stands

ABSTRACTSoybean [Glycine max (L.) Merr.] planting date trends have steadily shifted earlier within the northern Corn Belt, while inclement weather, insect pressure, and disease pressure associated with spring planting can result in replanting some years. However, limited published literature exists about soybean replant thresholds for suboptimal plant stands and the effects of seed treatments on this decision. This study evaluated three planting dates, three seed treatments, and twelve seeding rate–replant combinations to determine replant thresholds in terms of maximizing seed yield, the effects of seed treatments on these thresholds, and the relationship of cumulative intercepted photosynthetically active radiation (CIPAR) and cumulative normalized difference vegetative index (CumNDVI) on seed yield. Trials were conducted during 2012 and 2013 in southern Wisconsin. Soybean planting in early May increased seed yield by 358 kg ha−1 compared with late May and by 805 kg ha−1 compared with mid‐June. Seed yield reductions were due to decreased seeds m−2 while CIPAR and CumNDVI measurements may partially explain this planting date effect. When initial plant stands were below threshold (<247,000 plants ha–1), filling in these stands with enough seed to bring the final plant stand above the threshold increased yield, whereas using tillage and replanting the entire stand only increased yield when initial plant stands were extremely low (<91,000 plants ha−1). Yield was related to both CIPAR (R2 = 0.54) and CumNDVI (R2 = 0.49) and the latter two variables were highly correlated (r = 0.89). We observed linear yield increases through 700 MJ m−2 of CIPAR; therefore, management practices to increase CIPAR should be used. This study showed that early May planting with a fungicide/insecticide seed treatment (CruiserMaxx) and generating adequate plant stands (>247,000 plants ha−1) maximized CIPAR.

Composition of functional groups of ground vegetation differ between planted stands of non-native <i>Pinus contorta</i> and native <i>Pinus sylvestris</i> and <i>Picea abies</i> in northern Sweden

Intensified forestry increases the interest in replacing native tree species with fast growing non-native species. However, consequences for native biodiversity and ecosystem functioning are poorly understood. We compared cover and composition of major functional groups of ground vegetation between planted stands of non-native Dougl. var. Engelm. and native conifers L. and (L.) H. Karst. in northern boreal Sweden. We quantified the ground cover of lichens, bryophytes, vascular plants and ground without vegetation (bare ground) in 96 stands covering three different age classes (15, 30 and 85 years old). Our study revealed differences in ground vegetation patterns between non-native and native managed forests, and that these differences are linked to stand age and differences in canopy cover. Total vascular plant cover increased with increasing stand age for all tree species, with stands having higher cover than both native conifers. The ground cover of lichens was, although generally low, highest in stands of . stands had a lower cover of vascular plants, but bare ground was more common compared with . Our results suggest that the use of as an alternative tree species in Fennoscandian forestry will influence native ground vegetation patterns. This influence is likely to change with time and future research should consider both temporal and landscape-scale effects from shifting tree-species dominance to and other non-native tree species.Pinus contorta latifoliaPinus sylvestris Picea abies P. contortaPinus sylvestrisP. abiesP. contortaP. contortaPinus contorta

Effects of overgrowing at Cerknica Polje (southern Slovenia) on breeding farmland birds/ Vpliv zaraščanja Cerkniškega polja (južna Slovenija) na gnezdilke kmetijske krajine

Abstract Agriculture has a great impact on biodiversity in Europe. Populations of farmland birds are declining due to both intensification and abandonment of agriculture. The purpose of this study was to determine the effects of overgrowing on the diversity of birds at Cerknica Polje. Six vegetation types were identified on eight survey plots (15.2-31.6 ha each): Short grass - regularly mown wet meadows; Tall herbs - stands of Common Reed Phragmites australis and Reed Canary Grass Phalaris arundinacea; Sparse bushes - stands of low woody plants; Dense bushes - dense stands of bushes; Meadows with trees - mown meadows with scattered trees; Bushes with trees - hedges, trees and dense stands of bushes. In total, 34 species were registered. The heterogeneity of vegetation types correlated positively with the heterogeneity of bird species. The highest density of breeding territories and species was established in Bushes with trees, the lowest in Short grass. No species were registered in all vegetation types, and only Tree Pipit was recorded in five out of six types. Twelve species were registered in only one vegetation type. Cerknica Polje is an important breeding locality for species with the highest breeding density at the national level (e.g. Corncrake Crex crex, Curlew Numenius arquata, Skylark Alauda arvensis, Whinchat Saxicola rubetra, Sedge Warbler Acrocephalus schoenobaenus). These species breed in specific habitats with different stages of succession. A managing plan for the area should therefore combine abandoned plots in different stages of succession and large regularly mown areas. Abandonment of agriculture at Cerknica Polje has led to the emergence of areas with bushes in different succession stages. Efforts should be directed at preserving large complexes of mown wet meadows.

Growth and productivity of New Zealand kauri (Agathis australis (D.Don) Lindl.) in planted forests

BackgroundThe establishment of even-aged planted stands of New Zealand kauri (Agathis australis (D.Don) Lindl.) for timber has been constrained by a lack of quantitative information on productivity and rotation length on which forest management and investment decisions could be made.MethodsStand-level models of height and basal area against time were developed (as well as a stand-volume function to calculate volume from height and basal area) based on planted stands that were up to 83-years old and represented planting sites both within and outside the current natural range of the species.ResultsPlanted kauri was shown to be slow to establish with little height growth for the first five years after planting. Similar trends were observed for basal area and whole-tree volume development. A Schumacher equation with local slope parameter and asymptote bounded at 45 m gave the best fit for height, while a von Bertalanffy-Richards equation in difference form with local slope parameter gave the best fit for basal area. For plantations with an average site index (20.4), height was predicted to be 22.3 m in height at age 60, with a basal area of 78.1 m2 ha-1. Whole-tree volume was predicted to be 702 m3 ha-1. Predicted volume mean annual increment was 11.7 m3 ha-1 yr-1for all stands at age 60. From age 20-60 years, stands with a higher site index had a volume mean annual increment of 18.6 m3 ha-1 yr-1. The best stand exceeded 20 m3 ha-1 yr-1.ConclusionsThis study indicates an opportunity to grow kauri in plantations on selected good-quality sites over rotations of 60-80 years or less.

Effect of Alnus subcordata, Acer insigne and Sequoia sempervirens plantations on plant diversity in Hyrcanian forest of Iran

Gheibi F, Akbarinia M, Kooch Y. 2015. Effect of Alnus subcordata, Acer insigne and Sequoia sempervirens plantations on plant diversity in Hyrcanian forest of Iran. Biodiversitas 16: 10-15. Forest plantation is a common action in order to restore thedegraded forests in Hyrcanian forests of Iran. This study compares the plant biodiversity in four 25-year-old stands of plantation,adjacent understorey of alder (Alnus subcordata C. A. Mey.), maple (Acer insigne Boiss.), sequoia or red wood (Sequoia sempervirens(D. Don) Endl.) and mixed stand (maple and sequoia), located in Salmanshahr of Mazandaran Province, northern Iran. Research carriedout in, 10 sample plots with 20m × 20m area which taken by systematic-random in each plantation. All understorey species wereidentified, recorded and then the biodiversity indices (diversity, richness and evenness) were calculated. Our findings show that theplanted species had significant effects on understorey diversity. Statistical comparisons revealed that the highest and lowest diversity(Simpson and Shanon-Winer) and richness (Margalef and Menhinic) indices occurred in sequoia and alder stands, respectively. Theevenness indices (Camargo and Smith-Wilson) were significantly greater in maple, sequoia and mixed stands compared with the aldertype. As a conclusion, floristic change trends were different according to the planted tree species. A good understanding of thecomplexity of vegetation processes requires long-term monitoring of vegetation change.

Detecting leaf pulvinar movements on NDVI time series of desert trees: a new approach for water stress detection.

Heliotropic leaf movement or leaf ‘solar tracking’ occurs for a wide variety of plants, including many desert species and some crops. This has an important effect on the canopy spectral reflectance as measured from satellites. For this reason, monitoring systems based on spectral vegetation indices, such as the normalized difference vegetation index (NDVI), should account for heliotropic movements when evaluating the health condition of such species. In the hyper-arid Atacama Desert, Northern Chile, we studied seasonal and diurnal variations of MODIS and Landsat NDVI time series of plantation stands of the endemic species Prosopis tamarugo Phil., subject to different levels of groundwater depletion. As solar irradiation increased during the day and also during the summer, the paraheliotropic leaves of Tamarugo moved to an erectophile position (parallel to the sun rays) making the NDVI signal to drop. This way, Tamarugo stands with no water stress showed a positive NDVI difference between morning and midday (ΔNDVImo-mi) and between winter and summer (ΔNDVIW-S). In this paper, we showed that the ΔNDVImo-mi of Tamarugo stands can be detected using MODIS Terra and Aqua images, and the ΔNDVIW-S using Landsat or MODIS Terra images. Because pulvinar movement is triggered by changes in cell turgor, the effects of water stress caused by groundwater depletion can be assessed and monitored using ΔNDVImo-mi and ΔNDVIW-S. For an 11-year time series without rainfall events, Landsat ΔNDVIW-S of Tamarugo stands showed a positive linear relationship with cumulative groundwater depletion. We conclude that both ΔNDVImo-mi and ΔNDVIW-S have potential to detect early water stress of paraheliotropic vegetation.

Carbon storage capacity of different plantation types under sandstorm source control program in Hebei Province, China

Afforestation and reforestation are effective and ecological ways of mitigating elevated atmospheric carbon dioxide (CO2) concentration and increasing carbon (C) storage in terrestrial ecosystems. In this study, we measured the above-ground (tree, herbaceous plants and litter) and below-ground (root and soil) C storage in an aspen plantation (Populus davidiana) monoculture (PD), a larch plantation (Larix pincipis-rupprechtii) monoculture (LP), a pine plantation (Pinus tabulaeformis) monoculture (PT), a larch and birch mixed plantation (L. pincipis-rupprechtii and Betula platyphlla mixed) (MLB), and an apricot plantation (Armeniaca sibirica) monoculture (AS) under the Desertification Combating Program in Hebei Province, the northern China. The objective was to assess the effect of afforestation species on ecosystem C pools of different plantation types. Results showed that C storage of LP stand (258.0 Mg/ha) and MLB (163.4 Mg/ha) were significantly higher than the C storage in PD (45.5 Mg/ha), PT (58.9 Mg/ha) and AS (49.4 Mg/ha), respectively. Soil C was the main carbon pool of the ecosystem C storage in the five plantation stands, ranging from 31.4 Mg/ha to 232.5 Mg/ha, which accounted for 69.0%–90.1% of the total ecosystem C storage. The C storage in tree layer was about 5.2%–23.2% of ecosystem C storage. The herbaceous plants and litter layers contained 1.0%–6.0% and 1.5%–3.3% of ecosystem C storage, respectively. Our results suggest that tree species should be incorporated to accurately develop regional C budget of afforestation program, and also imply that substantial differences in ecosystem C stocks among plantation types can facilitate decision making on C management.

The dynamic relationship between plant architecture and competition.

In this review, structural and functional changes are described in single-species, even-aged, stands undergoing competition for light. Theories of the competition process as interactions between whole plants have been advanced but have not been successful in explaining these changes and how they vary between species or growing conditions. This task now falls to researchers in plant architecture. Research in plant architecture has defined three important functions of individual plants that determine the process of canopy development and competition: (i) resource acquisition plasticity; (ii) morphogenetic plasticity; (iii) architectural variation in efficiency of interception and utilization of light. In this review, this research is synthesized into a theory for competition based on five groups of postulates about the functioning of plants in stands. Group 1: competition for light takes place at the level of component foliage and branches. Group 2: the outcome of competition is determined by the dynamic interaction between processes that exert dominance and processes that react to suppression. Group 3: species differences may affect both exertion of dominance and reaction to suppression. Group 4: individual plants may simultaneously exhibit, in different component parts, resource acquisition and morphogenetic plasticity. Group 5: mortality is a time-delayed response to suppression. Development of architectural models when combined with field investigations is identifying research needed to develop a theory of architectural influences on the competition process. These include analyses of the integration of foliage and branch components into whole-plant growth and precise definitions of environmental control of morphogenetic plasticity and its interaction with acquisition of carbon for plant growth.

Photosynthesis and water use by two Sedum species in green roof substrate

Different succulent plants have been shown to exhibit varying degrees of crassulacean acid metabolism (CAM). This variation has not been consistently shown to relate to water use efficiency (WUE) by these species. This raises fundamental questions about the ecophysiological implications of switching between C3 photosynthesis and CAM metabolism. More information is also needed for Sedum species that utilize CAM to varying degrees on green roofs so that plant water use can be included in water balance equations that predict green roof performance. We monitored carbon dioxide exchange and water use by two common green roof species, Sedum album and Sedum kamtschaticum, for three weeks without water under strictly controlled environmental conditions in order to (1) compare daily carbon gain, rates of evapotranspiration (ET), and WUE for these two species and (2) assess the effect of CAM cycling on WUE with increasing drought for entire plant stands. Under similar environmental conditions, S. album and S. kamtschaticum canopies exhibited CAM metabolism to different extents with different ecophysiological consequences. S. kamtschaticum exhibited C3 photosynthesis for the first 14 days without water and outperformed S. album in terms of carbon gain and WUE above a volumetric water content (VWC) of 0.08m3m−3. S. album was the more drought tolerant species under the conditions of this experiment, gaining at least as much carbon and using water more efficiently at VWC below 0.08m3m−3. By switching from C3 to CAM at lower VWC, S. kamtschaticum had an overall greater WUE even though this species used as much if not more water overall compared to S. album. These data further support suggestions that a major adaptive function of CAM is to prolong plant-available water while maintaining a consistent, albeit low level of carbon gain. These findings also demonstrate why Sedum species should be treated independently of each other when considered in green roof designs.

Improved wheat performance with seed treatments under dry sowing on permanent raised beds

Two strategies for seeding irrigation are used for irrigated wheat. Wet sowing utilizes pre-sowing irrigation to germinate weed seeds and thus control weeds, followed by sowing. Dry sowing plants into dry soil that is irrigated soon afterward, resulting in higher soil moisture during germination and emergence than wet sowing. Field observations have indicated reduced emergence, plant stands and yield in dry compared to wet sowing on a Vertisol in northwestern Mexico. This disadvantage is more acute when dry sowing is conducted in permanent beds with residue retention (conservation agriculture) compared to the conventional system involving tillage with residue incorporation. To identify the causes of reduced plant stand and yield and examine control options, chemical seed treatment effects on durum wheat (Triticum durum Desf.) and bread wheat (Triticum aestivum L.) performance under wet and dry sowing were investigated over three seasons in a permanent bed system. Four seed treatments were applied: Control (no seed treatment); Carboxin+thiram+chlorothalonil (Vit-Dac; fungicides); Difenoconazole+mefenoxam (Dif-Mef; fungicides); and Thiamethoxam+difenoconazole+mefenoxam (TMX-Dif-Mef; insecticide and fungicides). Plant stands, root rot scores, normalized difference vegetative index (NDVI), and grain yield were determined. Under dry sowing, Dif-Mef and TMX-Dif-Mef increased plant stands by 87% and 104%, respectively, compared to Vit-Dac, and by 152% and 172%, respectively, compared to the control. Under dry sowing, TMX-Dif-Mef increased yield by 9.76% and 17.7% compared to Vit-Dac and the control, respectively. Bread and durum wheat were significantly different for both emergence and yield every growing season. Seed treatments effects were not significant under wet sowing. Treatment differences were not linked with root rot incidence later in the season. Several mechanistic hypotheses to explain the results were explored. TMX has been reported to alter genetic expression to enhance response to early season abiotic stresses, but this has not been reported for Dif-Mef. The different physical conditions during stand establishment, i.e. increased moisture and reduced temperature, under dry sowing compared to wet sowing, could have affected microbial populations which induced biological suppression of germination and/or emergence. Although more research is required to explain the underlying mechanism, wheat producers transitioning to a dry sowing system under conservation agriculture with permanent raised beds may avoid yield loss by utilization of a Dif-Mef or TMX-Dif-Mef seed treatment.

Genetic variation ofRhizoctonia solaniisolates from canola in Alberta, Canada

Zhou, Q. X., Hwang, S. F., Fu, H. T., Strelkov, S. E. and Gossen, B. D. 2014. Genetic variation of Rhizoctonia solani isolates from canola in Alberta, Canada. Can. J. Plant Sci. 94: 671–681. Seedling blight and root rot caused by Rhizoctonia solani often results in severe reductions in plant stands of canola (Brassica napus), a major oilseed crop in Canada. A total of 98 R. solani isolates were collected from central Alberta in 2009–2011 and analyzed for aggressiveness, anastomosis grouping and genetic variation. Seventy-six isolates (78%) were identified as AG2-1, three (3%) were AG2-2, one (1%) was AG4, one (1%) was AG8, and the anastomosis group of 17 isolates (17%) could not be determined. Isolates of AG2-1 were more aggressive on canola than the other isolates. The genetic variation among the 98 isolates was evaluated by sequence analysis of the ribosomal DNA internal transcribed spacers (ITS) and inter-simple sequence repeat (ISSR) markers. The isolates clustered into four groups based on a neighbor-joining tree of the ITS sequences using PAUP software, and four groups based on ISSR markers using the POPGENE program. The isolate composition of Group A in both clustering approaches was similar, and those isolates were weakly aggressive on canola seedlings. Although the identities of both groups differed, Groups B and C in both analyses included most of the AG2-1 isolates, which were highly aggressive on canola seedlings. Isolates with undetermined anastomosis grouping and isolates classified as AG4, AG8 or AG2-2 were also included in Groups B and C, but were generally less aggressive than the AG2-1 isolates. Group D consisted of only three isolates in both analyses, but their identities also differed. The results indicated that there was no association between Groups from the two molecular approaches.

Management legacy in the understory of North American mixed boreal regenerating stands

In the global context of planted forest expansion, the ability of artificially regenerated forests to stand-in for natural forests has become a central question for forest managers. Although few studies have examined their conservation potential, extensive planted forests cover a significant portion of North-American mixed boreal forests. We study the composition, functional assemblage, and vertical structure of understory communities in even-aged, mid-rotation, planted and naturally regenerated mixed boreal stands typical of extensive management (Québec, Canada). Our results show that more than 20years after harvest, species composition and functional assemblage still differ between stand types while understory structure does not. Planted stands exhibit a higher prevalence of traits and species typically associated with younger stands. Sensitive species such as Oxalis acetosella ssp. montana and Monotropa uniflora occurred less often in planted stands while the reverse was true for a portion of species with the potential to form a recalcitrant layer. This suggests that the understory of planted sites may require more time before reaching compositional and functional attributes comparable to those of naturally regenerated stands. This delayed maturation has implications for forest management, particularly under increased management intensity scenarios.

Up to 32 % yield increase with optimized spatial patterns of canola plant establishment in western Canada

Canola—Brassica napus L.—is an economically major crop in many parts of the world. The seed yield of canola is often limited by poor plant establishment. This issue is serious in areas with short growing seasons, such as western Canada, where canola plants have a limited time span plasticity to adapt and compensate for yield losses due to poor or non-uniform plant establishment. The effect of spatial patterns of canola plant stands on seed yield is actually unknown. Therefore, we studied the impacts of uniformity of plant stands on pod formation, seed set, and crop yield of canola. Field experiments were conducted at 16 site-years across the different soil-climatic zones of the Canadian prairies. At each site-year, the cultivar InVigor® 5440, a glufosinate-resistant hybrid, was sown at 100, 80, 60, 40, and 20 plants per square meter with uniform and non-uniform stands. We found that spatially uniform stands increased seed yield by up to 32 % at low-yielding sites and by up to 20 % at the high-yielding sites compared to non-uniform plant stands. This effect is mainly due to increased number of fertile pods. The yield increase was more pronounced with plant densities lower than 60 plants per square meter. Also, canola seed yield depended largely on plant survival during the hot summer and was less affected by the rate of seedling emergence. We conclude that canola yield can be increased by improving the uniformity of plant spatial distribution patterns in the field regardless of environmental conditions.

Vegetation Ecology of Coastal belt of Khejuri area of Purba Medinipur District with special reference to Hijli coast, West Bengal, India

The present article deals with vegetation admixed with populated shoreline elements along with some exotics which broadcast valid and successional change that can develop community as natural kind if managed by local people. The forest department (FD) is engaged with plantation of varied types of elements since two decades ago. The types of vegetation therefore three types as per the present situation either natural or plantation or preliminary natural followed by plantation type. This is due to the potential use of plants for different purposes either for fuel wood production or by other purpose they served. As a coastal line, all the managerial systems always associated with framing or making shelter belt or green belt for multipurpose reasons. The main theme was to sustain species in the present habitats and withstand there against natural calamities like devastating storms, heavy flood or to check the erosion which is annual and reoccurrence type. Therefore, the species planted there as artificial kind is Casuarina equisetifolia along with Acacia auriculoformis and a few strips of Eucalyptus for the sustenance of life. These species used for fuel wood production as well as for protection of the habitats in the upper strand. But the species planted along the shoreline are Sonneratia apetala, Avicennia officinalis, A. marina, A. alba and Prosopis juliflora. Other species they planted the same site are Acacia nilotica, but the species grew there with stunted growth and dynamics of stability was confined. Therefore, the types of special vegetation required here are to check the habitats as well as to develop biodiversity through the growing vegetation and reaching climax formation by halophytes. Though mixed pattern of vegetation found here are mesophytic, xerophytic, hydrophytic, halophytic, halophytic associate type and exotic introduced type. Most of the species grow there as plantation type except a few true halophytes near the High Tide (HT) and Low Tide (LT) area. Ground vegetation of Aleuropus lagopoide, Suaeda maritima and Suaeda monoica cover the disturbed area grazed by cattle which need immediate protection. A general discussion along with vegetation cover of true halophytes both in natural habitat and in plantation stands have been made for critical analysis as preliminary study. A total number of 16 plant species have been critically analyzed along with some potential plants with market demand have been discussed thoroughly. These will generate oxygen for categorically different researchers in the field of biology in near future to manage the ecosystem more usable than the present and will provoke sufficient path to generate income for eco-sustenance of life.

First Report of Fusarium cuneirostrum Causing Root Rot Disease in Dry Bean (Phaseolus vulgaris) in Canada.

Root rot is a major disease of dry bean and can cause significant yield reductions due to weakened root systems and poor plant stands. An in-depth study on root rot pathogen identification was conducted in 2011 in three commercial dry bean fields from the major production areas in Manitoba. Ten plants, sampled at each of four random sites within each field, were rated for disease severity. Twenty roots were processed for pathogen isolation and identification in the laboratory. Roots were cut into eight sections (~1 cm) and surface-sterilized in a laminar flow bench. Four root sections were placed on potato dextrose agar plates amended with 0.02% streptomycin sulfate (PDA-Strep) and four root sections were placed on peptone-pentachloronitrobenzene agar amended with 0.1% streptomycin sulfate and 0.012% neomycin sulfate. Afterward, 960 monosporic cultures were obtained representing 320 single spore isolates of potential root rot pathogens per commercial field. Common monosporic cultures from each field were subcultured on PDA-Strep and Spezieller Nährstoffarmer Agar (SNA) media. Based on morphological characteristics, 74 isolates were identified as Fusarium cuneirostrum (1). Colonies grew slowly on PDA-Strep with undulated margins, radial cream-grey mycelia, and conidia pustules with a cream-greyish pigmentation. Sporodochial conidia were falcate, mostly 5-septate, with a wedge shape and slightly protruding basal foot cell (56.3 to 71.8 × 4.6 to 6.2 μm on average). Species identity was confirmed for two isolates by sequencing the translation elongation factor 1 alpha (EF1-α) gene (2), the internal transcribed spacer (ITS) region (4), and the ribosomal intergenic spacer (IGS) (3) (GenBank Accession Nos. KF530848, KF530849, and KF025648 to 51). Sequence homology was compared using BLAST analysis and the FUSARIUM-ID database. The F. cuneirostrum isolates were deposited at the Canadian Collection of Fungal Cultures (DAOM 242540 and 242541). Pathogenicity screenings of two isolates was performed using sterilized seed of navy bean cv. Envoy. Seeds were germinated on moist filter paper for 3 days at 25°C and then inoculated by immersion in a prepared conidial suspension (2.5 × 105 conidia/ml) for 5 min. Seeds of the controls were immersed in sterile water. After inoculation, the germinated seeds were planted in 10-cm diameter pots, filled with sterile soilless mix (Sunshine #3). In the greenhouse, the experiment was arranged as a completely randomized design with three replicates with four germinated seeds per isolate, and was repeated twice. Disease assessment was performed 14 days after inoculation. Infected plants displayed dark brown lesions on the hypocotyl and primary root with a disease severity of 4 scored on a 0 to 5 scale. Fusarium cuneirostrum was re-isolated from roots of symptomatic plants. To our knowledge, this is the first report of F. cuneirostrum causing root rot of dry bean in Canada. It has been previously isolated from mung bean (Vigna radiata) in Ontario (1).

The Effect of Wide-Range Photosynthetic Active Radiations on Photosynthesis, Growth and Flowering of <i>Rosa sp.</i> and <i>Kalanchoe blossfeldiana</i>

Miniature roses (Rosa sp.) and Kalanchoe blossfeldiana were grown at photon flux densities (PFD) ranging from 60 to 670 μmol·m-2·s-1 (associated with a temperature gradient from 20.0°C to 24.0°C [TEMP1]) and from 50 to 370μmol·m-2-s-1 (associated with a temperature gradient from 22.5°C to 26.5°C [TEMP2]). The experiment was conducted in a greenhouse compartment at latitude 59° north in mid-winter. The daily photosynthetic active radiations (PAR) ranged from 4.3 to 48.2 and 3.6 to 26.6 mol·m-2·day-1 in the TEMP1 and TEMP2 treatments, respectively. Time until flowering in miniature roses decreased from about 50 to 35 days in the TEMP1 treatment and from 50 to 25 days in the TEMP2 treatment, when the PFD increased from 50 to 370μmol·m-2·s-1. In Kalanchoe time until flowering was decreased to the same extent (about 15 days) in both temperature treatments when PFD increased from 50 to 370 μmol·m-2·s-1. The number of flowers and the plant dry weight in miniature roses increased up to 300 – 400 μmol·m-2·s-1 PFD (21.6 - 28.8 mol·m-2 day-1 PAR), while flower stem fresh weight and plant dry weight in Kalanchoe increased up to 200 – 300 μmol·m-2·s-1 at TEMP1. Measurements of the diurnal carbon dioxide exchange rates (CER) in daylight in small plant stands of roses in summertime showed that CER was saturated at about 300 μmol·m-2·s-1 PFD at 370 μmol·mol-1 CO2 and at 400 – 500 μmol·m-2·s-1 PFD at 800 μmol·mol-1 CO2. For Kalanchoe similar results were obtained. Increasing the CO2 concentration from 370 to 800 μmol·mol-1 increased the CER in roses (48%) as well in Kalanchoe (69%). It was concluded that 15 to 20 mol·m-2·day-1 combined with about 24°C air temperature and high CO2 concentration will give a very good growth with lot of flowers within a short production time in miniature roses. For Kalanchoe 10 to 15 mol·m-2·day-1 combined with about 20°C and high CO2 produced a similar result.

Basal Area and Biomass Estimates of Loblolly Pine Stands Using L-band UAVSAR

Fully polarimetric L-band Synthetic Aperture Radar ( SAR ) backscatter was collected using NASA ’s Unmanned Aerial Vehicle ( UAV ) SAR and regressed with in situ measurements of basal area ( BA ) and above ground biomass ( AGB ) of mature loblolly pine stands in North Carolina. Results found HH polarization consistently displayed the lowest correlations where HV and VV exhibited the highest correlations in all groups for both BA and AGB . When plantation stands were analyzed separately (plantation versus natural), correlation improved signifi cantly for both BA (R 2 = 0.65, HV ) and AGB (R 2 = 0.66, VV ). Similarly, results improved when natural stands were analyzed separately resulting in the highest correlation for AGB (R 2 = 0.63, HV and VV ). Data decomposition using the Freeman 3-component model indicated that the relative low correlations were due to the saturation of the L-band backscatter across the majority of the study area.