Simply put, allelopathy refers to an ecological phenomenon of plant-plant interference through release of organic chemicals (allelochemicals) in the environment. These chemicals can be directly and ...continuously released by the donor plants in their immediate environment as volatiles in the air or root exudates in soil or they can be the microbial degradation products of plant residues. The chemicals may interfere with survival and growth of neighboring or succeeding plants. Black walnut, eucalyptus, sunflower, sorghum, sesame and alfalfa are common examples of plants with allelopathic property as well as some staple crops such as rice, wheat, barley and sorghum. Plants can emit chemicals that also discourage insects and pathogens. To maintain sustained productivity, knowledge of this form of plant interference on other plants and on disease causing organisms has been used in agriculture since prehistoric time by manipulating cropping pattern and sequence such as mixed cropping and crop rotation. However, use of numerous agrochemicals including a wide range of herbicides, pesticides, fertilizers and genetically modified high yielding crops has become the characteristic feature of modern industrial agriculture. Not only the sustainability of crop yield is called into question in this form of agriculture, the extensive long-term and often irreversible environmental degradation including ground water contamination and food safety associated with industrial agriculture are now of serious concern worldwide. The objective is to report on the latest advances in allelopathy by inviting leading scientists to contribute in specific fields. The volume is organized under three major subsections: History of allelopathy, Allelochemicals, allelopathic mechanisms, and bioassays, and Application of allelopathy in agriculture and forestry. An emphasis is place on methodology and application, making it a truly practical reference.
In eastern Canada, alternation of wildfire regime due to fire suppression creates alternate vegetation states converting black spruce forest to heath and shrub savannah (SS). We compared the ...taxonomic diversity (TD) and functional diversity (FD) of post-fire forest, heath, and SS alternate states to determine if community FD can explain their persistence. We hypothesized that (i) species diversity (TD and FD) would be the highest in forest followed by SS and heath due to decreased interspecific competition and niche differentiation, (ii) differences between TD and FD indices would be greater in communities with high TD in forest due to high trait differentiation and richness, and (iii) changes in community trait values would indicate niche limitations and resource availability. We conducted this study in Terra Nova National Park, Newfoundland, Canada. We calculated functional dispersion (alpha FD), functional pairwise dissimilarity (beta FD), Shannon’s diversity (alpha TD), and Bray–Curtis dissimilarity (beta TD) from species cover. We used five functional traits (specific root length, specific leaf area, leaf dry matter content, height, and seed mass) related to nutrient acquisition, productivity, and growth. We found lower beta diversity in forest than heath and SS; forest also had higher species diversity and greater breadth in niche space utilization. SS was functionally similar to heath but lower than forest in functional dispersion and functional divergence. It had the highest functional richness and evenness. There was no difference in functional evenness between forest and heath. Functional beta diversity was the highest in forest, and did not differ between heath and SS. Resource acquisition and availability was the greatest in forest and the lowest in heath. We suspect that this might be due to forest having the highest functional trait turnover and niche utilization. We conclude that alternate vegetation states originating from alterations to the natural fire regime negatively impact ecosystem function.
To understand impacts of post-disturbance assembly mechanisms on the functional diversity (FD) of plant communities, it is necessary to determine how the environment drives their functional trait ...composition. In the boreal forest, post-fire abiotic filters may control community assembly by selecting plants with specific traits. Ericaceous heaths are characterized by low FD and are thought to be subject to such filters. We hypothesized that soil parameters select for a specific suite of traits and act as a secondary abiotic filter in post-fire ericaceous heath and contribute to the observed reduction of FD. We measured six soil parameters, five functional traits, and plant species abundances in eight post-fire heath and four regenerating forest sites in Eastern Canada. We conducted a combined analysis of RLQ (R-table Linked to Q-table) and fourth-corner methods to examine the links between plant traits and plot-level soil parameters, mediated by species abundances. Only below ground traits were significantly linked to soil variables. Specific root length and ericoid mycorrhizal associations were negatively linked to total soil nitrogen, available ammonium, and pH. Post-fire heath soils favour a specific suite of species traits. Only a portion of the regional species pool possesses the above-mentioned traits, and when they are favoured by habitat conditions, they assemble into a community with low FD. The novelty of our study is here we show how the relationship between traits and soil chemistry can act as a secondary filter and exert community-level trait changes responsible for the low functional diversity observed in heaths.
The effect of intensive human intervention, poor socio-economic conditions and little knowledge on mangrove ecology pose enormous challenges for mangrove restoration in Southeast Asia. We present a ...framework for tropical mangrove restoration. Our proposed restoration framework addresses the ecology, economy and social issues simultaneously by considering the causes of mangrove degradation. We provide a step by step guideline for its restoration. We argue that although, ecological issues are of prime importance, economic and social issues must be considered in the restoration plan in order for it to be successful. Since mangrove ecology is not adequately studied in this region, local ecological knowledge can be used to fill the baseline information gaps. Unwanted human disturbance can be minimized by encouraging community participation. This can be ensured and sustained by facilitating the livelihood of the coastal community. We translated the restoration paradigm into a readily available practical guideline for the executors of the plans. We provide an example of mangrove restoration project that is closely related to our proposed framework. We are optimistic that this framework has the potential for universal application with necessary adjustments.
Drainage is known to reduce carbon sequestration in peatlands, but its effect on the stability of carbon pool and changes in recalcitrant organic carbon fractions remain relatively unknown, ...especially in temperate montane peatlands. We investigated the effect of drainage on physicochemical properties and organic carbon fractions of six peat cores from drained and near-pristine areas of Baijianghe peatland, NE China, basing on
210
Pb and AMS
14
C dating. The vegetation biomass and biomass-C sequestration were also measured in both areas. The loss of total soil carbon accumulation due to drainage was 7.5 kg m
−2
(− 25%), equivalent to a complete consumption of carbon accumulated for nearly 170 years in the near-pristine area. Vegetation succession after drainage had a little positive effect on ecosystem carbon sequestration, with an increase of 0.26 kg m
−2
, which compensated for only 3.5% of the peat soil carbon loss. Notably, over 80% of the total carbon loss after drainage was attributed to the loss of the recalcitrant carbon fraction. The study emphasizes the crucial impact of drainage on carbon sequestration in temperate peatlands. Our findings suggest that continuous water table drawdown induced by drainage, together with drought driven by climate warming, will further reduce carbon sequestration in drained peatlands. There is an urgent need to restore hydrology of peatlands in order to mitigate the long-lasting negative effect of drainage.
An array of 90times90 active pixel sensors (APS) with pixel-level embedded differencing and comparison is presented. The nMOS-only 6T 2C 25 mum times 25 mum pixel provides both analog readout of ...pixel intensity and a digital flag indicating temporal change at variable thresholds. Computation is performed through a pixel-level capacitively coupled comparator which also functions as analog-to-digital converter. The chip, fabricated in a 0.5 mum 3M2P CMOS, process consumes 4.2 mW of power while operating at 30 fps. Change sensitivity is 2.1% at an illumination of 1.7 W/cm 2 . Gating of raster-scanned pixel output by change detection typically produces a 20-fold compression in the data stream, depending on image conditions and reconstruction quality set by the change detection threshold.
In the present study, Aluminium metal matrix composite with Al6061 matrix and Graphite (5-20µm) particulate reinforcement of varying composition (2-8wt.%) were prepared by stir casting technique. ...Significant improvement in tensile strength and ductility was noticed as the weight percent of Gr increases in as cast Al6061- Gr composites. The cast composites have been subjected to annealing treatment at a temperature of 400°C for 4 hours to homogenize the microstructure. The specimens have been prepared from these composites for Equal Channel Angular Pressing (ECAP). The ECAP process was carried out at room temperature using a die with channel angle of 120o and Bc route was adopted for successive passes. The effect of ECAP on the microstructure and mechanical properties of Al6061 –Gr composites were evaluated. After ECAP process, the sizes of the reinforcement particles are not changed but they were distributed uniformly in the matrix. In addition, a significant reduction in the grain size of the matrix alloy was observed. The hardness and tension tests were conducted at room temperature as per ASTM standards. The results are compared with the base Al6061 material and as cast Al6061-Gr composites. There is a significant improvement in the hardness and the Ultimate tensile strength of ECAP processed composites.
Allelopathic interference of
Kalmia angustifolia (Ericaceae) to the growth and establishment of black spruce (
Picea mariana) has been suggested by several authors. The greenhouse studies suggested ...that
Kalmia has potential for nutrient interference. However, these studies do not eliminate probable involvement of allelopathy. Field studies indicate that soils associated with
Kalmia were nutrient-poor particularly for nitrogen, phosphorus, iron, and manganese, and support the hypothesis that
Kalmia has dominated microsites that were nutrient-poor prior to its colonization. The questions addressed in this paper are (i) Is
Kalmia interference to black spruce growth explained by allelopathy? (ii) Can
Kalmia–black spruce allelochemical interactions be better explained by ecosystem-level approach to allelochemicals rather than disturbance-related regeneration ecology of
Kalmia? At present, we do not have compelling direct evidence to support allelopathy as a mechanism of
Kalmia interference to black spruce. However, organic molecules released from
Kalmia into the environment may influence soil mineralization, mycorrhizae, nutrient dynamics, and soil microbial ecology. We hypothesize that synergistic interaction of ecological factors may better explain the interference mechanism of
Kalmia.
Blueberries are eaten fresh or after storing at room temperature, refrigerator or freezer but little is known about changes in food values of wild blueberries due to harvest dates and storage ...conditions. The aim of this study was to investigate the effect of harvest date and storage conditions of wild blueberries on berry quality and health related chemistry. We analyzed
Vaccinium angustifolium
,
V. angustifolium
var.
nigrum
, and
V. myrtilloides
native to NW Ontario, Canada harvested early and late in the season for total phenol (TP), anthocyanin contents (AC), and soluble solids to titratable acidity ratio storing at room temperature, refrigerator and freezer temperature. We also determined their antioxidant content and activity (ORAC). Late harvest and low temperature storage significantly increased TP and AC for most genotypes. In
V. myrtilloides
TP increased by 50, 44 and 45% respectively at late harvest, 14 days refrigerator and 90 days freezer storage. It also had significantly higher ORAC (22 and 33%) than the other two genotypes. Wild blueberry pickers and consumers can optimize health benefits and quality attributes of blueberries by customizing harvest protocols and choice of cultivar and storage in household fridge and freezer. Blueberry storage, at household fridge and freezer temperature, does not reduce its health benefits.
Post-fire nutrient flushes are an important precursor to secondary succession in fire-driven boreal forest. We studied the magnitude of changes in post-fire soil nutrient status across a ...chronosequence of ericaceous shrub-dominated boreal forest stands in eastern Newfoundland, Canada. The chronosequence comprised nine stands burned between 1 and 38 years prior to the study. These sites have resisted tree reestablishment following forest fire-induced mortality of black spruce and a concomitant increase in dominance of the ericaceous dwarf shrub Kalmia angustifolia L. Our objectives were: (1) to identify the factors driving soil nutrient status in these post-fire stands dominated by ericaceous plants, and (2) to test hypotheses that specific relationships exist among environmental factors, dominant vegetation and indicators of soil nutrient status. Macronutrients such as NH ₄ ⁺ , total organic N and mineral soil P concentrations showed non-linear declines with time since fire. These parameters were also negatively associated with cover of ericaceous plants. Potential phytotoxins such as total phenolics and aluminium concentrations increased with increasing cover of K. angustifolia. Variability in net ammonification, total P and total phenolic acids in organic soils were strongly related to ericaceous dominance even when the effect of time since fire was partialled out using regression analysis. These findings suggest a strong capacity for ericaceous vegetation to have top-down effects on soil chemical property particularly in the organic horizon with the increase in its post-fire dominance.
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