Modelling the influence of weed competition on growth of young Pinus radiata. Development and parameterization of a hybrid model across an environmental gradient

2007 ◽  
Vol 37 (3) ◽  
pp. 607-616 ◽  
Author(s):  
Michael S. Watt ◽  
Mark O. Kimberley ◽  
Graham Coker ◽  
Brian Richardson ◽  
George Estcourt
Keyword(s):  
Tree Growth ◽  
Environmental Gradient ◽  
Root Zone ◽  
Weed Competition ◽  
Diameter Growth ◽  
Weed Species ◽  
Light Competition ◽  
Potential Growth ◽  
Diverse Range ◽  
Using Data

A hybrid tree growth model sensitive to competition from a diverse range of weed species was developed and validated using data from a nationwide series of 24 plots covering an extensive environmental gradient. Tree growth in plots with weeds over the first 3 years following establishment was predicted by reducing potential growth from an empirically determined optimum rate for the site (weed free) using a competition modifier, which accounts for the degree of weed competition for both light and water availability. Diameter growth of trees in plots with weeds was initially predicted by including a light competition modifier into the model developed for weed-free plots. This model accounted for 87% of the variance in diameter of trees growing with weeds. Although inclusion of this modifier provided unbiased predictions of tree diameter growth on wet sites, model predictions overestimated diameter growth on dryland sites by on average 11%. Addition of a competition index for water based on treatment differences in average fractional available root-zone volumetric water content significantly (p < 0.001) improved the precision (R2 = 0.96) and reduced the bias of the overall model. A cross validation of this final model indicated it was unbiased and relatively accurate (R2 = 0.95).

Testing a juvenile tree growth model sensitive to competition from weeds, using Pinus radiata at two contrasting sites in New Zealand

2004 ◽  
Vol 34 (10) ◽  
pp. 1985-1992 ◽  
Author(s):  
Michael S Watt ◽  
Mark O Kimberley ◽  
Brian Richardson ◽  
David Whitehead ◽  
Euan G Mason
Keyword(s):  
Growth Model ◽  
Tree Growth ◽  
Pinus Radiata ◽  
Root Zone ◽  
Light Availability ◽  
Early Summer ◽  
Diameter Growth ◽  
Light Competition ◽  
Potential Growth ◽  
Tree Growth Model

A juvenile tree growth model sensitive to competition from weeds was developed and tested. Tree growth is predicted by reducing potential growth from an empirically determined optimum rate for the site (weed-free) using a seasonally estimated competition modifier, which accounts for the degree of weed competition for both water and light availability. The model was tested against data from a field trial at a dryland site, where juvenile Pinus radiata D. Don trees were grown with and without competition from the woody weed broom (Cytisus scoparius (L.) Link). For trees in plots without broom, seasonal fluctuations in growth were adequately modelled by a single-term Fourier series, which showed that maximum rates of diameter growth occurred during early summer. Diameter growth of trees in plots with broom was initially predicted by including a light-competition modifier into the model developed for weed-free plots on sites not subject to growth-limiting seasonal water deficit. Although the light modifier reduced growth from the weed-free state by 12% over the first year and 25% over the second year, modelled values still significantly exceeded measured diameter growth. To account for this overprediction a competition modifier based on modelled root-zone water storage was added into the model. Predictions of diameter growth using this modified model corresponded closely to measured diameter growth in both treatments.

scholarly journals Precommercial Thinning Increases Spruce Yields in Boreal Mixedwoods in Alberta, Canada

Forests ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 412
Author(s):  
Ivan Bjelanovic ◽  
Phil Comeau ◽  
Sharon Meredith ◽  
Brian Roth
Keyword(s):  
Growth Models ◽  
Growth And Yield ◽  
Diameter Growth ◽  
Growth Responses ◽  
Projection System ◽  
Precommercial Thinning ◽  
Thinning Intensity ◽  
Boreal Mixedwoods ◽  
Using Data ◽  
Mixedwood Stands

A few studies in young mixedwood stands demonstrate that precommercial thinning of aspen at early ages can improve the growth of spruce and increase stand resilience to drought. However, information on tree and stand responses to thinning in older mixedwood stands is lacking. To address this need, a study was initiated in 2008 in Alberta, Canada in 14 boreal mixedwood stands (seven each at ages 17 and 22). This study investigated growth responses following thinning of aspen to five densities (0, 1000, 2500, 5000 stems ha−1 and unthinned (control)). Measurements were collected in the year of establishment, and three and eight years later. Mortality of aspen in the unthinned plots was greater than in the thinned plots which were not significantly different amongst each other. Eight years following treatment, aspen diameter was positively influenced by thinning, while there was no effect on aspen height. The density of aspen had no significant effect on the survival of planted spruce. Spruce height and diameter growth increased with both aspen thinning intensity and time since treatment. Differentiation among treatments in spruce diameter growth was evident three years from treatment, while differentiation in height was not significant until eight years following treatment. Yield projections using two growth models (Mixedwood Growth Model (MGM) and Growth and Yield Projection System (GYPSY)) were initialized using data from the year eight re-measurements. Results indicate that heavy precommercial aspen thinning (to ~1000 aspen crop trees ha−1) can result in an increase in conifer merchantable volume without reducing aspen volume at the time of harvest. However, light to moderate thinning (to ~2500 aspen stems ha−1 or higher), is unlikely to result in gains in either deciduous or conifer merchantable harvest volume over those of unthinned stands.

scholarly journals Weed Interference Affects Dry Bean Yield and Growth

2012 ◽  
Vol 4 (3) ◽  
pp. 70-75 ◽  
Author(s):  
Hossein GHAMARI ◽  
Goudarz AHMADVAND
Keyword(s):  
Chenopodium Album ◽  
Growing Season ◽  
Amaranthus Retroflexus ◽  
Growth And Yield ◽  
Weed Competition ◽  
Weed Species ◽  
Dry Bean ◽  
Logistic Equations ◽  
Weed Interference ◽  
Minimum Number

Dry bean is one of the most important pulse crops in Iran. Field study was conducted in 2011 to evaluate effects of weed competition from a natural flora on growth and yield of dry bean (Phaseolus vulgaris L.). The treatments consisted of weed infestation and weed removal periods (10, 20, 30, 40 and 50 days) after crop emergence. Control plots kept weed-infested and weed-free throughout growing season. To assess the weed competition effect on crop characteristics, Richards, Gompertz and logistic equations were fitted to the data. The most abundant weed species were Chenopodium album and Amaranthus retroflexus. Increase in duration of weed interference decreased the stem height of dry bean. At the end of the growing season, dry bean was 20 cm taller in season-long weed-free treatment compared to the season-long weed-infested treatment. As the number of days of weed interference increased, a declining trend of LAI and number of pods was observed. The minimum number of pods was obtained in season-long weed-infested treatment (5.01 pods/plant). Weed interference during the whole growing season, caused a 60% reduction in yield. Considering 5% and 10% acceptable yield lost, the critical period of weed competition was determined from 20 to 68 and 23 to 55 days after planting (DAE), respectively.

scholarly journals Effect of duration of weed competition and weed control on the yield of Indian spinach

1970 ◽  
Vol 33 (4) ◽  
pp. 623-629 ◽  
Author(s):  
MSA Khan ◽  
MA Hossain ◽  
M Nurul Islam ◽  
SN Mahfuza ◽  
MK Uddin
Keyword(s):  
Weed Management ◽  
Critical Period ◽  
Field Experiments ◽  
Agricultural Research ◽  
Cyperus Rotundus ◽  
Weed Competition ◽  
Weed Species ◽  
Maximum Benefit ◽  
Hand Weeding ◽  
Crop Weed Competition

Field experiments were conducted at the research farm of Bangladesh Agricultural Research Institute, Joydebpur during kharif-1 (March to July) seasons of 2005 and 2006 to identify the critical period of crop-weed competition for Indian spinach. Major weed species were Paspalurn commersoni, Echinochlaa crusgalli. Lie nv/nc india. Cyanotis axillaris and Cyperus rotundus. The lowest weed dry matter was 76.3 g m-2 in 2005 and l01.60 g m-2 in 2006 from the plots weeded up to 40 days after transplanting (DAT). The highest yields were obtained (74.82 t ha in 2005 and 48.48 t ha in 2006) from the weed free plots. The fresh yield of Indian spinach did not vary among no weeding upto 20, 30 and 40 DAT in 2006. But weeded plot upto 30 and 40 DAT produced identical yield in 2005. Maximum BCR (4.52) was obtained from weeded plots upto 30 DAT in 2005 but BCR (2.60) was same from weeded upto 30 and 40 DA F in 2006. On an average, highest BCR (3.55) was recorded from weeding upto 30 DAT. Results revealed that the critical period of crop weed competition lies between 20 and 30 DAT and two times hand weeding would be necessary within 30 DAT for maximum benefit. Key Words: Crop-weed competitions, critical period, weed management and Indian spinach. doi: 10.3329/bjar.v33i4.2306 Bangladesh J. Agril. Res. 33(4) : 623-629, December 2008

scholarly journals Predicting Yield Losses in Rice Mixed-Weed Species Infestations in California

Weed Science ◽  
2016 ◽  
Vol 65 (1) ◽  
pp. 61-72 ◽  
Author(s):  
Whitney B. Brim-DeForest ◽  
Kassim Al-Khatib ◽  
Albert J Fischer
Keyword(s):  
Yield Loss ◽  
Information Criterion ◽  
Average Error ◽  
Canopy Closure ◽  
Weed Species ◽  
Major Barrier ◽  
Combined Models ◽  
Relative Cover ◽  
Predicted Values ◽  
Using Data

Although many pests constrain rice production, weeds are considered to be the major barrier to achieving optimal yields. A predictive model based on naturally occurring mixed-species infestations in the field would enable growers to target the specific weed group that is the greatest contributor to yield loss, but as of now no such models are available. In 2013 and 2014, two empirical hyperbolic models were tested using the relative cover at canopy closure of groups of weed species as independent variables: grasses, sedges, broadleaves, grasses and sedges combined, grasses and broadleaves combined, and all weed species combined. Models were calibrated using data from experiments conducted at the California Rice Experiment Station, in Biggs, CA, and validated across four sites over 2 years, for a total of 7 site-year combinations. Of the three major weed groups, grasses, sedges, and broadleaves, the only groups positively related to yield loss in the multispecies infestation were grasses. At the model calibration site, grasses and sedges combined best predicted yield loss (corrected Akaike information criterion [AICc]=−21.5) in 2013, and grasses alone best predicted yield loss (AICc=−19.0) in 2014. Across the validation sites, the model using grasses and sedges combined was the best predictor in 5 out of 7 site-years. Accuracy of the predicted values at the model validation sites ranged from 6% mean average error to 17% mean average error. No single model and set of parameters accurately predicted losses across all years and locations, but relative cover of grasses and sedges combined at canopy closure was the best estimate over the most sites and years.

Crop protection.

2021 ◽  
Author(s):  
Lynette Morgan
Keyword(s):  
Crop Protection ◽  
Early Agriculture ◽  
Weed Species ◽  
Diverse Range ◽  
Pests And Diseases ◽  
Vertebrate Pests ◽  
The Many ◽  
Potential Food ◽  
Vast Range

Abstract Crop protection procedures have existed since the first attempts at early agriculture. While cultivation of a vast range of crops is vital our existence, these same plants are highly attractive to a diverse range of invertebrate and vertebrate pests, and disease pathogens. Competition from weed species also occurs on a worldwide scale. Even with the many forms of crop protection practised today, losses due to pests and diseases range from 10 to 90%, with an average of 35-40% for all potential food and fibre crops (Peshin, 2002).

The Structure of Weed Communities in Saskatchewan Fields

Weed Science ◽  
1987 ◽  
Vol 35 (3) ◽  
pp. 348-355 ◽  
Author(s):  
Mark R. T. Dale ◽  
A. Gordon Thomas
Keyword(s):  
Linum Usitatissimum ◽  
Brassica Campestris ◽  
Common Species ◽  
Weed Species ◽  
Oilseed Crops ◽  
Weed Communities ◽  
Using Data ◽  
And Cluster Analysis ◽  
Natural Groups ◽  
Different Soils

This paper describes the communities of weeds in cereal and oilseed crops in Saskatchewan, using data collected in a 4-yr survey that sampled more than 400 fields. The survey data for the 40 most common weeds were analyzed in an attempt to distinguish natural groups of weed species and to compare the weed communities associated with the different crops and with different soils. The crops were barley (Hordeum vulgareL.), flax (Linum usitatissimumL.), oats (Avena sativaL.), rape (Brassica campestrisL.,Brassica napusL.), and wheat (Triticum aestivumL.). Phytosociological association and cluster analysis indicated that the associations of the weed species were more or less independent of the crop, although some differences existed and were determined more by soil or the associated climate. The 40 most common species were divided into three groups related to the soil and climatic subregions of the province.

scholarly journals Green manure and phosphorus fertilization affect weed community composition and crop/weed competition in organic maize

2019 ◽  
Vol 35 (5) ◽  
pp. 493-502 ◽  
Author(s):  
Stefano Carlesi ◽  
Federica Bigongiali ◽  
Daniele Antichi ◽  
Corrado Ciaccia ◽  
Fabio Tittarelli ◽  
...  
Keyword(s):  
Community Composition ◽  
Green Manure ◽  
Competitive Ability ◽  
Early Growth ◽  
Phosphorus Fertilization ◽  
Weed Competition ◽  
Weed Species ◽  
Green Manuring ◽  
Density And Biomass ◽  
Crop Weed Competition

AbstractGreen manure and compost-enriched in phosphorus can promote the sustainability of cropping systems by increasing soil fertility over the long term. They can also be used to manage crop/weed interactions, a key element in guaranteeing an appropriate level of satisfactory crop yields. We studied how green manuring with hairy vetch (Vicia villosaRoth.) and the application of different types of phosphorous-enriched compost affect weed/maize (Zea maysL.) interactions in an organic stockless Mediterranean agroecosystem for two consecutive dry years. Green manure stimulated the expression of maize traits related to a higher competitive ability against weeds, such as early growth, height and leaf area index, while the effect of compost was less clear. Regarding crop/weed competition, both green manuring and a phosphorus-enriched compost application gave a significant advantage to maize. Neither green manure nor compost increased total weed density and biomass compared to the control. Green manuring significantly affected the weed community composition. The relative density of ruderal and competitive-ruderal species (according to Grime's classification) was higher in plots where the green manure was applied. The use of green manure, together with novel composting techniques, significantly affected crop/weed competitive interactions, favoring maize, but also creating favorable conditions for unwanted weed species such as competitive-ruderals. Increasing nitrogen availability in the early growth stages of maize through green manuring can increase crop competitive ability. However, this may not suffice to preserve the system from future weed problems, should potentially detrimental species be selected. Dedicated strategies for the control of emerging weed species may thus be needed.

scholarly journals Weeds of Paddy Field at Kirtipur, Kathmandu

1970 ◽  
Vol 5 (5) ◽  
pp. 100-106 ◽  
Author(s):  
Sailaza Manandhar ◽  
Bharat B Shrestha ◽  
Hari D Lekhak
Keyword(s):  
Grain Yield ◽  
Seedling Growth ◽  
Shoot Elongation ◽  
Weed Competition ◽  
Root Extract ◽  
Aqueous Extracts ◽  
Weed Species ◽  
Ageratum Conyzoides ◽  
Straw Yield ◽  
Crop Weed Competition

Paddy (Oryza sativa L. var. Taiching-127) fields of Kirtipur, central Nepal, were studied to evaluate the effects of weeds on crop yield during June to October 2003. Weed community was recorded in permanently marked plots (2 x 2 m2 each), and grain and straw yields were measured. The effect of aqueous extracts (2 to 10%) of leaf, stem and root of dominant weeds (Echinochloa colona, E. crusgalli, Cyperus iria and Ageratum conyzoides) on germination and seedling growth of the paddy (Taiching-127) was examined in the laboratory. Altogether 52 weed species (27 dicot and 25 monocot) belonging to 32 genera and 15 families infested the paddy. The maximum weed density was observed in September (105 pl/m2). There was significant reduction in straw and grain yield of paddy in weedy plots and negative correlation between weed species richness and straw yield. Crop weed competition reduced straw yield by 13% to 38% and grain yield by 25% to 47%. Weed growth changed pH and reduced soil nitrogen and phosphorus content. Aqueous extracts of root, stem and leaf of dominant weeds (Echinochloa colona, E. crus-galli, Cyperus iria and Ageratum conyzoides) showed a weak effect on seeds germination however most of them had inhibitory effect on root and shoot elongation of paddy seedlings. Root elongation was more sensitive to allelopathic inhibition than shoot elongation. Stem extract of these weeds showed higher inhibition on seedling growth of paddy than leaf and root extract except in Ageratum conyzoides in which root extract showed highest inhibition. Keywords: Allelopathy; Crop-weed competition; Soil nutrients; Germination; Grain yield. DOI: 10.3126/sw.v5i5.2665 Scientific World, Vol. 5, No. 5, July 2007 100-106

scholarly journals Increased Individual Tree Growth Maintains Stand Volume Growth after B-Level Thinning and Crop-Tree Management in Mature Oak Stands

2019 ◽  
Vol 65 (6) ◽  
pp. 784-795
Author(s):  
Jeffrey S Ward ◽  
Jessica Wikle
Keyword(s):  
Tree Growth ◽  
Growth Response ◽  
Volume Growth ◽  
Diameter Growth ◽  
Red Oak ◽  
Individual Tree ◽  
Stand Volume ◽  
Tree Management ◽  
Individual Tree Growth ◽  
Partial Release

AbstractSix study areas were established in 80–125-year-old upland oak stands on average sites to compare stand and individual tree growth response following two active treatments (B-level thinning, crop tree) with an unmanaged control. Initial stocking of 104 percent was reduced to 62 percent and 60 percent on the B-level and crop-tree-management plots, respectively. Approximately 7,200 board feet per acre (International ¼) were harvested on the actively managed plots with upland oaks accounting for 81 percent of pre- and 86 percent of residual stand. Eleven-year diameter and volume growth of oak sawtimber trees was greater on actively managed plots. Growth response increased with degree of release and was maintained for the length of the study. Because of the increased individual tree growth of oaks in response to release, stand volume growth of oak sawtimber did not differ between treatments. In contrast to an 11-year decline of poletimber stocking on unmanaged plots, poletimber stocking increased on managed plots as diameter growth increased in response to partial release. This may increase difficulty of regenerating oak in the future. For those mature red oak stands where traditional regeneration prescriptions will not be implemented or will be delayed, commercial harvests can be conducted without compromising stand volume growth of oak.

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