A chronosequence analysis of forest recovery on abandoned agricultural fields in Nicaragua

Species composition, diversity and population structure of woody species recovered on three abandoned agricultural fields after 4, 9 and 14 years were characterized. Seedlings, saplings/poles and mature trees were identified and counted in 70 plots of 100 m^2 in each abandoned site. A total of 13, 29 and 22 families represented by 17, 48 and 44 species were registered in 4-, 9- and 14-year-old stands, respectively. There was a shift in dominant species across successional stages. Lonchocarpus acuminatus had the highest importance value in the 4-year old stand, whereas, Myrospermun frutescens, Guazurna ulmifolia and Cordia alliodora had the highest importance value in the 9-year-old-stand and Caesaeria corymbosa, Muntingia calabura, Gliricidia sepium and Tabebuia rosea in the 14-year-old stand. The total stem density increased from 5011 to 9631 individuals per hectare as the age of abandonment increased from 4 to 14 years. The total basal area of individuals _〉 I cm d.b.h, also increased with the age of abandonment. Overall, small individuals （〈 10 cm dbh） contributed to more than half of the total basal area. Species diversity was the highest in the 9-year old stand followed by 14- and 4-year-old stands. We concluded that floristic composition of secondary forests recovers rapidly to the mature forest level compared to structural attributes, which is consistent with the general successional trajectories of tropical dry forest.

Measurement of HONO flux using the aerodynamic gradient method over an agricultural field in the Huaihe River Basin,China

To investigate nitrous acid(HONO)levels and potential HONO sources above crop rotation fields.The HONO fluxes were measured by the aerodynamic gradient(AG)method from 14 December 2019 to 2 January 2020 over an agricultural field in the Huaihe River Basin.The ambient HONO levels were measured at two different heights(0.15 and 1.5 m),showing a typical diurnal cycle with low daytime levels and high nighttime levels.The upward HONO fluxes were mostly observed during the day,whereas deposition dominated at night.The diurnal variation of HONO flux followed solar radiation,with a noontime maximum of 0.2 nmol/(m^(2)·sec).The average upward HONO flux of 0.06±0.17 nmol/(m^(2)·sec)indicated that the agricultural field was a net source for atmospheric HONO.The higher HONO/NO_(2)ratio and NO_(2)-to-HONO conversion rate close to the surface suggested that nocturnal HONO was formed and released near the ground.The unknown HONO source was derived from the daytime HONO budget analysis,with an average strength of 0.31 ppbV/hr at noontime.The surface HONO flux,which was highly correlated with the photolysis frequency J(NO_(2))(R^(2)=0.925)and the product of J(NO_(2))×NO_(2)(R^(2)=0.840),accounted for∼23%of unknown daytime HONO source.The significant correlation between HONO fluxes and J(NO_(2))suggests a light-driven HONO formation mechanism responsible for the surface HONO flux during daytime.

An Adaptive Edge Detection Algorithm for Weed Image Analysis

Weeds are one of the utmost damaging agricultural annoyers that have a major influence on crops.Weeds have the responsibility to get higher production costs due to the waste of crops and also have a major influence on the worldwide agricultural economy.The significance of such concern got motivation in the research community to explore the usage of technology for the detection of weeds at early stages that support farmers in agricultural fields.Some weed methods have been proposed for these fields;however,these algorithms still have challenges as they were implemented against controlled environments.Therefore,in this paper,a weed image analysis approach has been proposed for the system of weed classification.In this system,for preprocessing,a Homomorphic filter is exploited to diminish the environmental factors.While,for feature extraction,an adaptive feature extraction method is proposed that exploited edge detection.The proposed technique estimates the directions of the edges while accounting for non-maximum suppression.This method has several benefits,including its ease of use and ability to extend to other types of features.Typically,low-level details in the formof features are extracted to identify weeds,and additional techniques for detecting cultured weeds are utilized if necessary.In the processing of weed images,certain edges may be verified as a footstep function,and our technique may outperform other operators such as gradient operators.The relevant details are extracted to generate a feature vector that is further given to a classifier for weed identification.Finally,the features have been used in logistic regression for weed classification.The model was assessed against logistic regression that accurately identified different kinds of weed images in naturalistic domains.The proposed approach attained weighted average recognition of 98.5%against the weed images dataset.Hence,it is assumed that the proposed approach might help in the weed classification system to accurately identify narrow and broad weeds taken captured in real environments.

尼加拉瓜废弃农田的森林恢复年代序列分析

Species composition, diversity and population structure of woody species recovered on three abandoned agricultural fields after 4, 9 and 14 years were characterized. Seedlings, saplings/poles and mature trees were identified and counted in 70 plots of 100 m2 in each abandoned site. A total of 13, 29 and 22 families represented by 17, 48 and 44 species were registered in 4-, 9-and 14-year-old stands, respectively. There was a shift in dominant species across successional stages. Lonchocarpus acuminatus had the highest importance value in the 4-year old stand, whereas, Myrospermun frutescens, Guazuma ulmifolia and Cordia alliodora had the highest importance value in the 9-year-old-stand and Caesaeria corymbosa, Muntingia calabura, Gliricidia sepium and Tabebuia rosea in the 14-year-old stand. The total stem density increased from 5011 to 9631 individuals per hectare as the age of abandonment increased from 4 to 14 years. The total basal area of individuals ≥ 1cm d.b.h. also increased with the age of abandonment. Overall, small individuals (< 10 cm dbh) contributed to more than half of the total basal area. Species diversity was the highest in the 9-year old stand followed by 14-and 4-year-old stands. We concluded that floristic composition of secondary forests recovers rapidly to the mature forest level compared to structural attributes, which is consistent with the general successional trajectories of tropical dry forest.

Distribution and Abundance of <i>Parthenium hysterophorus</i>L. in Metekel Zone, Northwest Ethiopia

Parthenium hysterophorus L. is a harmful invasive weed to plant biodiversity and human health. It is native to American tropics and first introduced to Ethiopia in the 1970s. Today, it is widely distributed across the country and severely affecting the biodiversity, crop, and animal production in the country. In the Metekel Zone, there was no report on its distribution and impacts so far. Therefore, this study was aimed to assess the distribution and abundance of the plant in the zone. The distribution and abundance data of the weed were recorded at five km intervals following all accessible roads of the zone. The result reveals that P. hysterophorus L. was less distributed in the area with a 4.95% frequency. However, it was found abundantly growing at roadsides, wastelands, around habitation, market place, and around Zeghibridge where it can rapidly spread to most economical lands like the arable and grazing lands. Moreover, it has aggressively invaded a nursery site, which enables the weed to enter agricultural fields directly. This suggests that the weed is on a fast move to agricultural lands in the zone. The regular active development activities such as agricultural investment, construction of roads, and factories are presumed to promote its spread. Therefore, a decisive and timely decision is needed to mitigate the weed when it is still sparse and small.

Eco-toxicity of water, soil, and sediment from agricultural areas of Kilombero Valley Ramsar wetlands, Tanzania

This study was conducted in the KVRS to;evaluate the seasonal eco-toxicity of water,soil and sediment samples;establish the suitability of using temperate biotest batteries in tropical systems;classify the toxicity of samples using Fuzzy Rules to estimate potential ecological risks.143 water,sediment,and soil samples were collected during dry and rainy seasons in plantation areas.Pseudokirchneriella subcapitata,Aliivibrio fischeri and Arthrobacter globiformis bioassays were used to assess the toxicity of the samples.Results were categorized and classified into toxicity classes.Dry season presented a significantly higher mean inhibition of 31%than 5%shown by rainy season samples(p<0.001)in the bacterial bioassays,indicating a lower concentration of contaminants due to flooding and increased surface runoff.A few sediment samples resulted into 100%inhibition of A.globiformis,implying organisms were physiologically inactive upon exposure to contaminants.Seventy-three percent of samples posed little or no toxic potential risk,25%posed critical risk and 1%posed elevated critical risk,implying the KVRS ecosystem might be at risk if the extensive usage of pesticides in the area is not well managed and monitored.The temperate micro-biotests can be used in tropical systems,but with further research on suitable organisms and standardized methods.

Factorial significance on tractor stability under variation of terrain roughness employing the Taguchi method

Tractor rollover accidents remain an issue with the development of agricultural mechanization.Adopting the scale-model-based experimental approach,this study investigated the three most influential geometric factors of tractor in various agricultural ground conditions with improved configuration of force sensing system.The initiation of tractor rollover,associated with the tire-ground contact status,was investigated for various front tire types,ballast weights,and rear track widths.Employing the Taguchi method,the ground reaction forces applied to the tractor’s uphill wheels were measured and evaluated using stability indicators.By taking this approach,the effects and statistical significance of the three factors and their interactions were examined under various agricultural ground conditions.Results showed that the ballast weight significantly affected the ground contact status of the uphill front tire.The significance of the front tire type gradually increased as the road roughness increased,but dramatically decreased for an extremely rough road surface.Furthermore,none of the factors or interactions,except the factor of the rear track width for relatively rough roads,was statistically significant.The study revealed that not all commonly discussed factors consistently affect tractor stability.The results of the present study are thus expected to provide a reference explaining how to explore the necessity and feasibility of parameter adjustment before reconfiguring a tractor for higher stability.