دانلود رایگان مقاله انگلیسی تحت تاثیر قرار گرفتن علف های هرز محیط زیست با وراثت در درختان مرکبات و باغ های قدیمی - اشپرینگر 2017

Abstract

The concepts of destruction and rebuilding in the succession play an important role in agro-ecology. Agricultural ecosystems are always afected by tillage, soil preparation, harvest, burning, and arboriculture. A common practice in the northern province of Mazandaran (Iran) is to replace rice (Oryza sativa L.) cultivation with Citrus farming. It can be accordingly interesting to investigate the ecology of weed community specifcally the dominance and characters during the diferent stages of succession, using constitutive and physiological aspects. In a 2-year research work, some functional (species composition and stability) and physiological characteristics (relative growth rate, biomass, and N and P uptake) of diferent weeds in the initial and fnal stages of secondary succession in Citrus gardens were compared. Three young (Citrus sinensis L.) and three old Citrus (Citrus reticulata Blanco) gardens (with the average age of 2 and 29 years, respectively), were selected in the suburb of Qaemshahr city (Iran), the centre of Citrus production. In each garden, three main fxed plots (30 m2 ), with fve subplots (1 m2 ) and destructive quadrates in each one, were prepared and used for the experiment (January 2013–August 2014). Weed composition was monthly recorded. The concept of dominance diversity was used to estimate the community consistency. Thirty-three weed species were identified among which the Poaceae and Asteraceae families were the dominant ones. In the young gardens, the number of weed species was twice more than the old ones. Poa nemoralis as a perennial and sciophytes species were plentiful in the old gardens. Just in the young gardens, the weed species were moved by pappus. There was a linear and stable regression between weed frequency and dominance in the fnal sampling. Higher relative growth rate as well as higher N and P uptake was resulted in the young gardens. Seed size and growth rate were correlated in the young gardens, and the smaller seeds resulted in a higher rate of weed survival. Parameters including weed dominance, functional and physiological characteristics, seed size, and the environment may determine weed ecology and survival at diferent stages of succession in Citrus gardens.

4 Conclusion

Weed ecology, specifcally dominance and characteristics, at the initial and secondary stages of succession in the young and old Citrus gardens, was investigated using diferent functional and physiological characteristics. The composition of weeds and their response to the environmental parameters, including N and P nutrients, was signifcantly diferent in the young and old gardens. This experiment showed that the weed species in the young gardens were more competitive, and the higher RGR was related to the higher rate of compound translocations to the roots and high seed production. In the old gardens, perennial sciophytes species had more frequency and used much storage for maintenance process, which leads to the rise of higher stability. Parameters including weed dominance, functional and physiological characteristics, seed size, and the environment may determine weed ecology and survival at diferent stages of succession in Citrus gardens. Such fndings can be used for a more efcient use of weed controlling strategies by determining the composition of weeds and their interactions with Citrus trees. Future research work may determine how other ecological and environmental parameters, rather than the ones investigated in this study, may afect weed ecology in diferently aged Citrus gardens.