AGROECOSYSTEM: Squash (Cucurbita maxima)

AGROECOSYSTEM: Squash (Cucurbita maxima)

AGROECOSYSTEMDefinitionAgriculture + Ecosystem = Agroecosystem

Any ecosystem largely created and maintained to satisfy a human want or need is called an agroecosystem.

It is a site or integrated region of agricultural production understood as an ecosystem;An ecosystem is a functional system of complementary relations between living organisms and their environment.Basic structural components:Biotic factors- living organisms that interact in the environment Abiotic factors- nonliving physical and chemical components of the environment SoilLightMoisturetemperature

Levels of organizationLevels of ecosystem organization applied to agroecosystem

Energy flowEcosystem energy flow. The size of each box represents the relative amount of energy flowing through that trophic level.

In average, only about 10% of the energy in a trophic level is transferred to the next trophic level. Nearly all the energy that enters an ecosystem is eventually dissipated as heat.Energy lost from one trophic level to the next level can be represented by a pyramid.

4 CONSUMERS3 CONSUMERS2 CONSUMERS1 CONSUMERSPRODUCERSEach level above only gets 10% of the energy frombelow.

Usually no more than 5 trophic levels since 6th level would have very little energy to keep it alive.

agroecosytemsHuman manipulation and alteration of ecosystems for the purpose of establishing agricultural production makes agroecosystems very different from natural ecosystems. At the same time, however, the components and characteristics of natural ecosystems can be observed in agroecosystems.

Energy flow in agroecosystems is altered greatly by human interference.

Inputs are derived from primarily human sources and are often not self-sustaining.

Functional components of a natural ecosystem.Functional components of an agroecosystem.

Table 1. Important structural and functional differences between NE & AENatural ecosystemAgroecosystem Net productivityMediumHighTrophic interactionsComplexSimpleSpecies diversityHighLowGenetic diversityHighLowNutrient cyclesClosedOpenStability HighLowHuman controlIndependentDependentTemporal permanenceLongShortHabitat heterogeneityComplex Simple NUTRIENT CYCLINGMinimal and considerable quantities are lost during harvest or as a result of leaching.Leaking of nutrients from the system--- frequent exposure of bare soil between crops.Farmers rely heavily on petroleum based inputs to replace these losses.Population regulating mechanismsHuman inputs(seeds or control agents) determine population sizes:Simplification of environmentReduced trophic interactionsPlants and animals are rarely self-reproducing and self-regulating

Reduced biological diversityMore simplified trophic structuresUnoccupied nichesHigh danger of catastrophic pest and diseasestabilityAgroecosystems have less resilience than natural ecosystems

--- due to reduced structural and functional diversity in relation to natural ecosystems.

Focus on harvest outputs upsets the equilibrium established in the ecosystem.

The system can only be sustained by maintaining the outside interference --- in the form of human labor and external outputsSquashProducer

INSECTSPrimary consumersThey are natural enemies of many insects, especially aphids and other sap feeders.

Ladybugs/lady beetlesMost destructive insect pest of squash. Feeding damage results in wilting of vines, often with plants being prematurely killed.

Squash Bug (Anasa tristis)They suck the juice from the plants and some transmit viral diseases.

Aphid WEEDCompetition

DISEASES

Fruit rot

Leaf chlorosis

Erwinia tracheiphila

Ecological impact of farmingMonoculture

monocultureMonoculture increases the productivity of farmland by growing only the best variety crop; allowing more than one crop per year; simplifying sowing and harvesting of the crop; and reducing labor costs.However, monoculture has a major impact on the environment:reduces genetic diversity and renders all crops in a region susceptible to disease.Fertilisers are required to maintain soil fertility. This is expensive and can pollute surrounding groundwater due to leaching.

Monoculture reduces species diversity. This has many knock-on effects such as allowing a pest species to get out of control, fewer plants due to lack of pollinating insects and loss of species that may be useful to humans.

PesticidesReferencesGliessman, S. R. (2007). Agroecology: The Ecology of Sustainable Food System. 2nd Ed. Taylor & Francis Group. NY.Kalabasa. Retrieved from: http://www.stuartxchange.com/Kalabasa.html. February 26, 2015.http://www.ext.colostate.edu/pubs/insect/05609.html