Plant Succession and Competition(Suksesi Tumbuhan dan Kompetisi)

Ecological Succession = development of an ecosystem = changes in species structure and community composition over time

Ecological SuccessionSuccession = change in species structure and community composition over time. BareHerbs,Small Mature groundgrasses Shrubstrees forest (climax)

ColonizersPersisters(adapt to new area)(relatively stable over time)Low diversityHigh diversityP>RPR

Ecological SuccessionSuccession = change in species structure and community composition over time. BareHerbs,Small Mature groundgrasses Shrubstrees forest (climax)

Physical factors and climate (e.g., soil, fire) can dictate endpoint in succession

Grassland end point due to fire, soils, moisture, etc

Ecological SuccessionSuccession = change in species structure and community composition over time. BareHerbs,Small Mature groundgrasses Shrubstrees forest (climax)

Secondary succession occurs on cleared land

Ecological Succession Application to AgricultureSecondary succession occurs on cleared landCertain herbaceous plants (grasses, nutsedge, etc.) are well adapted as colonizers become weeds in agricultural fields

CompetitionTwo species occupying similar nicheCompete for water, nutrients, space, light, etc. Characteristics of the plant species (growth habits, genetics/variety, etc.) and environment (season, temp., moisture, etc.) determine which species will prevail

Allelopathy = unusual advantage in some competitions

Allelopathy -- some plants secrete chemicals that are suppressive to other plants

SunflowerWalnut trees (not much undergrowth)Oak tanninsGrains some cultivars of rye, wheat, oats

CompetitionInterspecific competition between different species (crop plant vs. weeds)Intraspecific competition among plants of the same species (controlled in agriculture by planting rate plant density)

Increased plant density (reduced row spacing) may increase yields to a point (more plants/ha)Increased plant population

Increased plant density (reduced row spacing) may increase yields to a point (more plants/ha)Increased plant populationOptimum spacingLow yield due to low plant population

Increased plant density (reduced row spacing) may increase yields to a point (more plants/ha)Increased plant populationOptimum spacingLow yield due to low plant populationLow yield due to competition, crowded plants

Plant density depends on:Row spacing (previous example)Distance between plants in rows (e.g., if corn plant populations too high lodging, barren plants)Broadcast seeding rates (for plants not in rows)

Effects of decreasing space between plant rows:+++ Increases plant population and yield (to a point)+++ Improved competition vs weeds (less open row space for weed colonization)- - - Difficult passage for equipment- - - Possible increase in plant diseases (mortality)

Effects of decreasing space between plant rows:+++ Increases plant population and yield (to a point)+++ Improved competition vs weeds (less open row space for weed colonization)- - - Difficult passage for equipment- - - Possible increase in plant diseases (mortality)Important to know optimum plant spacing for each crop cultivar

ReferencesText, pp. 30-31, 126-127, 134-137.Altieri, M.A. 1987. Agroecology. The Scientific Basis of Alternative Agriculture. Westview Press, Boulder, CO. Ch. 14.Begon et al., 1990.Carroll et al. 1990. Ch. 8.Odum, 1983. Ch. 8.Russo, V.M. 1995. HortScience 30:53-54.