what kinds of species interactions drive succession in mountain forests? ANALYZI
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what kinds of species interactions drive succession in mountain forests?
ANALYZING DATA 17.1 in Mountain Forests? What Kinds of Species Interactions Drive Succession We learned in Concept 17.3 that successional patterns are often the result of complex species interactions. Such inter- actions are exemplified in a study investigating the patterns of succession in mountain forests in Utah dominated by quaking aspen (Populus tremuloides) and subalpine fir (Abies lasiocarpa) Calder and St. Clair 2012). In some cases, aspen can form stable and self-sustaining populations, but more commonly these trees occur in mixed stands with firs. Observations show that aspen initiate the earliest stage of secondary suc cession in open meadows created by fire or deforestation, using root suckers (underground shoots that produce clonal plants; see Figure 9.5) to colonize open meadows. Over time mixed aspen-fir stands are formed as the shade-tolerant firs become established and increase in abundance while aspen decline. The stands are eventually dominated by firs, which are more susceptible to fire than pure stands of aspen, thus increasing the chance of starting the successional cycle anew. Figure A ? Aspen suckers 14Fir seedlings 1.2 1.0 0.6 Meadow Aspen Mixed aspen-fir Fir Successional stage Figure B 80 Aspen > 0.5 m from fir Aspen 0.5 m from aspen FirExplanation / Answer
Ans: 1. In the first successional stage Aspen starts with suckers and in the second successional stage it is abundant than fir, in the third and fourth successional stages it decreases, and less abundant than fir. In the first and second successional stage Sub alpine fir is less abundant than Aspen from 3rd and 4th successional stage Sub alpine fir is dominant or more abundant than Aspen. Yes it supports the successional sequence.
2. In the aspen and meadow stages Inter specific interaction hypothesized is ‘antagonistic’ interactions, because first aspen dominance not allowed fir showing antagonism (indirectly helping it), later under shade fir started growing and showed antagonism to aspen. In the mixed and fir stages fir showing antagonism to aspen and aspen suckers decreased.
3. When fir is <0.5m to aspen trees in aspen and aspen-fir mixed stages it is completely absent or failed to grow (severe antagonism) and in fir stage it is successful or started growing. When aspen is <0.5m to fir trees in aspen stage it is expected to dominate and graph supports that but in aspen-fir mixed stages it is expected to decrese, but its increasing hence this data does not support hypothesis from question 2
4. According to Connell and Slatyer, This is a facilitation model, why because, this model says that initial colonists (here Aspen grows first, lets say after destruction by fire or cutting of dominant fir) prepare environment for later successional species (here fir, under the aspens shade fir grows and outgrows aspen)
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