Asymmetrical growth of the crowns of neighbouring desert shrubs

Rogers, Garry F.

doi:10.1016/s0140-1963(18)30885-1

Cited by 4 publications

(2 citation statements)

References 16 publications

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“…Crown plasticity occurs because of the modularity of trees, with individual branches growing at different light-dependent rates, and because of phototropism of the main stem (Franko 1986, Ford 1992, De Kroon et al 2005, although other factors such as gravity, wind, and abrasion of apical meristems may also be involved (Larson 1963, McMahon and Kronauer 1976, Grace 1977, King and Loucks 1978. Crown plasticity has been studied in many types of plants ranging from conifers (Halle et al 1978, Loehle 1986, Umeki 1995c, Stoll and Schmid 1998 and broadleaf trees (Gysel 1951, Woods and Shanks 1959, Frelich and Martin 1988, Young and Hubbell 1991, Brisson 2001, Webster and Lorimer 2005 to desert shrubs (Rogers 1989). Among trees, conifers appear to be less plastic than broad-leaved trees (Engler 1924, Busgen and Munch 1929, Assmann 1970, perhaps because of differences in the mechanism of apical control (Busgen and Munch 1929, Assmann 1970, Loehle 1986, Waller 1986).…”

Section: Plastic Crown Dynamicsmentioning

confidence: 99%

Scaling From Trees to Forests: Tractable Macroscopic Equations for Forest Dynamics

Strigul

Pristinski

Purves

et al. 2008

Ecological Monographs

232

339

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Individual‐based forest simulators, such as TASS and SORTIE, are spatial stochastic processes that predict properties of populations and communities by simulating the fate of every plant throughout its life cycle. Although they are used for forest management and are able to predict dynamics of real forests, they are also analytically intractable, which limits their usefulness to basic scientists. We have developed a new spatial individual‐based forest model that includes a perfect plasticity formulation for crown shape. Its structure allows us to derive an accurate approximation for the individual‐based model that predicts mean densities and size structures using the same parameter values and functional forms, and also it is analytically tractable. The approximation is represented by a system of von Foerster partial differential equations coupled with an integral equation that we call the perfect plasticity approximation (PPA). We have derived a series of analytical results including equilibrium abundances for trees of different crown shapes, stability conditions, transient behaviors, such as the constant yield law and self‐thinning exponents, and two species coexistence conditions.

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Section: Plastic Crown Dynamicsmentioning

confidence: 99%

Scaling From Trees to Forests: Tractable Macroscopic Equations for Forest Dynamics

Strigul

Pristinski

Purves

et al. 2008

Ecological Monographs

232

339

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“…In contrast, above-ground competition (for light) is relatively unimportant in sparse shrub communities (Rogers 1989;Skarpe 1991). Instead, widely-spaced individuals compete for below-ground resources (e.g.…”

Section: Introductionmentioning

confidence: 99%

Scales of aboveground and below‐ground competition in a semi‐arid woodland detected from spatial pattern

Martens

Breshears

Meyer

et al. 1997

J Vegetation Science

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Abstract. Semi‐arid woodlands are two‐phase mosaics of canopy and inter‐canopy patches. We hypothesized that both aboveground competition (within canopy patches), and below‐ground competition (between canopy patches), would be important structuring processes in these communities. We investigated the spatial pattern of trees in a Pinus edulis‐Juniperus monosperma woodland in New Mexico using Ripley's K‐function. We found strong aggregation of trees at scales of 2 to 4 m, which indicates the scale of canopy patches. Canopy patches were composed of individuals of both species. Crown centers of both species were always less aggregated than stem centers at scales less than canopy patch size, indicating morphological plasticity of competing crowns. In the smallest size classes of both species, aggregation was most intense, and occurred over a larger range of scales; aggregation decreased with increasing size as is consistent with density‐dependent mortality from intraspecific competition. Within canopy patches, younger trees were associated with older trees of the other species. At scales larger than canopy patches, younger trees showed repulsion from older conspecifics, indicating below‐ground competition. Hence, intraspecific competition was stronger than interspecific competition, probably because the species differ in rooting depth. Woodland dynamics depend on the scale and composition of canopy patches, aggregated seed deposition and facilitation, above‐ and below‐ground competition, and temporal changes in the spatial scale of interactions. This woodland is intermediate in a grassland‐forest continuum (a gradient of increasing woody canopy cover) and hence we expected, and were able to detect, the effects of both above‐ and below‐ground competition.

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Neighborhood competition and crown asymmetry inAcer saccharum

Brisson¹

2001

Can. J. For. Res.

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A tree neighboring a new gap must show a certain degree of morphological plasticity in its lateral growth to take advantage of the available space, expanding branches preferentially on the side of the gap. I evaluated the morphological plasticity of sugar maple (Acer saccharum Marsh.) by measuring crown asymmetry with respect to four different neighborhood contexts. Isolated trees have the most symmetrical crown, while all trees at the edge of a field have the largest part of their crown growing away from the forest. Asymmetry of trees at the edge of a forest and a recently constructed right-of-way is intermediate. The crown of forest trees is more developed away from the main competitive pressure of neighboring trees, with a disproportionate influence of the strongest neighbor. This crown development minimizes the negative effects of the interference with neighbors when competition is asymmetrical around a tree. The simplest mechanism allowing morphological plasticity and the resulting crown asymmetry involves a certain degree of autonomy of individual branches. Yet, branch autonomy is less likely for deciduous trees with determinate, single-flush growth patterns such as sugar maple. Some aspects of plasticity in sugar maple need to be investigated, especially with regard to a process where trees could compensate for the negative effects of close neighbors.

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Asymmetrical growth of the crowns of neighbouring desert shrubs

Cited by 4 publications

References 16 publications

Scaling From Trees to Forests: Tractable Macroscopic Equations for Forest Dynamics

Scaling From Trees to Forests: Tractable Macroscopic Equations for Forest Dynamics

Scales of aboveground and below‐ground competition in a semi‐arid woodland detected from spatial pattern

Neighborhood competition and crown asymmetry inAcer saccharum

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