Enlargement of canopy gaps associated with a fungal pathogen in Yosemite Valley, California

Rizzo, David M.; Slaughter, G. W.; Parmeter, J. R.

doi:10.1139/x00-073

Cited by 30 publications

(42 citation statements)

References 25 publications

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“…Host-specific diseases or pest outbreaks, a common biotic agent of contagious disturbance in temperate forests (e.g., Rizzo et al 2000, Worrall et al 2005, are less likely to play a role in (species-rich) tropical forests, where neighboring individuals tend to be heterospecifics. First, tropical forests usually are much more species diverse and often more unevenly aged than the temperate-zone forests for which contagiousness has been demonstrated.…”

Section: Mechanisms Of Contagious Disturbancementioning

confidence: 99%

Spatial Contagiousness of Canopy Disturbance in Tropical Rain Forest: An Individual‐tree‐based Test

Jansen

Meer

Bongers

2008

Ecology

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Spatial contagiousness of canopy dynamics-the tendency of canopy disturbances to occur nearby existing canopy openings due to an elevated risk of tree fall around gaps-has been demonstrated in many temperate-zone forests, but only inferentially for tropical forests. Hypothesized mechanisms increasing the risk of tree fall around tropical forest gaps are (1) increased tree exposure to wind around gaps, (2) reduced stability of trees alongside gaps due to crown asymmetry, or (3) reduced tree health around gaps due to damage from prior disturbances. One hypothesized consequence of elevated disturbance levels around gaps would be that gap-edge zones offer relatively favorable prospects for seedling recruitment, growth, and survival. We tested whether disturbance levels are indeed elevated around natural canopy gaps in a neotropical rain forest in French Guiana, and more so as gaps are larger. We followed the fate of 5660 trees >10 cm stem diameter over five years across 12 ha of old-growth forest and analyzed the risk and magnitude of canopy disturbance events in relation to tree diameter and the proximity and size of natural canopy gaps. We found that the cumulative incidence of disturbance over the five-year survey was not significantly elevated around preexisting gaps, and only weakly related to gap size. Also, neither the risk nor the magnitude of canopy disturbances increased significantly with the proximity of gaps. Moreover, canopy disturbance risk around gaps was independent of gap size, while the magnitude of disturbance events around gaps was weakly related to gap size. Tree size was the major driver of disturbance risk as well as magnitude. We did find an elevated incidence of disturbance inside preexisting gaps, but this "repeat disturbance" was due to an elevated disturbance risk inside gaps, not around gaps. Overall, we found no strong evidence for canopy dynamics in this rain forest being spatially contagious. Our findings are consistent with the traditional view of tropical rain forests as mosaics of patches with predictable regeneration cycles.

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Section: Mechanisms Of Contagious Disturbancementioning

confidence: 99%

Spatial Contagiousness of Canopy Disturbance in Tropical Rain Forest: An Individual‐tree‐based Test

Jansen

Meer

Bongers

2008

Ecology

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“…genets affecting several trees. Other factors affecting the number of trees occupied by a single genet include the age of the genet and the stand structure (Rizzo et al 2000), as the probability of root contacts is higher in denser stands. In addition, the host genotype is an important factor for spreading within the stand and for growth within the host.…”

Section: Introductionmentioning

confidence: 99%

Infection of Picea abies clones with a homokaryotic isolate of Heterobasidion parviporum under field conditions

et al. 2015

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Heterobasidion parviporum Niemelä & Korhonen is responsible for the majority of decay in conifers in northern Europe, which causes severe economic losses. In nature, heterokaryotic isolates of H. parviporum cause infection in Norway spruce (Picea abies (L.) Karst.). However, little is known on whether homokaryons of H. parviporum can infect trees under field conditions. In this study, 40-year-old clonal Norway spruce stems and roots were inoculated with a homokaryotic isolate of H. parviporum under field conditions. After four months, the infection frequency and necrotic lesion lengths were recorded. The homokaryon caused infection and provoked the development of necrotic lesions. Necrotic lesions were larger in roots than in stems. Among the studied Norway spruce genotypes, a Russian clone had the smallest necrotic lesions, whereas a Finnish clone developed the largest necrotic lesions. Clones with higher growth rates were more sensitive to fungal infection and wound damage. Under microscopic observation, H. parviporum grew adpressed to lumen cell walls, colonized tracheids next to rays, and induced lignification in cell walls close to the point of inoculation. This study provides a starting point for further studies on the ability of homokaryons to cause infection under field conditions and for discussions on factors affecting the resistance of Norway spruce against H. parviporum.Résumé : Chez les conifères d'Europe du Nord, la majeure partie de la carie qui est responsable d'importantes pertes économiques est causée par Heterobasidion parviporum Niemelä & Korhonen. En nature, des isolats hétérocaryotes de H. parviporum infectent l'épicéa commun (Picea abies (L.) Karst.). Cependant, on ne sait pas si des homocaryons de H. parviporum peuvent infecter les arbres sur le terrain. Dans cette étude, les racines et la tige d'individus clonaux d'épicéa commun âgés de 40 ans ont été inoculés avec un isolat homocaryote de H. parviporum sur le terrain. Après quatre mois, la fréquence des infections et la longueur des lésions nécrotiques ont été notées. L'homocaryon a causé une infection et provoqué le développement de lésions nécrotiques. Les lésions nécrotiques étaient plus grandes sur les racines que sur la tige. Parmi les génotypes d'épicéa commun étudiés, un clone russe avait les lésions nécrotiques les plus petites tandis que les plus grandes lésions se retrouvaient sur un clone finlandais. Les clones qui avaient le taux de croissance le plus élevé étaient plus sensibles aux infections fongiques et aux dommages causés par les blessures. Sous observation microscopique, H. parviporum croissait adossé à la paroi cellulaire à l'intérieur des cellules, colonisait les trachéides adjacentes aux rayons et induisait la lignification dans la paroi des cellules situées près du point d'inoculation. Cette étude constitue un point de départ pour d'autres études portant sur la capacité des homocaryons à causer des infections sur le terrain et pour alimenter la discussion concernant les facteurs qui influencent la résistance de l'ép...

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“…Pathogen-and insect-induced mortality can take many forms and affect forests at a variety of scales at various points in succession (Hansen and Goheen 2000, Rizzo et al 2000, Piri 2003, Filip and Ganio 2004. In coastal forests of the Pacific Northwest, insect-induced mortality is relatively uncommon (Childs and Shea 1967); however, root and stem rots are frequent, particularly in older forests (Holah et al 1997, Bible 2001.…”

Section: Introductionmentioning

confidence: 99%

Tree Mortality During Early Forest Development: A Long-Term Study of Rates, Causes, and Consequences

Lutz

Halpern

2006

Ecological Monographs

201

179

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Tree mortality is a critical but understudied process in coniferous forest development. Current successional models assume that mortality during early forest development is dominated by density‐dependent processes, but few long‐term studies exist to test this assumption. We examined changes in forest structure and patterns of tree mortality 14–38 years (1979–2001) after clear‐cut logging of two experimental watersheds in the western Cascade Range of Oregon, USA. We sampled 193 permanent plots (250 m2) six times generating 75126 data records and 7146 incidents of mortality. Mean density peaked at >3000 stems/ha (≥1.4 m tall) after 22–25 years; bole biomass increased continuously to >100 Mg/ha. At final sampling, stem density varied by two orders of magnitude and biomass by a factor of 10 among sample plots. Suppression mortality occurred in >80% of plots and was >2.5 times as frequent as mechanical damage (uprooting, stem snap, and crushing). However, biomass lost to mortality via mechanical damage was nearly four times that lost to suppression, a result of episodic storms that created windthrow patches, with some plots losing 30–50% of biomass. Total annual mortality increased from 1.0% to 5.3% of stems over the study period and was highly variable among species. Although mortality rates were highest for sprouting hardwoods (reaching 9.7% in Cornus nuttallii), biomass of most hardwood species increased through canopy closure as dominant stems achieved large sizes. Shade‐tolerant conifers (Tsuga heterophylla and Thuja plicata), typically assumed to be absent or to play a minor role in early forest development, accounted for 26% of stems after 38 years. In regression tree models, environmental attributes of plots had limited ability to predict mortality. Instead, stem density prior to canopy closure was the strongest predictor of cumulative mortality (either suppression or mechanical damage). Our long‐term studies suggest that current models of early forest development are overly simplistic, particularly in their treatment of mortality. Although suppression was the dominant demographic process, mechanical damage yielded greater loss of biomass and greater structural heterogeneity through creation of windthrow gaps. Thus, gap‐forming processes that operate late in succession and contribute to structural complexity in old‐growth forests can also occur early in stand development.

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Enlargement of canopy gaps associated with a fungal pathogen in Yosemite Valley, California

Cited by 30 publications

References 25 publications

Spatial Contagiousness of Canopy Disturbance in Tropical Rain Forest: An Individual‐tree‐based Test

Spatial Contagiousness of Canopy Disturbance in Tropical Rain Forest: An Individual‐tree‐based Test

Infection of Picea abies clones with a homokaryotic isolate of Heterobasidion parviporum under field conditions

Tree Mortality During Early Forest Development: A Long-Term Study of Rates, Causes, and Consequences

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