Heterogeneity in recruitment and habitat patterns of valley oak (Quercus lobata Née) at the site and landscape scale in the Santa Monica Mountains, California, USA

Hayes, James J.

doi:10.1007/s11258-013-0219-5

Cited by 5 publications

(11 citation statements)

References 14 publications

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“…Such high rainfall years have occurred with sufficient frequency in the recent past that documented low oak regeneration in open savannas in our region cannot be attributed solely to climate. This could change as the local climate continues to warm, and seedling establishment and sapling growth become increasingly moisture‐limited (Hayes , McLaughlin and Zavaleta , McLaughlin et al. ).…”

Section: Discussionmentioning

confidence: 99%

Demography of evergreen and deciduous oaks in a mixed oak savanna: insights from a long‐term experiment

2019

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The co-existence of evergreen and deciduous oaks in Mediterranean-climate savannas has motivated comparative studies on species' physiological adaptations to light and drought, establishment niche differences in acorn production, dispersal and seedling herbivory, and differential sapling tolerance of ungulate browsing. Understanding how species' differences collectively affect co-occurrence or segregation requires long-term studies that consider multiple life stages. We compare survival, height growth, and modeled population growth rate of the evergreen sclerophyll, Quercus agrifolia, to those of the winterdeciduous, broadleaved Q. lobata in southern California savanna sites where the species naturally co-occur. We evaluate species' performances after 8.7 yr for four cohorts sown as acorns in 1997, 1998, 2000, and 2001 under four different levels of protection from cattle, deer, and rodents. Survival curves for the two species were closely similar, with large differences between cohorts associated with precipitation in the year acorns were sown. Survival and growth rates of Q. agrifolia seedlings and saplings were slightly lower, and were more reduced by ungulates and rodents, than those of Q. lobata. No Q. agrifolia plants (0/1431) exposed to ungulates (cattle and/or deer) and rodents survived to the end of the experiment. Of 1421 Q. lobata acorns planted in these treatments, only 19 plants (1.3%) survived 8.7 yr and none of these plants progressed out of the ungulate browse layer. However, when protected from both ungulates and rodents, survival rates increased significantly for both species, and Q. agrifolia increased height faster than Q. lobata. Simulated population growth rates increased slightly for plants protected from ungulates, and 95% confidence intervals spanned the stable population growth rate of 1. With exclusion of ungulates and rodents, sapling and small tree recruitment rates for both species far exceeded those needed to offset the rate of recent adult mortality, with modeled population growth rates of 1.07-1.11. Our results underscore the essential role of occasional high rainfall years for initial establishment, plus the key role of consumers in limiting early survival and growth of both evergreen and deciduous oaks in mixed oak savannas.

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Section: Discussionmentioning

confidence: 99%

Demography of evergreen and deciduous oaks in a mixed oak savanna: insights from a long‐term experiment

2019

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“…; McConkey et al . ; Hayes ; Lavabre & García ). Therefore, analysing the variation in species regeneration and the determinants of such variation at large scales is essential for more adequate management of species and habitats (García et al .…”

Section: Introductionmentioning

confidence: 99%

Regeneration of a keystone semiarid shrub over its range in Spain: habitat degradation overrides the positive effects of plant–animal mutualisms

et al. 2018

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Global change drivers are currently affecting semiarid ecosystems. Because these ecosystems differ from others in biotic and abiotic filters, cues for plant regeneration and management derived from elsewhere may not be applicable to semiarid ecosystems. We sought to determine the extent to which regional variation in regeneration prospects of a long-lived semiarid keystone shrub depends on anthropogenic habitat degradation, plant-animal interactions and climate determinants. We investigated the regeneration ability (via population size structure, juvenile density and juvenile/adult ratio), fruit set and seed dispersal of Ziziphus lotus in 25 localities spanning the range of its threatened habitats in Spain. We dissected the relative contribution of different regeneration determinants using multiple regression and structural equation modelling. Population regeneration was extremely poor, and size structures were biased towards large classes and low juvenile densities and juvenile/adult ratios. Poor regeneration was often coincident with seed dispersal collapse. However, the positive effect of seed dispersal on population regeneration disappeared after considering its relationship with habitat degradation. Protected areas did have juveniles. Together, these data suggest that habitat degradation directly impacts juvenile establishment. Our results provide insights into habitat and species management at the regional level. Z. lotus populations are currently driven by persistence-based dynamics through the longevity of the species. Nonetheless, collapsed seed dispersal, poor regeneration and the removal of adults from their habitats forecast extinction of Z. lotus in many remnants. The extreme longevity of Z. lotus provides opportunities for recovery of its populations and habitats through effective enforcement of regulations.

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“…We asked these questions for all of the stems at each site, as well as for adult stems (dbh ≥ 10 cm) and sapling stems (1 ≤ dbh < 10 cm) to assess whether patterns in stem establishment were changing. The above methods are discussed in more detail in Hayes [52].…”

Section: Methodsmentioning

confidence: 99%

A Resilience-Based Approach to the Conservation of Valley Oak in a Southern California Landscape

Hayes

Donnelly

2014

Land

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Conservation thinking will benefit from the incorporation of a resilience perspective of landscapes as social-ecological systems that are continually changing due to both internal dynamics and in response to external factors such as a changing climate. The examination of two valley oak stands in Southern California provides an example of the necessity of this systems perspective where each stand is responding differently as a result of interactions with other parts of the landscape. One stand is experiencing regeneration failure similar to other stands across the state, and is exhibiting shifts in spatial pattern as a response to changing conditions. A nearby stand is regenerating well and maintaining spatial and structural patterns, likely due to the availability of imported water associated with upstream urban development. Valley oak stands have a capacity for reorganization as a response to changes in the landscape and environmental conditions. This reorganization can benefit conservation efforts; however, we must ask what limits there are to valley oak's capacity to reorganize and still maintain its ecological function in face of increasing changes in climate and land cover. The usefulness of resilience as a concept in conservation is discussed at several scales from the stand to the landscape.

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Heterogeneity in recruitment and habitat patterns of valley oak (Quercus lobata Née) at the site and landscape scale in the Santa Monica Mountains, California, USA

Cited by 5 publications

References 14 publications

Demography of evergreen and deciduous oaks in a mixed oak savanna: insights from a long‐term experiment

Demography of evergreen and deciduous oaks in a mixed oak savanna: insights from a long‐term experiment

Regeneration of a keystone semiarid shrub over its range in Spain: habitat degradation overrides the positive effects of plant–animal mutualisms

A Resilience-Based Approach to the Conservation of Valley Oak in a Southern California Landscape

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