The Test of Time: Using Historical Methods to Assess Models of Ecological Change on California’s Hardwood Rangelands

Abstract

Geographers and environmental scientists use conceptual models to understand ecological processes and support management decisions. Most of these models are based on short-term experiments and field observations, which might not account for longer term forces that shape ecosystems over decades to centuries. How can scholars use historical sources and methods to improve conceptual models of ecological change? In this article, we present the results of a study that employed methods from environmental history and historical geography to assess three conceptual models that researchers have used to study ecological changes on California’s hardwood rangelands: the succession and climax, state and transition, and cyclical replacement models. The succession and climax model fared poorly at all spatial scales. The historical record contained substantial evidence to support the predictions of the state and transition model at the small spatial scale of the plot or field (0.1–100 ha) and the very large spatial scale of the hardwood rangeland bioregion (4 million ha). The cyclical replacement model performed well at the intermediate scale of the landscape or typical cattle ranch (100–10,000 ha). Historical data and methods hold considerable untapped potential for assessing, building on, and improving conceptual models of ecological change in geography and the environmental sciences.

地理学者和环境科学家使用概念模型来理解生态过程、支持管理决策。这些模型大多基于短期的实验和野外观测，可能没有考虑对生态系统有数十到数百年影响的长期因素。如何利用历史资料和方法来改进生态变化概念模型？本文采用环境历史和历史地理的方法，评估了三个概念模型（演替-顶级模型，状态-转换模型，周期性更替模型），并研究了美国加利福尼亚硬木牧场的生态变化。在各种空间尺度上，演替-顶级模型结果都较差。在小空间尺度的地块（1-100公顷）和大空间尺度的硬木牧场生态区（4百万公顷），历史数据能充分支持状态-转换模型的预测结果。在中尺度的景观和黄牛牧场（100-10，000公顷），周期性更替模型效果良好。地理学和环境科学领域内，在生态变化概念模型的评估、建立和改善上，历史数据和方法具有巨大的潜力，但是还有待挖掘。

Los geógrafos y los científicos ambientales usan modelos conceptuales para entender los procesos ecológicos y para respaldar decisiones de manejo. La mayoría de estos modelos se basan en experimentos de corto término y en observaciones de campo, que podrían no considerar debidamente aquellas fuerzas de plazo más largo que configuran los ecosistemas a través de décadas y siglos. ¿Cómo pueden los estudiosos usar fuentes y métodos históricos para mejorar los modelos conceptuales de cambio ecológico? En este artículo presentamos los resultados de un estudio que empleó métodos de historia ambiental y de geografía histórica para evaluar tres modelos conceptuales que han sido usados por investigadores en estudios de los cambios ecológicos de áreas montuosas madereras de California: la sucesión y el clímax, el estado y la transición, y los modelos de remplazo cíclico. Al modelo de sucesión y clímax le fue pésimamente en todas las escalas espaciales. El registro histórico contenía evidencia sustancial para respaldar las predicciones del modelo de estado y transición a la escala espacial pequeña de lote o del campo (0.1–100 ha) y a la escala espacial muy grande de la biorregión de áreas boscosas maderables (4 millones de ha). El modelo de remplazo cíclico se desempeñó bien a la escala intermedia de paisaje o de rancho ganadero típico (100–10.000 ha). Los datos y métodos históricos tienen una considerable capacidad no utilizada hasta ahora para evaluar, para construir y para mejorar los modelos conceptuales de cambio ecológico en geografía y en las ciencias ambientales.

Key Words:

• California
• historical methods
• models
• rangelands
• scale

关键词:

• 加利福尼亚
• 历史方法
• 模型
• 牧场
• 空间尺度

Palabras clave:

• áreas montuosas
• California
• escala
• métodos históricos
• modelos

Supplemental Material

The compiled data that support the findings of this study, as well as references for all data sources, are available as a table in figshare and on the Web site of the corresponding author, Tim Paulson, at http://blogs.ubc.ca/timpaulson/resources/data/. The supplemental material can also be accessed on the publisher's wesbite at http://dx.doi.org/10.1080/24694452.2020.1782168. The table presents data in quantitative or qualitative form on seven indicators (vegetation, fire, livestock, wild ungulates, carnivores, precipitation, and erosion) for three sites on California’s hardwood rangelands from 1800 to 2017. Land management transition periods and managed property size are also included for reference and comparison. Many of these data are visualized in Figure 4.

Additional information

Funding

This work was supported by the University of California Institute for the Study of Ecological & Evolutionary Climate Impacts, the National Science Foundation, and the Social Science and Humanities Research Council under Grant 756-2017-0782.

Notes on contributors

Tim Paulson

TIM PAULSON is an Assistant Professor in the Department of History and Sociology at the University of British Columbia, Syilx Okanagan Nation Territory, Kelowna, BC V1V 1V7, Canada. E-mail: [email protected]. He received his PhD from the University of California, Santa Barbara and held a postdoctoral fellowship at Simon Fraser University. His applied history research examines Canadian and global rangelands using mixed methods and sources.

Kevin C. Brown

KEVIN C. BROWN is a Research Associate in the Environmental Studies Program at the University of California, Santa Barbara, Santa Barbara, CA 93106-4160. E-mail: [email protected]. He received his PhD in history from Carnegie Mellon University and was a postdoctoral fellow at the University of California, Santa Barbara. He is completing his first book, an exploration of how one of the world’s rarest species (the Devils Hole pupfish) managed to survive the twentieth century.

Peter S. Alagona

PETER S. ALAGONA is an Associate Professor of History, Geography, and Environmental Studies at the University of California, Santa Barbara, Santa Barbara, CA, 93106-4160. E-mail: [email protected]. He received his PhD at UCLA and held postdoctoral fellowships at Harvard and Stanford University. His research focuses on the relationships between humans and other species—particularly charismatic wildlife—and the changing wildland, rural, and urban habitats they share.