Donald Falk - Academia.edu (original) (raw)

Papers by Donald Falk

Ecological Restoration, 1996

research. W the National Science Foundation initiated the Special Program in Conservation and Res... more research. W the National Science Foundation initiated the Special Program in Conservation and Restoration Biology (CRB) in 1989, restorationists saw it as a milestone in the coming age of restoration. Most previous research in restoration had been funded privately or, where state and federal funds were involved, was more often for the utilitarian purposes of reclamation or rehabilitation. This was the first time restoration was treated as a legitimate area for basic research. The CRB Program seemed like a move that would help improve the quality of restoration research and promote increased participation by academic researchers. However, the results of the program have been disappointing. Out of some 15 proposals funded each year, on average only one or two were restoration proposals. This reflected the small proportion of restoration proposals submitted and raises the question of why so few researchers chose to submit restoration-oriented proposals. In contrast, the program has been enormously successful for conservation researchers, who submitted the bulk of the funded proposals. Conservation genetics and population-level conservation research have made great strides in both basic and applied research since 1989, and have become part of mainstream research in population ecology and genetics. Partly for this reason, future proposals in this area are likely to be well received by reviewers and panelists engaged in mainstream genetics and population biology research. In fact, "mainstreaming" is the intent of special programs at NSF, the idea being to promote areas that have previously been neglected, raising them to the status of traditional research areas. Special programs at NSF are designed to last some four years, but after seven years of the CRB Program restoration research has still not become part of ecological mainstream research, and has progressed little in conceptual development. To help change this trend in restoration research, we organized a workshop on "Developing the Conceptual Basis for Restoration Biology." We consulted with Scott Collins, a CRB program officer, on the approaches and results that would be most useful for NSF. There are social, political and economic limitations to restoration, but NSF can help only in the area of scientific limitations so we focused our workshop on the scientific aspects of restoration. We all felt that one of the reasons so few ecologists chose to submit proposals is that restoration is still viewed as a discipline without the conceptual basis needed to support basic research. Michael Soule and Kathryn Kohm’s book, Research Priorities for Conservation Biology (1989), helped to develop the conceptual basis for conservation biology, but a similar approach has never been taken for restoration. While Soule and Kohm discussed restoration, they presented it as a job for land managers, and not a scientific discipline. They also downplayed the importance of restoration for conservation, arguing that

Frontiers in Ecology and Evolution, 2019

Landscapes and the ecological processes they support are inherently complex systems, in that they... more Landscapes and the ecological processes they support are inherently complex systems, in that they have large numbers of heterogeneous components that interact in multiple ways, and exhibit scale dependence, non-linear dynamics, and emergent properties. The emergent properties of landscapes encompass a broad range of processes that influence biodiversity and human environments. These properties, such as hydrologic and biogeochemical cycling, dispersal, evolutionary adaptation of organisms to their environments, and the focus of this article, ecological disturbance regimes (including wildfire), operate at scales that are relevant to human societies. These scales often tend to be the ones at which ecosystem dynamics are most difficult to understand and predict. We identify three intrinsic limitations to progress in landscape ecology, and ecology in general: (1) the problem of coarse-graining, or how to aggregate fine-scale information to larger scales in a statistically unbiased manner; (2) the middle-number problem, which describes systems with elements that are too few and too varied to be amenable to global averaging, but too numerous and varied to be computationally tractable; and (3) non-stationarity, in which modeled relationships or parameter choices are valid in one environment but may not hold when projected onto future environments, such as a warming climate. Modeling processes and interactions at the landscape scale, including future states of biological communities and their interactions with each other and with processes such as landscape fire, requires quantitative metrics and algorithms that minimize error propagation across scales. We illustrate these challenges with examples drawn from the context of landscape ecology and wildfire, and review recent progress and paths to developing scaling laws in landscape ecology, and relatedly, macroecology. We incorporate concepts of compression of state spaces from complexity theory to suggest ways to overcome the problems presented by coarse-graining, the middle-number domain, and non-stationarity.

Fire History Analysis and Exploration System

Variation in Earth’s climate system has always been a primary driver of ecosystem processes and b... more Variation in Earth’s climate system has always been a primary driver of ecosystem processes and biological evolution. In recent decades, however, the prospect of anthropogenically driven change to the climate system has become an increasingly dominant concern for scientists and conservation biologists. Understanding how ecosystems may adapt to rapid contemporary and future change benefits from our knowledge of how they have responded to natural climatic variation across prehistoric time, especially during periods when Earth system conditions and ecosystems correspond to those of the modern era (e.g., Quaternary, the past 2.5 million years). Despite the dominant and pervasive influence of both climate variability and climate change, the restoration field is still learning how to accommodate these emerging influences. In this chapter we explore the consequences of climate variability and change for the science of restoration ecology and the practice of ecological restoration.

Beginning in 2007 in and around the Huachuca Mountains, the Coronado National Forest and other pa... more Beginning in 2007 in and around the Huachuca Mountains, the Coronado National Forest and other partners have been mapping ecosystems at multiple scales. The approach has focused on identifying land type associations (LTA), which represent the sum of bedrock and superficial geology, topography, elevation, potential and existing vegetation, soil properties, and local climatic variables. This mapping effort has been extended into the FireScape program, in which multiple partners utilize ecological land type mapping as a framework for fire planning across the Sky Island bioregion. Land type association maps for the Catalina-Rincon mountains (available at www.azfirescape.org) are used for managing ecological units (e.g., mixed conifer on granitic soils) typically no smaller than a thousand acres, and often much larger. Land type associations compliment raster-based sources of information such as LANDFIRE. Not surprisingly, the success of the project depends on an accurate depiction of ve...

Ecosphere, 2020

Macroecological studies have established widespread patterns of species diversity and abundance i... more Macroecological studies have established widespread patterns of species diversity and abundance in ecosystems but have generally restricted their scope to relatively steady-state systems. As a result, how macroecological metrics are expected to scale in ecosystems that experience natural disturbance regimes is unknown. We examine macroecological patterns in a fire-dependent forest of Bishop pine (Pinus muricata). We target two different-aged stands in a stand-replacing fire regime: a mature stand with a diverse understory and with no history of major disturbance for at least 40 yr, and one disturbed by a stand-replacing fire 17 yr prior to measurement. We compare properties of these stands with macroecological predictions from the Maximum Entropy Theory of Ecology (METE), an information entropy-based theory that has proven highly successful in predicting macroecological metrics in multiple ecosystems and taxa. Ecological patterns in the mature stand more closely match METE predictions than do data from the more recently disturbed, mid-seral stage stand. This suggests METE's predictions are more robust in latesuccessional, slowly changing, or steady-state systems than those in rapid flux with respect to species composition, abundances, and organisms' sizes. Our findings highlight the need for a macroecological theory that incorporates natural disturbance, perturbations, and ecological dynamics into its predictive capabilities, because most natural systems are not in a steady state.

Foundations of Restoration Ecology, 2016

... play an important role in the manage-ment of germplasm resources and restoration ecology by d... more ... play an important role in the manage-ment of germplasm resources and restoration ecology by determining the heritable compo-nent of ecologically important traits such as growth rates and tolerance for drought or ex-treme temperatures (Mitchell-Olds 1995; van Tienderen et ...

Restoration Ecology, 2021

The distinction often made between active and passive restoration approaches is a false dichotomy... more The distinction often made between active and passive restoration approaches is a false dichotomy that persists in much research, policy and financial structures today. We explore the contradictions imposed by this terminology, and the merits of replacing this dichotomy with a continuum-based intervention framework. In practice, the main distinction between "passive" and "active" restoration lies primarily in the timing and extent of human interventions. We apply the intervention continuum framework to forest, grassland, stream, and peatland ecosystems, emphasizing that a range of restoration approaches within the scope of ecological or ecosystem restoration are typically employed in most projects, and all can contribute to the recovery of native ecosystems and prevention of further degradation. As restoration is fundamentally about the recovery of ecosystems, eliminating human sources of degradation is essential to enable ecosystem recovery processes, regardless of subsequent interventions that may be needed to assist recovery. Our review of restoration practices involving different levels of intervention highlights the benefits of recognizing a broader suite of restoration interventions in the financial and policy frameworks that currently underpin restoration activity. Effective restoration interventions emerge from an understanding of nature's intrinsic recovery potential and overcoming specific obstacles that limit this potential.

Mammal Study, 2017

Disturbance events can alter habitat properties, leading to species displacement, isolation, and/... more Disturbance events can alter habitat properties, leading to species displacement, isolation, and/or local extinction. Therefore, understanding the interactions of potential ecological drivers on native and introduced wildlife species post-fire is critical to understand influences on distribution. We studied native Arizona gray squirrels (Sciurus arizonensis), which are believed to favor dense riparian habitat, and introduced Abert's squirrels (S. aberti), which prefer open ponderosa pine (Pinus ponderosa) forests. We examined how uncommon native Arizona gray squirrels and introduced Abert's squirrels used areas previously burned by widespread fires more than a decade prior to our study. To determine how past fire may affect squirrel habitat, we examined squirrel use and occupancy within fire altered habitats and used distance sampling to determine squirrel distribution, feeding, and nest use within a mosaic of burn severities. Occupancy and habitat use indicated that introduced Abert's squirrels readily used post-fire conditions more than native Arizona gray squirrels, likely due to the opening of a dense understory. Arizona gray squirrels remained in unburned riparian areas; therefore, fire affected riparian areas can be directly targeted for management to increase abundance of the native species.

Restoration Ecology, 2018

Canadian Journal of Forest Research, 2018

Dry mixed-conifer forests are widespread in the interior Pacific Northwest, but their historical ... more Dry mixed-conifer forests are widespread in the interior Pacific Northwest, but their historical fire regimes are poorly characterized, in particular the relative mix of low- and high-severity fire. We reconstructed a multi-century history of fire from tree rings in dry mixed-conifer forests in central Oregon. These forests are dominated by ponderosa pine (Pinus ponderosa Lawson & C. Lawson), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), and grand fir (Abies grandis (Douglas ex D. Don) Lindl.). Across four, 30-plot grids of ∼800 ha covering a mosaic of dry mixed-conifer forest types, we sampled 4065 trees for evidence of both high- and low-severity fire. From 1650 to ∼1900, all four sites sustained frequent, often extensive, low-severity fires that sometimes included small patches of severe fire (50–150 ha during 18%–28% of fire years). Fire intervals were similar among sites and also among forest types within sites (mean intervals of 14–32 years). To characterize the continuo...

Dendrochronologia, 2018

The influence of tree age on climate sensitivity is of central importance in dendrochronology. Re... more The influence of tree age on climate sensitivity is of central importance in dendrochronology. Recent research has highlighted the disparate nature of agedependent growth responses across species and geographic locations. We compared growth sensitivity and the influence of climate in Pinus edulis (Piñon) of varying ages at Dinosaur National Monument (DINO, northwestern Colorado, USA. Piñon is a particularly good species for this study because of its long lifespan and climate sensitivity, and the DINO site is at the northern extreme of

Better understanding and prediction of tree growth is important because of the many ecosystem ser... more Better understanding and prediction of tree growth is important because of the many ecosystem services provided by forests and the uncertainty surrounding how forests will respond to anthropogenic climate change. With the ultimate goal of improving models of forest dynamics, here we construct a statistical model that combines complementary data sources – tree-ring and forest inventory data. A Bayesian hierarchical model is used to gain inference on the effects of many factors on tree growth – individual tree size, climate, biophysical conditions, stand-level competitive environment, tree-level canopy status, and forest management treatments – using both diameter at breast height (DBH) and tree-ring data. The model consists of two multiple regression models, one each for the two data sources, linked via a constant of proportionality between coefficients that are found in parallel in the two regressions. The model was applied to a dataset developed at a single, well-studied site in th...

Genetics and conservation …, 1991

8 A Comparison of Methods for Assessing Genetic Variation in Plant Conservation Biology BARBARA A... more 8 A Comparison of Methods for Assessing Genetic Variation in Plant Conservation Biology BARBARA A. SCHAAL, WESLEY J. LEVERICH, and ... The classic studies of Clausen et al.(1948) on Achillea lanulosa ecotypes show that the morphological differences of ecotypes are ...

Forest death from extreme drought and wildfires are reducing regional carbon reservoirs and overa... more Forest death from extreme drought and wildfires are reducing regional carbon reservoirs and overall forest sequestration capacity. At the same time, land use practices and development have increased the vulnerabil- ity of some forests during extreme droughts. The intent of this fact sheet is to explain the basics of the car- bon cycle in southwestern forests. It also summarizes how carbon cycling patterns are most likely to change in the coming years to decades in the Southwest.