Savannas occur where trees and grasses interact to create a biome that is neither grassland nor forest. Woody and gramineous plants interact by many mechanisms, some negative (competition) and some positive (facilitation). The strength and sign of the interaction varies in both time and space, allowing a rich array of possible outcomes but no universal predictive model. Simple models of coexistence of trees and grasses, based on separation in rooting depth, are theoretically and experimentally inadequate. Explanation of the widely observed increase in tree biomass following introduction of commercial ranching into savannas requires inclusion of interactions among browsers, grazers, and fires, and their effects on tree recruitment. Prediction of the consequences of manipulating tree biomass through clearing further requires an understanding of how trees modify light, water, and nutrient environments of grasses. Understanding the nature of coexistence between trees and grass, which under other circumstances...

Tree-grass interactions in Savannas

Several recent papers have suggested replacing the terminology of fire intensity and fire severity. Part of the problem with fire intensity is that it is sometimes used incorrectly to describe fire effects, when in fact it is justifiably restricted to measures of energy output. Increasingly, the term has created confusion because some authors have restricted its usage to a single measure of energy output referred to as fireline intensity. This metric is most useful in understanding fire behavior in forests, but is too narrow to fully capture the multitude of ways fire energy affects ecosystems. Fire intensity represents the energy released during various phases of a fire, and different metrics such as reaction intensity, fireline intensity, temperature, heating duration and radiant energy are useful for different purposes. Fire severity, and the related term burn severity, have created considerable confusion because of recent changes in their usage. Some authors have justified this by contending that fire severity is defined broadly as ecosystem impacts from fire and thus is open to individual interpretation. However, empirical studies have defined fire severity operationally as the loss of or change in organic matter aboveground and belowground, although the precise metric varies with management needs. Confusion arises because fire or burn severity is sometimes defined so that it also includes ecosystem responses. Ecosystem responses include soil erosion, vegetation regeneration, restoration of community structure, faunal recolonization, and a plethora of related response variables. Although some ecosystem responses are correlated with measures of fire or burn severity, many important ecosystem processes have either not been demonstrated to be predicted by severity indices or have been shown in some vegetation types to be unrelated to severity. This is a critical issue because fire or burn severity are readily measurable parameters, both on the ground and with remote sensing, yet ecosystem responses are of most interest to resource managers.

/pdf/fire-intensity-fire-severity-and-burn-severity-a-brief-3f34ow4qed.pdf

Fire intensity, fire severity and burn severity: a brief review and suggested usage

https://www.fs.fed.us/rm/pubs_other/rmrs_1999_neary_d001.pdf

Fire effects on belowground sustainability: a review and synthesis

Plant invasions are widely recognized as significant threats to biodiversity conservation worldwide. One way invasions can affect native ecosystems is by changing fuel properties, which can in turn affect fire behavior and, ultimately, alter fire regime characteristics such as frequency, intensity, extent, type, and seasonality of fire. If the regime changes subsequently promote the dominance of the invaders, then an invasive plant–fire regime cycle can be established. As more ecosystem components and interactions are altered, restoration of preinvasion conditions becomes more difficult. Restoration may require managing fuel conditions, fire regimes, native plant communities, and other ecosystem properties in addition to the invaders that caused the changes in the first place. We present a multiphase model describing the interrelationships between plant invaders and fire regimes, provide a system for evaluating the relative effects of invaders and prioritizing them for control, and recommend ways...

https://www.jstor.org/stable/10.1641/0006-3568%282004%29054%5B0677%3AEOIAPO%5D2.0.CO%3B2

Effects of Invasive Alien Plants on Fire Regimes

Wildfire as a hydrological and geomorphological agent

FIRE DYNAMICS. Combustion Processes and Heat Transfer. Fuels and Fire Behavior. SOIL REPONSES. Soil Resource. Physical Soil System. Chemical Soil System. Biological Soil System. RESPONSES OF OTHER RESOURCES. Water. Vegetation. Wetlands and Riparian Ecosystems. Air. Cultural Resources. MANAGEMENT IMPLICATIONS. Economic Considerations. Fire in Ecosystem Management. Index.

Fire's effects on ecosystems

Riparian ecosystems and their management: Reconciling conflicting uses

The Madrean Archipelago or Sky Islands region of the southwestern United States and northern Mexico is recognized for its unique biological diversity, natural beauty, and cultural heritage. This 2012 conference brought together scientists, managers, students, and other interested parties from the United States and Mexico to share their knowledge and passion about the region and to identify needs and creative solutions for existing and emerging problems. More than 300 people attended the conference including a large and energetic contingent from northern Mexico. The conference provided a forum to update the state-of-knowledge that has evolved since the first conference in 1994 and the second conference in 2004. It also provided a setting for the formation of new friendships and partnerships. These proceedings contain 80 of the 190 oral and poster presentations and all abstracts from the plenary sessions and the concurrent sessions. Abstracts in Spanish are included. Topics include climate change in the Sky Island Region, southwestern cienegas, the Northern Jaguar Reserve, amphibian conservation, biodiversity of plants and animals, fire effects, grasslands, and human impacts, and tools. The conference hosted a symposium about Santa Cruz River Watershed Conservation. A lively open forum at the end of the conference generated a list of future scientific and management needs for the Madrean Archipelago and a commitment to increase international cooperation. Mexican participants graciously offered to host the next conference, Speakers stressed the importance for all interested parties to collaborate - to work side-by-side and constantly inform one another about relevant research, timely events, and cross-pollination opportunities throughout the region.

Merging science and management in a rapidly changing world: Biodiversity and management of the Madrean Archipelago III and 7th Conference on Research and Resource Management in the Southwestern Deserts; 2012 May 1-5; Tucson, AZ

Conservation in protected areas has focused on preserving biodiversity of ecosystems and species, whereas conserving the genetic diversity contained within species has historically often been ignored. However, maintaining genetic diversity is fundamental to food security and the provision of raw materials and it is best preserved within plants' natural habitats. This is particularly true for wild plants that are directly related to crop species and can play a key role in providing beneficial traits, such as pest or disease resistance and yield improvement. These wild relatives are presently threatened due to processes of habitat destruction and change and methodologies have been adapted to provide in-situ conservation through the establishment of genetic reserves within the existing network of protected areas.Providing a long awaited synthesis of these new methodologies, this book presents a practical set of management guidelines that can be used for the conservation of plant genetic diversity of crop wild relatives in protected areas.

/pdf/integrated-watershed-management-connecting-people-to-their-222rc4ruv1.pdf

Peter F. Ffolliott

Papers

Fire effects on belowground sustainability: a review and synthesis

Fire's effects on ecosystems

Riparian ecosystems and their management: Reconciling conflicting uses

Merging science and management in a rapidly changing world: Biodiversity and management of the Madrean Archipelago III and 7th Conference on Research and Resource Management in the Southwestern Deserts; 2012 May 1-5; Tucson, AZ

Integrated Watershed Management: Connecting people to their land and water