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Soil–vegetation relationships in cerrados under different fire frequencies

Abstract

Abstract 

Fire is an important ecological factor that structures savannas, such as the cerrado, by selecting plant species and altering soil nutrient content. In Emas National Park, central Brazil, we compared soils under three different fire regimes and their relationship to the cerrado species they support. We collected 25 soil and vegetation samples at each site. We found differences in soil characteristics (p < 0.05), with fertility and fire frequency positively related: in the annually burned site we found higher values of organic matter, nitrogen, and clay, whereas in the protected site we detected lower values of pH and higher values of aluminum. We also observed differences in plant community structure, with distinct floristic compositions in each site. Floristic composition was more related to sand proportion (intra-set correlation = 0.834). Different fire frequencies increase environmental heterogeneity and beta diversity in the Brazilian cerrado.

Keywords

Key words: Cerrado Fire Savanna Soil–vegetation relationships 

Ano de Publicação: 2008

Response of Acacia Sieberiana to Repeated Experimental Burning

Abstract

We conducted a study on how Acacia sieberiana respond to repeated burning in the Kidepo National Park in northeastern Uganda. The study was conducted to understand effects of common burning regimes (early dry season, late dry season, and no burn [control]) in the area on Acacia sieberiana. The three treatments were applied for three consecutive years to 14 replicate blocks in a randomized block design. All A. sieberiana trees were number tagged and monitored for height and girth (diameter at breast height) growth. All fires were set as head-fires and attained intensity ranging between 422 and 5693 kW · m−1. Both early and late dry season burning increased the number of small (< 49 cm) A. sieberiana trees after 2 yr. Burning did not affect the growth rates. Although the number of trees < 49 cm increased after 2 yr, the mortality in this height class was also increased by the late dry season burning, and after 3 yr of consecutive burning there were no statistical treatment differences in the height class < 49 cm. Late dry season burning also led to high mortality among trees > 250 cm in the third year. Mortality attributed to elephant browsing was important in all treatments but a substantial portion of mortality could not be attributed to any particular cause. In the late burn, fire was the most important mortality factor. Thus, 2 yr of burning may be used as a tool to stimulate recruitment of A. sieberiana, but additional years of late dry season burning will increase the mortality of older trees.


Ano de Publicação: 2008

Recruitment filters in a perennial grassland: the interactive roles of fire, competitors, moisture and seed availability

Summary

1. Demographic processes, particularly the recruitment of seedlings, are critical to the long-term survival and re-establishment of plant populations. In many perennial grasslands successful recruitment is a rare event that requires the simultaneous favourable alignment of several environmental variables.

2. Although a few empirical studies have examined demographic processes in perennial grasslands, most of these studies investigate the impact of only one or two environmental factors in isolation. Those studies would lead us to expect that seed availability, irrigation and burning, enhance recruitment rates whereas the presence of established competitors substantially lowers recruitment rates. But how these factors, or recruitment filters, act in concert and how they influence the different components of the recruitment process such as seedling emergence, survival and growth is not understood.

3. For this reason we explore the relative and combined influence of four factors – seed availability, irrigation, competition by the established vegetation, and fire – on the recruitment process of a perennial grass (Stipagrostis uniplumis ) in semi-arid savanna. We used a full factorial experiment to determine how these four factors influence emergence, growth, survival and flowering of seedlings. 

4. Our results show that all of the factors affected some stage of the recruitment process but not all significant effects contributed to enhancing the final number of recruits. 

5. We found enhanced seed availability to significantly enhance rates of seedling emergence but to play no further role in the recruitment process. Competition by the established vegetation exerted a strong negative effect on every step of the recruitment process. Irrigation had a minor effect on recruitment. It enhanced rates of flowering and survival during the growing season but the effect of the stimulus was short-lived and did not influence later stages of the recruitment process.

6. In contradiction to existing theory, seedling recruitment does therefore not seem to be limited to above average rainfall years. Fire acted similarly to the removal of competitors; that is, it positively affected seedling emergence, growth, flowering and survival.

7. Synthesis . We conclude that recruitment is not limited to above average rainfall years but triggered by events that open up the grass canopy and reduce the abundance of competitors. Specifically it appears that periodic fires enable the recruitment of new individuals into the population. This study shows that fire can play an important positive role in individual turnover of semi-arid perennial grass populations.

Key-words: demography, emergence, full factorial experiment, intraspecific competition, irrigation, recruitment limitation, seed addition, seedling survival, semi-arid savanna, Stipagrostis uniplumis

Ano de Publicação: 2008

Proceedings of the 2002 Fire Conference: Managing Fire and Fuels in the Remaining Wildlands and Open Spaces of the Southwestern United States December 2–5, 2002 San Diego, California

Abstract

Narog, Marcia G., technical coordinator. 2008. Proceedings of the 2002 fire conference: managing fire and fuels in the remaining wildlands and open spaces of the Southwestern United States. Gen. Tech. Rep. PSW-GTR-189. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 363 p. Many issues confront scientists, land managers, policymakers, and the public who deal with or are affected by management of fire and fuels across the southwestern United States (Utah, Colorado, Arizona, Nevada, New Mexico, and California). The 2002 Fire Conference was convened to tackle these concerns. It began with a plenary session addressing the central problems of fire and fuels management in the Southwest. Concurrent sessions with over 100 oral presentations covered a wide range of topics, including fire ecology, fire behavior, fire history, fire prevention, fire education, restoration and rehabilitation, air quality, wildlife-fire interactions, fire planning, watershed responses to fire, invasive species responses to fire, National Environmental Policy Act and other regulations, and vegetation-fire interactions. More than 50 posters displayed in an afternoon session rounded out the program. The 39 papers and 17 extended abstracts included in this volume serve as a reference for the management of fire and fuels concerns in the southwestern United States. 

Keywords: fire behavior, fire ecology, vegetation treatment, watershed response, wildfire, wildlife response.

Ano de Publicação: 2008

Herder Perceptions on Impacts of Range Enclosures, Crop Farming, Fire Ban and Bush Encroachment on the Rangelands of Borana, Southern Ethiopia

Abstract

This study focuses on community-based knowledge to analyze the impacts of range enclosures, crop farming, fire suppression and bush encroachment on the communal rangelands of Borana, southern Ethiopia. The knowledge of local herders is the basis for decision making in the utilization and management of grazing lands. We used Borana oral history associated with the period of the gada system to reconstruct environmental change that spans a period of 48 years. Our results show that the use of communities’ perceptions as a basis for evaluating the impacts of land use change on the environment makes an important methodological contribution. Communities’ responses to changing land use resulted in the development of range enclosures, the expansion of crop farming and the fragmentation of the communal rangelands, while the suppression of fire contributed to the expansion of bush encroachment. The overall impact was forage scarcity and greater vulnerability of stock during drought years. We conclude that policymakers could use communities’ knowledge of environmental change to improve the use of the rangelands. We propose that sustainable use of the southern rangelands in the future will require a greater focus on regulating the expansion of enclosures, crop farming and ranching, as well as reintroducing fire where necessary, to control the expansion of bush cover.

Keywords

Key words: Bush encroachment Community perception Environmental history Fire ban Land use Policy Rangeland development 

Ano de Publicação: 2008

Fire Regimes, Fire Ecology, and Fire Management in Mexico

I propose several broad fire regimes and provide an analysis of fire ecology for the principal vegetation types in Mexico. Forty percent of Mexican ecosystems are firedependent (pine forests, several oak forests, grasslands, several shrublands, savannas, palm lands, wet prairies, ‘‘popal’’ and ‘‘tular’’ swamps), 50% are fire-sensitive (tropical rain forests and tropical seasonal forests, tropical cloud forests, mangrove, fir forests, several oak forests, and several shrublands), and the remaining 10% fall into fire-influenced (such as several gallery forests) and fire-independent categories (shrublands in most xeric environments, very high-altitude prairies). I also present an analysis of current fire-management trends, highlighting the trend toward integral fire management, which merges prevention and control, community-based fire management, and ecological fire management.

Ano de Publicação: 2008

Ecophysiological responses of Chihuahuan desert grasses to fire

a b s t r a c t

To better understand the effects of fire in the Chihuahuan desert, gas exchange characteristics of two dominant grass species, Bouteloua eriopoda and Aristida purpurea, and soil nitrogen availability were studied in response to prescribed fire at the Jornada Experimental Range in southern New Mexico. Burned and unburned plant individuals were measured before and after fire. Rates of net photosynthesis and stomatal conductance were highest in burned individuals, with those of A. purpurea exceeding B. eriopoda. Soil nitrogen supply rates increased compared to unburned controls. Similar to other grasslands where fire is common, physiological characteristics of vegetation responded positively. These adaptations indicate that fire may be beneficial in the preservation and restoration of native grasses.


Ano de Publicação: 2008

Subsides to the creation of a regional model of forest fire hazard: Taquari River Springs Park, MS—A case study

Abstract

Using map algebra, in the GIS (geographic information system) environment, this study integrates the B-RAMS, Brazilian Regional Atmospheric Models Software (CPTEC, 2005) climate model data with remote sensing data, intending to obtain a wildfire hazard map. The Taquari River Springs Park (TRSP) was chosen as a case study, due to the presence of springs which are considered important contributors to the Upper Paraguay River Basin, and it also contains essential remnants of the Cerrado Biome. The B-RAMS model has provided relative humidity, com ponents of the horizontal wind and temperature. The TRSP land cover was identified by object oriented classification of a LANDSAT ETM+ image, supported by field observations. From the land cover phytophysionomic type characterization, a forest wildfire fuel map has been elaborated. The integration of the different maps has been made using a GIS, and a new map with its associated GIS database was generated showing the most vulnerable zones to wildfire hazard. 

Keywords: Forest fuel; Atmospheric modeling; Remote sensing; Map algebra

Ano de Publicação: 2007

SIMULANDO PADRÕES DE INCÊNDIOS NO PARQUE NACIONAL DAS EMAS, ESTADO DE GOIÁS, BRASIL

RESUMO

Utiliza-se um modelo probabilístico espacialmente explícito para prever a área final ou padrão atingido por incêndios históricos ocorridos no Parque Nacional das Emas (PNE) , estado de Goiás, Brasil. O modelo trata a paisagem como um um reticulado bidimensional de células quadradas com dimensões de 30 metros. Cada célulaé ocupada por um autômato finito e cada autômato é conectado a seus oito vizinhos adjacentes. O autômato pode assumir os estados inerte, queimando ou queimado. O fogo propaga de uma célula ignizada para qualquer uma das oito células vizinhas como um evento estocástico independente com probabilidade I, onde I pode variar de 0 a 1. Cada célula queima por um simples passo de tempo de comprimento variável, e a extinção do incêndio ocorre se novos sítios não forem ignizados em um dado passo de tempo. Dentre os processos que afetam o padrão de propagação do fogo inclui-se, de imediato, os efeitos de variações da carga combustível. Áreas recém queimadas possuem menos combustível acumulado e com isso a probabilidade de propagação do fogo é menor. O modelo foi implementado no ambiente computacional TerraME, que oferece uma linguagem de alto nível para a descrição de modelos, um conjunto de estruturas de dados espaço-temporais para a representação e simulação dos modelos, um modulo para o gerenciamento e análise de dados espaçoo-temporais integrado  a um sistema de informações geográficas. Experimentos de simulações do modelo foram executados visando prever a área atingida por incêndios ocorridos no PNE.

Ano de Publicação: 2007

Rural Livelihoods and Burning Practices in Savanna Landscapes of Nusa Tenggara Timur, Eastern Indonesia

Abstract

ABSTRACT 

Substantial attention has been given in recent years to forest and peatland degradation, transboundary haze, and biodiversity and economic impacts associated with major fire events in perhumid western Indonesia. Conversely, little information is available concerning underpinning conditions associated with burning practices and resultant fire patterns in other parts of the Indonesian archipelago, especially in markedly seasonally dry regions. As part of a broader study examining the patterning and drivers of burning in the monsoonal province of Nusa Tenggara Timur (NTT), the paper explores cultural, socioeconomic, biophysical, and, in discussion, political dimensions associated with landscape-scale patterns of burning at each of two village locations on the islands of Sumba and Flores. Assembled data illustrate that: (1) study villages are reliant on a range of subsistence agricultural activities, particularly annual food crops, livestock (especially pigs), and forest products; (2) while villages encompass mostly extensive areas of grassland savanna, proportionately most income/products are derived from limited areas of arable agricultural and very diminished forested lands; (3) despite this, considerable economic potential exists for developing certain tree products especially in agro-forestry settings, and more intensive livestock management; (4) these patterns are representative generally of surrounding regional agricultural landscapes. While burning is used as an essential agricultural management tool in defined seasonal contexts in all study villages, the reality is that today much burning is unmanaged and uncontrolled, with attendant significant economic impacts. As for western Indonesia, underlying drivers of such behavior are multiple and complex, but pointedly include: rapid societal change; conflicts within and between villages, and between villages and regulatory authorities (especially the Forestry Department), over access to land and resources; and continued nonrecognition in national and provincial fire policy frameworks of the practical necessity for using fire (wisely and safely) in many agricultural contexts. It is axiomatic that, without effective fire management and a supportive policy environment, sustainable livelihoods development will continue to be elusive in fire-prone savanna landscapes of eastern Indonesia.

Key words: Fires burning livelihoods agriculture savanna forest eastern Indonesia policy 

Ano de Publicação: 2007