Plant community response to fuel break construction and goat grazing in a southern California shrubland

Background Shrub-dominated ecosystems in California are widespread and provide invaluable ecosystem services to surrounding human-dominated communities. Yet shrublands, especially those at the wildland-urban interface, are at risk of degradation due to increasing wildfire frequency. Strategically placed fuel breaks are an important fuel management technique for reducing fire risk to neighboring communities and natural landscapes. Fuel breaks in shrub-dominated ecosystems are typically linear features where woody biomass is reduced, thereby providing fire suppression opportunities that limit fire spread. While fuel breaks are important for tactical response to fire, they can also affect the composition and structure of shrubland habitats. To understand the ecological changes resulting from fuel treatments in southern California chaparral, we measured vegetation change associated with fuel management techniques on a recently created fuel break established around the Lake Morena community on the Cleveland National Forest. The area was initially treated with cut and pile burning, then treated with herbicide, and 2 years later was subjected to short-term grazing by 1200 goats. The purpose of this study is to (1) evaluate the compositional and structural differences associated with fuel break creation and (2) quantify compositional shifts in herbaceous and woody vegetation caused by short-duration goat grazing as a method of fuel break maintenance. Results Plots on the fuel break and in untreated adjacent chaparral exhibited significantly different species assemblages. Total herbaceous cover (both native and non-native) was 92 times greater on the fuel break than in adjacent chaparral-dominated wildlands, and native shrub cover was 55.3 times greater in untreated adjacent chaparral than on the fuel break. Goats had a significant impact on reducing native and non-native herbaceous cover (87% reduction in cover, 92% reduction in height), but were ineffective at reducing the cover and height of most woody species such as Adenostoma fasciculatum, Eriogonum fasciculatum, Quercus berberidifolia, and Artemisia tridentata. Conclusion Initial fuel break creation was effective at reducing native woody cover and height, simultaneously giving rise to an abundance and diversity of native and non-native herbaceous species. Targeted goat grazing was successful at reducing herbaceous biomass but was ineffective at reducing woody biomass which is often one of the most important goals for fuel management in chaparral ecosystems. In areas where control of woody biomass is the primary objective, land managers should consider grazing duration and plant species composition when contemplating goats as a tool for fuel break maintenance.

Plant community response to fuel break and goat grazing in southern California

Background: California is a global biodiversity hotspot, yet increased urbanization of wildlands, warming temperatures, and invasion of nonnative species pose serious risks to these areas due to an increase in wildfire frequency. Fuel management is a tool for reducing fire risk to neighboring communities and natural resources that involves a two-step process requiring an initial reduction of woody vegetation followed by a repeated control of woody plants and reduction of herbaceous cover. To understand the compositional and structural changes resulting from fuel treatment methods in southern California chaparral, we evaluated the compositional and structural impacts of a recently created fuel break established around the Lake Morena community on the Cleveland National Forest. The area was initially treated with cut and pile burning, then treated with herbicide, and lastly grazed by 1,200 goats. The purpose of this study is to (1) evaluate the compositional and structural differences associated with the initial fuel break, and (2) quantify compositional shifts in herbaceous and woody vegetation caused by goat grazing over time. Results: Plots on fuel breaks and in adjacent wildlands exhibited significantly different species assemblages. Total herbaceous cover (both native and nonnative) was 92 times greater on fuel breaks than in adjacent chaparral-dominated wildlands and native shrub cover was 55.3 times greater in adjacent wildlands than on fuel breaks. Goats had a significant impact on reducing native and nonnative herb cover (87% reduction in cover, 92% reduction in height), but were ineffective at reducing the cover and height of most woody species such as Adenostoma fasciculatum, Eriogonum fasciculatum, Quercus berberidifolia, and Artemisia tridentata. However, goats were found to be effective in controlling nonnative grasses including Bromus diandrus and Bromus madritensis. Conclusion: Initial fuel break creation was effective at reducing wood biomass and height, simultaneously giving rise to an abundance and diversity of native and nonnative herbaceous species. Although targeted goat grazing was successful at reducing herbaceous biomass, it was ineffective at reducing woody biomass which is often one of the most important goals for fuel management in chaparral ecosystems.

Can Shrub Flammability be Affected by Goat Grazing? Flammability Parameters of Mediterranean Shrub Species under Grazing

In this study, we evaluated changes in the potential flammability of different Mediterranean shrub species in a pine (Pinus pinea) forest in the Doñana Natural Park (of SW Spain) as a result of goat grazing. Plant height, total biomass, fine fuel biomass and leaves/wood ratio were measured in individual plants of each species in both grazed and ungrazed areas. Moisture content, mean time of ignition, mean time of combustion, gross heat of combustion (GHC) and flammability class of the studied shrub species were determined in the laboratory. The results of this experiment showed that grazing influenced the flammability characteristics of the studied shrub species. However, the strength of this effect was insufficient to modify the flammability index of these plants, except in the case of Myrtus communis, in which grazed plants presented a lower flammability index. According to Valette’s classification, Cistus salviifolius, Halimium halimifolium and Pistacea lentiscus are flammable species, Rosmarinus officinalis is a flammable-highly flammable species, and M. communis is non-flammable. The GHC values obtained were generally “intermediate”, except for those of R. officinalis, which were classified as “high”. The flammability parameters of the study species did not show a very marked trend in relation to grazing, but the vertical structure of plants did change by presenting reduced biomass of leaves and fine twigs. This change altered the physical characteristics of these plants and possibly acted to reduce the inherent fire risk of the shrublands.

Evaluation of non-carcass components of goat grazing in Caatinga rangeland supplemented with spineless cactus and native plants

The objective of this study was to evaluate non-carcass components of goats submitted to grazing in the Caatinga rangeland and supplemented with spineless cactus (Nopalea cochelinifera Salm Dick), Jitirana hay (Merremia aegyptia L. Urban) and Mororó hay (Bauhinia cheilanta Bong Stend). Thirty male goats (castrated), with no defined breed, with an initial mean body weight of 19 ± 0.35 kg and approximately 90 days of age were used. The treatments consisted of grazing without supplementation (GWS), grazing + Jitirana hay (GJ); grazing + Jitirana hay + spineless cactus (GJSC); grazing + Mororó hay (GM); grazing + Mororó hay + spineless cactus (GMSC). The means of the variables were tested by Tukey's test at 5% probability. The goats fed GWS, GJSC, GM and GMSC presented higher weights and yields of the diaphragm, and the spleen weight (p < 0.05). The highest yield of omasum (p < 0.05) occurred with goats fed GJ treatment. There were treatments (p < 0.05) on omental fat weight and leg yield, with the highest values for goats, fed GWS, GJSC, GM, and GMSC. The "Buchada" EBW-1 yield was higher (p < 0.05) for animals fed GWS. Feeding supplementation of goats grazing in the Caatinga had few influences on weights and yields of non-carcass components.

The impact of cutting prior to goat grazing on variegated thistle (Silybum marianum)

Variegated thistle (Silybum marianum) is a prevalent weed on the East Coast of the North Island of New Zealand. Goats may provide a novel management tool to control thistles, but little is known about how cutting thistles prior to grazing affects thistle consumption by goats. This study investigated the extent to which goats consume either uncut entire variegated thistle plants or cut thistles. Eight groups of three goats were presented with thistle vegetation in each of two replicate 1-hour feeding sessions on 2 consecutive days. Averaged over both days, in the cut treatment, goats consumed 99% of the leaves that had been removed from the thistles and reduced the ground cover of the thistle plants by 68%. In the uncut treatment, ground cover of the thistles was reduced by 46%. A combination of cutting and goat grazing is likely to be a useful tool for stopping variegated thistle debris from smothering pasture and for inhibiting seed setting. Further work is required to test this at paddock scale.