Oak Grassland Research Articles

Corrigendum to: Yield and nutritional quality of intercropped forages for organic production in a hot-summer Mediterranean oak grassland ecosystem

Corrigendum to: Yield and nutritional quality of intercropped forages for organic production in a hot-summer Mediterranean oak grassland ecosystem

Yield and nutritional quality of intercropped forages for organic production in a hot-summer Mediterranean oak grassland ecosystem

Context Forage cultivation plays a pivotal role in sustaining ruminants in resource-limited ecosystems such as the hot-summer Mediterranean agroforestry systems of the Iberian Peninsula comprising oak trees (Quercus spp.) and grassland species. Intercropping techniques can enhance forage yields and nutritional quality. Aims This study assessed the yield and nutritional quality of organic forage mixtures in an Iberian oak grassland ecosystem. Methods Six forage associations were assessed over two growing seasons: vetch (Vicia sativa L.)–triticale (Triticum × Secale), vetch–rye (Secale cereale), vetch–oat (Avena sativa), pea (Pisum sativum L.)–triticale, pea–rye, and pea–oat. The data were analysed using a multivariate procedure. Key results Differences in forage composition influenced nutritional quality but not yield. Vetch-based associations exhibited higher crude protein, calcium, phosphorus, potassium, zinc, magnesium, manganese and sulfur contents, along with lower proportions of neutral-detergent fibre and ether extract. The vetch–oat mixture emerged as the highest quality association. Interannual variations in precipitation and temperature caused differences in forage yield, with greater values observed in 2020 than in 2019. Forage associations also had significantly higher nutritional quality in 2020 (increased protein and mineral content, and decreased neutral detergent fibre and lignin). Conclusions All forages demonstrated satisfactory performance and quality, even in the drier conditions of 2019, suggesting high resilience and adaptability to hot-summer Mediterranean oak grassland ecosystems. Implications The findings of this study are relevant for organic farmers in resource-limited ecosystems. This information empowers them to select the most suitable forage species based on the specific agroclimatic conditions of each growing season.

Trends in Lesser Prairie-Chicken Habitat Extent and Distribution on the Southern High Plains

The lesser prairie-chicken (Tympanuchus pallidicinctus) is a species of prairie grouse that occupies grassland ecosystems in the Southern and Central High Plains of the Great Plains. Reduced abundance and occupied ranges have led to increased conservation efforts throughout the species’ range. Habitat loss is considered the predominant cause of these declines. In the Southern High Plains of Texas and New Mexico, lesser prairie-chicken habitat corresponds to the Sand Shinnery Oak Prairie Ecoregion, which is comprised of a mixture of sand shinnery oak (Quercus havardii)-dominated grasslands, sand sagebrush (Artemisia filifolia)-dominated grasslands, and mixed grasslands. In sand shinnery oak–grassland communities, conversion to row-crop agriculture, continuous unmanaged livestock grazing, restriction of natural fire, invasive plant species (e.g., mesquite (Prosopis spp.)), extensive use of herbicides, energy development, and a variety of other factors have also negatively affected ecosystem extent and function. We integrated historical maps and remote sensing-derived information to measure trends in the extent and geographical distribution of sand shinnery oak prairies in eastern New Mexico and northwest Texas. Potential lesser prairie-chicken habitat was reduced by 56% from a potential of 43,258 km2 to 18,908 km2 in ~115 years (since pre-settlement). Our assessment indicated both mixed grasslands and sand shinnery oak-dominated grasslands were transformed from large parcels of existing vegetation communities to urban settlements, row crops, roads, and industrial land uses by the 1970s. Currently, potential habitat is highly fragmented and restricted to isolated locations in Texas and New Mexico, with an increasing dominance in mixed grasslands, especially in the southeastern portion of the lesser prairie-chicken range. Sand shinnery oak-dominated grasslands have been declining rapidly, from 69% of its potential extent in 1985, 65% in 1995, 54% in 2005, to 42% in 2015. Mixed grasslands drastically declined to 50% of its potential distribution by 1985. Since then, it has been stable until the 2005–2015 period when it declined to 45% of its potential extent. Based on the 2015 assessment, the current potential habitat for lesser prairie-chicken is estimated at 18,908 km2 (1,890,800 ha or 4.6 million acres), where 13,126 km2 corresponds to mixed grasslands and 5782 km2 corresponds to sand shinnery oak-dominated grasslands.

The cost of firewood

Firewood management is a key component of hunter-gatherer subsistence. the costs of time and labour required to gather firewood can affect labour allocation, social organisation, foodways and settlement patterns. An important factor in understanding the costs of fuel gathering is the availability of wood, the most common source of fuel, on the landscape. this study uses survey and time trials to quantify fuel availability and gathering time of a single day’s firewood in an unexploited environment in a northern California blue oak grassland. the study found that the available wood fuel in a central place territory would be consumed in under a year. this suggests that changes in the lifeways of prehistoric California hunter-gatherers may have in part been influenced by the need for fuel management.

Invasive Scotch broom (Cytisus scoparius, Fabaceae) and the pollination success of three Garry oak-associated plant species

A growing number of studies have reported an effect of invasive species on the pollination and reproductive success of co-flowering plants, over and above direct competition for resources. In this study, we investigate the effect of the invader Scotch broom (Cytisus scoparius) on the visitation, pollen deposition, and female reproductive output of three co-flowering species (two native, one exotic) of the critically endangered Garry oak grassland ecosystem on the Saanich peninsula of Vancouver Island. The presence of C. scoparius was largely neutral, with the exception of some facilitation of pollen deposition to the native Camassia leichtlinii, the one species exhibiting pollinator overlap with Scotch broom. Yet, this pattern occurred despite a decreased visitation rate from pollinators. There was little observed effect of the invader on the native Collinsia parviflora or the exotic Geranium molle. Because broom was not favourited by any of the observed pollinators, this study provides evidence that the spread of Scotch broom is not due to the reduction of pollination success of natives nor is C. scoparius likely to be facilitating the pollination of other exotics in Garry oak ecosystem remnants.

Nesting ecology and nest survival of lesser prairie‐chickens on the Southern High Plains of Texas

ABSTRACTThe decline in population and range of lesser prairie‐chickens (Tympanuchus pallidicinctus) throughout the central and southern Great Plains has raised concerns considering their candidate status under the United States Endangered Species Act. Baseline ecological data for lesser prairie‐chickens are limited, especially for the shinnery oak‐grassland communities of Texas. This information is imperative because lesser prairie‐chickens in shinnery oak grasslands occur at the extreme southwestern edge of their distribution. This geographic region is characterized by hot, arid climates, less fragmentation, and less anthropogenic development than within the remaining core distribution of the species. Thus, large expanses of open rangeland with less anthropogenic development and a climate that is classified as extreme for ground nesting birds may subsequently influence nest ecology, nest survival, and nest site selection differently compared to the rest of the distribution of the species. We investigated the nesting ecology of 50 radio‐tagged lesser prairie‐chicken hens from 2008 to 2011 in the shinnery oak‐grassland communities in west Texas and found a substantial amount of inter‐annual variation in incubation start date and percent of females incubating nests. Prairie‐chickens were less likely to nest near unimproved roads and utility poles and in areas with more bare ground and litter. In contrast, hens selected areas dominated by grasses and shrubs and close to stock tanks to nest. Candidate models including visual obstruction best explained daily nest survival; a 5% increase in visual obstruction improved nest survival probability by 10%. The model‐averaged probability of a nest surviving the incubation period was 0.43 (SE = 0.006; 95% CI: 0.23, 0.56). Our findings indicate that lesser prairie‐chicken reproduction during our study period was dynamic and was correlated with seasonal weather patterns that ultimately promoted greater grass growth earlier in the nesting season that provided visual obstruction from predators. © 2014 The Wildlife Society.

Defining Conservation Strategies with Historical Perspectives: a Case Study from a Degraded Oak Grassland Ecosystem

Abstract: The restoration of degraded ecosystems can be constrained by uncertainty over former conditions and the relevance of the past given recent changes. It can be difficult to differentiate among contrasting hypotheses about past ecosystem function, and restoration efforts can emphasize species reestablishment without integrating the ecological and cultural processes that once determined their occurrence. As a case study, we analyzed historical descriptions of an endangered oak grassland ecosystem in southwestern British Columbia, Canada, to determine former conditions and assess their validity for defining restoration targets. Twenty‐three documents described this ecosystem from 1790 to 1951. Comparison of early survey records with contemporary occurrences suggests habitat loss of >95%. The identity and former range of most native plant species were poorly described, but accounts of ecosystem structure revealed a diversity of floral communities that has been much simplified. Fire, most likely set by indigenous peoples, interacted with edaphic and topographic factors to create this structural diversity. European settlers intensively modified the ecosystem with grazing, cultivation, and introduced flora. These transformations partly explain the current high levels of plant invasion. Restoration must target the ecosystems' former structural diversity and the ecological and cultural processes that maintained it. Given the recent impacts of fire suppression, habitat loss, and plant invasion, however, land managers must balance the reestablishment of historical processes with their potential negative effects in sites with numerous at‐risk species. This ecosystem was, and remains, part of a culturally modified landscape, where human activity has maintained unforested areas for millennia but now promotes mostly exotic flora. Although pre‐European conditions cannot be fully restored, the historical data provided restoration insights unobtainable from current biological studies emphasizing the end point of long‐term ecological change.

Preference and performance of a generalist insect herbivore on Quercus agrifolia and Quercus engelmannii seedlings from a southern California oak woodland

Knowledge of the impact that insects have on oak seedlings planted in restoration programs is important for land managers and those interested in maintaining visible populations of a variety of oak species. Once established as seedlings, oaks face potential herbivory by mammals and phytophagous insects. To determine potential damage of a common generalist insect herbivore on oak seedlings, we conducted performance and preference tests using a grasshopper ( Melanoplus sanguinipes) and two species of oaks ( Quercus agrifolia and Quercus engelmannii) occurring in a southern California oak grassland. Q. agrifolia is abundant and often used in restoration plantings, while Q. engelmannii has the smallest range of all native oaks in California. To quantify herbivore performance, we measured leaf area of 30 Q. agrifolia and 30 Q. engelmannii seedlings, and caged them individually with a single grasshopper within acetate feeding arenas. Performance then was estimated by determining amount of leaf area eaten and frass produced. Grasshopper preference for either oak species was estimated in replicated choice experiments. M. sanguinipes consumed significantly more leaf area and produced significantly more frass when feeding only on Q. agrifolia than when feeding solely on Q. engelmannii. Additionally, grasshoppers feeding on Q. agrifolia gained significantly more biomass, whereas those feeding on Q. engelmannii actually lost biomass. Q. agrifolia provided a better diet than Q. engelmannii for this grasshopper species, a result that has the potential to affect the success of seedling planting programs in areas where both oaks and M. sanguinipes occur.

Meditteranean Ecosystems and Vegetation Types in California and Israel

A comparison of climate, soils, vegetation, and biotic history of mediterranean ecosytems revealed closest ecological equivalence between the blue oak grassland in California and the vallonea oak grassland in Israel, both mediterranean oak savannas in which overall environmental resemblance seems closest. Ecological amplitude and syndynamics in most other comparable types are similar, but the chamise chaparral on non—calcic brown upland and lithosols differs from its maqui counterpart by its adverse influence on the ecosystem. Annual grasslands in California foothills are comparable to seral batha dwarfshrub and grassland in Israel as human—induced degradation stages of chaparral and maqui. For such ecological comparisons a holistic ecosystem approach seems more suitable than any preconceived phytoclimatic and climax concepts.