Changing the fire management regime in the renosterveld and lowland fynbos of the Bontebok National Park

This paper evaluates the history of fire management in the Bontebok National Park (3435 ha) over a period of almost four decades. A GIS database was compiled of all fires between 1972 and 2009 and the fire regime was analysed in terms of the frequency, season, size and cause of fires. Since the early 1970s, short interval burning was implemented to promote grazing for bontebok, but from 2004 the fire interval was lengthened to favour plant species diversity, an increasingly urgent conservation priority for the park. In total, 43 fires were recorded, ranging in size from 9 to 1007 ha, collectively spanning 14 013 ha. The majority of fires were large (100–500 ha), with fires of >100 ha accounting for 96% of the area burnt. The overall mean fire return period (FRP) for the park was 7.2 years, which is short judged by fynbos standards. FRPs under the old and new management regimes were 6.7 and 10.9 years respectively. Under the old regime, FRPs in renosterveld and fynbos were 5.8 and 8.0 years respectively. Large parts of the park repeatedly experienced fires at immature vegetation ages resulting in the elimination of slow-maturing seed-regenerating plant species such as Protea repens. Post-fire age distribution was highly skewed towards young vegetation, with 75% of fire-prone vegetation burning at post-fire ages of ≤7 years, and <10% of fire-prone vegetation surviving beyond 10 years of age. Prescribed and accidental fires respectively accounted for 70% and 30% of the total area burnt. Prescribed burning was mostly done in March–April, and only 8% of the total area burnt, burnt outside of the ecologically acceptable fire season. This study identified areas which have been subject to ecologically appropriate and inappropriate fire return intervals, providing a basis for informed future management and research.     

Fire and the relative roles of weather,climate and landscape characteristics in the Great Lakes‐St. Lawrence forest of Canada

Question: In deciduous‐dominated forest landscapes, what are the relative roles of fire weather, climate, human and biophysical landscape characteristics for explaining variation in large fire occurrence and area burned? Location: The Great Lakes‐St. Lawrence forest of Canada. Methods: We characterized the recent (1959–1999) regime of large (≥ 200 ha) fires in 26 deciduous‐dominated landscapes and analysed these data in an information‐theoretic framework to compare six hypotheses that related fire occurrence and area burned to fire weather severity, climate normals, population and road densities, and enduring landscape characteristics such as surficial deposits and large lakes. Results: 392 large fires burned 833 698 ha during the study period, annually burning on average 0.07%± 0.42% of forested area in each landscape. Fire activity was strongly seasonal, with most fires and area burned occurring in May and June. A combination of antecedent‐winter precipitation, fire season precipitation deficit/surplus and percent of landscape covered by well‐drained surficial deposits best explained fire occurrence and area burned. Fire occurrence varied only as a function of fire weather and climate variables, whereas area burned was also explained by percent cover of aspen and pine stands, human population density and two enduring characteristics: percent cover of large water bodies and glaciofluvial deposits. Conclusion: Understanding the relative role of these variables may help design adaptation strategies for forecasted increases in fire weather severity by allowing (1) prioritization of landscapes according to enduring characteristics and (2) management of their composition so that substantially increased fire activity would be necessary to transform landscape structure and composition.     

Early post‐fire regeneration in subalpine heathland and grassland in the Victorian Alpine National Park,south‐eastern Australia

Landscape fire (at the scale of square kilometres or more) is relatively rare in the alpine and subalpine environments of Australia. In early 1998, a major fire (the ‘Caledonia Fire’), burnt approximately 35 000 ha, of which approximately 3000 hectares was subalpine heathland, grassland and wetland within the Victorian Alpine National Park. This fire was one of only three landscape‐scale fires that have occurred anywhere in the treeless vegetation of the Victorian Alps in the past 100 years, the others being in 1939 and 1985. Monitoring of regeneration in subalpine vegetation commenced 3 weeks postfire. Sites were established in burnt grassland at Holmes Plain (1400 m a.s.l.) and burnt grassland and heathland at Wellington Plain (1480 m a.s.l.), and in unburnt grassland at both sites. In burnt grassland and heathland, the fire consumed much of the vegetation, leaving extensive areas of bare ground. The cover of dense vegetation declined from > 70% prefire, to approximately 15% immediately postfire. Bare ground at the Holmes and Wellington Plains sites ranged from 70% to 85% immediately postfire. By May 2000, approximately 2.5 years postfire, dense vegetation cover in grassland had increased to approximately 20%, and bare ground had decreased to an average of approximately 30%. In unburnt grassland, dense vegetation cover was generally > 95%, and the amount of bare ground less than 5%. The tussock‐forming snow grasses resprouted vigorously following fire, and had flowered prolifically after 1 year. In heathland, most of the shrubs were incinerated, leaving close to 100% bare soil. Since then, a number of grasses and some dominant shrubs have resprouted vigorously, with some seedling regeneration. By May 2000, in heathland, bare soil was still > 50% and dense vegetation < 20%. Such ground cover conditions during this early postfire period were well below prefire levels, and well below the levels necessary to protect alpine soils from erosion. The Caledonia Fire has provided a rare opportunity to study ecological processes associated with postfire regeneration in treeless subalpine landscapes.     

An attempt to dendrochronologically date house features at the King site (9FL5), a 16th century Late Mississippian town in northwestern Georgia,USA

The King site is a Late Mississippian (ca. 1400–1540 CE) aboriginal town located in northwestern Georgia along the Coosa River associated with the Coosa Chiefdom. The site was settled ca. 1530 but was occupied for perhaps only 50 years or so based on the lack of horizontal stratigraphy. The site was visited by members of either or both the Hernando de Soto expedition in 1540 and/or the Tristan de Luna expedition in 1560. In 1974, archaeologists discovered and removed 36 sections of subterranean charred pine posts from six house features. Our objectives were to determine if the tree rings on these posts could be dendrochronologically dated to verify the dates of site occupation and confirm the construction sequence of several houses determined originally via stratigraphic and archaeological evidence. We were able to graphically and statistically crossmatch 13 measurement series representing 10 posts from 5 of the 6 structures, yielding a 157-year floating chronology (average interseries correlation = 0.60). We were unable to absolutely crossdate this floating chronology with the only regional reference chronology long enough (back to 1378 CE) to reach the 16th century, an eastern red cedar chronology from eastern Tennessee. Archaeological evidence indicated Houses 8 and 23.4 were built later in the King site occupancy, confirmed by the tree-ring dates as both houses have the youngest tree rings of the five structures. House 14 had the oldest outermost tree rings but archaeological evidence suggests this house also was likely constructed late in the King site occupancy. We propose some posts were salvaged and reused from abandoned houses as the King site became rapidly depopulated in the last 10–20 years of site occupancy, thus explaining the age of posts used in House 14. We urge archaeologists working in the Southeastern U.S. to consider developing a more formal process for exhuming and preserving charcoalized wood remains from archaeological sites so that these samples can be evaluated using dendrochronological techniques.     

普达措国家公园四种针叶树径向生长对气候因子的响应

运用树木年代学的原理和方法,对普达措国家公园大果红杉、长苞冷杉、高山松和麦吊云杉4个优势针叶树种的年轮宽度进行测量,建立年轮宽度差值年表。分析年表与香格里拉气象站的日、月气候数据的相关性,研究4个优势针叶树种的径向生长对气候因子的响应。结果表明: 大果红杉的年生长速率最高,长苞冷杉的年生长速率最低;4种针叶树径向生长对气候因子的响应存在物种特异性,大果红杉与气候因子的相关性最强,麦吊云杉的径向生长对气候因子的响应不敏感;长苞冷杉树轮宽度年表与上年冬季(11、12月)和当年夏季(7月)的平均温度呈显著正相关;大果红杉树轮宽度年表与生长季早期(6月)温度呈显著正相关,与同期降水量和相对湿度呈显著负相关;而高山松树轮宽度年表与生长季早期(5月)的降水量和相对湿度呈显著正相关,与同期最高温度呈显著负相关,表明高山松的径向生长主要受生长季早期水分可利用性的影响。