Fire history of an isolated subalpine mountain range of the Intermountain Region,United States

Fire has historically been an important ecological component of forests in the Intermountain Region of the northwestern United States. This study is set in a small biogeographically disjunct mountain range. Our research objectives were to (1) investigate the historical frequency, severity, size, and spatial pattern of fire; (2) determine if and how fire regimes have changed since Euro-American settlement; and (3) compare how fire regimes of a small isolated range compare to nearby, but considerably larger, mountain agglomerations. Our findings suggest that this mountain range has historically supported fires typified by small size and high frequency, resulting in a high degree of spatial pattern complexity compared to mountain agglomerations. We also found disparity in size and burn severity solely within the study area based on the bisecting Continental Divide. Since the advent of Euro-American settlement in the 1870s, fire frequency and sizes of individual fires in the West Big Hole Range have significantly decreased resulting in an estimated 87% reduction in area burned. We discuss potential relationships of mountain range isolation and fire regimes in the Intermountain Region. Furthermore, we suggest that the relative small size of this mountain range predisposes it to greater anthropogenic effects upon fire occurrence.     

Influence of rainfall on sleeping site choice by a group of anubis baboons (Papio anubis)

For diurnal nonhuman primates, shifting among different sleeping sites may provide multiple benefits such as better protection from predators, reduced risk of parasitic infection, and closer proximity to spatially and temporally heterogeneous food and water. This last benefit may be particularly important in sleeping site selection by primates living in savanna‐woodlands where rainfall is more limited and more seasonally pronounced than in rainforests. Here, we examined the influence of rainfall, a factor that affects food and water availability, on the use of sleeping sites by anubis baboons (Papio anubis) over two 13‐month study periods that differed in rainfall patterns. We predicted that during wet periods, when food and water availability should be higher, the study group would limit the number of sleeping sites and would stay at each one for more consecutive nights than during dry periods. Conversely, we predicted that during dry periods the group would increase the number of sleeping sites and stay at each one for fewer consecutive nights as they searched more widely for food and water. We also predicted that the group would more often choose sleeping sites closer to the center of the area used during daytime (between 07:00 and 19:00) during wet months than during dry months. Using Global Positioning System data from collared individuals, we found that our first prediction was not supported on either monthly or yearly timescales, although past monthly rainfall predicted the use of the main sleeping site in the second study period. Our second prediction was supported only on a yearly timescale. This study suggests that baboons’ choice of sleeping sites is fluid over time while being sensitive to local environmental conditions, one of which may be rainfall.     

Factors influencing seasonal and monthly changes in the group size of chital or axis deer in southern India

Chital or axis deer (Axis axis) form fluid groups that change in size temporally and in relation to habitat. Predictions of hypotheses relating animal density, rainfall, habitat structure, and breeding seasonality, to changes in chital group size were assessed simultaneously using multiple regression models of monthly data collected over a 2 yr period in Guindy National Park, in southern India. Over 2,700 detections of chital groups were made during four seasons in three habitats (forest, scrubland and grassland). In scrubland and grassland, chital group size was positively related to animal density, which increased with rainfall. This suggests that in these habitats, chital density increases in relation to food availability, and group sizes increase due to higher encounter rate and fusion of groups. The density of chital in forest was inversely related to rainfall, but positively to the number of fruiting tree species and availability of fallen litter, their forage in this habitat. There was little change in mean group size in the forest, although chital density more than doubled during the dry season and summer. Dispersion of food items or the closed nature of the forest may preclude formation of larger groups. At low densities, group sizes in all three habitats were similar. Group sizes increased with chital density in scrubland and grassland, but more rapidly in the latter—leading to a positive relationship between openness and mean group size at higher densities. It is not clear, however, that this relationship is solely because of the influence of habitat structure. The rutting index (monthly percentage of adult males in hard antler) was positively related to mean group size in forest and scrubland, probably reflecting the increase in group size due to solitary males joining with females during the rut. The fission-fusion system of group formation in chital is thus interactively influenced by several factors. Aspects that need further study, such as interannual variability, are highlighted.     

Climatic influences on the behavioural ecology of Chanter's mountain reedbuck in Kenya

The effects of rainfall and temperature on the behavioural ecology of Chanler's mountain reedbuck (Redunca fulvorufula fulvorufula Rothschild) were examined on ranchland near Gilgil, Kenya. Ambient temperature was shown to be the proximate determinant of diurnal activity and rumination patterns. Mountain reedbuck were active during early morning and late afternoon, but rested and abandoned rumination when temperatures peaked at midday. There was close synchrony in levels of activity, rumination and use of cover and shade between males and females. Seasonal variations in time budgets were strongly influenced by rainfall patterns. Analyses revealed a one-month lag between rainfall and both peak grass growth and a decrease in rumination frequency. The proportion of time allocated to feeding decreased one month later, and was coincident with an increase in the proportion of grass in the diet. Reedbuck may therefore be prevented from exploiting high-quality new grass, possibly by gut-fill or induced imbalances in rumen pH. It is suggested that the unexpectedly high levels of browse in the diet is an adaptive response to low rainfall during the preceding two months.     

The effect of rainfall on tick challenge at Kyle Recreational Park,Zimbabwe

The effect of rainfall pattern on tick challenge was investigated at Kyle Recreational Park, Zimbabwe, from 1991 to 1992 using drag and removal plot methods to sample environmental tick density. The abundance of adults and nymphs of the brown ear-tick Rhipicephalus appendiculatus and larvae of the bont tick Amblyomma hebraeum was positively correlated with monthly rainfall, whereas no relationship with rainfall was revealed for larval R. appendiculatus, adults of the red-legged tick R. evertsi, or larvae of the blue tick Boophilus decoloratus. A comparison between 1991 (490 mm rainfall) and the drought year of 1992 (161 mm) revealed significant differences in the abundance of R. appendiculatus, A. hebraeum, and B. decoloratus. During the wet season, R. appendiculatus adults were 2–3 time more numerous in the environment during the higher rainfall year of 1991. A. hebraeum larval abundance exhibited a similar pattern to that of R. appendiculatus adults, but B. decoloratus larvae were more abundant in the drought year of 1992 during both the wet and dry seasons. Comparable tick abundance data collected at Kyle during the above-average rainfall years of 1975–1977 (mean = 1029 mm) were compared with tick challenge during the below-average rainfall years of 1991–1992 (mean = 326 mm). In grassland sand habitat and all habitats combined R. appendiculatus adults, nymphs, and larvae were much more abundant during the high rainfall years. In contrast, larvae of B. decoloratus were more numerous during the drier years. A. hebraeum larvae were also more abundant during the drier years. The strong positive correlation of adult R. appendiculatus abundance with rainfall and the coincidence of increased adult tick challenge with increased rainfall indicates that adult R. appendiculatus tick burden on hosts would be heaviest during the wet season and high rainfall years.     

The rapid and long-lasting growth of grasses following small falls of rain on stony downs in the arid interior of Australia

Abstract Stony downs consist of grassy areas that alternate with areas that have a substantial stone cover. The stone-covered areas are impermeable, and most rain falling on them runs off, substantially increasing the effective rainfall in adjacent grassy areas. As a result, 20–25 mm of rain on stony downs wetted the soil around the grass to a depth of 140–170 mm and allowed sustained grass response. This is much less than the 35–40 mm of rain required for the same response on red clay or grey clay plains. Grasses respond very rapidly after rain. Some have green shoots the day after rain, and all have responded by the second day. Ephemerals dry off in 4–6 weeks, but most tussock grasses still have some green foliage 8–10 weeks after rain. Deeper rooted tussock grasses remain green for so long because most of the moisture that reaches deeper roots after rain remains there. Most moisture loss is through the soil surface and is recognizable as a drying front that descends through the soil profile. Soil above the drying front is nearly air dry (<5% moisture) while soil below the front has substantial moisture (14–16%). By about a month after rain in summer, the drying front is at a depth of about 80–120 mm. This is near the tips of the roots of ephemeral grasses and the ephemerals then dry off rapidly. Only the tips of the leaves of deep rooted grasses like Mitchell grass (Astrebla spp.) dry off. Their leaves continue to remain mostly green during most of the second month after rain and they do not dry off completely until the third month when the drying front reaches the bottom of the main root system.     

晋西黄土区土地利用对降雨入渗产流模式和优先流分布的影响试验研究

黄土高原退耕还林(草)工程显著改变了河川径流过程,但其作用机制尚不明晰。选取晋西黄土区4种典型下垫面(20年和30年刺槐人工林地、草地、休耕地)分别开展连续3场模拟降雨试验,观测坡面入渗产流过程,并结合染色示踪和图像处理软件技术,分析土地利用类型对坡面降雨入渗产流模式和优先流分布的影响。结果表明：(1)累积入渗量和优先流发育程度均表现为刺槐林地>草地>休耕地,刺槐林地优先流对总入渗的贡献是草地和休耕地的2.5—4.5倍,但优先流贡献均不超过10%,仍以基质流入渗为主。(2)4种用地类型降雨入渗主要补给地表60—70cm土层,前期降雨均匀增加表层土壤含水率,而后期降雨补给深层土壤水分的空间变异性显著增强。(3)刺槐林地产流量及径流系数均显著小于草地和休耕地,且前期含水量对20年刺槐林地的影响较小,而显著影响草地和休耕地径流系数。(4)直径d<1mm的细根显著促进降雨入渗和优先流发育,而d>5mm的粗根与入渗量和基质流量呈显著负相关。较高的土壤初始含水率、容重和粘粒含量会抑制入渗和优先流的发生。研究说明不同土地利用类型将改变降雨入渗产流过程及土壤水运动形式。     

Restoration management of abandoned chalk grassland in the Netherlands

After abandonment of chalk grassland in the Netherlands, Brachypodium pinnatum had become very dominant and this resulted in a dramatic decrease of plant diversity. Restoration of these abandoned sites is important, because of its former high diversity with many nationally endangered species. To restore the chalk grassland vegetation, the impact of the introduction of different experimental cutting regimes was investigated during three years. The thick litter layer and the dominance of Brachypodium was strongly reduced after introduction of all cutting regimes. In all cutting treatments forb phytomass increased considerably, especially in the twice-a-year cutting vegetation, where the forb phytomass became as high as that of Brachypodium. Phanerogamic species diversity was stimulated in all cutting regimes. Especially the number of short-lived forbs. with a persistent seed bank, increased markedly in the twice-a-year cutting treatment. It is concluded that cutting the vegetation twice is adequate to reduce the negative effects of the thick litter layer and the abundant growth of Brachypodium. It creates an appropriate starting point for more detinite management, whether mowing or grazing. However, the restoration of a more complete species assortment strongly depends on the re-invasion possibilities of these species.     

Sieving experiment: the controlled recovery of charred plant remains from modern and archaeological samples

Results of experimental retrieval of plant remains (both charred modern and fossil) from three sediment types (clay, gravel and sandy loam) carried out by environmental archaeologists from the Ancient Monuments Laboratory and the Central Archaeology Service, English Heritage, are reported. For each sediment type, six different treatments were carried out using three flotation machines of the Siraf type, two other machines in use in two archaeological units and one experimental machine. The results show that there is invariably considerable discrepancy between the amount of plant material present and that recovered, that the Serif-type machine is among the best currently available and that pretreatment of particular mineral soils may improve recovery of plant macrofossil material.     

Variability of nutrient limitation in the Archipelago Sea,SW Finland

Over a two year study period, zooplankton was sampledin Gazi Bay, Kenya, using a 335 μm mesh size Bongonet. Two Way Indicator Species Analysis (TWINSPAN)classification technique demonstrated that rainfalland tidal regime had substantial influence on thezooplankton community structure. Samples collectedduring the rainy season months clustered together whentreated with TWINSPAN. Furthermore, theclustering was more pronounced for neap tidesamples than for spring tide ones. Samples obtainedduring spring tide did not give a clear cut pattern. Canonical Correspondence Analysis (C.C.A.) confirmedthese findings, a clustering together of rainy/neaptide samples; and little separation (based onenvironmental variables) between samplingstations. This revised version was published online in August 2006 with corrections to the Cover Date.