Fire regime shifts affect bird species distributions

Aim Fire is a major driver of ecosystem structure and process, and shifts in fire regimes are implicated in the decline of many species. Shifting fire regimes have been documented around the world, and fire frequency and extent is predicted to increase in many areas because of changes in both climate and land management. Here, we evaluate how predicted increases in fire frequency are likely to impact on species distributions. Location The tropical savannas of northern Australia. Methods We developed distribution models for 44 bird species using the modelling algorithm Maxent. Our models incorporated bird locality records and environmental variables including climate, total fire frequency and the subset of fire frequency occurring late in the dry season. We investigated the effect of increasing total fire frequency and increasing fire late in the dry season, on species distributions by projecting species model algorithms onto scenarios of incrementally increased total fire frequency. Results The probability of presence for most species was higher when fire frequency late in the dry season was low. Species showed a mixed response to an overall increase in total fire frequency, with one‐third predicted to increase in distribution. However, almost all species (98%) showed a decrease in predicted range with increased late‐dry season fire, and species distribution area was generally negatively correlated with an increase in late‐dry season fire. Main conclusions Our study highlighted the array of responses of species to increasing fire frequency and suggested that increased fire frequency late in the dry season is detrimental to most savanna‐restricted bird species. The understanding of individual species’ preferences for particular fire frequencies is important for informed conservation planning.     

Spatial and temporal variations in the composition and density of crustacean plankton in the five basins of Lake Kariba, Zambia-Zimbabwe

Lake Kariba is a man-made reservoir which is now over 30 yearsold. The reservoir was built on the Zambezi river on the borderbetween Zambia and Zimbabwe. The crustacean zooplankton of thisman-made lake were studied over 3 years from March 1986 to February1988. This period included three seasons — (i) warm, rainyseason, (ii) cool, dry season and (iii) warm, dry season —which have a major influence on the limnology of the lake. Crustaceanplankton species composition and abundance varied among thefive basins. The most upstream basin had the highest numberof species and highest densities at all the sampling times overthe period of this study. There was both spatial and temporalheterogeneity in species composition and abundance along thelong axis of the lake. ¹Present address: Department of Biological Science, Universityof Botswana, P. Bag 0022, Gaborone, Botswana     

Temporal changes in the fish fauna entering a tidal swamp system in tropical Australia

Synopsis Leanyer Swamp, a tidal swamp in tropical Australia, is a nursery area for a number of fish species of marine origin. Juveniles of 38 species, representing 24 families, were trapped between October 1979 and March 1980 as they entered the swamp on flood spring tides. The composition of the fish fauna varied markedly between the late dry, early wet and late wet seasons. Of the 17 species whose numbers were significantly correlated to environmental parameters, 15 were correlated wholly or in part with season. The season, the sequence of flood spring tides and the height of these tides determined the movement of the fish community as a whole. The seasonal abundance of many fish species was determined more by their breeding patterns and the dispersal abilities of their juveniles than by such environmental parameters as temperature and salinity which, despite their seasonal change, varied over the short-term with the interaction of tides and rainfall.     

Effect of fire regime on plant abundance in a tropical eucalypt savanna of north‐eastern Australia

Abstract Changes in plant abundance within a eucalypt savanna of north‐eastern Australia were studied using a manipulative fire experiment. Three fire regimes were compared between 1997 and 2001: (i) control, savanna burnt in the mid‐dry season (July) 1997 only; (ii) early burnt, savanna burnt in the mid‐dry season 1997 and early dry season (May) 1999; and (iii) late burnt, savanna burnt in the mid‐dry season 1997 and late dry season (October) 1999. Five annual surveys of permanent plots detected stability in the abundance of most species, irrespective of fire regime. However, a significant increase in the abundance of several subshrubs, ephemeral and twining perennial forbs, and grasses occurred in the first year after fire, particularly after late dry season fires. The abundance of these species declined toward prefire levels in the second year after fire. The dominant grass Heteropogon triticeus significantly declined in abundance with fire intervals of 4 years. The density of trees (>2 m tall) significantly increased in the absence of fire for 4 years, because of the growth of saplings; and the basal area of the dominant tree Corymbia clarksoniana significantly increased over the 5‐year study, irrespective of fire regime. Conservation management of these savannas will need to balance the role of regular fires in maintaining the diversity of herbaceous species with the requirement of fire intervals of at least 4‐years for allowing the growth of saplings >2 m in height. Whereas late dry season fires may cause some tree mortality, the use of occasional late fires may help maintain sustainable populations of many grasses and forbs.     

Dynamic spatial partitioning and coexistence among tall grass grazers in an African savanna

Competitive relationships among mobile animals may be expressed through dynamically changing spatial relationships over different time frames. Less common species that are apparently inferior competitors may be able to coexist with more abundant species by concentrating in regions of the landscape little utilized by the former at spatio‐temporal scales from annual or seasonal ranges to the specific foraging localities exploited at different stages of the annual cycle. Spatial relationships may be influenced further by dependencies on other resources, predation risks and facilitatory interactions under certain conditions. Our study aimed to determine whether competition with more abundant zebra and buffalo restricted the abundance of sable antelope in a region where these three tall‐grass grazers overlapped in their herd distributions. We tracked the simultaneous movements of animals representing herds of these species over two dry seasons and one wet season using GPS‐GSM collars, and estimated seasonal or monthly range extents and their overlap. We also compared daily separation distances between these animals against the null pattern expected if their movements had been independent, and assessed how prior grazing by buffalo influenced the subsequent use of these localities by sable. The range of the sable herd was mostly separated from the seasonal range of the buffalo herd during the late dry season of 2006 and throughout the dry season of 2007. Seasonal home ranges of zebra herds overlapped partially with the range of the sable herd during most of the year. Even during times when their ranges overlapped, sable were rarely recorded within <1 km of the buffalo herd. Prior grazing by buffalo beyond a threshold level inhibited later use of these localities by sable, but the sable were nevertheless able to exploit places that were little utilized by buffalo at that time. Sable were less able to evade overlap with the small, mobile zebra herds, and hence more vulnerable to competitive exclusion by zebra than by buffalo. Our findings demonstrate how less abundant species can restrict competition from more abundant competitors through dynamic spatial partitioning in regions where their home ranges overlap.     

云南元江干热河谷木本植物的物候

在中国西南干热河谷的典型地段——元江干热河谷,连续3年观测了32种木本植物的枝条生长、叶片动态、花期、果期和果实类型。这些植物的枝条生长方式可以分为连续生长、枝条枯死、陡长和间歇生长4个类型。其中连续生长型占优势,包括13种植物,它们的枝条在雨季连续不断伸长。9种植物雨季的枝条伸长与连续生长型的相似,但它们顶部的枝条在旱季末期出现枯死现象。6种植物属于陡长型,在2周内完成抽枝,且一年只抽一次枝。4种植物属于间歇生长型,枝条在雨季来临后伸长一段时间,然后生长停滞,过一段时间后再接着伸长。从叶片物候类型看,元江干热河谷植被以落叶植物占优势。落叶植物中冷凉旱季（11月～2月）落叶植物占优势（19种）,而干热旱季（3—4月）落叶植物很少（4种）。除红花柴（Indigofera pulchella）和狭叶山黄麻（Trema angustifolia）从雨季中期开始脱落叶片外,其它30种植物从雨季末期开始脱落叶片,落叶期至少延续3个月以上。常绿植物脱落近1／3～1／2的当年生叶片。共有6种植物能在旱季末期长出新叶。常绿植物的叶面积、单个枝条上的总叶面积和枝条承载（总叶面积／枝条长度）比落叶植物小。虽然一年四季都有不同植物开花和结果,但多数植物（29种,占观测树种的91％）的花期集中在旱季和雨季初期,而果实（种子）成熟期从雨季末期延续到旱季末期和下个雨季初期。果实多为核果。     

Diet of Montagu's Harrier Circus pygargus in central Spain: analysis of temporal and geographic variation

The diet of Montagu's Harrier Circus pygargus was studied for 4 years near Madrid, Spain, with the use of pellets and prey remains collected during the breeding season. The diet of the study birds included a wide variety of prey categories, the most important one by weight being lagomorphs (mainly Hares Lepus granatensis ). The diet varied seasonally, with Hares predominating early in the breeding season, while birds increased in importance later. The shift was partly a result of variation in availability (with fledgling birds being more abundant late in the season), but statistical analysis suggested that lagomorphs and then birds were actively chosen in the prelaying and nestling periods, respectively. Montagu's Harrier seemed to be an opportunistic species, hunting a wider range of prey types in more southern latitudes, but specialized in each region in the prey species that was most profitable. This was the only study on Montagu's Harriers to date which found lagomorphs to be the most important part of the diet throughout the season.     

Germinable soil seed banks in a tropical savanna: seasonal dynamics and effects of fire.

Abstract The germinable soil seed bank of a tropical eucalypt savanna of north‐eastern Australia was found to be dominated by grasses and forbs, with seed bank density ranging from 58 to 792 seeds per square metre, from a total of 53 species. Late dry season fires and the fire‐related cues, heat shock and smoke, broke the seed dormancy of a range of tropical savanna species. Heat shock promoted the germination of the species groups natives, exotics, subshrubs, ephemeral and twining perennial forbs, and the common species Indigofera hirsuta, Pycnospora lutescens and Triumfetta rhomboidea. Exposure to smoke at ambient temperature promoted germination from the soil seed bank of the species groups combined natives, upright perennial forbs and grasses, as well as the common grasses Digitaria breviglumis and Heteropogon triticeus. The germinable soil seed bank varied seasonally, increasing from the mid wet season (February) and early dry season (May) to a maximum in the late dry season (October). The effect of recent fire history on soil seed bank dynamics was limited to the immediate release of some seed from dormancy; a reduction in seed densities of subshrubs and monocots, other than grasses, in recently burnt savanna; and enhanced seed density of the ephemeral I. hirsuta in the year following fire. The seed banks of most savanna species were replenished in the year following burning.     

Yellow‐chevroned Parakeet (Brotogeris chiriri) abundance and canopy foraging at a dry forest in western Brazil

I studied Brotogeris chiriri abundance and foraging activity at a dry forest of the Urucum mountains in western Mato Grosso do Sul, Brazil, to evaluate their relationships with food resource production. Brotogeris chiriri abundance sharply increased during the early wet season (mainly October 2001) when it mostly foraged for fleshy fruits. At that time Protium heptaphyllum, one of the most common tree species, bore a large crop of fruits, the arils of which were extensively consumed by B. chiriri. Conversely, only a few parakeets were recorded foraging from the late wet to the late dry season, when dry fruit production predominated. The monthly pattern of parakeet abundance paralleled both its monthly pattern of foraging activity and fleshy fruit availability. Moreover, the variations in foraging activity were highly correlated to fleshy fruit production. Thus, data presented here evidenced the effect of both fruiting pulses and a common tree species that produced a large and ephemeral fruit crop, on the dynamic of a small and mobile canopy forager at a primary dry forest.     

Canopy phenology of a dry forest in western Brazil.

Dry forests are common, although highly threatened in the Neotropics. Their ecological processes are mostly influenced by rainfall pattern, hence their cycles exhibit contrasting phases. We studied the phenology of canopy trees in a primary dry forest in Western Brazil in the foothills of the Urucum mountain chain, in order to improve our knowledge on the functioning of these poorly-known forests. Leaf shedding started in the early dry season and was massive in the latter part of this period. Most leaf loss occurred in dry hills, while wet valleys remained evergreen. Anemochorich and autochorich species predominated in dry hills, presumably due to their tolerance to dry conditions and enhanced exposition to winds, which favour diaspores removal and dispersal. Conversely, zoochorich species dominated the wet valleys. Flowering was intense in the late dry season, the driest period of the year, while fruiting was massive just after the onset of rains, as well as flushing. Therefore, most flowering was unrelated to wet conditions, although such an abiotic factor, potentially, triggered the major fruiting episode, widely comprised by zoochorich species. Anemochorich and autochorich species flowered and fruited in the course of the long dry season. The contrasting environmental conditions present in the hills and valleys determine the arrangement of a mosaic in which patches of zoochorich and evergreen trees alternate with patches of non zoochorich and highly deciduous species. Consequently, species with such syndromes exhibited marked flowering and fruiting patterns, accordingly to the pronounced seasonality.     

Ranging behavior of the François’ langur (<Emphasis Type="Italic">Trachypithecus francoisi</Emphasis>) in the Fusui Nature Reserve,China

Data on activity budgets and ranging patterns were collected from March to December 2001 for one group of François’ langurs (Trachypithecus francoisi) inhabiting a forested part of the Fusui Nature Reserve, Guangxi province, China. Our results indicate that the total size of the home range of the study group during the study period was 19 ha. The majority of their activities (52%) occurred within a small area, 22%, of their home range, and was concentrated in or near quadrats containing their sleeping sites, which may reduce the time and energetic cost of travel. The extent of the ranging behavior varied between months, with the smallest, 7 ha, recorded in July and the largest, 13.5 ha, in November. There was no significant difference between seasons. The monthly mean daily path lengths varied from 341 to 577 m. The daily path lengths showed significant seasonal changes: the path lengths were longer during the dry season than in the rainy season, which may be related to the scarcity of preferred food resources during the dry season.     

Seasonal variability of ichthyoneuston assemblage on the continental shelf and slope of the Southwest Atlantic Ocean,Brazil (20°–23°S)

Many marine organisms spend the early life history stages in neuston domain. Although the importance of ichthyoneuston, few studies were developed in the Southwest Atlantic Ocean. Therefore, this study aimed to improve the knowledge on ichthyoneuston of the Brazilian coast analyzing the vertical stratification and horizontal distribution of these organisms. Neuston samples were collected in daylight between 20°S and 23°S from February to April 2009 (late summer/early autumn; rainy season) and from August to September 2009 (late winter/early spring; dry season). Eggs of six taxa were identified: Anguilliformes, Engraulidae, Clupeidae, Synodontidae, Trichiuridae, and Maurolicus stehmanni (Sternoptychidae). The neustonic larval fish assemblage was composed by 40 families and 63 species. Mullidae and Myctophidae larvae were the most abundant in the rainy period while Mullidae and Mugilidae dominated in the dry season. Seasonal and spatial variation of larval fish assemblages in the neuston were structured by oceanographic features. The larval fish abundance on the outer slope stations may have been favored by the advection of an anticyclone that encompassed most of the study region during the cruise periods. In the rainy season, salinity and local depth structured the larval fish assemblage in a cross‐shelf gradient, while in the dry season the larval assemblage was structured around temperature and north‐south gradient. In the dry season, the cross‐shelf gradient was less pronounced mainly because of the low abundance and frequency of mesopelagic larvae. The low frequency and abundance of some species are probably related to the net avoidance of fish larvae during the day or dial vertical migration, as many species migrate to deeper layers during the day and ascend to neuston only at night. Nevertheless, the present study presented baseline information about the seasonal and spatial variation of the neustonic larval fish assemblage influenced by the oceanographic conditions in the Campos Basin. We recommend to additionally collect night samples to decrease larval escapement rates and to compare night versus day catches to further investigate the influence of daily migration in the neustonic larval fish in the area.     

An assessment of the fish population of the lower reaches of the Sanyati River,Zimbabwe

The fish population of the lower reaches of the Sanyati River was studied using multifilament gillnets and monthly sampling was conducted over 13 consecutive months. A total of 15 fish species belonging to seven families were collected and variations in monthly catches and catch per unit effort and condition were observed. The five most common species exhibited a seasonal breeding pattern, with most breeding occurring in the rainy season. The exotic Nile tilapia Oreochromis niloticus was found to have established itself in the Sanyati River. The results of this study were compared with those of previous workers on Lake Kariba.     

Spatial variation in density and total size estimates in fragmented primate populations: the golden‐crowned sifaka (Propithecus tattersalli)

The golden‐crowned sifaka (Propithecus tattersalli) is an endangered lemur species found only in the Daraina region, a very restricted area in north‐eastern Madagascar. Its forest habitat is highly fragmented and expected to suffer from significant changes in the near future. The species is poorly known and only one census study, carried out in 2000, has ever been published. It is thus crucial to update the conservation status of the golden‐crowned sifaka before major anthropogenic environmental changes take place. Using the line‐transect approach, we estimated the species density in the main forest fragments located in both the peripheral and central parts of the distribution range, including both protected and unprotected areas. In parallel, we tried to determine whether an edge effect could be detected by comparing densities at different distances from the forest edges. We found important variation of sifaka densities among forest fragments. The total species abundance is thus difficult to determine, but we estimated that it is likely to be over 18,000, two to three times higher than previously thought. However, our data also suggested that most P. tattersalli live in forests located in the central part of the distribution range and that the estimated densities in the central part were high (>80 individuals/km²). Two forest fragments, found to host a large part of the total population, are currently outside the managed area and their incorporation to the managed area is strongly recommended. Lastly, as expected for a folivorous and not heavily hunted species, our results are consistent with the hypothesis that this species does not experience a clear edge effect, at least during the first half of the dry season. This could be due to a high resiliency to habitat fragmentation or to the fact that fragmentation has been going on for some time. Am. J. Primatol. 72:72–80, 2010. © 2009 Wiley‐Liss, Inc.     

Herbaceous production in South India—limiting factors and implications for large herbivores

This study’s goal was to better understand the growth pattern and limitations of the herbaceous production that supports South India’s rich large herbivore grazer assemblage. We conducted a fully factorial nitrogen and water (three levels each) treatment field experiment in the herbivore rich South Indian Western Ghats region to determine the seasonal pattern and the extent to which nitrogen and water availability limit herbaceous production. Graminoid production was found to be nitrogen limited. Despite low rainfall, additional water did not significantly increase overall biomass production nor extend growth in the dry season. Accumulated standing biomass was highest in the late wet season (November) and lowest in the dry season (May). Leaf nitrogen was highest in the early wet season (June) and lowest in the late dry season (March). Grazing had a positive effect on grass production by extending the growing season. Biomass production and graminoid leaf nitrogen concentration levels in the study area were similar to other tropical areas in the world. Also similar to other tropical large herbivore areas, the dry season poses an annual challenge for large herbivores in the study area —particularly the smaller bodied species—to satisfy their nutrient requirements.     

Variability of fish diets between dry and flood periods in an arid zone floodplain river

The fish assemblages of an arid zone floodplain river, Cooper Creek, Queensland, Australia, were sampled during two dry periods in isolated waterholes and on the inundated floodplain during the early and late phase of a major flood event. Diets were described for nine native species and compared within and between dry and flood periods. In the dry season, when fishes were restricted to waterholes, diets were characteristically simple with narrow diet breadths. Movement onto the floodplain during flooding clearly increased feeding opportunities, with greater diet breadths evident in all species. Despite obvious potential for terrestrial inputs, diets tended to be dominated by aquatic resources in both the waterholes and on the floodplain. Stomach fullness, however, varied little between dry season waterhole and floodplain samples. Fishes appeared to feed on potentially lower value resources such as detritus and calanoid copepods during the dry season, when waterholes were isolated and food resources were limited. They were then able to capitalize on the 'boom' of aquatic production and more diverse food resources associated with episodic flood events.     

Regeneration of monsoon rain forest in northern Australia: the sapling bank

Abstract. As part of a wider study examining regeneration pathways in monsoon rain forest vegetation in northern Australia, a one-off, dry season census of saplings was undertaken along transects sampled at each of 33 relatively undisturbed sites broadly representative of the range of regional monsoon rain forest vegetation. Four floristic quadrat groups were derived through TWINSPAN classification. Subsequent analyses involved: (1) comparison of mean dry season stockings of juveniles occurring in different rain forest types, and their structural and environmental correlates; (2) comparison of the contributions of different life forms, and the influence of clonal reproduction in the sapling regeneration banks of different forest types; and (3) exploration of relationships between the distributions of saplings of common tree species with respect to seed bank, floristic, structural, and environmental variables. While data presented here require cautious interpretation given that processes of seedling/sapling recruitment and mortality are highly dynamic, sapling banks were found to be most dense on coarse-textured, moist soils, and least dense on coarse-textured, seasonally dry soils. Canopy cover and fire impact were shown to be highly influential on sapling distribution, especially for saplings of tree species and those growing on seasonally dry sites. Sapling densities were little influenced by proximity to rain forest margins, except for shrubs. The potential for clonal reproduction was significantly greater on dry sites, especially for trees. The majority of saplings sampled were derived from relatively few common, non-clonal, canopy tree species. Sapling distributions of 20 out of 23 common tree species were clumped in the vicinity of conspecific adults; for most species the strength of this relationship was greater than that for any other variable. These data support observations in the literature concerning the distribution of sapling banks in moist and dry tropical forests.     

Reproductive Phenology of Woody Species in a North Australian Tropical Savanna1

Interspecific and interannual variation in reproductive phenology was quantified for 50 common species of trees and shrubs from a mesic savanna near Darwin, northern Australia. The presence of buds, flowers, and fruit was noted over a 30-month period, from September 1992 to February 1995. Surveys were undertaken at monthly intervals for the less common species, and at bimonthly intervals for ten of the common trees and tall shrubs. The majority of species flowered each year at about the same time. There was no evidence of sub-annual or continuous regimes of reproductive phenology. There was no supra-annual carryover of seed-bearing fruit in the canopy of any species. The peak flowering periods were the mid to late dry season (July–August) and the transition between the dry season and the wet season (October–November). The two dominant trees–Eucalyptus miniata and E, tetrodonta– flowered during the dry season, thereby providing resources for some elements of the vertebrate fauna. Flowering and fruiting were uncommon at the end of the wet season (February/March), although two species that flower and fruit at this time (E. porrecta and Terminalia ferdinandianas may provide resources to consumers at a time when floral or fruit resources are otherwise scarce. Because the peak of reproductive activity takes place during the late dry season, fruit maturity and seed dispersal have occurred prior to the onset of the rainy season for most species, and germination and seedling establishment potentially may take effect in response to the first rains. Late dry season fires, which tend to be extensive and intense, are a potential threat to the floral and fruit reserves within these savannas.     

Temporal Dynamics of Rich Moth Ensembles in the Montane Forest Zone in Southern Ecuador1

We studied temporal dynamics of diverse moth ensembles (Arctiidae and Geometridae) in early and late succession stages of forest recovery in the montane zone of southern Ecuador. Moths were sampled using weak light sources (2 × 15 W tubes per trap) during three sampling periods (March–April 2002, wet season; October–November 2002, and August–October 2003, both “dry” seasons). Arctiid moth abundance hardly varied between sampling periods. Estimates of local diversity were lower in 2002 (wet and dry season) than in the dry season 2003, and ensemble composition was more strongly affected by sampling period rather than habitat differences. Geometridae ensembles revealed stronger temporal patterns. Geometrid abundance increased about twofold from the wet to the dry season, and temporal effects on species composition were far more pronounced that in arctiids. These differences might hint to variation in the dependence of geometrid versus arctiid larvae on ephemeral plant resources. Despite these significant temporal dynamics, in both families only a few of the more common species analyzed individually showed strong temporal changes in abundance. Almost all common species occurred as adults during all sampling periods. Therefore, even though temporal dynamics of moth ensembles are not negligible, both moth families are suitable “indicators” of community diversity and change along the succession gradient. Samples must be large enough, however, and preferably should be collated over various times of the year and in parallel, to allow for valid statements about moth diversity and species compositions in relation to habitat differences. These recommendations undermine the validity of the concept of “rapid biodiversity inventories” for speciose tropical insect communities.     

Possible causes of decreasing migratory ungulate populations in an East African savannah after restrictions in their seasonal movements

In many areas in Africa, seasonal movements of migratory ungulates are restricted and their population numbers decline, for example in the Tarangire region, Tanzania. Here, agriculture restricts migration of ungulates to their wet season ranges. We investigated whether low forage quality or supply are possible causes of population decline of wildebeest and zebra when access to these wet season ranges is restricted and migratory herds have to reside in the dry season range year-round. We simulated grazing through a clipping experiment in the dry season range during the wet season. Clipping negatively affected forage supply and had a positive effect on forage quality by increasing proportions of live and leaf biomass as well as nutrient concentrations in the leaves. However, increase in forage quality in the dry season range due to grazing was not as such that requirements of wildebeest during the wet season, when females are lactating, could be met. We conclude that low forage quality in the dry season range during the wet season could cause the decrease in migratory ungulate populations in the Tarangire region. With this study, the necessity of protecting wet season ranges from expanding human activities to safeguard migratory systems is supported.