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Little attention has been paid to how four dominant shrub species distributed in semi-arid areas respond to the combined effects of temperature and water supply. Seedlings of four species were grown in a glasshouse for eight weeks at air temperatures of 12.5/22.5, 15/25, 17.5/27.5, and 20/30degC (night/day) and with water supplies of 37.5, 75, 112.5, and 150 mm per month. When temperatures were 17.5/27.5 and 20/30degC relative growth rate (RGR) decreased for Artemisia ordosica, A. sphaerocephala, and Hedysarum laeve but not for Caragana korshinskii. RGR increased with increasing water availability for all four species and most treatments. In response to changing water availability, the RGR tended to correlate mainly with the physiological trait (net assimilation rate, NAR) and with dry matter allocation traits (below-ground to above-ground dry matter and leaf mass ratio). A higher ratio of below to above-ground dry matter for all four species under most treatments (0.3-1.7) and water-use efficiency (1.4-9.2 g/kg) may explain how all four species survive drought. Higher temperatures may be harmful to A. ordosica and A. sphaerocephala, under current precipitation levels (average 75 mm per month from mid-June to mid-August). These findings support the proposal that A. ordosica mixed with C. korshinskii will prove optimal for re-vegetation of degraded areas of the Ordos plateau.

Non-native annual grasses dominate most Californian mediterranean-climate grasslands today. However, native Californian grassland flora persists in grasslands on serpentine-derived soils. We manipulated soil nutrient resources to explore the links between nutrient availability, plant productivity, and the relative abundances of native and non-native species in serpentine grassland. Factorial combinations of nitrogen, phosphorus, and other components of a nutritionally complete formula were added to field plots over two growing seasons. Fertilization with nitrogen and phosphorus increased biomass of the resident vegetation substantially in the first season, and within two years allowed the invasion and dominance of non-native annual grasses in patches originally dominated by native annual forbs. Species richness declined with fertilization, as the increased biomass production by invaders suppressed some native forbs. Increased macronutrient availability can increase production on serpentine-derived soil, even when other serpentine characteristics (such as low Ca/Mg ratios and high heavy-metal concentrations) have not been mitigated. Observed changes in community structure and composition demonstrate that the invasibility of plant communities may be directly influenced by nutrient availability, independent of physical disturbance.

In the state of Para, Brazil, in the eastern Amazon, we studied the potential for sustained fire events within four dominant vegetation cover types (undisturbed rain forest, selectivity logged forest, second-growth forest, and open pasture), by measuring fuel availability, microclimate, and rates of fuel moisture loss. We also estimated the potential tree mortality that might result from a wide-scale Amazon forest fire by measuring the thermal properties of bark for all trees in a 5-ha stand of mature forest, followed by measurements of heat flux through bark during simulated fires. Partial logging resulted in dramatic increases in downed woody debris. Total fuel mass was significantly greater in the logged forest (180 Mg/ha) compared to the other cover types (30-60 Mg/ha). However, the readily combustible fine-fuels (e.g., grasses, litter, herbs) were significantly greater in pastures (@? 11 Mg/ha) than in all other cover types (@? 6 Mg/ha). Anthropogenic disturbance altered microclimate, which in turn affected rates of fuel moisture loss and the dynamic equilibrium of fuel moisture contents. In pastures of average midday temperature was almost 10^oC greater, and the average midday relative humidity was 30% lower, than in primary forest. There was a sixfold difference in average vapor pressure deficit between the primary-forest and the open-pasture cover types. Given the relatively steep gradient between the vapor pressure of the fuel particles and the surrounding atmosphere in the disturbed communities, fuel moisture loss was more rapid and equilibrium moisture contents were lower than in primary forest. Based on the changes in fuels and microclimate, we determined that cattle pastures were the most fire-prone ecosystem. During much of the 6-mo @'dry@' season (total rainfall: 200-400 mm), sustained combustion was possible in this community within 24 h following rainfall events. Openings in the selectively logged forest would burn after 5-6 rainless days and in the second-growth forest after 8-10 d. In contrast, sustained combustion was not possible in the primary forest even after prolonged rainless periods (e.g., >30 d). Through an examination of bark tissues and simulated fires in primary forest we found that only a small percentage of the standing vegetation would likely survive even a low-intensity, surface fire. Mean (@+ SE) bark thickness for trees > 20 cm in diameter was 7.3 @+ 0.14 mm (n = 699) with values ranging from 1.5 to 28.9 mm. We found a significant relationship (r^2 = 0.77) between bark thickness and maximum cambium temperatures during fire simulations, and thereby estimated that in the event of a surface fire in the primary forest, 98% of all stems @? 1 cm diameter at breast height would be killed. Even though the autogenic factors in primary forest of the eastern Amazon create a microclimate that virtually eliminates the probability of fire, they are currently a common event in disturbed areas of Amazonia. As many as 8 x 10^6 ha burned in the Amazon Basin of Brazil in 1987 alone. In terms of current land-use patterns, altered microclimates, and fuel mass, there are also striking similarities between the eastern Amazon and East Kalimantan, Indonesia (the site of recent rain forest wildfires that burned 3.5 x 10^6 ha).

Few empirical data exist to examine the influence of regional scale environmental gradients on productivity patterns of plant species. In this paper we analyzed the productivity of several dominant grass species along two climatic gradients, mean annual precipitation (MAP) and mean annual temperature (MAT), in the Great Plains of the United States. We used climatic data from 296 weather stations, species production data from Natural Resource Conservation Service rangeland surveys and a geographic information system to spatially integrate the data. Both MAP and MAT were significantly related to annual above-ground net primary production (ANPP). MAP explained 54 % to 89 % of the variation in ANPP of two C4 short-grasses, Bouteloua gracilis and Buchloë dactyloides, and two C4 tall-grasses, Andropogon gerardii and Schizachyrium scoparium (= Andropogon scoparius). MAT explained 19 % to 41 % of the variation in ANPP of two C4 grasses, B. gracilis and B. dactyloides, and 41 % to 66 % of the variation in ANPP of two C3 grasses, Agropyron smithii and Stipa comata. ANPP patterns for species along both gradients were described by either linear, negative exponential, logistic, normal or skewed curves. Patterns of absolute ANPP (g/m2) for species differed from those of relative ANPP (%) along the MAP gradient. Responses were similar for species with common functional characteristics (e.g. short-grasses, tall-grasses, C3, C4). Our empirical results support asymmetric responses of species to environmental gradients. Results demonstrate the importance of species attributes, type of environmental gradient and measure of species importance (relative or absolute productivity) in evaluating ecological response patterns.

:  Feeding habits of Favonigobius gymnauchen, Repomucenus spp. and Tarphops oligolepis were examined during the period from May to August in 1999, 2000 and 2001 at a sandy beach in the central Seto Inland Sea, Japan. The three species of fish accounted for more than 60% of all fish collected in terms of number of individuals. All three species mainly consumed small crustaceans. However, the major prey of F. gymnauchen and Repomucenus spp. differed from that of T. oligolepis. F. gymnauchen and Repomucenus spp. mainly consumed mysids and small crangonid shrimp (<12 mm in body length), which predominated in the study area. T. oligolepis actively selected only epifaunal mysids Nipponomysis ornata and avoided crangonid shrimp and gammarids. The frequencies of occurrence of fish in the guts of the three dominant species were very low, and larval and juvenile Japanese flounder were not observed in any of the three fish species. The diet of juvenile Japanese flounder was similar to that of the three species. From these results, it appears that these three fish are competing species for the flounder.

Tropical rain forests do not always have a high diversity in tree species. In some cases, most of the trees in the canopy layer are a single species. This results in a low diversity among the other canopy tree species (fig. 1). Increasing dominance by one canopy species has little effect on the diversity of subcanopy trees (fig. 2). Such single-dominant forests are of two types: the dominant either persists at the site beyond one generation or it does not. In forests with a persistent dominant species (type I), one species may achieve dominance either by colonizing most of a large open patch and persisting thereafter or by gradually replacing the existing residents. The latter could take place either because the dominant is the species most resistant to deleterious physical or biotic conditions or because it is superior in competition to all others. One possible mechanism enabling one species to replace and exclude many others is the possession of an ectomycorrhizal (EM) association. Most tropical tree species sampled in the Neotropics and Africa have a different type, the vesicular-arbuscular mycorrhizal (VAM) association. Various characteristics of the EM association, such as its greater host specificity, the greater protection it gives its host from natural enemies and deleterious physical factors, and its ability to secure nutrients in both organic and inorganic form before they are available to a VAM association, may confer an advantage on its host tree species that allows it to replace itself and to displace or exclude VAM host trees. This \"mycorrhiza hypothesis\" needs to be tested; various types of surveys and experiments are suggested as appropriate tests. In forests where the VAM type is more common, most tree species are associated with the same set of fungal species and thus may be nearly equivalent in competitive ability for securing resources. Such equivalence promotes diversity, as suggested by earlier work. Examples of nonpersistent dominants (type II) are those that first colonize large open patches (>1 ha). Dominance probably results when few species are available for colonization during the short period open to invasion after a disturbance and few are adapted to the conditions in recently disturbed large patches. We suggest that after a single EM tree species achieves dominance in a type-I forest, other species in the same family are more likely to invade than are those of a different family. Thus, a many-species VAM rain forest might gradually shift to one with a single EM species dominant, leading to a forest of higher diversity dominated by several species from a few families that associate with EM fungi (e.g., as found in dipterocarp forests in southeastern Asia). The latter forests should tend to maintain their diversity because, like VAM forests, EM species in the same family may be nearly equivalent in competitive ability.

The aim of the present study was to identify seasonal changes in net phytoplankton communities as indicators of the trophic state in two lakes with differing morphometry and trophic states. These studies were conducted in Lake Maróz from May to November 1995 and 1996 and in Lake Jeziorak Mały in 1996 and 1997. Differences in the abundance, biomass, species diversity, and dominant taxa of particular groups of phytoplankton between these lakes were analyzed. Lake Jeziorak Mały, which has a smaller area and shallower depth, is more susceptible to degradation than is Lake Maróz. The results of studies confirm that there are differences in the net phytoplankton communities and physiochemical water parameters in the studied lakes. The abundance of blue-greens (60760 indiv. dm -3 ), dominated by Limnothrix redekei (Van Goor) Meffert, noted from May to October was almost nine-times higher in Lake Jeziorak Mały. The oxygen deficiency in the spring season and low mean visibility (0.7 m) also confirmed that this lake is polytrophic, while the lower abundance of blue-green algae (7022 indiv. dm -3 ), the great abundance of dinoflagellates, and the higher mean visibility (2.12 m) in Lake Maróz indicated that these waters are mesoeutrophic. Celem pracy było określenie różnic pomiędzy sezonowymi zmianami zbiorowisk fitoplanktonu sieciowego jako wskaźnika trofii w dwóch jeziorach o zróżnicowanej morfometrii i trofii. Badania prowadzono od maja do listopada w latach 1995 i 1996 w jeziorze Maróz oraz 1996 i 1997 w jeziorze Jeziorak Mały. Analizowano różnice w liczebności, biomasie, różnorodności gatunkowej i taksonach dominujących poszczególnych grup taksonomicznych fitoplanktonu pomiędzy tymi jeziorami. Jezioro Jeziorak Mały ze względu na mniejszą powierzchnię i głębokość jest jeziorem bardziej podatnym na degradację niż Maróz. Wyniki badań świadczą o zróżnicowaniu w zbiorowiskach fitoplanktonu sieciowego i fizyczno-chemicznych parametrach wody w badanych jeziorach. W jeziorze Jeziorak Mały odnotowano prawie 9-krotnie wyższe liczebności sinic (60760 osobn. dm -3 ), które dominowały (Limnothrix redekei) od maja do października, a także deficyty tlenowe w sezonie wiosennym oraz niską średnią widzialność (0,7 m), co może świadczyć o politroficznym charakterze wód tego zbiornika. Natomiast niższe liczebności sinic (7022 osobn. dm -3 ), liczne występowanie bruzdnic i wyższa średnia widzialność (2,1 m) w jeziorze Maróz wskazują mezo-eutroficzny charakter wód.

The aim of the study was to identify the similarities and differences in the phytoplankton in lakes Licheńskie and Ślesińskie based on the phytoplankton species composition and biomass. Quantitative and qualitative studies of phytoplankton from two heated lakes were conducted in 2004-2005. A total of 280 and 240 taxa were identified belonging to six phyla: Chlorophyta, Cyanoprokaryota, Cryptophyta, Dinophyta, Euglenophyta, and Heterokontophyta. Most of the taxa were incidental species with frequencies of less than 25%. The phytoplankton biomass in Lake Licheńskie ranged from 0.2 to 8.6 mg dm -3 . Throughout the growing season of 2004, the phytoplankton observed was comprised of diatoms and green algae, while in 2005 it was comprised of diatoms, green algae, and cryptophytes. The phytoplankton biomass in Lake Ślesińskie ranged from 0.4 to 13.2 mg dm -3 . Diatoms dominated in this lake in the spring and fall of both years (54-90%), while in summer 2004 diatoms and green algae dominated and in summer 2005 the dominants were cryptophytes, dinophytes, and cyanophytes. Na podstawie ilościowej i jakościowej analizy fitoplanktonu (skład gatunkowy, różnorodność taksonomiczna, biomasa ogólna wraz ze strukturą dominacji) wykazano podobieństwa i różnice rozwijającego się planktonu roślinnego w jeziorach Licheńskim i Ślesińskim. Badania prowadzono od marca do listopada w latach 2004-2005. Zidentyfikowano odpowiednio: 280 (J. Licheńskie) oraz 240 taksonów (J. Ślesińskie), które należały do 6 gromad: Chlorophyta, Cyanoprokaryota, Cryptophyta, Dinophyta, Euglenophyta oraz Heterokontophyta. Większość taksonów należała do gatunków przypadkowych, z frekwencją 0-25%. W J. Ślesińskim zaobserwowano ponadto większą liczbę gatunków absolutnie stałych i stałych niż w J. Licheńskim.W Jeziorze Licheńskim glony planktonowe utworzyły biomasę w zakresie od 0,2 do 8,6 mg dm -3 . W całym sezonie wegetacyjnym 2004 roku obserwowano fitoplankton o charakterze okrzemkowo-zielenicowym, a w 2005 roku okrzemkowo-zielenicowo-kryptofitowym. W Jeziorze Ślesińskim fitoplankton utworzył biomasę w zakresie od 0,4 do 13,2 mg dm -3 . Wiosną i jesienią w zbiorowiskach dominowały okrzemki (54-90%), natomiast latem współdominowały okrzemki i zielenice w 2004 roku oraz kryptofity, dinofity i sinice w 2005 roku. Wartości wskaźnika różnorodności Shannona-Weavera w Jeziorze Licheńskim średnio wynosiły: H n ' - 2,23; H b ' - 2,52, natomiast w Jeziorze Ślesińskim były niższe - H n ' - 2,08; H b ' - 2,10.Fitoplankton Jeziora Licheńskiego i Ślesińskiego kształtował się w obliczu odmiennych cech tych zbiorników, uwzględniających morfometrię, typ mieszania, czas retencji wody, zawartość tlenu, termikę wód oraz biodostępność fosforu. O odrębności planktonu roślinnego w obu jeziorach zadecydowała głównie różna liczebność i frekwencja taksonów oraz skład letniego zbiorowiska. Potwierdzeniem stały się różne wartości wskaźnika różnorodności gatunkowej Shannona-Weavera. Dość duże podobieństwo stwierdzono natomiast pod względem biomasy ogólnej oraz struktury wiosennego i jesiennego fitoplanktonu.

We studied factors shaping the diversity and abundance of small mammals in temperate woodlands in northeastern Poland at local (within the forests) and regional (among the forests) scales. We compared diversity and abundance of rodents and insectivores in habitats covering the widest possible range of forest productivity in Central Europe, from dry coniferous to wet deciduous forests. Small mammals were live-trapped during summer (2004–2006) on 206 circular plots. On the regional scale, the number of small mammal (rodent and shrew) species positively correlated with the proportion of deciduous stands in the woodland's area. In all forests, the bank vole (Myodes glareolus) and the yellow-necked mouse (Apodemus flavicollis) dominated, and their joint proportion in the community increased with share of deciduous forest habitats. On the local scale, the number of species increased significantly with productivity of both capture site and the whole woodland. Variation in rodent abundance was influenced mainly by forest productivity at the capture site, productivity of the whole woodland, and month of capture. Only a minor part of the variation in shrew abundance was explained by habitat productivity. The relationship between forest productivity and small mammal diversity was linear and positive on both local and regional scales. The different responses of rodents and insectivores to increasing productivity could be due to a wider ecological niche of shrews and their competition for space with rodents. Nomenclature: Mitchell-Jones et al., 1999; White, White & Walters, 2005; Wilson & Reeder, 2005; Seneta & Dolatowski, 2006.