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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.

Distribution patterns of the three species of sand-burrowing mysids, Archaeomysis vulgaris, Archaeomysis japonica and Iiella ohshimai were investigated, and also the diel and tidal distribution patterns of the dominant mysid A. vulgaris were investigated in the surf zone of an exposed and mesotidal sandy beach at Fukiagehama, Kagoshima Prefecture, southern Japan. The morphodynamic state of the beach was an intermediate type with a low-tide terrace or ridge/runnel. Habitat zonation was recognized among the three species during the entire study period (May and October of 2002 and 2003). A. vulgaris occurred from the high-water shoreline to the low-water shoreline during the daytime, whereas A. japonica was observed off the low-water shoreline and I. ohshimai was found far from the longshore bar. Habitats of A. vulgaris shifted along the beach slope, depending on the tidal changes at the shoreline. However, at low water in May of 2002 and 2003, most individuals of A. vulgaris were distributed in the intertidal runnel and on the lowtide terrace, rather than off the low-water shoreline. A. vulgaris had the highest population density of the three species, and fluctuations in its total mean density in the surf zone were estimated at each tide in May of 2003. These ranged from 2,956 indiv./square m at low water at night to 172 indiv./square m at middle water during the daytime. Distribution patterns characteristic of A. vulgaris are ecologically interpreted in relation to beach morphology, water flow regimes in the surf zone, and avoidance of fish-predation pressure.

A study of the structure and floristics at a transition zone from a monodominant to a more diverse forest in the African humid tropics was conducted to elucidate the mechanisms maintaining floristic diversity and the discontinuity between mixed forests and forests dominated by a single tree species (monodominant). The mixed forest's greater diversity could not be explained by substrate differences, greater maturity, or greater predation on seeds or juveniles. The dominant species of the monodominant forest was shade-tolerant and had poorly dispersed seeds. Tree species associated with the dominant were also found in the mixed forest. Monodominant and mixed forests occur side by side in the Asian and American tropics as well. As in the African example, many of these monodominant forests share most species with neighboring mixed forests. Characteristically, the dominant species have large seeds and shade-tolerant seedlings. Monodominant tropical forests are widespread and may indicate areas that have not experienced large-scale disturbance for long periods. Subsequent to major disturbance, it is likely that such forests regenerate and spread more slowly than mixed-forest associations.

In the framework of the established long-term monitoring of the Carpathian forest ecosystems, the assessment of changes in the plant species richness, type of plant communities and biometric characteristics and health status of forest trees, for getting relevant insights regarding the effects of the type of management, pollution and climate changes upon forest biodiversity and health, is one of the major objectives. The joint monitoring activities in the Carpathians from the Romanian territory were launched in 1998 by including six study sites in the network of twenty- six sites established for monitoring and assessment changes in the Carpathian forests at the scale of the entire Carpathian Mountain range. The paper addresses the results gained by repeating field studies protocols in 2005, in the same study sites from the Romanian stretch of Carpathian Mts, and shows first findings of the attempt of comparative analysis of two sets of empirical results collected in 1998 and 2005. The biometric characteristics of the investigated forest stands have changed between the years 1998–2005, due to moderate (Retezat) or intensive (Fundata) silvicultural interventions, progressive improvement of the amount of precipitations and significant decrease of pressure exerted by air pollution (Badea et al, 2006). Except a relatively low volume increment (4.8 cubic mper yr per ha) estimated for Fundata forest stands, which is located at the upper altitudinal limit (1360 m asl), good (6.7–7.1 cubic m per yr per ha) and high (10–11 cubic m per yr per ha) volume increment were estimated for Magura Odobesti and Stana de Vale, respectively Obcina Mare and Retezat sites, according with the tree species composition and yield class. The data related to the share of damaged trees (defoliation classes 2–4) indicate that between 1998 and 2005 the health status of forests from the Romanian Carpathians has been slightly improved, as well as for all Romanian forests (Badea et al, 2006). The recorded data indicate also that the dominant plant species have not been changed, and thus, the type of plants associations. However, they indicate an increase with 5 species (SdV), 8 species (F; MO; R), 16 species (RA) and 19 species (OM) in the plant species richness between 1998 and 2005. In addition, the results of the comparative analysis based on Jaccard coefficient of similarity, show profound changes (78 percent) in species composition, in particular subordinate and transient species.