Regeneration and growth of coolibah,Eucalyptus coolabah subsp. arida,a riparian tree,in the Cooper Creek region of South Australia

Abstract Regeneration patterns of Eucalyptus coolabah Blakely & Jacobs subsp. arida (Blakely) L. Johnson & K. Hill (coolibah), a riparian tree of inland Australia, were inferred from size classes at two locations in South Australia; part of the floodplain of Cooper Creek and a swale in the Strzelecki Desert. These had contrasting water regimes; Cooper Creek floods on average once every 5–6 years whereas the swale has a continual water supply from a bore. A peak in size class distribution showed a regeneration event at each location but at different times. The one in the swale was more recent and was dated to the mid-1970s using aerial photography. Young (< 5 m tall) trees, interpreted as recent regeneration, were concentrated on specific topographic features, the top of a steep riverbank and a sand mound separate from the main dune system. Access to these features would have been difficult after flooding suggesting regeneration is dependent on protection from introduced herbivores. Field observations of reproductive status and canopy die-back showed coolibah condition was better in the swale. The relatively poorer condition of floodplain coolibahs was attributed to saline soils compounded by drier conditions rather than age.     

黄土高原关中地区植草沟径流水力学特性

植草沟被广泛应用于海绵城市建设中,可有效改善城市生态环境。为探究植草沟径流调控作用的机理,通过放水模拟试验,研究了5个坡度(1%、2%、3%、4%、5%)、5个放水流量(20、30、40、50、60 L·min^-1)组合条件下植草沟径流的水力学特性与断面流速分布变化规律。结果表明: 植草沟径流水力学特性主要表现为,随流量和坡度的增加,流速、雷诺数和佛汝德数均逐渐增加,曼宁糙率系数与Darcy-Weisbach阻力系数逐渐减小。流速(V)可以用流量(Q)与坡度(S)的幂函数V=0.3387Q^0.555S^0.6601来表示。雷诺数和佛汝德数变化范围分别为1160.95~6596.82和0.17~1.21,径流流态均为紊流,流型受坡度影响较大。流量和坡度较小时,两者对阻力系数的影响较大,试验条件下水流阻力系数与雷诺数呈负相关关系。植草沟径流断面流速分布表现出关于中心两侧对称分布,最大流速点位于中心水面处,断面流速等值线随流量和坡度的增加而逐渐变密,流速变化梯度增大。本研究可为黄土区海绵城市建设中植草沟的设计应用与水力计算提供理论基础,也可以通过分析植草沟径流水力学特性以探索其径流调控机理。     

Mapping the history of botanical collectors: spatial patterns,diversity, and uniqueness through time

This study examines changing spatial patterns of botanical collections over a 400 year time frame, focussing on the collections at the Natural History Museum (BM) in comparison with global patterns. The Plant Collector Resource Database, which contains 68,000 collector records was used to generate 250,667 unique collector × country × date records. We observe an exponential increase in the number of collectors over time. The activities of collectors were investigated in 50-year time-slices from 1650–2000. We specifically considered the geographic scope of collections (i.e., countries in which collections were made), the depth of collections (i.e., the number of collectors per country) and the uniqueness of collections (i.e., the proportion not duplicated in other herbaria). Uniqueness was highest for the earliest time-slice. Collector activity is shown to be strongly influenced by extrinsic factors such as the development of trade and empire, which allowed for collections to expand in scope and depth, and conflicts, which reduced collecting activity. A striking finding concerns the uniqueness of collections through time. The considerable unique element of the collections in herbaria highlighted by this study provides a strong motivation for digitization efforts to ensure that collections are accessible to address key questions in systematics, biogeography, and ecology.     

Middle gaspé limestones communities on the forillon Peninsula,Quebec, Canada (Siegenian,Lower Devonian)

Lower Devonian quiet-water marine benthic communities were examined to determine what parameters of community structure are maintained from locality to locality. The preserved elements of the communities are dominated by brachiopods. Each community has a characteristic taxonomic composition and diversity. From stratigraphically lowest to highest the communities include the newly proposed Dawsonelloides Community which has relatively low diversity, and is strongly dominated by a single species. The Beachia Community is less strongly dominated by a single species. The newly proposed Leptostrophia Community is very strongly dominated by a single species; less common species are rare or absent in the other communities. The Plicoplasia Community is slightly less diverse than the preceeding two communities, but unlike them has six species which dominate one or more collections and are commonly found in reduced abundance in the other collections. The gradual change in taxonomic composition and structure from one community to adjacent communities coupled with the similar structure of diversity and dominance within particular communities suggest that these characteristics are time-averaged and primary structural features of the communities.     

Effect of Nitrogen, Phosphorus and Potassium Additions on Plant Biomass and Soil Nutrient Content of a Swale Barrier Strand Community in Louisiana

Fertilization of a swale plant community with various levelsand combinations of nitrogen, phosphorus and potassium resultedin increased plant growth. Nitrogen addition produced the greatestincrease in biomass. At some high nitrogen levels, phosphoruslimited plant production. Potassium fertilization did not influenceplant growth. Phosphorus fertilization decreased the levelsof soil calcium, magnesium and manganese. A shore-perpendiculargradient in apparent saltwater inundation influenced soil pHand the concentrations of iron, phosphorus, and magnesium. Fertilizer effects, swale Scirpus americanus, Spartina patens, nitrogen limitation     

Vegetation Monitoring of Created Dune Swale Wetlands, Vandenberg Air Force Base, California

A monitoring program was established on San Antonio Terrace at Vandenberg Air Force Base to compare vegetation development at two created wetland sites and six nearby natural wetlands. The reference wetlands were chosen to represent a range of habitats in dune swale wetlands on the Terrace. Vegetation in the reference wetland plant communities varies from low-growing herbaceous marsh species with open canopies to closed canopies dominated by shrub or tree species. Transects and plots for long-term vegetation monitoring were established in all the wetlands, stratified by plant communities in the reference wetlands and by geomorphic location in the newly created wetlands. Quantitative vegetation and environmental data were collected at all the sites; measures included species distributions, species cover, and topographical elevations. Over the first three years of monitoring, variations in groundwater depth at different geomorphic locations in the created wetlands resulted in a variety of physical conditions for plant growth. In the first year, more than 100 plant species were observed, the majority being natives. During the next two years, species richness at the created wetland sites remained relatively stable and was higher than at the reference sites. Statistical comparisons of vegetation parameters by analysis of variance and hierarchical clustering exhibited patterns of increasing similarity between the created and reference wetlands. Long-term monitoring will be continued to track the progress of vegetation at the created sites, and to assess their development relative to the reference wetlands.     

Spatial and temporal growth dynamics of Barrier Island shrub thickets

Spatial and temporal dynamics of barrier island shrub thickets were investigated on Hog Island, a barrier island along the Eastern Shore peninsula of Virginia. The island thickets are dominated by the actinorhizal shrub, Myrica cerifera. On the accreting, northern half of the island, thickets expanded as swale area increased. Analysis of aerial photographs revealed that total thicket area increased by nearly 400% from 1949 to 1989, paralleling a substantial increase in area for the northern portion of the island. Thicket characteristics varied with the age and position of the three field sites on Hog Island. At the youngest site examined (20 yr), recruitment and shrub growth were high. Shrub growth remained high and recruitment continued in the stable central portions of the island (50 yr). However, at the oldest site near a bay side salt marsh (≈130 yr), recruitment was not evident, shrub growth was reduced, and mortality was most apparent. Several “life stages” for shrub thickets were identified relative to island accretion. After the stabilization of new land, seedlings establish and grow rapidly to form a thicket. Once established, a thicket rapidly expands in the relatively protected, mesic swale environment. Thicket decline follows, characterized by an increase in vine growth on and around the shrubs and the formation of gaps as the thicket breaks up. Spatial variation in M. cerifera thickets on Hog Island is related to length of time soils have been stabilized and, especially, to time since thicket establishment.     

Waterlogging responses in dune,swale and marsh populations of Spartina patens under field conditions

Summary Soil waterlogging responses were examined in three Spartina patens populations along a steep flooding gradient in coastal Louisiana. Root anatomy and physiological indicators of anaerobic metabolism were examined to identify and compare flooding responses in dune, swale and marsh populations, while soil physicochemical factors were measured to characterize the three habitats. Soil waterlogging increased along the gradient from dune to marsh habitats and was accompanied by increases in root porosity (aerenchyma). Aerenchyma in marsh roots was apparently insufficient to provide enough oxygen for aerobic respiratory demand, as indicated by high root alcohol dehydrogenase activities and low energy charge ratios. Patterns of root metabolic indicators suggest that dune and swale roots generally respired aerobically, while anaerobic metabolism was important in marsh roots. However, in each population, relatively greater soil waterloging was accompanied by differences in enzyme activities leading to malate accumulation. In dune and swale roots under these circumstances, depressed adenylate energy charge ratios may have been the result of an absence of increased ethanol fermentation. These trends suggest that: 1) Aerenchyma formation was an important, albeit incomplete, long-term adaptation to the prevalent degree of soil waterlogging. 2) All populations adjusted root metabolism in response to a relative (short-term) increase in soil waterlogging.     

Growth,production and biomass of the antarctic gastropod Laevilacunaria Antarctica Martens 1885

Twenty-one monthly collections of the Antarctic prosobranch gastropod Laevilacunaria antarctica Martens 1885 were obtained by divers at Signy Island, South Orkney Islands. Animals were contagiously distributed in the depth range 2–12 m below mean low water, with a mean monthly density of 199.0 ± 207.3 (S.D.) m^?2. Size frequency distribution was analysed, and at least three year classes identified. There was a prolonged annual recruitment from mid winter to mid summer, and juveniles dominated the population numerically for ten months of the year. Growth was seasonal, with a high rate during the Austral spring and summer, and a reduced rate during winter. A mean biomass of 356.3 mg dry tissue wt · m^?2 and a total annual production of 812.2 mg · m^?2 were estimated for the second year of study, and a production to biomass ratio of 2.28 obtained.     

THE GENETIC BASIS OF THE ECOLOGICAL AMPLITUDE OF SPARTINA PATENS. II. VARIANCE AND CORRELATION ANALYSIS

Reciprocal transplantations of Spartina patens genotypes from adjacent salt marsh, swale, and dune habitats provided evidence for genetic differentiation among subpopulations, due at least in part to contrasting selection regimes. Genet survival in the different habitats was related to the amount of genetic divergence. In the dune habitat, marsh ramets showed the lowest survival, swale ramets showed intermediate survival, and dune ramets showed the highest survival. This relationship was not reciprocal, however. The marsh habitat afforded an environment where survival was maximal for all genotypes. Thus, by comparison, the dune environment appeared to impose a more intense selection pressure, and the swale an intermediate selection pressure on Spartina patens. In each site resident genotypes tended to show greater relative fitness than aliens. This evidence for genetic divergence corroborates that previously reported on morphometric (Silander and Antonovics, 1979) and allozymic traits (Silander, 1984). High levels of phenotypic plasticity may permit greater adaptation to the spatially and temporally heterogeneous environment occupied by S. patens than would genetic variation alone. Dune and swale genets were more phenotypically plastic across traits examined than were marsh genotypes. The higher plasticity in these peripheral subpopulations may confer increased fitness among residents and compensate for observed declines in genetic variation. A slight decrease in genetic variability was evident from marsh to dune subpopulations. However, since the differences in genetic variation among subpopulations were small, and disparities did occur, it is unlikely that evolutionary divergence is retarded primarily by a lack of genetic variability in the characters considered. Evidence is presented to indicate that evolutionary divergence among subpopulations may be retarded by negative or unfavorable correlations among characters being selected simultaneously. These negative correlations may increase extinction probabilities in small peripheral populations, such as those represented by the dune or swale, and are likely to lower fitness. Based on these observations, I hypothesize that further microevolution may be retarded in peripheral dune and swale subpopulations, primarily by unfavorable genetic correlation structures among fitness components or characters under simultaneous selection. Contributing factors may include lowered genetic variance and higher levels of phenotypic plasticity.     

羊草种群密度与生长动态研究

 通过人为控制种群密度的栽培实验,从基株和构件水平上观察羊草无性系种群的生长动态,分析不同密度水平上羊草种群通过调节种群的生长、发育、增殖以及死亡过程来适应密度制约的途径。研究结果表明：1)羊草种群密度可在不同的构件水平间得到调节。当基株密度得到适当调节后便可减缓构件密度(无性系枝条、根茎芽等)的变化幅度和影响构件的发育进程。2)无性系枝条是羊草种群的主体,常在生长季后期出现大量增长,都处于生长旺盛的幼苗期,为翌年春季的返青积累能量和物质。3)单位面积总生物量随密度增加而提高,虽然尚未出现产量恒值现象,但存活枝条平均单株重(地上生物量)随密度增加呈下降趋势,这已反映出密度制约的作用。4)不同密度下羊草种群的生殖过程表现为：低密度时以无性繁殖为主,根茎芽的存活力较高;高密度时以有性繁殖为主,生殖分配值较大。     

Pollen use by Megalopta sweat bees in relation to resource availability in a tropical forest

1. Spatial and temporal availability of pollen helps shape bee foraging behaviour and productivity, which has been studied in great detail at the landscape level, but never in a diverse tropical forest. 2. To study the effect of spatio‐temporal variation in resource distribution on pollen use and productivity, we identified pollen from spatially explicit nest collections of two generalist sweat bees, Megalopta genalis Meade‐Waldo and M. centralis Friese, from Barro Colorado Island, Panama, a 50‐ha forest dynamics plot during the 2007 dry and early wet seasons. Pollen from nests collected in 1998–1999 without spatial information was also identified. 3. Bees used pollen of at least 64 species; many of these occurred in only one collection. The 2007 collections contained pollen of 35 different species, but were dominated by five species, especially Hura crepitans L. and Pseudobombax septenatum (Jacq.) Dugand. 4. Temporal availability, but not distance from nest, influenced flower use at a 50‐ha scale. 5. Body size was not associated with minimum flight distance as inferred from pollen collections. 6. Nest productivity and pollen diversity decreased from the dry to wet seasons, mirroring community‐level availability of floral resources. 7. Results suggest that on a scale of 50 ha, bees are choosing certain host plant species regardless of distance from the nest, but adjusting foraging behaviour opportunistically based on the temporal availability of host flowers.     

Monitoring coral reefs, seagrasses and mangroves in Costa Rica (CARICOMP)

The coral reefs, seagrasses and mangroves from the Costa Rican Caribbean coast have been monitored since 1999 using the CARICOMP protocol. Live coral cover at Meager Shoal reef bank (7 to 10 m depth) at the Parque Nacional Cahuita (National Park), increased from 13.3% in 1999, to 28.2% in 2003, but decreased during the next 5 years to around 17.5%. Algal cover increased significantly since 2003 from 36.6% to 61.3% in 2008. The density of Diadema antillarum oscillated between 2 and 7ind/m2, while Echinometra viridis decreased significantly from 20 to 0.6ind/m2. Compared to other CARICOMP sites, live coral cover, fish diversity and density, and sea urchin density were low, and algal cover was intermediate. The seagrass site, also in the Parque Nacional Cahuita, is dominated by Thalassia testudinum and showed an intermediate productivity (2.7 +/- 1.15 g/m2/d) and biomass (822.8 +/- 391.84 g/m2) compared to other CARICOMP sites. Coral reefs and seagrasses at the Parque Nacional Cahuita continue to be impacted by high sediment loads from terrestrial origin. The mangrove forest at Gandoca, within the Refugio Nacional de Vida Silvestre Gandoca-Manzanillo (National Wildlife Refuge), surrounds a lagoon and it is dominated by the red mangrove, Rhizophora mangle. Productivity and flower production peak was in July. Biomass (14 kg/m2) and density (9.0 +/- 0.58 trees/100 m2) in Gandoca were relatively low compared to other CARICOMP sites, while productivity in July in Costa Rica (4 g/m2/d) was intermediate, similar to most CARICOMP sites. This mangrove is expanding and has low human impact thus far. Management actions should be taken to protect and preserve these important coastal ecosystems.     

Foundations of the method of dating global fluctuations of abundance of oceanic sharks on the basis of the amount of fossil teeth in bottom sediments

A method for dating fluctuations in abundance of Elasmobranchii based on three parameters: density of fossil teeth on the ocean floor, density of modern species, and the rate of teeth replacement in modern species is proposed. As a model event, the substitution by the blue shark Prionace glauca of sharks of the genus Isurus that dominated from the Pliocene to the Late Holocene was used. It was determined that, at various values of the aforementioned parameters, the blue shark occupied a dominant position in the eastern Pacific between 302 and 3940 years ago. It is suggested that, in case of a large amount of material in geological collections using this method, a great number of paleoreconstructions of the development and changes in the oceanic biota may be carried out.     

Patterns of coral recruitment at the Gneering Shoals,southeast Queensland,Australia

Recruitment patterns of scleractinian corals were investigated at the Gneering Shoals, a coral-dominated rocky-reef south of the Great Barrier Reef, in subtropical Queensland. The density of recruits (mean of 0.8 to 6.3 recruits per tile (15 cm × 15 cm) pair from 4 sites) was the lowest ever recorded from six regions in tropical or subtropical eastern Australia that have been studied using directly comparable methods. Recruitment in summer was dominated by recruits from the Family Acroporidae, while corals from the Family Pocilloporidae recruited throughout the year. Recruits of massive corals andTurbinaria sp., which dominate the established coral communities, were absent. Possible explanations for the low recruitment rate in the region, include the depth of most sites (> 10m), competition for space with fouling organisms, and isolation, that is the failure of the south flowing East Australian Current to supply tropical larvae regularly from the Great Barrier Reef, 250 km to the north. The low coral recruitment rate at Gneering Shoals indicates that this region is unlikely to act as a stepping-stone for dispersal of tropical corals to more southern regions, which are more directly influenced by the East Australian Current.     

Distribution,abundance and ecology of the meiofauna in a tropical estuary along the west coast of India

The distribution and abundance of subtidal meiofauna in Mandovi estuary of Goa were studied from June 1983 to June 1984. Monthly faunal abundance ranged from 491 to 2791/10 cm² and dry weight biomass from 0.16 to 2.80 mg 10 cm². Free living nematodes were the dominant group contributing over 75% of the total density and 30 to 42% of the total biomass. Among nematodes the deposit feeders were more abundant in fine muddy substratum while epigrowth feeders dominated in sandy substratum.Harpacticoids were next, comprising 6.9 to 8.7% of the total meiofauna number, followed by turbellaria (3.8–4.5%), polychaeta (2.8–3.2%) and ostracods (1.6–4.5%) The contribution of other groups to faunal density was 4.5–6.2%. In the biomass the ostracods contributed most (29.8–54.7%), followed by nematodes (23.8–34.6%). Over 60% of the fauna occurred in the top 2 cm of the sediment and the faunal density reduced significantly with increasing depth in the sediment. The vertical distribution of meiofauna was positively correlated to the vertical distribution of Eh, chlorophyll a and interstitial water. Seasonality was greatly influenced by the south-west monsoon and the fauna quickly repopulated after the monsoon. Salinity, temperature and food influenced the faunal abundance.     

Presence, distribution, and diversity of iron-oxidizing bacteria at a landfill leachate-impacted groundwater surface water interface

We examined the presence of iron-oxidizing bacteria (IOB) at a groundwater surface water interface (GSI) impacted by reduced groundwater originating as leachate from an upgradient landfill. IOB enrichments and quantifications were obtained, at high vertical resolution, by an iron/oxygen opposing gradient cultivation method. The depth-resolved soil distribution profiles of water content, Fe²⁺, and total Fe indicated sharp gradients within the top 10 cm sediments of the GSI, where the IOB density was the highest. In addition, the vertical distribution of iron-reducing bacteria at the same sampling site mirrored the IOB distribution. Clone libraries from two separate IOB enrichments indicated a stratified IOB community with clear differences at short vertical distances. Alpha- and Betaproteobacteria were the dominant phylotypes. Clones from the near-surface sediment (1–2 cm below ground surface) were dominated by members of the Bradyrhizobiaceae and Comamonadaceae ; clones from the deeper sediments were phylogenetically more diverse, dominated by members of the Rhodocyclaceae . The iron deposition profiles indicated that active iron oxidation occurred only within the near-to-surface GSI sediments. The match between the iron deposition profiles and the IOB abundance profiles strongly hints at the contribution of the IOB community to Fe oxidation in this Fe-rich GSI ecosystem.     

Planktonic rotifer community structure in Adirondack,New York,U.S.A. lakes in relation to acidity,trophic status and related water quality characteristics

The structure of the mid-summer planktonic rotifer communities of 101 Adirondack lakes ranging in pH from 4.0 to 7.3 were characterized in relation to acidity and selected water quality parameters. More than 70 rotifer species were identified from collections in 1982 and 1984. None of the species collected could be considered acidobiontic or alkalibiontic. Keratella taurocephala was the most commonly collected rotifer, occurring in 94 of the study lakes. It was abundant throughout the range of pH investigated but was particularly dominant in acidic waters, averaging > 85 % of the rotifers collected from waters of pH < 5.0.Rotifer community structure can be related to three groups of water quality parameters. Community parameters (richness and diversity) are most highly correlated with parameters indicative of acidity status. Rotifer abundance correlates with trophic state indicators, i.e. chlorophyll a and total phosphorus, over the full range of pH investigated. However, in acidic lakes, rotifer abundance is related to true color and DOC, indicators of humic influences.The rotifer communities of the Adirondacks can be classified into four broad types: 1) A diverse, productive community of the more alkaline lakes, generally with 13 species, and dominated by Conochilus unicornis, Kellicottia bostoniensis, Kellicottia longispina, and Polyarthra major; 2) Relatively diverse communities of productive, highly colored acid lakes, with 8 species, and often with very large populations (> 200 · 1^–1) dominated by K. bostoniensis and K. taurocephala; 3) Depauperate (< 4 species) communities of clear water acid lakes with generally low density populations dominated by K. taurocephala (> 90 % of rotifers in each sample); and 4) Extremely depauperate (2–3 species) acid lake communities associated with small lakes with high flushing rates dominated by C. unicornis.     

Habitat associations of dryland avian communities during an extended dry period

The influence of resource availability on ecosystem function varies spatially and temporally, among and within ecosystems. Dramatic shifts in moisture-driven resources can drive bottom-up effects on animal behaviours and distributions. Further, complexity arises when landscapes are influenced by large mammalian grazers and predator-induced trophic cascades, such as those mediated by the dingo (Canis familiaris (Dingo)) in the eastern arid Strzelecki Desert in Australia. During the driest two-year period on record for this region, we investigated the persistence of avian communities associated with structurally distinct dunes and swale habitats, and across two different land management regimes (pastoral land with livestock and dingoes, and Sturt National Park managed for conservation without these animals). We grouped all birds into dietary functional groups to infer patterns of habitat use associated with available resources. We also compared incidental observations of the ‘winter’ bird community in part of the study region between the extended dry period of 2018/2019 and wet period of 2020/2021. Despite habitat partitioning, the avian community did not differ between land management regimes except in species richness during the dry period, likely driven by the low numbers of birds present during the surveys. Incidental observations indicated that insectivorous and omnivorous species dominated the bird community in the dry period, with granivorous species forming a greater proportion of the bird community during wet times. Birds with completely or partially insectivorous diets dominated avian species composition on surveys in the dry period, but there were distinct structural vegetation associations among functional groups, indicating that heterogeneity in vegetation structure was likely important for the conservation of refuges, which enable the persistence of avifauna during extended dry periods. Distinct habitat type, structure and available resources shaped avian communities in this landscape, during the extremely resource-limited extended dry period, with implications for conservation and management, particularly given the increasing drying effects of climate change.     

Diversity and biogeochemical structuring of bacterial communities across the Porangahau ridge accretionary prism, New Zealand

Sediments from the Porangahau ridge, located off the northeastern coast of New Zealand, were studied to describe bacterial community structure in conjunction with differing biogeochemical regimes across the ridge. Low diversity was observed in sediments from an eroded basin seaward of the ridge and the community was dominated by uncultured members of the Burkholderiales. Chloroflexi/GNS and Deltaproteobacteria were abundant in sediments from a methane seep located landward of the ridge. Gas-charged and organic-rich sediments further landward had the highest overall diversity. Surface sediments, with the exception of those from the basin, were dominated by Rhodobacterales sequences associated with organic matter deposition. Taxa related to the Desulfosarcina/Desulfococcus and the JS1 candidates were highly abundant at the sulfate-methane transition zone (SMTZ) at three sites. To determine how community structure was influenced by terrestrial, pelagic and in situ substrates, sequence data were statistically analyzed against geochemical data (e.g. sulfate, chloride, nitrogen, phosphorous, methane, bulk inorganic and organic carbon pools) using the Biota-Environmental matching procedure. Landward of the ridge, sulfate was among the most significant structuring factors. Seaward of the ridge, silica and ammonium were important structuring factors. Regardless of the transect location, methane was the principal structuring factor on SMTZ communities.