The influence of plant on productivity, ground coverage and floral performance in grass-free lawns

The grass-free lawn is a novel development in modern ornamental horticulture where the traditional monoculture of grass is replaced by a variety of mowing-tolerant clonal forbs. It brings floral aesthetics and a diverse approach to the use of lawn space. How the of constituent forb affects the aesthetic and structural performance of grass-free lawns was investigated using grass-free lawns composed of four, six and twelve British native clonal perennial forb . Lawn productivity was seen to increase with increasing but the relationship was not linear. Plant cover was dynamic in all lawn types, varied between years and was not representative of individual ' floral performance. The behaviour of component common to all lawns suggested that lawns with 12 show greater structural stability than the lawns with a lower . Visual performance in lawns with the greatest was lower than in lawns with fewer , with increasing variety in floral size and individual floral productivity leading to a trade-off between diversity and floral performance. Individual were seen to have different aesthetic functions in grass-free lawns either by providing flowers, ground coverage or both.

Ostracoda in sediment core CRP-3 from the Ross Sea, Antarctica

A total of eighteen of marine ostracods, in at least twelve genera, have been recovered from Early and Late Oligocene glacio-marine sediments from boreholes CRP-3 and CRP-2/2A in the Victoria Land Basin, Ross Sea, Antarctica. Faunas are sparse and generally moderately-well preserved. Previously, three or closely related have been recorded only from glacial settings (Kuiperiana meridionalislain (Müller), Australicythere polylyca (Müller), Hemicytheridea aff. H. kinggeorgeensis Blaszyk), but palaeotemperatures somewhat higher than at present in the Ross Sea are suggested by the presence of Austrocythere reticulotuberculata Hartmann, Cluthia aff. C. antiqua Ayress & Drapala and Cytherella? sp. 4796. Majungaella sp. 4471 is an enigmatic component, representing a genus previously known only from warm Cretaceous and Eocene, and relatively warm interglacial Pliocene habitats in southern Gondwana and the Antarctic Peninsula. Palaeobiogeographical considerations indicate that during Early Oligocene times, the Ross Sea area had faunal links with both Antarctic Peninsula/South America and southern Australasia. Three present in the Early Oligocene glacial environments at Cape Roberts have survived to the Recent in the cool-cold Antarctic/Sub-Antarctic region: Austrocythere reticulotuberculata Hartmann, Australicythere polylyca (Müller), and Kuiperiana meridionalis (Müller).

Look before you leap : a confidence-based method for selecting criticality while avoiding negative populations in τ-leaping

The stochastic simulation algorithm was introduced by Gillespie and in a different form by Kurtz. There have been many attempts at accelerating the algorithm without deviating from the behavior of the simulated system. The crux of the explicit τ-leaping procedure is the use of Poisson random variables to approximate the of occurrences of each type of reaction event during a carefully selected time period, τ. This method is acceptable providing the leap condition, that no propensity function changes “significantly” during any time-step, is met. Using this method there is a possibility that s can, artificially, become negative. Several recent papers have demonstrated methods that avoid this situation. One such method classifies, as critical, those reactions in danger of sending populations negative. At most, one of these critical reactions is allowed to occur in the next time-step. We argue that the criticality of a reactant and its dependent reaction channels should be related to the probability of the becoming negative. This way only reactions that, if fired, produce a high probability of driving a reactant population negative are labeled critical. The of firings of more reaction channels can be approximated using Poisson random variables thus speeding up the simulation while maintaining the accuracy. In implementing this revised method of criticality selection we make use of the probability distribution from which the random variable describing the change in is drawn. We give several numerical examples to demonstrate the effectiveness of our new method.

-area and -individual relationships for tropical trees: A comparison of three 50-ha plots

1 -accumulation curves for woody plants were calculated in three tropical forests, based on fully mapped 50-ha plots in wet, old-growth forest in Peninsular Malaysia, in moist, old-growth forest in central Panama, and in dry, previously logged forest in southern India. A total of 610 000 stems were identified to and mapped to < Im accuracy. Mean and stem were calculated in quadrats as small as 5 m x 5 m to as large as 1000 m x 500 m, for a variety of stem sizes above 10 mm in diameter. -area curves were generated by plotting as a function of quadrat size; -individual curves were generated from the same data, but using stem as the independent variable rather than area. 2 -area curves had different forms for stems of different diameters, but -individual curves were nearly independent of diameter class. With < 10(4) stems, -individual curves were concave downward on log-log plots, with curves from different forests diverging, but beyond about 104 stems, the log-log curves became nearly linear, with all three sites having a similar slope. This indicates an asymptotic difference in richness between forests: the Malaysian site had 2.7 times as many as Panama, which in turn was 3.3 times as rich as India. 3 Other details of the -accumulation relationship were remarkably similar between the three sites. Rectangular quadrats had 5-27% more than square quadrats of the same area, with longer and narrower quadrats increasingly diverse. Random samples of stems drawn from the entire 50 ha had 10-30% more than square quadrats with the same of stems. At both Pasoh and BCI, but not Mudumalai. richness was slightly higher among intermediate-sized stems (50-100mm in diameter) than in either smaller or larger sizes, These patterns reflect aggregated distributions of individual , plus weak density-dependent forces that tend to smooth the abundance distribution and 'loosen' aggregations as stems grow. 4 The results provide support for the view that within each tree community, many have their abundance and distribution guided more by random drift than deterministic interactions. The drift model predicts that the -accumulation curve will have a declining slope on a log-log plot, reaching a slope of O.1 in about 50 ha. No other model of community structure can make such a precise prediction. 5 The results demonstrate that diversity studies based on different stem diameters can be compared by sampling identical s of stems. Moreover, they indicate that stem counts < 1000 in tropical forests will underestimate the percentage difference in richness between two diverse sites. Fortunately, standard diversity indices (Fisher's sc, Shannon-Wiener) captured diversity differences in small stem samples more effectively than raw richness, but both were sample size dependent. Two nonparametric richness estimators (Chao. jackknife) performed poorly, greatly underestimating true richness.

Tree diversity and ecosystem function: Can tropical multi- plantations generate greater productivity?

Results from the humid tropics of Australia demonstrate that diverse plantations can achieve greater productivity than monocultures. We found that increases in both the observed and the effective richness were significantly related to increased levels of productivity as measured by stand basal area or mean individual tree basal area. Four of five plantation were more productive in mixtures with other than in monocultures, offering on average, a 55% increase in mean tree basal area. A general linear model suggests that richness had a significant effect on mean individual tree basal area when environmental variables were included in the model. As monoculture plantations are currently the preferred reforestation method throughout the tropics these results suggest that significant productivity and ecological gains could be made if multi- plantations are more broadly pursued.

Tree -area and -diameter relationships at three lowland rain forest sites in Sumatra

Data from three forest sites in Sumatra (Batang Ule, Pasirmayang and Tebopandak) have been analysed and compared for the effects of sample area cut-off, and tree diameter cut-off. An 'extended inverted exponential model' is shown to be well suited to fitting tree--area curves. The model yields carrying capacities of 680 for Batang Ule, 380 for Pasirmayang, and 35 for Tebopandak (tree diameter >10cm). It would seem that in terms of carrying capacity, Tebopandak and Pasirmayang are rather similar, and both less diverse than the hilly Batang Ule site. In terms of conservation policy, this would mean that rather more emphasis should be put on conserving hilly sites on a granite substratum. For Pasirmayang with tree diameter >3cm, the asymptotic estimate is 567, considerably higher than the estimate of 387 for trees with diameter >10cm. It is clear that the diameter cut-off has a major impact on the estimate of the carrying capacity. A conservative estimate of the total of tree in the Pasirmayang region is 632 ! In sampling exercises, the diameter cut-off should not be chosen lightly, and it may be worth adopting field sampling procedures which involve some subsampling of the primary sample area, where the diameter cut-off is set much lower than in the primary plots.

Detecting patterns of diversification in the presence of both rate shifts and mass extinctions.

BACKGROUND: Recent methodological advances allow better examination of speciation and extinction processes and patterns. A major open question is the origin of large discrepancies in between groups of the same age. Existing frameworks to model this diversity either focus on changes between lineages, neglecting global effects such as mass extinctions, or focus on changes over time which would affect all lineages. Yet it seems probable that both lineages differences and mass extinctions affect the same groups. RESULTS: Here we used simulations to test the performance of two widely used methods under complex scenarios of diversification. We report good performances, although with a tendency to over-predict events with increasing complexity of the scenario. CONCLUSION: Overall, we find that lineage shifts are better detected than mass extinctions. This work has significance to assess the methods currently used to estimate changes in diversification using phylogenetic trees. Our results also point toward the need to develop new models of diversification to expand our capabilities to analyse realistic and complex evolutionary scenarios.

Effects of turnover on reserve site selection in a fragmented landscape

Changes in composition is an important process in many ecosystems but rarely considered in systematic reserve site selection. To test the influence of temporal variability in composition on the establishment of a reserve network, we compared network configurations based on data of small mammals and frogs sampled during two consecutive years in a fragmented Atlantic Forest landscape (SE Brazil). Site selection with simulated annealing was carried out with the datasets of each single year and after merging the datasets of both years. Site selection resulted in remarkably divergent network configurations. Differences are reflected in both the identity of the selected fragments and in the amount of flexibility and irreplaceability in network configuration. Networks selected when data for both years were merged did not include all sites that were irreplaceable in one of the 2 years. Results of estimation revealed that significant changes in the composition of the community occurred. Hence, temporal variability of community composition should be routinely tested and considered in systematic reserve site selection in dynamic systems.

How do subordinate and dominant in semi-natural mountain grasslands relate to productivity and land-use change?

Changes in agricultural practices of semi-natural mountain grasslands are expected to modify plant community structure and shift dominance patterns. Using vegetation surveys of 11 sites in semi-natural grasslands of the Swiss Jura and Swiss and French Alps, we determined the relative contribution of dominant, subordinate and transient plant in grazed and abandoned communities and observed their changes along a gradient of productivity and in response to abandonment of pasturing. The results confirm the humpbacked diversity–productivity relationship in semi-natural grassland, which is due to the increase of subordinate at intermediate productivity levels. Grazed communities, at the lower or higher end of the diversity gradient, suffered higher loss after grazing abandonment. loss after abandonment of pasturing was mainly due to a higher reduction in the of subordinate , as a consequence of the increasing proportion of dominant . When plant biodiversity maintenance is the aim, our results have direct implications for the way grasslands should be managed. Indeed, while intensification and abandonment have been accelerated since few decades, our findings in this multi-site analysis confirm the importance of maintaining intermediate levels of pasturing to preserve biodiversity.

Mean cover and frequencies of vascular plant during three decades around Abisko Scientific Research Station

Plant distributions are expected to shift and diversity is expected to decline as a result of global climate change, particularly in the Arctic where climate warming is amplified. We have recorded the changes in richness and abundance of vascular plants at Abisko, sub-Arctic Sweden, by re-sampling five studies consisting of seven datasets; one in the mountain birch forest and six at open sites. The oldest study was initiated in 1977-1979 and the latest in 1992. Total increased at all sites except for the birch forest site where richness decreased. We found no general pattern in how composition of vascular plants has changed over time. Three , Calamagrostis lapponica, Carex vaginata and Salix reticulata, showed an overall increase in cover/frequency, while two Equisetum taxa decreased. Instead, we showed that the magnitude and direction of changes in richness and composition differ among sites.