@article{HigginsClarkNathanetal.2003,
  author    = {Higgins, Steven I. and Clark, Stephen James and Nathan, Ran and Hovestadt, Thomas and Schurr, Frank Martin and Fragoso, Jose M. V. and Aguiar, Martin R. and Ribbens, Eric and Lavorel, Sandra},
  title     = {Forecasting plant migration rates : managing uncertainty for risk assessment},
  year      = {2003},
  abstract  = {1. Anthropogenic changes in the global climate are shifting the potential ranges of many plant species. 2. Changing climates will allow some species the opportunity to expand their range, others may experience a contraction in their potential range, while the current and future ranges of some species may not overlap. Our capacity to generalize about the threat these range shifts pose to plant diversity is limited by many sources of uncertainty. 3. In this paper we summarize sources of uncertainty for migration forecasts and suggest a research protocol for making forecasts in the context of uncertainty.},
  language  = {en}
}
@article{ThuillerAlbertAraujoetal.2008,
  author    = {Thuiller, Wilfried and Albert, C{\´e}cile H. and Ara{\´u}jo, Miguel B. and Berry, Pam M. and Cabeza, Mar and Guisan, Antoine and Hickler, Thomas and Midgley, Guy F. and Paterson, James and Schurr, Frank Martin and Sykes, Martin T. and Zimmermann, Niklaus E.},
  title     = {Predicting global change impacts on plant species' distributions : future challenges},
  issn      = {1433-8319},
  doi       = {10.1016/j.ppees.2007.09.004},
  year      = {2008},
  language  = {en}
}
@article{JeltschMoloneySchurretal.2008,
  author    = {Jeltsch, Florian and Moloney, Kirk A. and Schurr, Frank Martin and K{\"o}chy, Martin and Schwager, Monika},
  title     = {The state of plant population modelling in light of environmental change},
  issn      = {1433-8319},
  doi       = {10.1016/j.ppees.2007.11.004},
  year      = {2008},
  abstract  = {Plant population modelling has been around since the 1970s, providing a valuable approach to understanding plant ecology from a mechanistic standpoint. It is surprising then that this area of research has not grown in prominence with respect to other approaches employed in modelling plant systems. In this review, we provide an analysis of the development and role of modelling in the field of plant population biology through an exploration of where it has been, where it is now and, in our opinion, where it should be headed. We focus, in particular, on the role plant population modelling could play in ecological forecasting, an urgent need given current rates of regional and global environmental change. We suggest that a critical element limiting the current application of plant population modelling in environmental research is the trade-off between the necessary resolution and detail required to accurately characterize ecological dynamics pitted against the goal of generality, particularly at broad spatial scales. In addition to suggestions how to overcome the current shortcoming of data on the process-level we discuss two emerging strategies that may offer a way to overcome the described limitation: (1) application of a modern approach to spatial scaling from local processes to broader levels of interaction and (2) plant functional-type modelling. Finally we outline what we believe to be needed in developing these approaches towards a 'science of forecasting'.},
  language  = {en}
}
@article{SchiffersSchurrTielboergeretal.2008,
  author    = {Schiffers, Katja and Schurr, Frank Martin and Tielb{\"o}rger, Katja and Urbach, Carsten and Moloney, Kirk A. and Jeltsch, Florian},
  title     = {Dealing with virtual aggregation : a new index for analysing heterogeneous point patterns},
  issn      = {0906-7590},
  doi       = {10.1111/j.0906-7590.2008.05374.x},
  year      = {2008},
  language  = {en}
}
@article{HigginsFloresSchurr2008,
  author    = {Higgins, Steven I. and Flores, Olivier and Schurr, Frank Martin},
  title     = {Costs of persistence and the spread of competing seeders and sprouters},
  issn      = {0022-0477},
  doi       = {10.1111/j.1365-2745.2008.01391.x},
  year      = {2008},
  language  = {en}
}
@article{SchmollDietrichWinkeletal.2005,
  author    = {Schmoll, Tim and Dietrich, Volkmar and Winkel, Wolfgang and Epplen, J. T. and Schurr, Frank Martin and Lubjuhn, Thomas},
  title     = {Paternal genetic effects on offspring fitness are context dependent within the extrapair mating system of a socially monogamous passerine},
  year      = {2005},
  abstract  = {Avian extrapair mating systems provide an interesting model to assess the role of genetic benefits in the evolution of female multiple mating behavior, as potentially confounding nongenetic benefits of extrapair mate choice are seen to be of minor importance. Genetic benefit models of extrapair mating behavior predict that females engage in extrapair copulations with males of higher genetic quality compared to their social mates, thereby improving offspring reproductive value. The most straightforward test of such good genes models of extrapair mating implies pail-wise comparisons of maternal half-siblings raised in the same environment, which permits direct assessment of Paternal genetic effects oil offspring traits. But genetic benefits of mate choice may be difficult to detect. Furthermore, the extent of genetic benefits (in terms of increased offspring viability or fecundity) may depend oil the environmental context Such that the proposed differences between extrapair offspring (EPO) and within-pair offspring (WPO) only appear under comparatively poor environmental conditions. We tested the hypothesis that genetic benefits of female extrapair mate choice are context dependent by analyzing offspring fitness-related traits in the coal tit (Parus ater) in relation to seasonal variation in environmental conditions. Paternal genetic effects on offspring fitness were context dependent. as shown by a significant interaction effect of differential paternal genetic contribution and offspring hatching date. EPO showed a higher local recruitment probability than their maternal half-siblings if born comparatively late in the season (i.e.. when overall performance had significantly declined), while WPO performed better early in the season. The same general pattern of context dependence was evident when using the number of grandchildren born to a cuckolding female via her female WPO or EPO progeny as the respective fitness measure. However, we were unable to demonstrate that cuckolding females obtained a general genetic fitness benefit from extrapair fertilizations in terms of offspring viability or fecundity. Thus, another type of benefit Could be responsible for maintaining female extrapair mating preferences in the study population. Our results suggest that more than a single selective pressure may have shaped the evolution of female extrapair mating behavior in socially monogamous passerines.},
  language  = {en}
}
@article{SchurrBondMidgleyetal.2005,
  author    = {Schurr, Frank Martin and Bond, William J. and Midgley, Guy F. and Higgins, Steven I.},
  title     = {A mechanistic model for secondary seed dispersal by wind and its experimental validation},
  issn      = {0022-0477},
  year      = {2005},
  abstract  = {1 Secondary seed dispersal by wind, the wind-driven movement of seeds along the ground surface, is an important dispersal mechanism for plant species in a range of environments. 2 We formulate a mechanistic model that describes how secondary dispersal by wind is affected by seed traits, wind conditions and obstacles to seed movement. The model simulates the movement paths of individual seeds and can be fully specified using independently measured parameters. 3 We develop an explicit version of the model that uses a spatially explicit representation of obstacle patterns, and also an aggregated version that uses probability distributions to model seed retention at obstacles and seed movement between obstacles. The aggregated version is computationally efficient and therefore suited to large-scale simulations. It provides a very good approximation of the explicit version (R-2 > 0.99) if initial seed positions vary randomly relative to the obstacle pattern. 4 To validate the model, we conducted a field experiment in which we released seeds of seven South African Proteaceae species that differ in seed size and morphology into an arena in which we systematically varied obstacle patterns. When parameterized with maximum likelihood estimates obtained from independent measurements, the explicit model version explained 70-77\% of the observed variation in the proportion of seeds dispersed over 25 m and 67- 69\% of the observed variation in the direction of seed dispersal. 5 The model tended to underestimate dispersal rates, possibly due to the omission of turbulence from the model, although this could also be explained by imprecise estimation of one model parameter (the aerodynamic roughness length). 6 Our analysis of the aggregated model predicts a unimodal relationship between the distance of secondary dispersal by wind and seed size. The model can also be used to identify species with the potential for long-distance seed transport by secondary wind dispersal. 7 The validated model expands the domain of mechanistic dispersal models, contributes to a functional understanding of seed dispersal, and provides a tool for predicting the distances that seeds move},
  language  = {en}
}
@article{SchurrBossdorfMiltonetal.2004,
  author    = {Schurr, Frank Martin and Bossdorf, Oliver and Milton, Sue J. and Schumacher, J.},
  title     = {Spatial pattern formation in semi-arid shrubland : a priori predicted versus observed pattern characteristics},
  year      = {2004},
  abstract  = {Ecologists increasingly use spatial statistics to study vegetation patterns. Mostly, however, these techniques are applied in a purely descriptive fashion without a priori statements on the pattern characteristics expected. We formulated such a priori predictions in a study of spatial pattern in a semi-arid Karoo shrubland, South Africa. Both seed dispersal and root competition have been discussed as processes shaping the spatial structure of this community. If either of the two processes dominates pattern formation, patterns within and between shrub functional groups are expected to show distinct deviations from null models. We predicted the type and scale of these deviations and compared predicted to observed pattern characteristics. As predicted by the seed dispersal hypothesis, small-scale co-occurrence within and between groups of colonisers and successors was increased as compared to complete spatially random arrangement of shrubs. The root competition predictions, however, were not met as shrubs of similar rooting depth co- occurred more frequently than expected under random shrub arrangement. Since the distribution of rooting groups to the given shrub locations also failed to match the root competition predictions, there was little evidence for dominance of root competition in pattern formation. Although other processes may contribute to small-scale plant co-occurrence, the sufficient and most parsimonious explanation for the observed pattern is that its formation was dominated by seed dispersal. To characterise point patterns we applied both cumulative (uni- and bivariate K-function) and local (pair- and mark-correlation function) techniques. Based on our results we recommend that future studies of vegetation patterns include local characteristics as they independently describe a pattern at different scales and can be easily related to processes changing with interplant distance in a predictable fashion.},
  language  = {en}
}
@article{SchurrDeanMiltonetal.2004,
  author    = {Schurr, Frank Martin and Dean, W. R. J. and Milton, Sue J. and Jeltsch, Florian},
  title     = {A conceptual model linking demography of the shrub species Grewia flava to the dynamics of Kalahari savannas},
  year      = {2004},
  abstract  = {Environmental heterogeneity is a major determinant of plant population dynamics. In semi-arid Kalahari savannas, heterogeneity is created by savanna structure, i.e. by the spatial arrangement and temporal dynamics of woody plant and open grassland microsites. We formulate a conceptual model describing the effects of savanna dynamics on the population dynamics of the animal-dispersed shrub Grewia flava. From empirical results we derive model rules describing effects of savanna structure on several processes in Grewia's life cycle. By formulating the model, we summarise existing information on Grewia demography and identify gaps in this knowledge. Despite a number of such gaps, the model can be used to make certain quantitative predictions. As an example, we apply the model to investigate the role of seed dispersal in Grewia encroachment on rangelands. Model results show that cattle promote encroachment by depositing substantial numbers of seeds in open areas, where Grewia is otherwise dispersal-limited. Finally, we draw some general conclusions about Grewia's life history and population dynamics. Under natural conditions, concentrated seed deposition under woody plants appears to be a key process causing the observed association between Grewia and other woody plants. Furthermore, low rates of recruitment and high adult survival result in slow-motion dynamics of Grewia populations. As a consequence, Grewia populations interact with savanna dynamics on long temporal and short to intermediate spatial scales.},
  language  = {en}
}
@article{JeltschTewsSchurr2004,
  author    = {Jeltsch, Florian and Tews, J{\"o}rg and Schurr, Frank Martin},
  title     = {Seed dispersal by cattle may cause shrub encroachment of Grewia flava on southern Kalahari rangelands},
  year      = {2004},
  abstract  = {Shrub encroachment, i.e. the increase in woody plant cover, is a major concern for livestock farming in southern Kalahari savannas. We developed a grid-based computer model simulating the population dynamics of Grewia flava, a common, fleshy-fruited encroaching shrub. In the absence of large herbivores, seeds of Grewia are largely deposited in the sub-canopy of Acacia erioloba. Cattle negate this dispersal limitation by browsing on the foliage of Grewia and dispersing seeds into the grassland matrix. In this study we first show that model predictions of Grewia cover dynamics are realistic by comparing model output with shrub cover estimates obtained from a time series of aerial photographs. Subsequently, we apply a realistic range of intensity of cattle-induced seed dispersal combined with potential precipitation and fire scenarios. Based on the simulation results we suggest that cattle may facilitate shrub encroachment of Grewia. The results show that the severity of shrub encroachment is governed by the intensity of seed dispersal. For a high seed dispersal intensity without fire (equivalent to a high stocking rate) the model predicts 56\% shrub cover and 85\% cell cover after 100 yr. With fire both recruitment and shrub cover are reduced, which may, under moderate intensities, prevent shrub encroachment. Climate change scenarios with two-fold higher frequencies of drought and wet years intensified shrub encroachment rates, although long-term mean of precipitation remained constant. As a management recommendation we suggest that shrub encroachment on rangelands may be counteracted by frequent fires and controlling cattle movements to areas with a high proportion of fruiting Grewia shrubs},
  language  = {en}
}