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Question: Does long-term grazing exclusion affect plant species diversity? And does this effect vary with long-term phytomass accumulation across a regional productivity gradient?Location: Lowland grassy ecosystems across the state of Victoria, southeast Australia.Methods: Floristic surveys and phytomass sampling were conducted across a broad-scale productivity gradient in grazing exclusion plots and adjacent grazed areas. Differences in species richness, evenness and life-form evenness between grazed and ungrazed areas were analysed. The environmental drivers of longterm phytomass accumulation were assessed using multiple linear regression analysis.Results: Species richness declined in the absence of grazing only at the high productivity sites (i.e. when phytomass accumulation was 4 500 g m À2 ). Species evenness and life-form evenness also showed a negative relationship with increasing phytomass accumulation. Phytomass accumulation was positively associated with both soil nitrogen and rainfall, and negatively associated with tree cover. Conclusions:Competitive dominance is a key factor regulating plant diversity in productive grassy ecosystems, but canopy disturbance is not likely to be necessary to maintain diversity in less productive systems. The results support the predictions of models of the effects of grazing on plant diversity, such as the dynamic equilibrium model, whereby the effects of herbivory are contextdependent and vary according to gradients of rainfall, soil fertility and tree cover.

Disturbance has been considered essential for maintaining biodiversity in temperate grassy ecosystems in Australia. This has been particularly well demonstrated for inter-tussock plant species in C4 Themeda-dominated grasslands in mesic environments. Disturbance is also thought crucial to maintain the structure of preferred habitat for some animals. Relationships between disturbance and diversity may be contingent on ecosystem productivity, but little is known about the generality of the disturbance-promoting-diversity paradigm across the range of temperate grasslands. To date, the disturbance-promoting-diversity paradigm has taken a univariate approach to the drivers of biodiversity; rainfall is seen as a key driver of productivity, which then drives diversity, mediated by disturbance. We argue that this framework is too simplistic as biodiversity drivers are multivariate. We suggest that the accumulation of phytomass (live and dead plant material) is an important determinant of diversity in grassy ecosystems and that phytomass accumulation is governed by multiple drivers (of which disturbance is just one). For fauna, it is structure – not biomass – that determines habitat suitability, and this can be moderated by both abiotic and biotic drivers. The assumption that there is a consistent effect of disturbance on diversity through the range of temperate grassland settings in southern Australia ignores the likelihood that biodiversity also responds to other factors such as spatial heterogeneity in the environment, resource availability and climatic variation. We developed a conceptual model of the multivariate drivers of grassland diversity that explores mechanisms underpinning patterns of species richness. Despite four decades of research, it is clear that our understanding of the multivariate drivers of diversity across the range of temperate grasslands in Australia is still incomplete. Further research into the conditions under which disturbance is required to maintain biodiversity in grasslands is integral to conservation planning in these endangered systems.

Water availability is a critical driver of population dynamics in arid zones, and plant recruitment is typically episodic in response to rainfall. Understanding species’ germination thresholds is key for conservation and restoration initiatives. Thus, we investigated the role of water availability in the germination traits of keystone species in an arid ecosystem with stochastic rainfall. We measured seed germination responses of five arid species, along gradients of temperature and water potential under controlled laboratory conditions. We then identified the cardinal temperatures and base water potentials for seed germination, and applied the hydrotime model to assess germination responses to water stress. Optimum temperatures for germination ranged from 15 to 31 °C under saturated conditions (0 MPa), and three species had low minimum temperatures for germination (<3 °C). A small proportion of seeds of all species germinated under dry conditions (Ψ ≤ −1 MPa), although base water potential for germination (Ψ b50) ranged from −0.61 to −0.79 MPa. Species adhered to one of two germination traits: (i) the risk-takers which require less moisture availability for germination, and which can germinate over a wider range of temperatures irrespective of water availability (Casuarina pauper and Maireana pyramidata), and (ii) the risk-avoiders which have greater moisture requirements, a preference for cold climate germination, and narrower temperature ranges for germination when water availability is low (Atriplex rhagodioides, Maireana sedifolia and Hakea leucoptera). High seed longevity under physiological stress in H. leucoptera, combined with a risk-avoiding strategy, allows bet-hedging. The hydrotime model predicted lower base water potentials for germination than observed by the data, further supporting our assertion that these species have particular adaptations to avoid germination during drought. This study provides insights into the complex physiological responses of seeds to environmental stress, and relates seed germination traits to community dynamics and restoration in arid zones.

Supplementary Figure 1. Study region, showing the multiple sites that make up Terrick Terrick National Park (TTNP). The survey sites within TTNP are shown. The grey shaded areas show the modelled 1750 distribution of the Plains Grassland ecological vegetation class. Data source: DELWP (2008) NV1750_EVCBCS https://www.data.vic.gov.au/data /dataset/native-vegetation-modelled-1750-ecological-vegetation-classesSupplementary Table 1. Number of surveys conducted each year in each paddock.

Temperate native grasslands in Australia have been decimated across their range since European colonization (>200 years ago), and the few remaining remnants are mostly fragmented and degraded. Changes in disturbance type, particularly the removal of Indigenous fire and the introduction of livestock grazing, resulted in the local extinction of fire‐dependent and grazing‐sensitive native species, and led to an increase in exotic species. Recently, native grasslands have been acquired to improve the reservation status of the threatened community and management strategies have been implemented that involve the removal of livestock grazing and the reintroduction of fire or other biomass reduction methods. Here, we examine if the change in disturbance type—a disturbance switch—improves the native composition of grasslands. We review literature that reports instances where there has been a change in disturbance type to examine how grasslands respond to disturbance switching. We found mostly no change in native and exotic species richness when management changed from stock grazing to fire (at least in the short term, ≤10 years). Positive outcomes for other disturbance shifts (grazing → mowing, or cultivation → grazing) occurred when the disturbance type was accompanied by seed addition, or in landscapes where dispersal from nearby remnant sites was possible. This suggests that seed‐ and/or dispersal‐limitation may limit passive restoration outcomes in fragmented landscapes. It is necessary to determine the longer‐term impacts of switches in disturbance regimes, and whether recovery thresholds have already been crossed.

Summary A key task for native grassland managers is to assess when biomass reduction is necessary to maintain plant and animal diversity. This requires managers to monitor grassland structure. Parks Victoria and La Trobe University developed a method for rapid assessment of grassland structure using golf balls. Baker‐Gabb et al. (Ecological Management & Restoration, 17, 2016, p235) provide an example of where the method has been used to manage grassland structure to favour an endangered bird, the Plains‐wanderer (Pedionomus torquatus). In this study, we provide further critical analysis of the method using three data sets collected across different parts of Victoria that relate golf ball scores to various habitat attributes. We demonstrate how the golf ball score provides a good surrogate for key aspects of grassland structure. We show that the method does not provide a reliable surrogate for above‐ground biomass or vegetation cover, although we discuss how biomass and cover are not particularly good indicators of grassland structure. We argue that elements of grassland structure may be better correlated with desired conservation outcomes (e.g. plant species diversity or the presence of a particular species) than biomass or cover alone. We discuss examples of how the golf ball method has been used, and how it can be improved. The method will be particularly useful where a link can be demonstrated between golf ball scores and desired conservation outcomes, such as in the case of the Plains‐wanderer.

15Lower dormancy with rapid germination for arid seeds 2 16 Abstract 17 Seed germination traits are key drivers of population dynamics, yet they are under-18 represented in community ecology studies, which have predominately focussed on adult plant 19 and seed morphological traits. We studied the seed traits and germination strategy of eight 20 woody plant species to investigate regeneration strategies in the arid zone of eastern 21 Australia. To cope with stochastic and minimal rainfall, we predict that arid seeds will either 22 have rapid germination across a wide range of temperatures, improved germination under 23 cooler temperatures, or dormancy and/or longevity traits to delay or stagger germination 24 across time. To understand how temperature affects germination responses, seeds of eight 25 keystone arid species were germinated under laboratory conditions, and under three diurnal 26 temperatures (30/20°C, 25/15°C and 17/7°C) for 30 days. Seeds of species in this study are 27 currently stored for minesite restoration projects, hence we tested for decline in seed viability 28 across 24 months in dry storage at similar storage conditions (≈20°C). Six of the eight arid 29 species studied had non-dormant, rapidly germinating seeds, and only two species had 30 physiological dormancy traits. Seed longevity differed widely between species, from one 31 recalcitrant species surviving only months in storage (P50 = <3 months) and one serotinous 32 species surviving for many years (P50 = 84 months). Our results highlight the importance of 33 understanding the reproductive strategies of plant species in arid environments. Rapid 34 germination, the dominant seed trait of species included in this study, allows arid species to 35 capitalise on sporadic rainfall. However, some species also exhibit dormancy and delayed 36 germination; this an alternative strategy which spreads the risk of germination failure over 37 time. We highlight important seed traits and germination strategies of plants from an arid 38 zone with stochastic rainfall and discuss the implications for their restoration. 39 40 Lower dormancy with rapid germination for arid seeds 3 41 Introduction 42 Seed traits and germination strategies drive plant community dynamics and provide insight 43 into species' adaptations to environmental filters [1] and community composition [2]. Despite 44 this, seed traits are under-represented in community ecology studies [3-5]. Knowledge of 45 seed traits and germination strategies is necessary to describe plant niches, to anticipate 46 population dynamics under changes in land use [6], and to assess plant responses to the 47 environment [7]. By studying seed traits and germination responses we can obtain 48 ecologically meaningful data about the functional properties of plant communities that 49 improve predictions of plant assemblages under natural, and anthropogenic, environmental 50 change [8]. 51Seed traits and germination strategies, which are often unrelated to other plant traits [9], 52 can inform us about the repro...