Declining fruit production before death in a widely distributed tree species, Sorbus aucuparia L.

International audienceAbstractKey messageTrees are commonly thought to increase their seed production before death. We tested this terminal investment hypothesis using long-term data on rowan trees (Sorbus aucuparia) and found no support. Rather, seed production declined significantly before death, which points to the potential detrimental effects of reproductive senescence on regeneration in stands of old trees.ContextAging poses a fundamental challenge for long-lived organisms. As mortality changes with with age due to actuarial senescence, reproductive senescence may also lead to declines in fertility. However, life history theory predicts that reproductive investment should increase before mortality to maximize lifetime reproductive success, a phenomenon termed terminal investment.AimsTo date, it is unclear whether long-lived, indeterminantly growing trees experience reproductive senescence or display terminal investment.MethodsWe investigated fruit production of rowan (Sorbus aucuparia L.), widely distributed trees that live up to 150 years, as they approached death.ResultsIn our study population in Poland’s Carpathian Mountains, 79 trees that died produced up to 20% fewer fruits in the years before their demise compared to 199 surviving trees of the same population.ConclusionThe pattern of reproductive investment in S. aucuparia is suggestive of age-independent reproductive senescence rather than terminal investment. These findings highlight that the understanding of the generality of life history strategies across diverse taxa of perennial plants is still in its infancy

Does masting scale with plant size? High reproductive variability and low synchrony in small and unproductive individuals

Background and Aims In a range of plant species, the distribution of individual mean fecundity is skewed and dominated by a few highly fecund individuals. Larger plants produce greater seed crops, but the exact nature of the relationship between size and reproductive patterns is poorly understood. This is especially clear in plants that reproduce by exhibiting synchronized quasi-periodic variation in fruit production, a process called masting. Methods We investigated covariation of plant size and fecundity with individual-plant-level masting patterns and seed predation in 12 mast-seeding species: Pinus pinea, Astragalus scaphoides, Sorbus aucuparia, Quercus ilex, Q. humilis, Q. rubra, Q. alba, Q. montana, Chionochloa pallens, C. macra, Celmisia lyallii and Phormium tenax. Key Results Fecundity was non-linearly related to masting patterns. Small and unproductive plants frequently failed to produce any seeds, which elevated their annual variation and decreased synchrony. Above a low fecundity threshold, plants had similar variability and synchrony, regardless of their size and productivity. Conclusions Our study shows that within-species variation in masting patterns is correlated with variation in fecundity, which in turn is related to plant size. Low synchrony of low-fertility plants shows that the failure years were idiosyncratic to each small plant, which in turn implies that the small plants fail to reproduce because of plant-specific factors (e.g. internal resource limits). Thus, the behaviour of these sub-producers is apparently the result of trade-offs in resource allocation and environmental limits with which the small plants cannot cope. Plant size and especially fecundity and propensity for mast failure years play a major role in determining the variability and synchrony of reproduction in plants

Does masting scale with plant size? High reproductive variability and low synchrony in small and unproductive individuals

Centro de Investigación Forestal (CIFOR)In a range of plant species, the distribution of individual mean fecundity is skewed and dominated by a few highly fecund individuals. Larger plants produce greater seed crops, but the exact nature of the relationship between size and reproductive patterns is poorly understood. This is especially clear in plants that reproduce by exhibiting synchronized quasi-periodic variation in fruit production, a process called masting.The study was supported by the Polish National Science Centre (2017/24/C/NZ8/00151), the Polish State Committee for Scientific Research (6 P04G 045 21, 3 P04G 111 25), the Polish Ministry of Science and Higher Education (N304 362938), the US National Science Foundation (DEB 165511, DEB-02-40963, DEB-05-15756, DEB-10-20889, DBI-9978807, DEB-0642594, DEB-1556707), the Wilkes University Fenner Endowment, USDA/NIFA grant 2017-03807, the Hatch Act (225165) through the USDA National Institute of Food and Agriculture, PROPINEA (CC-16-095, AGL-2017-83828-C2), FORASSEMBLY (CGL2015-70558-P), BEEMED (SGR913) and a Marsden Fund grant (UOC1401).Peer reviewed9 Pág

Microgeographical, inter-individual, and intra-individual variation in the flower characters of Iberian pear Pyrus bourgaeana (Rosaceae)

Flower characteristics have been traditionally considered relatively constant within species. However, there are an increasing number of examples of variation in flower characteristics. In this study, we examined the variation in attracting and rewarding flower characters at several ecological levels in a metapopulation of Pyrus bourgaeana in the Doñana area (SW Spain). We answered the following questions: what are the variances of morphological and nectar characters of flowers? How important are intra-individual and inter-individual variance in flower characters? Are there microgeographical differences in flower characters? And if so, are they consistent between years? In 2008 and 2009, we sampled flowers of 72 trees from five localities. For six flower morphological and two nectar characteristics, we calculated coefficients of variation (CV). The partitioning of total variation among-localities, among-individuals, and within-individuals was estimated. To analyze differences among localities and their consistency between years, we conducted generalized linear mixed models. The CVs of nectar characters were always higher than those of morphological characters. As expected, inter-individual variation was the main source of variation of flower morphology, but nectar characters had significant variation at both intra- and inter-individual levels. For most floral traits, there were no differences among localities. Our study documents that variation is a scale-dependent phenomenon and that it is essential to consider intra- and inter-individual variance when investigating the causes and consequences of variation. It also shows that single year studies of floral characters should be viewed with caution

MASTREE+: Time-series of plant reproductive effort from six continents.

Significant gaps remain in understanding the response of plant reproduction to environmental change. This is partly because measuring reproduction in long-lived plants requires direct observation over many years and such datasets have rarely been made publicly available. Here we introduce MASTREE+, a data set that collates reproductive time-series data from across the globe and makes these data freely available to the community. MASTREE+ includes 73,828 georeferenced observations of annual reproduction (e.g. seed and fruit counts) in perennial plant populations worldwide. These observations consist of 5971 population-level time-series from 974 species in 66 countries. The mean and median time-series length is 12.4 and 10 years respectively, and the data set includes 1122 series that extend over at least two decades (≥20 years of observations). For a subset of well-studied species, MASTREE+ includes extensive replication of time-series across geographical and climatic gradients. Here we describe the open-access data set, available as a.csv file, and we introduce an associated web-based app for data exploration. MASTREE+ will provide the basis for improved understanding of the response of long-lived plant reproduction to environmental change. Additionally, MASTREE+ will enable investigation of the ecology and evolution of reproductive strategies in perennial plants, and the role of plant reproduction as a driver of ecosystem dynamics

SPPA of Picea abies mortality

The file consists of four sheets which present SPPA of mortality (p11{r}; p12{r} and g1,1+2 - g2,1+2 {r}) in years 1993-2013, 1993-2003 and 2003-2013:(1) overall mortality; (2) deer-caused mortality; (3) mortality due to mechanical causes and (4) mortality of unknown causes

Data from: Non-trophic plant-animal interactions mediate positive density dependence among conspecific saplings

Trophic plant-animal interactions (e.g. browsing by ungulates, insect attack) are an important and well-studied source of mortality in many tree populations. Non-trophic tree-animal interactions (e.g. deer antler rubbing) also frequently lead to tree death, and thus have significant effects on forest ecosystem functioning, but they are much less well studied than trophic interactions are. As deer populations have increased in recent decades in the Northern Hemisphere, their impact on tree populations via browsing and antler rubbing will increase. The aim of the study was to illustrate the potential ability of non-trophic plant-animal interactions to regulate the dynamics of a natural forest. Specifically, we wanted to determine whether and how density and distance-dependent processes affect sapling mortality caused by an antler rubbing by red deer (Cervus elaphus). We used a spatially explicit approach to examine density and distance-dependent mortality effects in almost two thousand Picea abies saplings over 20 years, based on a fully mapped permanent 14.4 ha plot in a natural subalpine old-growth spruce forest. Antler rubbing by deer was the main identified cause of sapling mortality, and it showed a strong spatial pattern: positive density dependence of survival among spruce saplings. Deer selectively killed spruce saplings that were isolated from conspecifics. In consequence, non-trophic plant-deer interactions were a major driver of the spatial pattern of P. abies sapling survival. The other mortality causes (e.g. breaking, overturning) did not show density-dependent patterns or their effects were much weaker. In the medium and long term, the density-dependent pattern of sapling mortality due to antler rubbing can alter the tree stand structure. Our results highlight the ecological relevance of non-trophic plant-animal interactions for forest ecosystem functioning

Stand Composition, Tree-Related Microhabitats and Birds—A Network of Relationships in a Managed Forest

Forest ecosystems contain many tree-related microhabitats (TreMs), which are used by various groups of organisms. Birds use TreMs for shelter, foraging and breeding. The abundance and variability of TreMs is related to tree stand composition and age. Over the last few centuries there has been a drastic decline in the structural and biological diversity of temperate forests over large areas of the Northern Hemisphere. These changes have reduced the diversity and quantity of TreMs. In this study we showed the relationships between stand composition, the abundance of TreMs, and the species richness of birds in a managed forest. We focused on TreMs that are important to birds: woodpecker breeding cavities, rot holes, dead branches, broken treetops, and perennial polypores. Our study was performed in a managed lowland temperate forest. In 94 plots (10 ha each) we made bird surveys and inventoried the stand composition and TreMs. Our results show that the tree stand composition of a managed forest affects the abundance of TreMs. The share of deciduous trees in the stand favors the occurrence of such TreMs as dead branches, rot holes and perennial polypores. The overall richness of bird species and the species richness of primary cavity nesters depended on the total basal area of oak, hornbeam and birch, whereas the species richness of secondary cavity nesters increased with the total basal area of birch and oak