Contrasting Resource Dynamics in Mast Years for European Beech and Oak—A Continental Scale Analysis

Resource allocation to different plant tissues is likely to be affected by high investment into fruit production during mast years. However, there is a large knowledge gap concerning species-specific differences in resource dynamics. We investigated the influence of mast years on stem growth, leaf production, and leaf carbon (C), nitrogen (N), and phosphorus (P) concentrations and contents in Fagus sylvatica, Quercus petraea, and Q. robur at continental and climate region scales using long-term data from the International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) and similar datasets. We discussed the results in the light of opposing resource dynamics hypotheses: (i) resource accumulation before mast years and exhaustion after mast years (resource storage hypothesis), (ii) shifting resources from vegetative to generative compartments (resource switching hypothesis), and (iii) investing resources concurrently in both vegetative and generative compartments (resource matching hypothesis). Linear mixed-effects modelling (LMM) showed that both stem growth and leaf production were negatively influenced by weather conditions which simultaneously lead to high fruit production. Thus, the impact of generative on vegetative growth is intermixed with effects of environmental factors. Superposed epoch analyses and LMM showed that for mast behaviour in F. sylvatica, there are indicators supporting the resource storage and the resource switching hypotheses. Before mast years, resources were accumulated, while during mast years resources switched from vegetative to generative tissues with reduced stem and leaf growth. For the Quercus species, stem growth was reduced after mast years, which supports the resource storage hypothesis. LMM showed that leaf C concentrations did not change with increasing fruit production in neither species. Leaf N and P concentrations increased in F. sylvatica, but not in Quercus species. Leaf N and P contents decreased with increasing fruit production in all species, as did leaf C content in F. sylvatica. Overall, our findings suggest different resource dynamics strategies in F. sylvatica and Quercus species, which might lead to differences in their adaptive capacity to a changing climate.

Oral Processing Behavior of Diana Monkeys (Cercopithecus diana) in Taï National Park, Côte d’Ivoire

Primates are hypothesized to “fall back” on challenging-to-process foods when preferred foods are less available. Such dietary shifts may be accompanied by changes in oral processing behavior argued to be selectively important. Here, we examine the oral processing behavior of Diana monkeys (<i>Cercopithecus diana</i>) in the Taï Forest across their dietary breadth, testing relationships among food intake, fruit availability, preference, and oral processing behaviors including those involved in food ingestion and breakdown. We conducted 1,066 focal follows from April 2016 to September 2017 documenting frequencies of incisor, canine, and cheek tooth mastications (i.e., chews) per ingestive action (<i>n</i> = 11,906 feeding events). We used phenological survey and scan sample data collected between 2004 and 2009 to examine dietary preference and food availability. Our analyses show that Diana monkeys processed foods in significantly different ways (<i>H</i>₂ = 360.8, <i>p</i> &#x3c; 0.001), with invertebrates requiring the least oral processing, fruit requiring intermediate amounts, and leaves requiring the most oral processing. There was no relationship between fruit availability and consumption of preferred or nonpreferred fruits (<i>p</i> &#x3e; 0.05); however, preferred fruits were processed with significantly fewer mastications (i.e., less chewing) than nonpreferred fruits (<i>U</i> = 6,557, <i>p</i> &#x3c; 0.001). We thus demonstrate that, when preferred foods are scarce, Diana monkeys do not fall back on difficult-to-process foods. Changes in processing profiles occurred throughout the year and not solely when preferred foods were in short supply. Though preferred fruits required less processing than nonpreferred fruits, we found no relationship between fruit preference and fruit availability. Diana monkeys’ lack of readily identifiable fallback foods may be attributable to the relatively high tree diversity and productivity of the Taï Forest. We conclude that Diana monkeys engage in resource switching, consuming a relatively easy-to-process diet year-round.

Aestivation dynamics of bogong moths (Agrotis infusa) in the Australian Alps and predation by wild pigs (Sus scrofa)

We document predation of aestivating bogong moths (Agrotis infusa) by wild pigs (Sus scrofa) at a location in the Australian Alps. This is the first known record of pigs preying on bogong moths. Wild pigs are recent colonisers of the region, though already the population appears seasonally habituated to foraging on aestivating moths. This is indicative of adaptation of a feral animal undertaking dietary resource switching within what is now a modified ecosystem and food web. The significance of this predation on moth abundance is unclear. Long-term monitoring to compare numbers of moths with historical surveys undertaken before the colonisation by wild pigs will require that they are excluded from aestivation sites. Our surveys in 2014–15 observed bogong moths to arrive about one month earlier compared with a similar survey in 1951–52, though to also depart earlier.

Patterns of post-fire flowering and fruiting in Chlorogalum pomeridianum var. pomeridianum (DC.) Kunth in southern California chaparral

For many geophytes living in Mediterranean ecosystems, the passage of fire can produce bursts of flowering, seed production, vegetative growth, and seedling recruitment. In the present study, we investigated patterns of flowering and fruit production of the chaparral geophyte Chlorogalum pomeridianum (common soap plant) at two sites: one burned in a prescribed fire and one in nearby unburned chaparral. Both sites burned in a wildfire 2 years later, and we continued monitoring marked plants for an additional 6 years, enabling us to observe the effects of recent reburning on reproduction and growth. We found that flowering was stimulated by fire but was not strictly fire-dependent. There was a positive relationship between bulb size and leaf area, as well as between these two characteristics and flower and fruit production. Flower stalk initiation occurred when plants reached a minimum leaf area of ~1000 cm2, indicating that a minimum bulb size must be reached before reproductive effort is initiated. Direct herbivory of flowering stalks reduced fruiting and leaf herbivory indirectly prevented the initiation of flowering stalks. In the first several years after fire, flower and fruit production could be explained by resource matching but in subsequent years, resource matching was replaced by resource switching.