Differences in climate-growth relationships between two tree species that co-occur in a seasonally dry tropical forest in Northeastern Brazil

Seasonally dry tropical forests are an important global climate regulator and represent one of main drivers of carbon sink dynamics. However, projections of climate change suggest future productivity losses and negative impacts on forest functioning. Understanding the interaction between climate variability and tree growth responses between species with different growth strategies represents a crucial challenge to forecast ecosystem functioning in the future. Here we used tree ring chronology to evaluate changes in growth and climate sensitivity of two tropical tree species that co-occur in a seasonally dry tropical forest in Brazil: Cedrela odorata and Ceiba glaziovii. Using Pearson correlations and linear regressions we explored how growth variability is correlated with local (precipitation, temperature) and global (ocean temperature and El Niño Southern Oscillation - ENSO) climatic factors. Tree growth was closely related with precipitation in C. odorata (r = 0.59) and C. glaziovii (0.24). Differences were found at monthly level, which C. odorata showing greater sensitivity in the beginning of rainy season. The South Atlantic Temperature was positively correlated with C. odorata, while ENSO was negatively correlated. Our results showed a dominant effect of precipitation on tree growth and suggest that are different growth strategies among species, which C. odorata being the most sensitive to drought and C. glaziovii more adapted with parenchyma in trunk. Therefore, C. odorata is probably more vulnerable to the deleterious effects of future climate change than C. glaziovii. Our findings highlight the importance of understanding the climate sensitivity of different seasonally dry tropical forest species, which is critical to predicting carbon dynamics in tropical regions. These also reveal that differences in sensitivity must be considered when prioritizing conservation measures for seasonally dry tropical forests.     

A tree-ring based comparison of Terminalia superba climate–growth relationships in West and Central Africa

Tropical lowland forests are characterized by humid climate conditions with interannual variations in amount of precipitation, length of dry season, and relative humidity. The African tree species, Terminalia superba Engl. & Diels has a large distribution area and potentially incorporates these variations in its tree rings. Tree ring analysis was performed on 60 plantation trees (increment cores) and 41 natural trees (stem disks) from Ivory Coast and the Congolese Mayombe Forest. Natural forests and old plantations (50–55 years) showed similar growth patterns. Regional chronologies were developed for the two sample regions and showed a long-distance relationship for the period 1959–2008. Growth in the Mayombe was associated with early rainy season precipitation, but no relation was found between tree growth and precipitation in Ivory Coast. Congolese trees possibly show a higher climate-sensitivity than Ivorian trees, because precipitation in the Mayombe is more limiting, and Congolese T. superba trees are found closer to the margins of their distribution. Likewise, tree growth in the Mayombe was also influenced by the SSTs of the Gulf of Guinea and the South Atlantic Ocean during the early rainy season. However, tree growth was influenced by ENSO in both regions. In the Mayombe, La Niña years were associated with stronger tree growth whereas in Ivory Coast, El Niño years corresponded with stronger tree growth. The presented relation between ENSO, precipitation and tree growth is original for equatorial African forests, suggesting an influence of global climate variability on tree growth.     

Site-dependent growth responses to climate in two major tree species from tropical dry forests of southwest Ecuador

Tropical dry forests (hereafter TDFs) have been extensively logged and converted into croplands or grasslands worldwide. Tumbesian forests in southwest Ecuador are among the most diverse and endangered TDFs. They face seasonal droughts of varied severity and are also subjected to episodic very wet and cloudy conditions during El Niño events. However, we lack a local quantification of their responses to regional climate (temperature, precipitation, cloud cover) and El Niño which could change across sites. Here we use dendrochronology to quantify the radial-growth rates and the responses to climate (mean temperatures, precipitation amount, cloud cover and drought severity) of two major tree species forming annual rings (Geoffroea spinosa, Handroanthus chrysanthus) in three TDFs with different local climate conditions. The lowest (1.0 mm yr⁻¹) and the highest (2.1 mm yr⁻¹) radial-growth rates of both tree species were found in the hottest-driest and moderately hot sites, respectively. G. spinosa growth responded positively to wet, cool and cloudy conditions in the hottest-driest and moderately hot sites, but the most intense response to drought was observed in the driest site at 1–5 months long scales. H. chrysanthus growth reacted positively to high growing-season precipitation in all sites, particularly in the driest site, and to cloudy conditions in moderately hot sites. The growth of H. chrysanthus was negatively associated to the Southern Oscillation Index in the dry-hot and in the moderately hot sites. Tree species coexisting in TDFs show varied growth responses to regional weather variability, drought severity and El Niño events across sites with different local climate conditions.     

Dendroclimatic potential of the Adesmia pinifolia shrub growing at high altitude in the Andes foothills

Highland ecosystems of western Andes foothills are currently poorly represented by dendrochronological information. The dendroclimatological potential of the Acerillo plant (Adesmia pinifolia), a shrub species well represented at these latitudes, was investigated. We reported the first ring width chronology of A. pinifolia growing at the central semi-arid Andes foothills of Argentina. We collected living and dead wood samples of Acerillo resulting in a chronology covering the period 1609–2020 (412 years) with a well replication from 1655 to present (> 13 samples). Bootstrapping correlation analysis revealed a strong positive relationship between our chronology and monthly precipitation and with the Standardized Precipitation Evapotranspiration Index (SPEI-12 months). For the last 40 years however, strong negative correlations with temperature are evidenced. The dendrochronological record also showed a negative relationship with sea surface temperatures from the Tropical Pacific, suggesting teleconnections with the El Niño Southern Oscillation (ENSO) phenomenon. The strong hydroclimatic signal recorded in the A. pinifolia chronology represents a high opportunity to produce long-term proxy climate data for the Central Andes foothills, an extensive region devoid of trees but of hydrological relevance for the support of important economic activities.     

El Niño and related monsoon drought signals in 523-year-long ring width records of teak (Tectona grandis L.F.) trees from south India

We present a 523-year (A.D. 1481–2003) tree-ring width index chronology of Teak (Tectona grandis L.F.) from Kerala, Southern India, prepared from three forest sites. Dendroclimatological investigations indicate a significant positive relationship between the tree-ring index series and Indian summer monsoon rainfall (ISMR) and related global parameters like the Southern Oscillation Index (SOI). A higher frequency of occurrence of low tree growth is observed in years of deficient Indian monsoon rainfall (droughts) associated with El Niño since the late 18th century. Prior to that time, many low tree growth years are detected during known El Niño events, probably related to deficient Indian monsoon rainfall. The general relationship between ISMR and El Niño is known to be negative and the spatial correlations between our Kerala tree-ring chronology and sea surface temperatures (SSTs) over the Niño regions follow similar patterns as those for ISMR. This relationship indicates strong ENSO-related monsoon signals in the tree-ring records. These tree-ring chronologies with a high degree of sensitivity to monsoon climate are useful tools to understand the vagaries of monsoon rainfall prior to the period of recorded data.     

Dendrochronological potential of four neotropical dry-forest tree species: Climate-growth correlations in northeast Brazil

Tropical dry forests (TDF) are highly important tropical forest ecosystems. Yet, these forests are highly threatened, usually neglected and only poorly studied. Understanding the long-term influences of environmental conditions on tree growth in these forests is crucial to understand the functioning, carbon dynamics and potential responses to future climate change of these forests. Dendrochronology can be used as a tool to provide these insights but has only scantly been applied in (dry) tropical forests. Here we evaluate the dendrochronological potential of four Caatinga neotropical dry forest tree species – Aspidosperma pyrifolium, Ziziphus joazeiro, Tabebuia aurea, and Libidibia ferrea – collected in two locations in northeastern Brazil (Sergipe state). We provide an anatomical characterization of the ring boundaries for the four species and investigate correlations of their growth with local and regional climatic variables. All four species form annual rings and show high inter-correlation (up to 0.806) and sensitivity (up to 0.565). Growth of all species correlated with local precipitation as well as with sea-surface temperatures in the tropical Atlantic and/or tropical Pacific oceans. We also show teleconnections between growth and the El Niño South Oscillation. The strong dependence of tree on precipitation is worrisome, considering that climate change scenarios forecast increased drought conditions in the Caatinga dry forest. Including more species and expanding dendrochronological studies to more areas would greatly improve our understanding of tree growth and functioning in TDFs. This type of knowledge is essential to assist the conservation, management and restoration of these critical tropical ecosystems.     

The effects of El Niño‐Southern Oscillation events on intertidal seagrass beds over a long‐term timescale

El Niño‐Southern Oscillation (ENSO) events can cause dramatic changes in marine communities. However, we know little as to how ENSO events affect tropical seagrass beds over decadal timescales. Therefore, a diverse array of seagrass (Thalassia hemprichii) habitat types were surveyed once every 3 months for 16 years (January 2001 to February 2017) in a tropical intertidal zone that is regularly affected by both ENSO events and anthropogenic nutrient enrichment. La Niña and El Niño events had distinct effects on the biomass and growth of T. hemprichii. During La Niña years, higher (a) precipitation levels and (b) seawater nitrogen concentrations led to increases in seagrass leaf productivity, canopy height, and biomass. However, the latter simultaneously stimulated the growth of periphyton on seagrass leaves; this led to decreases in seagrass cover and shoot density. More frequent La Niña events could, then, eventually lead to either a decline in intertidal seagrass beds or a shift to another, less drought‐resistant seagrass species in those regions already characterized by eutrophication due to local anthropogenic activity.     

Climate–growth relationships of the dominant tree species from semi-arid savanna woodland in Ethiopia

Long-term climate–growth relationships, were examined in tree rings of four co-occurring tree species from semi-arid Acacia savanna woodlands in Ethiopia. The main purpose of the study was to prove the presence of annual tree rings, evaluate the relationship between radial growth and climate parameters, and evaluate the association of El Niño and drought years in Ethiopia. The results showed that all species studied form distinct growth boundaries, though differences in distinctiveness were revealed among the species. Tree rings of the evergreen Balanites aegyptiaca were separated by vessels surrounding a thin parenchyma band and the growth boundary of the deciduous acacias was characterized by thin parenchyma bands. The mean annual diameter increment ranged from 3.6 to 5.0 mm. Acacia senegal and Acacia seyal showed more enhanced growth than Acacia tortilis and B. aegyptiaca. High positive correlations were found between the tree-ring width chronologies and precipitation data, and all species showed similar response to external climate forcing, which supports the formation of one tree-ring per year. Strong declines in tree-ring width correlated remarkably well with past El Niño Southern Oscillation (ENSO) events and drought/famine periods in Ethiopia. Spectral analysis of the master tree-ring chronology indicated occurrences of periodic drought events, which fall within the spectral peak equivalent to 2–8 years. Our results proved the strong linkage between tree-ring chronologies and climate, which sheds light on the potential of dendrochronological studies developing in Ethiopia. The outcome of this study has important implications for paleoclimatic reconstructions and in restoration of degraded lands.     

Effects of El Niño drought on seedling dynamics in a seasonally dry tropical forest in Northern Thailand

As El Niño is predicted to become stronger and more frequent in the future, it is crucial to understand how El Niño-induced droughts will affect tropical forests. Although many studies have focused on tropical rainforests, there is a paucity of studies on seasonally dry tropical forests (SDTFs), particularly in Asia, and few studies have focused on seedling dynamics, which are expected to be strongly affected by drought. Seedlings in SDTFs are generally more drought-tolerant than those in the rainforests, and the effects of El Niño-induced droughts may differ between SDTF and tropical rainforests. In this study, we explored the impact of El Niño-induced drought at an SDTF in northern Thailand by monitoring the seedling dynamics at monthly intervals for 7 years, including a period of strong El Niño. The effects were compared between two forest types in an SDTF: a deciduous dipterocarp forest (DDF), dominated by deciduous species, and an adjacent lower montane forest (LMF) with more evergreen species. El Niño-induced drought increased seedling mortality in both the forest types. The effect of drought was stronger in evergreen than in the deciduous species, resulting in higher mortality in the LMF during El Niño. However, El Niño increased seedling recruitment only in the DDF, mainly because of the massive recruitment of the deciduous oak, Quercus brandisiana (Fagaceae), which compensated for the mortality of seedlings in the DDF. As a result, El Niño increased seedling density in the DDF and decreased it in the LMF. This is the first long-term study to identify the differences in the impacts of El Niño on seedlings between the two forest types, and two leaf habits, evergreen and deciduous, in Southeast Asia. Our findings suggest that future climate change may alter the species composition and spatial distribution of seedlings in Asian SDTFs.     

Climate/growth relations and teleconnections for a <Emphasis Type="Italic">Hymenaea courbaril</Emphasis> (Leguminosae) population inhabiting the dry forest on karst

Key message

Both water availability and temperature modulate the growth of Hymenaea courbaril on karst in Central Brazil. There is evidence of teleconnections between South Atlantic SST and tree growth.

Abstract

Tropical dry forests have low annual precipitation and long dry seasons. Water availability, the main restrictive growth factor, becomes more pronounced in the shallow and highly porous soil of karst regions. Understanding how climate regulates tree growth in stressful environments is essential for predicting climate change impacts on trees. The aim of this study was to build a tree-ring chronology of Hymenaea courbaril growing in a karst dry forest and evaluate how local climate and teleconnections modulate its growth. To accomplish this, increment cores of 19 individuals were sampled in Terra Ronca State Park located in Goiás State, Central Brazil. After surface polishing, tree rings were identified, measured, dated, and a tree-ring chronology was built with 17 individuals. The chronology was correlated with local and regional climate data (temperature, precipitation, air humidity). We also tested teleconnections with sea surface temperature (SST) of the Equatorial Pacific and South Atlantic. Results show that air humidity, precipitation amount, and its distribution during the transition period between dry and wet seasons positively regulate this species growth. On the other hand, growth is negatively correlated with temperature during the middle of the previous year’s dry season. Additionally, growth is negatively correlated with SST of the Southern Atlantic, but not with Equatorial Pacific. These relationships between climate and growth indicate that predicted increases in regional temperature and decreases in water availability may limit the growth of H. courbaril in karst dry forests.

     

Teleconnection between tree growth in the Amazonian floodplains and the El Niño–Southern Oscillation effect

There is a limited knowledge about the El Niño–Southern Oscillation (ENSO) effects on the Amazon basin, the world's largest tropical rain forest and a major factor in the global carbon cycle. Seasonal precipitation in the Andean watershed annually causes a several month‐long inundation of the floodplains along the Amazon River that induces the formation of annual rings in trees of the flooded forests. Radial growth of trees is mainly restricted to the nonflooded period and thus the ring width corresponds to its duration. This allows the construction of a tree‐ring chronology of the long‐living hardwood species Piranhea trifoliata Baill. (Euphorbiaceae). El Niño causes anomalously low precipitation in the catchment that results in a significantly lower water discharge of the Amazon River and consequently in an extension of the vegetation period. In those years tree rings are significantly wider. Thus the tree‐ring record can be considered as a robust indicator reflecting the mean climate conditions of the whole Western Amazon basin. We present a more than 200‐year long chronology, which is the first ENSO‐sensitive dendroclimatic proxy of the Amazon basin and permits the dating of preinstrumental El Niño events. Time series analyses of our data indicate that during the last two centuries the severity of El Niño increased significantly.     

Legacies of La Niña: North American monsoon can rescue trees from winter drought

While we often assume tree growth–climate relationships are time‐invariant, impacts of climate phenomena such as the El Niño Southern Oscillation (ENSO) and the North American Monsoon (NAM) may challenge this assumption. To test this assumption, we grouped ring widths (1900‐present) in three southwestern US conifers into La Niña periods (LNP) and other years (OY). The 4 years following each La Niña year are included in LNP, and despite 1–2 year growth declines, compensatory adjustments in tree growth responses result in essentially equal mean growth in LNP and OY, as average growth exceeds OY means 2–4 years after La Niña events. We found this arises because growth responses in the two periods are not interchangeable: Due to differences in growth–climate sensitivities and climatic memory, parameters representing LNP growth fail to predict OY growth and vice versa (decreases in R² up to 0.63; lowest R² = 0.06). Temporal relationships between growth and antecedent climate (memory) show warmer springs and longer growing seasons negatively impact growth following dry La Niña winters, but that NAM moisture can rescue trees after these events. Increased importance of monsoonal precipitation during LNP is key, as the largest La Niña‐related precipitation deficits and monsoonal precipitation contributions both occur in the southern part of the region. Decreases in first order autocorrelation during LNP were largest in the heart of the monsoon region, reflecting both the greatest initial growth declines and the largest recovery. Understanding the unique climatic controls on growth in Southwest conifers requires consideration of both the influences and interactions of drought, ENSO, and NAM, each of which is likely to change with continued warming. While plasticity of growth sensitivity and memory has allowed relatively quick recovery in the tree‐ring record, recent widespread mortality events suggest conditions may soon exceed the capacity for adjustment in current populations.     

Herbivory and plant growth rate determine the success of El Niño Southern Oscillation-driven tree establishment in semiarid South America

While climatic extremes are predicted to increase with global warming, we know little about the effect of climatic variability on biome distribution. Here, we show that rainy El Niño Southern Oscillation (ENSO) events can enhance tree recruitment in the arid and semiarid ecosystems of north‐central Chile and northwest Peru. Tree‐ring studies in natural populations revealed that rainy El Niño episodes have triggered forest regeneration in Peru. Field experiments indicate that tree seedling recruitment in Chile is much less successful than in Peru due mostly to larger mortality caused by herbivores. The dramatic impact of herbivores in Chile was derived from the combined result of slower plant growth and the presence of exotic herbivores (European rabbits and hares). The interplay of herbivory and climatic effects we demonstrated implies that rainy ENSO events may represent ‘windows of opportunity’ for forest recovery if herbivore pressure is minimized at the right moment.     

Adjusting xylem anatomy and growth to inter-annual climate variability in two Fabaceae species (Centrolobium microchaete,Cenostigma pluviosum) from Bolivian dry tropical forests

Climate-growth relationships are strong in seasonally dry tropical forests (SDTFs). To better understand the ecological processes controlling these relationships we need to assess the long-term responses of wood anatomy and radial growth to year-to-year climate variability. We assessed how wood-anatomical traits (mean vessel area –MVA– and vessel density –VD–, percentage of conductive area –CA–, xylem-specific estimated hydraulic conductivity –Ks–) and growth responded to local climate (mean temperature, total precipitation, estimated moisture) variability and teleconnections (Pacific Decadal Oscillation) between 1970 and 2011 in two Fabaceae tree species (Centrolobium microchaete and Cenostigma pluviosum) coexisting in a Bolivian SDTF. We found that C. microchaete produced wider vessels and was more responsive to both local climate conditions and teleconnections than C. pluviosum. In C. microchaete VD positively responded to average temperature in the late-wet season and in the previous dry season, and CA and Ks were higher in years with warmer wet and previous early-dry seasons, as well as in years with higher PDO values. These responses were independent from ring-width variability only for C. microchaete. For C. pluviosum, vessel chronologies were more responsive to local temperature variability, and only MVA and CA positively and negatively responded to moisture in the early-dry and the previous dry seasons, respectively. Our results show that wood hydraulic structure in SDTFs is responsive to climate fluctuations. The combined study of ring width and wood anatomy allows having a more complete picture of the influence of climate on growth, particularly in species as C. microchaete which show low collinearity of tree-ring width and wood plasticity in response to climate variability.     

Climate‐growth analysis for a Mexican dry forest tree shows strong impact of sea surface temperatures and predicts future growth declines

Tropical forests will experience relatively large changes in temperature and rainfall towards the end of this century. Little is known about how tropical trees will respond to these changes. We used tree rings to establish climate‐growth relations of a pioneer tree, Mimosa acantholoba, occurring in tropical dry secondary forests in southern Mexico. The role of large‐scale climatic drivers in determining interannual growth variation was studied by correlating growth to sea surface temperature anomalies (SSTA) of the Atlantic and Pacific Oceans, including the El Niño‐Southern Oscillation (ENSO). Annual growth varied eightfold over 1970–2007, and was correlated with wet season rainfall (r=0.75). Temperature, cloud cover and solar variation did not affect growth, although these climate variables correlated with growth due to their relations with rainfall. Strong positive correlations between growth and SSTA occurred in the North tropical Atlantic during the first half of the year, and in the Pacific during the second half of the year. The Pacific influence corresponded closely to ENSO‐like influences with negative effects of high SSTA in the eastern Pacific Niño3.4 region on growth due to decreases in rainfall. During El Niño years growth was reduced by 37%. We estimated how growth would be affected by the predicted trend of decreasing rainfall in Central America towards the end of this century. Using rainfall predictions of two sets of climate models, we estimated that growth at the end of this century will be reduced by 12% under a medium (A1B) and 21% under a high (A2) emission scenario. These results suggest that climate change may have repercussions for the carbon sequestration capacity of tropical dry forests in the region.     

Preliminary Evidence of the Importance of ENSO in Modifying Food Availability for White‐tailed Deer in a Mexican Tropical Dry Forest1

The influence of El Niño/Southern Oscillation (ENSO) on rainfall and its possible effect on availability of food for white‐tailed deer (Odocoileus virginianus) in a tropical dry forest in the Pacific coast of Mexico was studied. From 1977 to 2003 there were three significant El Niño and La Niña events. During El Niño years rainfall decreased during the wet season ( June to October) and increased during the dry season (November to May), with the opposite effect during La Niña years. Plant diversity was monitored in permanent plots during the wet and dry seasons of 1989–1993. The results provide evidence that ENSO events affect deer food availability, particularly in the dry season.     

Coral reef resilience to thermal stress in the Eastern Tropical Pacific

Coral reefs worldwide are threatened by thermal stress caused by climate change. Especially devastating periods of coral loss frequently occur during El Niño‐Southern Oscillation (ENSO) events originating in the Eastern Tropical Pacific (ETP). El Niño‐induced thermal stress is considered the primary threat to ETP coral reefs. An increase in the frequency and intensity of ENSO events predicted in the coming decades threatens a pan‐tropical collapse of coral reefs. During the 1982–1983 El Niño, most reefs in the Galapagos Islands collapsed, and many more in the region were decimated by massive coral bleaching and mortality. However, after repeated thermal stress disturbances, such as those caused by the 1997–1998 El Niño, ETP corals reefs have demonstrated regional persistence and resiliency. Using a 44 year dataset (1970–2014) of live coral cover from the ETP, we assess whether ETP reefs exhibit the same decline as seen globally for other reefs. Also, we compare the ETP live coral cover rate of change with data from the maximum Degree Heating Weeks experienced by these reefs to assess the role of thermal stress on coral reef survival. We find that during the period 1970–2014, ETP coral cover exhibited temporary reductions following major ENSO events, but no overall decline. Further, we find that ETP reef recovery patterns allow coral to persist under these El Niño‐stressed conditions, often recovering from these events in 10–15 years. Accumulative heat stress explains 31% of the overall annual rate of change of living coral cover in the ETP. This suggests that ETP coral reefs have adapted to thermal extremes to date, and may have the ability to adapt to near‐term future climate‐change thermal anomalies. These findings for ETP reef resilience may provide general insights for the future of coral reef survival and recovery elsewhere under intensifying El Niño scenarios.     

Seasonal patterns in rainforest litterfall: Detecting endogenous and environmental influences from long‐term sampling

Tropical rainforests play an important role in the storage and cycling of global terrestrial carbon. In the carbon cycle, net primary productivity of forests is linked to soil respiration through the production and decomposition of forest litter. Climate seasonality appears to influence the production of litter although there is considerable variability within and across forests that makes accurate estimates challenging. We explored the effects of climate seasonality on litterfall dynamics in a lowland humid rainforest over a 7‐year period from 2007 to 2013, including an El Niño/La Niña cycle in 2010/2011. Litterfall was sampled fortnightly in 24 traps of 0.50 m diameter within a 1‐ha forest plot. Total mean litterfall was 10.48 ± 1.32 (±SD, dry weight) Mg ha^?1 year^?1 and seasonal in distribution. The different components of litterfall were divided into L_Leaf (63.5%), L_Wood (27.7%) and L_{FF[flowers & fruit]} (8.8%), which all demonstrated seasonal dynamics. Peak falls in L_Leaf and L_Wood were highly predictable, coinciding with maximum daily temperatures and 1 and 2 months prior to maximum monthly rainfall. The El Niño/La Niña cycle coincided with elevated local winter temperatures and peak falls of L_Leaf and L_Wood. Importantly, we establish how sampling length and generalized additive models eliminate the requirement for extensive within‐site sampling when the intention is to describe dynamics in litterfall patterns. Further, a greater understanding of seasonal cycles in litterfall allows us to distinguish between endogenous controls and environmental factors, such as El Niño events, which may have significant impacts on biochemical cycles.     

Effects of El Niño Southern Oscillation on avian breeding phenology

Aim

Climate oscillations are known to influence the reproductive phenology of birds. Here, we quantify the effects of cyclic climatic variation, specifically El Niño Southern Oscillation (ENSO), on birds that breed opportunistically. We aim to show how inter‐decadal climate fluctuations influence opportunistic breeding. This knowledge is essential for tracking the phenological responses of birds to climate change.

Location

Temperate and arid Australia.

Methods

We assessed variation in egg‐laying (start, peak, conclusion, length) during the three phases of ENSO (El Niño, La Niña and Neutral) for 64 temperate and 15 arid region species using ~80,000 observations. Linear mixed‐effect models and analysis of variance were used to (1) determine if, on average within each region, egg‐laying dates differed significantly among species between Neutral‐El Niño and Neutral‐La Niña phases, and (2) assess how La Niña and El Niño episodes influence egg‐laying in birds which breed early in the year.

Results

During La Niña phases, which are characterized by mild/wet conditions, most bird species in the temperate and arid regions exhibited longer egg‐laying periods relative to Neutral phases. However, there was substantial variation across species. This effect was strongly seasonal; species breeding in spring experienced the greatest increases in egg‐laying periods during La Niña. Further, we found only small differences in peak egg‐laying dates during Neutral and La Niña in the arid region; suggesting that hot temperatures may constrain breeding regardless of rainfall. The effects of El Niño on breeding phenology were not consistent in the temperate and arid regions and may be confounded by highly mobile species opportunistically moving and breeding with localized rainfall during dry periods.

Main conclusions

In both arid and temperate regions, increased rainfall associated with La Niña phases positively influences avian breeding, and likely recruitment. However, dry El Niño phases may not have the dramatic impacts on breeding phenology that are commonly assumed.

     

Population dynamics of the tropical bivalve <Emphasis Type="Italic">Cardita affinis</Emphasis> from Málaga Bay,Colombian Pacific related to La Niña 1999–2000

The population dynamics of the “cholga” Cardita affinis (Sowerby 1833) from Málaga Bay, Colombia, was studied from December 1999 to February 2002, which included the 1999–2000 La Niña event (LN) and the post-LN period 2001–2002. This climatic deviation caused precipitation anomalies in Málaga Bay. Salinity, precipitation, and sea surface temperature anomalies were highly correlated with the bivalve’s body mass cycle. Irregular spawning events were observed during LN by comparison with the regular period. Individual growth and mortality were found significantly higher during LN than during the post-LN period while longevity was almost twofold lower during LN. Increased mortality was probably related to environmental stress. Individual production and productivity were higher during LN, although the annual biomass was lower than during the post-LN period. These results may be related to higher food availability during LN, which agrees well with the results on growth performance. The observed changes provide a base line for future studies regarding effects of El Niño/LN events on population dynamics of tropical bivalves.