Van Hall Larenstein University of Applied Sciences
Recent publications
Fish assemblages of different types of artificial reefs can differ greatly in abundance, biomass and composition, with some reef types harboring over five times more herbivores than others. It is assumed that higher herbivorous fish abundance results in a higher grazing intensity, affecting the benthic community by means of enhanced coral recruitment, survival and growth. Territorial fish species might affect this process by chasing away other fish, especially herbivores. In this study we compared the fish assemblage, territorial behavior and grazing intensity by fish on two artificial reef types: reef balls and layered cakes, differing greatly in their fish assemblage during early colonization. In addition, the effect of artificial reef type on benthic development and coral recruitment, survival and growth, was investigated. Although layered cakes initially harbored higher herbivorous fish biomass, this effect was lost during consecutive monitoring events. This seems to be the result of the higher territorial fish abundance around the layered cakes where almost four times more chasing behavior was recorded compared to the reef balls. This resulted in a more than five times lower fish grazing intensity compared to the reef-ball plots. Although macroalgae were effectively controlled at both reefs, the grazing intensity did not differ enough to cause large enough structural changes in benthic cover for higher coral recruitment, survival or growth. The high turf algae cover, combined with increasing crustose coralline algae and sponge cover likely explained reduced coral development. We recommend further research on how to achieve higher grazing rates for improved coral development on artificial reefs, for example by facilitating invertebrate herbivores.
The 1983-1984 die-off of the long-spined sea urchin Diadema antillarum stands out as a catastrophic marine event because of its detrimental effects on Caribbean coral reefs. Without the grazing activities of this key herbivore, turf and macroalgae became the dominant benthic group, inhibiting coral recruitment and compromising coral reef recovery from other disturbances. In the decades that followed, recovery of D. antillarum populations was slow to non-existent. In late January 2022, a new mass mortality of D. antillarum was first observed in the U.S. Virgin Islands. We documented the spread and extent of this new die-off using an online survey. Infected individuals were closely monitored in the lab to record signs of illness, while a large population on Saba, Dutch Caribbean, was surveyed weekly before and during mortality to determine the lethality of this event. Within four months the die-off was distributed over 1,300 km from north to south and 2,500 km east to west. Whereas the 1983-1984 die-off advanced mostly with the currents, the 2022 event has appeared far more quickly in geographically distant areas. First die-off observations in each jurisdiction were often close to harbor areas, which, together with their rapid appearance, suggests that anthropogenic factors may have contributed to the spread of the causative agent. The signs of illness in sick D. antillarum were very similar to those recorded during the 1983-1984 die-off: lack of tube feet control, slow spine reaction followed by their loss, and necrosis of the epidermis were observed in both lab and wild urchins. Affected populations succumbed fast; within a month of the first signs of illness, a closely monitored population at Saba, Dutch Caribbean, had decreased from 4.05 individuals per m 2 to 0.05 individuals per m 2. Lethality can therefore be as high as 99%. The full extent of the 2022 D. antillarum die-off Frontiers in Marine Science event is not currently known. The slower spread in the summer of 2022 might indicate that the die-off is coming to a (temporary) standstill. If this is the case, some populations will remain unaffected and potentially supply larvae to downstream areas and augment natural recovery processes. In addition, several D. antillarum rehabilitation approaches have been developed in the past decade and some are ready for large scale implementation. However, active conservation and restoration should not distract from the primary goal of identifying a cause and, if possible, implementing actions to decrease the likelihood of future D. antillarum die-off events.
For large herbivores inhabiting arid/semi-arid environments, water can be a limiting resource affecting their distribution and abundance for periods when water requirements are not met via forage. The Cyprus mouflon (Ovis gmelini ophion) is such a species, which is endemic to the mountain habitats of Cyprus. Recognizing water scarcity to be a major pressure to the mouflon, and with global warming projected to intensify hot and dry periods in the region, the Game and Fauna Service has been maintaining a network of locally designed watering troughs in Pafos Forest—the mouflon’s stronghold—since 1997. This study describes the mouflon’s use of the water troughs and examines whether visitation rates differed at the daily or weekly scale in response to environmental, climatic or anthropogenic parameters. Using camera traps, ten troughs were monitored from September 2017 to March 2018 (1,065 days; range 29–164 days per trough). Mouflon were detected at seven troughs (mean herd size 1.5 ± 1.2) during 373 independent detections (≥30 min interval between photographs), with visits peaking during late morning and midday hours. Generalized mixed-effect models showed mouflon visiting water troughs more frequently during hotter days, regardless of recent precipitation. Visits were also more frequent at water troughs located close to tar roads. Moreover, there was no evidence of mouflon avoiding water troughs used by predators (red foxes, feral dogs) at either daily or weekly scale, or during hunting days. The study supports the value of artificial water troughs for mediating, partially at least, the effects of climate change on mountain ungulates such as the Cyprus mouflon. Additional studies are proposed that will examine both mouflon drinking patterns across all seasons and ways of improving the effectiveness of the current water trough grid.
Reconnecting fragmented habitats by planting forest corridors is becoming necessary to support isolated populations of threatened callitrichid primates (marmosets and tamarins) in Brazil. Tamarins frequently use tree holes as sleeping sites, but young forests do not provide these; artificial nestboxes offer a potential solution until trees in the corridors reach maturity. However, how effective such nestboxes are in attracting callitrichids and providing safety from predators is unquantified. We tested three features that might be important in the design of callitrichid nestboxes: internal shelves or entrance tunnels, to prevent predators from reaching tamarins in the boxes, and a second exit point to provide an escape route. Seven groups of zoo-housed pied tamarins (Saguinus bicolor) were given a choice between an unmodified nestbox with a single entrance and a box with one of the three test features. Each group was tested 12-13 times under each choice condition. Tamarins chose to sleep in boxes with tunnels (overall probability of selection = 0.72) and shelves (probability of selection = 0.53) in preference to unmodified boxes, but rarely opted for boxes with two entrance holes (probability = 0.3). A generalised linear mixed model showed that these differences were statistically significant (F = 15.6, df = 2, P < 0.0001). Tamarins spent more time in the hour before retiring in nestboxes with tunnels or shelves than in unmodified boxes, but less time in boxes with two entrances (F = 11.84, df = 2, 53.05, P < 0.0001). They also retired latest and rose earliest if they used boxes with two entrances. To test their susceptibility to predation, boxes of each design were baited and offered to coatis (Nasua nasua), macaques (Macaca nigra), and capuchins (Cebus capucinus and Sapajus xanthosternos). Four trials were conducted for each box type with each species. None managed to obtain bait from boxes with tunnels, but all rapidly retrieved the bait from boxes with two entrances. Pied tamarins therefore preferred nestbox designs (tunnels) offering the most protection from predators.
Residue analysis is an established area of expertise focused on detecting traces of substances found on the surface of objects. It is routinely employed in forensic casework and increasingly incorporated into archaeological investigations. In archaeology, sampling and data interpretation sometimes lacked strict standards, resulting in incorrect residue classifications. In particular, molecular signals of salts of fatty acids identified by FTIR have been, at times, interpreted as evidence for adipocere, a substance formed as a consequence of adipose tissues' degradation. This article reviews and discusses the possibilities and limitations of the analytical protocols used in residue analysis in archaeology. The focus is on three main points: (1) reviewing the decomposition processes and the chemical components of adipocere; (2) highlighting potential misidentifications of adipocere while, at the same time, addressing issues related to residue preservation and contamination; and (3) proposing new research avenues to identify adipocere on archaeological objects.
A tailor-made training (TMT) assembled by both Politeknik Pertanian Negeri Kupang (Politani Kupang) and Van Hall Larenstein of Applied Sciences, Netherlands (VHL) was conducted from the 9th to 13th November 2020. This training focused on the importance of establishing, maintaining, and broadening partnerships for a better institutional development. As many as 19 participants were invited to attend the training and were assigned into five groups based on the five prioritized commodities the institution was planning to expand further, which were: meat/beef, coffee, honey, shallot, and catfish. The training was organized through both online and offline methods. The online method implemented both an asynchronous pathway, in which all the materials were posted through Google Classroom and Whatsapp group, and an asynchronous pathway, in which the teaching-learning process was organized via ZOOM. For the in-person method, the participants were taken to a field trip. By the end of the training, all the participants had understood the concepts of partnerships and their importance, how to construct and differ between a Memorandum of Understanding (MoU) and a Contract, how to achieve cultural awareness for a fruitful partnership, and how to outline a business plan and demonstrate a 3-minute pitch to be implemented on potential business partners during the field trip.
This study evaluated the effects of dietary supplementation of thyme (Thymus vulgaris) essential oil (TVO) on growth performance, digestive enzymes, biochemical parameters, hematological indices, liver enzymes, and pathogen resistance in common carp (Cyprinus carpio). Triplicate groups of fish (15.36 ± 0.10 g) were fed daily with diets supplemented with TVO at 0, 0.5, 1, and 2 percent for 60 days, then challenged with Aeromonas hydrophila. The results determined that supplementation of thyme resulted in significantly higher final body weights (FBW) and lower feed conversion ratios (FCR). Furthermore, no mortality was observed in the thyme-supplemented treatments. Regression analysis showed that fish growth parameters were polynomially-related to dietary TVO levels. The optimum dietary TVO level, based upon the varied growth parameters, was 1.344 to 1.436 %. Digestive enzymes activity, including amylase and protease, significantly increased in fish fed the supplemented diets. The thyme supplemented diets also significantly increased the biochemical parameters, including total protein, albumin, and acid phosphatase (ACP), compared to the control group. We also observed significant increases in hematological indices, including red blood cells (RBC), white blood cells (WBC), hematocrit (Hct), and hemoglobin (Hb) in common carp fed diets containing thyme oil (P < 0.05). Liver enzymes activity including Alanine Aminotransferase (ALT), Alkaline Phosphatase (ALP), and Aspartate Aminotransferase (AST) were also reduced (P < 0.05). Immune parameters, including total protein and total immunoglobulin (total Ig) levels, alternative complement pathway hemolytic (ACH50), lysozyme, protease, and ALP in the skin mucus; and lysozyme, total Ig, and ACH50 in the intestine were higher (P < 0.05) in TVO-supplemented fish . Catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), and glutathione peroxidase (GPx) in the liver were also elevated (P < 0.05) in TVO administered groups. Lastly, thyme supplementation resulted in higher survival rates after the A. hydrophila challenge compared to the control (P < 0.05). In conclusion, dietary inclusion of thyme oil (1 and 2 %) effectively improved fish growth, immune systems, and resistance to A. hydrophila.
The long spined sea urchin Diadema antillarum was an abundant grazer on Caribbean coral reefs, until 1983–1984, when densities were reduced by ~98% during a region wide die-off. Since then, there has been very little natural recovery of the species and interest is growing in applying aquaculture as a tool for population enhancement. In this study we optimized a new shaker bottle cultivation method for D. antillarum. The method was tested in a series of experiments by culturing D. antillarum from egg to juvenile in the Netherlands as well as the USA. Larvae were cultured in standard 1-L glass reagent bottles, suspended by gentle constant movement on an orbital shaking table and fed with either the microalgae Rhodomonas lens or Rhodomonas salina. Effects on larval growth and survival were evaluated for different microalgal feeding concentrations, larval densities, and culture temperatures. Larval density and growth were measured twice a week over a period of up to 56 days. Larvae grew significantly faster on a higher feeding concentration up to 90,000 Rhodomonas sp. cells mL⁻¹, twice weekly, compared to 30,000 and 60,000 cells mL⁻¹. A density of 1 larvae mL⁻¹ resulted in the highest body size and survival compared to densities of 2 or 4 larvae mL⁻¹. Overall survival from larva to settled juvenile urchin increased from 8 to 10% settlement to 32–33% when the initial density was lowered further from 1.2 to 0.4 larvae mL⁻¹. Growth, survival, competency and settlement did not differ between larval cultures kept at 25 °C or 28 °C. We believe that this novel method for culturing D. antillarum larvae, once scaled-up and validated to pilot scale, could provide juveniles for restocking of urchin-depleted reefs that suffer from algae overgrowth.
The risk for development of non-communicable diseases (NCD’s) can be predicted by somatic or mental symptoms and dietary alterations aimed at improvement of those symptoms could potentially delay development of NCD’s. The goal of this study was to identify whether self-initiated dietary changes could improve mental and somatic symptoms in relatively healthy individuals. Participants (n=494) recruited from the Dutch population filled out weekly questionnaires on dietary intake, somatic and mental symptoms and physical activity for four weeks. There was a significant reduction in mental and somatic symptoms, body weight, and waist circumference at four weeks, whereas physical activity remained unchanged. Five dietary patterns were identified by principal component analysis labelled “Processed foods”, “Animal source foods”, “Wheel of Five”, “Traditional Dutch”, and “Party”. Reduction in mental symptoms was correlated to increased physical activity and reduced intake of Processed foods. Reduction in somatic symptoms was related to body weight loss and changes in dietary intake, less Processed foods, more Wheel of Five foods, reduced caloric intake, lower carbohydrate and higher fat intake. Other observed dietary changes were not correlated to changes in symptoms. In conclusion this research showed that a self-initiated dietary change can lead to a significant reduction of mental and somatic symptoms.
New approach methodologies predicting human cardiotoxicity are of interest to support or even replace in vivo-based drug safety testing. The present study presents an in vitro–in silico approach to predict the effect of inter-individual and inter-ethnic kinetic variations in the cardiotoxicity of R- and S-methadone in the Caucasian and the Chinese population. In vitro cardiotoxicity data, and metabolic data obtained from two approaches, using either individual human liver microsomes or recombinant cytochrome P450 enzymes (rCYPs), were integrated with physiologically based kinetic (PBK) models and Monte Carlo simulations to predict inter-individual and inter-ethnic variations in methadone-induced cardiotoxicity. Chemical specific adjustment factors were defined and used to derive dose–response curves for the sensitive individuals. Our simulations indicated that Chinese are more sensitive towards methadone-induced cardiotoxicity with Margin of Safety values being generally two-fold lower than those for Caucasians for both methadone enantiomers. Individual PBK models using microsomes and PBK models using rCYPs combined with Monte Carlo simulations predicted similar inter-individual and inter-ethnic variations in methadone-induced cardiotoxicity. The present study illustrates how inter-individual and inter-ethnic variations in cardiotoxicity can be predicted by combining in vitro toxicity and metabolic data, PBK modelling and Monte Carlo simulations. The novel methodology can be used to enhance cardiac safety evaluations and risk assessment of chemicals.
Forensic methods to independently trace timber origin are essential to combat illegal timber trade. Tracing product origin by analysing their multi-element composition has been successfully applied in several commodities, but its potential for timber is not yet known. To evaluate this potential the drivers of wood multi-elemental composition need to be studied. Here we report on the first study relating wood multi-elemental composition of forest trees to soil chemical and physical properties. We studied the reactive soil element pools and the multi-elemental composition in sapwood and heartwood for 37 Azobé (Lophira alata) trees at two forest sites in Cameroon. A total of 46 elements were measured using ICP-MS. We also measured three potential drivers of soil and wood elemental composition: clay content, soil organic matter and pH. We tested associations between soil and wood using multiple regressions and multivariate analyses (Mantel test, db-RDA). Finally, we performed a Random Forest analysis of heartwood elemental composition to check site assignment accuracy. We found elemental compositions of soil, sapwood and heartwood to be significantly associated. Soil clay content and organic matter positively influenced individual element concentrations (for 13 and 9 elements out of 46 respectively) as well as the multi-elemental composition in wood. However, associations between wood and topsoil elemental concentrations were only significant for one element. We found close associations between element concentrations and composition in sapwood and heartwood. Lastly, the Random Forest assignment success was 97.3 %. Our findings indicate that wood elemental composition is associated with that in the topsoil and its variation is related to soil clay and organic matter content. These associations suggests that the multi-elemental composition of wood can yield chemical fingerprints obtained from sites that differ in soil properties. This finding in addition to the high assignment accuracy shows potential of multi-element analysis for tracing wood origin.
The quantification and identification of new plasmid-acquiring bacteria in representative mating conditions is critical to characterize the risk of horizontal gene transfer in the environment. This study aimed to quantify conjugation events resulting from manure application to soils and identify the transconjugants resulting from these events. Conjugation was quantified at multiple time points by plating and flow cytometry, and the transconjugants were recovered by fluorescence-activated cell sorting and identified by 16S rRNA sequencing. Overall, transconjugants were only observed within the first 4 days after manure application and at values close to the detection limits of this experimental system (1.00-2.49 log CFU/g of manured soil, ranging between 10-5 and 10-4 transconjugants-to-donor ratios). In the pool of recovered transconjugants, we found amplicon sequence variants (ASVs) of genera whose origin was traced to soils (Bacillus and Nocardioides) and manure (Comamonas and Rahnella). This work showed that gene transfer from fecal to soil bacteria occurred despite the less-than-optimal conditions faced by manure bacteria when transferred to soils, but these events were rare, mainly happened shortly after manure application, and the plasmid did not colonize the soil community. This study provides important information to determine the risks of AMR spread via manure application.
The EU Maritime Spatial Planning Directive (MSPD) requires the member states (MS) to pursue Blue Growth while ensuring good environmental status (GES) of sea areas. An ecosystem-based approach (EBA) should be used for the integration of the aims. However, the MSPD does not specify how the MS should arrange their MSP governance, which has led to a variety of governance arrangements and solutions in addressing the aims. We analysed the implementation of the MSPD in Finland, to identify conditions that may enable or constrain the integration of Blue Growth and GES in the framework of EBA. MSP in Finland is an expert-driven regionalized approach with a legally non-binding status. The results suggest that this MSP framework supports the implementation of EBA in MSP. Yet, unpredictability induced by the non-binding status of MSP, ambiguity of the aims of MSP and of the concept of EBA, and the need to pursue economic viability in the coastal municipalities may threaten the consistency of MSP in both spatial and temporal terms. Developing MSP towards a future-oriented adaptive and collaborative approach striving for social learning could improve the legitimacy of MSP and its capacity to combine Blue Growth and GES. The analysis indicates, that in the delivery of successful MSP adhering to the principles of EBA should permeate all levels of governance. The study turns attention to the legal status of MSP as a binding or non-binding planning instrument and the role the legal status plays in facilitating or constraining predictability and adaptability required in MSP.
The massive die-off of the sea urchin Diadema antillarum in 1983–1984 is one the main reasons for low coral recruitment and little coral recovery in the Caribbean. As the natural recovery of D. antillarum is slow to non-existent, multiple restoration studies have been attempted. There are currently three different approaches to obtain individuals for restocking: the translocation of wild-collected juveniles or adults, lab-reared juveniles cultured from wild-collected settlers, or lab-reared juveniles cultured from gametes. All three methods are costly and can only be applied on a relatively small scale. We here propose a fourth, new, approach, which we term assisted natural recovery (ANR) of D. antillarum populations. ANR, a concept already applied in terrestrial restoration to restore forests and grasslands, can accelerate succession by removing barriers to natural recovery. In this study, performed on the Dutch Caribbean island of Saba, suitable settlement substrate was provided in the form of bio ball streamers that were attached to the reef shortly before the settlement season. At the end of the experiment, reefs with streamers had significantly higher D. antillarum recruit densities than control reefs without additional settlement substrate, indicating that the lack of settlement substrate is an important factor constraining natural recovery. However, D. antillarum recruit abundance was low compared to the measured settlement rates, possibly due to low post-settlement survival. The size distribution of recruits showed that recruits almost never became larger than 20 mm, which is likely due to predation. We conclude that, next to low settlement availability, low post-settlement survival and high predation on recruits also constrain the natural recovery of D. antillarum populations on Saba. To improve the survival of settlers till adults, we propose to 1) reduce predation on settlers by using bio balls or other substrates that can provide shelter to larger individuals and 2) optimize the reef habitat by removing macroalgae, either manually or by facilitating other herbivores. To improve the survival of recruits, we suggest to 1) choose sites with a known lower predation density or 2) protect recruits with a corral around the reef underneath the streamers. The combination of these measures could improve prospects for ANR, and we expect this new approach can contribute to the recovery of D. antillarum populations in the future.
Nature-based strategies, such as wave attenuation by tidal marshes, are increasingly proposed as a complement to mitigate the risks of failure of engineered flood defense structures such as levees. However, recent analysis of historic coastal storms revealed smaller dike breach dimensions if there were natural, high tidal marshes in front of the dikes. Since tidal marshes naturally only experience weak flow velocities (~0-0.3 ms-1 during normal spring tides), we lack direct observations on the stability of tidal marsh sediments and vegetation under extreme flow velocities (order of several ms-1) as may occur when a dike behind a marsh breaches. As a first approximation, the stability of a tidal marsh sediment bed and winter-state vegetation under high flow velocities were tested in a flume. Marsh monoliths were excavated from Phragmites australis marshes in front of a dike along the Scheldt estuary (Dutch-Belgian border area) and installed in a 10 m long flume test section. Both sediment bed and vegetation responses were quantified over 6 experimental runs under high flow velocities up to 1.75 ms-1 and water depth up to 0.35 m for 2 hours. These tests showed that even after a cumulative 12 hours exposure to high flow velocities, erosion was limited to as little as a few millimeters. Manual removal of the aboveground vegetation did not enhance the erosion either. Present findings may be related to the strongly consolidated, clay- and silt-rich sediment and P. australis root system in this experiment. During the flow exposure, the P. australis stems were strongly bent by the water flow, but the majority of all shoots recovered rapidly when the flow had stopped. Although present results may not be blindly extrapolated to all other marsh types, they do provide a strong first indication that marshes can remain stable under high flow conditions, and confirm the potential of well-developed tidal marshes as a valuable extra natural barrier reducing flood discharges towards the hinterland, following a dike breach. These outcomes promote the consideration to implement tidal marshes as part of the overall flood defense and to rethink dike strengthening in the future.
Water availability is the major driver of tropical forest structure and dynamics. Most research has focused on the impacts of climatic water availability, whereas remarkably little is known about the influence of water table depth and excess soil water on forest processes. Nevertheless, given that plants take up water from the soil, the impacts of climatic water supply on plants are likely to be modulated by soil water conditions. Lowland Amazonian forests. 1971–2019. We used 344 long‐term inventory plots distributed across Amazonia to analyse the effects of long‐term climatic and edaphic water supply on forest functioning. We modelled forest structure and dynamics as a function of climatic, soil‐water and edaphic properties. Water supplied by both precipitation and groundwater affects forest structure and dynamics, but in different ways. Forests with a shallow water table (depth <5 m) had 18% less above‐ground woody productivity and 23% less biomass stock than forests with a deep water table. Forests in drier climates (maximum cumulative water deficit < −160 mm) had 21% less productivity and 24% less biomass than those in wetter climates. Productivity was affected by the interaction between climatic water deficit and water table depth. On average, in drier climates the forests with a shallow water table had lower productivity than those with a deep water table, with this difference decreasing within wet climates, where lower productivity was confined to a very shallow water table. We show that the two extremes of water availability (excess and deficit) both reduce productivity in Amazon upland (terra‐firme) forests. Biomass and productivity across Amazonia respond not simply to regional climate, but rather to its interaction with water table conditions, exhibiting high local differentiation. Our study disentangles the relative contribution of those factors, helping to improve understanding of the functioning of tropical ecosystems and how they are likely to respond to climate change.
The massive die-off of the herbivorous sea urchin Diadema antillarum in 1983 and 1984 resulted in phase shifts on Caribbean coral reefs, where macroalgae replaced coral as the most dominant benthic group. Since then, D. antillarum recovery has been slow to non-existent on most reefs. Studying settlement rates can provide insight into the mechanisms constraining the recovery of D. antillarum, while efficient settlement collectors can be used to identify locations with high settlement rates and to collect settlers for restoration practices. The aim of this study was to compare pre and post die-off settlement rates and to determine possible settlement peaks in the Eastern Caribbean island of St. Eustatius. Additionally, we aimed to determine the effectiveness and reproducibility of five different settlement collectors for D. antillarum. D. antillarum settlement around St. Eustatius was highest in May, June and August and low during the rest of the study. Before the die-off, settlement recorded for Curaçao was high throughout the year and was characterized by multiple settlement peaks. Even though peak settlement rates in this study were in the same order of magnitude as in Curaçao before the die-off, overall yearly settlement rates around St. Eustatius were still lower. As no juvenile or adult D. antillarum were observed on the reefs around the settlement collectors, it is likely that other factors are hindering the recovery of the island's D. antillarum populations. Of all five materials tested, bio ball collectors were the most effective and reproducible method to monitor D. antillarum settlement. Panels yielded the least numbers of settlers, which can partly be explained by their position close to the seabed. Settler collection was higher in mid-water layers compared to close to the bottom and maximized when strings of bio balls were used instead of clumps. We recommend research into the feasibility of aiding D. antillarum recovery by providing suitable settlement substrate during the peak of the settlement season and adequate shelter to increase post-settlement survival of settlers. The bio ball collectors could serve as a suitable settlement substrate for this new approach of assisted natural recovery.
Interannual variability in the global land carbon sink is strongly related to variations in tropical temperature and rainfall. This association suggests an important role for moisture-driven fluctuations in tropical vegetation productivity, but empirical evidence to quantify the responsible ecological processes is missing. Such evidence can be obtained from tree-ring data that quantify variability in a major vegetation productivity component: woody biomass growth. Here we compile a pantropical tree-ring network to show that annual woody biomass growth increases primarily with dry-season precipitation and decreases with dry-season maximum temperature. The strength of these dry-season climate responses varies among sites, as reflected in four robust and distinct climate response groups of tropical tree growth derived from clustering. Using cluster and regression analyses, we find that dry-season climate responses are amplified in regions that are drier, hotter and more climatically variable. These amplification patterns suggest that projected global warming will probably aggravate drought-induced declines in annual tropical vegetation productivity. Our study reveals a previously underappreciated role of dry-season climate variability in driving the dynamics of tropical vegetation productivity and consequently in influencing the land carbon sink.
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362 members
Robbie Weterings
  • Coastal and Marine Management
Jessica de Koning
  • Coastal and Marine Management
Amsterdam, Netherlands