Southern Sites Research Articles

Fifty percent overestimation of black carbon concentration measured in aerosols of the Tibetan Plateau

Elemental carbon (EC), also known as black carbon, plays an important role in climate change. Accurately assessing EC concentration in aerosols remains challenging due to the overestimations caused by carbonates and organic carbon (OC) during thermal-optical measurement in the Tibetan Plateau (TP). This study evaluates the extent of EC overestimated by carbonates and OC at four remote sites (Nyalamu, Lulang, Everest and Ngari) in southern and western of the TP using different treatments. The average overestimation of EC concentration due to acid treatment was consistent across all sites (25.5 ± 2.4 %). After correction, the proportion of EC overestimated by carbonates were approximately 8.5 ± 7.3 %, 12.3 ± 6.9 %, 18.1 ± 11.8 % and 22.7 ± 13.3 %, respectively, revealing an increasing trend from humid to arid regions. Methanol-soluble OC (MSOC) concentrations were significantly correlated with the reduction of EC concentrations, indicating that the methanol extraction effectively mitigates EC overestimation. Seasonal variation of carbonaceous aerosol concentrations was significantly affected by sources from South Asia. Despite the variations in climate and aerosol sources, the average overestimations of measured EC concentration by carbonates and OC were similar at Nyalamu (49.4 ± 14.0 %), Lulang (47.8 ± 8.4 %), Everest (48.7 ± 15.9 %) and Ngari (49.3 ± 13.7 %) sites. Therefore, the actual EC concentrations were only about 51.2 ± 13.1 % of the original values. This estimation will significantly enhance the contribution of brown carbon (BrC) to radiative forcing relative to EC, highlighting a critical area for future research. Investigating the actual concentrations of EC in the TP provides critical data to support model simulation and validate model accuracy, further enhancing our understanding of EC’s impacts on climate warming and glacier melting.

Subalpine fir response to drought in northern British Columbia, Canada

Abstract As global warming continues, drought severity and duration are expected to increase in many areas of the world, necessitating a thorough understanding of how trees react to severe drought periods. In this study, we used dendrochronological analyses to determine the response of subalpine fir [Abies lasiocarpa (Hook.) Nutt.] to historical drought events on sites along a latitudinal interval of 500 km in the Rocky Mountains in northern British Columbia, Canada. We used the ClimateBC Climate Moisture Deficit index to approximate drought conditions at the sites and to identify common drought years across sites. We then compared wood densities across the time series to temperature, precipitation, and climate moisture indices for the locations studied to determine relationships between subalpine fir wood densities and climate in this region. We demonstrated that subalpine fir wood density was often negatively correlated to spring and summer temperatures and that these stands are responsive to drought events in the short term. We found that the latitudinal difference between stands was not as pronounced as expected; however, northern sites had a stronger climate response and more frequent drought years than southern sites. This cautiously suggests that the impacts of climate change may be more intensely felt in forests at more northern latitudes. If droughts continue to become more frequent in northern British Columbia, as is predicted with changing climates, we might expect less carbon sequestration and lower wood strength in subalpine fir trees from this region.

Heatwave events and concurrent ozone concentrations between 2006 and 2022 at two sites in southern and northern Spain.

Hotter-than-usual days are becoming more common, such that heat waves are expected to increase in intensity, frequency, duration, and spatial extent in Spain. Within this framework, this paper looks at the combined effects of extreme temperatures and air pollution in two cities in Spain, Córdoba and Valladolid, over the period 2006-2022. Synoptic patterns and air mass movement were analysed during the eleven coincident heat waves at both locations in order to study what impact orography and local meteorology have on ozone concentrations. Weak flow conditions were the most frequent synoptic pattern in the Iberian Peninsula during heat waves. Moreover, west and local circulations characterised the main air trajectories at low levels (500m agl), while southwest maritime advections and African air mass transport were more frequent at higher levels (1500 and 3000m agl) in Córdoba and Valladolid, respectively. On average, maximum ozone values were higher in Córdoba (105.1µgm-3) than in Valladolid (80µgm-3) and were strongly correlated with extreme temperatures at both locations (r up to 0.8, p-value < 0.05). Mean temperature in Córdoba was 31.9°C, with the maximum value reaching 43.7°C, while temperatures in Valladolid were lower (28.3°C and 37.3°C, respectively). Calculation and assessment of some indices helped to understand the impact of extreme events. Caution actions based on the Heat Index characterised heat wave periods. Moderate risk was the general Air Quality Health Index feature recorded and reached a very high risk of unhealthy air quality in the June 2022 event in Córdoba.

Variable preservation of the 1991 Hudson tephra in small lakes and on land

Volcanic ash (tephra) preserved in terrestrial environments and lake sediments contains information about volcanic processes and can be used to infer eruptive parameters and frequency of past eruptions, contributing to the understanding of volcanic hazards. However, tephra deposits can undergo transformation from their initial fallout sedimentation to being preserved as a tephra layer in the sedimentary record. The process is likely to be different in lakes and in terrestrial (soil) sequences. Here we compare the thickness, mass loading and grain size of tephra layers from the 1991 eruption of Cerro Hudson, Chile, from small lakes and adjacent terrestrial settings to measurements of the tephra made shortly after the eruption. We analysed samples from 35 cores in total from six small lakes (&amp;lt;0.25 km2), located 76 and 109 km from the volcano in two contrasting climatic areas (cool and humid northern site, and warm and dry southern site), and made 73 measurements of tephra thickness and 11 measurements of grain size in adjacent terrestrial areas. The major element geochemistry of our samples confirmed they were from the 1991 Hudson eruption. We found that some of the measured characteristics of the preserved tephra layers were comparable to those recorded in 1991 shortly after initial deposition, but that there was considerable variability within and between locations. This variability was not predictable and lake sediments did not preserve a notably more accurate record of the fallout than terrestrial sites. However, in aggregate the characteristics of the preserved tephra was similar to those recorded at the time of deposition, suggesting that, for palaeotephra research, a sampling strategy involving a wide range of environments is more robust than one that relies on a single sedimentary record or a single type of sedimentary environment.

Historical Geography in Brazil: Examining Backgrounds and New Perspectives

ABSTRACTThe sub‐discipline of historical geography in Brazil, in contrast to the Anglophone and Francophone scholarship, often tends to be overlooked by the northern disciplinary history of this sub‐discipline. In Brazil, historical geography studies emerged in the 1980s as a result of personal initiatives. Nonetheless, in the last few years, distinct generations of Brazilian historical geographers have contributed to this sub‐discipline's promotion and recognition, mainly by diversifying their methodological approaches and research interests. Undoubtedly, developing transnational academic networks and collaborations represents a crucial contribution. This review provides an overview of the main Brazilian historical geographers engaged in studying past geographies. It delves into the central themes they address and also examines the academic conferences and research groups responsible for establishing institutional spaces to foster the practice of historical geography in Brazil in recent years. In doing so, the review calls for a ‘polyphonic’ approach to historical geography, urging the inclusion of southern sites of knowledge production and embracing a diverse scholarship beyond the English‐speaking community.

Economic evaluation of corn relative maturity hybrids in corn–pennycress–soybean rotations

AbstractThis manuscript is a follow‐up of previously published results that presented findings on pennycress (Thlaspi arvense L.) establishment and agronomics in response to previous corn (Zea mays L.) relative maturity (CRM) hybrids grown for grain and silage in the corn–pennycress–soybean [Glycine max (L.)] rotations. In this manuscript, we compared the economics of grain corn–pennycress–soybean rotations (grain rotation) with silage corn–pennycress–soybean rotations (silage rotation). The treatments were CRM hybrids ranging from 76 to 95 days (full season) at northern sites (Morris and Rosemount, MN) and 95 to 113 days (full season) at southern sites (Lexington, IL, and Custar, OH). Full‐season corn harvested for silage was included as a control treatment representing optimum conditions for sowing pennycress. A partial budget procedure was used for economic analysis. The results showed that the annualized net benefits (ANBs) ranged from $315 to $945 ha−1. The silage rotation produced greater ANBs than the grain rotation at all sites due to increased pennycress seed yield. In the grain rotation, the 105 days in the south, 95 days corn at Morris, and 86 days corn at Rosemount resulted in minimal ANB losses compared with silage rotation. Among grain corn treatments, some of the early CRM hybrids resulted in greater ANBs (up to 40%) than the full season hybrid. Results demonstrate potential to integrate pennycress into a grain rotation using early CRM hybrids. In addition, valuing the diverse ecosystem benefits that pennycress offers as a cash cover crop during the offseason between corn and soybean rotation may help to attract growers.

ESTIMATION OF NITRIC ACID GAS DRY DEPOSITION IN VIET NAM

This article uses dry deposition calculating method to estimate Nitric acid (HNO3) gas dry deposition and analyze, evaluate trend of HNO3 gas dry deposition in recent years. The results present that HNO3 gas concentration is from 0.02 to 0.83 ppb and Yen Bai site has the highest HNO3 gas emission in 2020 and 2021. High HNO3 gas emission focuses on summer and spring at Northern’s sites. HNO3 gas emission at Southern sites is lower than that of Northern ones. HNO3 gas dry deposition is from 6.63 kg/ha/year to 10.26 kg/ha/year and the highest HNO3 gas dry deposition value is in 2021. Ha Noi site has the highest HNO3 gas dry deposition value in 2019, 2020, and 2022 while Yen Bai site is in 2021 and 2023. HNO3 gas dry deposition value at Southern sites is lower than Northern sites. The highest monthly HNO3 gas dry deposition is from June to August at Yen Bai site in 2021 and May in 2020. Annual average HNO3 gas dry deposition of 2021 is higher than other years. HNO3 gas dry deposition in recent years has an increasing trend.

Assessing water quality of kazerun county in southwest Iran: Multi-analytical techniques, deterministic vs. probabilistic water quality index, geospatial analysis, fuzzy C-means clustering, and machine learning

Water quality is critical to human health and the environment, especially in arid and semi-arid regions. Hence, the objectives of this study were to assess drinking water quality, identify critical parameters, investigate spatial patterns, and investigate accurate predictive models for the water quality index (WQI) in the Kazerun county in southwest Iran. To address this issue using deterministic and probabilistic WQI, correlation matrix, fuzzy C-Means (FCM) clustering, geostatistics, and adaptive network-based fuzzy inference system (ANFIS) with FIS generation by fuzzy C-Means (FCM-ANFIS) and sub-clustering (SC-ANFIS).Various software tools, including Excel, MATLAB, Python, and GIS were used to analyze groundwater data collected from 25 sampling sites. Water parameters, including pH, Cl−, SO4−2, EC, NO3−, NO2−, Ca2+, Mg2+, and F−, were examined. The results showed that F− levels were within acceptable limits set by the US EPA, but about one-third of sites posed potential health risks based on WHO guidelines. In one-third of regions, the levels of Mg2+ exceeded the recommended guidelines. In deterministic and probabilistic approaches, water quality was excellent in 68% and 81.3% of sites, respectively. Sobol sensitivity analysis identified SO4−2> Mg2+>Cl− > EC > F− > NO3− as significant WQI variables. Spearman correlation matrix shows substantial positive correlations between WQI and EC, F−, SO4−2, Mg2+, and Cl− were shown by the Spearman correlation matrix. Based on the FCM results, the southeast and central sites (56% of sites) have similar water quality. In comparison, the northern and four central sites (28% of sites) have distinct regional features, and the southern sites (16% of sites) had unique water quality characteristics. Geostatistical analyses showed that pH had the most substantial local clustering, while SO4−2 had significant high-value clustering. Furthermore, hot spot research revealed specific sites with high pH, F−, NO3−, and Cl− levels. The FCM-ANFIS model outperformed the SC-ANFIS model, emphasizing FCM clustering's importance in water quality forecasting accuracy.

Trend of SO2 Gas Dry Deposition in Vietnam

This research used the calculating method of dry deposition to estimate SO2 dry deposition value and evaluate its trend in 5 recent years. The results indicate that SO2 emission at Northern sites is more changing than Southern ones in months by affecting meteorology and weather. Summer and autumn seasons have SO2 emitted concentrations higher than other seasons in 2019, 2020, and 2022 year at Yen Bai, Hoa Binh, and Ha Noi stations. The 2021 year has the highest SO2 dry deposition and the 2019 year has the lowest SO2 dry deposition in 5 recent years. The Hanoi site has the highest SO2 dry deposition value from 2019 to 2022 year. Hoa Binh site has the highest SO2 dry deposition at 2.45 kg/ha/year in 2023. High SO2 dry deposition occurs normally in the summer and autumn (from April to August). Southern sites have lower SO2 dry deposition amounts with not much change than the Northern sites of Vietnam. The increasing trend of SO2 dry deposition happened from 1999 to 2023 year and it increases sharply from 1999 to 2021. Therefore, SO2 dry deposition will have a light-increasing trend in the future.

Long-term measurements of aerosol composition at rural background sites in France: Sources, seasonality and mass closure of PM2.5

Fine particulate matter (PM2.5) was monitored at five rural background locations in France from 2012 to 2021. Annual PM2.5 ranged from 5 to 15 μg m−3, all sites repeatedly exceeding the 2021 annual World Health Organization guideline. Chemical speciation including organic and elemental carbon (OC, EC), secondary inorganic aerosols (SIA: NO3−, SO42−, NH4+) and other major water-soluble ions (Cl−, Na+, Mg2+, Ca2+, K+) were monitored on 24-h filters covering 14% of the year. A source apportionment of OM was undertaken based on fine potassium and using representative ratios for domestic biomass burning (BB) and fossil fuel (FF) emissions. The latter dominated the EC fraction (55–60%) while BB was the main primary source of OM (27–54%). The average mass balance of PM2.5 at the French rural background atmospheric sites was: secondary organic aerosol (18–35%), BB (17–27%), non-sea-salt sulphate (12–17%), nitrate (6–22%), ammonium (7–11%), FF (4–6%), mineral dust (3–9%) and sea salt (1–2%). Secondary aerosols were the main component of PM2.5 through all seasons, with SIA dominating in spring episodes. The contribution of OM to PM2.5 was larger at the southern sites whereas the contribution of SIA was larger at the northern sites. The mean OC/EC ratio and the good correlations between OC, EC, and fine potassium suggested that BB was the main primary source contributing to carbonaceous aerosols, 27–54% to total OM depending on the site; and also, to PM2.5 (17–27%). Stronger regulations of OM sources including BB, nitrate from combustion, and ammonium from agricultural sources are needed to reduce PM2.5 at rural background sites on an annual and episodic basis, respectively.

Tropical cyclone activity over the past 1200 years at the Pelican Cays, Belize

Tropical cyclone (TC) models indicate that continued planet warming will likely increase the global proportion of powerful TCs (specifically Categories 4 and 5 hurricanes), increasingly jeopardizing low-lying coastal communities and resources such as the Pelican Cays, Belize. The combination of increased coastal development and continued relative sea-level rise puts these communities at even higher risk of damage from TCs. The short TC observational record for the western Caribbean hampers the extensive study of TC activity on centennial timescales, which hinders our ability to fully understand past TC climatology and improve the accuracy of TC models. To better assess TC risk, paleotempestological studies are necessary to put future scenarios in perspective. Here, we present a high-resolution reconstruction of coarser-grained sediment deposits associated with TC (predominately ≥ Category 2 hurricanes) passages over the past 1200 years from Elbow and Lagoon Cays, two coral reef-bounded lagoons at the northern and southern end of the Pelican Cays; the most southern Belizean paleotempestological site to date. Coincident timing of historic storms with statistically significant coarser-grained deposits within cay lagoon sediment cores allows us to determine which historic TCs likely generated event layers (tempestites) archived in the sediment record. Our compilation frequency analysis indicates one active interval (above-normal TC activity) from 1740-1950 CE and one quiet interval (below-normal TC activity) from 850-1018 CE. The active and quiet intervals in the Pelican Cays composite record are anticorrelated with those from nearby and re-analyzed TC records to the north, including the Great Blue Hole (∼100 km north) and the Northeast Yucatan (∼380 km northwest). This site-specific anticorrelation in TC activity along the western Caribbean indicates that we cannot rely on any one single TC record to represent regional TC activity. However, we cannot discount that these anticorrelated periods between the western Caribbean sites are due to randomness. To confirm that the anticorrelation in TC activity among sites from the western Caribbean is indeed a function of climate change and not randomness, an integration of more records and TC model simulations over the past millennium is necessary to assess the significance of centennial-scale variability in TC activity recorded in reconstructions from the western Caribbean.

Optimizing bioenergy sorghum productivity and nutrient removal in Illinois: Impact of nitrogen fertilization under diverse marginal conditions

Context or problemBioenergy sorghum (Sorghum bicolor L. Moench) is a promising crop for contributing to the United States bioenergy supply. However, the varying limitations of the marginal lands targeted for its cultivation present a management challenge. ObjectiveThis two-year study aimed to investigate how the limitations associated with marginal cropland impact the effects of nitrogen fertilization on the yield of bioenergy sorghum and the uptake of 11 macro- (N, P, K, Ca, Mg, and S) and micronutrients (Fe, Mn, Zn, Cu, and B). MethodsThe study contrasted prime cropland in central Illinois (Urbana) with three marginal cropland sites in southern (Ewing) and central Illinois (Fairbury and Pesotum). These marginal cropland sites are characterized by varying limitations, including low soil fertility (P and K limitations), leaching and erosion, and flooding, respectively. Four nitrogen rates (0, 56, 112, and 168 kg N ha−1) were tested under eight environments. ResultsThe average yields and ranges of sorghum biomass were 20.2 (17.0–23.2) Mg ha−1 in Urbana, 18.1 (13.1–19.8) Mg ha−1 in Ewing, 13.8 (9.0–17.3) Mg ha−1 in Fairbury, and 23.3 (14.6–33.0) Mg ha−1 in Pesotum. Optimal N rates were 56 N in Pesotum and 112 N in Urbana, Ewing, and Fairbury. Tissue macronutrient contents in Urbana were generally higher than in the marginal croplands, while micronutrient contents did not show discernible trends. Increasing N rate generally correlated with the macronutrient removal except in Ewing. ConclusionComparable sorghum biomass yields were observed between prime and marginal croplands (averaging 18.3 Mg ha−1), but optimal N rates varied between 56 N and 112 N. This suggests that yield gaps can be narrowed by applying the optimal N rates for the respective locations. However, increased removals of macronutrients, especially P and K, with increasing yields indicate the need to revise fertilizer recommendations, particularly for soils deficient in these nutrients. Implications or significanceOur study suggests that while sorghum production on marginal cropland is feasible, N management needs to be adapted to the unique limitations associated with various types of marginal cropland.

Awareness, treatment, and control of hypertension among women at risk or living with HIV in the US South.

Timely control of hypertension is vital to prevent comorbidities. We evaluated the association of race/ethnicity and HIV infection with incident hypertension outcomes, including awareness, treatment, and control. We evaluated cisgender women living with HIV and sociodemographically matched women living without HIV recruited into four Southern sites of the Women's Interagency HIV Study (WIHS) (2013-2019). We calculated measurements of the time to four events or censoring: incident hypertension, hypertension awareness, hypertension treatment, and hypertension control. Hazard ratios for race/ethnicity and HIV status were calculated for each outcome using Cox proportional-hazards models adjusted for sociodemographic, behavioral, and clinical risk factors. Among 712 women, 56% were hypertensive at baseline. Forty-five percentage of the remaining women who were normotensive at baseline developed incident hypertension during follow-up. Non-Hispanic white and Hispanic women had faster time to hypertension control compared with non-Hispanic black women ( P = 0.01). In fully adjusted models, women living with HIV who were normotensive at baseline had faster time to treatment compared with normotensive women living without HIV ( P = 0.04). In our study of women in the US South, non-Hispanic black women became aware of their hypertension diagnosis more quickly than non-Hispanic white and Hispanic women but were slower to control their hypertension. Additionally, women living with HIV more quickly treated and controlled their hypertension compared with women living without HIV.

Eocene–Oligocene vegetation and climate changes in southeastern Brazil

The Eocene–Oligocene Transition (EOT) marks the onset of a major phase of global cooling with significant consequences to the vegetation worldwide. Here, we present palynological analyses from a site in southern São Paulo basin, southeastern Brazil (23.67°S; 46.58°W). An Oligocene age was constrained by the abundance of Dacrydiumites florinii and Podocarpidites spp., alongside the presence of taxa such as Cicatrocosisporites dorogensis and Polypodiisporites usmensis. Autochthonous elements including Paleoazolla, Corsinipollenites spp., Monoporopollenites annulatus, and Zygnemataceae algae spores are indicative of a low-energy freshwater depositional environment. In addition, we performed a comparison of Eocene and Oligocene temperature and precipitation estimates from records in southeastern Brazil using the weighted Mutual Climate Range approach. Results support global trends with a cooling of ca. 3–4 °C from the Eocene to the Oligocene accompanied by slightly drier regional conditions. Oligocene environmental changes drove a vegetation turnover by local extinction of warm-tropical taxa or a significant retreat of species unable to stand comparatively colder and drier climates under lower CO2atm concentrations. Our data are consistent with previous estimates and verify the impact of global cooling on the vegetation of mid-low latitudes of the Southern Hemisphere.

Spatial Dynamics of Demersal Fish Assemblages off the Korean Coast in the East Sea.

This study assessed variations in demersal fish assemblages with respect to the study site and water depth. Seasonal samplings from May 2018 to March 2019 were conducted along the northern (Ayajin, Goseong) and southern (Hupo, Uljin) sites of the East Sea off the Korean coast, using commercial gill nets. Samples were collected at depths of ~50, ~80, ~150 m across the study sites, with concurrent monitoring of water column structures. A total of 73 species and 6250 specimens were collected. Distinctive fish species compositions were observed according to the study site and depth. Although Glyptocephalus stelleri was the most abundant fish species in both Ayajin and Hupo, Gadus macrocephalus, Icelus cataphractus, and Alcichthys elongatus were most predominant in Ayajin, whereas Cleisthenes pinetorum, Hippoglossoides dubius, and Gymnocanthus herzensteini were more prevalent in Hupo. In terms of depth layer, in Ayajin, G. stelleri dominated in both intermediate and deeper layers, with Hemilepidotus gilberti, A. elongatus, Enophrys diceraus common in shallower depths. Conversely, in Hupo, G. stelleri, C. pinetorum, and A. nadeshnyi dominated across all depth layers, whereas Dasycottus setiger and G. herzensteini dominated in deeper and shallower depths, respectively. Significant influences of the study site and water depth on fish assemblage structures were observed due to variations in water temperature at the seasonal thermocline boundary.

Variation in the strength and stationarity of southern longleaf pine seasonwood climate-growth relationships

Climate change is predicted to cause asymmetric warming and increased precipitation variability across different seasons. These changes and their effects may be captured in subannual seasonwood measures of tree growth (i.e., earlywood, latewood). Longleaf pine is a foundational tree species throughout the broad southeastern U.S. Its latewood growth may be more variable and sensitive to climate change than earlywood, but prior studies have geographical and ecological sampling limitations. Here, we use dendroecological methods to develop ring-width and seasonwood (earlywood, latewood, and adjusted latewood) chronologies and analyze climate-growth relationships for longleaf pine from eight sites in the Southern Coastal Plain of Florida, USA. Sites spanned a range of environmental conditions to generate an ecologically representative dataset. We evaluated chronology strength and variability and determined monthly and seasonal correlations with precipitation and temperature. We furthermore evaluated climate-growth stationarity using a moving response function and bootstrapped transfer function stability tests. We found adjusted latewood chronologies were most climatically sensitive although totalwood chronologies had higher interseries correlations. Totalwood measurements were more variable than early- or latewood year to year. Tree growth was positively correlated with summer precipitation at six out of eight sites and negatively correlated with late summer maximum temperatures at six out of eight sites. Negative relationships between growth and maximum temperature occurred earlier in the year at southern sites and the positive effect of June precipitation on tree growth was notable, found at six out of eight sites. However, the strength and significance of climate-growth relationships were non-stationary through space and time, with shifts largely occurring post-1950s. Longleaf pine at its southern range extent was less sensitive to climate than more northern populations, which may indicate non-linear responses to warming captured at the species’ range margin. Our results highlight dynamic climate-growth relationships related to the broad range of environmental conditions where longleaf pine is found.

Vanishing giants: An assessment on the population status of giant clams across Malaysia

The iconic giant clams are known for its multifaceted importance throughout the Indo-Pacific –for functional, ecological, or cultural purposes. In Malaysia, habitat destruction and illegal poaching were main reasons behind the declining populations of giant clams. As previous surveys date back to 1990 s, an update on the status of giant clam populations in Malaysia is overdue. Using the extensive monitoring data from Reef Check Malaysia, we analysed and provided an assessment of population trends of giant clams between 2007 and 2021 in Malaysia. This study showed a decline in giant clam population in the east coast Peninsula and Sabah, while their abundances have always been low in the west coast Peninsula and Sarawak. In the east coast Peninsula, Tridacna maxima and T. crocea were most common (2.7 ± 7.3 and 1.4 ± 7.6 clams per 100 m2, respectively), followed by T. squamosa (0.7 ± 1.4 clams per 100 m2), and Hippopus hippopus (0.3 ± 2.5 clams per 100 m2). The boring species, T. maxima and T. crocea, typically displayed highly aggregated populations, reaching densities of 41.5 and 70 clams per 100 m2, where a reciprocal abundance shift between both species was observed between northern and southern sites of east coast Peninsula. The demography of T. maxima and T. crocea is either positively skewed or normally distributed, indicating abundant recruits that correspond to their higher densities. In contrast, T. squamosa showed a negative skew, suggesting poor recruitment rates. Findings here underscore the need to tailor conservation strategies for respective giant clam species in Malaysia. Proposed initiatives include establishing conservation zones in key areas like Perhentian, Lang Tengah, Redang, and Tioman Islands, which have significant T. maxima and T. crocea recruit populations. Also, targeted restocking efforts are necessary for T. squamosa and H. hippopus to ensure long-term viability of populations.

Radial distribution of heartwood extractives in second-growth western redcedar

Western redcedar has high economic value and has been traditionally used for cultural purposes by Indigenous communities. Second-growth redcedar is potentially growing faster due to lower planting densities, fertilization, and tree breeding. Little quantitative information is available about the impact of management practices on wood quality, particularly heartwood extractives. This study evaluated the effects of growth rate and site on heartwood extractives at two locations aged 70–90 years in British Columbia, Canada. A three-parameter sigmoid model was fit to the data using nonlinear mixed effects to analyze the relationship between heartwood extractives relative to cambial age, growth rate, and sampling site. The southern site had significantly higher cumulative extractive concentrations, while all extractive concentrations increased faster. This study shows that smaller trees will reach their peak concentrations earlier than larger trees. Results show that faster growth through active management of western redcedar may lead to increased and more uniformly distributed content of heartwood extractives.

Interplay of management and environmental drivers shifts size structure of reef fish communities.

Countries are expanding marine protected area (MPA) networks to mitigate fisheries declines and support marine biodiversity. However, MPA impact evaluations typically assess total fish biomass. Here, we examine how fish biomass disaggregated by adult and juvenile life stages responds to environmental drivers, including sea surface temperature (SST) anomalies and human footprint, and multiple management types at 139 reef sites in the Mesoamerican Reef (MAR) region. We found that total fish biomass generally appears stable across the region from 2006 to 2018, with limited rebuilding of fish stocks in MPAs. However, the metric of total fish biomass masked changes in fish community structure, with lower adult than juvenile fish biomass at northern sites, and adult:juvenile ratios closer to 1:1 at southern sites. These shifts were associated with different responses of juvenile and adult fish to environmental drivers and management. Juvenile fish biomass increased at sites with high larval connectivity and coral cover, whereas adult fish biomass decreased at sites with greater human footprint and SST anomalies. Adult fish biomass decreased primarily in Honduran general use zones, which suggests insufficient protection for adult fish in the southern MAR. There was a north-south gradient in management and environmental drivers, with lower coverage of fully protected areas and higher SST anomalies and coastal development in the south that together may undermine the maintenance of adult fish biomass in the southern MAR. Accounting for the interplay between environmental drivers and management in the design of MPAs is critical for increasing fish biomass across life history stages.

Spatial management measures benefit the critically endangered flapper skate, Dipturus intermedius

Abstract While elasmobranchs are often a designated feature in Marine Protected Areas, there are few studies that have evaluated the effectiveness of spatial fishery restrictions on their recovery. Here we examine the effectiveness of fishery restrictions on the critically endangered flapper skate, Dipturus intermedius, based on changes in their abundance, demography and survival rate. Trends in local abundance at two sites within the Loch Sunart to the Sound of Jura Marine Protected Area (LStSJ MPA), were contrasted with that in surrounding waters off the west of Scotland where fishing remains unrestricted. Survival rate was estimated using a multi‐state model of capture mark recapture data, and spill‐over from the LStSJ MPA was considered from tag‐recapture rates between the two LStSJ MPA study areas and a further site south of the LStSJ MPA. In contrast to the wider trend across adjacent waters, skate abundance increased, especially for young juveniles, following the introduction of fishing restrictions in the LStSJ MPA. This increase could be explained by a reduction in juvenile and adult mortality as population growth rates following fishing restrictions were markedly higher than estimated in a pre‐restriction study of one site. Limited exchange of skate between the two study areas within the LStSJ MPA and a southern site beyond the LStSJ MPA indicated a low rate of spill‐over. This study demonstrates that spatial fishery restrictions have the potential to benefit populations of elasmobranchs which have a high site‐fidelity, but their wider conservation benefit may be partly confounded by a high level of residency.