Questions: What processes govern the long-term recovery of tropical secondary forests? Specifically, how are seedling species density, stem density and functional groups in older regenerating forests ...affected by existing trees, the regeneration environment and distance to seed sources? Location: Central Catchment Nature Reserve, Singapore. Methods: We investigated three primary forest plots and nine 60-yr-old secondary forest plots varying in their degree of recovery. We analysed seedling parameters as a function of the abiotic and biotic regeneration environment as well as distance to primary and mature secondary forests. Results: The secondary forest plots had functional composition distinct from, and Chao-estimated species richness and stem density lower than the primary forest plots. Seedling communities were most strongly associated with the mature tree communities within each plot; associations with other intra-plot variables and distance to potential seed sources were lower but still highly significant. Overall, aside from the mature tree community, the most significant predictors of seedling species composition were fern cover, VPD, soil Al, available P and C:N ratio. Primary forest species were associated with low light environments, low macronutrients and low Al saturation. Secondary forest species were associated with high P, low soil pH and low total exchangeable bases. Long-lived pioneers differed from short-lived pioneers in their association with high soil C: N ratio, low Al saturation, low P and tolerance of a wider light range. Overall, improved seedling recruitment was associated with decreasing fern cover, thinner layer of leaf litter and higher light. At the landscape level, species density was inversely related to distance to potential seed sources. Conclusions: Our findings suggest that historical soil degradation and subsequent feedback processes among the adult trees, seedling communities and the regeneration environment strongly affect forest succession. Nutrient-efficient and Al-tolerant pioneers, such as the fern Dicranopteris linearis, were probably initial colonizers. Chance dispersal and recovery of the regeneration environment subsequently affected the establishment of long-lived or short-lived pioneers. Persistence of D. linearis and long-lived pioneers slowed forest recovery, while short-lived pioneers improved nutrient recovery and ameliorated the above-ground conditions to facilitate subsequent succession, provided that seeds of primary forest species were present.
•We assessed the recovery of a 56-year-old secondary forest in Singapore.•Structural and floristic recovery was poor despite proximity of primary forest.•Sapling composition between secondary and ...primary forest remained distinct.•Longevity of pioneers, thick leaf litter and dispersal limitation slowed recovery.•We demonstrate appropriate analyses for data sets with limited treatment replication.
Understanding the structure and diversity of secondary tropical forests is important as they constitute an increasing proportion of tropical landscapes. However, few studies have investigated the long-term recovery of tropical forests following agricultural abandonment. We compared the physical structure and tree species composition of a 56-year-old 2-ha secondary forest plot with an adjacent 2-ha primary forest in Singapore. All trees⩾1cm in diameter were surveyed. We found that after 56 years of recovery, the secondary forest remains floristically and structurally distinct from the adjacent primary forest. The secondary forest plot had 30% of the stem density, 58% of basal area, 26% of species richness and 59% of the Shannon diversity as compared to the primary forest plot. Nonmetric multidimensional scaling analysis and partial Mantel tests showed that the floristic composition of the two plots was distinct, even after accounting for the underlying spatial gradient in composition. Nevertheless, some shade tolerant species such as Streblus elongatus and Calophyllum spp. were thriving in the secondary forest. Our findings suggest several possible mechanisms for the slow recovery of the secondary forest, including strong dispersal limitation and the presence of long-lived pioneer species.
Secondary forests occupy a growing portion of the tropical landscape mosaic due to regeneration on abandoned pastures and other disturbed sites (Asner et al. 2009). Tropical secondary forests and ...degraded old-growth forests now account for more than half of the world's tropical forests (Chazdon 2003), and provide critical ecosystem services (Brown & Lugo 1990, Guariguata & Ostertag 2001).
In Malaysia, knowledge regarding the clinical efficacy of tenecteplase (TNK), a fibrin-specific tissue-plasminogen activator, is limited.
To evaluate the effectiveness and tolerability of TNK in ...patients with ST-segment-elevation myocardial infarction in a secondary referral Malaysian hospital.
This was a single-center retrospective case series based on the medical records of patients with ST-segment-elevation myocardial infarction admitted to the cardiac care unit between January 2016 and May 2019. Data regarding the mortality status and date of death were collected from the database of the National Registration Department of Malaysia.
Data for 30 patients with ST-segment-elevation myocardial infarction, who received weight-adjusted doses of TNK, were analyzed. The patients’ mean (SD) age was 62 (14) years, and 77% were men. The median time to treatment was 265 minutes (interquartile range = 228–660 minutes), and the clinical success rate of thrombolysis was 79%. The overall all-cause in-hospital mortality rate was 33%. The 1-year survival rates were higher in patients achieving a time to treatment ≤360 minutes (P = 0.03), with a trend toward greater survival in this group at 30 days. Similarly, a trend toward lower in-hospital all-cause mortality was observed in this group (21% vs 50%; P = 0.12). Only 1 patient (3%), who had a HAS-BLED score based on hypertension, abnormal liver/renal function, stroke history, bleeding history or predisposition, labile international normalized ratio, old age, drug/alcohol use of 5, developed major bleeding that required blood transfusion. No cases of ischemic stroke, nonmajor bleeding, in-hospital reinfarction, or TNK-induced allergic reaction were identified.
We hypothesized that the mortality-related outcomes of TNK in patients with ST-segment-elevation myocardial infarction were influenced by TTT, with TTT ≤360 minutes indicating a better prognosis than TTT >360 minutes. TNK-induced bleeding-related complications were minimal in low-risk patients. Further local studies are needed to compare TNK's profile with that of streptokinase, which is a common agent currently used in clinical practice in Malaysian public hospitals. (Curr Ther Res Clin Exp. 2021; 82:XXX–XXX)
Pristine habitats have generally been considered to be the most important ecological resource for wildlife conservation, but due to forest degradation caused by human activities, mosaics of secondary ...forests have become increasingly prominent. We studied three forest types in a mosaic tropical forest consisting of short secondary forest (SS), tall secondary forest (TS) and freshwater swamp forest (SF). These forests differed in stand structure and floristic composition, as well as phenological productivity of fruits, flowers and young leaves. We examined habitat use of long-tailed macaques (
Macaca fascicularis
) in relation to indices of phenological activity. The macaques used the SS for feeding/foraging more than the TS and the SF. This was because the SS had higher productivity of fruit, which is a preferred food resource for macaques. Stem densities of young leaves in the SS and the TS also influenced habitat use, as they provided more clumped resources. Use of SF was limited, but these forests provided more species-rich resources. Our results showed that
M. fascicularis
responded to small-scale variability in phenological activity between forest types found in a heterogeneous mosaic forest, with young secondary regrowth forests likely providing the most important food resources. Mosaic landscapes may be important as they can buffer the effects of temporal food resource variability in any given forest type. In our increasingly human-altered landscapes, a better understanding of the role of secondary forest mosaics is crucial to the conservation and management of wildlife habitats and the animals they support.
Simultaneous measurement of plant functional traits and the regeneration environment should shed light on the plant-environment interactions and feedbacks as secondary forest regenerates. However, ...little of such work has been done in the wet tropics, and even fewer studies have examined soil nutrients. We investigated whether plant functional traits and environmental variables explain the varied recovery of secondary forests in Singapore. Our study plots included three primary forest plots and eight approximately 60-year-old secondary forest plots regenerating from intensive agricultural activities. Using 35 seedling quadrats, we asked: Q1) How do environmental variables explain the variation in seedling functional traits observed in primary and secondary forests? Q2) How do seedling traits, adult traits and environmental variables relate and explain variation in species richness and stem density in secondary forests? We found that both light and soil fertility explained the shifts in plants functional traits from poorly recovering secondary forests to primary forests. Poor forest regrowth was correlated with high soil aluminum levels and lower leaf nitrogen concentrations. Low nutrients and high aluminum saturation were also negatively correlated with seedling species richness, but not stem density, in the secondary forests. Forest recovery is probably slowed by positive feedback between slower nutrient returns from slow decaying litter and further recruitment of nutrient conserving species, as indicated by positive correlations among adult leaf CN ratio, litter depth, soil CN ratio and quadrat level CN ratio. Plant functional traits are indicative of the strategies of successful seedlings and do not necessarily relate to overall forest recovery. Hence, while some specialist plant species are able to accrue high nutrients on degraded soils with aluminum toxicity and low nutrients, species richness on these soils was poor. This underscores the need to concurrently measure environmental variables and plant traits when investigating the mechanisms driving changes during forest recovery.
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•Environmental variables were significantly correlated with seedling traits.•Soil aluminum is lower but seedling leaf nitrogen is higher in primary forests.•Opposing trends in sec forests as specialist species accrued high nutrients.•Seedling traits reflect successful strategies, not necessarily forest recovery.
An obituary for Professor Dr. Mohamed Azmi Ahmad, who died on July 16, 2021, is presented. He graduated with a Bachelor's degree in pharmacy from Universiti Sains Malaysia in the year 1998, followed ...soon after with a Master's degree in the field of clinical pharmacy from the same university in 2001, consequently earning his PhD at Monash University in Melbourne, Australia in 2006. Professionally, Professor Azmi was one of the leaders in the field of social and administrative pharmacy. He obtained his professorship in 2014 at the age of 40.
Mangroves have long been associated with human populations, as coastal communities rely on the various ecosystem services that mangroves provide. However, human degradation and destruction of ...mangrove forests is common, despite and because of our reliance on them as valuable ecosystems. Mangrove research and management must elucidate and reconcile these conflicts to maintain mangrove forests and the services that humans depend on. To better understand the complex dynamics, interactions and relationships that exist between mangroves and coastal communities, the 5th Mangrove Macrobenthos and Management (MMM5) conference was held in Singapore in July 2019, with the theme “Mangroves and People: Impacts and Interactions”. This theme was chosen because Southeast Asia is the epicentre of ongoing mangrove loss, and a large number of coastal communities in the region rely on the ecosystem services that mangroves provide. The 32 papers published in this Special Issue represent the breadth of mangrove research presented at MMM5, including topics in faunal biology, ecosystem ecology, genetics, physical geography, biogeochemistry, remote sensing and the social sciences. The articles are characterized under the following topics: 1) mangrove ecosystem functioning; 2) range expansion of mangroves; 3) ecosystem services of mangroves; 4) anthropogenic and natural threats to mangroves; and 5) the management and social-ecology of mangroves. This Special Issue highlights the current state of the art of mangrove research and application, and describes a number of emerging new ideas and research opportunities that will continue to advance mangrove ecosystem science into the future.
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