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Spatial patterns of light-demanding tree species in the Yangambi rainforest (Democratic Republic of Congo).

ABSTRACT: Most Central African rainforests are characterized by a remarkable abundance of light-demanding canopy species: long-lived pioneers (LLP) and non-pioneer light demanders (NPLD). A popular explanation is that these forests are still recovering from intense slash-and-burn farming activities, which abruptly ended in the 19th century. This "human disturbance" hypothesis has never been tested against spatial distribution patterns of these light demanders. Here, we focus on the 28 most abundant LLP and NPLD from 250 one-ha plots distributed along eight parallel transects (~50 km) in the Yangambi forest. Four species of short-lived pioneers (SLP) and a single abundant shade-tolerant species (Gilbertiodendron dewevrei) were used as reference because they are known to be strongly aggregated in recently disturbed patches (SLP) or along watercourses (G. dewevrei). Results show that SLP species are strongly aggregated with clear spatial autocorrelation of their diameter. This confirms that they colonized the patch following a one-time disturbance event. In contrast, LLP and NPLD species have random or weakly aggregated distribution, mostly without spatial autocorrelation of their diameter. This does not unambiguously confirm the "human disturbance" hypothesis. Alternatively, their abundance might be explained by their deciduousness, which gave them a competitive advantage during long-term drying of the late Holocene. Additionally, a canonical correspondence analysis showed that the observed LLP and NPLD distributions are not explained by environmental variables, strongly contrasting with the results for the reference species G. dewevrei, which is clearly aggregated along watercourses. We conclude that the abundance of LLP and NPLD species in Yangambi cannot be unambiguously attributed to past human disturbances or environmental variables. An alternative explanation is that present-day forest composition is a result of adaptation to late-Holocene drying. However, results are inconclusive and additional data are needed to confirm this alternative hypothesis.

SUBMITTER: Luambua NK

PROVIDER: S-EPMC8717288 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:An increase of congenital anomalies in the eastern Democratic Republic of the Congo (DRC) has been reported. Congenital malformations (CMs) are not uncommon among newborns and, if left untreated, can contribute to increased neonate morbidity and mortality.Medical records of all individuals admitted with a diagnosed CM to HEAL Africa Teaching Hospital (Goma, DRC) from 2002 to 2014 (n=1301) were reviewed. Data were analysed using descriptive statistics to summarize chart records, and inferential statistics to investigate significant barriers to earlier treatment.Since 2012, the number of patients treated each year for CMs has increased by over 200% compared to the average annual number of cases treated from 2002-2011. Though delayed presentation of patients to HEAL Hospital was very obvious, with an average age of 8.2 years. We find that patient age has been significantly decreasing (p=0.037) over time. The average distance separating patients from HEAL Hospital was 178 km, with approximately one third living 350 km or further from the treatment center. Distance is the most significant (p=3.33x10(-6)) barrier to earlier treatment. When controlling for an interaction between gender and the use of mercy funds, we also find that female patients are at a significant (p=1.04x10(-3)) disadvantage to undergo earlier corrective surgery. This disadvantage is further illustrated by our finding that 89% of women and girls, and over 81% of all patients, required mercy funds to cover the cost of surgery in 2014. Lastly, the mortality rate for surgery was low and averaged less than 1.0%.Despite a formal end to the war in 2009, and an overall increase in individuals undergoing corrective surgery, distance, poverty, and gender are still massive barriers to CM care at HEAL Hospital, Goma, DRC. We find that patients have been successfully treated earlier by HEAL, although the average age of CM correction in 2014 (4.9 years) is still above average for Sub-Saharan Africa. Thus, we advocate for further funding from the National Government and international health agencies to enable continued treatment of CMs in rural residents of the eastern DRC. Distance, the most significant barrier to care can be mitigated by the implementation of additional mobile clinics and the construction of regional surgery centers along with the associated hiring of surgeons trained in CM repair.

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Spatial patterns of light-demanding tree species in the Yangambi rainforest (Democratic Republic of Congo).

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