arXiv subjects

Colin A. Chapman

Publications and source records attributed to Colin A. Chapman.

2 recordsLinked to original sources

arXiv2026

From seasons to decades: Solar radiation, cloud cover, and CO$_2$ shape young leaf phenology in a tropical forest over 26 years

1. Climate change is altering plant phenology globally with potential deleterious impacts on animal species and entire ecosystems, yet the long-term effects of climate change on tropical leaf production remain poorly understood. 2. We analyzed 26 years of young leaf phenology field data from Kibale National Park, Uganda, focusing on 12 tree species consumed by leaf-eating mammals. We examined seasonal and long-term patterns and how they are related to climatic variables using Bayesian hierarchical generalized additive mixed models (GAMMs). 3. The tree community and most species exhibited peaks in young leaf production during the two annual rain seasons, with seasonal changes primarily associated with diffuse light availability through solar radiation and cloud cover, as well as rainfall and minimum temperature. Long-term variations in leaf production was primarily linked to long-term changes in atmospheric CO2, solar radiation, and cloud cover. 4. Our results support the role of CO2 fertilization, though decreasing levels of solar radiation resulting from the ending of the recent solar cycle may be slowing this effect. 5. Synthesis: This study highlights the critical role of diffuse light, solar radiation, and the solar cycle in predicting tropical leaf production, emphasizing that interpretations of greening trends must consider solar radiation alongside atmospheric CO2 levels. Furthermore, our findings emphasize the complex relationship between climate and young leaf phenology, highlighting the importance of integrating species-specific long-term data to better understand the effects of climate change on food availability for tropical folivores and tropical forest ecosystems in general.

q-bio.QM↗

arXiv2015

Population pressure and global markets drive a decade of forest cover change in Africa's Albertine Rift

The Albertine Rift region faces rapid human population growth, while being a biodiversity hotspot. Using satellite-derived continuous forest cover change data, we examined national socioeconomic, demographic, and agricultural production data, and local demographic and geographic variables to assess multilevel forces driving significant local forest cover loss and gain outside protected areas during the first decade of this century. Because the processes that drive forest cover loss and gain are expected to be different, we constructed models of change in each direction. Although forest cover change varied by country, national level population change was the strongest driver of forest loss rate for all countries, with a population doubling predicted to cause 2.06 percent annual cover loss, while doubling tea production was predicted to cause 1.90 percent. The rate of forest cover gain was associated positively with increased production of the local staple crop cassava, but negatively with local population density and meat production, suggesting production drivers at multiple levels mitigate reforestation. We found a small, but significant, decrease of forest cover loss rate with increasing distance from protected areas, supporting studies suggesting higher rates of landscape change near protected areas. While local population density mitigated the rate of forest cover gain, cover loss also correlated to lower local population density, an apparent paradox, but consistent with findings that larger scale forces outweigh local drivers of deforestation. This implicates demographic and market forces at national and international scales as critical drivers of change, calling into question the necessary scale of forest protection policy in this biodiversity hotspot.

q-bio.OT↗