Strong influence of trees outside forest in regulating microclimate of intensively modified Afromontane landscapes

Abstract

Abstract. Climate change is expected to have detrimental consequences on fragile ecosystems, threatening biodiversity as well as food security of millions of people. Trees are likely to play a central role in mitigating these impacts. The microclimatic conditions below tree canopies usually differ substantially from the ambient macroclimate, as vegetation can buffer temperature changes and variability. Trees cool down their surroundings through several biophysical mechanisms, and the cooling benefits occur also with trees outside forest. The aim of this study was to examine the effect of canopy cover on microclimate in an intensively modified Afromontane landscape in Taita Taveta, Kenya. We studied temperatures recorded by 19 microclimate sensors under different canopy covers, and land surface temperature (LST) estimated by Landsat 8 thermal infrared sensor. We combined the temperature records with high–resolution airborne laser scanning data to untangle the combined effects of topography and canopy cover on microclimate. We developed four multivariate regression models to study the joint impacts of topography and canopy cover on LST. The results showed a negative linear relationship between canopy cover percentage and daytime mean (R2 = 0.65) and maximum (R2 = 0.75) temperatures. Any increase in canopy cover contributed to reducing temperatures. The average difference between 0 % and 100 % canopy cover sites was 5.7 °C in mean temperatures and 10.2 °C in maximum temperatures. Canopy cover reduced LST on average by 0.05 °C/%CC. The influence of canopy cover on microclimate was shown to vary strongly with elevation and ambient temperatures. These results demonstrate that trees have substantial effect on microclimate, but the effect is dependent on macroclimatic conditions, highlighting the importance of maintaining tree cover particularly in warmer conditions. Hence, we demonstrate that trees outside forests can increase climate change resilience in fragmented landscapes, having strong potential for regulating regional and local temperatures.

Assessment of Vegetation Dynamics and Ecosystem Resilience in the Context of Climate Change and Drought in the Horn of Africa

“…Studies on vegetation dynamics and their quantification are numerous, and accurate measurement at larger areas may increase human understanding of the dynamics in the terrestrial ecosystem, carbon exchange system, and climate-biosphere interactions in the environment [13,14]. The dynamics of vegetation for small areas can be assessed and monitored with field-based measurements [15], however, as the spatial coverage and temporal variability increases, the complexity of the vegetation and types in structure and phenology also changes and varies essentially.…”

Natural forests for a safe climate: Enhancing ecosystem integrity, biodiversity and adaptive capacity for climate mitigation

“…Higher fragmented and more isolated forest fragments tend to advance changes in local climatic conditions, leading to drier, hotter, and increasingly volatile microclimate (Laurance et al, 2002;Tuff et al, 2016). Nevertheless, small forest fragments and green canopy cover adjacent to the highly modified anthropogenic landscape also provide substantial benefits for regulating the microclimate (Aalto et al, 2022). However, such effects are more pronounced in large intact forests (Gohr et al, 2021).…”

Does fragmentation contribute to the forest crisis in Germany?

“…Higher fragmented and more isolated forest fragments 10.3389/ffgc.2023.1099460 tend to advance changes in local climatic conditions, leading to drier, hotter, and increasingly volatile microclimate (Laurance et al, 2002;Briant et al, 2010;Tuff et al, 2016). Nevertheless, small forest fragments and green canopy cover adjacent to the highly modified anthropogenic landscape also provide substantial benefits for regulating the microclimate (Aalto et al, 2022). However, such effects are more pronounced in large intact forests (Gohr et al, 2021).…”