Analysis of the Ecological Performance of Multi- And Single-Taxa Restoration Approaches In the Eastern Mau Forest Reserve, Kenya

Abstract

Anthropogenic pressure and climate change has spurred a global push for more innovative approaches to restore tropical forests, recognizing their crucial role in combating biodiversity loss. In the Eastern Mau Forest in Kenya both single- and multi-species tree restoration methods have been implemented since 2017; however, understanding of ecological performance and their benefits to forest ecosystem remains limited. A comparative study was conducted to assess tree species diversity and soil properties in Eastern Mau forest of the greater Mau complex, one of the five main water towers in Kenya. The experiment focused on Hagenia abyssinica, Podocarpus gracilior, Juniperus procera, Olea capensis, and Prunus africana. Using Line Intersect sampling, study plots were divided into four 10 m x 10 m quadrats. Soil samples, collected from six points in each quadrat at depths of 0-15 cm and 15-30 cm, were combined for analysis of soil organic carbon (SOC), potassium (K), nitrogen (N), and available phosphorus (P). A calibrated rode was used to measure individual tree height while diameter at breast height measured by the use of calibrated diameter tapes in the defined six sample plots and the values were recorded in metres. The multi-species stands showed higher species recruitment with an average stand volume of 1.19 m3 compared to single-species stands (0.85 m3). There was also a 60% increase in forest-specialist species recovery. H. abyssinica showed high dominance (> 5 cm DBH), while the DBH of P. gracilior, J. procera, and P. africana were below 5cm. J. procera in single-species stands exhibited straight, tapered, and thick boles, contrasting with the multi-species approach where H. abyssinica and O. capensis displayed (> 5 cm DBH) and P. gracilior showed smaller sizes with higher mortality rates. P. africana experienced moderate mortality (~20% loss). Analysis of soil samples from the two stands revealed significant differences in organic carbon, nitrogen, and phosphorus concentrations between single and multi-species approaches (p < 0.05). There were significant differences in Soil Organic Carbon, Nitrogen, and Phosphorus among soil profiles (p < 0.05). Additionally, a statistical negative correlation was found between soil organic carbon and nitrogen concentrations (r = 0.759, p = 0.0238), indicating a dependency of nitrogen on soil organic carbon levels across sampled soil depth layers. These findings will inform better forest restoration by highlighting species approach benefits for soil health and biodiversity