Woody Species Composition, Stand Structure and Regeneration Status of Londiani Forest in Kenya

Tropical forests contain diverse ecosystems and provide a home for people, flora and faunal species [1]. These include about 75% of bird species, 68% of mammal species and 80% of amphibian species. Tropical forests harbour over 60% of the world’s vascular plants [2]. Additionally, they are essential in regulating the climate through oxygen production and carbon storage within different carbon pools, and provide livelihoods for millions of people, especially those adjacent communities that entirely depend on them [1,2,3,4]. Consequently, understanding the dynamics of tropical forests and their conservation has gained prominence [5]. Increased political commitments and the global will to reduce the rates of forest destruction and enhance the restoration of degraded forest ecosystems are great evidence that forests are increasingly becoming more widely recognized for their roles as nature-based solutions to many challenges in sustainable development [6,7].

Deforestation and forest degradation within forest ecosystems remain the biggest challenges in forest conservation globally [8,9]. These two processes contribute significantly to the current loss of biodiversity, resulting in increased rates of extinction in important species that play crucial roles in maintaining ecosystems [4]. A total of 420 million hectares of forests is thought to have been lost during the past 30 years due to conversion to other land uses [4]. The primary causes of deforestation, forest fragmentation and the resulting loss in forest biodiversity are currently agricultural expansion and urbanization [10]. Large-scale commercial agriculture and local subsistence agriculture account for most tropical deforestation. It has been demonstrated that the resilience of human food systems and their capacity to adapt to future change depends on biodiversity, which includes dry land shrubs and tree species that are essential in combating desertification in arid lands, especially forest insects; bat species and bird species that are useful for crop pollination; trees with extensive root systems that mitigate soil erosion and conserve fertility; and mangrove species that provide resilience against flooding and storms in coastal areas [11,12]. The role of forests in absorbing and storing carbon and mitigating climate change is becoming increasingly important for the agricultural sector as hazards to food systems and subsequently food security increase [13,14].

Data and information are the keys to the sustainable management of forests [15,16] since they provide the means for planning, monitoring, evaluating, research, growth, yield, biodiversity and wood sales [17,18]. Forest inventories put together to gather information on the status of forest resources in relation to forest management are the primary method of obtaining this information. A list of tree species can help to identify species of particular concern that could be adversely affected by deforestation and forest degradation by providing information on the diversity and richness of the forest [19].

Intense anthropogenic pressures, such as deforestation, habitat degradation and fragmentation, over-exploitation, invasive species, pollution and global climate change, threaten the biodiversity of tropical rainforests [20,21]. These threats may alter the stand structure and composition of forest ecosystems [22,23]. Tropical forest restoration, which models natural regeneration, has been adopted as a strategy for restoring degraded forests, and hence, restoring forest health [24]. The dynamics of the forest ecosystem and the repair of damaged forest areas heavily rely on regeneration [25]. The patterns of regeneration drive the structure and composition of forest ecosystems [26,27]. At various spatial scales, these variables affect the species composition of tropical forests [27,28]. One result of this is an improvement in the stability, resilience and variety of forest ecosystems [29]. A significant number of seedlings must survive for regeneration to be successful, which depends on the site’s predominant microclimate and the intensity of anthropogenic activities. The success of the different growth stages of the seedlings as well as the size class distribution of a tree population is important in the recovery of the forest following disturbances [30]. In the understory of a forest, seedling densities can fluctuate according to the species, types of forests and habitats with gaps and shadows [31,32,33]. Where regeneration is continuous, the size class distribution of species cohorts will tend to exhibit a reverse J-shaped curve [34]. There are a number of studies that have determined patterns of tree species composition and diversity in different forest ecosystems globally, emphasizing the determination of floristic similarity and diversity gradients [35,36]. Similar studies have been reported in the Kakamega tropical rain forest [37] and Mau Forest in Kenya [38], among others. Studies on the woody species composition, the tree diversity and the regeneration status of Londiani Forest, which is a montane forest, are lacking. Therefore, this study sought to determine: i) species composition, tree abundance, species diversity and distribution within different species associations in Londiani Forest, ii) stand structure (stem density across size classes) by important species across species associations of Londiani Forest and iii) the regeneration status of key species in Londiani Forest.