Fertility and management strategies of soils in rural and urban forest ecosystems: a review of selected rural and urban forests in Ghana and USA

ABSTRACT

Healthy soils are paramount to forest ecosystems for the provision of resources required to drive net primary productivity. This review provides an overview of rural and urban forest ecosystems in terms of soil fertility and management strategies in select areas. The Bobiri Forest Reserve (BFR), Ghana was chosen as a representative of the rural forest whilst Independence Community Park (ICP), Baton Rouge, Louisiana was selected to represent an urban forest. A literature search on soil fertility and management strategies of rural and urban forest ecosystems was conducted. The history of soil fertility and the management of rural and urban forest soils were concisely discussed. The USDA web soil survey was conducted to identify the soil types and characteristics of the ICP. The soil types of BFR were also identified and discussed. It emerged from the review that urban forests face a high risk of soil degradation through compaction, landfilling, construction, depletion of soil nutrients, loss of capacity to retain soil water, and inhibition of soil carbon sequestration. To ensure that informed management decisions are taken for the development and policy planning of the forest ecosystems, a list of progressive recommendations has been provided including maintaining optimum forest soil conditions that favour regeneration and long-term survival of desired forest vegetation.

KEYWORDS:

• Soil fertility
• rural forest
• urban forest
• ecosystem
• policy planning

1. Introduction

Traditionally, the primary function of soil is its provision as a medium for plant growth and development (Blanco & Lal, 2010). They are the foundation of forest ecosystems that provide the required resources to drive net primary productivity (Horwath & Kuzyakov, 2018). As an essential constituent and environmental factor of the forest ecosystems (Pang et al., 2006), soils promote root growth (Binkley, 2019); store and release carbon (Horwath & Kuzyakov, 2018); promote biological activity (Pouyat et al., 2010); hold, supply and cycle mineral nutrients (Pang et al., 2006); retain and supply water (Kumawat et al., 2016); promote optimum gas exchange (Thiffault, 2019); and regulate earth’s temperature (Lal et al., 2021).

According to FAO, and ITPS (2021), soil fertility is defined as “the ability of a soil to sustain plant growth by providing essential plant nutrients and favourable chemical, physical, and biological characteristics as a habitat for plant growth.” In forest ecosystems, soil fertility is key to the growth and survival of tree species (Mng’ong’o et al., 2021). However, increasing human population with associated increased demand for housing, agriculture, and infrastructure results in land degradation including a decline in soil fertility and overall land quality for forests. The decline of such elements becomes a major biophysical constraint and often threatens the productivity of terrestrial ecosystems (Ranamukhaarachchi & Begum, 2005).

The Bobiri Forest Reserve (BFR) (Figure 1), found within the middle-belt of Ghana lies in the tropical moist semi-deciduous forest zone (Addo-Fordjour & Ankomah, 2017). It is a typical rural forest with a total land area of about 54.6 sq. Km (21.1 sq. Miles). Under the administration of the Forest Research Institute of Ghana (FORIG), the BFR is the largest forest reserve which host several species of indigenous trees, birds and a butterfly sanctuary (Mensah & Adofo, 2013). It also serves as habitat and refugia for many wildlife species including mona monkey, white-nosed monkey, green monkey and black-and-white colobus monkeys. The area experiences tropical rainfall with an annual mean rainfall between 1200 mm and 1750 mm (Forest Research Institute of Ghana, 2011), as well as an annual mean temperature ranging from 22°C to 31°C (Ammal, 2022). The reserve was created and gazetted in 1939 when it was a pristine forest (Foggie, 1947) with lush vegetation and mystifying atmosphere (Mensah & Adofo, 2013) until it encountered different human disturbances (Baffour-Ata et al., 2021). Management of the reserve over the years has sectionalised BFR under four (4) main designated use namely; butterfly sanctuary, deforested site (logged-over area of the forest), forest production site and the forested site (a protected old growth forest) (Addo-Danso et al., 2018).

Figure 1. A map of Bobiri forest reserve.

On the other hand, is the Independence Community Park (ICP), an urban forest located in the center of East Baton Rouge Parish, Louisiana, U.S.A. (Figure 2). With a higher level of maintenance, security and recreational opportunities, the ICP is designed to engage families throughout the day. It covers a land mass of 0.38 sq. Km (0.0015 sq. miles) 96.02 acres. Comparatively, it serves a larger geographic area than a neighbourhood park (Anonymous, 2019) which offers a wide-range of amenities but not limited to arboretum, library, recreation center, pavilion, soccer field, playground, shuffleboard court and an outdoor fitness station.

Figure 2. A satellite map of independence community park.

Several studies have been conducted on rural and urban forest yet little or no attention has been given to soil fertility and management strategies of these two (Independence Community Park and Bobiri Forest Reserve) forest ecosystems (Jaramillo & Murray-Tortarolo, 2019; Knoepp et al., 2019; Osman, 2012; Ow & Ghosh, 2017; Pouyat & Trammell, 2019; Safford & Vallejo, 2019). This paper therefore seeks to evaluate soil fertility management strategies of a rural forest in Ghana and urban forest in Baton Rouge, Louisiana, U.S.A.. It further explores and examines the various soil fertility management strategies employed in both rural and urban forest ecosystems as well as providing policy recommendations.

2. Methodology

The paper adopted a narrative review approach, providing an overview of soil fertility and management strategies in context-specific of rural and urban forest ecosystems in Ghana and the U.S.A.. It provides insight on the past, current and future understanding of the topic. The narrative in this paper assumes a storyline about management strategies in maintaining soil fertility in rural and urban forest ecosystems. In this context, soil fertility history, urban soils and its management, and rural forest soils management were reviewed.

The narratives were compiled by conducting literature search using multiple research database platforms including SCOPUS (https://www.scopus.com), Google Scholar (https://scholar.google.com) and ScienceDirect (https://www.sciencedirect.com) from date of inception to March, 2022. The key search terms include “soil fertility,” “urban forest soil,” “rural forest soil” and “management strategies” including Ghana and U.S.A. either as prefixes or suffixes. Articles published in the English language with the main focus on soil fertility in urban and rural forests conducted across the globe were considered. Most importantly, those published in languages other than English were excluded. The compiled narratives further provided the basis for reviewing soil fertility management in Bobiri Forest Reserve and Independence Community Park.

3. History of soil fertility

3.1. History of soil fertility in the global context

The concept of soil fertility was commonly referred to the soil physical properties rather than the chemical properties during ancient Rome and Greece until the “theory of salt” was published in 1580 (Palissy, 1880). At the time, the assumption was that organic materials of similar nature nourished the plants. The publication was considered by historians of soil science as forebear of the mineral theory. Nonetheless, Palissy’s definition of salt not being strictly mineral raised questionable opinions as Van Helmont, and several others, shared Palissy’s ideas about the role of soil as a simple source of water and mineral nutrients for the plant (Feller et al., 2012).

In the eighteenth century, “humus” was considered soil, and many propounded theories about nutrition of plants were based on the belief that plants solely relied on humus for supply of carbon. Consequently, some authors adopted ambiguous terminology and referred to it as “juices,” “oils,” or “bituminous substances” (Feller, 1997b, 1997b). Tull (1733) propounded a theory dubbed “new agriculture and fertilization” that hinged on soil tillage because there was a belief that plant growth was dependent on soil particles as source of food. In this light, the soil structure had to be broken down in fine form to ensure quick and safe uptake by plant roots.

However, several scientists – all cited in Feller et al. (2012), rejected these propositions and demonstrated the role of light and origin of carbon during photosynthesis in a rigorous experimentation fashion. Throughout history, theories about soil fertility and plant nutrition remain widely varied. However, almost all laud the importance of soil humus and soil organic matter’s function in facilitating plant nutrition and growth.

3.1.1. History of soil fertility in the US context

The history of forest soil fertility in the United States has been shaped by a combination of natural processes, indigenous land management practices, European colonization, agricultural expansion, and modern conservation efforts. Before European colonization, Native American tribes practiced various forms of land management that influenced soil fertility (Varanasi, 2021). Many indigenous communities practiced a form of shifting cultivation, where they cleared small patches of land for cultivation and allowed cleared areas to revert to forest while they moved to new plots. This approach allowed soil fertility to naturally regenerate. With the arrival of European settlers, significant changes occurred in land use and agriculture. European colonists cleared large areas of forests for farming, leading to soil erosion and degradation in some regions (Brevik et al., 2017). The introduction of new crops and livestock altered soil nutrient dynamics and led to changes in soil fertility (Brevik et al., 2018; McGrath et al., 2014). During the 19th century, the US experienced westward expansion and rapid agricultural development. The demand for fertile land led to extensive deforestation and soil degradation in certain areas. Practices such as monocropping and lack of soil conservation methods contributed to soil fertility decline. The 1930s saw the Dust Bowl, a severe ecological disaster caused by prolonged drought and improper land management practices. The combination of drought, soil erosion, and wind erosion resulted in widespread soil degradation and fertility loss (McGrath et al., 2014). In response, the US government-initiated soil conservation programs and established agencies like the Soil Conservation Service (now the Natural Resources Conservation Service) to promote sustainable land management practices (United States Department of Agriculture, N. R. C. S., 2005). Since the mid-20th century, there has been a growing emphasis on sustainable land management and conservation. Efforts to prevent soil erosion, improve soil fertility, and promote reforestation have been a priority. Agroforestry, cover cropping, crop rotation, and reduced tillage techniques have been promoted to enhance soil fertility and prevent degradation. However, urban soils in Independence Community Park present a challenge to tree growth due to the lack of distinguishable structure, being permeable to air and water infiltration, and can contain toxic substances detrimental to plants. The history of forest soil fertility in the US is marked by periods of soil degradation due to improper land use practices, followed by efforts to restore and maintain soil health through conservation and sustainable management practices. These efforts continue to be important for ensuring the long-term fertility and productivity of US forests and agricultural lands.

3.1.2. History of soil fertility in Ghana

Forest soil fertility history in Ghana is closely intertwined with the country’s agricultural practices, land use changes, and environmental factors. Before European colonization, indigenous communities in Ghana practiced shifting cultivation and agroforestry (Brammer, 1948; Foggie, 1947). They utilized the fertile forest soils for subsistence agriculture, growing crops like yams, plantains, and cocoa. These practices maintain soil fertility through natural nutrient cycling and organic matter decomposition. During the colonial era, European powers established control over various parts of West Africa, including Ghana. This led to changes in land use patterns, as colonial powers introduced cash crops like cocoa and introduced commercial agriculture practices. The cultivation of cocoa, in particular, became a significant part of Ghana’s economy, leading to changes in forested areas to accommodate cocoa farms. After gaining independence in 1957, Ghana continued to focus on agriculture as a key sector of its economy. Cocoa remained a major export, and various governments implemented policies to promote agricultural expansion. This often led to deforestation and soil degradation, as forests were cleared for agricultural purposes without proper soil conservation measures (Adjei-Gyapong & Asiamah, 2002). In the latter half of the 20th century, increasing environmental awareness led to efforts to conserve Ghana’s forests and address soil fertility issues. The government and various organizations started promoting sustainable agricultural practices, reforestation, and soil conservation techniques. Agroforestry systems, which combine trees with crops, were introduced to improve soil fertility and prevent erosion. In recent decades, Ghana has faced challenges such as population growth, urbanization, and deforestation, which have all impacted forest soil fertility. This is evident in the Bobiri Forest Reserve where trees are often cut down for timber, disrupting the ecosystem and leading to habitat loss for many species as well as resulting in soil erosion and changes in water flow. Also, there are unauthorized human settlements, agriculture, and other activities can encroach upon the boundaries of the forest reserve. Unsustainable logging, mining, and agricultural expansion have contributed to soil degradation and loss of biodiversity (Effland et al., 2009; Obeng, 1971). Efforts have been made to address these issues through stricter regulations, community-based conservation projects, and the promotion of sustainable land management practices. Overall, the history of forest soil fertility in Ghana reflects the complex interactions between human activities, environmental changes, and the pursuit of economic development. Efforts to maintain and enhance forest soil fertility continue to be crucial for the sustainability of agriculture, biodiversity, and the overall well-being of the country.

3.2. Soil types and characteristics of independence community park

The United States Department of Agriculture Web Soil Survey (WSS) was employed in the identification of soil types in the Independence Community Park. The USDA Web Soil Survey is a user-friendly and interactive web-based platform (https://websoilsurvey.sc.egov.usda.gov/) that provides access to detailed soil information for various geographical locations within the United States. The tool is valuable for land planners, farmers, environmentalists, and anyone interested in understanding the soil characteristics of a specific area. The area of interest (AOI) was determined using the geographic coordinates of the ICP (Figure 3).

Figure 3. Area of interest interactive map.

After defining the area of interest, a soil map of the location was generated displaying different soil types and their boundaries within the specified area (Figure 4).

Figure 4. Custom soil resource map of Independence Community Park.

The soil types identified at the Independence Park are Calhoun silt loam (CcA), Deerford-Verdun complex (DaA) and Oprairie silt (OpA) (Table 1).

Table 1. Characteristics and soil types of Independence Community Park.

Soil Type Symbol	Soil Type Name	Acres in Area of Interest (AOI)	Percentage of Area of Interest (AOI)
CcA	Calhoun silt loam	0.1	0.1%
DaA	Deerford-Verdun complex	2.3	3.1%
OpA	Oprairie silt	40.2	53.5%
UrA	Urban land	32.5	43.2%
Totals for Area of Interest		75.1	100.0%

Calhoun silt loam covers a very small portion of the AOI, with only 0.1 acres (0.1%) of the total area (Table 1). This indicates that Calhoun silt loam is a minor component of the overall soil composition in the AOI. It is the least in terms of the soil components of the area yet very beneficial to plant growth. The Calhoun silt loam is primarily composed of silt, with some influence from sand and clay particles (United States Department of Agriculture, N. R. C. S., 2005). It has a balanced composition of silt, sand, and clay, providing the soil with a moderately fine texture. This texture allows for good water and nutrient retention while also allowing for reasonable drainage (Soil Survey Staff, 2003). CcA exhibits moderate to good drainage properties, facilitating proper water movement through the soil profile and reducing the risk of waterlogging (United States Department of Agriculture, N. R. C. S., 2005). Due to its silt content, CcA has a relatively high water-holding capacity. This means it can retain moisture well, providing a steady supply of water to plants. This can be beneficial for supporting vegetation during periods of drought. They are often fertile and can support a wide range of crops and plants. They have a good balance of mineral content, organic matter, and nutrients that contribute to plant growth. CcA is likely easy to work with, as its balanced texture makes it relatively friable (crumbly) and malleable. This makes it suitable for agricultural activities such as planting, cultivation, and tillage. However, they are generally susceptible to erosion, especially when left bare or inadequately managed (Stiles, 2014). Soil conservation practices are important to prevent erosion and maintain soil health.

The Deerford-Verdun complex (DaA) covers a larger area compared to Calhoun silt loam, accounting for 2.3 acres (3.1%) of the AOI (Table 1). This soil type is more prevalent in the AOI compared to Calhoun silt loam. DaA consists of a combination of soil materials that create a distinct set of soil horizons (United States Department of Agriculture, 2006). Soil horizons are distinct layers within the soil profile, each with its own characteristics. Surface Horizon (A Horizon) is the uppermost layer, often containing organic matter and nutrients. It is influenced by factors like vegetation, climate, and biological activity. Subsurface Horizon (B Horizon) is the layer which is often characterized by the accumulation of materials leached from above, such as minerals, clays, and iron compounds (Soil Survey Staff, 2003). The layer beneath the B horizon, often containing weathered parent material is the Subsoil Horizon (C Horizon). The Bedrock Horizon (R Horizon) is the unweathered rock layer at the bottom of the soil profile. The texture of the Deerford-Verdun complex varies depending on the specific composition of its horizons (United States Department of Agriculture, N. R. C. S., 2008). It may include a mix of sand, silt, and clay particles, contributing to the overall texture and properties of the soil. The drainage characteristics of DaA can vary based on the arrangement of horizons. While some horizons may have better drainage properties, others could contribute to water retention (United States Department of Agriculture, 2012). The different horizons in the complex have varying nutrient contents and availability. The A horizon is the most nutrient-rich due to its organic matter content. The characteristics of the Deerford-Verdun complex influence its suitability for various land uses, such as forestry, agriculture, and construction. These characteristics make the DaA a viable soil type for the land use activities at the Independence Community Park.

Oprairie silt (OpA) is the dominant soil type in the AOI, covering a substantial portion of the area with 40.2 acres or 53.5% of the total AOI (Table 1). This soil type is the most extensive among the ones known to exist in the AOI. It is somewhat a poorly drained soil that is formed during the deposition of loess (United States Department of Agriculture, 2012). OpA soil type exhibits high organic matter content, high water holding capacity, high cation exchange capacity (CEC) and high bulk density (Soil Survey Staff, 1999).

Urban land refers to developed or built-up areas which covers 32.5 acres (43.2%) of the AOI (Table 1). It includes areas with buildings, roads, and other urban infrastructure within the area of interest.

3.3. Bobiri forest reserve’s soil type and characteristics

The soils of Bobiri Forest Reserve have been identified as the forest ochrosols which are typically well-drained soils with a balanced mixture of mineral particles, organic matter, and nutrients (Foggie, 1947; Hall & Swaine, 1981). This soil type is also known as Acrisol (as per the Food and Agriculture Organization’s soil classification system) or Ultisol under the US soil classification system (Adjei-Gyapong & Asiamah, 2002). Forest ochrosols contain a significant amount of organic matter, which is derived from the decomposition of plant and animal materials in the tropical forest environment. This organic matter contributes to the area’s soil fertility by releasing nutrients as it breaks down. The high biological activity in tropical forests aids in the continuous cycling of nutrients within the soil. They are generally well-suited for supporting the lush plant life found in the tropical forests. The presence of organic matter and nutrients supports the growth of a diverse range of plants, from large trees to smaller shrubs, herbs, and ferns.

Forest ochrosols have a moderate to coarse texture which allows for good water infiltration and retention (Brammer, 1948). The soil’s texture and drainage properties help prevent waterlogging, which can be detrimental to many plant species. While forest ochrosols are valuable for plant growth, they can also be vulnerable to erosion, especially when exposed to heavy rainfall or disturbances such as deforestation or improper land management. The protective canopy of the tropical forest plays a crucial role in preventing erosion by reducing the impact of raindrops on the soil surface.

3.4. Urban soils and their management

The geometric rise in global human population has seen town and city dwellers account for about 52% of the world population; a figure projected to increase to 70% by 2050 (United Nations, 2015). Its attendant effect on soils is threatening, as urban soils are considered known sources of greenhouse gases. As the environment gets urbanized, soil carbon depletes, causing the enhancement of carbon fluxes from the soil which worsens ecological and environmental problems (Lal & Stewart, 2017).

Soils found within urban areas are generally regarded as urban soils. They may be found in industrial, mining, military, traffic and urban areas with strong modification in terms of structure, composition and functions by anthropogenic activities (O’Riordan et al., 2021). Craul (1992) defined urban soils as “a soil material having a non-agricultural, man-made surface layer more than 50 cm thick that has been produced by mixing, filling, or by contamination of land surface in urban and sub-urban areas.”

Through biogeochemical and anthropogenic interactions, such as weathering and erosion, urban soils act as sinks of trace nutrients (Huang et al., 2018; Zhang et al., 2020). Due to their proximity to anthropogenic activities that increase elemental cycling, urban forests function with greater carbon (C), nitrogen (N), and other nutrient cycles (Pouyat & Trammell, 2019).

Just as non-urban soils, urban soils provide many ecosystem services for the well-being of humans and urban resilience. The services may include storing nutrients and water, flood mitigation, immobilization of air pollution, providing structural support for infrastructure, buffering the urban heat island effect, and contributing to nutrient cycling and carbon storage (O’Riordan et al., 2021). However, most of these services have been affected by soil degradation through intensive forestry operations (Edmondson et al., 2011). Before Edmondson et al. (2011)’s city wide analysis of urban soils, there was a long-held impression that urban soils are usually of poor quality due to modification and compaction. Their results revealed otherwise, suggesting that urban soils have better physical conditions than agricultural soils.

It is important to note that climate and environmental change affect C and N cycling in urban ecosystems. Against this foregoing, Pouyat and Trammell (2019) predicted that the cycling of C and N in urban ecosystems will be altered in the next decades by multiple environmental stressors both from urban influences (e.g., pollution) and changes in global climate (e.g., drought). Biogeochemical cycles in urban ecosystems are altered directly and indirectly by human activities (Lorenz & Lal, 2009). Due to the heavy metal contamination and compaction, urban soils usually do not favour plant growth, thereby affecting the delivery of essential ecosystem services (Lal & Stewart, 2017). The heavy machinery introduced during lawn mowing causes reduction of soil pore spaces that prevent air and water movement, thereby causing waterlogging and its resultant plant growth inhibition (Shah et al., 2017).

3.5. Rural forest soils management

Almost one-third of earth’s total land area is covered by a highly rich and complex layer called forest soil (Osman, 2012). This layer is key to the survival of most organisms on our planet. Among the goods and services forest soils provide to humans are food, fuel, timber, medicines, water, oxygen, biodiversity, climate and hydrological regulation. In addition to these services are a wealth of spirituality, cultural, and aesthetic benefits (Busse et al., 2019).

Several mechanisms have been employed in the management of soil fertility in rural forest ecosystems. A typical example is biochar; a well-known soil amendment used to improve soil productivity and health especially soils contaminated by heavy metals (Kong et al., 2021). It has the capacity to increase nutrient retention, water storage and microbial activity. Apart from biochar technology, lime has proven to be essential in plant productivity when applied to sites with low pH (Bruckman & Pumpanen, 2019). Long-term forest productivity can be enhanced with application of ash which recycles nitrogen, phosphorous and potassium, as well as limiting off-site waste material deposition (Vance, 1995).

After a major disturbance of forest soils, biodiversity can be enhanced through retention and creation of different habitat types within the affected landscape rather than applying a single restoration approach to the entire area (Prescott et al., 2019).

A study by Mango et al. (2016), explored the claim of agroforestry being the second soil fertility paradigm and the result was in the affirmative considering its cost-effectiveness and ability to replenish soil fertility.

The table describes the structure and characteristics of soil in the forested and deforested sites in the Bobiri Forest Reserve (Table 2). It is a construct from two major studies (Addo-Danso et al., 2018; Ammal, 2022) conducted in the reserve. Addo-Danso et al. (2018) explored changes that occur in root exploitation strategies during a post-logging recovery. However, some soil properties were analysed. On the other hand, Ammal (2022) examined micronutrients in the forested and deforested sites within the Bobiri Forest Reserve. The soil in both study areas of the reserve is acidic. Comparatively, the soil pH in the forested site is higher than that of the deforested site (Table 2). There is a lower concentration of soil organic matter, carbon, nitrogen, available Phosphorous, available Potassium, and CEC in the deforested site than in the forested site. This possibly could be attributed to the removal of forest vegetation which hampers forest soil quality through essential nutrients deficiency and loss.

Table 2. Structural and soil characteristics of forested and deforested sites of the Bobiri Forest Reserve, Ghana.

Soil property	Forested Site (Old growth Forest)	Deforested Site (Logged-over Forest)	Reference
	Mean ± SEM*	Mean ± SEM*
pH (H2O)	5.60 ± 0.06	6.19 ± 0.12	Addo-Danso et al. (2018)
Total Nitrogen (%)	0.40 ± 0.06	0.39 ± 0.07	Addo-Danso et al. (2018)
Organic Carbon (%)	4.02 ± 0.55	3.94 ± 0.59	Addo-Danso et al. (2018)
Organic Matter (%)	6.94 ± 0.94	6.79 ± 1.02	Addo-Danso et al. (2018)
Available Phosphorous (%)	18.55 ± 1.76	15.26 ± 1.31	Addo-Danso et al. (2018)
Available Potassium (%)	120.52 ± 8.96	109.09 ± 8.70	Addo-Danso et al. (2018)
Bulk density (g/cm^3)	0.66 ± 0.09	0.42 ± 0.06	Addo-Danso et al. (2018)
Sand (%)	59.70 ± 1.85	58.30 ± 2.85	Addo-Danso et al. (2018)
Silt (%)	17.60 ± 3.76	18.10 ± 1.60	Addo-Danso et al. (2018)
Clay (%)	22.70 ± 2.70	23.60 ± 4.36	Addo-Danso et al. (2018)
CEC* (cmolc kg^−1)	4.64 ± 0.29	2.00 ± 0.24	Ammal (2022)

SEM* - Standard Error of Means.

CEC* - Cation Exchange Capacity.

4. Perspectives of soil fertility and management strategies on selected rural and urban forest ecosystems

The Independence Community Park is one of the community parks in the East Baton Rouge Parish that receives thousands of visitors annually. This huge reception causes soil compaction thereby reducing rate of water infiltration and drainage which significantly affects plant growth. Because the park is heavily trafficked, it causes soil structural changes where pore spaces are reduced with less aeration and moisture in the soil. Soil microorganisms are also hardly hit in such circumstances. When this happens, it negatively affects seedling emergence and root growth. Edmondson et al. (2011), posits that seedling emergence normally delay due to increased vehicle traffic. Even in the event that seedling emergence pulls through a compacted soil, the stands usually are at higher risk of decreased moisture, predation and diseases.

It is worthy to note that, to the best of the authors’ knowledge no study (research article, review article, unpublished report) of relating to soil fertility and strategies for maintenance thereof has been conducted at the ICP.

On the other hand, the BFR which is under legal protection in Ghana sees a microcosm of visitors that visit the ICP. Visitors to the reserve are normally researchers. Nonetheless, there is an element of soil compaction in a minimal form. Restricted from the public, yet there are pockets of encroachers that illegally farm and fell trees for various economic reasons. Within the fringes of the reserve is well noted as a pathway for cattle herders; the nomadic cattle sometimes stray into the BFR and also cause soil compaction through their hooves when traversing. These activities have dire consequences on the soil fertility of the area.

Interestingly, the trees and crops illegally farmed in the BFR, for example, Leucaena, Acacia and Alnus; cowpeas, groundnut and beans have the capacity of biologically fixing nitrogen into the soil, adding organic matter and nutrients recycling. The nitrogen fixed mutually benefits tree growing and also help in improving soil fertility (Misra, 2011).

Soil compaction of BFR and ICP cannot be eliminated, rather managed. The aforementioned inimical effects of soil compaction can be managed through fertilizer application, addition of topsoil, or a mosaic of sandy mineral fills and soil organic matter, which tends to improve soil aeration, soil moisture, plant root growth and soil fertility. Furthermore, access to these areas must be controlled to prevent exacerbation of soil degradation.

Generally, soil fertility evaluation involves assessing the nutrient content, physical properties, and overall health of soil to determine its capacity to support healthy plant growth and productivity (Sanchez et al., 1997). It is a critical component to soil fertility management. Three main categories of soil fertility assessment are recommended for BFR and ICP. They include soil testing/analysis, plant tissue analysis and visual symptoms of nutrient deficiency. Visually, symptoms of nutrient deficiency can be observed through the appearance of plants for signs of nutrient imbalances (McGrath et al., 2014). Certain nutrient deficiencies manifest as distinct visual cues on plant tissues, such as leaves. For example, a nitrogen deficiency might lead to yellowing of older leaves (chlorosis), while a potassium deficiency could cause leaf edges to appear scorched (Wade, 2010). Magnesium deficiency might lead to interveinal yellowing. These visual symptoms are often specific to the nutrient deficiency and can vary between plant species. While visual symptoms provide immediate indications of potential problems, they are not always definitive, as various factors like diseases, pests, or environmental stress can mimic nutrient deficiencies. This therefore necessitates soil testing/analysis. Soil samples can be collected from various points in the planting area and sent to the laboratory for analysis (Sathyanarayana et al., 2022). The laboratory assesses factors such as nutrient concentrations, cation exchange capacity (CEC), soil pH, available nitrogen, phosphorous and potassium. The results will then determine the soil’s nutrient-holding capacity, its ability to release nutrients to plants, and any potential imbalances or deficiencies. This category of soil fertility assessment is valuable for making informed decisions about nutrient management and fertilizer application. Plant tissue analysis could be imperative when the nutrient content within the plant itself is deficient (McGrath et al., 2014). It can provide insights into the plant’s nutrient uptake and utilization. The process involves collecting representative plant samples, preparing them for analysis, and then using techniques such as spectroscopy or chemical testing to determine the concentration of various nutrients. Comparing the observed nutrient levels to established optimal ranges helps diagnose nutrient deficiencies or imbalances, allowing for targeted fertilization strategies. These three categories of soil fertility evaluation complement each other and collectively provide a comprehensive picture of a plant’s nutrient status and its growing environment. Combining information from plant tissue analysis, soil analysis, and visual symptoms will help forest managers to make informed decisions about nutrient management strategies, ensuring that trees receive the necessary nutrients for healthy growth and optimal yields.

5. Conclusion and policy recommendations

Understanding the dynamics of soil fertility and management strategies offers important insights of relevance to development, planning and policy. Soil fertility if not appropriately managed can lead to adverse risk in terms of poor tree health, bioaccumulation, greenhouse gas emissions and limited soil carbon sequestration.

Based on the current knowledge on rural and urban forest ecosystems, the following are recommended for sustainable forest soil productivity:

• A comprehensive study of the soil structure, soil composition and soil properties of the Independence Community Park must be conducted to bring to the fore soil fertility status of the area. This will provide a baseline for subsequent monitoring and tracking of progress of the area’s fertility.

• As much as possible, the numbers that visit these forests should be controlled. For instance, within a year, the Independence Community Park can be shut down for a period of at least 90 days (3 months) for rehabilitation of the soil and vegetation growth.

• Maintain optimum forest soil conditions that favour regeneration and long-term survival of desired forest vegetation.

• Encourage the use of alternate operating techniques and less impacting tools and equipment to maintain favourable soil productivity.

• Soil amendments such as biochar must be encouraged, since it helps to mitigate the effects of climate change through the process of sequestering carbon within the soil profile and plant growth enhancement.

Acknowledgments

The authors are grateful to Dr. V. Ferchaud, whose inspiration birthed this review article.

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No potential conflict of interest was reported by the author(s).

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.