The effects of seaward distance on above and below ground carbon stocks in estuarine mangrove ecosystems

Mangrove forests have gained recognition for their potential role in climate change mitigation due to carbon sequestration in live trees, and carbon storage in the sediments trapped by mangrove tree roots and pneumatophores. Africa hosts about 19% of the world’s mangroves, yet relatively few studies have examined the carbon stocks of African mangroves. The available studies report considerable differences among sites and amongst the different pools of carbon stocks. None considered the effects of seaward distance. We present details of AGC and SOC carbon stocks for Lindi in Tanzania, and focus on how these values differ with increasing seaward distance and, how our results compare to those reported elsewhere across Africa

A framework to assess forest-agricultural landscape management for socioecological well-being outcomes

Global demand for agricultural products continues to grow. However, efforts to boost productivity exacerbate existing pressures on nature, both on farms and in the wider landscape. There is widespread appreciation of the critical need to achieve balance between biodiversity and human well-being in rural tropical crop production landscapes, that are essential for livelihoods and food security. There is limited empirical evidence of the interrelationships between natural capital, the benefits and costs of nature and its management, and food security in agricultural landscapes. Agroforestry practices are frequently framed as win-win solutions to reconcile the provision of ecosystem services important to farmers (i.e., maintaining soil quality, supporting pollinator, and pest control species) with nature conservation. Yet, underlying trade-offs (including ecosystem disservices linked to pest species or human-wildlife conflicts) and synergies (e.g., impact of ecosystem service provision on human well-being) are seldom analysed together at the landscape scale. Here, we propose a systems model framework to analyse the complex pathways, with which natural capital on and around farms interacts with human well-being, in a spatially explicit manner. To illustrate the potential application of the framework, we apply it to a biodiversity and well-being priority landscape in the Southern Agricultural Growth Corridor of Tanzania, a public-private partnership for increasing production of cash and food crops. Our framework integrates three main dimensions: biodiversity (using tree cover and wildlife as key indicators), food security through crop yield and crop health, and climate change adaptation through microclimate buffering of trees. The system model can be applied to analyse forest-agricultural landscapes as socio-ecological systems that retain the capacity to adapt in the face of change in ways that continue to support human well-being. It is based on metrics and pathways that can be quantified and parameterised, providing a tool for monitoring multiple outcomes from management of forest-agricultural landscapes. This bottom-up approach shifts emphasis from global prioritisation and optimisation modelling frameworks, based on biophysical properties, to local socio-economic contexts relevant in biodiversity-food production interactions across large parts of the rural tropics.Agrisys Tanzania project was funded through BBSRC Global Challenges Research Fund.https://www.frontiersin.org/journals/forests-and-global-changedm2022Zoology and Entomolog

Scenarios of land use and land cover change and their multiple impacts on natural capital in Tanzania

REDD+ (reducing emissions from deforestation, and forest degradation, plus the conservation of forest carbon stocks, sustainable management of forests, and enhancement of forest carbon stocks, in developing countries) requires information on land use and land cover changes (LULCC) and carbon emissions trends from the past to the present and into the future. Here we use the results of participatory scenario development in Tanzania, to assess the potential interacting impacts on carbon stock, biodiversity and water yield of alternative scenarios where REDD+ is effectively implemented or not by 2025, the green economy (GE) and the business as usual (BAU) respectively. Under the BAU scenario, land use and land cover changes causes 296 MtC national stock loss by 2025, reduces the extent of suitable habitats for endemic and rare species, mainly in encroached protected mountain forests, and produce changes of water yields. In the GE scenario, national stock loss decreases to 133 MtC. In this scenario, consistent LULCC impacts occur within small forest patches with high carbon density, water catchment capacity and biodiversity richness. Opportunities for maximising carbon emissions reductions nationally are largely related to sustainable woodland management but also contain trade-offs with biodiversity conservation and changes in water availability

Interactions between canopy structure and herbaceous biomass along environmental gradients in moist forest and dry miombo woodland of Tanzania

We have limited understanding of how tropical canopy foliage varies along environmental gradients, and how this may in turn affect forest processes and functions. Here, we analyse the relationships between canopy leaf area index (LAI) and above ground herbaceous biomass (AGBH) along environmental gradients in a moist forest and miombo woodland in Tanzania. We recorded canopy structure and herbaceous biomass in 100 permanent vegetation plots (20 m × 40 m), stratified by elevation. We quantified tree species richness, evenness, Shannon diversity and predominant height as measures of structural variability, and disturbance (tree stumps), soil nutrients and elevation as indicators of environmental variability. Moist forest and miombo woodland differed substantially with respect to nearly all variables tested. Both structural and environmental variables were found to affect LAI and AGBH, the latter being additionally dependent on LAI in moist forest but not in miombo, where other factors are limiting. Combining structural and environmental predictors yielded the most powerful models. In moist forest, they explained 76% and 25% of deviance in LAI and AGBH, respectively. In miombo woodland, they explained 82% and 45% of deviance in LAI and AGBH. In moist forest, LAI increased non-linearly with predominant height and linearly with tree richness, and decreased with soil nitrogen except under high disturbance. Miombo woodland LAI increased linearly with stem density, soil phosphorous and nitrogen, and decreased linearly with tree species evenness. AGBH in moist forest decreased with LAI at lower elevations whilst increasing slightly at higher elevations. AGBH in miombo woodland increased linearly with soil nitrogen and soil pH. Overall, moist forest plots had denser canopies and lower AGBH compared with miombo plots. Further field studies are encouraged, to disentangle the direct influence of LAI on AGBH from complex interrelationships between stand structure, environmental gradients and disturbance in African forests and woodlands

Interaksjoner mellom struktur, diversitet, næringsstoffer i jord og karbonlagring i Tanzaniansk skog

In recent years, structural components such as woody species richness, diversity, canopies and non-woody lifeforms in tropical forests and woodlands have experienced increasing rates of degradation and deforestation due to agricultural expansion and other land use changes. The decline in plant species diversity in forests and woodlands has negative effects on ecosystem processes and functions such as atmospheric carbon sequestration and mitigations of global climate changes. However, our knowledge on how varieties of structural components interacts with physiographic conditions and anthropogenic disturbances to influence ecosystem processes are limited. This knowledge gap has consequently undermined our understanding of the potential contributions of structural components in enhancing human wellbeing. This thesis consist of series of studies from a moist forest and miombo woodlands in Tanzania. The main aim was to relate structural components, such as tree species richness, canopy, carbon stocks and their interactions, with physiographic conditions, and anthropogenic disturbances. I explore (1) how do tree species richness relates to vertical heterogeneity, mean and depth specific soil nutrient availability. (2) do dominant tree species influence the richness, diversity, evenness and vertical structure heterogeneity of non-dominant tree species? (3) how do tree canopy characteristics relates to herbaceous biomass and tree species richness? (4) how do the aboveground carbon stocks of trees relate to tree species richness, diversity and evenness along gradients of physiographic conditions and anthropogenic disturbances? Using data from vegetation and soil surveys in a series of regression analyses, I showed that variation in tree species richness were better explained by mean than vertical heterogeneity in soil nutrient availability in moist forest, while in miombo woodlands, vertical heterogeneity explained a large part of the variations in tree species richness than mean soil nutrient availability. Nondominant tree species richness, Shannon diversity and evenness had negative linear and nonlinear relationships with the relative abundance of dominant tree species in wet and dry miombo woodlands. Moreover, tree species structure, physiographic conditions and anthropogenic disturbances explained over 50 % of the variations in leaf area index (LAI) and nearly 20 % of the variations in aboveground herbaceous biomass (AGBH) in moist forest and miombo woodlands. Furthermore, aboveground carbon stocks of trees were unimodal, positive or negative linearly related to tree species richness, evenness and abiotic factors in the two vegetation types. X The relationships between structural components, physiographic conditions and anthropogenic disturbances has consequences on ecosystem properties such as carbon storage and sequestration, and biodiversity. Understanding of how structural components interact with environmental conditions and anthropogenic disturbances is a step towards establishing the potential contributions of forest and woodlands to local livelihoods. Thus, management of forests and woodlands in Tanzania require strategies that maintains the existing structural complexity.CCIA

Forests and woodlands of Tanzania : interactions between woody plant structure, diversity, carbon stocks and soil nutrient heterogeneity

In recent years, structural components such as woody species richness, diversity, canopies and non-woody lifeforms in tropical forests and woodlands have experienced increasing rates of degradation and deforestation due to agricultural expansion and other land use changes. The decline in plant species diversity in forests and woodlands has negative effects on ecosystem processes and functions such as atmospheric carbon sequestration and mitigations of global climate changes. However, our knowledge on how varieties of structural components interacts with physiographic conditions and anthropogenic disturbances to influence ecosystem processes are limited. This knowledge gap has consequently undermined our understanding of the potential contributions of structural components in enhancing human wellbeing. This thesis consist of series of studies from a moist forest and miombo woodlands in Tanzania. The main aim was to relate structural components, such as tree species richness, canopy, carbon stocks and their interactions, with physiographic conditions, and anthropogenic disturbances. I explore (1) how do tree species richness relates to vertical heterogeneity, mean and depth specific soil nutrient availability. (2) do dominant tree species influence the richness, diversity, evenness and vertical structure heterogeneity of non-dominant tree species? (3) how do tree canopy characteristics relates to herbaceous biomass and tree species richness? (4) how do the aboveground carbon stocks of trees relate to tree species richness, diversity and evenness along gradients of physiographic conditions and anthropogenic disturbances? Using data from vegetation and soil surveys in a series of regression analyses, I showed that variation in tree species richness were better explained by mean than vertical heterogeneity in soil nutrient availability in moist forest, while in miombo woodlands, vertical heterogeneity explained a large part of the variations in tree species richness than mean soil nutrient availability. Nondominant tree species richness, Shannon diversity and evenness had negative linear and nonlinear relationships with the relative abundance of dominant tree species in wet and dry miombo woodlands. Moreover, tree species structure, physiographic conditions and anthropogenic disturbances explained over 50 % of the variations in leaf area index (LAI) and nearly 20 % of the variations in aboveground herbaceous biomass (AGBH) in moist forest and miombo woodlands. Furthermore, aboveground carbon stocks of trees were unimodal, positive or negative linearly related to tree species richness, evenness and abiotic factors in the two vegetation types. X The relationships between structural components, physiographic conditions and anthropogenic disturbances has consequences on ecosystem properties such as carbon storage and sequestration, and biodiversity. Understanding of how structural components interact with environmental conditions and anthropogenic disturbances is a step towards establishing the potential contributions of forest and woodlands to local livelihoods. Thus, management of forests and woodlands in Tanzania require strategies that maintains the existing structural complexity

Deforestation and Connectivity among Protected Areas of Tanzania

Protected Areas (PAs) in Tanzania had been established originally for the goal of habitat, landscape and biodiversity conservation. However, human activities such as agricultural expansion and wood harvesting pose challenges to the conservation objectives. We monitored a decade of deforestation within 708 PAs and their unprotected buffer areas, analyzed deforestation by PA management regimes, and assessed connectivity among PAs. Data came from a Landsat based wall-to-wall forest to non-forest change map for the period 2002–2013, developed for the definition of Tanzania’s National Forest Reference Emissions Level (FREL). Deforestation data were extracted in a series of concentric bands that allow pairwise comparison and correlation analysis between the inside of PAs and the external buffer areas. Half of the PAs exhibit either no deforestation or significantly less deforestation than the unprotected buffer areas. A small proportion (10%; n = 71) are responsible for more than 90% of the total deforestation; but these few PAs represent more than 75% of the total area under protection. While about half of the PAs are connected to one or more other PAs, the remaining half, most of which are Forest Reserves, are isolated. Furthermore, deforestation inside isolated PAs is significantly correlated with deforestation in the unprotected buffer areas, suggesting pressure from land use outside PAs. Management regimes varied in reducing deforestation inside PA territories, but differences in protection status within a management regime are also large. Deforestation as percentages of land area and forested areas of PAs was largest for Forest Reserves and Game Controlled areas, while most National Parks, Nature Reserves and Forest Plantations generally retained large proportions of their forest cover. Areas of immediate management concern include the few PAs with a disproportionately large contribution to the total deforestation, and the sizeable number of PAs being isolated. Future protection should account for landscapes outside protected areas, engage local communities and establish new PAs or corridors such as village-managed forest areas.publishedVersio