Going beyond the green : senesced vegetation material predicts basal area and biomass in remote sensing of tree cover conditions in an African tropical dry forest (miombo woodland) landscape

© The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Environmental Research Letters 12 (2017): 085004, doi:10.1088/1748-9326/aa7242.In sub-Saharan Africa (SSA), tropical dry forests and savannas cover over 2.5 million km2 and support livelihoods for millions in fast-growing nations. Intensifying land use pressures have driven rapid changes in tree cover structure (basal area, biomass) that remain poorly characterized at regional scales. Here, we posed the hypothesis that tree cover structure related strongly to senesced and non-photosynthetic (NPV) vegetation features in a SSA tropical dry forest landscape, offering improved means for satellite remote sensing of tree cover structure compared to vegetation greenness-based methods. Across regrowth miombo woodland sites in Tanzania, we analyzed relationships among field data on tree structure, land cover, and satellite indices of green and NPV features based on spectral mixture analyses and normalized difference vegetation index calculated from Landsat 8 data. From satellite-field data relationships, we mapped regional basal area and biomass using NPV and greenness-based metrics, and compared map performances at landscape scales. Total canopy cover related significantly to stem basal area (r 2 = 0.815, p  60%) at all sites. From these two conditions emerged a key inverse relationship: skyward exposure of NPV ground cover was high at sites with low tree basal area and biomass, and decreased with increasing stem basal area and biomass. This pattern scaled to Landsat NPV metrics, which showed strong inverse correlations to basal area (Pearson r = −0.85, p < 0.01) and biomass (r = −0.86, p < 0.01). Biomass estimates from Landsat NPV-based maps matched field data, and significantly differentiated landscape gradients in woody biomass that greenness metrics failed to track. The results suggest senesced vegetation metrics at Landsat scales are a promising means for improved monitoring of tree structure across disturbance and ecological gradients in African and other tropical dry forests.The project was funded by the US National Science Foundation Partnerships for International Research and Education (PIRE) program, project title 'Ecosystems and Human Well-Being' (Award # 0968211) PI Chris Neill. Additional research and dissertation support was provided to Marc Mayes from Brown University

Nitrogen cycle patterns during forest regrowth in an African Miombo woodland landscape

Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Biogeosciences, 124(6), (2019): 1591-1603, doi:10.1029/2018JG004803.Tropical dry forests in eastern and southern Africa cover 2.5 × 106 km2, support wildlife habitat and livelihoods of more than 150 million people, and face threats from land use and climate change. To inform conservation, we need better understanding of ecosystem processes like nutrient cycling that regulate forest productivity and biomass accumulation. Here we report on patterns in nitrogen (N) cycling across a 100‐year forest regrowth chronosequence in the Tanzanian Miombo woodlands. Soil and vegetation indicators showed that low ecosystem N availability for trees persisted across young to mature forests. Ammonium dominated soil mineral N pools from 0‐ to 15‐cm depth. Laboratory‐measured soil N mineralization rates across 3‐ to 40‐year regrowth sites showed no significant trends and were lower than mature forest rates. Aboveground tree N pools increased at 6 to 7 kg N·ha−1·yr−1, accounting for the majority of ecosystem N accumulation. Foliar δ15N <0‰ in an N‐fixing canopy tree across all sites suggested that N fixation may contribute to ecosystem N cycle recovery. These results contrast N cycling in wetter tropical and Neotropical dry forests, where indicators of N scarcity diminish after several decades of regrowth. Our findings suggest that minimizing woody biomass removal, litter layer, and topsoil disturbance may be important to promote N cycle recovery and natural regeneration in Miombo woodlands. Higher rates of N mineralization in the wet season indicated a potential that climate change‐altered rainfall leading to extended dry periods may lower N availability through soil moisture‐dependent N mineralization pathways, particularly for mature forests.This study depended on the knowledge, insights, and cooperation of many people and institutions. We thank the Millennium Villages Project‐Mbola site for providing introductions to the landscape and village headmen in many regions. We thank the ARI‐Tumbi staff (now TARI‐Tumbi) in Tabora, Tanzania for providing invaluable logistical support in identifying forest regrowth sites and help with labwork in Tabora, Tanzania. We thank other key local organizations, including Tabora Development Foundation Trust (Dick Mlimuka, Oscar Kisanji) and Tanzania Forest Service (Bw. Relingo), for logistical support and transportation. We thank many village headmen and farmers for access to forest sites within their lands for sampling. Finally, we would like to thank the MBL Stable Isotope laboratory and Dr. Marshall Otter for his expertise with producing and interpreting soil and leaf C, N and stable isotope data. This study was funded in part by NSF PIRE Grant OISE 0968211, a Dissertation Support Grant to Marc Mayes from Brown University (2015–2016), and completed with permission and cooperation from the Tanzania Commission on Science and Technology (COSTECH permits 2013‐261‐NA‐2014‐199 and 2015‐183‐ER‐2014‐199). Data and code for analyses can be accessed at a Github repository: https://github.com/mtm17/MiomboN.git.2019-11-0

Comparison of wood basic density and basal area of 5-year-old Acacia crassicarpa, A. julifera, A. leptocarpa, Leucaena pallida and Senna siamea in rotational woodlots trials in western Tabora, Tanzania

Improvement and Culture of Nitrogen Fixing TreesIntroduction The term rotational woodlot connotes a technology which involves growing trees, normally N-fixing, with crops for 2-3 years until the trees out-compete the crops. The woodlot may then be used as a source of fuelwood, building poles or fodder. Soil fertility is also restored during this time until the farmers can cut the trees and start growing crops between the stumps, 4 to 5 years later. The technology was designed to mimic the traditional practice of shifting cultivation by introducing trees into the crop and shrub land with shortened fallow. The cropping and fallow phases take place concurrently. This allows the farmers to crop for an extended period without returning the land to bush fallow. The technology is flexible in the sense that it allows the farmers to adopt both the cropping phase and trees to suit individual needs which diversifies production base, enhances trees and crops productivity and allows a sustainable cropping system (Ramadhani et al. 2002). This technology is being promoted by the World Agroforestry Centre (ICRAF) in collaboration with farmers, Tanzania Forestry Research Institute (TAFORI), and the Agricultural Research and Development Institute (ARDI) Tumbi. The main objective is the provision of fuelwood for tobacco curing and other domestic uses to rural farmers and improvement of soil fertility in the tobacco-cereal land use system of Tabora, Tanzania. It reduces pressure on the 'miombo' woodlands. Despite the potential of this technology, there are few studies on wood basic density and basal area on trees currently used in rotational woodlots. Wood density is highly affected by woodlot manipulation through silvicultural and cultural practices. This study reports comparison of wood basic density and basal area of 5-year-old N-fixing trees of Acacia crassicarpa, A. julifera, A. leptocarpa, Leucaena pallida and Senna siamea grown in rotational woodlots both on-station and in farmers fields

Comparison of wood basic density and basal area of 5-year-old Acacia crassicarpa, A. julifera, A. leptocarpa, Leucaena pallida and Senna siamea in rotational woodlots trials in western Tabora, Tanzania

Improvement and Culture of Nitrogen Fixing TreesIntroduction The term rotational woodlot connotes a technology which involves growing trees, normally N-fixing, with crops for 2-3 years until the trees out-compete the crops. The woodlot may then be used as a source of fuelwood, building poles or fodder. Soil fertility is also restored during this time until the farmers can cut the trees and start growing crops between the stumps, 4 to 5 years later. The technology was designed to mimic the traditional practice of shifting cultivation by introducing trees into the crop and shrub land with shortened fallow. The cropping and fallow phases take place concurrently. This allows the farmers to crop for an extended period without returning the land to bush fallow. The technology is flexible in the sense that it allows the farmers to adopt both the cropping phase and trees to suit individual needs which diversifies production base, enhances trees and crops productivity and allows a sustainable cropping system (Ramadhani et al. 2002). This technology is being promoted by the World Agroforestry Centre (ICRAF) in collaboration with farmers, Tanzania Forestry Research Institute (TAFORI), and the Agricultural Research and Development Institute (ARDI) Tumbi. The main objective is the provision of fuelwood for tobacco curing and other domestic uses to rural farmers and improvement of soil fertility in the tobacco-cereal land use system of Tabora, Tanzania. It reduces pressure on the 'miombo' woodlands. Despite the potential of this technology, there are few studies on wood basic density and basal area on trees currently used in rotational woodlots. Wood density is highly affected by woodlot manipulation through silvicultural and cultural practices. This study reports comparison of wood basic density and basal area of 5-year-old N-fixing trees of Acacia crassicarpa, A. julifera, A. leptocarpa, Leucaena pallida and Senna siamea grown in rotational woodlots both on-station and in farmers fields

Pedological characteristics, general fertility and classification of some benchmark soils of Morogoro District, Tanzania

A detailed characterization of soils earmarked as “Benchmark Soils of Morogoro District”, Tanzania, was carried out to provide data required for planning and execution of soil fertility studies and transfer of agro-technology in the area. Benchmark soils are defined as those occurring in extensive areas and whose comprehensive characterization could contribute substantially to transfer of agro-technology from one area to another. Eleven sites were selected as “Benchmark Sites” of the district based on existing soils information coupled with reconnaissance field soil survey. Soil samples representative of the benchmark soil profiles were described and analysed for their chemical, physical and mineralogical characteristics. Based on these data, general fertility is discussed for the various soils pointing out their potentials and constraints. The data also permitted classification of the soils using international soil classification systems i.e. the United States Department of Agriculture Soil Taxonomy and the FAO-UNESCO Soil Classification System. The soils were classified into different categories reflecting their differences in potentials and constraints and hence use and management. The data obtained through this study presents a substantial base for sound land use planning and will facilitate transfer of technology from one area to another with similar ecological conditions. Key Words: Pedological characteristics, fertility, soil classification, benchmark soils, Morogoro District, Tanzania African Journal of Science and Technology Vol.4(2) 2003: 101-11

Pedological Characteristics, General Fertility and Classification of Some Benchmark Soils of Morogoro District

ABSTRACT:-A detailed characterization of soils earmarked as &quot;Benchmark Soils o

Pedological characteristics, general fertility and classification of some benchmark soils of Morogoro district, Tanzania

A detailed characterization of soils earmarked as “Benchmark Soils of Morogoro District”, Tanzania, was carried out to provide data required for planning and execution of soil fertility studies and transfer of agro-technology in the area. Benchmark soils are defined as those occurring in extensive areas and whose comprehensive characterization could contribute substantially to transfer of agro-technology from one area to another. Eleven sites were selected as “Benchmark Sites” of the district based on existing soils information coupled with reconnaissance field soil survey. Soil samples representative of the benchmark soil profiles were described and analysed for their chemical, physical and mineralogical characteristics. Based on these data, general fertility is discussed for the various soils pointing out their potentials and constraints. The data also permitted classification of the soils using international soil classification systems i.e. the United States Department of Agriculture Soil Taxonomy and the FAO-UNESCO Soil Classification System. The soils were classified into different categories reflecting their differences in potentials and constraints and hence use and management. The data obtained through this study presents a substantial base for sound land use planning and will facilitate transfer of technology from one area to another with similar ecological conditions

Pedological characteristics, general fertility and classification of some benchmark soils of Morogoro district, Tanzania

A detailed characterization of soils earmarked as “Benchmark Soils of Morogoro District”, Tanzania, was carried out to provide data required for planning and execution of soil fertility studies and transfer of agro-technology in the area. Benchmark soils are defined as those occurring in extensive areas and whose comprehensive characterization could contribute substantially to transfer of agro-technology from one area to another. Eleven sites were selected as “Benchmark Sites” of the district based on existing soils information coupled with reconnaissance field soil survey. Soil samples representative of the benchmark soil profiles were described and analysed for their chemical, physical and mineralogical characteristics. Based on these data, general fertility is discussed for the various soils pointing out their potentials and constraints. The data also permitted classification of the soils using international soil classification systems i.e. the United States Department of Agriculture Soil Taxonomy and the FAO-UNESCO Soil Classification System. The soils were classified into different categories reflecting their differences in potentials and constraints and hence use and management. The data obtained through this study presents a substantial base for sound land use planning and will facilitate transfer of technology from one area to another with similar ecological conditions