Question: What type of vegetation is in the central region of the country Ferronigerite-2N1S is named after?

full_context: Document 1: Geography of Nigeria: Nigeria, like the rest of West Africa and other tropical lands, has only two seasons. These are the dry season and the rainy season. The dry season is accompanied by a dust laden airmass from the Sahara Desert, locally known as Harmattan, or by its main name, The Tropical Continental (CT) airmass, while the rainy season is heavily influenced by an airmass originating from the south atlantic ocean, locally known as the south west wind, or by its main name, The Tropical Maritime (MT) airmass. These two major wind systems in Nigeria are known as the trade winds.
Document 2: Sahara: To the south, the Sahara is bounded by the Sahel, a belt of dry tropical savanna with a summer rainy season that extends across Africa from east to west. The southern limit of the Sahara is indicated botanically by the southern limit of Cornulaca monacantha (a drought-tolerant member of the Chenopodiaceae), or northern limit of Cenchrus biflorus, a grass typical of the Sahel. According to climatic criteria, the southern limit of the Sahara corresponds to the 150 mm (5.9 in) isohyet of annual precipitation (this is a long-term average, since precipitation varies annually).
Document 3: Chad: Chad has several regions: a desert zone in the north, an arid Sahelian belt in the centre and a more fertile Sudanian Savanna zone in the south. Lake Chad, after which the country is named, is the largest wetland in Chad and the second - largest in Africa. The capital N'Djamena is the largest city.
Document 4: Nigeria: The name "" was taken from the Niger River running through the country. This name was coined in the late 19th century by British journalist Flora Shaw, who later married Lord Lugard, a British colonial administrator. The origin of the name "Niger", which originally applied only to the middle reaches of the Niger River, is uncertain. The word is likely an alteration of the Tuareg name "egerew n-igerewen" used by inhabitants along the middle reaches of the river around Timbuktu prior to 19th-century European colonialism.
Document 5: Sahara: To the north, the Sahara skirts the Mediterranean Sea in Egypt and portions of Libya, but in Cyrenaica and the Maghreb, the Sahara borders the Mediterranean forest, woodland, and scrub ecoregions of northern Africa, all of which have a Mediterranean climate characterized by hot summers and cool and rainy winters. According to the botanical criteria of Frank White and geographer Robert Capot-Rey, the northern limit of the Sahara corresponds to the northern limit of date palm cultivation and the southern limit of the range of esparto, a grass typical of the Mediterranean climate portion of the Maghreb and Iberia. The northern limit also corresponds to the 100 mm (3.9 in) isohyet of annual precipitation.
Document 6: Nigeria: The Niger Delta Nembe Creek Oil field was discovered in 1973 and produces from middle Miocene deltaic sandstone-shale in an anticline structural trap at a depth of 2–4 km. In June 2013, the company announced a strategic review of its operations in Nigeria, hinting that assets could be divested. While many international oil companies have operated there for decades, by 2014 most were making moves to divest their interests, citing a range of issues including oil theft. In August 2014, Shell Oil Company said it was finalising its interests in four Nigerian oil fields.
Document 7: Agbaja mine: The Agbaja mine is a large iron mine located in central Nigeria in the Kogi State. Agbaja represents one of the largest iron ore reserves in Nigeria and in the world having estimated reserves of 1.25 billion tonnes of ore grading 48% iron metal.
Document 8: Sawaba: Sawaba was an outgrowth of several sources, and passed through several name changes prior to Niger's independence from France in 1959-1960. Under first the French Union and then the French Community, the colonies of French West Africa began to develop semi-autonomous political institutions in the decade and a half of the French Fourth Republic. Territories, like Niger, were granted consultative posts, first to the colonial government of West Africa (in Dakar), and later in Territorial Assemblies. These bodies had very limited powers, limited seats for Africans, and those elected were chosen by a very restricted electorate.
Document 9: Nigeria: The name Nigeria was taken from the Niger River running through the country. This name was allegedly coined in the late 19th century by British journalist Flora Shaw, she was inspired by the name of the river, in preference to terms such as "Central Sudan". The origin of the name ''Nigeria'' came from the name of the Niger River. The word ( Niger )  is an alteration of the Tuareg name egerew n-igerewen used by inhabitants along the middle reaches of the river around Timbuktu prior to 19th-century European colonialism. Egerew n-igerewen means River of the Rivers.
Document 10: Sahara: The desert comprises much of North Africa, excluding the fertile region on the Mediterranean Sea coast, the Atlas Mountains of the Maghreb, and the Nile Valley in Egypt and Sudan. It stretches from the Red Sea in the east and the Mediterranean in the north to the Atlantic Ocean in the west, where the landscape gradually changes from desert to coastal plains. To the south, it is bounded by the Sahel, a belt of semi-arid tropical savanna around the Niger River valley and the Sudan Region of Sub-Saharan Africa.
Document 11: Sial: The name 'sial' was taken from the first two letters of silica and of alumina. The sial is often contrasted to the 'sima,' the next lower layer in the Earth, which is often exposed in the ocean basins; and the nickel - iron alloy core, sometimes referred to as the ``Nife ''. These geochemical divisions of the Earth's interior (with these names) were first proposed by Eduard Suess in the 19th century. This model of the outer layers of the earth has been confirmed by petrographic, gravimetric, and seismic evidence.
Document 12: Ferronigerite-2N1S: Ferronigerite-2N1S was first discovered in the Kabba provence of central Nigeria in 1944; it was originally named Nigerite. Its name was later changed to nigerite-6H then to nigerite-6T and in 2003 ferronigertie-2N1S was approved by the International Mineralogical Association.
Document 13: Niobium: Columbium (symbol "Cb") was the name originally bestowed by Hatchett upon his discovery of the metal in 1801. The name reflected that the type specimen of the ore came from America (Columbia). This name remained in use in American journals—the last paper published by American Chemical Society with columbium in its title dates from 1953—while niobium was used in Europe. To end this confusion, the name niobium was chosen for element 41 at the 15th Conference of the Union of Chemistry in Amsterdam in 1949. A year later this name was officially adopted by the International Union of Pure and Applied Chemistry (IUPAC) after 100 years of controversy, despite the chronological precedence of the name columbium.  This was a compromise of sorts; the IUPAC accepted tungsten instead of wolfram in deference to North American usage; and niobium instead of columbium in deference to European usage. While many US chemical societies and government organizations typically use the official IUPAC name, some metallurgists and metal societies still use the original American name, "columbium".
Document 14: Geography of Nigeria: With the Intertropical Convergence Zone (ITCZ) swinging northward over West Africa from the Southern Hemisphere in April, heavy showers coming from pre-monsoonal convective clouds mainly in the form of squall lines also known as the north easterlies formed mainly as a result of the interactions of the two dominant airmasses in Nigeria known as the Maritime tropical (south westerlies) and the Continental tropical (north easterlies), begins in central Nigeria while the Monsoons from the south atlantic ocean arrives in central Nigeria in July bringing with it high humidity, heavy cloud cover and heavy rainfall which can be daily occurrence lasting till September when the monsoons gradually begin retreating southward to the southern part of Nigeria. Rainfall totals in central Nigeria varies from 1,100 mm (43.3 in) in the lowlands of the river Niger Benue trough to over 2,000 mm (78.7 in) along the south western escarpment of the Jos Plateau.
Document 15: Nigeria: Everything in between the far south and the far north is savannah (insignificant tree cover, with grasses and flowers located between trees). Rainfall is more limited, to between 500 and 1,500 millimetres (20 and 60 in) per year. The savannah zone's three categories are Guinean forest-savanna mosaic, Sudan savannah, and Sahel savannah. Guinean forest-savanna mosaic is plains of tall grass interrupted by trees. Sudan savannah is similar but with shorter grasses and shorter trees. Sahel savannah consists of patches of grass and sand, found in the northeast. In the Sahel region, rain is less than 500 millimetres (20 in) per year and the Sahara Desert is encroaching. In the dry north-east corner of the country lies Lake Chad, which Nigeria shares with Niger, Chad and Cameroon.
ground_truth: savannah
sub_queries: Who is the Ferronigerite-2N1S named after? Answer: Nigeria
What type of vegetation is in central Nigeria ? Answer: savannah