They are also helpful in extreme years of drought. Climate During 1988, mean maximum temperature ranged from in January to in May, while the mean temperature varied from in December to in June. The diurnal temperature variation ranged from in January to in May. Mean relatively humidity varied from 62% in March to 83.3% in December. The mean annual precipitation is , with rain falling on an average of 36 days per year. In 1988, only of rain fell during 32 days. Ecology Flora In an area characterized by sparse vegetation, the park is the only spot which has dense vegetation and trees. The principal vegetation types are tropical dry deciduous forests intermixed with dry grasslands. Where the forest has degraded, the greater part of the area is covered with shrubs and medium-sized trees. The park is a freshwater swamp and is flooded during the monsoon. The rest of the area remains dry. Forests, mostly in the north-east of the park, are dominated by kalam or kadam (Mitragyna parvifolia), jamun (Syzygium cumini) and babul (Acacia nilotica). The open woodland is mostly babul with a small amount of kandi (Prosopis cineraria) and ber (Zizyphus). It is unlikely that the site would support such numbers of waterfowl as it does without the addition of water from Ajan Bund, a human-made impoundment. Soils are predominantly alluvial, some clay has formed as a result of the periodic inundations. The open woodland is mostly babul with a small amount of kandi and ber. Scrublands are dominated by ber and karira (Capparis decidua). Piloo (Salvadora oleoides and Salvadora persica) are also present in the park and happens to be virtually the only woody plants found in areas of saline soil. The aquatic vegetation is rich and provides a valuable food source for waterfowl. During 2007 and 2008 attempts were made to eradicate the mesquite Prosopis juliflora and specimens of the asteraceous genus Cineraria to prevent the park being overrun with these invasive species and to assist natural vegetation in recovering. Fauna Macro invertebrates such as worms, insects, and mollusks, though more abundant in variety and numbers than any other group of organisms, are present mostly in aquatic habitats. They are food for many fish and birds, as well as some animal species, and hence, constitute a major link in the food chain and functioning of the ecosystem. Land insects are in abundance and have a positive