Distribution, density and impact of invasive plants in Lake Nakuru National Park, Kenya

摘要

AbstractInvasive plants have invaded swathes of grasslands in Lake Nakuru National Park thus necessitating the Park management to institute measures to control them. Despite this, information on the status and impact of invasive plants in these grasslands is lacking. Six grassland types were identified and assigned random numbers. Five study sites were then randomly selected from each grassland type. The Point-Centre Quarter method was used to determine the distribution and density of seven major invasive plants, whilst their impact was assessed by comparing biomass and crude protein content of important forage grasses in invaded and noninvaded grasslands. Results show that the distribution of invasive plants did not differ among the grasslands (F5, 30 = 1.47, P = 0.229) but their densities differed among the plants (F6, 30 = 20.99, P < 0.001). The mean biomass in invaded and noninvaded grasslands (22 g m-2 versus 37.2 g m super(-2)) was significantly different (t-test, P < 0.05), while crude protein content of grasses in invaded (7.73, % DM) and noninvaded (9.3, % DM) patches was not significantly different (t-test; P > 0.05). Our results suggest that invasive plants lower grass production and hence might reduce food availability to grazers. ResumeDes plantes invasives ont envahi des etendues de prairies du Parc National du Lac Nakuru, ce qui oblige la gestion du parc a instaurer des mesures pour les controler. Malgre cela, on manque toujours d'informations sur le statut et l'impact des plantes invasives sur ces prairies. On a identifie six types de prairies et on leur a attribue un numero au hasard. On a ensuite choisi au hasard cinq sites d'etude pour chaque type. La methode des quartiers par point centre fut utilisee pour determiner la distribution et la densite de sept plantes invasives importantes, tandis que l'on evaluait leur impact en comparant la biomasse et le contenu en proteine brute des herbes fourrageres importantes dans les prairies envahies et non envahies. Les resultats montrent que la distribution des plantes invasives ne differait pas selon les prairies (F 5,30 = 1,47, P = 0,229), mais que leur densite differait parmi les plantes (F6, 30 = 20.99, P < 0.001). La biomasse moyenne dans les prairies envahies et non envahies (22 g m-2 versus 37.2 g m super(-2)) etait significativement differente (test de t : P < 0,05) alors que le contenu en proteine brute dans les ilots de prairies envahies (7,73, % DM) et non envahies (9,3, % DM) n'etait pas significativement different (Test de t: P > 0,05). Nos resultats suggerent que les plantes invasives diminuent la production herbeuse et pourraient donc reduire la disponibilite de nourriture pour les animaux qui broutent.