Large herbivores may alter vegetation structure of semi-arid savannas through soil nutrient mediation

In savannas, the tree–grass balance is governed by water, nutrients, fire and herbivory, and their interactions. We studied the hypothesis that herbivores indirectly affect vegetation structure by changing the availability of soil nutrients, which, in turn, alters the competition between trees and grasses. Nine abandoned livestock holding-pen areas (kraals), enriched by dung and urine, were contrasted with nearby control sites in a semi-arid savanna. About 40 years after abandonment, kraal sites still showed high soil concentrations of inorganic N, extractable P, K, Ca and Mg compared to controls. Kraals also had a high plant production potential and offered high quality forage. The intense grazing and high herbivore dung and urine deposition rates in kraals fit the accelerated nutrient cycling model described for fertile systems elsewhere. Data of a concurrent experiment also showed that bush-cleared patches resulted in an increase in impala dung deposition, probably because impala preferred open sites to avoid predation. Kraal sites had very low tree densities compared to control sites, thus the high impala dung deposition rates here may be in part driven by the open structure of kraal sites, which may explain the persistence of nutrients in kraals. Experiments indicated that tree seedlings were increasingly constrained when competing with grasses under fertile conditions, which might explain the low tree recruitment observed in kraals. In conclusion, large herbivores may indirectly keep existing nutrient hotspots such as abandoned kraals structurally open by maintaining a high local soil fertility, which, in turn, constrains woody recruitment in a negative feedback loop. The maintenance of nutrient hotspots such as abandoned kraals by herbivores contributes to the structural heterogeneity of nutrient-poor savanna vegetation

The effects of land-use change on arthropod richness and abundance on Santa Maria Island (Azores):unmanaged plantations favour endemic beetles

Copyright © Springer Science+Business Media B.V. 2010.We study how endemic, native and introduced arthropod species richness, abundance, diversity and community composition vary between four different habitat types (native forest, exotic forest of Cryptomeria japonica, semi-natural pasture and intensive pasture) and how arthropod richness and abundance change with increasing distance from the native forest in adjacent habitat types in Santa Maria Island, the Azores. Arthropods were sampled in four 150 m long transects in each habitat type. Arthropods were identified to species level and classified as Azorean endemic, single-island endemic (SIE), native, or introduced. The native forest had the highest values for species richness of Azorean endemics, SIEs and natives; and also had highest values of Azorean endemic diversity (Fisher’s alpha). In contrast, the intensive pasture had the lowest values for endemic and native species richness and diversity, but the highest values of total arthropod abundance and introduced species richness and diversity. Arthropod community composition was significantly different between the four habitat types. In the semi-natural pasture, the number of SIE species decreased with increasing distance from the native forest, and in the exotic forest the abundance of both Azorean endemics and SIEs decreased with increasing distance from the native forest. There is a gradient of decreasing arthropod richness and abundance from the native forest to the intensive pasture. Although this study demonstrates the important role of the native forest in arthropod conservation in the Azores, it also shows that unmanaged exotic forests have provided alternative habitat suitable for some native species of forest specialist arthropods, particularly saproxylic beetles

The Role of Gender and Kinship Structure in Household Decision-Making for Agriculture and Tree Planting in Malawi

This study examines household decision-making on various agricultural activities—including tree planting and management—among farming families in Malawi. A mixed-method approach consisting of a household survey (containing 135 married respondents and 16 focus group discussions) was used to analyze the gender dimensions of decision-making and the role of kinship structure. The study found that most decisions in relation to agricultural activities are made either by the husband or by the husband and wife together. However, decisions regarding tree planting and tree management are more often made by the household head alone, and are considered mainly the domain of men. These results were reinforced by the focus group discussions, which also revealed that women do play a role in the implementation of these activities. In patrilineal households decisions were made more often by the husband alone compared to matrilineal families where there was more joint decision-making by husbands and wives together. Decision-making on tree planting by the wife and joint decision-making on tree management resulted in higher densities of trees planted on farms compared to situations where decisions were made by the husband alone

Farmers and forest conservation in Malawi: the disconnect between attitudes, intentions and behaviour

<p>Malawi’s unique flora and fauna are threatened by high levels of deforestation and forest degradation. In addition to the many ecosystem services provided by the country’s forests, most of the rural population of this poor country are highly dependent on forests for provision of food, firewood, medicine, building materials and income. This study examined farmers’ attitudes and behaviour in relation to cutting down forest trees in two rural districts in Malawi using the theory of planned behaviour as a conceptual framework. A survey was administered to 200 household heads in Mzimba and Chiradzulu districts. With strongly negative attitudes, subjective norms and perceived behavioural control, farmers were aware of the negative consequences associated with cutting down forest trees, the lack of social support and obstacles encountered when cutting down forest trees. The intention to cut down forest trees was generally low. However, farmers were highly dependent on forest resources, especially in the north, which is caused by high levels of poverty and a lack of alternative income opportunities. We conclude that poverty alleviation and livelihood diversification are crucial for addressing the overexploitation of forest trees in Malawi.</p