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Dryland ecosystems comprise a balance between woody and herbaceous vegetation. Climate change impacts rainfall timing, which may alter the respective contributions of woody and herbaceous plants on the total vegetation production. Here, we apply 30 years of field-measured woody foliage and herbaceous mass from Senegal and document a faster increase in woody foliage mass (+17 kg ha −1 yr −1 ) as compared to herbaceous mass (+3 kg ha −1 yr −1 ). Annual rainfall trends were partitioned into core wet-season rains (+0.7 mm yr -1 ), supporting a weak but periodic (5-year cycles) increase in herbaceous mass, and early/late rains (+2.1 mm yr −1 ), explaining the strongly increased woody foliage mass. Satellite observations confirm these findings for the majority of the Sahel, with total herbaceous/woody foliage mass increases by 6%/20%. We conclude that the rainfall recovery in the Sahel does not benefit herbaceous vegetation to the same extent as woody vegetation, presumably favoured by increased early/late rains.

The large scale conversion of extensive swidden agriculture to intensive market oriented production of maize in upland areas of South East Asia is a cause of environmental concern. This study investigates how intensive maize cultivation affects soil quality in an upland area of Northern Thailand by comparing commonly used indicators of soil quality in soils from maize fields used at various intensities. Relations between these indicators and concentration of permanganate oxidizable carbon (Pox‐C) – a low cost proxy for soil quality – are also examined. The extent, type and drivers of land use changes between 2002 and 2012 are investigated by classification of high resolution satellite images, interviews, participatory mapping and questionnaires. We document a widespread change from traditional swidden agriculture to intensive cultivation of maize that is mainly brought about by economcic and political drivers. We show that the concentration of Pox‐C in the top soil of the maize fields is closely related to common indicators of soil quality and to farmers' perceptions of soil quality. Most of the other soil quality indicators are negatively – albeit not significantly – related to intensity of maize cultivation. There is a strong negative correlation between intensity of maize cultivation and concentration of Pox‐C in the upper 5 cm of the soil where the Pox‐C concentration declines with a rate of 40 mg year under maize−1. We conclude that Pox‐C is a sensitive indicator of effects of land use intensity on the soil and a useful integrative measure of soil quality. Copyright © 2016 John Wiley & Sons, Ltd.

Global climate change is projected to lead to an increase in both the areal extent and degree of aridity in the world's drylands. At the same time, the majority of drylands are located in developing countries where high population densities and rapid population growth place additional pressure on the ecosystem. Thus, drylands are particularly vulnerable to environmental changes and large-scale environmental degradation. However, little is known about the long-term functional response of vegetation to such changes induced by the interplay of complex human-environmental interactions. Here we use time series of satellite data to show how vegetation productivity in relation to water availability, which is a major aspect of vegetation functioning in tropical drylands, has changed over the past two decades. In total, one-third of tropical dryland ecosystems show significant (P < 0.05) changes in vegetation-rainfall sensitivity with pronounced differences between regions and continents. We identify population as the main driver of negative changes, especially for developing countries. This is contrasted by positive changes in vegetation-rainfall sensitivity in richer countries, probably resulting from favourable climatic conditions and/or caused by an intensification and expansion of human land management. Our results highlight geographic and economic differences in the relationship between vegetation-rainfall sensitivity and associated drivers in tropical drylands, marking an important step towards the identification, understanding and mitigation of potential negative effects from a changing world on ecosystems and human well-being.

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