JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.Abstract. The long-term relationship between major climatic change, vegetation change, and soil development is complex and poorly understood. In northeastern Hungary, for example, geochemical and pollen studies from a lake sedimentary sequence indicate that in the early postglacial, vegetation changed from a coniferous to deciduous forest, and soils from a podzol to brown earth. But which changed first? Did climatic warming result in a transformation from one soil type to another, which in turn resulted in a change in forest composition, or did the vegetation change first and subsequently alter the soil? How long did these soil transformation processes take? And what mechanisms were involved in the development of a brown-earth soil from a podzol? This paper presents the results of a study addressing some of these questions using palaeoecological analyses of a sedimentary sequence from lake Kis-Mohos To in northeastern Hungary. A proposed model for the process by which a podzol becomes transformed into a brown earth is presented, and possible triggering mechanisms are discussed. Results suggest that in northeastern Hungary the postglacial increase in deciduous populations was not consequent on soil type; rather, deciduous trees increased on podzolic soils, and this increase was one of the triggering mechanisms responsible for the development of brown-earth soils.

Conceptual models suggest a link between spatial heterogeneity, diversity, and resilience, but few empirical studies exist to demonstrate such an ecological relationship. In this study, we investigated the nature of spatial heterogeneity and resilience of two forest fragments from Madagascar's highly endangered littoral forest, and two nearby sites in the surrounding ericoid grassland. This ecosystem has been subjected to a number of large environmental disturbances over the last 6000 years, including a late Holocene sea-level rise of 1-3 m above the present level, pronounced drought events, and natural and anthropogenic fires. The aims were to determine the driving mechanisms for heterogeneity and to compare the impact of large environmental disturbances among the four sites.Overall, our results indicate that, contrary to previous assumptions of continuous forest cover, the ecosystem was already spatially heterogeneous prior to the arrival of humans. Differences in groundwater, nutrients, and fires maintained a natural mosaic of forest and open vegetation giving rise to high floristic diversity. The four sites differed significantly in their resilience to climatic disturbances, as measured by compositional turnover and by the timing and extent of biotic recovery. The highly diverse littoral forest reverted more quickly to forest than the surrounding vegetation, which was composed of open Uapaca woodland (a noanalogue community) prior to the formation of the ericoid grassland. Further, species and populations from sites with low nutrients and nitrogen-fixing species as dominants were able to persist despite climatic perturbations, whereas there was higher turnover in the other sites. Overall, minimal extinction occurred in the ecosystem despite widespread landscape transformations. It is suggested that spatial heterogeneity and diversity in southeastern Madagascar may have enhanced species survival during climatic perturbations. Fossil extinction among abundant taxa .1% of total sum (date last observed in fossil record) Fabaceae type (950 cal yr BP), Solanaceae type 2 (850 cal yr BP) Uncaria (1150 cal yr BP), Solanaceae type 2 (1026 cal yr BP), Solanaceae type 3 (976 cal yr BP), Symphonia (950 cal yr BP) Note: SD is standard deviation. Fabaceae type (966 cal yr BP), Euphorbiaceae type 110 (635 cal yr BP), Solanaceae type 2 (403 cal yr BP) none 5 hhttp://bcal.shef.ac.uk/i

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American cotton (Gossypium hirsutum L.), transformed with Bacillus thuringiensis Cry genes (Bt G. hirsutum) that confer resistance to lepidopteran pests, is extensively cultivated worldwide. In India, transgenic Bt G. hirsutum was commercially released in 2002 and by 2014 95% of farmers had adopted Bt G. hirsutum(1). The economic benefits of Bt G. hirsutum over non-Bt G. hirsutum are well documented and include increase in yields, increase in farmers' net revenue and reduction in pesticide application against lepidopteran pests(2-9). However, it is unclear to what extent irrigation influences the performance of Bt G. hirsutum on smallholder farming in India, and if, in the absence of irrigation, growing Bt G. hirsutum provides greater economic benefits for Indian smallholder farmers compared with growing the Asiatic cotton Gossypium arboreum L. Here, we compare the economic impact of growing Bt G. hirsutum with growing G. arboreum under rainfed conditions in the Indian state of Maharashtra, and show that G. arboreum can generate similar net revenue, and thus similar economic benefits for smallholder farmers compared with growing Bt G. hirsutum. We also compare the economic impact of growing Bt G. hirsutum under rainfed conditions with growing Bt G. hirsutum under irrigated conditions and show that even though Bt G. hirsutum yields increase with irrigation, the net revenue does not significantly increase because farmers using irrigation spend significantly more than farmers growing Bt G. hirsutum without irrigation. We conclude that our data provide a broader insight into how socio-economic data needs to be incorporated into agro-ecological data when planning strategies to improve cotton farming in India.

The mean state of the tropical Pacific ocean-atmosphere climate, in particular its east-west asymmetry, has profound consequences for regional climates and for the El Niño/Southern Oscillation variability. Here we present a new high-resolution paleohydrological record using the stable-hydrogen-isotopic composition of terrestrial-lipid biomarkers (δDwax) from a 1,400-year-old lake sedimentary sequence from northern Philippines. Results show a dramatic and abrupt increase in δDwax values around 1630 AD with sustained high values until around 1900 AD. We interpret this change as a shift to significantly drier conditions in the western tropical Pacific during the second half of the Little Ice Age as a result of a change in tropical Pacific mean state tied to zonal sea surface temperature (SST) gradients. Our findings highlight the prominent role of abrupt shifts in zonal SST gradients on multidecadal to multicentennial timescales in shaping the tropical Pacific hydrology of the last millennium, and demonstrate that a marked transition in the tropical Pacific mean state can occur within a period of a few decades.

Social Impact Statement Climate change is expected to disproportionately affect sub‐Saharan Africa in the next century, posing a threat to the livelihoods of smallholder farmers and deepening food insecurity. To adapt to this threat, more climate‐resilient crops need to be brought into the food system; these may be developed through breeding with crop wild relatives with key traits to cope with climate change. Here, we assess the level of open‐access trait documentation of crop wild relatives of 29 important crops, their resilience, how threatened they are in situ, how well they are preserved ex situ and we provide priorities for their conservation and use in breeding programmes. Summary Climate change is projected to adversely affect smallholder agriculture in sub‐Saharan Africa (SSA) over the next century, with many areas becoming unsuitable for growing crops. Breeding programmes using crop wild relatives (CWRs) that are pre‐adapted to projected future climatic conditions may lead to more resilient crops, but their traits have not been screened across a large diversity of CWRs. Furthermore, many are threatened and require greater protection in situ and ex situ to prevent the loss of an important adaptive solution to climate change. A previous ecogeographical study found that 303 out of 836 CWRs of 29 major crops cultivated across SSA may represent priorities for future crop resilience. Here, we assessed the availability of trait information and compared traits between resilient and non‐resilient CWRs. Subsequently, we analysed the conservation status of CWRs in situ and ex situ to set new global priorities for protection. Our findings show that the traits of many CWRs are poorly described, but for those species with better coverage, key differences between resilient and non‐resilient CWRs were identified, including lower plant height amongst resilient CWRs of tree crops (arabica and robusta coffee, mango and cacao) and a higher likelihood of invasive CWRs to be resilient. We found that 14% and 36% of resilient CWRs are threatened in situ and absent from seed collections, respectively. Our study highlights CWR priorities for conservation based on resilience. A concerted international effort is recommended to conserve CWRs and improve agricultural resilience in a changing climate.