LICHEN GROWTH RATES ON GLACIER FORELANDS IN SOUTHERN NORWAY: PRELIMINARY RESULTS FROM A 25-YEAR MONITORING PROGRAMME     

BY HAZEL E. TRENBIRTH  JOHN A. MATTHEWS 《Geografiska Annaler: Series A, Physical Geography》2010,92(1):19-39

A unique 25-year lichen growth monitoring programme involving 2,795 individuals of the Rhizocarpon subgenus at 47 sites on 18 glacier forelands in the Jotunheimen–Jostedalsbreen regions of southern Norway is reported. The data are used to address fundamental questions relating to direct lichenometry: spatial and temporal variability in lichen growth rates, climatic effects on lichen growth rates, lichen growth models, and implications for lichenometric dating. Mean annual (diametral) growth rate ranged from 0.43 to 0.87 mm yr⁻¹ between sites, which is attributed primarily to local habitat differences. Interannual variability in annual mean growth rate exceeded 1.0 mm yr⁻¹ at some sites. Annual mean growth rates for all sites combined varied from 0.52 to 0.81 mm yr⁻¹ and was positively correlated with annual mean temperature and winter mean temperature (both r = 0.64, p <0.005) but not with summer seasonal temperature: positive correlations with annual and winter precipitation were less strong and the correlation with summer precipitation was marginally significant (r = 0.41 p <0.10). Growth-rate models characterized by annual growth rates that remain approximately constant or increase with lichen size up to at least 120 mm tended to fit the data more closely than a parabolic model. This is tentatively attributed to a long 'linear/mature' phase in the growth cycle. Comparison with growth rates inferred from indirect lichenometry suggest that such high measured growth rates could not have been maintained over the last few centuries by the largest lichens used in southern Norway for lichenometric dating. Several hypotheses, such as the effects of competition and climate change, which might explain this paradox, are discussed.  相似文献   

WHAT'S IN A NAME? LINGUISTICS,GEOGRAPHY, AND TOPONYMS*     

LISA RADDING  JOHN WESTERN 《Geographical review》2010,100(3):394-412

In differing ways, linguistics and geography each observes that a name's significance is connected to a society. According to lexical theory, a word is arbitrary: Its sound and meaning have no intrinsic link; its function is grammatical. Names are, however, special words. We bestow names based on how they sound or on what they may already have come to represent; names are not arbitrary. In turn, toponyms are special names, and as example we discuss a specific one, “New Orleans.” Far from an arbitrary pairing of form and meaning, this toponym reveals that names reflect the experience of the people who use them.  相似文献   

THE CHANGING LOCATION OF TRADE AND SERVICES IN GUADALAJARA,MEXICO, 1994–2004*     

JOHN HARNER 《Geographical review》2010,100(4):494-520

The location of trade and services in Guadalajara, Mexico, is in flux as suburban commercial centers compete with the traditional downtown for new businesses and employment. Since the mid‐1990s a factor driving the change has been the introduction of American‐style big‐box retailers, corporate franchise supermarkets, and large suburban shopping malls. In this article I analyze the changing patterns of commercial and service businesses and employment from 1994 to 2004 in order to compare suburban and urban growth. My analysis includes comparative measures of change in neighborhoods immediately surrounding Walmart stores and by disaggregated types of commercial districts. Results indicate that a complementary relationship has developed: Suburbs are increasingly strong in the services, but the downtown remains a commercial hub. Moreover, some traditional small vendors in close proximity to Walmart may suffer, but growth in employment and in the service sector near Walmarts is high.  相似文献   

RIVER BLINDNESS REVISITED*     

JOHN M. HUNTER 《Geographical review》2010,100(4):559-582

My hypothesis on onchocerciasis, or river blindness, appeared in the Geographical Review of 1966. It led to an invitation from the World Health Organization in 1972 to revisit the problem area for two months to provide information to assist in the planning of a twenty‐year program of intervention. This article presents unpublished maps selected from my 1972 report. The issues discussed have relevance today regarding international health projects, air‐mass climatology, and human geography.  相似文献   

GEOMORPHOLOGY OF THE LAKE SHEWA LANDSLIDE DAM,BADAKHSHAN, AFGHANISTAN,USING REMOTE SENSING DATA     

JOHN F. SHRODER JR  BRANDON J. WEIHS 《Geografiska Annaler: Series A, Physical Geography》2010,92(4):469-483

Lake Shewa in northeastern Badakhshan, Afghanistan, was dammed sometime in antiquity when a large rock avalanche (sturzstrom) from the fault‐shattered and strongly weathered Archean gneisses of the Zirnokh peaks to the north moved into the Arakht River valley. This rock avalanche dammed up the river and its tributaries to a dam thickness of c. 400 m, producing a 12‐km‐long lake that is as much as 270 m deep, leaving c. 80 m of freeboard to the top of the dam. At least four separate instances of slope failure have been mapped at the site of the landslide dam, as well as a rock glacier, using remotely sensed data, historical maps, and Google Earth?. Spring seepage through the dam face has caused several recent subsidiary debris slides, which if continued at a large enough scale for long enough, or with additional seismicity from the active strike‐slip faults that cross beneath the landslide dam, could threaten its integrity. Otherwise the clean water that emerges from the dam face could be the source of an unvarying mini‐hydroelectric power source, in addition to the agricultural irrigation that it provides at the present time.  相似文献