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Black cherry occupies a key position in the dynamics of oak (Quercus spp.) forests in southern Wisconsin. Its relative importance in sapling and small—tree sizes averaged over 50%, and in some stands it was the only species in these strata. Age analysis of 854 cores showed that 58% of all black cherry stems were established between 1931 and 1941. The appearance of large amounts of black cherry in the 1930 decade was the result of drought and livestock—feed shortages. The latter were especially severe in 1934 and 1936 and resulted in large—scale disturbance of forests through grazing and possibly extensive cutting of forests for foliage. The presence of a strong shrub component exerted a major influence on the dynamics of the oak forest. An inverse relationship existed between overstory tree basal area and the importance of shrubs. Although density and cover of tree seedlings were independent of tree basal area and shrub cover, seedling numbers were insufficient for adequate restocking of most stands. In clear—cut forests the shrub layer was extensive, and regrowth of trees was largely confined to stump sprouts. Shrubs in disturbed forests averaged 38,635 stems/acre, 4,535 square inches basal area/acre, and 145.8% cover. In undisturbed forests, shrub competition (average 16,231 stems/acre, 1,036 square inches basal area/acre, and 51.4% cover) largely precluded seedling establishment by tree species, and maximum basal area levels in these forests were not maintained. Growth and survival of black cherry in the understory depended on the complex interaction of environmental factors. Tree overstory basal area and soil available water were the most significant factors controlling its vigor. Suppressed stems of cherry were as old as 60 years. Growth patterns in stem cores showed that stems responded to release after 39 years of suppression. The capacity of black cherry to develop basal sprouts and the occurrence of light intensities greater than 1,200 ft—c in the understory greatly aided its survival in this stratum. The important role of black cherry in the dynamics of the oak forests was based on opportunistic characteristics including widespread dispersal, delayed germination of seeds, and flexible seedbed requirements. Forest conditions, such as the isolation of forests as woodlots, pioneer environmental conditions, and widespread disturbance, predisposed invasion by opportunistic species. Dynamic processes were characterized by general rather than gradient compositional changes. Patterns of replacement were not orderly and predictable, but irregular as a result of chance dispersal and local catastrophe. Although not uncommon in oak forests in the northeastern United States, invasion by Acer saccharum is not occurring in southern Wisconsin. Succession to Acer—Tilia is confined to specific sites. The overall existing pattern is one of increasing diversity typical of many pioneer communities in an early phase of colonization.

Euro-American settlement of the Inland West has altered forest and woodland landscapes, species composition, disturbance regimes, and resource conditions. Public concern over the loss of selected species and unique habitats (e.g., old-growth) has caused us to neglect the more pervasive problem of declining ecosystem health. Population explosions of Wees, exotic weed species, insects, [Hawonh co-indemng cnuy noel: "H~storeal and Antlclptcd Changes m Forest Ecosystems of rhc Inland Wcrt of rhc Un~ted Slates." Covlnnton. W. Wallax el al Cppubllshcd s~muhaJvously m lhc Journnl of Susroinable Farrsfry (Thc ~a k o r ( h Rcss, I n .

The ticks Rhipicephalus ( Boophilus ) annulatus and R . ( B .) microplus , commonly known as cattle and southern cattle tick, respectively, impede the development and sustainability of livestock industries throughout tropical and other world regions. They affect animal productivity and wellbeing directly through their obligate blood-feeding habit and indirectly by serving as vectors of the infectious agents causing bovine babesiosis and anaplasmosis. The monumental scientific discovery of certain arthropod species as vectors of infectious agents is associated with the history of research on bovine babesiosis and R . annulatus . Together, R . microplus and R . annulatus are referred to as cattle fever ticks (CFT). Bovine babesiosis became a regulated foreign animal disease in the United States of America (U.S.) through efforts of the Cattle Fever Tick Eradication Program (CFTEP) established in 1906. The U.S. was declared free of CFT in 1943, with the exception of a permanent quarantine zone in south Texas along the border with Mexico. This achievement contributed greatly to the development and productivity of animal agriculture in the U.S. The permanent quarantine zone buffers CFT incursions from Mexico where both ticks and babesiosis are endemic. Until recently, the elimination of CFT outbreaks relied solely on the use of coumaphos, an organophosphate acaricide, in dipping vats or as a spray to treat livestock, or the vacation of pastures. However, ecological, societal, and economical changes are shifting the paradigm of systematically treating livestock to eradicate CFT. Keeping the U.S. CFT-free is a critical animal health issue affecting the economic stability of livestock and wildlife enterprises. Here, we describe vulnerabilities associated with global change forces challenging the CFTEP. The concept of integrated CFT eradication is discussed in reference to global change.

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Transboundary zoonotic diseases, several of which are vector borne, can maintain a dynamic focus and have pathogens circulating in geographic regions encircling multiple geopolitical boundaries. Global change is intensifying transboundary problems, including the spatial variation of the risk and incidence of zoonotic diseases. The complexity of these challenges can be greater in areas where rivers delineate international boundaries and encompass transitions between ecozones. The Rio Grande serves as a natural border between the US State of Texas and the Mexican States of Chihuahua, Coahuila, Nuevo León, and Tamaulipas. Not only do millions of people live in this transboundary region, but also a substantial amount of goods and people pass through it everyday. Moreover, it occurs over a region that functions as a corridor for animal migrations, and thus links the Neotropic and Nearctic biogeographic zones, with the latter being a known foci of zoonotic diseases. However, the pathogenic landscape of important zoonotic diseases in the south Texas–Mexico transboundary region remains to be fully understood. An international perspective on the interplay between disease systems, ecosystem processes, land use, and human behaviors is applied here to analyze landscape and spatial features of Venezuelan equine encephalitis, Hantavirus disease, Lyme Borreliosis, Leptospirosis, Bartonellosis, Chagas disease, human Babesiosis, and Leishmaniasis. Surveillance systems following the One Health approach with a regional perspective will help identifying opportunities to mitigate the health burden of those diseases on human and animal populations. It is proposed that the Mexico–US border along the Rio Grande region be viewed as a continuum landscape where zoonotic pathogens circulate regardless of national borders.

Since 1977, the extent of forest wildfires in the boreal and western regions of North America increased 6- to 9-fold over long-term trends, and an estimated 132 × 106 ha of temperate and boreal forest burned across the northern hemisphere. Emissions during and after burning may have been a significant feedback to global warming. Simulated carbon budgets indicated a hemispheric release of 1.4 Pg C during burning and 4.1 Pg C gross from CO2 fluxes postfire. The total release (5.5 Pg C) was 43% of the biospheric CO2 release to the atmosphere, 1977–1990. Over the next century (1991–2090), continuing emissions from wood and soil decomposition will release an additional 6.9 Pg C gross. A large CO2 release was contrary to assumptions of little net carbon flux in the temperate and boreal forests. The pattern of attenuated CO2 release in northern forests also contrasted with sharp emission peaks in tropical deforestation. A simulation experiment indicated that the CO2 pulse from direct emissions per unit area was 10-fold larger in tropical deforestation than in northern forest wildfires on average; postfire release in the northern systems, however, was about 10 times longer in duration and only slightly less overall than in tropical deforestation fires.

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