Land ownership and landscape structure: a spatial analysis of sixty-six Oregon (USA) Coast Range watersheds

Patterns of land ownership and forest cover are related in complex and ecologically significant ways. Using a Geographic Information System and regression analysis, we tested for spatial relationships between the structure of land ownership and forest cover across 66 watersheds in the state of Oregon (USA), Coast Range mountains. We found that in these watersheds (1) forest cover diversity increased with land ownership diversity, (2) size of forest patches increased with size of land ownership patches, and (3) connectivity of forest cover increased with connectivity of land ownership. Land ownership structure explained between 29% and 40% of the variability of forest cover structure across these watersheds. Driving this relationship are unique associations among particular ownership classes and various forest cover classes. The USDA Forest Service and the USDI Bureau of Land Management were associated with mature forest cover; private industry was associated with young forest cover; nonindustrial private forest owners were associated with a wide diversity of cover classes. Watersheds with mixed ownership appear to provide greater forest cover diversity, whereas watersheds with concentrated ownership provide less diverse but more connected forest cover. Results suggest that land ownership patterns are strongly correlated with forest cover patterns. Therefore, understanding landscape structure requires consideration of land ownership institutions, dynamics, and patterns.This revised version was published online in May 2005 with corrections to the Cover Date.     

A multi-scale assessment of human and environmental constraints on forest land cover change on the Oregon (USA) coast range

Human modification of forest habitats is a major component of global environmental change. Even areas that remain predominantly forested may be changed considerably by human alteration of historical disturbance regimes. To better understand human influences on the abundance and pattern of forest habitats, we studied forest land cover change from 1936 to 1996 in a 25000 km² landscape in the Oregon (USA) Coast Range. We integrated historical forest survey data and maps from 1936 with satellite imagery and GIS data from 1996 to quantify changes in major forest cover types. Change in the total area of closed-canopy forests was relatively minor, decreasing from 68% of the landscape in 1936 to 65% in 1996. In contrast, large-conifer forests decreased from 42% in 1936 to 17% in 1996, whereas small-conifer forests increased from 21% of the landscape in 1936 to 39% in 1996. Linear regression models were used to predict changes in the proportion of large conifer forest as a function of socioeconomic and environmental variables at scales of subbasins (mean size = 1964 km², n=13), watersheds (mean size = 302 km², n=83), and subwatersheds (mean size = 18 km², n=1325). The proportion of land in private ownership was the strongest predictor at all three spatial scales (partial R² values 0.57–0.76). The amounts of variation explained by other independent variables were comparatively minor. Results corroborate the hypothesis that differing management regimes on private and public ownerships have led to different pathways of landscape change. Furthermore, these distinctive trajectories are consistent over a broad domain of spatial scales.     

Effects of land-cover change on spatial pattern of forest communities in the Southern Appalachian Mountains (USA)

Landscape Ecology - Understanding the implications of past, present and future patterns of human land use for biodiversity and ecosystem function is increasingly important in landscape ecology. We...     

Rate and pattern of forest disturbance in the Klamath-Siskiyou ecoregion,USA between 1972 and 1992

We classified NALC (North American Landscape Characterization) imagery to forest-nonforest and examined forest change between 1972 and 1992 in theKlamath-Siskiyou ecoregion (USA) in relation to land ownership and fifth levelwatersheds. We also analyzed changes in forest patterns by land ownership forthree major river basins within the ecoregion (Eel, Klamath, and Rogue) usingFRAGSTATS. Overall, forests covered 66.8% of the ecoregion in 1972 and 62.1% in1992. Approximately 10.5% of the forest area was disturbed overall, translatinginto an annual disturbance rate of 0.53%. Although public lands accounted for aslightly higher total area of forest disturbance, private lands were cut at aslightly higher rate. Forest disturbance within fifth level watersheds averaged13.2%, but reached as high as 93.2%. For the three river basins where spatialpattern of forest disturbance was analyzed, private lands were already morefragmented than public lands in 1972. Over the 20-year time period, forestfragmentation increased on all ownerships. Fragmentation rates on public landswere high for all basins especially the Rogue. Clearcut logging on privatelandswas generally in larger adjacent tracts, whereas cuts on public lands weregenerally smaller and more dispersed. Our results illustrate the importance ofconsidering landscape change history when planning for effective biodiversityconservation in forested ecoregions and when formulating ecologicallysustainable forest management strategies.This revised version was published online in May 2005 with corrections to the Cover Date.     

Some determinants of the spatio-temporal fire cycle in a mediterranean landscape (Corsica,France)

Based on recent needs to accurately understand fire regimes and post-fire vegetation resilience at a supra-level for carbon cycle studies, this article focusses on the coupled history of fire and vegetation pattern for 40 years on a fire-prone area in central Corsica (France). This area has been submitted since the beginning of the 20^th century to land abandonment and the remaining land management has been largely controlled by frequent fires. Our objectives were to rebuild vegetation and fire maps in order to determine the factors which have driven the spatial and temporal distribution of fires on the area, what were the feed backs on the vegetation dynamics, and the long-term consequences of this inter-relationship. The results show a stable but high frequency of small fires, coupled with forest expansion over the study period. The results particularly illustrate the spatial distribution of fires according to topography and vegetation, leading to a strong contrast between areas never burnt and areas which have been burnt up to 7 times. Fires, when occuring, affect on average 9 to 12% of the S, SE and SW facing slopes (compared to only 2 to 5% for the N facing slopes), spread recurrently over ridge tops, affect all the vegetation types but reburn preferentially shrublands and grasslands. As these fire-proning parameters have also been shown to decrease the regeneration capacity of forests, this study highlights the needs in spatial studies (both in terms of fire spread and vegetation dynamic) to accurately apprehend vegetation dynamic and functionning in fire-prone areas.This revised version was published online in May 2005 with corrections to the Cover Date.     

Predicting the spatial distribution of an invasive plant species (<Emphasis Type="Italic">Eupatorium adenophorum</Emphasis>) in China

Invasive alien species can pose a severe threat to biodiversity and stability of the ecosystems they invade. Predicting distribution patterns of invasive species in regions outside their native range is a fundamental component of early warning systems. Crofton weed (Eupatorium adenophorum Spreng.) was first discovered in the Yunnan Province of China around the 1940s. The well-documented invasion history of this plant species provided the opportunity for us to examine the spatiotemporal patterns of biological invasion by crofton weed. Using the datasets documenting 441 known localities invaded by crofton weed in China over the past 50 years and 23 environmental variables generated by the genetic algorithm for rule-set production (GARP) model, we tested the predictability of crofton weed distribution with a high degree of accuracy. Both the Kappa statistics and the receiver–operator characteristic (ROC) analysis indicated that it is possible to predict the geographical spread of crofton weed in China. Precipitation in the coldest quarter of the year, extremely low air temperature, and maximum annual air temperature strongly influenced the predictions. Our results indicate that crofton weed may break out in Yungui Plateau, Sichuan Basin, southeastern Coastlands, Hainan Island, and Taiwan although currently it is either absent or has only recently been recorded in these regions. Redundancy analysis (RDA) ordination results demonstrated that temperature and precipitation play an important role in confining the spread of crofton weed. Over the past 20 years, crofton weed has spread from subtropical areas with higher annual mean temperature and lower climatic fluctuations to much cooler and dryer areas at higher altitudes. The distribution of crofton weed was restricted mainly to regions with mean annual air temperature ranging from 10 to 22°C and annual precipitation from 800 to 2000 mm. Our results could help in developing and implementing early detection measures to minimize the ecological impacts of crofton weed invasion in China.