Differences in the summer insulative value of the zonal vegetation mat affect the depth of thaw along the Arctic bioclimate gradient. Toward the south, taller, denser plant canopies and thicker organic horizons counter the effects of warmer temperatures, so that there is little correspondence between active layer depths and summer air temperature. We examined the interactions between summer warmth, vegetation (biomass, Leaf Area Index, Normalized Difference Vegetation Index), soil (texture and pH), and thaw depths at 17 sites in three bioclimate subzones of the Arctic Slope and Seward Peninsula, Alaska. Total plant biomass in subzones C, D, and E averaged 421 g m 2 , 503 g m 2 , and 1178 g m 2 respectively. Soil organic horizons averaged 4 cm in subzone C, 8 cm in subzone D, and 14 cm in subzone E. The average late-August thaw depths in subzones C, D, and E were 44 cm, 55 cm, and 47 cm respectively. Non-acidic soils in equivalent climates generally have shorter-stature sedge-dominated canopies and many frost boils, and consequently have thicker active layers than acidic soils. The trends reported here are useful for palaeo-ecological reconstructions and predictions of future ecosystem changes in the Low Arctic. Climate change will not lead to uniform thickening of the active layer, and could lead to shallower active layers in some presently dry areas due to paludification.
We evaluated the feasibility of using aerial photo-based office methods rather than field-collected data to validate Landsat-based change detection products in national parks in Washington State. Landscape change was performed using LandTrendr algorithm. The resulting change patches were labeled in the office using aerial imagery and a random sample of patches was visited in the field by experienced analysts. Comparison of the two labels and associated confidence shows that the magnitude or severity of the change is a strong indicator of whether field assessment is warranted, and that confusion about patches with lower magnitude changes is not always resolved with a field visit. Our work demonstrates that validation of Landsat-derived landscape change patches can be done using office based tools such as aerial imagery, and that such methods provide an adequate validation for most change types, thus reducing the need for expensive field visits.
Field crews recently collected more than 10 years of classification and mapping data in support of the North Coast and Cascades Inventory and Monitoring Network (NCCN) vegetation maps of Mount Rainier (MORA), Olympic (OLYM), and North Cascades (NOCA) National Parks. Synthesis and analysis of these 6000+ plots by Washington Natural Heritage Program (WNHP) and Institute for Natural Resources (INR) staff built on the foundation provided by the earlier classification work of Crawford et al. (2009). These analyses provided support for most of the provisional plant associations in Crawford et al. (2009), while also revealing previously undescribed vegetation types that were not represented in the United States National Vegetation Classification (USNVC). Both provisional and undescribed types have since been submitted to the USNVC by WNHP staff through a peer-reviewed process. NCCN plots were combined with statewide forest and wetland plot data from the US Forest Service (USFS) and other sources to create a comprehensive data set for Washington. Analyses incorporated Cluster Analysis, Nonmetric Multidimensional Scaling (NMS), Multi-Response Permutation Procedure (MRPP), and Indicator Species Analysis (ISA) to identify, vet, and describe USNVC group, alliance, and association distinctions. The resulting revised classification contains 321 plant associations in 99 alliances. A total of 54 upland associations were moved through the peer review process and are now part of the USNVC. Of those, 45 were provisional or preliminary types from Crawford et al. (2009), with 9 additional new associations that were originally identified by INR. WNHP also revised the concepts of 34 associations, wrote descriptions for 2 existing associations, eliminated/archived 2 associations, and created 4 new upland alliances. Finally, WNHP created 27 new wetland alliances and revised or clarified an additional 21 as part of this project (not all of those occur in the parks). This report and accompanying vegetation descriptions, keys and synoptic and environmental tables (all products available from the NPS Data Store project reference: https://irma.nps.gov/DataStore/Reference/Profile/2279907) present the fruit of these combined efforts: a comprehensive, up-to-date vegetation classification for the three major national parks of Washington State.
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