No abstract

No abstract

Global metrics of land cover and land use provide a fundamental basis to examine the spatial variability of human-induced impacts on freshwater ecosystems. However, microscale processes and site specific conditions related to bank vegetation, pollution sources, adjacent land use and water uses can have important influences on ecosystem conditions, in particular in smaller tributary rivers. Compared to larger order rivers, these low-order streams and rivers are more numerous, yet often under-monitored. The present study explored the relationship of nutrient concentrations in 150 streams in 57 hydrological basins in South, Central and North America (Buenos Aires, Curitiba, São Paulo, Rio de Janeiro, Mexico City and Vancouver) with macroscale information available from global datasets and microscale data acquired by trained citizen scientists. Average sub-basin phosphate (P-PO4) concentrations were found to be well correlated with sub-basin attributes on both macro and microscales, while the relationships between sub-basin attributes and nitrate (N-NO3) concentrations were limited. A phosphate threshold for eutrophic conditions (>0.1 mg L-1 P-PO4) was exceeded in basins where microscale point source discharge points (eg. residential, industrial, urban/road) were identified in more than 86% of stream reaches monitored by citizen scientists. The presence of bankside vegetation covaried (rho = –0.53) with lower phosphate concentrations in the ecosystems studied. Macroscale information on nutrient loading allowed for a strong separation between basins with and without eutrophic conditions. Most importantly, the combination of macroscale and microscale information acquired increased our ability to explain sub-basin variability of P-PO4 concentrations. The identification of microscale point sources and bank vegetation conditions by citizen scientists provided important information that local authorities could use to improve their management of lower order river ecosystems.

This paper describes the classification and ordination of Sonoran Desert vegetation using systematically collected data from the US Army Yuma Proving Ground ͑USYPG͒. Two classifications were created, one based upon relative plant cover derived from 100 m line transect data and one based upon relative plant density derived from 6 m ϫ 100 m belt transect data, with the belt transect being a lateral extension of the line transect. Both cluster analysis using Ward's Method and TWINSPAN were used for classifying the data while Principal Component Analysis, Correspondence Analysis, Detrended Correspondence Analysis, and Non-Metric Multidimensional Scaling were used as ordination methods. Cluster analysis was superior to TWINSPAN in creating logical classifications comparable to published descriptions of vegetation communities found in the Lower Colorado Subdivision of the Sonoran Desert. Together, the ordination methods served to accentuate different aspects of the data including main gradients of species composition, in particular a gradient separating plots with riparian-affinities from the main data set, a Larrea tridentata-Ambrosia dumosa gradient, and a gradient separating Encelia farinosa from the main data set. The main difference between the relative cover and relative density classifications was that the former under-represented cacti such as Opuntia bigelovii and the latter under-represented such as Parkinsonia microphylla and Olneya tesota. The classification methodology used in this study is useful for evaluating resource sampling strategies on U.S. Army bases in sparsely vegetated areas and the classifications could be used as a baseline for monitoring changes in vegetation communities.

The Greater Vancouver area has undergone significant land use and land cover (LULC) change over the past several decades, often adversely affecting stream health and water quality, particularly in those areas that have undergone the most urbanization. In this study 30 years of historical LULC and water quality data were examined using GIS and statistical analysis to better understand these impacts and to help build a broader understanding of cause and effect relationships of changing LULC, especially since urbanization is increasingly occurring within sensitive watersheds at greater distances from the City of Vancouver. Urban, agriculture, and disturbed LULC data from 1976, 1986, and 2000 were examined within a number of watersheds and related to historical water quality data sampled from streams during similar time frames. Additional higher resolution 2006 LULC data from a smaller number of watersheds were then examined and compared to stream health data to investigate the sensitivity of LULC data resolution on monitoring watershed impact. While LULC impact can be clearly seen at both high and lower resolutions, issues of ambiguous land cover and land use designations can potentially affect the magnitude of the relationship.