Multivariate analysis of watershed health and sustainability in Turkey

National hydrological network data between 1970 and 2002 for 96 stations across 25 watersheds were used to monitor annual trends in 13 variables: streamflow rates, water temperature, pH, electrical conductivity (EC), sediment concentration and eight nutrient levels (Na, K, Ca+Mg, CO₃, HCO₃, Cl, SO₄ and boron). The dataset was analysed with multiple linear regression (MLR) models, principal components analysis (PCA) and hierarchical cluster analysis (CA). The Turkish watersheds have experienced a significant increase in pH, K, CO₃ and a significant decrease in streamflow rate and sediment concentration between 1970 and 2002, with considerable spatial variations. There was also an increasing trend in streamwater temperature, at a rate of 0.05°C yr^–1 (p > 0.05). The MLR models had high r ² values of 69.6% to 99.9% at p ≤ 0.001 for 12 out of the 13 variables, with r ² of 42% for boron (p < 0.05). PCA reduced the dimensionality of the dataset to four principal components that explain most (81.7%) of the variance. CA was able to distinguish six geographically associated groupings of watersheds with similar attributes in concordance with the climate zones of Turkey, despite the use of different clustering methods (complete, McQuitty, average, centroid and single linkage methods). Multivariate analyses of dynamic watershed characteristics provide the basis on which preventive and mitigative measures can be tailored to secure and enhance watershed health and sustainability.     

Land resource degradation in China: Analysis of status,trends and strategy

Land degradation threatens environmental well-being and is a growing global issue. China is among the most affected countries in the world in terms of the extent, intensity and economic impact of land degradation. Sustainable and successful intervention requires clear definition and quantification of land degradation. Based on land resource variation survey data from 1991 to 2002, this paper identified, defined and classified land resource degradation, and analyzed dynamic changes in the degradation and rehabilitation process. Through the establishment of a land resource degradation index, the status and trend of degradation in China was explored to enable the design and planning of interventions for mitigation and establishment of sustainable land use and management practices. Results showed that: (1) The total land degradation index (A) fluctuated upwards from 1991 to 2002, although some parts improved. (2) Sand and rock desertification, deforestation and wetland loss reduced slightly, whereas secondary salinification, non-agricultural land occupation and natural grassland further deteriorated. (3) 66.27% of degradation was in natural grassland and non-agricultural land; while 57.5% of rehabilitation focused on sandy desertification and forests. (4) Non-agricultural land occupation and wetland shrinkage are primary causes of land resource deterioration in China. (5) Grassland, cultivated land and forest land accounted for 83.9% of degradation. (6) All the degradation processes are interrelated. These results provide useful information to combat future land resource degradation in China.