No abstract

As the main defoliators of coniferous forests in Shandong Province, China, pine caterpillars (including Dendrolimus suffuscus suffuscus Lajonquiere, D. spectabilis Butler, and D. tabulaeformis Tsai et Liu) have caused substantial forest damage, adverse economic impacts, and losses of ecosystem resources. Therefore, elucidating the effects of drought on the outbreak of these pests is important for promoting forestry production and ecological reconstruction. Accordingly, the aim of the present study was to analyse the spatiotemporal variation of drought in Shandong Province, using the Standard Precipitation Index, and to investigate the impact of drought on the outbreak of pine caterpillar infestations. Future trends in drought and pine caterpillar populations were then estimated using the Hurst exponent. The results showed that: (1) Drought decreased gradually and showed a wetting trend from 1981 to 2012, with frequency decreasing on a decadal scale as follows: 1980s > 1990s > 2000s > 2010s; (2) The total area of pine caterpillar occurrence decreased strongly from 1992 to 2012; (3) Long-term or prolonged drought had a greater positive impact on pine caterpillar outbreak than short-term drought; (4) In the future, a greater portion of the province’s area will experience increased wetting conditions (57%) than increased drought (43%), and the area of pine caterpillar outbreak is estimated to decrease overall. These findings help elucidate the relationship between drought and pine caterpillar outbreak in Shandong Province and, hence, provide a basis for developing preventive measures and plans.

Abstract:Reference evapotranspiration (ET 0 ) plays an important role in regional dry/wet conditions. Based on the Food and Agriculture Organization of the United (FAO) Penman-Monteith method and daily climate variables, ET 0 was calculated for 21 stations in and around the Songnen Grassland, northeast China, during 1960China, during -2014. The temporal and spatial variations of ET 0 and precipitation (P) were analyzed in the annual, seasonal, and growing season (from April to October) time series using the Mann-Kendall test, Sen's slope estimator, and linear regression coupled with a break trend analysis. A sensitivity analysis was used to detect the key climate parameter contributing to ET 0 change. By linear regression analysis on the relationship between ET 0 , P, and the aridity index (AI), the role of ET 0 in determining regional wet/dry conditions was analyzed. Results show a higher ET 0 in the southwest and a lower ET 0 in the northeast, but P was opposite to that of ET 0 . Evident decreasing trends of ET 0 in the annual, seasonal, and growing season time series were detected in almost the entire region by the trend analysis methods. For the entire region, the decreasing trend of ET 0 can be linked to the relative humidity and maximum air temperature. The positive contribution of increasing temperature to ET 0 was offset by the effect of the significantly decreasing relative humidity, wind speed, and sunshine duration at the 0.05 level during 1960-2014. In addition, the value of ET 0 was higher in drought years and lower in wet years.

Land use/cover change (LUCC) and ecosystem service functions are current hot topics in global research on environmental change. A comprehensive analysis and understanding of the land use changes and ecosystem services, and the equilibrium state of the interaction between the natural environment and the social economy is crucial for the sustainable utilization of land resources. We used remote sensing image to research the LUCC, ecosystem service value (ESV), and ecological economic harmony (EEH) in eight main urban areas of Harbin in China from 1990 to 2015. The results show that, in the past 25 years, arable land—which is a part of ecological land—is the main source of construction land for urbanization, whereas the other ecological land is the main source of conversion to arable land. There is no significant change in the value ratio of ESV, however, it is also inclined to the southeast of the study area in spaces like the barycenter of LUCC. The EEH degree has risen from the potential crisis area to the medium coordination degree, and then dropped to the low coordination degree. This shows that although there has been limited change of LUCC, ESV, and EEH in eight main urban areas of Harbin in 25 years, there is a contradiction between the allocation of ecological land and non-ecological land.