Effects of fertilization on population density and productivity of herbaceous plants in desert steppe

In order to investigate the impacts of fertilization on population density and productivity on herbaceous plants in desert steppe, nitrogen （N）, phosphorus （P）, and N-P addition experiments were performed. Each fertilizer treatment included four addition levels, i.e., 0, 5, 10, and 20 g/m2. The results indicated that population density decreased as fertilization levels increased regardless of the sort of fertilizer. More specifically, total density as well as density ofArtemisia capillaris, Allium polyrhizum, and Enneapogon brachystachyus decreased significantly in 20 g/m2 treated plots, as compared with the control plots. Fertilization effects on aboveground and root biomasses were extremely similar to that found in population density; that is, both total aboveground biomass and aboveground biomasses for A. capillaris, A. polyrhizum, and E. brachystachyus were negatively correlated with increasing fertilization levels, with all determination coefficients （R2） greater than 0.80. Therefore, in the case of desert regions （annual precipitation 〈180 mm）, fertilization would inhibit population density and productivity of herbaceous plants.

The Effects of Ground Cover Mowing Height on the Fauna of Ground-dwelling Arthropods in Olive Grove

Ground dwelling insects,spiders,and other arthropods play an important role in agroecosystems as predators and saprophytic organisms.Their presence on the soil surface helps the biological control of pests,enhances organic matter decomposition and promotes biodiversity.Soil disturbance,particularly tilling and mowing has greatly affected the assemblage and abundance of epigeic arthropods.This study aimed to determine the effects of herbaceous vegetation cover mowing height on arthropods abundance and structure in olive orchards.The experimental site was divided into three zones(Z1,Z2,and Z3)regarding mowing heights(0 cm,10 cm,and 15 cm).This research was done in 2019 from the beginning of May untill the end of September.During this research,1490 individuals were recorded belonging to 6 classes,11 orders and 13 families.The number of individuals was higher in the zones Z2 and Z3 comparing with Z1.The highest number of individuals showed woodlices(Isopoda)comprising 67,5%of all individuals collected.There were significant differences in the number of Carabidae,Bleteliidae and Forficulidae between the zones of research.Unlike Forficulidae,higher heights of mown positively affected the population of Carabidae and Blateliidae.