N addition suppresses the performance of grassland caterpillars (Gynaephora alpherakjj) by decreasing ground temperature

Abstract

Citation: Yang, Y., X. Xi, X. Zhong, N. Eisenhauer, and S. Sun. 2017. N addition suppresses the performance of grassland caterpillars (Gynaephora alpherakjj) by decreasing ground temperature. Ecosphere 8(3):e01755. 10.1002/ecs2.1755Abstract. Nitrogen deposition may stimulate plant biomass production and improve the quality of plant tissue, with both effects potentially facilitating herbivore growth and development. We hypothesized that simulated N deposition (N addition) would facilitate the growth and development of the grassland caterpillar Gynaephora alpherakjj, a notorious pest species in the alpine Tibetan meadow. We tested this hypothesis in two complementary experiments. The first field experiment tested N (ambient N levels vs. N addition) and caterpillar effects (caterpillar absence vs. presence) on plant community and sedge (major food plant species for caterpillars) biomass, growth, and development rate of the caterpillars, and microhabitat temperature. The second chamber experiment tested N addition effects through plant tissue quality on caterpillar performance. Results show that N addition increased the biomass and leaf N concentration of the sedge species, but decreased the feeding time, growth, and development rate of the caterpillars in the field experiment. The independent chamber experiment showed that increased leaf N facilitated the caterpillar growth and development. These results suggest that the reduced performance of caterpillars was not caused by an N addition-induced change in food quality. By contrast, N addition significantly reduced the ground surface temperature presumably because of canopy shading, as indicated by increased plant height and biomass in the N addition treatment. A significant quadratic relationship between ground surface temperature and the number of feeding caterpillars in the field experiment explained the difference in feeding time between the N addition and ambient N treatments. It can thus be concluded that N addition reduced caterpillar performance by stimulating plant growth leading to reduced ground surface temperatures, which decreased caterpillar feeding activity. Our results suggest that the effect of N deposition on abiotic factors could be critical to the growth, development, and survival of immobile herbivore species or the individuals at immobile stages that cannot quickly respond to changing microclimatic environments.

Predicting the Distribution of Oxytropis ochrocephala Bunge in the Source Region of the Yellow River (China) Based on UAV Sampling Data and Species Distribution Model

“…In this study, visual species recognition was mainly used to extract the presenceabsence information, and the efficiency is relatively low. Therefore, in a further study, a large number of obtained training samples (for example, O. ochrocephala selected manually can be automatically extracted and saved by proposal classifier, Figure 3) will play a key role in the subsequent automatic object identification [61,62]. Then, machine learning algorithms, such as convolution neural network and random forest, will identify target species automatically [63].…”

Invertebrate herbivory accelerates shift towards forbs caused by warming in a sedge‐dominated alpine meadow

“…The caterpillar species Gynaephora alpherakjj , a notorious insect pest of grasslands in alpine areas of the Northern Hemisphere, is widely distributed in the meadows of the Tibetan Plateau (Zhang & Yuan, 2013). This species is an invertebrate herbivorous species with partial diets, foraging mainly on sedges (Xi et al, 2013; Yang et al, 2017). It not only competes for high‐quality forages with livestock, but also causes cattle disease (e.g., oral membrane inflammation), which substantially threatens the sustainable development of animal husbandry in the Tibetan Plateau (Shang et al, 2014).…”