Effects of nitrogen deposition and insect herbivory on patterns of ecosystem‐level carbon and nitrogen dynamics: results from the CENTURY model

Abstract

Atmospheric nitrogen deposition may indirectly affect ecosystems through depositioninduced changes in the rates of insect herbivory. Plant nitrogen (N) status can affect the consumption rates and population dynamics of herbivorous insects, but the extent to which N deposition-induced changes in herbivory might lead to changes in ecosystemlevel carbon (C) and N dynamics is unknown. We created three insect herbivory functions based on empirical responses of insect consumption and population dynamics to changes in foliar N and implemented them into the CENTURY model. We modeled the responses of C and N storage patterns and flux rates to N deposition and insect herbivory in an herbaceous system. Results from the model indicate that N deposition caused a strong increase in plant production, decreased plant C : N ratios, increased soil organic C (SOC), and enhanced rates of N mineralization. In contrast, herbivory decreased both vegetative and SOC storage and depressed N mineralization rates. The results suggest that herbivory plays a particularly important role in affecting ecosystem processes by regulating the threshold value of N deposition at which ecosystem C storage saturates; C storage saturated at lower rates of N deposition with increasing intensity of herbivory. Differences in the results among the modeled insect herbivory functions suggests that distinct physiological and population response of insect herbivores can have a large impact on ecosystem processes. Including the effects of herbivory in ecosystem studies, particularly in systems where rates of herbivory are high and linked to plant C : N, will be important in generating accurate predictions of the effects of atmospheric N deposition on ecosystem C and N dynamics.

The biogeochemical consequences of litter transformation by insect herbivory in the Subarctic: a microcosm simulation experiment

“…During these outbreaks, insect deposits (including excreta/frass, cadavers, moults, pupae, greenfall) constitute considerable nutrient fluxes from the canopy to the soil, with the largest single constituent being frass (Hunter 2001;Arnold et al 2016). Understanding how these outbreaks influence element cycling and plant growth is essential for improving predictions of C and N cycling (Throop et al 2004;Metcalfe et al 2016) and plant community composition (Jepsen et al 2013) across the Scandinavian Arctic, particularly as the extent and intensity of outbreaks appear to be increasing due to climate warming (Jepsen et al 2008;Kozlov and Zvereva 2017).…”

Effect of Effluent Water on Population Dynamics of Cowpea Aphid, Aphis Craccivora Koch (Hemiptera: Aphididae), on Cowpea Plants

“…This is because nitrogen has been reported to have a positive correlation with aphid growth [24]. Nitrogen is essential in insect development, aphids inclusive by increasing the abundance of free amino acids in the plant [25]. The aphid infestation per plant showed significant difference among the four treatments, control inclusive, at each day of observation (F7, 86 = 11.79; P < 0.0001) .…”

The role of neuropeptides in caterpillar nutritional ecology

“…However, while plants often contain sufficient or excess carbohydrates (i.e. sucrose), proteins may be limiting in quantity and/or quality [32,57,82,111,138]. Therefore, to obtain sufficient protein resources, larvae must limit the detrimental effects of excess carbohydrate consumption [68,70,131,142] One post-ingestive mechanism to cope with excess glucose is elevated respiration, which has been demonstrated in locust, and assumed to occur in caterpillars [131,149].…”

“…Atmospheric carbon dioxide levels are predicted to double by the end of the century [100]. The resulting climate changes will significantly affect plant carbon and nitrogen allocation and consequently levels of insect herbivory [76,138]. Thus, understanding the flexibility of the physiological/biochemical processes governing feeding behaviors of caterpillars could be useful in predicting the distribution and abundance of both insect and plant species.…”

“…temperature, light, relative humidity and soil quality) and biotic (e.g. intra-and inter-specific competition) factors [82,112,104,138]. Similarly, levels of defenses vary temporally and spatially both within and between plants of the same species [48,106,139].…”