These models produce stable dynamics and form the basis for weed management recommendations, yet exclude the role of the exogenous variables, i.e., those influencing the response of a determined variable but without being affected back by those changes, such as climate. To our knowledge, there are no other studies attempting to understand how both feedback structure and exogenous factors interact in shaping the dynamics of weed populations and their management. Here, we use one of the longest data set in plant populations on two annual weed species from a locality in Central Spain to determine the importance of endogenous and exogenous processes. We focus on diagnosis and modeling tools from population-dynamics theory to analyze these long-term data and to determine the role of the North Atlantic Oscillation and local weather as exogenous factors influencing weed dynamics. In particular, we use the Royama classification of exogenous effects as an organized approach to evaluating the effect of climate on population dynamics. In this way, we can include logical explanations of the possible effects of climate on demographic rates in the population dynamics models and also use independent data for testing model predictions. Our modeling study determined two different feedback structures in the two weed species analyzed. While D. sophia exhibited a second-order feedback and low climate influence, V. hederifolia was characterized by a first-order feedback structure and important effects of climate variables. The endogenous structure therefore appears to be stronger in D. sophia than in V. hederifolia. The dynamics of D. sophia were mainly explained by endogenous factors. A second order feedback structure �C delayed density dependence �C captured the essential elements of the population dynamics of this species in both minimum and notillage. It has been suggested that the accumulation of plant litter as a consequence of high nutrient levels might be a plausible explanation for the second-order feedback structure found in D. sophia under no-tillage practice. Growth of D. sophia in that study took place in a cropping system with high nutrient levels. High nutrient supply could lead to high crop and weed biomass production and high rates of crop litter deposition. The accumulation of plant litter in the topsoil resulting from no-tillage and reduced tillage systems may potentially cause important changes to the physical and chemical environment of the soil surface and may act as a time-delayed inhibitor on the germination of D. sophia populations. It was probably due to the NAO negative effect increasing precipitations in the Mediterranean area.