Dynamics of wetland vegetation under multiple stresses: a case study of changes in sawgrass trait, structure, and productivity under coupled plant‐soil‐ microbe dynamics

Abstract

This paper quantifies wetland vegetation dynamics under drought, waterlogging, shading, and nutrient stresses within the coupled plant-soil-microbe system. A plant is characterized by three independent traits, namely leaf nitrogen (N) content, specific leaf area (SLA), and allometric carbon (C) allocation to rhizome storage, while plant growth is modelled through a dynamic plant allocation scheme. The modelling of N focuses on the internal cycle in which the aerobic and anaerobic processes are determined by the dynamics of oxygen controlled by plants, microbial aerobic processes, and hydrologic dynamics. The dynamics of water levels and soil moisture are described by a simple hydrologic model with stochastic rainfall and are decoupled from the plant-soil-microbe dynamics. Using the model to investigate the dynamics of sawgrass, the results, which are consistent with field observations in the southern Everglades, indicate that SLA decreases with increasing anaerobic condition. The lower SLA maintains high stomatal opening, while at the same time prevents cavitational collapse when sawgrass lowers its root : shoot ratio to reduce C cost in root anaerobic respiration. Given a naturally low but not too scarce level of phosphorus, net N mineralization is higher in the wetter hydrologic regimes because the increase in anaerobic decomposition and N mineralization compensate for the decline in those of aerobes; and the slower growing, more nitrogen efficient anaerobes compete less with plants for N. The optimal traits are the results of several counteracting trends of trade-offs in C and N economy differently influenced by trait combinations in different wetland environments.

Spatial heterogeneity of soil water content on surface land following reforestation in a semi-arid region

“…4). Furthermore, SWC in planted and mixed forests years decreased with age in this study, likely leading to a negative feedback to the water circulation processes in the ecosystem; these results were consistent with those of previous studies (Wang et al, 2011;Zhu et al, 2017), and may be illustrative of the repetitive degradation of the planted area within the past 20 years (A et al, 2019;He et al, 2007;Muneepeerakul et al, 2011;Sun et al, 2014). In the early stages of plantation establishment, soil moisture formed a new trade-off between the new vegetation cover and precipitation, and then a relatively stable water cycle was gradually established (Fu et al, 2003;Gomez-Plaza et al, 2001;Sun et al, 2014).…”

Reforestation Will Lead to a Long-Term Downward Trend in the Water Content of the Surface Soil in a Semi-Arid Region

“…Consequently, the lower SWC in mixed forests may indicate an objective phenomenon of reduced water availability that could have occurred during the plantation phase [42]. This finding contrasts with those of several prior studies [26,41] and may reflect the repetitive degradation of the planted area over the past two decades [8,19,[43][44][45]. Initially, there may be a marginal decrement in pedospheric hydric content attributable to the augmented hydric requisites of arboreal proliferation and the desiccation of exposed pedologic surfaces.…”