Warming Effects on Topsoil Organic Carbon and C:N:P Stoichiometry in a Subtropical Forested Landscape

Abstract

Warming effects on agricultural and forest ecosystems have been well documented at broad spatiotemporal scales but less so at stand and landscape scales. To detect the changes in soil organic carbon (SOC) and carbon:nitogen:phosphorus (C:N:P) stoichiometry in response to a short-range warming gradient, we defined an inverse elevation-dependent warming gradient and developed a novel index of warming based on a common environmental lapse rate. We associated the warming gradient and warming index with the changes in SOC and C:N:P stoichiometry and tested the independence of warming effects using partial correlation analysis. SOC content and C:N:P stoichiometric ratios significantly decreased with warming, and the effect of warming on C:N:P stoichiometric ratios were stronger than on SOC content. The relationships of SOC content and C:N:P stoichiometric ratios with warming did not change after controlling for two other energy-related variables, i.e., transmitted total radiation and potential direct incident radiation. However, the strength in the relationships of C:N:P stoichiometric ratios with vegetation-related variables significantly decreased after the warming index was controlled for. As indicated by the random forest regression model, the warming index was the most important variable for predicting SOC variability and the second most important for predicting total N variability, while vegetation-related variables were the most important for predicting C:N:P stoichiometric ratios. Our results showed that warming was responsible for the decrease in SOC content and C:N:P stoichiometric ratios and the warming index was the most important variable for predicting SOC variability. Although the most important variables for C:N:P stoichiometric ratios were related to vegetation, the relationships between C:N:P stoichiometric ratios and vegetation-related variables were significantly affected by warming. These findings demonstrate that warming is the major driver of SOC variability and the decrease in SOC content, as well as of C:N:P stoichiometry, even along a short-range warming gradient.

Size-dependent associations of woody plant structural diversity with soil C:N:P stoichiometry in a subtropical forest

“…At the community or stand level, however, few studies have determined how soil C, N, and P and their stoichiometric ratios are related to biotic variables such as species composition, community structure, and biodiversity. A recent study of a subtropical forest ecosystem of the same area showed a consistent pattern for the spatial heterogeneity of soil C:N:P stoichiometric ratios, which could predict the changes of certain community indicators to some extent and were sensitive in response to a negative elevation-dependent warming gradient (Su et al, 2020). From this point of view, an appropriate stratification of environmental gradients can help reveal the relationships between response variables and the weak environmental signals from abiotic or biotic factors.…”

“…Our study site was located at the Kanghe Provincial Nature Reserve (23 °44′37″-23 °52′16″ N, 115 °04′27″-115 °09′41″ E) in the eastern part of Guangdong Province in south China. This area has a humid subtropical monsoon climate, with a mean annual temperature ranging from 20.3 to 21.1 °C and a mean annual precipitation of 2,142 mm (Hu et al, 2015;He et al, 2017;Su et al, 2020). Soils in the area are predominantly clay loamy TABLE 2 Pearson correlation coefficients of six vegetation-related biotic factors with soil total organic carbon (TOC, g kg −1 ), total nitrogen (TN, g kg −1 ), total phosphorus (TP, g kg −1 ), and C:N:P stoichiometric ratios at the quadrat level.…”

Altitudinal Gradients Modify the Ecological Stoichiometry and Enzyme Activities of Soil in a Natural Secondary Quercus spp. Forest of the Dabie Mountains

“…At the mountain peak, the vegetation cover was low, and reduced litter inputs translated to decreased SOC and TN contents [11]. Higher temperatures at low altitudes may induce soil organisms to consume large quantities of organic matter, which in turn impacts the accumulation of soil C and N [22].…”

Woody Plant Structural Diversity Changes across an Inverse Elevation-Dependent Warming Gradient in a Subtropical Mountain Forest

“…In a mountain landscape, temperature decreases as elevation increases at a scale of 0.65 • C/100 m according to the common environmental lapse rate [8,9]. Conversely, an inverse elevational gradient corresponds to a warming gradient and can be used to predict warming effects on the structural attributes of forest communities with the "space-for-time substitution" method [10].…”

“…The changes in community structure and species diversity along elevational gradients have long attracted the interest of ecologists and forest scientists. The response of forest community to climate warming can be shown by examining the changes in community structure and species diversity across an inverse elevational gradient [5,10], because in a mountain landscape a warming trend exists with descending elevation according to an environmental temperature lapse rate of 0.65 • C per 100 m [8,9]. The subtropical mountain forest ecosystem is an ideal natural experimental environment for studying the variation of plant community structure and diversity along the elevational gradient, because the subtropical forest is rich in species resources [14,15], and the mountains with sloping topography can directly or indirectly affect the distribution of thermal radiation, the key factor controlling the richness, abundance, and dominance of plant species in a community [10,16].…”