Increasing temperature reduces the coupling between available nitrogen and phosphorus in soils of Chinese grasslands

Abstract

Changes in climatic conditions along geographical gradients greatly affect soil nutrient cycling processes. Yet how climate regimes such as changes in temperature influence soil nitrogen (N) and phosphorus (P) concentrations and their stoichiometry is not well understood. This study investigated the spatial pattern and variability of soil N and P availability as well as their coupling relationships at two soil layers (0–10 and 10–20 cm) along a 4000-km climate transect in two grassland biomes of China, the Inner Mongolian temperate grasslands and the Tibetan alpine grasslands. Our results found that in both grasslands, from cold to warm sites the amounts of soil total N, total P and available P all decreased. By contrast, the amount of available N was positively related to mean annual temperature in the Tibetan grasslands. Meanwhile, with increasing temperature ratio of available N to P significantly increased but the linear relationship between them was considerably reduced. Thus, increasing temperature may not only induce a stoichiometric shift but also loose the coupling between available N and P. This N-P decoupling under warmer conditions was more evident in the Tibetan alpine grasslands where P limitation might become more widespread relative to N as temperatures continue to rise.

Elevation and aspect determine the differences in soil properties and plant species diversity on Himalayan mountain summits

“…Although both showed higher values toward south and east aspects, P showed a decline with elevation while as K an increase. Since, available P in plant litter is usually difficult to breakdown because it exists in the form of phospholipid and phytate, which need to be processed by specialized enzymes affected by multiple factors such as pH and temperature (Chen, Condron, Davis, & Sherlock, 2004; Geng et al, 2017). Therefore, difference in soil temperature along elevation and among different aspects in the selected summits might be responsible for the availability of different levels of soil P. Moreover, an increase in K concentration with elevation might be related to better dissolution from rocks and minerals in the presence of slightly higher acidic condition at higher elevations (Mathur & Bhatnagar, 1964).…”

“…Under the contemporary climate change, the alpine ecosystems are reported to be warming at a much higher rate than the adjacent lowland areas—a pattern termed as elevation ‐ dependent warming (Gottfried et al, 2012; Pepin et al, 2015; Steinbauer et al, 2018). In fact, changes in climatic conditions (e.g., temperature and precipitation) can alter both biotic and abiotic environments in alpine ecosystems (Alatalo, Jägerbrand, & Molau, 2016; Geng et al, 2017). The impacts of climate change on community composition and soil nutrient properties may be particularly evident in alpine ecosystems.…”

Assessment of plant species diversity based on hyperspectral indices at a fine scale

“…Compared to airborne hyperspectral imagery, the hyperspectral data gained by hand-held portable parameters have the advantages of low labor cost and high spatial resolution, and they are less influenced by atmosphere layer and background environment; therefore they might be a better option for quick estimation of plant diversity. These characteristics are important when carrying out repeat monitoring on fine-habitat species diversity over large areas, especially for grasslands since they cover nearly a third of the continents on earth 41 .…”

“…Except for plant diversity estimation, the methodology used in the present study can help in recovering estimates made through remote sensing data for other ecological applications 41 , 42 . Ecological condition evaluations, such as riparian condition 43 , vegetation eco-restoration 44 and forest cover mapping 45 , all of which are variables derived from satellite or airborne imageries at a grain of 30 m or coarser, might be improved by hyperspectral data and stepwise linear regression on narrower sensitive wavebands.…”

Thermal acclimation of leaf respiration varies between legume and non-legume herbaceous

“…The lack of significant response in R d with additional N but without additional phosphorus (P) suggests the co-limitation of N and P in controlling R d (van De Weg et al 2013;Heskel et al 2014). The warming-induced decline in available P in grassland ecosystem (Geng et al 2017) thus, might explain the higher relative N reduction in IB than other species since legumes are sensitive to P deficiency (Bargaz et al 2015).…”