Nitrogen and phosphorus addition differentially enhance seed production of dominant species in a temperate steppe

Abstract

Previous studies have demonstrated changes in plant growth and reproduction in response to nutrient availability, but responses of plant growth and reproduction to multiple levels of nutrient enrichment remain unclear. In this study, a factorial field experiment was performed with manipulation of nitrogen (N) and phosphorus (P) availability to examine seed production of the dominant species, Stipa krylovii, in response to N and P addition in a temperate steppe. There were three levels of N and P addition in this experiment, including no N addition (0 g N m−2 year−1), low N addition (10 g N m−2 year−1), and high N addition (40 g N m−2 year−1) for N addition treatment, and no P addition (0 g P m−2 year−1), low P addition (5 g P m−2 year−1), and high P addition (10 g P m−2 year−1) for P addition treatment. Low N addition enhanced seed production by 814%, 1371%, and 1321% under ambient, low, and high P addition levels, respectively. High N addition increased seed production by 2136%, 3560%, and 3550% under ambient, low, and high P addition levels, respectively. However, P addition did not affect seed production in the absence of N addition, but enhanced it under N addition. N addition enhanced seed production mainly by increasing the tiller number and inflorescence abundance per plant, whereas P addition stimulated it by decreasing the plant density yet stimulating height of plants and their seed number per inflorescence. Our results indicate seed production is not limited by P availability but rather by N availability in the temperate steppe, whereas seed production will be increased by P addition when N availability is improved. These findings enable a better understanding of plant reproduction dynamics in the temperate steppe under intensified nutrient enrichment and can inform their improved management in the future.

Increasing precipitation during first half of growing season enhances ecosystem water use efficiency in a semiarid grassland

“…The soil is classified as a Haplic Calcisol according to the FAO classification, with sand, silt, and clay comprising 62.75%, 20.30%, and 16.95%, respectively. The soil aggregate and capillary porosities are 57.16% and 31.10%, respectively, at the depth of 0-10 cm ( Su et al., 2021 ). The average rooting depth is 11.6 cm.…”

“…The aims of this study were 1) to examine how ecosystem WUE responds to increasing growing-season precipitation, 2) to access which period of precipitation increase is more decisive in determining ecosystem WUE and 3) to identify the factors controlling ecosystem WUE under higher growing season precipitation. , respectively, at the depth of 0-10 cm (Su et al, 2021). The average rooting depth is 11.6 cm.…”