Species‐specific Response of Photosynthesis to Burning and Nitrogen Fertilization

Abstract

The present study was conducted to examine photosynthetic characteristics of three dominant grass species (Agropyron cristatum, Leymus chinensis, and Cleistogenes squarrosa) and their responses to burning and nitrogen fertilization in a semiarid grassland in northern China. Photosynthetic rate (P(n)), stomatal conductance (g(s)), and water use efficiency (WUE) showed strong temporal variability over the growing season. C. squarrosa showed a significantly higher P(n) and WUE than A. cristatum and L. chinensis. Burning stimulated P(n) of A. cristatum and L. chinensis by 24-59% (P < 0.05) in the early growing season, but not during other time periods. Light-saturated photosynthetic rate (P(max)) in A. cristatum and the maximum apparent quantum yield (Phi(max)) in A. cristatum and L. chinensis were significantly enhanced by burning (16-67%) in both the fertilized and unfertilized plots. The main effect of burning on P(n), P(max) and Phi(max) was not significant in C. squarrosa. The burning-induced changes in soil moisture could explain 51% (P = 0.01) of the burning-induced changes in P(n) of the three species. All three species showed positive responses to N fertilization in terms of P(n), P(max), and Phi(max). The stimulation of P(n) under N fertilization was mainly observed in the early growing season when the soil extractable N content was significantly higher in the fertilized plots. The N fertilization-induced changes in soil extractable N content could explain 66% (P = 0.001) of the changes in P(n) under N fertilization. The photosynthetic responses of the three species indicate that burning and N fertilization will potentially change the community structure and ecosystem productivity in the semiarid grasslands of northern China.

Interannual variability of soil microbial biomass and respiration in responses to topography, annual burning and N addition in a semiarid temperate steppe

“…The decreased qCO 2 due to burning also reflects less water stress, which is contrary to the results of a previous study that burning induced higher qCO 2 because of exacerbated water stress (Graham and Haynes, 2006). Second, consistent with the studies in a Kansas tallgrass prairie (Ojima et al, 1994) and a mesic grassland (Heisler et al, 2004), greater solar radiation at the soil surface due to the removal of plant litter by burning can stimulate seed germination and photosynthesis (Zhang et al, 2008b), leading to enhanced plant growth and biomass in this experiment (Xu and Wan, 2008). Moreover, increased total respiration (Xu and Wan, 2008) in combination with decreased microbial respiration in the burned side (Fig.…”

“…This study, as a part of a comprehensive research project in a temperate steppe in northern China since 2005 (Liu et al, 2007;Xu and Wan, 2008;Zhang et al, 2008b), was conducted to examine interannual variability of soil microorganisms in response to topography, burning, and N addition. The specific questions we would like to address include: (1) are there interannual differences in soil microbial biomass and respiration in response to topography, annual burning and N addition in this semiarid temperate steppe?…”

Responses of a Dominant Temperate Grassland Plant (Leymus chinensis) to Elevated Carbon Dioxide and Nitrogen Addition in China

“…Although N is one of the most important factors controlling plant photosynthesis, the effects of N application on leaf‐level net assimilation rate are inconsistent. Nitrogen fertilization stimulated leaf photosynthesis in some cases (Mitchell and Hinckley 1993; Shangguan et al, 2000; Reich et al, 2003), but not in other cases (Lee et al, 2001; Martínez‐Carrasco et al, 2005; Niu et al, 2006; Zhang et al, 2008). A previous study of L. chinensis in the same geographic area also showed that N fertilization had no effect or even a tendency of a negative effect on photosynthesis (Niu et al, 2006; Zhang et al, 2007).…”

Short-term regrowth responses of four steppe grassland species to grazing intensity, water and nitrogen in Inner Mongolia

“…However, little is known about the interaction between the key regulators (precipitation and nitrogen) and the effect of grazing. In several studies the effect of water (van Staalduinen and Anten 2005;Zhao et al 2008), nitrogen (Chen et al 2005;Zhang et al 2008) or grazing (Liang et al 2002;Liang et al 2009;Xie and Wittig 2003) on different steppe grass species has been analysed, predominantly in pot experiments. Therefore, the present study was conducted to interactively analyse effects of grazing, water and nitrogen on major C3 and C4 grass species.…”