Combined effects between temporal heterogeneity of water supply, nutrient level, and population density on biomass of four broadly distributed herbaceous species

Abstract

Temporal heterogeneity of water supply affects grassland community productivity and it can interact with nutrient level and intraspecific competition. To understand community responses, the responses of individual species to water heterogeneity must be evaluated while considering the interactions of this heterogeneity with nutrient levels and population density. We compared responses of four herbaceous species grown in monocultures to various combinations of water heterogeneity, nutrient level, and population density: two grasses (Cynodon dactylon and Lolium perenne), a forb (Artemisia princeps), and a legume (Trifolium repens). Treatment effects on shoot and root biomass were analyzed. In all four species, shoot biomass was larger under homogeneous than under heterogeneous water supply. Shoot responses of L. perenne tended to be greater at high nutrient levels. Although root biomass was also larger under homogeneous water supply, effects of water heterogeneity on root biomass were not significant in the grasses. Trifolium repens showed marked root responses, particularly at high population density. Although greater shoot and root growth under homogeneous water supply appears to be a general trend among herbaceous species, our results suggested differences among species could be found in the degree of response to water heterogeneity and its interactions with nutrient level and intraspecific competition.

Effects of temporal heterogeneity of water supply and nutrient levels on plant biomass growth depend on the plant's relative size within its population

“…On the other hand, periodic water deficits decreased plant growth under the heterogeneous water supply. This tendency is likely to be common in many species, because the result is consistent with the results of several previous studies of water heterogeneity (Saeed and El-Nadi 1998;Novoplansky and Goldberg 2001;Hagiwara et al 2012;but see Heisler-White et al 2008).…”

“…The temporal heterogeneity of the frequency of water supply (hereafter referred to as the ''water heterogeneity'') alters the biomass growth of plants: plants grow larger under a more homogeneous (more frequent) water supply than under a more heterogeneous (less frequent) water supply, because plants can take up water more stably under homogeneous conditions (Saeed and El-Nadi 1998;Novoplansky and Goldberg 2001;Hagiwara et al 2012; but see Sher et al 2004;Heisler-White et al 2008). The variability of water availability, not only the total water availability, can affect plant biomass, because the effect of heterogeneity remains clear even when the same amount of water is provided in heterogeneous and homogeneous conditions (Saeed and El-Nadi 1998;Novoplansky and Goldberg 2001).…”

Spatial Pattern and Population Structure of Artemisia ordosica Shrub in a Desert Grassland under Enclosure, Northwest China

“…At this time, a great deal of seeds germinated and grew into seedlings or adults, which caused a high reduction of shrubs’ height and crown ( Table 2 ). However, elevated plant density and size lead to some individuals dying or withering because of a lack of ability to face intense intraspecific competition for light, water, and nutrients [ 76 , 77 , 78 ]. Further, the appearance and development of soil crusts, which is water-absorbing and hinders water infiltration, would prevent seeds from germinating [ 79 , 80 , 81 ].…”