Photosynthetic responses of two pleurocarpous mosses to low-level nitrogen addition: a study in an old-growth fir forest

Abstract

We examined photosynthetic responses of two dominant pleurocarpous mosses, Actinothuidium hookeri (Mitt.) Broth. and Hylocomium splendens (Hedw.) Schimp. to low-level nitrogen (N) addition. The study was conducted in an old-growth fir forest on the eastern Tibetan Plateau. The added N, 1 g N/m 2 , was mainly absorbed by the new-growth. The concentrations of chlorophyll a and b both increased 8 days after N addition. The quantum yield of Photosystem II (W PSII ) also increased. However, no significant changes were found in terms of gas exchange parameters. The mass-based CO 2 assimilation rate, chlorophyll a content, and chlorophyll a/b ratio (which is related to antenna size of the photosystem), of H. splendens were all higher than those of A. hookeri. Shoot mass per area (SMA) of H. splendens was lower than that of A. hookeri. We conclude that the photosynthetic rate was less sensitive to low-level N addition than chlorophyll contents and chlorophyll fluorescence parameters, suggesting other limiting factors in the photosynthetic process. Additionally, the faster growing H. splendens has a higher photosynthetic capacity than A. hookeri, allocating fewer resources to structural tissue.

The ‘plant economic spectrum’ in bryophytes, a comparative study in subalpine forest

“…For most parameters, the bryophyte values were within the ranges reported for vascular plant leaves ( Table 2 ). Only for A mass , A area , PNUE, and PPUE, the lower values in our bryophytes were below the vascularplant ranges, although they were within the ranges usually reported for bryophytes ( Rice et al, 2008 ;Waite and Sack, 2010 ;Wagner et al, 2014b ;Wang et al, 2014 ;Liu et al, 2015 ). Compared to vascular plant leaves, bryophytes had relatively low values for all measured traits, except, interestingly, P concentration.…”

“…Th e forest has a canopy (42% coverage) dominated by Abies fargesii var. faxoniana , and the understory is dominated by feather mosses ( Actinothuidium hookeri , Hylocomium splendens , and Ptilium crista-castrensis , covering approximately 60% of the ground area) ( Liu et al, 2015 ). Twenty-eight terrestrial or semiterrestrial (on rocks or rotten logs) bryophytes were chosen for the study (including 2 liverworts and 25 moss species; the vegetative shoot and reproductive shoot of Mnium spinosum were considered as two bryophyte types because of their distinct appearances) ( Table 1 ).…”

Higher photosynthetic capacity and different functional trait scaling relationships in erect bryophytes compared with prostrate species

“…Common shrub and herbaceous species include Rosa omeiensis, Salix spp., Ligularia sagitta and Fragaria orientalis. Bryophytes are abundant in the understory and account for approximately 60 % of the cover (Liu et al 2015). The most dominant species are Actinothuidium hookeri, Hylocomium splendens, Pleurozium schreberi and Ptilium crista-castrensis.…”

Comparisons of photosynthesis‐related traits of 27 abundant or subordinate bryophyte species in a subalpine old‐growth fir forest

“…year branches grow on last year branches. They thus form new levels and "climb" over other bryophytes, small vascular plants, and fresh litter (Liu, Wang, Bao, & Li, 2015). This growth form might be the reason that these large pleurocarpous mosses can dominate the floors of boreal and subalpine forests because the resulting dense and continuous carpet can restrict the growth of other bryophytes through changing soil temperatures, lowering the already-low light levels, and by intercepting nutrient deposition (Cleavitt, 2004;Startsev, Lieffers, & McNabb, 2007).…”