The influence of seasonal precipitation and grass competition on 20 years of forb dynamics in northern Chihuahuan Desert grassland. (27th December 2016)

• Record Type: Journal Article
• Authors: Mulhouse, John M.; Hallett, Lauren M.; Collins, Scott L.
• Editors: Vandvik, Vigdis
• Is Part Of: Journal of vegetation science. Volume 28:Number 2(2017:Mar.)
• Page Start: 250
• Page End: 259
• Publication Date: 2016-12-27
• Subjects: Chihuahuan Desert -- Core‐satellite hypothesis -- Forbs -- Grasslands -- Species richness -- Temporal distribution pattern -- Vegetation dynamics; Plant ecology -- Periodicals; Plant communities -- Periodicals; Plant populations -- Periodicals; 581.7
• DOI: 10.1111/jvs.12476
• Languages: English
• ISSNs: 1100-9233

Abstract

Abstract: Aims: In arid grasslands forbs represent a large component of species diversity and provide a key resource for pollinators and consumers. However, low abundances and high temporal variability make it challenging to successfully predict forb presence and abundance from 1 yr to the next. In this study we: (1) characterize patterns of semi‐arid forb diversity and abundance over time; (2) determine the relative importance of direct vs indirect (via grass competition) effects of precipitation on forb richness and abundance; and (3) separate the effect of precipitation timing on forb community composition from the effects of precipitation amount and season. Location: Semi‐arid grassland, Sevilleta National Wildlife Refuge, Socorro County, central New Mexico, USA. Methods: We analysed forb dynamics along two 400‐m long line‐intercept transects in response to inter‐annual and seasonal precipitation variability and abundance of perennial grasses using a unique 20‐yr species composition data set from ungrazed native grassland in the northern Chihuahuan Desert. Results: Forb richness and cover were significantly positively associated with precipitation across seasons. Total richness was high across the time series but substantially lower within any given year. A direct, positive effect of precipitation overrode any potential negative, indirect effect via grass competition. Although aggregate forb responses were strongly linked with precipitation, individual species responses were highly variable and generally not linked with either precipitation timing or season. Conclusions: In the hotter, drier climate predicted by meteorological models for the US southwest, forbs may be negatively impacted if winter moisture decreases and monsoon precipitation becomes more variable. On the other hand, the flexibility exhibited by forbs in germination and establishment throughout the growing season may help buffer some common species to increased inter‐annual precipitation variability. Abstract : Temporal variability limits predictability of forb community composition in desert grasslands. Using a 20‐yr dataset we related forb dynamics to seasonal precipitation and perennial grass abundance. Forb richness and cover were significantly positively associated with precipitation, but not grass abundance. Given the importance of precipitation, forbs may decline as aridity increases under climate change yet some species could exhibit resiliency.