Aboveground Biomass Of Forbs Research Articles

Effects of Land Use Changes on the Plant Community Characteristics in the Wetlands of the Semi-Arid Regions

Human disturbance is the main driving factor of wetland vegetation degradation, and plant community changes can directly characterize the process of wetland degradation. The wetlands in semi-arid region of Songnen Plain perform the important ecological functions, especially the habitat of waterbirds. Recently, the succession of wetland plant community has been accelerated by land use changes. In this study, we investigated the variations of plant community in wetlands undergoing land use changes (natural, mowing, light grazing + mowing, moderate grazing and heavy grazing wetlands) in the western Songnen Plain. The results showed that the plant communities were significantly affected by land use changes. The typical wetland plant Calamagrostis angustifolia was the dominant species in natural wetlands, and its dominance was gradually decreased in mowing or grazing wetlands in where Carex spp. or Artemisia selengensis acting as the dominant species. The height, density, and biomass in natural wetlands were significantly higher than those in other wetlands, whereas the species diversity and richness in natural wetlands were significantly lower. The similarity index of plant community in wetlands undergoing land use changes to natural wetlands ranged from 17.7–45.1%, being the highest in mowed wetlands and the lowest in heavily grazed wetlands. The linear regression further indicated that the plant diversity index was negatively correlated with the aboveground biomass of grasses and positively correlated with the aboveground biomass of forbs. Therefore, the land use changes in wetlands drove the replacement of dominant species of wetland vegetation and changed plant community characteristics and the species diversity, and the maintenance of species diversity is linked with the variability in plant functional strategies. The results of community variations and their relationships with functional changes can be used for assessing the effects of degradation and ecological function in response of land use changes in wetlands.

Aboveground net primary productivity was not limited by phosphorus in a temperate typical steppe in Inner Mongolia

AbstractPhosphorus (P) is an essential element for plant growth, however, whether the aboveground net primary productivity (ANPP) of typical steppe was limited by P remains obscure. To detect the effects of P addition on primary productivity and aboveground biomass of different plant functional groups both under ambient and N addition conditions, ANPP and aboveground biomass of grasses and forbs were measured from 2016 to 2020 on a 16-year N and P addition experiment platform in a temperate typical steppe in Inner Mongolia. The soil available N and P concentrations were also determined to test the relationship between ANPP and the availability of soil nutrients. We found that P addition under ambient condition had no significant effect on ANPP and the aboveground biomass of grasses and forbs. However, under N addition, P addition significantly increased ANPP and the aboveground biomass of forbs. Furthermore, soil available N and P concentrations were increased significantly by N and P addition, respectively. Moreover, there was no significant correlation between ANPP and soil available P concentration, while ANPP was positively correlated with soil available N concentration. These results suggest that P is not the key factor limiting the primary productivity of the temperate typical steppe in Inner Mongolia. However, under N addition, P addition can promote ANPP and alter the community composition. These findings provide valuable information for the management of the temperate typical steppe.

Changes in vegetation parameters and soil nutrients along degradation and recovery successions on alpine grasslands of the Tibetan plateau

Understanding the changes in vegetation parameters and soil nutrients in the different stages of grasslands degradation and recovery is crucial for assessing and restoring degraded grasslands. Consequently, we determined above-ground vegetation and soil C, N and P concentrations and their stoichiometry in different degradation and recovery stages on the Tibetan Plateau. Four degradation succession stages, GKC: Grass-Kobresia community, KHC: Kobresia humilis community, KPC: Kobresia pygmaea community, and FBC: forbs - black soil beach community, and three recovery succession stages, FG: freely grazed, RG: restricted grazed, and NG: non-grazed, were identified. Above-ground biomass and vegetation coverage decreased with degradation succession and there was a concomitant shift of plant functional groups to more above-ground biomass of forbs and less biomass of grasses and sedges. The highest species diversity emerged in the K. pygmaea succession stage, mainly due to an influx of Compositae. Significant differences in soil total nitrogen (TN), total phosphorus (TP) and soil organic carbon (SOC) concentrations occurred in the 0–10 and 10–20 cm layers among degradation successions. Vegetation cover, above-ground biomass, soil TN and SOC, as well as C:N and C:P ratios increased in non-grazed grasslands when compared to grazed grasslands. Soil TN, TP and SOC concentrations decreased with increasing soil depths across all degradation and recovery successions. In addition, soil nutrients and their stoichiometry were affected by above-ground biomass. We concluded that grazing exclusion could improve the above-ground vegetation and soil nutrients of degraded alpine grasslands, but that the rate of recovery was related to the degree of degradation.

Abiotic and biotic drivers of aboveground biomass in semi-steppe rangelands

Rangelands play an important role in the biodiversity conservation and ecosystem functions. Yet, few studies have assessed the effects of biotic and abiotic factors on aboveground biomass across plant growth forms and at whole-community level in rangelands. Here, we hypothesized that aboveground biomass is driven by both biotic (plant coverage, species richness and evenness) and abiotic factors (soil textural properties and topographic factors) but biotic factors may best predict aboveground biomass, probably due to small spatial scale. To test this hypothesis, we performed multiple linear mixed model by including abiotic and biotic factors as fixed effects while sites aspects and plant community types across sites, and disturbance intensities as random effects, using data from 735 quadrats across 35 sites in semi-steppe rangelands in Iran. The optimal model for shrubs showed that aboveground biomass was positively related to plant coverage, species richness, elevation, sand, silt and clay. Aboveground biomass of forbs and grasses was positively related to plant coverage, species richness, elevation and slope. Whole-community aboveground biomass was positively related to plant coverage, species richness and elevation, but negatively to species evenness and slope. We conclude that higher aboveground biomass is related to high species richness and plant coverage, and located on high elevation and/or slope across plant growth forms while having medium-coarse-textured to fine-textured soils for adaptation of shrubs only. Few dominant species or niche overlap in whole-community may also drive high aboveground biomass, and located on high elevation with gentle slope. Therefore, we found support for both the niche complementarity and selection effects across plant growth forms and at whole-community. In addition, this study shows that plant coverage is the best proxy for aboveground biomass in the studied rangelands.

Dynamic of grassland biomass in different degenerative stages

The dynamics of plant community and above- and belowground biomass of the different degenerative stages was researched ofKobresia humlis meadows of Nakchu prefecture in Tibet Autonomous Region. The results indicated that the aggravation of the degree of deterioration of alpine meadow is, the lower the vegetation coverage, percentage of excellent forage, and biodiversity are. The total aboveground biomass is highest in the lightly degraded stages while it is lowest in the extremely degraded stages. With the aggravation of degradation, the aboveground biomass of forbs increases while that of Cyperaceae decreases. We found that the belowground biomass was mostly distributed in the 0–10 cm soil depth in the alpine meadow with a “T”-shape distribution feature, and with the acceleration of deterioration, the numbers of roots becomes less and less. Meanwhile, the above- and belowground biomass of the different degraded communities was significantly correlated (r=0.963). There is an obvious positive correlation with the above- and belowground biomass in different degenerative stages, and their ratio increased with the aggravation of degradation.

Food and Habitat Preferences of Melanoplus sanguinipes and Aulocara elliotti (Orthoptera: Acrididae) on Disturbed Rangeland in Southern Idaho

Food habits of Melanoplus sanguinipes (F.) and Aulocara elliotti (Thomas), confined to cages containing crested wheatgrass, Agropyron desertorum (Fisch. ex Link) Schult.; cheatgrass, Bromus tectorum L.; and assorted forbs were examined in May, July, and August by microhistological techniques. Habitat preferences were determined by sampling the density and species composition of grasshoppers and the aboveground plant biomass at 44 locations during early July 1990. In May, caged A. elliotti consumed crested wheatgrass and cheatgrass in proportions equal to their relative availability. In July, A. elliotti fed mainly on crested wheatgrass. M. sanguinipes fed mainly on cheatgrass in May. In July and August, forbs comprised the major portion of the diet. Observed habitat preferences were consistent with predictions based on the food preferences of the two species. Density of M. sanguinipes was positively correlated with aboveground biomass of forbs and annual grasses. Density of A. elliotti was positively correlated with crested wheatgrass biomass and percent bare ground. The results indicate that rehabilitation of annual rangelands with crested wheatgrass can potentially affect the local distribution and abundance of these grasshopper species, possibly by altering their food resources.