Gas Exchange Rates of Texas Persimmon (Diospyros texana) in Central Texas Woodlands

Diospyros texana (Texas persimmon) is a secondary species in most Juniperus ashei/Quercus fusiformis woodlands in central Texas. It has high density, but plants are mostly in the community understory. Light response curves at ambient and elevated levels of CO2 and temperature were measured for D. texana. The Anet (photosynthetic rate) increased significantly as both light level and CO2 levels increased but not temperature. The Amax (maximum photosynthetic rate) of D. texana in full sun at elevated levels of CO2 was increased for all treatments. Stomatal conductance increased with levels of CO2 but only if the interaction was removed from the model. Intercellular levels of CO2 increased with both temperature and CO2 treatments as did water use efficiency (WUE). Furthermore, light saturation (Lsat) increased with CO2 treatments and light compensation (Lcp) increased with temperature. The dark respiration (Rd) increased with both temperature and CO2 treatments. Markov population models suggested D. texana populations would remain ecologically similar in the future. However, sub-canopy light levels and herbivory should be considered when examining population projections. For example, Juniperus ashei juveniles are not recruited into any canopy unless there are high light levels. Herbivory reduces the success of Quercus juveniles from reaching the canopy. These factors do not seem to be a problem for D. texana juveniles which would allow them to reach the canopy without need of a high light gap and are not prevented by herbivory. Thus, Juniperus/Quercus woodlands will change in the future to woodlands with D. texana a more common species.

Beyond biogeographic patterns:Processes shaping the microbial landscape in soils and sediments along the Yangtze River

Deciphering biogeographic patterns of microorganisms is important for evaluating the maintenance of microbial diversity with respect to the ecosystem functions they drives.However,ecological processes shaping distribution patterns of microorganisms across large spatial‐scale watersheds remain largely unknown.Using Illumina sequencing and multiple statistical methods,we characterized distribution patterns and maintenance diversity of microorganisms(i.e.,archaea,bacteria,and fungi)in soils and sediments along the Yangtze River.Distinct microbial distribution patterns were found between soils and sediments,and microbial community similarity significantly decreased with increasing geographical distance.Physicochemical properties showed a larger effect on microbial community composition than geospatial and climatic factors.Archaea and fungi displayed stronger species replacements and weaker environmental constraints in soils than that in sediments,but opposite for bacteria.Archaea,bacteria,and fungi in soils showed broader environmental breadths and stronger phylogenetic signals compared to those in sediments,suggesting stronger environmental adaptation.Stochasticity dominated community assemblies of archaea and fungi in soils and sediments,whereas determinism dominated bacterial community assembly.Our results have therefore highlighted distinct microbial distribution patterns and diversity maintenance mechanisms between soils and sediments,and emphasized important roles of species replacement,environmental adaptability,and ecological assembly processes on microbial landscape.Our findings are helpful in predicting loss of microbial diversity in the Yangtze River Basin,and might assist the establishment of environmental policies for protecting fragile watersheds.

Variation in plant diversity and dominance across dune fixation stages in the Chinese steppe zone

Aims Our aim was to study how diversity and dominance of plant species and plant functional types(PFTs)change and covary across three dune fixation stages in the Chinese steppe zone.Methods In the Chinese steppe zone,we measured coverage,mean height and density of each plant species in three types of dunes(mobile,semi-fixed and fixed dunes)in four sites(Mu Us,Otindag,Hulunbeir and Horqin).Plant species were grouped into 24 PFTs according to their lifespan,photosynthetic pathway,reproductive mode and life form.Dominance of each plant species and PFT were determined,and species diversity and PFT diversity were quantified using Shannon–Wiener index.Important Findings PFT diversity was positively related to plant species diversity in each dune stage,but PFT diversity increased more with increasing plant species diversity in the mobile and semi-fixed dunes than in the fixed dunes.Dune fixation stage explained 87.2%of the variation in plant species diversity and 84.8%of the variation in PFT diversity.Dominant species and PFTs differed among the three dune fixation stages;the more fixed the dunes were,the more perennial,shrubby,clonal and C3 species co-dominated.Specifically,in mobile dunes annual C4 non-clonal herbs were the most dominant,and in semi-fixed and fixed dunes perennial C3 clonal shrubs were most dominant.