Latitudinal patterns of climatic variables and influence of local topography on climatic variables in the dry valleys of southwestern China

Climate is a key factor to determine the pattern of ecosystems;however,the latitudinal patterns of climatic variables in the arid and semiarid areas remain largely unclear when compared to humid areas.The topography of the dry valleys of southwestern China plays an important role in the formation of climate.However,its impact on the climate remains qualitative.In this study,eight climatic variables from 12 meteorological stations were analyzed to explore their latitudinal patterns in the wet and dry seasons from 1961 to 2019.We also quantified the effects of local topography(RH10)on the climatic variables.The results were as follows:sunshine duration,total solar radiation,average temperature,and evaporation decreased significantly,and wind speed increased significantly with increasing latitude in the annual,wet,and dry seasons(P<0.001).Relative humidity and precipitation decreased significantly with increasing latitude in the wet season(P<0.001),and no obvious change pattern was observed in the dry season.Aridity index significantly decreased(toward dryness)with increasing latitude in the wet season and increased in the dry season(P<0.001).Wind speed had a significantly positive relationship with topography(RH10)(P<0.01),whereas precipitation and aridity index were negatively associated with topography in the wet season and positively associated with topography in the dry season.Dryness was positively associated with RH10 in the wet season,and negatively in the dry season.The results of our research could provide new perspectives for understanding the relationship between topography and drought in the dry valleys of southwestern China.

The unimodal latitudinal pattern of K,Ca and Mg concentration and its potential drivers in forest foliage in eastern China

Potassium(K),calcium(Ca),and magnesium(Mg)are essential elements with important physiological functions in plants.Previous studies showed that leaf K,Ca,and Mg concentrations generally increase with increasing latitudes.However,recent meta-analyses suggested the possibility of a unimodal pattern in the concentrations of these elements along latitudinal gradients.The authenticity of this unimodal latitudinal pattern,however,requires validation through large-scale field experimental data,and exploration of the underlying mechanisms if the pattern is confirmed.Here,we collected leaves of common species of woody plants from 19 montane forests in the north-south transect of eastern China,including 322 species from 160 genera,67 families;and then determined leaf K,Ca,and Mg concentrations to explore their latitudinal patterns and driving mechanisms.Our results support unimodal latitudinal patterns for all three elements in woody plants across eastern China,with peak values at latitude 36.5±1.0°N.The shift of plant-functional-type compositions from evergreen broadleaves to deciduous broadleaves and to conifers along this latitudinal span was the key factor contributing to these patterns.Climatic factors,mainly temperature,and to a lesser extent solar radiation and precipitation,were the main environmental drivers.These factors,by altering the composition of plant communities and regulating plant physiological activities,influence the latitudinal patterns of plant nutrient concentrations.Our findings also suggest that high leaf K,Ca,and Mg concentrations may represent an adaptive strategy for plants to withstand water stress,which might be used to predict plant nutrient responses to climate changes at large scales,and broaden the understanding of biogeochemical cycling of K,Ca,and Mg.

Latitudinal variation of leaf morphological traits from species to communities along a forest transect in eastern China

Comprehensive information on geographic patterns of leaf morphological traits in Chinese forests is still scarce.To explore the spatial patterns of leaf traits,we investigated leaf area(LA),leaf thickness(LT),specific leaf area(SLA),and leaf dry matter content(LDMC) across 847 species from nine typical forests along the North-South Transect of Eastern China(NSTEC) between July and August 2013,and also calculated the community weighted means(CWM) of leaf traits by determining the relative dominance of each species.Our results showed that,for all species,the means(± SE) of LA,LT,SLA,and LDMC were 2860.01 ± 135.37 mm2,0.17 ± 0.003 mm,20.15 ± 0.43 m2 kg–1,and 316.73 ± 3.81 mg g–1,respectively.Furthermore,latitudinal variation in leaf traits differed at the species and community levels.Generally,at the species level,SLA increased and LDMC decreased as latitude increased,whereas no clear latitudinal trends among LA or LT were found,which could be the result of shifts in plant functional types.When scaling up to the community level,more significant spatial patterns of leaf traits were observed(R2 = 0.46–0.71),driven by climate and soil N content.These results provided synthetic data compilation and analyses to better parameterize complex ecological models in the future,and emphasized the importance of scaling-up when studying the biogeographic patterns of plant traits.

Warming-driven migration of core microbiota indicates soil property changes at continental scale

Terrestrial species are predicted to migrate northward under global warming conditions,yet little is known about the direction and magnitude of change in microbial distribution patterns.In this continental-scale study with more than 1600 forest soil samples,we verify the existence of core microbiota and lump them into a manageable number of eco-clusters based on microbial habitat preferences.By projecting the abundance differences of eco-clusters between future and current climatic conditions,we observed the potential warming-driven migration of the core microbiota under warming,partially verified by a field warming experiment at Southwest China.Specifically,the species that favor low p H are potentially expanding and moving northward to medium-latitudes(25°–45°N),potentially implying that warm temperate forest would be under threat of soil acidification with warming.The eco-cluster of high-p H with high-annual mean temperature(AMT)experienced significant abundance increases at middle-(35°–45°N)to high-latitudes(>45°N),especially under Representative Concentration Pathway(RCP)8.5,likely resulting in northward expansion.Furthermore,the eco-cluster that favors low-soil organic carbon(SOC)was projected to increase under warming scenarios at low-latitudes(<25°N),potentially an indicator of SOC storage accumulation in warmer areas.Meanwhile,at high-latitudes(>45°N)the changes in relative abundance of this eco-cluster is inversely related with the temperature variation trends,suggesting microbes-mediated soil organic carbon changes are more responsive to temperature variation in colder areas.These results have vital implications for the migration direction of microbial communities and its potential ecological consequences in future warming scenarios.

Contrasting phenology responses to climate warming across the northern extra-tropics

Climate warming has substantially advanced the timing of spring leaf-out of woody species at middle and high latitudes,albeit with large differences.Insights in the spatial variation of this climate warming response may therefore help to constrain future trends in leaf-out and its impact on energy,water and carbon balances at global scales.In this study,we used in situ phenology observations of 38 species from 2067 study sites,distributed across the northern hemisphere in China,Europe and the United States,to investigate the latitudinal patterns of spring leaf-out and its sensitivity(S T,advance of leaf-out dates per degree of warming)and correlation(R_(T),partial correlation coefficient)to temperature during the period 1980-2016.Across all species and sites,we found that S_(T) decreased significantly by 0.15±0.02 d℃^(-1)°N^(-1),and R_(T) increased by 0.02±0.001°N^(-1)(both at P<0.001).The latitudinal patterns in R_(T) and S_(T) were explained by the differences in requirements of chilling and thermal forcing that evolved to maximize tree fitness under local climate,particularly climate predictability and summed precipitation during the pre-leaf-out season.Our results thus showed complicated spatial differences in leaf-out responses to ongoing climate warming and indicated that spatial differences in the interactions among environmental cues need to be embedded into large-scale phenology models to improve the simulation accuracy.