Mm Of Mean Annual Precipitation Research Articles

Distribution, species richness, and relative importance of different plant life forms across drylands in China

Studies on plant diversity are usually based on the total number of species in a community. However, few studies have examined species richness (SR) of different plant life forms in a community along large-scale environmental gradients. Particularly, the relative importance (RIV) of different plant life forms in a community and how they vary with environmental variables are still unclear. To fill these gaps, we determined plant diversity of ephemeral plants, annual herbs, perennial herbs, and woody plants from 187 sites across drylands in China. The SR patterns of herbaceous plants, especially perennial herbs, and their RIV in plant communities increased with increasing precipitation and soil nutrient content; however, the RIV of annual herbs was not altered along these gradients. The SR and RIV of ephemeral plants were affected mainly by precipitation seasonality. The SR of woody plants had a unimodal relationship with air temperature and exhibited the highest RIV and SR percentage in plant communities under the harshest environments. An obvious shift emerged in plant community composition, SR and their critical impact factors at 238.5 mm of mean annual precipitation (MAP). In mesic regions (> 238.5 mm), herbs were the dominant species, and the SR displayed a relatively slow decreasing rate with increasing aridity, which was mediated mainly by MAP and soil nutrients. In arid regions (< 238.5 mm), woody plants were the dominant species, and the SR displayed a relatively fast decreasing rate with increasing aridity, which was mediated mainly by climate variables, especially precipitation. Our findings highlight the importance of comparative life form studies in community structure and biodiversity, as their responses to gradients differed substantially on a large scale.

Critical levels and nitrogen fertilizer equivalencies for grain protein in winter wheat

AbstractPrecision nitrogen (N) application methods have been developed for dryland wheat that utilize site‐specific measurements of grain protein concentration (GPC) to determine N fertilizer recommendations for the next season. The objectives of this study were to determine the critical protein level and N equivalent to a unit change in GPC from relationships between GPC, and grain yield or plant‐available N in soft white winter wheat (SWW, Triticum aestivum L.), and assess the consistency of these relationships across SWW cultivars grown under a wide range of precipitation. A 3‐year study was undertaken near two sites: Lexington (225 mm of mean annual precipitation) and Adams (450 mm) in Oregon. Differences in precipitation and N fertilization rates between sites were used to induce variability in grain yield and GPC of four cultivars. A critical protein concentration of 117.5 g kg−1 was defined by Cate–Nelson analysis of scatter plots of relative yield versus GPC. Critical protein among cultivars ranged between 105 and 118 g kg−1 suggesting that 117.5 g kg−1 might be used as a general indicator of N sufficiency. Slopes of the regression of available N on GPC were consistent across cultivars and revealed that 4.2–8.4 kg N ha−1 is equivalent to a unit change protein (1 g kg−1) in lower precipitation areas of the region where SWW is under water stress during grain filling. This information is useful in calculating the N to apply from the GPC in the previous season to meet crop requirements in the next season.

Tillage agriculture and afforestation threaten tropical savanna plant communities across a broad rainfall gradient in India

Abstract The consequences of land‐use change for savanna biodiversity remain undocumented in most regions of tropical Asia. One such region is western Maharashtra, India, where old‐growth savannas occupy a broad rainfall gradient and are increasingly rare due to agricultural conversion and afforestation. To understand the consequences of land‐use change, we sampled herbaceous plant communities of old‐growth savannas and three alternative land‐use types: tree plantations, tillage agriculture and agricultural fallows (n = 15 sites per type). Study sites spanned 457 to 1954 mm of mean annual precipitation—corresponding to the typical rainfall range of mesic savannas globally. Across the rainfall gradient, we found consistent declines in old‐growth savanna plant communities due to land‐use change. Local‐scale native species richness dropped from a mean of 12 species/m2 in old‐growth savannas to 8, 6 and 3 species/m2 in tree plantations, fallows and tillage agriculture, respectively. Cover of native plants declined from a mean of 49% in old‐growth savannas to 27% in both tree plantations and fallows, and 4% in tillage agriculture. Reduced native cover coincided with increased cover of invasive species in tree plantations (18%), fallows (18%) and tillage agriculture (3%). In analyses of community composition, tillage agriculture was most dissimilar to old‐growth savannas, while tree plantations and fallows showed intermediate dissimilarity. These compositional changes were driven partly by the loss of characteristic savanna species: 65 species recorded in old‐growth savannas were absent in other land uses. Indicator analysis revealed 21 old‐growth species, comprised mostly of native savanna specialists. Indicators of tree plantations (nine species) and fallows (13 species) were both invasive and native species, while the two indicators of tillage agriculture were invasive. As reflective of declines in savanna communities, mean native perennial graminoid cover of 27% in old‐growth savannas dropped to 9%, 7%, and 0.1% in tree plantations, fallows and tillage agriculture, respectively. Synthesis. Agricultural conversion and afforestation of old‐growth savannas in India destroys and degrades herbaceous plant communities that do not spontaneously recover on fallowed land. Efforts to conserve India's native biodiversity should encompass the country's widespread savanna biome and seek to limit conversion of irreplaceable old‐growth savannas.

Do limits exist on potential woody cover of Brazilian savanna?

With the increasing concern of woody plant encroachment worldwide in savanna ecosystems, many studies endeavor to examine the upper bound of woody plant cover, which is referred to as potential woody cover. Potential woody cover defines the maximum possible woody plant encroachment and bears strong implications on savanna dynamics. Both African and North American savannas have been reported to exhibit limits on potential woody cover below 650 and 660 mm of mean annual precipitation (MAP), respectively. At present it is less clear whether that limit exists and at what level in the Brazilian savanna (the Cerrado) of South America, throughout which MAP is above 790 mm. This study models the potential woody cover pattern of Brazilian savanna over the present precipitation gradient and in relation to surface and subsurface soil moisture (SM) separately. Remotely sensed products were processed in Google Earth Engine (GEE), and included MODIS tree cover (MOD44B), TRMM monthly precipitation (3B43), and NASA-USDA Enhanced SMAP Global soil moisture. Quantile regression results suggest that below respective thresholds of MAP, surface SM, and subsurface SM, potential woody cover in Brazilian savanna is constrained. Comparison to the savanna in central Texas of the United States reveals that water availability is not the only determinant of potential woody cover. Regional context such as precipitation seasonality and woody plant species are important factors. This study also underscores the discrepancy between potential woody cover modelled based on MAP and that based on soil moisture (surface and subsurface).

Controls on the presence and storage of soil inorganic carbon in a semi-arid watershed

Soil inorganic carbon (SIC) constitutes ∼40–50% of the terrestrial soil carbon and is an integral part of the global carbon cycle. Rainfall is a primary factor controlling SIC accumulation; however, the distribution and hierarchy of controls on SIC development in arid and semi-arid regions is poorly understood. The Reynolds Creek Experimental Watershed (RCEW) in southwestern Idaho is an ideal location to study factors influencing SIC because it spans a wide mean annual precipitation range (235 mm to 900 mm) along a 1,425 to 2,111 m elevation gradient and has soils derived from a wide variety of parent materials (granite, basalt, dust, and alluvium). We collected soil samples along this elevational gradient to understand local controls on SIC distributions. SIC content was quantified at 71 soil pits and/or augered cores collected between approximately 0–1 m depth or until refusal. Consistent with previous studies, we found variations in precipitation governed the presence or absence of SIC; field measurements of the top 1 m of soils confirm little or no SIC in soils receiving > 500 mm in mean annual precipitation. Below this 500 mm threshold, SIC pools varied substantially and significantly between sites. Results showed that 90% of sites (64 sites) contained less than 10 kg m−2 SIC, 7% (5 sites) contained 10–20 kg m−2, and 3% (2 sites) contain between 24 and 29 kg m−2 SIC. The total SIC within RCEW was estimated at ∼5.17 × 105 Mg. After precipitation, slope consistently ranked as the second most important predictor of SIC accumulation in random forest analysis. Wind-blown dust likely contributed to SIC accumulation; prior work indicates an average dust flux rate in RCEW of about 11 ± 4.9 g m−2 year−1. This study provides an initial model predicting SIC distribution and accumulation in a shrub-dominated dryland watershed.

Above- and belowground net-primary productivity: A field-based global database of grasslands.

Net primary productivity (NPP) over global grasslands is crucial for understanding the terrestrial carbon cycling and for the assessments of wild herbivores food security. During the past few decades, numerous field investigations have been conducted to estimate grassland NPP since the measuring criterion released by the International Biological Program. However, a comprehensive NPP database, particularly for belowground NPP (BNPP), in global grasslands is rare to date. Here, field NPP measurements from 438 publications (1957-2018) in global grasslands were collected, critically filtered, and incorporated in a comprehensive global database with observations for aboveground NPP (ANPP), BNPP, total NPP (TNPP), and BNPP fraction (fBNPP ). Associated information on geographical locations, climatic records, grassland types, land use patterns, manipulations subjected to manipulative experiments, sampling year of study sites, as well as NPP measurement methods are also documented. This database included 2985 entries from 1785 study sites. Among them, 806 entries contained paired data of ANPP and BNPP, resulting in the 806 fBNPP data. The study sites encompassed global grasslands with latitudinal range of 54.5° S~78.9° N, longitudinal range of 157.4° W~175.8° E, and altitudes from 0 to 5168 m above sea level, covering broad climatic gradients (-17.6 to 28.8°C in mean annual temperature and 63-2052 mm in mean annual precipitation). This global database is the world's largest paired data of ANPP and BNPP field measurements in grasslands. It can be used to study the spatio-temporal patterns of NPP and its allocation, evaluate the responses of above- and below-ground carbon components to future global changes, and validate the NPP estimation by empirical or process-based models in global grasslands. The database can be freely used for noncommercial applications. We kindly request users cite this data paper when using the database, respecting all the hard work during data compilation.

The role of plant functional groups mediating climate impacts on carbon and biodiversity of alpine grasslands

Plant removal experiments allow assessment of the role of biotic interactions among species or functional groups in community assembly and ecosystem functioning. When replicated along climate gradients, they can assess changes in interactions among species or functional groups with climate. Across twelve sites in the Vestland Climate Grid (VCG) spanning 4 °C in growing season temperature and 2000 mm in mean annual precipitation across boreal and alpine regions of Western Norway, we conducted a fully factorial plant functional group removal experiment (graminoids, forbs, bryophytes). Over six years, we recorded biomass removed, soil microclimate, plant community composition and structure, seedling recruitment, ecosystem carbon fluxes, and reflectance in 384 experimental and control plots. The dataset consists of 5,412 biomass records, 360 species-level biomass records, 1,084,970 soil temperature records, 4,771 soil moisture records, 17,181 plant records covering 206 taxa, 16,656 seedling records, 3,696 ecosystem carbon flux measurements, and 1,244 reflectance measurements. The data can be combined with longer-term climate data and plant population, community, ecosystem, and functional trait data collected within the VCG.

The absence of alternative stable states in vegetation cover of northeastern India.

Globally, forests and savannah are shown to be alternative stable states for intermediate rainfall regimes. This has implications for how these ecosystems respond to changing rainfall conditions. However, we know little about the occurrence of alternative stable states in forest ecosystems in India. In this study, we investigate the possibility of alternative stable states in the vegetation cover of northeastern India, which is a part of the Eastern Himalaya and the Indo-Burma biodiversity hotspots. To do so, we construct the so-called state diagram, by plotting frequency distributions of vegetation cover as a function of mean annual precipitation (MAP). We use remotely sensed satellite data of the enhanced vegetation index (EVI) as a proxy for vegetation cover (at 1 km resolution). We find that EVI exhibits unimodal distribution across a wide range of MAP. Specifically, EVI increases monotonically in the range 1000–2000 mm of MAP, after which it plateaus. This range of MAP corresponds to the vegetation transitional zone (1200–3700 m), whereas MAP greater than 2000 mm covers the larger extent of the tropical forest (less than or equal to 1200 m) of northeast India. In other words, we find no evidence for alternative stable states in vegetation cover or forest states at coarser scales in northeast India.

Late Quaternary Drainage Rearrangement Prevents the Vegetation Development in the La Tatacoa Intermontane Basin of the Colombian Andes

The Tatacoa Desert (TD) is a Cenozoic basin between the Central and Eastern Cordilleras in the southern Colombian Andes. Its sparse vegetation and Badlands morphology resemble a semi-arid environment, despite receiving ∼1,300 mm of mean annual precipitation. Based on optically stimulated luminescence dating in two fluvial terraces and drainage morphometric analysis, we propose that such “aridification” was imposed by a drainage reorganization during the Late Pleistocene. No river coming from the neighboring mountains flows into the TD. This makes the Tatacoa rivers unable to balance the evapotranspiration effect, causing a surficial water deficit. A fluvial terrace (TAT-2) works as a divide between the Tatacoa catchments and the Cabrera River, the latter coming from the Eastern Cordillera and bounding the TD towards the north. Paleocurrent measurements on its sedimentary lithic clasts point to a W-NW-directed flow into the TD. Thus, OSL ages around 74.1 ± 7.0 ka in this terrace suggest the TD was drained by an Eastern Cordillera catchment during the Late Pleistocene. At the western end of the TD, a dissected fluvial terrace (TAT-1) lying 80 m above the Magdalena River ages between 6.3 ± 1.5 and 7.7 ± 1.5 ka, representing the Holocene incision rates of 10.8 ± 0.3 mm/y. Coupled OSL data and river longitudinal profile analysis show a high susceptibility to erosion of the Tatacoa rocks and estimate incision rates ranging from 2–5 mm/y to 10–20 mm/y within the TD. The higher rates are concentrated along knickpoints related to anticlines and thrust faults. Thus, a northward shift of the Cabrera River and a westward migration of the Magdalena Valley have drastically reduced the surficial water availability in the Tatacoa and the development of vegetation, increasing erodibility. Potential climatic and tectonic drivers include 1) terrace accumulation during the wet periods of Marine Isotope Stage 5A and 1; 2) fault-induced incision of the Magdalena River in the NW, which would have favored northward migration of tributaries such as the Cabrera River; and 3) activity on the Baraya thrust fault, which would have prevented rivers from the Eastern Cordillera to enter the desert.

The Pedogenesis of Soil Derived from Carbonate Rocks along a Climosequence in a Subtropical Mountain, China

Revealing the pedogenesis of soil on carbonate rocks is a key step in determining the boundaries of soil types along a climosequence. However, related research is lacking for a subtropical mountain. In this study, eight pedons were sampled across an elevation gradient (789–2322 m) having large variation in mean annual precipitation (MAP) (1189–1764 mm) and mean annual temperature (MAT) (5.7–14.9 °C). General processes were performed, including physical, chemical, and morphological characterizations, X-ray diffraction (XRD), total elements’ content, and soil classification of the carbonate rock. In the climo-toposequence, the illite had been transformed into illite-smectite below 1300–1500 m of elevation, 1300–1370 mm of MAP, and above 10.5–11.5 °C of MAT, and into vermiculite above this climate. These findings indicated that the effects of temperature on soil mineral transformation had weakened with the gradual increases in elevation. The pedon at 861 m of elevation, 1206 mm of MAP, and 14.5 °C of MAT, which accounted for the argic horizons, was divided into Argosols after human activities. The finding revealed that changes from forest to cultivated land could potentially accelerate the formation of argic horizons, and it provided a theoretical basis for global carbonate rocks’ weathering conditions and ecological problems in subtropical mountains. When the soils reached approximately 1100–1200 m of elevation, 1250–1300 mm of MAP, and 11.5–13.5 °C of MAT, the argic horizons of the soil could be accounted for, as evolved from the Cambosols in Chinese Soil Taxonomy (CST) (Inceptisols in Soil Taxonomy (ST), Cambisols in the World Reference Base for Soil Resources (WRB)) to the Argosols in CST (Alfisols in ST, Luvisols or Alisols in WRB) under natural vegetation. Therefore, it was indicated that the soil types changed significantly in the CST, ST, and WRB with increases of MAP and decreases of MAT, which provides a reference for determining the boundaries of the soil types along a climosequence in subtropical mountains.

Woody species have stronger facilitative effects on soil biota than on plants along an aridity gradient

AbstractQuestionsWoody‐shrub encroachment affects community structure and composition. However, most studies focus on their effects on understorey plant communities, and the relative importance of shrubs in affecting plants vs soil biota communities is poorly known.LocationInner Mongolian Steppe, China.MethodsWe examined the effect of shrubs on multiple community attributes, including plants, soil biota (bacteria, fungi and nematodes), and soil fertility, and quantified how these effects changed from semi‐arid to hyperarid conditions (from 281 mm to 110 mm of mean annual precipitation). In addition, we assessed whether the effects of shrubs on plant communities were directly mediated by biotic filtering in seed germination and establishment, or indirectly mediated by plant biomass or soil fertility in the case of soil organisms.ResultsThe effect of shrubs on soil biota was generally more positive than on plants, and it increased with aridity. We found that a larger proportion of below‐ground taxa depended on shrub presence (36%) than plants (20%). Soil nematodes and soil bacteria were directly influenced by shrub presence whereas soil fungi were indirectly influenced by enhanced soil fertility. Shrubs also increased plant biomass under all conditions but only increased plant species richness in the most arid conditions. Despite the generally positive effect of shrubs, and the fact that they weakened the filtering effects of aridity on seed germination, aridity was a stronger predictor of changes in species composition than shrub presence was, particularly for plants.ConclusionsOur results illustrate the variety of positive effects of shrubs and show that they are particularly important in supporting biodiversity in the most arid conditions. These strong and positive effects could partially buffer the impacts of increasing aridity on dryland soil biodiversity, but our study suggests that facilitative interactions may not be able to completely mitigate the impacts of increasing aridity on drylands.

Modeling land surface processes over a mountainous rainforest in Costa Rica using CLM4.5 and CLM5

Abstract. This study compares the performance of the Community Land Models (CLM4.5 and CLM5) against tower and ground measurements from a tropical montane rainforest in Costa Rica. The study site receives over 4000 mm of mean annual precipitation and has high daily levels of relative humidity. The measurement tower is equipped with eddy-covariance and vertical profile systems able to measure various micrometeorological variables, particularly in wet and complex terrain. In this work, results from point-scale simulations for both CLM4.5 and its updated version (CLM5) are compared to observed canopy flux and micrometeorological data. Both models failed to capture the effects of frequent rainfall events and mountainous topography on the variables of interest (temperatures, leaf wetness, and fluxes). Overall, CLM5 alleviates some errors in CLM4.5, but CLM5 still cannot precisely simulate a number of canopy processes for this forest. Soil, air, and canopy temperatures, as well as leaf wetness, remain too sensitive to incoming solar radiation rates despite updates to the model. As a result, daytime vapor flux and carbon flux are overestimated, and modeled temperature differences between day and night are higher than those observed. Slope effects appear in the measured average diurnal variations of surface albedo and carbon flux, but CLM5 cannot simulate these features. This study suggests that both CLMs still require further improvements concerning energy partitioning processes, such as leaf wetness process, photosynthesis model, and aerodynamic resistance model for wet and mountainous regions.

Vegetation response to precipitation anomalies under different climatic and biogeographical conditions in China

Understanding precipitation-vegetation interaction is of great importance to implementing adaptation and mitigation measures for terrestrial ecosystems. Many studies have explored the spatial pattern of precipitation-vegetation correlation along the precipitation amount gradient. While the impacts of other precipitation characteristics remain poorly understood. Here, we provided a comprehensive investigation of spatiotemporal patterns of vegetation response to precipitation anomalies in China, using satellite-derived vegetation index and multi-source climate datasets for the years 1982–2015. Subsequently, we attempted to examine in detail what specific factors, climatic or biogeographic, are responsible for spatiotemporal patterns of precipitation-vegetation relationship. Results show that vegetation in Inner Mongolia Plateau is strongly affected by precipitation anomalies. Vegetation has a 1–2 month lag response to precipitation anomalies and is significantly correlated with 2–6 month cumulative precipitation anomalies. Seasonal differences of vegetation response are also remarkable. Moreover, the largest NDVI-precipitation correlation appears in areas with 150–500 mm of mean annual precipitation, 0.075–0.275 of fraction of precipitation days, and 19–23 of precipitation concentration index. More locally, the spatial distribution of NDVI-precipitation correlations is closely related to the vegetation type and elevation. The results can provide technical basis and beneficial reference to water resource and ecological management strategies in China for associated policymakers and stakeholders.

Temperature-induced growing season drought threatens survival and height growth of white spruce in southern Ontario, Canada

The adaptive capacity of boreal tree species to thrive in a warming, more variable climate has significant implications for boreal forest ecosystem structure and function. Dendrochronological and other empirical data indicate reduced growth and increased mortality of white spruce (Picea glauca [Moench] Voss) growing in warmer, drier portions of its natural range in western North America due to recent climate change. Comparatively, little is known of potential climate change effects on white spruce in the more mesic, eastern portion of its range where mean annual precipitation is relatively high. In this study, we examined the potential long-term consequences of climate warming on annual rates of mortality and height growth of mature white spruce by substituting space for time using data from 10, 31- to 40-year-old large common garden experiments (CGEs) established in Ontario, Canada. Across these CGEs, white spruce was exposed to differences of up to 5.0 °C in mean annual temperature and 405 mm in mean annual precipitation. During a 12- to 16-year measurement interval, mortality increased from the colder, more northern CGEs to the warmer CGEs near the species’ southern range margin. Along this climatic gradient, white spruce was also exposed to more frequent, severe growing season moisture deficits, with southern CGEs sometimes subject to extreme drought events with a low probability based on historical occurrence. Our results indicate that the severity of recent growing season drought events at more southern CGEs may have exceeded the drought tolerance capacity of white spruce and resulted in significantly increased mortality and reduced height growth rates. These results suggest that with projected increases in temperature and frequency/severity of growing season drought by the end of this century, white spruce is likely to experience maladaptation over a larger portion of its range in Ontario and gradually retract from its current southern range edge.

Meta-analysis of no-tillage effect on wheat and maize water use efficiency in China

No-tillage (NT) is a popular agricultural technique worldwide, but it remains unclear how NT affects the yield, evapotranspiration (ET), and water use efficiency (WUE) of maize and wheat. We performed a meta-analysis of the NT effects on the yield, ET and WUE for wheat and maize based on the literatures published during 1950–2018. Yield, ET, and WUE varied by species, region, and agronomic and environmental factors. Averaged across all the geographic locations NT had no effect on the yield, ET, or WUE of wheat in northwestern and northern China, and no effect on the yield or ET of maize, but significantly increased the maize WUE by 5.9%. NT increased the WUE and yield of wheat in regions with ≤400 mm of mean annual precipitation, increased the yield in regions with 400–600 mm of precipitation, and decreased the yield and ET in regions with ≥600 mm, but had no effects on maize. In the first 1–3 years of NT implementation, the wheat ET was reduced. However, a significant decrease in maize yield and ET occurred in 3–6 years of NT implementation. Meanwhile, yield and WUE in both wheat and maize were improved after >6 years. In general, NT effect on yield, ET, or WUE was not related to soil texture. However, NT increased maize WUE in a medium soil texture. Without crop rotation, NT increased wheat yield and ET but decreased maize yield. No NT effects were observed when crop residues retained and under crop rotation. Consequently, optimizing NT effects on yield, ET and WUE for wheat and maize in China was largely dependent on environmental conditions and management practices.

Responses and influencing factors of foliar photosynthetic characteristics of &amp;lt;italic&amp;gt;Larix gmelinii &amp;lt;/italic&amp;gt;to changing environments

Investigating tree photosynthetic capacity is important for understanding the carbon cycles of terrestrial ecosystems and their responses and adaptation to climatic change. Dahurian Larch ( Larix gmelinii ) is one of the dominant tree species in Chinese boreal forests with a broad bio-geographic range under divergent habitats, and thus an ideal tree species for exploring tree adaptation to environment. In this study, we measured the foliar photosynthesis and associated physiological parameters of 30-year-old Dahurian larch trees from six provenances in a common garden at the Maoershan Forest Ecosystem Research Station in Northeast China for three years (2009–2011). The six provenances were located across the natural distribution range of the larch, spanning approximately 4° in latitude (48°–52°N), 5°C in mean annual temperature ( - 2.3–2.6°C), and 200 mm in mean annual precipitation (425–622 mm). To access the top canopy of the sampled trees, we constructed 15-m-high wooden scaffolds at the site. Three representative trees from each provenance were selected for the measurements per month from mid May to mid September. We measured three fully expanded sunlit fascicles on young short shoots at the top of the canopy of each tree in situ with an infrared gas analyzer. On non-rainy days, light and CO2 response curves were measured between 06:30 and 12:00 hours under optimal conditions. Our goal was to explore impacts of environmental changes on foliar photosynthetic characteristics of the larch and their driving factors. The main results were summarized as follows: (ⅰ) The leaf-area-based maximum net photosynthetic rate ( P max-a), dark respiratory rate ( R a), apparent quantum yield (AQY), maximum rate of carboxylation ( V max), maximum electron transport rate ( J max) and triose phosphate utilization rate (TPU) all increased significantly ( P T s) and aridity index (AI) of the seed-source original sites, while the light compensation point (LCP) and photorespiratory rate ( R p) showed an opposite trend. This suggests that the leaf photosynthetic characteristics genetically adapt to the original site conditions of the tree seed-sources, among which the temperature and precipitation are the major driving factors. (ⅱ) P max-a was positively correlated with AQY, V max, J max, TPU, and leaf nitrogen concentration, but negatively with LCP and R p ( P T s habitats had higher sensitivity of P max-a associated with other characteristics. (ⅲ) P max-a was significantly and positively correlated with 3-day mean temperature, mean monthly temperature, mean growing season temperature, 3-day mean relative humidity, and mean monthly precipitation of the common garden, while the R a showed opposite trends with the environmental factors except for the mean growing season temperature. This indicates that the leaf photosynthetic characteristics acclimate to the environmental conditions of the common garden. However, the trees from higher T s habitats had lower intercepts of the regression equations of P max-a associated with the environmental factors, and had the opposite trends for R a except for the mean growing season temperature. The results suggest that the relationships between foliar photosynthetic characteristics and environment are jointly controlled by both phenotypic acclimation to current site conditions and genotypic adaptation to the original environment of the seed-source. These findings provide insights on understanding the survival, reproduction and distribution of Dahurian larch to changing environments.

Forest litterfall and its composition: a new data set of observational data from China

AbstractKnowledge of litterfall production and its allocation is important for understanding nutrient cycling and assessing productivity in forest ecosystems; however, available litterfall datasets are rare in China. Consequently, in the present study, data from published studies (1970–2014) on litterfall and its composition in forest ecosystems in China (excluding Hong Kong, Macao, and Taiwan) were collected, critically reviewed, and incorporated in a comprehensive forest litterfall data set for China. The data set included the following litterfall data: leaves, branches, reproductive parts (flowers and fruits), and miscellaneous. Moreover, associated information was also included, i.e., geographical location (latitude, longitude, altitude, aspect, and slope), climate [mean annual temperature (MAT) and mean annual precipitation (MAP)], stand description (forest type, dominant tree species, stand origin, stand age, mean DBH, mean tree height and stand density), and data collection regime (sample frequency and date, trap size, and number). The data set included 904 entries for 168 study sites, that were distributed in various climate zones with latitudes 18.26°–51.50° N, longitudes 82.25°–129.53° E and altitudes 0–4115 m above sea level (a.s.l.), covering broad climatic gradients (−5.4 to 25.4°C in MAT and 370 to 2800 mm in MAP). The data can be used to analyze spatio‐temporal dynamics of China's forest litterfall and its allocation, understand nutrient cycling and assess productivity in forest ecosystems. Finally, the data set is freely available for noncommercial scientific applications.

Plio-Pleistocene floras of the Vildštejn Formation in the Cheb Basin, Czech Republic — A floristic and palaeoenvironmental review

Plant fossil assemblages (foliage, fruits and seeds, pollen, wood) from the Pliocene and early Pleistocene deposits in W Bohemia (the Vildštejn Formation of the Cheb Basin, Tachov/Cheb–Domažlice/ Graben) are newly analysed using several palaeoenvironmental methods with the aim to reconstruct palaeovegetation and palaeoclimatic changes. Floras of four subsequent stratigraphic levels show a decrease of exotic elements in the Pliocene and a massive immigration of boreal elements in the early Pleistocene. Vegetation changes start with broad-leaved deciduous and mixed mesophytic forests and continue towards light forests of the mentioned types in areas of zonal to extrazonal habitats. This vegetational change is characterised by an immigration of dry herbaceous and sclerophyllous elements. Wetland communities from higher positions in the profiles stepwise loose exotic components and point to cool–temperate conditions similar to the present conditions. Palaeoclimatic signals show warmer and more humid conditions for the Pliocene levels (about 15°C of mean annual temperature, 5°C of mean temperature of the coldest month and 25°C of mean temperature of the warmest month, more than 900mm of mean annual precipitation). Early Pleistocene proxy data indicate the beginning of a cooler phase at the Plio-Pleistocene boundary (about 7°C of mean annual temperature and decreasing trend of precipitation), but conditions not colder than those of the present day in the NW part of the Bohemian Massif.

Styles and rates of long-term denudation in carbonate terrains under a Mediterranean to hyper-arid climatic gradient

Carbonate minerals, unlike silicates, have the potential to dissolve almost completely and with high efficiency. Thus, in carbonate terrains denudation rate and style (the governing process of denudation, mechanical or chemical) should be more sensitive to climatic forcing. Using 36Cl measurements in 39 carbonate bedrock and sediment samples, we calculate long-term denudation rates across a sharp climatic gradient from Mediterranean to hyper-arid conditions. Our samples were collected along the Arugot watershed, which drains the eastern flank of the Judea Range (central Israel) to the Dead Sea and is characterized by a pronounced rain shadow. Denudation rates of flat-lying bedrock outcrops sampled along interfluves differ by an order of magnitude from ∼20 mm ka−1 in the Mediterranean zone to 1–3 mm ka−1 in the hyper-arid zone. These rates are strongly correlated with precipitation, and thus reflect the importance of carbonate mineral dissolution in the overall denudation process. In contrast, denudation rates of steep bedrock surfaces depend on the hillslope gradient, but only in the hyper-arid climate zone, indicating that mechanical processes dominate the overall hillslope denudation within this zone. The dominance of slope-dependent mechanical erosion in the hyper-arid zone is also reflected by an increase in spatially-average denudation rates from 17–19 mm ka−1 in the Mediterranean–semi-arid zones to 21–25 mm ka−1 in the hyper-arid zone. These higher rates are attributed to clast contribution from steep slopes under arid climate. This suggests an increased importance of mechanical processes to the overall denudation in the hyper-arid zone.We demonstrate that the transition between chemically-dominated denudation to mechanically-dominated denudation occurs between 100 and 200 mm of mean annual precipitation. Long-term denudation rates across the Judea Range indicate that between Mediterranean and hyper-arid climates, chemical weathering rates are limited by precipitation. Nevertheless, in more humid climates, chemical weathering rates are apparently limited by the rates of carbonate mineral dissolution. This study demonstrates that carbonate terrains have the capacity to shift between mechanically and chemically dominated denudation in response to changes in precipitation. Similar transitions in response to changes in temperature or the level of tectonic activity have been previously reported. We suggest that the abrupt nature of such transitions can be primarily attributed to the efficiency of carbonate dissolution processes and the competition between surface and subsurface drainage systems in carbonate terrains.

Biomass and its allocation of Chinese forest ecosystems

Forest biomass and its allocation have long been considered important in forest ecosystem structure and function. However, discrete forest biomass data and its allocation to various forest components must be standardized to explore many ecological questions, e.g., plant allometric scaling laws, biomass allocation theory, and terrestrial carbon cycling. Currently, available data sets focus either on regions other than China, or studies in China are spatially and/or temporally limited, e.g., specific habitats and/or time periods. Therefore, the applicability of conclusions to world or China forests might be problematic. Consequently, in the present study, published studies (during the 1978–2008 period) on biomass and its allocations in China's forests (excluding Hong Kong, Macao, and Taiwan) were collected and critically reviewed, and a comprehensive forest biomass data set of China was developed. The data set included the following biomass data: tree overstory components (stems, branches, leaves, and roots, among all other plant material), the understory vegetation (saplings, shrubs, herbs, and mosses), woody liana vegetation, and the necromass components of dead organic matter (litterfall, suspended branches, and dead trees). Moreover, associated information was also included, i.e., geographical location, climate, soil fertility, stand description, sampling regime (the dimension and sample size of plots), and biomass measurement methods. The data set included 1607 entries for 348 study sites, which exhibited a broad spatial distribution, and covered broad climatic gradients (−5.1°C to 23.8°C in mean annual temperature and 223–2515 mm in mean annual precipitation). Our data set can be used to verify the accuracy of models used to budget China's forest carbon dynamics, and also provides an opportunity to further elucidate and confirm general principles and patterns in ecology. Finally, the data set is freely available for noncommercial scientific applications.