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The storage of carbon in plant tissues and debris has been proposed as a method to offset anthropogenic increases in atmospheric [CO 2 ]. Temperate forests represent significant above-ground carbon (AGC) "sinks" because their relatively fast growth and slow decay rates optimise carbon assimilation. Fire is a common disturbance event in temperate forests globally that should strongly influence AGC because: discrete fires consume above-ground biomass releasing carbon to the atmosphere, and the long-term application of different fire-regimes select for specific plant communities that sequester carbon at different rates. We investigated the latter process by quantifying AGC storage at 104 sites in the Sydney Basin Bioregion, Australia, relative to differences in components of the fire regime: frequency, severity and interfire interval. To predict the potential impacts of future climate change on fire/AGC interactions, we stratified our field sites across gradients of mean annual temperature and precipitation and quantified within- and between-factor interactions between the fire and climate variables. In agreement with previous studies, large trees were the primary AGC sink, accounting for ~70% of carbon at sites. Generalised additive models showed that mean annual temperature was the strongest predictor of AGC storage, with a 54% near-linear decrease predicted across the 6.1°C temperature range experienced at sites. Mean annual precipitation, fire frequency, fire severity and interfire interval were consistently poor predictors of total above-ground storage, although there were some significant relationships with component stocks. Our results show resilience of AGC to frequent and severe wildfire and suggest temperature mediated decreases in forest carbon storage under future climate change predictions., (© 2018 John Wiley & Sons Ltd.)

Studying both soil carbon (C) and nitrogen (N) storages in different climate zones and their relationship with climatic factors is of great significance for understanding soil fertility and predicting global climate change. Climate influences soil minerals, which are important for soil organic carbon (SOC) and N retention. However, there are few studies on SOC and soil total nitrogen (STN) storage in different climatic zones, and of the effects of soil oxidation minerals on SOC and STN storage. We measured the storage of SOC and STN and the content of oxidizable minerals in soils from different climatic regions, then obtained climate data from the China Meteorological Data Service Center, and finally investigated the effects of climate factors and soil oxides minerals on SOC and STN. The results showed that climatic factors (mean annual temperature—MAT, mean annual precipitation—MAP, and ≥10 °C mean annual cumulative temperature—MACT) had significant effects on SOC and STN content, and there was significant epistatic clustering of SOC and STN contents in different climatic zones. When MAT, MAP, and MACT increased, SOC and STN storage showed a trend of increasing and then decreasing, and both SOC and STN storages were largest in the middle temperate zone. The content of soil metal oxides (Al2O3, Fe2O3, Na2O, MgO, CaO, K2O, and TiO2) showed significant positive correlation with climatic factors (MAT, MAP, and MACT). The contents of Al2O3, Fe2O3, CaO, K2O, and TiO2 showed significant negative correlation with SOC and STN contents. In summary, our results showed that, although soil metal oxides (SMO) have a protective effect on SOC and STN to some extent, they do not change the influence of climatic factors on SOC and STN storage. [ABSTRACT FROM AUTHOR]

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The Himalayan region is likely particularly exposed to climate change indicated by the high regional rate of change. The number of high-resolution, well-calibrated, and long-term paleoclimate reconstructions are however regrettably few, to set this change in a longer-term context. The dendroclimatic reconstructions over Himalaya that do exist have only reconstructed summer season temperatures, and rarely or never attempted to reconstruct mean annual temperatures. The paucity of long meteorological records is a matter of concern when developing chronologies of climate sensitive tree-ring data in Bhutan, but the chronologies would theoretically be of high potential for extending short meteorological records back in time using trees in high-elevation ecotones. The objectives of this study were to explore dendroclimatic signals in tree-ring width chronologies of Abies densa growing in these extreme ecotones and to reconstruct, if possible, annual temperatures over Northern Bhutan. A point-by-point regression analysis revealed that the regional composite chronology was significantly and positively correlated with temperatures of all months of the current year, i.e., January to December. The chronology was highly correlated with annual temperatures (calibration period R = 0.67 and validation period R = 0.50; p < 0.001) allowing a reconstruction of temperature over Northern Bhutan (NB-TEMR). The NB-TEMR reveals some common variations with summer temperature reconstructions of the Northern Hemisphere as well as the Himalayan region, particularly w.r.t to the recent warming trend. The reconstruction covers the period of 1765 to 2017. This reconstruction reveals a warming trend since 1850 with higher rates of warming 1935 to 2017, but with a pause around 1940–1970. The warming is consistent with reduced volcanic activity and increase of greenhouse gases. We anticipate that our new reconstruction of annual mean temperature could be an important contribution for future climate change studies and assessments of climate models. [ABSTRACT FROM AUTHOR]

The alpine treeline ecotones are an early indicator of vegetation's response to changes in climate, and the advancement of diffuse treeline ecotones has been associated with mean annual warming temperatures. However, the knowledge of how tree demographic size, age and population distribution, and regeneration decrease with increasing elevation and mean annual temperature remain fragmentary in Bhutan. There was no explanation of how treelines migrate in response to the climate. Therefore, the objectives of this study were to investigate tree demographic size and age and population distribution, as well as the regeneration expansion of treeline ecotones of Abies densa trees in response to climate change. Demographic data from thirty transect bands from treeline ecotones and reconstructed mean annual temperatures from tree-rings were used. Regression analysis was used to establish a relationship between elevation/temperature and demographic tree size and age, as well as to determine recruitment frequency distributions and whether these could be driven by climate change. The tree demography indicated that the treeline ecotone in our sampling site is temperature limited. Hence, cooler temperatures at higher elevations should drive decreases in basal diameter, age and recruitment frequencies. From the dendroecological analysis, the diffuse treeline ecotones appear to be climbing on average 1.00 m per year in Northern Bhutan. We also found that the recruitment frequency has increased over recent years (1850–2017), as temperatures continue to rise. The thermal treeline ecotones will be likely to serve as a line of bioclimatic reference against which other zones of bioclimate can be defined. With documented responses of treeline ecotones toward mean annual temperatures, the expectation is that additional warming will continue to influence regeneration expansion in the future. This dynamic response of treeline ecotones towards the climate acts as an indicator of climate change. Information about climbing treelines and altered ecotones should be a vital part of the material for decision makers to consider, to assess impacts and threats to Himalayan alpine biota. [ABSTRACT FROM AUTHOR]

Climate warming in the Russian Arctic over the past 40 years shows a variety of patterns at different locations and time periods. In the second half of the 20th century, the maximum rates of warming were characteristic of the subarctic permafrost regions of Russia. But in the 21st century, the locations of the greatest rates of climate warming moved to the Arctic zone of Russia. It was one of the reasons for a sharp increase in permafrost temperatures, an increase in the depth of seasonal thaw, and the formation of closed taliks. It was found that as a result of climate change, the differences in permafrost temperatures between different cryogenic landscapes in the area of continuous and discontinuous permafrost distribution have decreased, and in the area of sporadic permafrost distribution are now practically absent. The thermal regime of the ground shows dramatic changes everywhere with a pronounced reduction in the depth of zero annual amplitude. [ABSTRACT FROM AUTHOR]

Background: Forecasts of climate change impacts on biodiversity often assume that the current geographical distributions of species match their niche optima. However, empirical evidence has challenged this assumption, suggesting a mismatch. We examine whether the mismatch is related to functional traits along temperature or precipitation gradients. Methods: The observed distributions of 32 tree species in northeast China were evaluated to test this mismatch. Bayesian models were used to estimate the climatic niche optima, i.e. the habitats where the highest species growth and density can be expected. The mismatch is defined as the difference between the actual species occurrence in an assumed niche optimum and the habitat with the highest probability of species occurrence. Species’ functional traits were used to explore the mechanisms that may have caused the mismatches. Results: Contrasting these climatic niche optima with the observed species distributions, we found that the distribution–niche optima mismatch had high variability among species based on temperature and precipitation gradients. However, these mismatches depended on functional traits associated with competition and migration lags only in temperature gradients. Conclusions: We conclude that more relevant research is needed in the future to quantify the mismatch between species distribution and climatic niche optima, which may be crucial for future designs of forested landscapes, species conservation and dynamic forecasting of biodiversity under expected climate change. [ABSTRACT FROM AUTHOR]

The Himalayan region is likely particularly exposed to climate change indicated by the high regional rate of change. The number of high-resolution, well-calibrated, and long-term paleoclimate reconstructions are however regrettably few, to set this change in a longer-term context. The dendroclimatic reconstructions over Himalaya that do exist have only reconstructed summer season temperatures, and rarely or never attempted to reconstruct mean annual temperatures. The paucity of long meteorological records is a matter of concern when developing chronologies of climate sensitive tree-ring data in Bhutan, but the chronologies would theoretically be of high potential for extending short meteorological records back in time using trees in high-elevation ecotones. The objectives of this study were to explore dendroclimatic signals in tree-ring width chronologies of Abies densa growing in these extreme ecotones and to reconstruct, if possible, annual temperatures over Northern Bhutan. A point-by-point regression analysis revealed that the regional composite chronology was significantly and positively correlated with temperatures of all months of the current year, i.e., January to December. The chronology was highly correlated with annual temperatures (calibration period R = 0.67 and validation period R = 0.50; p < 0.001) allowing a reconstruction of temperature over Northern Bhutan (NB-TEMR). The NB-TEMR reveals some common variations with summer temperature reconstructions of the Northern Hemisphere as well as the Himalayan region, particularly w.r.t to the recent warming trend. The reconstruction covers the period of 1765 to 2017. This reconstruction reveals a warming trend since 1850 with higher rates of warming 1935 to 2017, but with a pause around 1940–1970. The warming is consistent with reduced volcanic activity and increase of greenhouse gases. We anticipate that our new reconstruction of annual mean temperature could be an important contribution for future climate change studies and assessments of climate models.

Tropical forests exert a disproportionately large influence on terrestrial carbon (C) balance but projecting the effects of climate change on C cycling in tropical forests remains uncertain. Reducing this uncertainty requires improved quantification of the independent and interactive effects of variable and changing temperature and precipitation regimes on C inputs to, cycling within and loss from tropical forests. Here, we quantified aboveground litterfall and soil‐surface CO2 efflux ("soil respiration"; FS) in nine plots organized across a highly constrained 5.2°C mean annual temperature (MAT) gradient in tropical montane wet forest. We used five consecutive years of these measurements, during which annual rainfall (AR) steadily increased, in order to: (a) estimate total belowground C flux (TBCF); (b) examine how interannual variation in AR alters the apparent temperature dependency (Q10) of above‐ and belowground C fluxes; and (c) quantify stand‐level C allocation responses to MAT and AR. Averaged across all years, FS, litterfall, and TBCF increased positively and linearly with MAT, which accounted for 49, 47, and 46% of flux rate variation, respectively. Rising AR lowered TBCF and FS, but increased litterfall, with patterns representing interacting responses to declining light. The Q10 of FS, litterfall, and TBCF all decreased with increasing AR, with peak sensitivity to MAT in the driest year and lowest sensitivity in the wettest. These findings support the conclusion that for this tropical montane wet forest, variations in light, water, and nutrient availability interact to strongly influence productivity (litterfall+TBCF), the sensitivity of above‐ and belowground C fluxes to rising MAT (Q10 of FS, litterfall, and TBCF), and C allocation patterns (TBCF:[litterfall+TBCF]). [ABSTRACT FROM AUTHOR]

Climate warming in the Russian Arctic over the past 40 years shows a variety of patterns at different locations and time periods. In the second half of the 20th century, the maximum rates of warming were characteristic of the subarctic permafrost regions of Russia. But in the 21st century, the locations of the greatest rates of climate warming moved to the Arctic zone of Russia. It was one of the reasons for a sharp increase in permafrost temperatures, an increase in the depth of seasonal thaw, and the formation of closed taliks. It was found that as a result of climate change, the differences in permafrost temperatures between different cryogenic landscapes in the area of continuous and discontinuous permafrost distribution have decreased, and in the area of sporadic permafrost distribution are now practically absent. The thermal regime of the ground shows dramatic changes everywhere with a pronounced reduction in the depth of zero annual amplitude.

Abstract Perennial grasses are touted as sustainable feedstocks for energy production. Such benefits, however, may be offset if excessive nitrogen (N) fertilization leads to economic and environmental issues. Furthermore, as yields respond to changes in climate, nutrient requirements will change, and thus guidance on minimal N inputs is necessary to ensure sustainable bioenergy production. Here, a pairwise meta-analysis was conducted to investigate the effects of N fertilization (amount and duration) and climate on the above-ground biomass yields of miscanthus (Miscanthus x giganteus) and switchgrass (Panicum virgatum L.). Both regression models and meta-analyses showed that switchgrass was more responsive to N than miscanthus, although both showed significant and positive N effects. Meta-analysis further showed that the positive growth response of miscanthus to N application increased with N addition rates of 60–300 kg N ha−1 year−1, but the magnitude of the response decreased with the number of years of fertilization (duration). N effects on switchgrass biomass increased and peaked at rates of 120–160 kg N ha−1 year−1 and 5–6 years of N inputs, but diminished for rates >300 kg N ha−1 year−1 and >7 years. Meta-analysis further revealed that the influences of N on switchgrass increased with both mean annual temperature and precipitation. Miscanthus yields were less responsive to climate than switchgrass yields. This meta-analysis helps fill a gap in estimation of biofeedstock yields based on N fertilization and could help better estimate minimum N requirements and soil management strategies for miscanthus and switchgrass cultivation across climatic conditions, thereby improving the efficiency and sustainability of bioenergy cropping systems. Highlights • Switchgrass was more responsive to N fertilization than miscanthus. • Miscanthus biomass increased to N addition rates, but response decreased with years. • Excessive N addition rates and duration did not further increase switchgrass yields. • N effects on switchgrass depend on annual mean temperature and precipitation. [ABSTRACT FROM AUTHOR]

Background and aims: In upland ecosystems, climate and initial litter quality are the two major factors influencing decomposition rates regionally and globally. Litters are exposed to a different decomposition environment in wetlands than in upland ecosystems, but the driving factors of litter decomposition in wetlands at a large scale are still unclear. Methods: We established a comprehensive database of litter decomposition in China, including 249 datasets and 27 pairs of sites, to examine the controlling factors of decomposition in both wetland and upland ecosystems at the regional scale. Results: Both ecosystems showed similar climatic conditions, but the average litter decomposition potential was higher in wetlands than in upland ecosystems, as indicated by a higher initial K content and lower initial carbon content. The average decomposition rate in wetlands was almost 3 times higher than that in upland ecosystems. In both ecosystems, the decomposition rate increased with the mean annual temperature, mean annual precipitation, and initial N content. However, linear regressions of these variables with the decomposition rate indicated steeper slopes in wetlands than in upland ecosystems. Conclusions: The litter decomposition rate responded to climate and initial N content in both ecosystem types, but these responses were more rapid in wetlands than upland ecosystems. Wetland ecosystems should be given more attention when studying the responses of litter dynamics to future climate changes. [ABSTRACT FROM AUTHOR]

• New expanded dataset was used to assess ecosystem soil respiration of China. • Increased grassland Rs contributed the most to the overall rise of Rs in China. • Increasing precipitation caused an increase in soil respiration in grasslands. • The temporal response of Rs to environment differed from that on spatial scale. In the context of increasing CO 2 concentrations and climate warming, there are large uncertainties regarding the regulatory mechanisms of soil respiration and its accurate assessment. As an area sensitive to global climate change, China covers a broad range of longitudes, latitudes, and altitudes, and it is of great significance to study the spatial and temporal patterns of soil respiration and its environmental response in China's terrestrial ecosystems to clarify the mechanisms of regional and global carbon balance processes. Based on the expanded annual soil respiration dataset from 1993 to 2020, we evaluated soil respiration in China's terrestrial ecosystems and its responses to environmental factors. The mean annual soil respiration in China's terrestrial ecosystems was 777.90 ± 489.43 g C m −2 yr−1 by arithmetic averaging and 595.52 g C m −2 yr−1 by area weighting, with soil respiration in wetlands being higher than that of the forest, grassland, shrubland, cropland, and desert. Soil respiration showed a significant upward trend from 2000 to 2017, which was mainly caused by a significant increase in soil respiration in grasslands due to increasing precipitation. In addition, we found differences in the environmental factors influencing the interannual and spatial variability of soil respiration. The response sensitivities of soil respiration to environmental changes differed significantly among the various ecosystem types; however, these differences were not significant when comparing interannual and spatial scales. This study provides information on soil respiration in China's terrestrial ecosystem and highlights the importance of considering the two-dimensional responses of soil respiration to environmental changes in both time and space. [ABSTRACT FROM AUTHOR]

The nutritive quality in plant organs is related to the different partitioning patterns of nutrient resources among the organs under various environmental conditions. This study examined the relationship between the nutritive quality of pods and seeds in Zanthoxylum and environmental factors, such as temperature and preciptation by using numerous samples collected from Southwest China to the East China of Shandong peninsula. The increasing accumulations of N, P and C in seeds implied that the nutritive quality in seeds was higher at the regions with relative higher mean annual temperature (MAT) and mean annual precipitation (MAP), while that in pods was on the contrary. By contrast, pod nutritive content was relatively high, but seed nutritive content was relatively low at the regions with relative high MAT and MAP. In addition, C:N ratio in pods was significantly and negatively correlated with MAT and MAP, while that in seed was significantly and positively correlated with MAT and MAP. The partitioning patterns of N-compounds between pods and seeds reflected different nitrogen translocations in the plant organs under various climate condition. The N:P ratios were negatively correlated with MAP, implying a higher proportional allocation of P to seeds than that of N in the areas with a relative high MAP. Therefore, the strategies to assess pod nutritional quality should be taken into account for nutritive translocation under various environmental conditions. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) is a major component of the global carbon cycle and has a potentially large impact on the greenhouse effect. Paddy soils are important agricultural soils worldwide, especially in Asia. Thus, a better understanding of the relationship between SOC of paddy soils and climate variables is crucial to a robust understanding of the potential effect of climate change on the global carbon cycle. A soil profile data set ( n = 1490) from the Second National Soil Survey of China conducted from 1979 to 1994 was used to explore the relationships of SOC density with mean annual temperature (MAT) and mean annual precipitation (MAP) in six soil regions and eight paddy soil subgroups. Results showed that SOC density of paddy soils was negatively correlated with MAT and positively correlated with MAP ( P < 0.01). The relationships of SOC density with MAT and MAP were weak and varied among the six soil regions and eight paddy soil subgroups. A preliminary assessment of the response of SOC in Chinese paddy soils to climate indicated that climate could lead to a 13% SOC loss from paddy soils. Compared to other soil regions, paddy soils in Northern China will potentially more sensitive to climate change over the next several decades. Paddy soils in Middle and Lower Yangtze River Basin could be a potential carbon sink. Reducing the climate impact on paddy soil SOC will mitigate the positive feedback loop between SOC release and global climate change. [ABSTRACT FROM AUTHOR]

• A tree recruitment model was developed for oaks (Quercus spp.) in Hunan Province, south-central China. • Mean annual temperature significantly affected the occurrence probability and counts of oaks recruitment. • The performance of the models improved significantly when the random effects were added. Tree recruitment is an essential component and plays a fundamental role in forest management decision-making. However, the existing tree recruitment models for oak (Quercus spp.) species have been developed using traditional modeling functions, and have neglected the effects of climate, which do not apply to long-term projections of future forest composition under a climatic change scenario. In this study, we developed tree recruitment models based on the data of 548 permanent sample plots distributed in Hunan Province, south-central China. Five commonly used recruitment approaches (negative binomial model, zero-inflated Poisson, zero-inflated negative binomial model, Hurdle-Poisson model, and Hurdle-negative binomial model) were employed to analyze the data. Then the random effects of the regions were included to develop the nonlinear mixed-effects models and account for spatial and temporal correlations. Among the various candidate predictors tested including stand characteristics, site conditions, and climate, stand basal area (BA), quadratic mean diameter (QMD), basal area of the species (Bai), cosine of the slope combined with the natural logarithm of elevation (CIE), and mean annual temperature (MAT) had significant effects on oak recruitment. The zero-inflated negative binomial model was selected as the optimal model compared to the other four basic models. The performance of the models improved significantly when the random effects were added. These results and knowledge of adaptive management will be useful for developing practical forest management plans. [ABSTRACT FROM AUTHOR]

Understanding changes in plant diversity is important with changing climate in desert ecosystems. We analyzed the changes in species richness and plant functional types in different landscape positions and species turnover between five sub-regions of the Gurbantünggüt Desert, China, from 2009 to 2013. We also analyzed how species density, richness, and plant functional types responded to annual precipitation, mean annual temperature, and the coefficient of variation ( C) of both daily precipitation and monthly temperature, throughout this entire desert region. The results showed significant differences in the Shannon-Weiner, Evenness, and Gleason indices between the sub-regions over the 5-year study period. Species richness varied in the order of ephemeral plants > long-lived annual plants > perennial herbs > shrubs. Species richness in the lower and inter-dune area was higher than on the upper dune and on top of dunes. About 34.8 % of total species were influenced by climate change. The density of about 8.7 % of total species declined with increasing precipitation, especially the two dominant species, Haloxylon persicum and Haloxylon ammodendron. Plant richness increased significantly with increased precipitation. Ephemeral plant made the largest contribution to increasing plant diversity in the desert, while shrubs made the smallest. Ephemeral plants play an important role in maintaining plant community composition and function. In addition, species turnover declined with increasing precipitation. We suggest that differences in flora and different landscape positions in the dunes, specifically in shaping the heterogeneous microhabitats, are important reasons for the complex responses of species to climate change. [ABSTRACT FROM AUTHOR]

Climate and initial litter quality are the major factors influencing decomposition rates on large scales. We established a comprehensive database of terrestrial leaf litter decomposition, including 785 datasets, to examine the relationship between climate and litter quality and evaluate the factors controlling decomposition on a global scale, the arid and semi-arid (AS) zone, the humid middle and humid low (HL) latitude zones. Initial litter nitrogen (N) and phosphorus (P) concentration only increased with mean annual temperature (MAT) in the AS zone and decreased with mean annual precipitation (MAP) in the HL zone. Compared with nutrient content, MAT imposed less effect on initial litter lignin content than MAP. MAT were the most important decomposition driving factors on a global scale as well as in different climatic zones. MAP only significantly affected decomposition constants in AS zone. Although litter quality parameters also showed significant influence on decomposition, their importance was less than the climatic factors. Besides, different litter quality parameters exerted significant influence on decomposition in different climatic zones. Our results emphasized that climate consistently exerted important effects on decomposition constants across different climatic zones. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau (TP) is experiencing high rates of climatic change. We present a novel combined mechanistic–bioclimatic modeling approach to determine how changes in precipitation and temperature on the TP may impact net primary production (NPP) in four major biomes (forest, shrub, grass, desert) and if there exists a maximum rain use efficiency (RUEMAX) that represents Huxman et al.'s “boundary that constrain[s] site‐level productivity and efficiency.” We used a daily mechanistic ecosystem model to generate 40‐yr outputs using observed climatic data for scenarios of decreased precipitation (25–100%); increased air temperature (1°–6°C); simultaneous changes in both precipitation (±50%, ±25%) and air temperature (+1 to +6°C) and increased interannual variability (IAV) of precipitation (+1σ to +3σ, with fixed means, where σ is SD). We fitted model output from these scenarios to Huxman et al.'s RUEMAX bioclimatic model, NPP = α + RUE × PPT (where α is the intercept, RUE is rain use efficiency, and PPT is annual precipitation). Based on these analyses, we conclude that there is strong support (when not explicit, then trend‐wise) for Huxman et al.'s assertion that biomes converge to a common RUEMAX during the driest years at a site, thus representing the boundary for highest rain use efficiency; the interactive effects of simultaneously decreasing precipitation and increasing temperature on NPP for the TP is smaller than might be expected from additive, single‐factor changes in these drivers; and that increasing IAV of precipitation may ultimately have a larger impact on biomes of the Tibetan Plateau than changing amounts of rainfall and air temperature alone. [ABSTRACT FROM AUTHOR]

Abstract: Natural abundance of radiocarbon (14C) has been applied to estimate the turnover time of soil carbon (C) across different climate regions. However, despite the important functional role played by soil animals in decomposition processes, little is known about variation in their 14C concentrations across different climate regions. In this study, we measured 14C concentrations of earthworms collected in three forests in Japan. In addition, we also reviewed 14C data on earthworms that were previously reported. We used these data to test whether the diet ages (defined as time elapsed since C in the diet of earthworms was fixed from atmospheric CO2 by photosynthesis) differed according to feeding habits and across study sites in various climate regions ranging from cool temperate forest to tropical savanna. Multiple regression analysis showed that the diet ages of earthworms were significantly affected by both feeding habits and study sites. The diet ages of endogeic (soil-feeding) earthworms (8.3±0.4 years, mean±SE) were significantly older than those of epigeic (litter-feeding) earthworms (2.6±0.5 years), with anecic (litter-/soil-feeding) earthworms (5.7±0.9 years) having intermediate diet ages. When mean diet age was compared for each feeding habit, only that of endogeic earthworms differed significantly across the sites. However, it did not necessarily become younger in warmer climate regions. These results either suggest that the degree of decomposition of soil organic matter used by earthworms differs among the study sites, or that the difference in the turnover time of soil organic C used by earthworms across the sites is relatively small and variable due to factors other than temperature, such as soil texture and vegetation. [Copyright &y& Elsevier]

Soils of the US Great Plains contain enormous stocks of soil organic carbon (SOC) and soil organic nitrogen (SON) that are vulnerable to predicted climate and land use change. Climate change scenarios predict a 2.2°C to 3.6°C (4°F to 6.5°F) increase and more vari-ability in precipitation across most of the United States. This study quantifies management effects (native grassland, Conservation Reserve Program [CRP], and cropped) on SOC and SON stocks across the region and assessed soil variables (soil texture, cation exchange capac-ity, and others) and climatic drivers (precipitation and temperature) to predict future changes in carbon (C) and nitrogen (N) stocks. Across all sites, cropped land had significantly lower C and N stocks in the 0 to 5 cm (0 to 2 in) and 0 to 10 cm (0 to 3.9 in) depths than native sites, while CRP sites were intermediate. Mean annual temperature (MAT), the ratio of mean annual precipitation to potential evapotranspiration (MAP:PET), soil bulk density (BD), and clay content were important covariates for SOC and SON stocks within land use. Soil C and N stocks under all three land uses were strongly negatively related to MAT and positively related to MAP:PET, suggesting that they are equally vulnerable to increased temperature and decreasing water availability. Based on these empirical relationships, a 1°C (1.8°F) increase in MAT could cause a loss of 486 Tg SOC (536 million tn) and a loss of 180 kg SON hac-1 (160 1b SON ac-1) from the top 10 cm (3.9 in) of soil over 30 years, but the decrease will be mediated by water availability (MAP:PET). Combined, increased temperature and conversion from CRP to cropland could decrease the existing SOC sink, but improved soil management and increased water availability may help offset these losses in the US Great Plains. [ABSTRACT FROM AUTHOR]

Previous comparative studies on patterns of reproduction in small-mammal species focus primarily on latitudinal differences in average litter size. Few studies compare reproductive patterns among northern and southern populations at the landscape scale. Our study compares differences in seasonal patterns of reproduction in northern and southern populations of the golden mouse, Ochrotomys nuttalli, and the white-footed mouse, Peromyscus leucopus. These are remarkably similar species with regard to bioenergetics, body mass, feeding behavior, home-range size, natural history, nest-site preference, and periods of activity. Both species also exhibit very similar intraspecific seasonal patterns of reproduction across their respective geographic ranges. We found that O. nuttalli and P. leucopus switch from a summer breeding season, extending from late spring through early autumn in the north to a winter breeding season extending from late autumn through early spring in the south, near the isotherm where mean annual temperature is 15.6°C (60°F), or approximately 35° N latitude. This latitudinal isotherm provides a geographic benchmark to address future changes in patterns of reproduction attributed to climate change. Findings also suggest that length of the breeding season and patterns of reproduction between species partially explain why P. leucopus is typically more abundant than O. nuttalli in similar habitat types. [ABSTRACT FROM AUTHOR]

Abstract: The coexistence approach (CA) is widely used to reconstruct palaeoclimates for the Cenozoic. Most published CA analyses relied on climate data for nearest living relatives (NLRs) stored in the Palaeoflora database (PFDB). Here, we used more than two-hundred modern relevés (taxon lists of forest stands) from North American, Caucasian and East Asian forest regions in order to test the ability of CA/PFDB to estimate palaeoclimate. Since only data for mean annual temperature (MAT) are publicly available from the PFDB, we concentrated on this climate parameter. Two criteria were tested: ‘resolution’ and ‘reliability’ of CA/PFDB analyses. The CA assumes that for a given climate parameter (e.g. MAT; mean annual precipitation; coldest month mean temperature etc.) the interval shared by all or nearly all NLRs for a fossil assemblage is best describing the past climatic conditions. Narrow, i.e. well-resolved, intervals are desirable, since they describe most precisely the climate. Our results show that CA/PFDB is unable to reliably reconstruct the actual climates of most of the relevés analysed. CA/PFDB performed best for lowland and mid-altitude stands with MAT of ca. 13–16°C, while producing remarkably incorrect results for warmer lowland stands and cooler stands at higher elevations. This is mainly due to generally incorrect entries of MAT ranges of NLRs in the PFDB. Using corrected MAT tolerances, the reconstructed, low-resolved intervals (3°C in exceptional cases, typically 5–10°C) fall within the actual climates. Hence, only dramatic climate changes are likely to be captured in a CA analysis. This renders the coexistence approach useless for the quantitative reconstruction of palaeoclimate and calls for alternative approaches of investigating past climates by means of fossil plants. [Copyright &y& Elsevier]

Past seasonality changes are often poorly represented by Quaternary proxies because one season, or one factor, dominates the reconstructed signal. During the early Holocene in New Zealand, mean annual temperatures were at least 1.5°C warmer than present. However, treelines were lower, suggesting summers were cooler. Here we use a forest ecosystem process model, LINKNZ, to explore past precipitation and temperature seasonality changes in an intermontane basin of the Southern Alps, New Zealand. Pollen and macrofossils from the basin show that during an early-Holocene warm event (11 500 to 9500 cal. yr BP) podocarp and broadleaved species dominated. In exploratory modelling runs, mean annual temperatures were increased by up to 2°C, precipitation was reduced by 20—30%, and temperature seasonality reduced. When mean annual temperature was increased by 1.0—2.0°C, LINKNZ reconstructed wet forest associations, very different to those in the early-Holocene fossil assemblages. Acceptable matches were made with the early-Holocene vegetation using elevated temperature scenarios with up to 30% lower annual precipitation and decreased temperature seasonality. Longer growing seasons apparently compensate for cooler summer temperatures. We suggest that during the early Holocene in this area, westerly wind flow over the Southern Alps to the west of the basin was less, reducing spill-over rainfall and vapour pressure deficits. Warm oceans generated milder, cloudier climates reducing seasonal contrasts. Inverse modelling is recommended as a tool for exploring past climate scenarios when proxies fail to reconstruct important climate variables. [ABSTRACT FROM AUTHOR]