Effects Of Interannual Climate Variability Research Articles

Inter-annual variability of catchment water balance in a montane spruce forest

ABSTRACT Climatic conditions in temperate montane forests vary over multiple temporal scales. This study examines the effects of inter-annual climatic variability on the long-term water balance of a small headwater catchment with gradually changing vegetation characteristics. The research is based on direct observations of basic hydrological variables (precipitation, stream discharge), and process-based modelling of difficult-to-measure variables (forest transpiration, wet canopy evaporation, snow sublimation). The catchment water balance is evaluated in terms of the catchment water storage. The uncertainty of the estimated storage changes is expressed as a convolution of partial uncertainties associated with the individual components of catchment water balance. The results suggest a significant decrease of catchment water storage over the study period. The decrease is assumed to be caused by increasing winter temperatures, resulting in a more frequent occurrence of liquid precipitation and less prominent spring snowmelt. Considering vegetation’s conservative water-balance management proved essential for the studied environment.

Interannual climate variability has predominant effects on seedling survival in a temperate forest.

Mechanisms such as conspecific negative density dependence (CNDD) and niche partitioning have been proposed to explain species coexistence and community diversity. However, as a potentially important axis of niche partitioning, the role of interannual climate variability in driving local community dynamics remains largely unknown. Here we used a 15-year monitoring data set of more than 53,000 seedlings in a temperate forest to examine (1) what are the relative effects of interannual climate variability, biotic interactions, and habitat conditions on seedling survival; (2) how the effects of biotic interactions change with interannual climate variability, and habitat conditions; and (3) whether the impacts of interannual climate variability, biotic interactions, and habitat conditions differ with plant traits. Interannual climate variability accounted for the most variation in seedling survival at the community level, followed by biotic interactions, and habitat conditions. Increased snowpack and decreased minimum temperature during the non-growing season had positive effects on seedling survival. Effects of conspecific neighbor density were weakened in higher snowpack, effective accumulated temperature, elevation, and soil-resource gradient, but were intensified with increased ultraviolet radiation, maximum precipitation, minimum temperature, and soil moisture. In addition, the relative importance of interannual climate variability versus biotic interactions differed depending on species-trait groups. Specifically, biotic interactions for gravity-dispersed species had a larger effect size in affecting seedling survival than other trait groups. Also, gravity-dispersed species experienced a stronger CNDD than wind-dispersed, probably because wind-dispersed seedlings rarely had adult conspecifics nearby. We found that interannual climate variability was most strongly associated with seedling survival, but the magnitude of climatic effects varied among species-trait groups. Interannual climate variability may act as an inhibitor or accelerator to density-dependent interactions and should be accounted for in future studies, as both a potential direct and indirect factor in understanding the diversity of forest communities.

Effects of inter-annual climate variability on grape harvest timing in rainfed hilly vineyards of Piedmont (NW Italy)

The current scenario of global warming impacts viticulture, influencing grape and wine quality. A study was carried out in the “Basso Monferrato” region, a rainfed hilly vine-growing area in NW Italy, to investigate the relationships between climate variables and grape harvest dates. The dates of harvest for some local wine grape varieties were recorded from 1962 to 2019 in the Vezzolano Experimental Farm and surrounding vineyards. Three series of climate data were investigated by means of trend analysis for temperature variables, Huglin index, and precipitation during the growing period. A significant trend was found for temperature variables (positive) and harvest dates (negative), indicating anticipation of harvest beginning from 11.6 to 34.2 days in the 58-years study period, depending on the variety. The influence of increasing temperature and Huglin index in anticipating the harvest period, particularly the harvest beginning, was also highly significant for all the considered varieties and vineyards in the Monferrato area. Implication under a climate warming scenario, the relevance of having available continuous and homogeneous datasets and possible future studies were also discussed.

Effects of Anthropogenic Activity on Global Terrestrial Gross Primary Production

AbstractGross primary production (GPP) has been identified as the largest terrestrial carbon flux and the major driver of the growing biosphere uptake of carbon. Factorial simulations using several biosphere models have been used to estimate the effects of long‐term (>50 years) climate change on global terrestrial GPP. However, no study has integrated large‐ensemble climate simulation data into a biosphere model to realistically estimate global terrestrial GPP with associated uncertainty. Here we present a novel approach to estimate the global terrestrial long‐term GPP with associated climate data‐induced uncertainty that combines a diagnostic‐type biosphere model with a large‐ensemble climate simulation data set. We distinguish the effects of recent anthropogenic activity on global GPP (the anthropogenic GPP effect) from the effects of interannual climate variability (the natural GPP effect) by comparing GPP model estimates forced by historical and “nonwarming” climate data. We provide evidence for an increasing anthropogenic effect on global terrestrial GPP. The anthropogenic GPP effect is driven by CO2 fertilization, which is projected to weaken or saturate by 2050–2150, depending on the representative concentration pathway scenario used. Model results suggest that shortwave radiation couples with El Niño–Southern Oscillation conditions and volcanic eruptions to drive the natural GPP effect. Because shortwave radiation at the surface is related to cloud cover, we encourage future studies to focus on cloud‐radiation feedbacks on the carbon cycle.

Interannual climate variability and altered precipitation influence the soil microbial community structure in a Tibetan Plateau grassland

Climate change could influence aboveground and belowground plant community diversity and structure profoundly. However, our understanding of the responses of microbial communities to changes in both temperature and precipitation remains poor. Here, using 16S rDNA and ITS high throughput sequencing, we investigated the responses of soil bacterial and fungal community structure to both temperature and precipitation changes, and how such changes could influence interannual variability within soil microbial communities in a grassland in the Tibetan Plateau. The altered precipitation treatments had significant effects on soil bacterial and fungal community structure (F = 2.11, P = 0,001; F = 2.26. P = 0.001, respectively), while year had a more significant effect on soil bacterial and fungal community structure (F = 3.36, P = 0.001; F = 2.67, P = 0.001, respectively). The results showed that the interannual fluctuations in mean annual precipitation and mean annual temperature were significantly correlated with the interannual variations in soil bacterial and fungal community structures. In addition, the robustness of co-occurrence relationships among microbes could be strongly influenced by the altered precipitation and year. Overall, our results indicated that the effect of interannual climate variability on the soil microbial community was greater than the effect of a 1.6 °C increase in temperature. Our findings suggest an interactive effect of rapid interannual variability and slow climate change on the belowground soil microbial community structure.

Interdependent effects of climate variability and forest cover change on streamflow dynamics: a case study in the Upper Umvoti River Basin, South Africa

Streamflow dynamics are sensitive to both climate variability and land use change. However, estimating their separate and combined effects remains a research challenge. In South Africa, streamflow dynamics are important not only for irrigated agriculture but also for many rural communities that depend on streamflow for domestic water supply. In this paper, we analysed the effects of pine, wattle and eucalyptus plantation cover change vis-a-vis the effects of inter-annual climate variability on streamflow dynamics of the Upper Umvoti River in South Africa from 1994 to 2016. We modelled inter-annual variability in streamflow by precipitation, temperature and plantation cover using the Bayesian inference. We mapped plantation cover from Landsat satellite imagery. We found strong evidence for an interaction between temperature range and plantation cover net change on streamflow. Specifically, the plantation effect weakened under conditions of high-temperature range anomalies. We explain this interaction with a shift in soil water repellency and interception capacity within the plantation area under a changing temperature range, with important implications for the formation of surface runoff. Previous studies have assumed that the effects of climate variability and plantation cover change on streamflow dynamics are independent. Our results call this assumption into question. Hence, climate and land cover interdependencies should be accounted for in future statistical and process-based modelling studies.

5. The Effect of Climate Variability on Lake Water Balances and Water Quality in the Apex River Watershed, Baffin Island, Nunavut

Iqaluit, Nunavut is currently facing a water shortage as its population rises, and its drinking water reservoir, Lake Geraldine, is increasingly insufficient. The City of Iqaluit is currently looking into alternative sources of drinking water to supplement this reservoir. This study investigates the effects of inter-annual climate variability on the water chemistry of twenty Arctic lakes in a continuous permafrost region, and the potential implications of these changes on drinking water availability. The twenty lakes are located in the Niaqunguk (Apex) river watershed, Baffin Island, Nunavut (which is adjacent to the Lake Geraldine watershed at Iqaluit) were sampled annually during late July between 2014-2017. Ion concentrations and stable isotopes were measured for each lake annually throughout the study period to compare variability between lakes and between years. Water chemical and physical properties are used to gain insight into the inputs and outputs of each lake, and the changes in estimated water balance between years. This information will be used to determine the impact of different hydrological conditions on water chemistry. Results of water isotope tracers of the twenty lakes indicate that there are important year-to-year changes in the water stable isotopes, indicating inter-annual variations in evaporation rates, suggesting that these lakes are sensitive to changes in summer climatic conditions. Preliminary analyses of the ionic concentrations of the lakes suggest that ion concentrations generally decrease throughout the study period, and largely vary together, signifying the hydrological processes controlling the lake water balances are related to climate variability. This research will provide insights into the hydrologic response of lakes in a continuous permafrost region to long-term climatic change.

Winners and losers from climate change in agriculture: Insights from a case study in the Mediterranean basin

The Mediterranean region has always shown a marked inter-annual variability in seasonal weather, creating uncertainty in decisional processes of cultivation and livestock breeding that should not be neglected when modeling farmers' adaptive responses. This is especially relevant when assessing the impact of climate change (CC), which modifies the atmospheric variability and generates new uncertainty conditions, and the possibility of adaptation of agriculture. Our analysis examines this aspect reconstructing the effects of inter-annual climate variability in a diversified farming district that well represents a wide range of rainfed and irrigated agricultural systems in the Mediterranean area. We used a Regional Atmospheric Modelling System and a weather generator to generate 150 stochastic years of the present and near future climate. Then, we implemented calibrated crop and livestock models to estimate the corresponding productive responses in the form of probability distribution functions (PDFs) under the two climatic conditions. We assumed these PDFs able to represent the expectations of farmers in a discrete stochastic programming (DSP) model that reproduced their economic behaviour under uncertainty conditions. The comparison of the results in the two scenarios provided an assessment of the impact of CC, also taking into account the possibility of adjustment allowed by present technologies and price regimes. The DSP model is built in blocks that represent the farm typologies operating in the study area, each one with its own resource endowment, decisional constraints and economic response. Under this latter aspect, major differences emerged among farm typologies and sub-zones of the study area. A crucial element of differentiation was water availability, since only irrigated C3 crops took full advantage from the fertilization effect of increasing atmospheric CO2 concentration. Rainfed crop production was depressed by the expected reduction of spring rainfall associated to the higher temperatures. So, a dualism emerges between the smaller impact on crop production in the irrigated plain sub-zone, equipped with collective water networks and abundant irrigation resources, and the major negative impact in the hilly area, where these facilities and resources are absent. However intensive dairy farming was also negatively affected in terms of milk production and quality, and cattle mortality because of the increasing summer temperatures. This provides explicit guidance for addressing strategic adaptation policies and for framing farmers' perception of CC, in order to help them to develop an awareness of the phenomena that are already in progress, which is a prerequisite for effective adaptation responses.

Constraints on southern hemisphere tropical climate change during the Little Ice Age and Younger Dryas based on glacier modeling of the Quelccaya Ice Cap, Peru

Improving the late Quaternary paleoclimate record through climate interpretations of low-latitude glacier length changes advances our understanding of past climate change events and the mechanisms for past, present, and future climate change. Paleotemperature reconstructions at low-latitude glaciers are uniquely fruitful because they can provide both site-specific information and enhanced understanding of regional-scale variations due to the structure of the tropical atmosphere. We produce Little Ice Age (LIA) and Younger Dryas (YD) paleoclimate reconstructions for the Huancané outlet glacier of the Quelccaya Ice Cap (QIC) and low-latitude southern hemisphere regional sea surface temperatures (SSTs) using a coupled ice-flow and energy balance model. We also model the effects of long-term changes in the summit temperature and precipitiation rate and the effects of interannual climate variability on the Huancané glacier length. We find temperature to be the dominant climate driver of glacier length change. Also, we find that interannual climate variability cannot adequately explain glacier advances inferred from the geomorphic record, necessitating that these features were formed during past colder climates. To constrain our LIA reconstruction, we incorporate the QIC ice core record, finding a LIA air temperature cooling at the ice cap of between ∼0.7 °C and ∼1.1 °C and ∼0.4 °C and regional SSTs cooling of ∼0.6 °C. For the YD paleoclimate reconstructions, we propose two limits on the precipitation rate, since the ice core record does not extend into the Pleistocene: 1) the precipitation rate scales with the Clausius-Clapeyron relationship (upper limit on cooling) and 2) the precipitation rate increases by 40% (lower limit on cooling), which is an increase about twice as great as the regional increases realized in GCM simulations for the period. The first limit requires ∼1.6 °C cooling in ice cap air temperatures and ∼0.9 °C cooling in SSTs, and the second limit requires ∼1.0 °C cooling in ice cap air temperatures and ∼0.5 °C cooling in SSTs. Our temperature reconstructions are in good agreement with the magnitude and trend of GCM simulations that incorporate the forcing mechanisms hypothesized to have caused these climate change events.

The effects of interannual climate variability on the moraine record

Research Article| January 01, 2014 The effects of interannual climate variability on the moraine record Leif S. Anderson; Leif S. Anderson 1Institute of Arctic and Alpine Research, and Department of Geological Sciences, University of Colorado, Campus Box 450, Boulder, Colorado 80309, USA Search for other works by this author on: GSW Google Scholar Gerard H. Roe; Gerard H. Roe 2Department of Earth and Space Sciences, University of Washington, 4000 15th Avenue NE, Seattle, Washington 98195, USA Search for other works by this author on: GSW Google Scholar Robert S. Anderson Robert S. Anderson 1Institute of Arctic and Alpine Research, and Department of Geological Sciences, University of Colorado, Campus Box 450, Boulder, Colorado 80309, USA Search for other works by this author on: GSW Google Scholar Geology (2014) 42 (1): 55–58. https://doi.org/10.1130/G34791.1 Article history received: 20 May 2013 rev-recd: 15 Sep 2013 accepted: 19 Sep 2013 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Leif S. Anderson, Gerard H. Roe, Robert S. Anderson; The effects of interannual climate variability on the moraine record. Geology 2014;; 42 (1): 55–58. doi: https://doi.org/10.1130/G34791.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Valley glacier moraines are commonly used to infer past mean annual precipitation and mean melt-season temperature. However, recent research has demonstrated that, even in steady climates, multi-decadal, kilometer-scale fluctuations in glacier length occur in response to stochastic, year-to-year variability in mass balance. When interpreting moraine sequences it is important to include the effect of interannual weather variability on glacier length; moraines record advances that are forced either by interannual variability or by a combination of climate change and interannual variability. We address this issue for the Last Glacial Maximum (LGM) glaciers of the Colorado Front Range, United States. Using a linear glacier model that allows thorough exploration of parameter uncertainties, supplemented by a shallow-ice flowline model, our analyses suggest that (1) glacial standstills longer than 50 years were unlikely; (2) mean glacier lengths are ∼10%–15% up-valley from maximum glacier lengths; and (3) individual LGM terminal moraines were formed by a combination of a climate change and interannual variability–forced advances. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Evaluating the impacts of climate variability and disturbance regimes on the historic carbon budget of a forest landscape

Landscape-level understanding of forest carbon (C) dynamics is required to quantify the net contribution of forest biomes to the global C cycle and to help forest managers to understand the impacts of forest management activities on the C sequestration in forests. In this study, the effects of interannual climate variability, carbon dioxide (CO2) fertilization, and disturbance regimes on the C dynamics of an old-growth Pacific Northwest temperate conifer forest landscape (2500ha) were studied from 1920 to 2005, using a process-based land surface model, known as the Carbon and Nitrogen coupled Canadian Land Surface Scheme (CN-CLASS). The model was parameterized with ecological, forest inventory and historical land-use data, and run using historical meteorological observations. Before performing landscape level simulations, model results were evaluated against eddy covariance flux tower observations. Simulated mean annual net ecosystem productivity (NEP) over the flux tower footprint area was 340gCm−2yr−1 from 1998 to 2005, while the measured value was 293±20.5gCm−2yr−1. When two anomalous weather years, corresponding to El Niño (1998) and La Niña (1999) events, were excluded while performing statistical analysis, measured and simulated fluxes were highly, but negatively, correlated to both annual mean air temperature and annual precipitation (R2=0.69 and 0.60, respectively). Interannual variability of simulated and measured NEP over the flux footprint area, calculated as deviations of the respective annual NEP values, was 143gCm−2yr−1 and 61gCm−2yr−1, respectively. On the landscape-level, prior to disturbance in 1920, simulated C fluxes indicated that the forest landscape was close to C neutral, with annual net biome productivity (NBP) of 0.8gCm−2yr−1. However, during the intense disturbance period from 1938 to 1944, landscape-level NBP reached about −5083gCm−2yr−1. Then from 1951 to 1997, when there were no major disturbance events, NBP gradually recovered to about 365gCm−2yr−1. At the end of the study period, in 2005, the landscape again became C source, due to harvesting of second growth stands that occurred from late 1990s to 2000s.The regression of age-detrended variations in the simulated annual C fluxes to mean daily maximum air temperature over the peak growing season (July–September), during an undisturbed period from 1963 to 1984, indicated that summer temperature was the dominant climatic control on landscape-level C fluxes. Higher temperatures caused a decrease in gross primary productivity at almost twice the rate of increase in ecosystem respiration (i.e. 27gCm−2yr−1C−1 versus 15.7gCm−2yr−1C−1, respectively). A sensitivity analysis to evaluate the impacts of climate variability and disturbances showed that the relative effect of disturbance on carbon stocks was greater than the effect on carbon fluxes. Overall CO2 fertilization effects were minor. Disturbance type and severity, represented by the standard deviation in NBP, as described in the model, determined the magnitude of the simulated C losses to the atmosphere. This study enhances our understanding of the impacts of future climate change and forest management on landscape-level C dynamics in forests.

Effects of interannual climate variability on tropical tree cover

Climatic warming is intensifying the global water cycle, and is projected to increase rainfall variability. Higher interannual variability in rainfall is shown to reduce tree cover in the wet tropics, but may promote expansion of cover in tropical dry lands.

Interannual climate variability and population density thresholds can have a substantial impact on simulated tree species’ migration

Assessments of future tree species’ distributions should account for time lags in the adaptation of their external range limits to climatic changes. In simulation experiments it is therefore necessary to capture processes that influence such time lags, in particular tree species’ migration. We hypothesise that directional processes such as migration are sensitive to the exact sequence of simulated climate influences, and that the uncertainty associated with a given interannual climate variability has to be accounted for when simulating migration explicitly. In this paper we used the intermediate-complexity multi-species model TreeMig to examine whether different realisations of future climate influences with the same temporal mean and the same interannual variability cause fundamental differences in simulated migration. We assume that the impact of interannual climate variability becomes most apparent in situations which critically influence regeneration and survival. Such situations arise, for example, when species’ sensitivities to climate, competition and spatial fragmentation interact. We therefore developed an illustrative and realistic simulation setup representing this situation. We simulated the northwards migration of the sub-Mediterranean tree species Ostrya carpinifolia Scop. (European Hop Hornbeam) through the highly fragmented and climatically heterogeneous landscape of the Swiss Alps.Situations critically influencing regeneration and survival can lead to low species’ abundances. Before investigating effects of interannual climate variability, we therefore tested whether the continuous representation of species’ cell populations in TreeMig, which allows for infinitesimal population densities, can have side effects on simulated migration. Specifically, we tested for effects of minimum density thresholds, i.e. thresholds below which a species is treated as absent. We found that small thresholds in the magnitude of one individual per km2 cell have a considerable impact on simulated migration, and can even impede migration in situations critical for regeneration and survival.To test for effects of interannual climate variability, we compared simulation results from multiple repetitions driven by different annual climate time series generated stochastically from the same probability distribution. Results from these repetitions were additionally compared to results from simulations driven by cyclically repeated climate and steadily applied mean climate, respectively. These comparisons were conducted for different species parameter sets within the plausible parameter range of O. carpinifolia to account for potential interactions between species’ sensitivities and the environment. Simulated tree species’ migration was highly dependent on the species parameters applied and markedly influenced by interannual climate variability. Notable divergence in species’ spread resulted amongst multiple realisations of annual climate time series stochastically sampled from the same probability distribution. We conclude that uncertainty associated with interannual climate variability has to be accounted for. Single realisations can be insufficient and mean value simulations as well as averages of output results can be too simplistic to reflect possible outcomes of tree species’ migration.

Effect of inter-annual climate variability on evapotranspiration and canopy CO2 exchange of a tropical rainforest in Peninsular Malaysia

We investigated inter-annual variation of canopy CO2 exchange (NEE) and evapotranspiration during a 7-year period over a lowland Dipterocarp forest in Pasoh, Peninsular Malaysia, using the eddy covariance method. Annual rainfall fluctuated between 1,451 and 2,235 mm during this period. Annual evapotranspiration estimated by energy budget correction and gap filling using the relationship between latent heat and available energy was 1,287 ± 52 mm. Despite inter-annual variation in rainfall, annual evapotranspiration was stable, except for a slight decrease in the driest year (2009). Evapotranspiration was roughly related to the amount of available energy, but was regulated by stomatal closure to prevent excessive water loss at high vapour pressure deficit. Even during dry periods, no significant decrease in evapotranspiration occurred, as water was supplied from soil layers deeper than 0.5 m. Ecosystem respiration (RE) increased with soil water content. Daytime NEE was also stable during the 7 years, despite climate variability. Afternoon inhibition of canopy photosynthesis was seen every month. Daytime NEE did not become more negative with increasing solar radiation, or with increasing soil water content. During dry periods, gross primary production (GPP) and thus canopy gross photosynthesis decreased slightly, coupled with decreased daytime RE. In this forest, variability in rainfall pattern resulted in seasonal and inter-annual variability in micrometeorology; evapotranspiration, photosynthesis, and RE responded to these changes, and compensated for each other and/or other components of micrometeorology, resulting in rather stable annual evapotranspiration and NEE, even during a very dry year associated with an El Nino Southern Oscillation (ENSO) event.

Climate affects food availability to planktivorous least auklets Aethia pusilla through physical processes in the southeastern Bering Sea

Climate change might affect marine top predators by altering availability and nutritional quality of their prey. Climate effects vary on a regional basis, and our understanding of the relationships between fluctuations in climate and food resources in sub-arctic regions with seasonal ice cover is limited. We studied the effects of inter-annual climate variability (as reflected in the Pacific Decadal Oscillation, PDO, and the timing of the winter ice retreat) on zooplankton– planktivorous predator linkages in one of the most productive regions of the southeastern Bering Sea, the ‘Green Belt’. We examined changes in diets (species composition of chick meals and stable isotope signatures of adult blood) and relative food availability (as reflected in blood plasma concentrations of the stress hormone corticosterone) of planktivorous least auklets Aethia pusilla breeding on St. George I. (shelf-break) and St. Paul I. (shelf) during 2003 to 2005 and 2008 to 2009. We found that isotopic signatures of blood and composition of chick meals differed between the colonies. The proportion of energy-rich oceanic copepods Neocalanus spp. in the diet declined during warm years (high PDO and early ice retreat) on St. Paul but not on St. George. However, inter-annual and seasonal dynamics of corticosterone were similar between the colonies, and auklets experienced higher nutritional stress during warm compared to cold years. Our results suggest that the influx of prey-bearing water masses from the ocean basin and the retention time of oceanic copepods on the shelf are the main factors affecting composition of prey and its availability to auklets. We conclude that anticipated climate warming will negatively affect food availability of planktivorous predators in the Green Belt region of the southeastern Bering Sea.

Recent climate variability and its impacts on soybean yields in Southern Brazil

Recent climate variability in rainfall, temperatures (maximum and minimum), and the diurnal temperature range is studied with emphasis on its influence over soybean yields in southern Brazil, during 1969 to 2002. The results showed that the soybean (Glycine max L. Merril) yields are more affected by changes in temperature during summer, while changes in rainfall are more important during the beginning of plantation and at its peak of development. Furthermore, soybean yields in Parana are more sensitive to rainfall variations, while soybean yields in the Rio Grande do Sul are more sensitive to variations in temperature. Effects of interannual climatic variability on soybean yields are evaluated through three agro-meteorological models: additive Stewart, multiplicative Rao, and multiplicative Jensen. The Jensen model is able to reproduce the interannual behavior of soybean yield reasonably well.

Variability and trends in the directional wave climate of the Southern Hemisphere

AbstractThe effect of interannual climate variability and change on the historic, directional wave climate of the Southern Hemisphere is presented. Owing to a lack of in situ wave observations, wave climate in the Southern Hemisphere is determined from satellite altimetry and global ocean wave models. Altimeter data span the period 1985 to present, with the exception of a 2‐year gap in 1989–1991. Interannual variability and trends in the significant wave height are determined from the satellite altimeter record (1991 to present), and the dominant modes of variability are identified using an empirical orthogonal function (EOF) analysis. Significant wave heights in the Southern Ocean are observed to show a strong positive correlation with the Southern Annular Mode (SAM), particularly during Austral autumn and winter months. Correlation between altimeter derived significant wave heights and the Southern Oscillation Index is observed in the Pacific basin, which is consistent with several previous studies.Variability and trends of the directional wave climate are determined using the ERA‐40 Waves Re‐analysis for the period 1980–2001. Significant wave height, mean wave period and mean wave direction data are used to describe the climate of the wave energy flux vector. An EOF analysis of the wave energy flux vector is carried out to determine the dominant modes of variability of the directional seasonal wave energy flux climate. The dominant mode of variability during autumn and winter months is strongly correlated to the SAM. There is an anti‐clockwise rotation of wave direction with the southward intensification of the Southern Ocean storm belt associated with the SAM. Clockwise rotation of flux vectors is observed in the Western Pacific Ocean during El‐Nino events.Directional variability of the wave energy flux in the Western Pacific Ocean has previously been shown to be of importance to sand transport along the south‐eastern Australian margin, and the New Zealand region. The directional variability of the wave energy flux of the Southern Ocean associated with the SAM is expected to be of importance to the wave‐driven currents responsible for the transport of sand along coastal margins in the Southern Hemisphere, in particular those on the Southern and Western coastal margins of the Australian continent. Copyright © 2009 Royal Meteorological Society

Active‐layer characteristics and summer climatic indices, Mackenzie Valley, Northwest Territories, Canada

AbstractSummer thaw depths at eight monitoring sites in the Mackenzie Valley, determined from probing of grids and thaw tubes, are used to characterise the spatial and temporal variations in active‐layer thickness and to investigate linkages to climatic variations. Intra‐site variability in thaw depths is typically low where organic cover is thin and uniform. Higher variability occurs where moisture contents and organic cover are high and spatially variable.Grid‐mean thaw depths provide robust measures of the average site thaw depth, although they are less than annual maximum active‐layer thicknesses determined by thaw tubes. Values from both measurements correlate reasonably well, permitting estimates of the variations in active‐layer thickness from grid‐mean thaw depths.Active‐layer response to thermal forcing in various settings is well represented by grid‐mean thaw depths and the square‐root of late‐season thawing‐degree days. However, the effect of interannual climate variability on active‐layer thickness is better assessed by maximum tube thaw depths and the square‐root of total thawing‐degree days. Copyright © 2009 Her Majesty the Queen in right of Canada. Published by John Wiley & Sons, Ltd.

Evapotranspiration and water use efficiency in different-aged Pacific Northwest Douglas-fir stands

We used the eddy-covariance technique to measure evapotranspiration ( E) and gross primary production (GPP) in a chronosequence of three coastal Douglas-fir ( Pseudotsuga menziesii) stands (7, 19 and 58 years old in 2007, hereafter referred to as HDF00, HDF88 and DF49, respectively) since 1998. Here, we focus on the controls on canopy conductance ( g c), E, GPP and water use efficiency (WUE) and the effect of interannual climate variability at the intermediate-aged stand (DF49) and then analyze the effects of stand age following clearcut harvesting on these characteristics. Daytime dry-foliage Priestley–Taylor α and g c at DF49 were 0.4–0.8 and 2–6 mm s −1, respectively, and were linearly correlated ( R 2 = 0.65). Low values of α and g c at DF49 as well at the other two stands suggested stomatal limitation to transpiration. Monthly E, however, showed strong positive linear correlations to monthly net radiation ( R 2 = 0.94), air temperature ( R 2 = 0.77), and daytime vapour pressure deficit ( R 2 = 0.76). During July–September, monthly E (mm) was linearly correlated to monthly mean soil water content ( θ, m 3 m −3) in the 0–60 cm layer ( E = 453 θ − 21, R 2 = 0.69), and GPP was similarly affected. Annual E and GPP of DF49 for the period 1998–2007 varied from 370 to 430 mm and from 1950 to 2390 g C m −2, respectively. After clearcut harvesting, E dropped to about 70% of that for DF49 while ecosystem evapotranspiration was fully recovered when stand age was ∼12 years. This contrasted to GPP, which varied hyperbolically with stand age. Monthly GPP showed a strong positive linear relationship with E irrespective of the stand age. While annual WUE of HDF00 and HDF88 varied with age from 0.5 to 4.1 g C m −2 kg −1 and from 2.8 to 4.4 g C m −2 kg −1, respectively, it was quite conservative at ∼5.3 g C m −2 kg −1 for DF49. N-fertilization had little first-year response on E and WUE. This study not only provides important results for a more detailed validation of process-based models but also helps in predicting the influences of climate change and forest management on water vapour and CO 2 fluxes in Douglas-fir forests.

The effect of the El Niño Southern Oscillation on the reproductive frequency of eastern Pacific leatherback turtles

Summary Pacific leatherback turtle Dermochelys coriacea populations have been declining precipitously. It has been suggested that fishery‐associated mortality is the leading factor causing the decline; however, the sensitivity of leatherbacks to climate variability relative to their population ecology is unknown. We investigated the effects of interannual climate variability, as governed by the El Niño Southern Oscillation (ENSO), on leatherback nesting ecology. We used equatorial Pacific sea surface temperature (SST) anomaly data over various time scales derived from both moored buoys and remote satellites as signals of ENSO. We then incorporated these data into a remigration probability model for the largest nesting population of eastern Pacific leatherbacks at Parque Nacional Marino Las Baulas (PNMB), Costa Rica. Our results showed that nesting females of PNMB exhibited a strong sensitivity to ENSO, as reflected in their nesting remigration probabilities. Cool La Niña events corresponded with a higher remigration probability and warm El Niño events corresponded with a lower remigration probability. We suggest that productivity transitions at leatherback foraging areas in the eastern equatorial and south‐eastern Pacific in response to El Niño/La Niña events result in variable remigration intervals and thus variable annual egg production. This phenomenon may render the eastern Pacific leatherback population more vulnerable to anthropogenic mortality than other populations. Synthesis and applications. Physical indices of environmental variation can be used to estimate the probability of leatherbacks remigrating to nest at PNMB. This type of modelling approach can be extremely useful for understanding the effects of climatic variation on the population dynamics of sea turtles. Our remigration probability model can be applied to any monitored sea turtle nesting population where nesting site fidelity and beach monitoring coverage remains high. This modelling approach can help nesting beach monitoring programmes forecast remigrant numbers based on prior climate data, and can further quantify anthropogenic mortality by validating survival estimates.