Emergent freeze and fire disturbance dynamics in temperate rainforests

The coastal temperate rainforests of South and North America are part of the most biomass dense forest biome on the planet. They are also subject to rapid climatic shifts and, subsequently, new disturbance processes – snow loss‐driven mortality and the emergence of fire in historically non‐fire‐exposed areas. Here, we compare and contrast Southern and Northern Hemisphere coastal temperate rainforests of the Americas, two of the largest examples of the biome, via synthesis of current literature, future climate expectations and new downscaling of a global fire model. In terms of snow loss, a rapid decline in winter snow is leading to mass mortality of certain conifer species in the Northern Hemisphere rainforests. High‐elevation Southern Hemisphere forests, which are beginning to see similar declines in snow, may be vulnerable in the future, especially bogs and high‐water content soils. Southern Hemisphere forests are seeing the invasion of fire as an ecological force at mid‐to‐high latitudes, a shift not yet observed in the north but which may become more prominent with ongoing climate change. We suggest that research should focus on the flammability of seral vegetation and bogs under future climate scenarios in both regions. By comparing these two drivers of change across similar gradients in the Northern and Southern Hemispheres, this work points to the potential for emerging change in unexpected places in both regions. There is a clear benefit to conceptualising the coastal temperate rainforests of the Americas as two examples of the biome which can inform the other, as change is proceeding in similar directions but at different rates in each region.     

Thermal characteristics of running waters

This chapter reviews available data on thermal conditions prevailing in lotic ecosystems of the Southern Hemisphere. The primary factors (hydrology, climate, insolation) that interact to determine the thermal régime are examined in the context of southern waters. Maximum temperatures are plotted against annual ranges for equatorial (0–10° latitude), tropical (10–231/2° latitude), and temperate sites. In regions with seasonal climates, running waters exhibit diel and annual thermal periodicity patterns, the phasing of which varies between and within lotic systems. The universality of Illies' river zonation system is analyzed in the context of thermal conditions in Southern Hemisphere running waters.From the relatively limited data base, it appears that Southern Hemisphere running waters exhibit some distinctive features when viewedin toto, compared with Europe and North America where thermal characteristics of lotic habitats have been reasonably well documented. Such differences relate to the generally warm and dry conditions, and to the highly variable and unpredictable climatic régimes characterizing large areas of the Southern Hemisphere. It is concluded that differences in thermal conditions of running waters between hemispheres are a matter of degree rather than of kind, and partly reflect a small woodland stream bias inherent in Northern Hemisphere stream ecology.     

Middle Pliocene vegetation: reconstructions, paleoclimatic inferences, and boundary conditions for climate modeling

The general characteristics of global vegetation during the middle Pliocene warm period can be reconstructed from fossil pollen and plant megafossil data. The largest differences between Pliocene vegetation and that of today occurred at high latitudes in both hemispheres, where warming was pronounced relative to today. In the Northern Hemisphere coniferous forests lived in the modern tundra and polar desert regions, whereas in the Southern Hemisphere southern beech apparently grew in coastal areas of Antarctica.Pliocene middle latitude vegetation differed less, although moister-than-modern conditions supported forest and woodland growth in some regions now covered by steppe or grassland. Pliocene tropical vegetation reflects essentially modem conditions in some regions and slightly cooler-than-or warmer-than- modern climates in other areas. Changes in topography induced by tectonics may be responsible for many of the climatic changes since the Pliocene in both middle and lower latitudes. However, the overall latitudinal progression of climatic conditions on land parallels that seen in the reconstruction of middle Pliocene sea-surface temperatures.Pliocene paleovegetational data was employed to construct a 2 ° × 2 ° global grid of estimated mid-Pliocene vegetational cover for use as boundary conditions for numerical General Circulation Model simulations of middle Pliocene climates. Continental outlines and topography were first modified to represent the Pliocene landscape on the 2 ° × 2 ° grid. A modern 1 ° × 1 ° vegetation grid was simplified and mapped on this Pliocene grid, and then modified following general geographic trends evident in the Pliocene paleovegetation data set.     

Dwarf shrub and grass vegetation resistant to long‐term experimental warming while microarthropod abundance declines on the Falkland Islands

Dwarf shrubs are a dominant plant type across many regions of the Earth and have hence a large impact on carbon and nutrient cycling rates. Climate change impacts on dwarf shrubs have been extensively studied in the Northern Hemisphere, and there appears to be large variability in response between ecosystem types and regions. In the Southern Hemisphere, less data are available despite dwarf shrub vegetation being a dominant feature of southern South America and mountainous regions of the Southern Hemisphere. Here, we present the response of an Empetrum rubrum dwarf shrub and a Poa grass community to 12 years of experimental climate manipulation achieved using open top chambers on the Falkland Islands, a cold temperate island group in the South Atlantic. The dwarf shrub and grass vegetation did not change significantly in cover, biomass or species richness over the 12 years period in response to climate warming scenarios of up to 1°C reflecting annual warming levels predicted in this region for the coming decades. The soil microarthropod community, however, responded with declines in abundance (37%) under warming conditions in the grass community, but no such changes were observed in the dwarf shrub community. Overall, our data indicate that dwarf shrub communities are resistant to the levels of climate warming predicted over the coming decades in the southern South America region and will, therefore, remain a dominant driver of local ecosystem properties.     

Mammalian endemism,range size and conservation status in the southern temperate zone

Aim To examine the taxonomic uniqueness, range sizes, endemism and conservation status of southern temperate zone mammals and how factors impacting their conservation differ across hemispheres. Location Land surfaces of all continents (with the exception of Antarctica) and continental islands with an emphasis on the southern temperate hemisphere (land south of the Tropic of Capricorn). Methods We used data from the 2008 IUCN Red List of Threatened Species to characterize conservation status, threats and range sizes to compare northern and southern temperate zone mammals. We assessed the taxonomic uniqueness of the two regions as derived from the EDGE programme. We also conducted a gap analysis by overlapping mammal ranges with protected area coverages for temperate regions. Results Southern temperate species are phylogenetically more unique than in the Northern Hemisphere. The endemics have significantly smaller range sizes and are at a significantly greater risk of extinction (about 50% greater, with 24.7% of species being threatened versus 15.6% in the Northern Hemisphere). Finally, southern temperate endemics are significantly more likely to exist outside protected areas (13.38% versus 3.65%). Main conclusions The southern temperate zone harbours a unique fauna, attributed to the long isolation from the northern temperate zone. Temperate regions are heavily exploited for human activities, especially grazing and agriculture. The Southern Hemisphere is particularly susceptible to disturbance, given the small range sizes of its species and the low degree of protected area coverage. The scenario now is one of regions with numerous endemics under high threat from human activities.     

Global patterns of insect herbivory in gap and understorey environments,and their implications for woody plant carbon storage

Insect herbivory is thought to favour carbon allocation to storage in juveniles of shade‐tolerant trees. This argument assumes that insect herbivory in the understorey is sufficiently intense as to select for storage; however, understoreys might be less attractive to insect herbivores than canopy gaps, because of low resource availability and – at temperate latitudes – low temperatures. Although empirical studies show that shade‐tolerant species in tropical forests do allocate more photosynthate to storage than their light‐demanding associates, the same pattern has not been consistently observed in temperate forests. Does this reflect a latitudinal trend in the relative activity of insect herbivory in gap versus understorey environments? To date there has been no global review of the effect of light environment on insect herbivory in forests. We postulated that if temperature is the primary factor limiting insect herbivory, the effect of gaps on rates of insect herbivory should be more evident in temperate than in tropical forests; due to low growing season temperatures in the oceanic temperate forests of the Southern Hemisphere, the effect of gaps on insect herbivory rates should in turn be stronger there than in the more continental temperate climates of the Northern Hemisphere. We examined global patterns of insect herbivory in gaps versus understories through meta‐analysis of 87 conspecific comparisons of leaf damage in contrasting light environments. Overall, insect herbivory in gaps was significantly higher than in the understorey; insect herbivory was 50% higher in gaps than in understoreys of tropical forests but did not differ significantly between gaps and understories in temperate forests of either hemisphere. Results are consistent with the idea that low resource availability – and not temperature – limits insect herbivore activity in forest understoreys, especially in the tropics, and suggest the selective influence of insect herbivory on late‐successional tree species may have been over‐estimated.     

Differentiating drought legacy effects on vegetation growth over the temperate Northern Hemisphere

In view of future changes in climate, it is important to better understand how different plant functional groups (PFGs) respond to warmer and drier conditions, particularly in temperate regions where an increase in both the frequency and severity of drought is expected. The patterns and mechanisms of immediate and delayed impacts of extreme drought on vegetation growth remain poorly quantified. Using satellite measurements of vegetation greenness, in‐situ tree‐ring records, eddy‐covariance CO₂ and water flux measurements, and meta‐analyses of source water of plant use among PFGs, we show that drought legacy effects on vegetation growth differ markedly between forests, shrubs and grass across diverse bioclimatic conditions over the temperate Northern Hemisphere. Deep?rooted forests exhibit a drought legacy response with reduced growth during up to 4 years after an extreme drought, whereas shrubs and grass have drought legacy effects of approximately 2 years and 1 year, respectively. Statistical analyses partly attribute the differences in drought legacy effects among PFGs to plant eco‐hydrological properties (related to traits), including plant water use and hydraulic responses. These results can be used to improve the representation of drought response of different PFGs in land surface models, and assess their biogeochemical and biophysical feedbacks in response to a warmer and drier climate.     

Impact of fire and the recovery of molluscs in south‐east Australian salt marsh

Fire has long been recognised as a natural force in structuring Northern Hemisphere salt marshes, yet little is known about the impact of fire on molluscs and native vegetation dynamics of Southern Hemisphere coastal salt marshes. Following a fire at Ash Island, Hunter River New South Wales, Australia in the summer 2012, we assessed patterns of recovery through time of gastropod populations and resident salt marsh vegetation including biomass for three keystone native plant species, Native Rush (Juncus kraussii Hochst.), a chenopod (Sarcocornia quinqueflora Bunge ex Ungen‐Sternberg A.J. Scott), Salt Couch (Sporobolus virginicus, L. Kunth) and the invasive Spiny Rush (Juncus acutus). In temperate east‐coast Australian salt marshes, Spiny Rush is displacing native salt marsh vegetation. After twelve months, the biomass of Native Rush recovered to similar pre‐burn levels. While fire affected the abundance, richness and composition of the gastropod assemblage differences were also largely driven by spatial variability. Gastropod assemblages associated with two of the higher elevation native species (Native Rush and Salt Couch) were impacted the most by fire. Greater abundance (between 1 and 5 orders of magnitude difference in abundance) and richness of gastropods were found in unburnt compared with burnt Native Rush and Salt Couch vegetation, while more gastropods were found in Spiny Rush in one site. Species prevalent in burnt vegetation included larger species of gastropods Ophicardelus ornatus (Ferussac, 1821) and Phallomedusa solida (Martens, 1878) with an unexpected spike in number of the smaller gastropod Tatea huonensis (Tenison‐Woods, 1876) in the spiny rush at one site only. In salt marsh habitats, many gastropods have planktonic larval dispersal stages which are dependent on the tidal height for transport and the structural complexity provided by vegetation at settlement. Since fire appears to negatively affect salt marsh gastropod populations within structurally complex Native Rush and Salt Couch, due consideration of the importance of these refuges for gastropods is recommended when fire or other disturbances occur in ecologically endangered salt marsh in the Southern Hemisphere. Managers need to consider spatial heterogeneity of molluscs and their recovery in the event of fire in Southern Hemisphere salt marshes.     

Role of plant functional traits in determining vegetation composition of abandoned grazing land in north‐eastern Victoria,Australia

Question: In the Northern Hemisphere, species with dispersal limitations are typically absent from secondary forests. In Australia, little is known about dispersal mechanisms and other traits that drive species composition within post‐agricultural, secondary forest. We asked whether mode of seed dispersal, nutrient uptake strategy, fire response, and life form in extant vegetation differ according to land‐use history. We also asked whether functional traits of Australian species that confer tolerance to grazing and re‐colonisation potential differ from those in the Northern Hemisphere. Location: Delatite Peninsula, NE Victoria, Australia. Methods: The vegetation of primary and secondary forests was surveyed using a paired‐plot design. Eight traits were measured for all species recorded. ANOSIM tests and Non‐metric Multi‐dimensional Scaling were used to test differences in the abundance of plant attributes between land‐use types. Results: Land‐use history had a significant effect on vegetation composition. Specific leaf area (SLA) proved to be the best predictor of response to land‐use change. Primary forest species were typically myrmecochorous phanerophytes with low SLA. In the secondary forest, species were typically therophytes with epizoochorous dispersal and high SLA. Conclusions: The attributes of species in secondary forests provide tolerance to grazing suggesting that disturbance caused by past grazing activity determined the composition of these forests. Myrmecochores were rare in secondary forests, suggesting that species had failed to re‐colonise due to dispersal limitations. Functional traits that resulted in species loss through disturbance and prevented re‐colonisation were different to those in the Northern Hemisphere and were attributable to the sclerophyllous nature of the primary forest.     

Quantifying massive outbreaks of the defoliator moth Ormiscodes amphimone in deciduous Nothofagus‐dominated southern forests using remote sensing time series analysis

Forest insect outbreaks are one of the major biotic disturbances on natural and artificial landscapes. Although abundant literature of insect outbreaks exists in the Northern Hemisphere, studies for the Southern Hemisphere are rare. Recently, massive outbreaks of the native moth Ormiscodes amphimone (Fabricius) (Lepidoptera: Hemileucinae) have been reported in the southern cone of South America. These O. amphimone outbreaks have defoliated large areas of temperate forests, raising great concern among local inhabitants, but yet the spatio‐temporal patterns of these events have not been evaluated. Here, we quantify the extension of the massive O. amphimone outbreaks occurred in the Aysén region (southern Chile) in the period 2000–2015 using a novel remote sensing approach and field data. Remote sensing detections were strongly in agreement with field observations and showed that massive outbreaks of O. amphimone are among the largest biotic disturbances in the forests of the Southern Hemisphere. Considering only field‐confirmed outbreaks, the defoliated area reached 164,000 hectares in total between 2000 and 2015. The estimation of the spatial impact of O. amphimone, and its recurrence, represents the first step for the search of management alternatives of this massive disturbance.     

Diversity and ecological distribution of macrofungi in the Laojun Mountain region,southwestern China

Surveys of the macrofungi associated with eight different vegetation types in the Laojun Mountain region of southwestern China yielded approximately 520 species belonging to 175 genera. Species richness and diversity were highest in mixed conifer and broadleaf forests and deciduous broadleaf forests. In typical forests of temperate regions of the world, there are five dominant genera of ectomycorrhizal macrofungi. The distribution patterns of species in these genera for the different vegetation types indicate that they are able to associate with a wide variety of different trees. Analysis of data for common macrofungal species and taxonomic similarity of the communities present in the eight vegetation types suggest that the greater the differences in the plant species that comprise the vegetation, the less similar are the common macrofungal species associated with the most common host plants. These same data also show that some species of macrofungi occur only in one or two vegetation types. There were 156 species of edible fungi recorded from the different vegetation types, and these fungi appear to be abundant in the Laojun Mountain region. At different positions along the elevation gradient, positive correlations existed with respect to the relationship between species richness and diversity, and the general trend was for macrofungal species richness and diversity to decrease with increasing elevation, with the numbers of species recorded being significantly lower at the very highest elevation. The relative dominance of certain taxa in the assemblage of species present was found to increase with increasing elevation, and variation in the evenness component of diversity was slight. As such, the differences in dominance and evenness were also not significant (P > 0.05). Macrofungal species richness was slightly more diverse on shaded slopes than on more exposed (sunny) slopes, and the differences in species diversity, dominance and evenness were relatively minor. This suggests that slope aspect may only weakly influence the distribution of macrofungal species in the Laojun Mountain region.     

Plate tectonics and the distribution of cool temperate Southern Hemisphere macrolichens

GALLOWAY, D. J., 1988. Plate tectonics and the distribution of cool temperate Southern Hemisphere macrolichens. Several macrolichen genera in the families Lobariaceae and Pannariaceae speciate richly in cool temperate areas of the Southern Hemisphere between latitudes 35 and 55°S, being common in Nothofagus forests, subalpine shrubland, bog and grassland habitats. Affinities of southern cool temperate lichens are discussed in terms of plate tectonics and tectono-stratigraphic terranes.     

Tooth row counts, vicariance, and the distribution of the sand tiger shark Carcharias taurus

Geographic variation in tooth row counts among sand tiger sharks Carcharias taurus (Chondrichthyes), from the SW Atlantic, NW Atlantic and the East China Sea is analyzed in this paper. We found significant differences between sand tigers from the SW Atlantic (Southern Hemisphere population) and each of the other two (Northern Hemisphere) regions in the number of upper lateral tooth rows, and between individuals from the SW Atlantic and the East China Sea in the total number of upper tooth rows. Sand tiger sharks from the two Northern Hemisphere populations did not differ in any of the studied variables. Our results agree with comparisons of vertebral counts between sand tiger sharks from Southern and Northern Hemispheres. Both lines of evidence suggest that Southern and Northern Hemisphere populations of C. taurus were isolated to a larger extent than populations of the Northern Hemisphere. The fossil record of the genus Carcharias begins in the Early Cretaceous and C. taurus is certainly known since the Late Miocene. During the Miocene, the Tethys Sea separating northern and southern land masses was still present and it provided a continuous temperate shallow sea that could allow dispersal of sand tiger sharks along Northern Hemisphere seas. Independent observations on the distribution and evolutionary history of the genera Myripristis , Neoniphon , Sargocentron and Aphanius , and genetic studies on the temperate shark genus Mustelus that indicate a close relationship between the Indo-Pacific M. manazo and the Mediterranean M. asterias suggest that this hypothesis is plausible and deserves to be tested.     

Phylogeny and biogeography of Caltha (Ranunculaceae) based on chloroplast and nuclear DNA sequences

The genus Caltha (Ranunculaceae) consists of 10 species of low-growing, perennial herbs distributed throughout the moist temperate and cold regions of both the Northern and Southern Hemispheres. Traditionally, the species have been divided into two sections: section Psychrophila in the Southern Hemisphere with diplophyllous leaves and section Caltha in the Northern Hemisphere with leaves lacking inflexed appendages. This study uses chloroplast and nuclear DNA sequences to determine the relationships among the 10 species, test the monophyly of sections Psychrophila and Caltha, trace the evolutionary history of diplophylly, and explore biogeographical hypotheses for the genus. Analysis of these data resulted in a well-resolved and well-supported phylogeny. Section Psychrophila (C. sagittata, C. appendiculata, C. dionaeifolia, C. obtusa, C. introloba, and C. novae-zelandiae) was resolved as monophyletic, indicating a single origin of diplophylly. The species of section Caltha (C. natans, C. scaposa, C. palustris, and C. leptosepala) formed a paraphyletic grade. The resulting phylogeny strongly supports a Northern Hemisphere origin for Caltha, followed by dispersal to the Southern Hemisphere (Gondwanaland). A vicariance model is invoked to explain present-day distributions in South America, Australia, and New Zealand.     

The world's southernmost tree and the climate and windscapes of the southernmost forests

The world's southernmost tree has been documented along with the condition and growth pattern of the world's southernmost forest on Isla Hornos, Chile. The distribution of trees at broad scales is strongly influenced by the abiotic environment and determining the position and condition of tree limits around the world is an important way to monitor global change. This offers an ideal way to test the relationship between the biogeography of individual species and the effects of climate/climate change. The limits of trees, as all ecotones, are also useful communication points – easily understood signposts of ecosystems and their change through time. The southernmost trees in the world exist at soil temperatures that correspond to the low range of global treeline temperatures, with a climate analogous to equatorial treeline despite the high latitude (56° S). However, their fine‐scale distribution is strongly influenced by wind exposure rather than simply aspect and/or elevation, as one would expect if temperature were limiting the range. Recent establishment further south was found from core forest areas, however significant dieback along wind‐exposed edges of the contiguous forest was also noted. In contrast to the wide extension of land where boreal or subarctic forests grow in the Northern Hemisphere, in the Southern Hemisphere Isla Hornos represents a single point embedded in the ocean under much milder climatic conditions. Documented shifts in wind intensity and direction as result of larger‐scale climate change will likely continue to strongly shape the condition of these unique forests.     

Molecular evidence for long distance dispersal across the Southern Hemisphere in the Ganoderma applanatum-australe species complex (Basidiomycota)

We examined phylogeographic relationships in the cosmopolitan polypore fungus Ganoderma applanatum and allies, and conservatively infer a possible age of origin for these fungi. Results indicate that it is very unlikely that members of this species complex diversified before the break-up of Gondwana from Laurasia ca 120 M years ago, and also before the final separation of the Gondwanan landmasses from each other that was achieved about 66 M years ago. An earliest possible age of origin of 30 M years was estimated from nucleotide substitution rates in the 18S rDNA gene. Phylogenetic reconstruction of a worldwide sampling of ITS rDNA sequences reveals at least eight distinct clades that are strongly correlated with the geographic origin of the strains, and also correspond to mating groups. These include one Southern Hemisphere clade, one Southern Hemisphere–Eastern Asia clade, two temperate Northern Hemisphere clades, three Asian clades, and one neotropical clade. Geographically distant collections from the Southern Hemisphere shared identical ITS haplotypes, and an ITS recombinant was noted. Nested clade analysis of a parsimony network among isolates of the Southern Hemisphere clade indicated restricted gene flow with isolation-by-distance among the New Zealand, Australia–Tasmania, Chile–Argentine, and South Africa populations, suggesting episodic events of long-distance dispersal within the Southern Hemisphere. This study indicates that dispersal bias plays a more important role than generally admitted to explain the Southern Hemisphere distribution of many taxa, at least for saprobic fungi.     

The genetic legacy of aridification: climate cycling fostered lizard diversification in Australian montane refugia and left low-lying deserts genetically depauperate

It is a widely held assumption that populations historically restricted to mountain refugia tend to exhibit high levels of genetic diversity and deep coalescent histories, whereas populations distributed in surrounding low-lying regions tend to be genetically depauperate following recent expansion from refugia. These predicted genetic patterns are based largely on our understanding of glaciation history in Northern Hemisphere systems, yet remain poorly tested in analogous Southern Hemisphere arid systems because few examples in the literature allow the comparison of widespread taxa distributed across mountain and desert biomes. We demonstrate with multiple datasets from Australian geckos that topographically complex mountain regions harbor high nucleotide diversity, up to 18 times higher than that of the surrounding desert lowlands. We further demonstrate that taxa in topographically complex areas have older coalescent histories than those in the geologically younger deserts, and that both ancient and more recent aridification events have contributed to these patterns. Our results show that, despite differences in the details of climate and landscape changes that occurred in the Northern and Southern hemispheres (ice-sheets versus aridification), similar patterns emerge that illustrate the profound influence of the Pleistocene on contemporary genetic structure.     

Extended gestation with late‐autumn births in a cool‐climate viviparous gecko from southern New Zealand (Reptilia: Naultinus gemmeus)

Abstract Female viviparous lizards from temperate locations in the Southern Hemisphere (New Zealand, Tasmania (Australia), South Africa and South America) often have reproductive activity spanning many months of the year. In contrast, vitellogenesis and pregnancy are often confined to the spring/summer months in viviparous species from temperate zones of the Northern Hemisphere. An extreme Southern Hemisphere example is the nocturnal common gecko from New Zealand, Hoplodactylus maculatus (Gray 1845), in which females exhibit biennial reproduction with pregnancy lasting up to 14 months in a cool‐climate population. Here, we examined whether such an extended reproductive cycle also occurs in a diurnal species, the jewelled gecko Naultinus gemmeus (McCann 1955), at a similar latitude. Palpation was used to assess reproductive condition non‐invasively. In contrast to the nearby higher‐altitude population of H. maculatus, N. gemmeus reproduces annually. Vitellogenesis occurs from autumn to spring in both species, but pregnancy ends after about 7 months in N. gemmeus. Birth occurs in the seemingly unpropitious season of mid‐ to late autumn, a pattern that may be unique for lizards from cool‐temperate zones. We hypothesize that there are major differences between populations of N. gemmeus and H. maculatus with respect to survival of autumn‐born neonates and/or costs to females from remaining pregnant over winter. Museum specimens of N. gemmeus support anatomical inferences from palpation; they also suggest that vitellogenesis may begin before the end of pregnancy (which may be essential to completing each reproductive cycle within a year) and that some populations may show gestation in utero over winter, as in H. maculatus. Extended gestation appears to be a common response to cool climates for Southern Hemisphere lizards that have independently evolved viviparity.     

Seasonally different response of photosynthetic activity to daytime and night‐time warming in the Northern Hemisphere

Over the last century the Northern Hemisphere has experienced rapid climate warming, but this warming has not been evenly distributed seasonally, as well as diurnally. The implications of such seasonal and diurnal heterogeneous warming on regional and global vegetation photosynthetic activity, however, are still poorly understood. Here, we investigated for different seasons how photosynthetic activity of vegetation correlates with changes in seasonal daytime and night‐time temperature across the Northern Hemisphere (>30°N), using Normalized Difference Vegetation Index (NDVI) data from 1982 to 2011 obtained from the Advanced Very High Resolution Radiometer (AVHRR). Our analysis revealed some striking seasonal differences in the response of NDVI to changes in day‐ vs. night‐time temperatures. For instance, while higher daytime temperature (T_max) is generally associated with higher NDVI values across the boreal zone, the area exhibiting a statistically significant positive correlation between T_max and NDVI is much larger in spring (41% of area in boreal zone – total area 12.6 × 10⁶ km²) than in summer and autumn (14% and 9%, respectively). In contrast to the predominantly positive response of boreal ecosystems to changes in T_max, increases in T_max tended to negatively influence vegetation growth in temperate dry regions, particularly during summer. Changes in night‐time temperature (T_min) correlated negatively with autumnal NDVI in most of the Northern Hemisphere, but had a positive effect on spring and summer NDVI in most temperate regions (e.g., Central North America and Central Asia). Such divergent covariance between the photosynthetic activity of Northern Hemispheric vegetation and day‐ and night‐time temperature changes among different seasons and climate zones suggests a changing dominance of ecophysiological processes across time and space. Understanding the seasonally different responses of vegetation photosynthetic activity to diurnal temperature changes, which have not been captured by current land surface models, is important for improving the performance of next generation regional and global coupled vegetation‐climate models.