What determines the spatial extent of landscape effects on species?

Context

Landscape ecologists are often interested in measuring the effects of an environmental variable on a biological response; however, the strength and direction of effect depend on the size of the area within which the environmental variable is measured. Thus a central objective is to identify the optimal spatial extent within which to measure the environmental variable, i.e. the “scale of effect”.

Objectives

Our objectives are (1) to provide a comprehensive summary of the hypotheses concerning what determines the scale of effect, (2) to provide predictions that can be tested in empirical studies, and (3) to show, with a review of the literature, that most of these predictions have so far been inadequately tested.

Methods

We propose 14 predictions derived from five hypotheses explaining what determines the scale of effect, and review the literature (if any) supporting each prediction. These predictions involve five types of factors: (A) species traits, (B) landscape variables, (C) biological responses (e.g. abundance vs. occurrence), (D) indirect influences, and (E) regional context of the study. We identify methodological issues that hinder estimation of the scale of effect.

Results

Of the 14 predictions, only nine have been tested empirically and only five have received some empirical support. Most support is from simulation studies. Empirical evidence usually does not support predictions.

Conclusions

The study of the spatial scale at which landscape variables influence biological outcomes is in its infancy. We provide directions for future research by clarifying predictions concerning the determinants of the scale of effect.

     

Abundance–occupancy and abundance–body mass relationships of small mammals in a mountainous landscape

Context

Mountainous landscapes are characterized by strong spatial heterogeneity, leading to increasing geographical isolation and decreasing area with elevation. Consequently, the colonization rate decreases from the low to high elevation zone, while the extinction rate shows the opposite.

Objectives

Due to such changes, we test whether (1) species occur at a declining number of sites (mountains) and have a less positive abundance–occupancy relationship (AOR) in a higher elevation zone; (2) a lower proportion of rare large-bodied species (less resistant to extinction) and a more positive abundance–body mass relationship (ABR) emerge in a higher elevation zone.

Methods

Using the data of small mammals from 20 elevational gradients in the Mountainous Region of Southwest China, we compared the AORs and ABRs among the low, middle and high elevation zones. The AOR and ABR were fitted with linear and polynomial regression models. We compared endemic ratios among the different elevation zones.

Results

The AOR was best characterized by a linear model and positive in all elevation zones. Its slope decreased from the low to high elevation zone. The quadratic model performed the best in fitting the ABR in each zone. When fitted with linear models, both the R² and slope of the ABR increased towards the high elevation zone. The endemic ratios were significantly higher in the middle and high elevation zones.

Conclusions

Both the AOR and ABR in mountainous landscapes are strongly elevation-dependent. The increasing geographical isolation and decreasing area with elevation can have a high impact on macroecological patterns and processes.

     

Effects of different rootstocks and training systems on the mineral composition of ‘Delicious’ apple leaves

Leaf mineral composition as affected by different rootstocks, cultivars, training systems and their combinations was measured during 1987 and 1988. Trees on M.7 had significantly higher concentrations of N, P and Fe, whereas those on MM. 106 maintained higher values of K, Ca, Mg and Mn during both years. Between cultivars, Red ‘Delicious’ showed greater accumulation of N, P, Mg and Fe but K and Cu levels were found to be more in Starking ‘Delicious’. All mineral nutrients except Ca and Mg accumulated more in spindle-bush trained trees than those under modified central leader system. The Mineral composition of Starking ‘Delicious’ grafted on M.7 rootstock and trained as a spindle bush produced the best yield efficiency and fruit quality, and fell within the normal range.     

Effects of light on flavonoid and chlorogenic acid levels in the skin of ‘Jonagold’ apples

The objective of our work was to determine how fruit position on the tree affects flavonoid and chlorogenic acid contents. Light was measured at different positions within the canopy of 10-year-old ‘Jonagold’ apple trees on M.9 rootstock raised as slender spindles. Fruit from the top of the canopy contained the highest percentage of blush and the highest levels of cyanidin 3-galactoside (anthocyanin) and quercetin 3-glycosides, followed by fruit from the outside of the canopy, and then those from the canopy interior. There were no significant differences in the levels of catechins, phloridzin and chlorogenic acid among fruit from the different canopy positions. Light level was directly correlated with the levels of cyanidin 3-galactoside and quercetin 3-glycosides and with the percentage of blush in the fruit skin. Light in the interior of the canopy was poorer in UV-A, blue, green and red but richer in far-red light than at all other positions. Consequently, the FR/R ratio was much larger at the interior of the canopy than at all other positions. Both anthocyanin and quercetin 3-glycoside concentrations were clearly related to light level, and there was a critical FR/R ratio of about 1 below which no anthocyanin and only minimal quercetin 3-glycosides were formed.     

Quantifying the spatial relationship between bird species’ distributions and landscape feature boundaries in southern Ontario, Canada

Understanding what features of the landscape affect species distribution is critical to effectively implement conservation strategies. This study investigates how a boundary analysis framework can be used to characterize the spatial association between boundaries (i.e., spatial locations of high rates of change) in bird species?? distributions and landscape features at the regional scale. The study area covers 92,000?km² in southern Ontario (Canada) and extends from the Great Lakes-St. Lawrence biome to the southern Canadian Shield biome. Landcover composition was derived from Ontario Land Cover data (1991?C1998; 7 types) and elevation data were derived from the Canada3D digital elevation model. Bird distributions were estimated using indicator kriging based on point counts obtained from the Ontario Breeding Bird Atlas data (2001?C2005; 60 species). Boundaries were delineated for both data types using a 10?×?10?km cell resolution. Spatial boundary overlap statistics were used to quantify the spatial relationship between landscape features and bird boundaries and tested using a randomization procedure. There was significant positive association and spatial overlap between delineated landscape feature boundaries and bird boundaries. The number of spatially overlapping cells between the two boundary types was 67 out of 164 (41?%) and 76?% of cells were within 11.42?km of each other. These results were statistically significant (P?<?0.001) and suggest a strong spatial relationship between high rates of change in landscape features and bird species?? distributions at the regional scale. A boundary analysis framework could be used to identify boundary shifts in response to climate change and anticipate changes in species distributions.     

Effects of green roofs’ variations on the regional thermal environment using measurements and simulations in Chongqing,China

In the present work, field measurement and simulation method were employed to investigate the effects of several green roofs variables on regional thermal environment in Chongqing (29°N, 106°E), China. Field experiments were conducted in two typical places. The real influence of green roofs on ambient environment was analyzed and compared with the simulation results. The software ENVI-met was employed to simulate 29 cases with different factors, including green roofs types, vegetation coverage, building height, arrangement position and regional layouts. With the aim to investigate the effect of the green roofs thoroughly, different design factors of green roofs were taken in consideration. From the aspect of cooling effect, it can be found that enclosing layout has the maximum air temperature drop, which is up to 0.5 °C. From the perspective of the uniformity of regional environmental temperature distribution, the regional thermal environment of scattered layout is better than enclosing and array layout as a whole. In addition, with the same vegetation coverage, the effectiveness of air temperature dropping of the whole region differed according to the arrangement position. Centrally arranging the green roofs upwind can effectively reduce the air temperature of the whole region. These findings can be used to improve the regional thermal environment by designing the green roofs reasonably.     

Fruit-Thinning Effects on the Development and Storage Quality of Cox’s Orange Pippin Apple Fruits

Fruit-thinning treatments were applied in the three seasons 1963–65 to Cox trees to investigate the relationships between leaf : fruit ratio, fruit size, cell volume and cell number, and the incidence of rotting and disorders following air storage at 2·8° C. (37° F.) and o° C. (32° F.). Progressively more severe thinning was required, sis fruit development proceeded, to obtain a similar increase in fruit size. This declining response to thinning was accompanied by a progressively smaller increase in the cell numbers of fruits as the treatments were delayed. Thinning also caused an increase in cell-enlargement rate but the magnitude of the response varied between different experiments and did not appear to be related to the developmental stage at which the treatment was applied.

The larger fruits from thinned trees were more susceptible to bitter pit, breakdown, and rotting caused by Gloeosporium perennans, but were less susceptible to low-temperature injury than fruits from unthinned trees. Bitter-pit incidence was related to fruit size within each treatment and was more severe in fruit where the ratio between the potassium and calcium concentrations was high. Low-temperature injury was associated with fruit with low dry matter and potassium contents. Susceptibility to this disorder and to rotting was also influenced by fruit maturity as measured by the progress of the climacteric rise in respiration rate. There were no marked relationships between storage disorders and the numbers or size of cells in fruits produced by the various treatments included in these experiments.     

Effects of growth regulators and activated charcoal on in vitro bulblet multiplication and growth in Galanthus nivalis ‘Flore Pleno’

Summary

The in vitro multiplication of Galanthus nivalis ‘Flore Pleno’ bulblet clumps was evaluated through three 16-week sub-culture passages on media supplemented with either 1.0 mg l^–1 6-benzylaminopurine (BA) and 0.1 mg l^–1 naphthaleneacetic acid [NAA; the plant growth regulator (PGR) control], 0.5 mg l^–1 BA and 0.05 mg l^–1 NAA (PGR/2), or 0.1 mg l^–1 BA and 0.01 mg l^–1 NAA (PGR/10). At the end of the second sub-culture passage, clumps of bulblets from each of the three PGR treatments were also transferred to conditions to promote bulblet growth (G medium without PGRs) supplemented with 60 g l^–1 sucrose and 5 g l^–1 activated charcoal (AC). Lowering the PGR concentration during the initial multiplication phase reduced bulblet multiplication and overall culture growth, but did not influence bulblet size, as indicated by the diameter of the largest bulblet. Lowering the PGR concentration during the multiplication phase also reduced the multiplication of bulblets, overall tissue fresh weight, and the production of roots in tissues transferred to bulblet growth conditions. The reduced growth of tissues previously multiplied on PGR/10 medium was not, however, reflected in the growth of individual bulblets, since these were not significantly smaller than bulblets initially multiplied at the higher PGR concentrations. Bulblet sprouting and root growth on the bulblet growth medium were unaffected by prior PGR status in the multiplication phase. The results are discussed in terms of the mode of action of AC on the promotion of bulblet growth.     

The Effects of Fruit Thinning on the Development of Cox’s Orange Pippin Apples in Relation to the Incidence of Storage Disorders

Severe hand thinning of fruitlets on Cox’s Orange Pippin trees five weeks after full blossom led to a doubling of fruit weight by harvest. Although the rate of cell division was stimulated slightly, the larger fruit size was due mainly to an increased rate of cell enlargement.

The respiration rate of whole fruits was slightly higher after thinning and the onset of the climacteric rise was advanced. Respiration per cell was correspondingly higher in the larger cells of the thinned fruit and respiration per unit protein was similar to that of fruit from unthinned trees.

Potassium, magnesium, and phosphorus contents, expressed on a fresh weight basis, were higher in the cortical tissue of the thinned fruits. Calcium per unit fresh weight was unaffected by thinning and the ratio of calcium to cell surface remained relatively constant throughout development in both types of fruit.

Senescent breakdown and bitter pit developed during storage only in the thinned fruit. Slight differences in the incidence of rotting and low temperature breakdown between the two types of fruit are attributed to the effects of maturity rather than of fruit size.     

Effects of rate of establishment of storage conditions and ethylene removal on the storage performance of ‘Cox's Orange Pippin’ apples

The use of rapid establishment of temperature and CA storage conditions, as well as ethylene removal to reduce loss of firmness and ground colour, during storage of apples (Malus domestica Borkh, ‘Cox's Orange Pippin’) in <1% CO₂ + 1.25% O₂ at 3.5°C was investigated. Samples subjected to rapid establishment (RE) of storage conditions had a higher peel chlorophyll content after 5 months storage, but not after 8 months, than samples from containers where the conditions had been established at a rate typical of normal, well-maintained commercial stores (CR). RE samples were considered firmer than CR by a sensory panel in February but not in May, while penetrometer readings were the same on both occasions. RE samples which had additionally been subjected to a pre-harvest daminozide spray and ethylene removal during storage (LE) were firmer, had a higher peel chlorophyll content and, on the green parts of the surface, a lower Hunter “b” value in February than both CR and RE samples. The effects of LE on chlorophyll and ground colour were maintained until May, but in both February and May only the ground colour effect was maintained during a simulated marketing period of 14 days at 10°C in air following storage.     

Effects of Fruit Thinning Severity on Yield and Quality in ‘Sensation’ Mango （Mangifera indica）

Four different fruit thinning severities were tested.The thinning treatments were carried out in October before the occurrence of physiological fruit drop.Different parameters were measured(both qualitative and quantitative) and the results compared among treatments as well as to that of the control.The results showed that wher fruit on ‘Sensation’ mango pani-cles were thinned to two fruit per panicle,a significant difference was obtained for most of the quantitative parameters.The fruits of the treatment where one fruit per panicle was retained and 50% panicles removed,produced the best results for most of the qualitative parameters.     

Where do we go from here? Dispersal simulations shed light on the role of landscape structure in determining animal redistribution after reintroduction

Reintroduction projects represent viable options for animal conservation. They allow the establishment of new local populations and may contribute to recreating functional networks within a metapopulation. In the latter case, landscape connectivity may be a major determinant of the phase of spread of the reintroduced populations. Here, we deal with an example of a red deer (Cervus elaphus) translocation planned to enable the connection among existing isolated populations of the species in the Italian Alps. Our aim was to assess whether the analysis of landscape suitability and the simulation of dispersal of released individuals could shed light on the actual process of population spread. For these purposes, we adopted a modelling approach using radiotracking data to develop a habitat suitability map. On the basis of this map, we simulated the dispersal of the animals after release and we then compared the simulation results with the outcome of null models and with the observed population redistribution. The results suggest that the spread of the subpopulation was easier north-westward than southward. Taking into account landscape suitability, our simulations produced a reliable estimate of the ease of colonization of the valleys neighbouring the release-site and they allowed the identification and validation of a potential pathway for animal dispersal. The suitability model based on the monitoring of individuals in the earliest phase of establishment shed light on the spread of the population and on its potential connections with other deer subpopulations.     

Effects of the application of ‘cash’ on the growth,fruit yield,and nutrient status of tomato (Solanum lycopersicum L.) grown in reclaimed saline soil

Summary

The effects of ‘cash’ [a novel 2:5:1 (w/w/w) mixture of calcium sulphate, ground sunflower heads, and humic acid] as a soil amendment on the growth, fruit yield, and leaf nutrient status of tomato (Solanum lycopersicum L.) grown on reclaimed saline soil (EC = 9.4 dS m^–1) were investigated. A glasshouse experiment was performed in a completely randomised design with six treatments (0, 10, 20, 30, 40, or 50 g ‘cash’ kg^–1 soil) each with four replicates. The results indicated that ‘cash’ increased both the shoot dry weight (DW) plant^–1 and the root DW plant^–1, the free proline contents of leaves, and leaf chlorophyll contents. The use of ‘cash’ also increased the number of fruit plant^–1, fruit yield pot^–1, and fruit vitamin C contents, although total soluble solids (TSS) contents were not affected. The contents of nitrogen (N), potassium (K), and calcium (Ca), and the Ca:Na ratios of leaf tissues increased with all application rates of ‘cash’. Leaf phosphorus (P) contents showed no response to any applied level of ‘cash’. Leaf sodium (Na) contents declined gradually with an increase in the level of ‘cash’ applied to the soil. We concluded that ‘cash’ has a pronounced positive effect on the growth and fruit yield of tomato plants grown in reclaimed saline soil. ‘Cash’ therefore has the potential to be used as a soil amendment for vegetable crops such as tomato to overcome the adverse effects of salinity in newly-reclaimed soils.     

Effects of genotype and environment on total anti-oxidant capacity and the content of sugars and acids in strawberries (Fragaria × ananassa Duch.)

Summary

Total anti-oxidant capacity (TAC) and the contents of mono- and disaccharides, and organic acids were determined in strawberry fruit from ten genotypes sampled from eight experimental sites in Norway in 2002 and 2003. The difference between genotypes was significant for all recorded traits, and it appeared possible to select for all traits in breeding programmes. On average, the Norwegian bred cultivar ‘Carmen’ had a TAC of 30.07 mmol kg^–1 fresh weight (FW), compared to 23.16 mmol kg^–1 FW in the standard cultivar ‘Korona’. TAC was negatively correlated with fruit size, rainfall and leaf surface humidity, but was positively correlated with the minimum temperature on the day prior to sampling. Mono- and di-saccharide contents were negatively correlated with both minimum and maximum temperatures, and with wind velocity. It was confirmed that the sugars:organic acids ratio was inversely related to the maximum temperature on the day before harvest, which supports anecdotal claims that strawberries grown in northern areas have, on average, better flavour.     

Effects of crop load and time of thinning on the incidence of split pits,fruit yield,fruit quality,and leaf mineral contents in ‘Andross’ peach

Summary

The effects of light, moderate, or heavy thinning (5, 10, or 20 cm between fruit, respectively), conducted before (7 d or 15 d), during, or after (7 d or 15 d) pit hardening (PH), on the incidence of split pits, fruit yield, fruit quality characteristics, and leaf mineral contents, were studied in the canning peach (Prunus persica L. Batsch.) cultivar ‘Andross’ over two growing seasons. The percentage of fruit with split pits increased by 58.2% in heavily-thinned trees compared with moderately- or lightly-thinned trees, and by 22.9% for the earliest time of thinning (15 d before PH) compared with thinning during, or after PH. Fruit fresh weight (FW) was greater in moderately- and heavily-thinned trees compared with lightly-thinned trees, but yields were similar among the different crop-load treatments. The latest time of thinning (15 d after PH) also had a negative impact on yield at first harvest and on total yield, fruit FW, and delayed fruit ripening compared to thinning during, and 15 d before PH. Total anti-oxidant capacities and phenolic contents were usually greater in fruit from heavily-thinned compared with lightly- or moderately-thinned trees only when thinning was conducted during, or 15 d after PH. Moreover, anti-oxidant levels were highest in fruit from the earliest-thinned trees. There was no significant effect of crop load, or of time of thinning application treatment on fruit colour, or on the K, P, Fe, Mn, and Cu contents of leaf tissues. In conclusion, light or moderate thinning during PH resulted in minimal split pits during processing, and in optimal yields and fruit quality characteristics in the canning peach cultivar ‘Andross’.     

Effects of panax notoginseng saponins on content of triglyceride and the mRNA expression of LXRα in steatotic hepatocyte L02

AIM: To study the effects of panax notoginseng saponins (PNS) on the content of triglyceride (TG) and the mRNA expression of liver X receptor α (LXRα) in steatotic hepatocyte L02.METHODS: The cells of hepatocyte L02 were cultured with 50% bovine calf serum for 48 h and a model of steatosis of hepatocytes was established. The appropriate concentrations of PNS on steatotic hepatocytes were detected by MTT assay. The cells were divided into 5 groups: normal control group, model group, spontaneous recovery group, low concentration of PNS group (10 mg/L) and high concentration of PNS group (50 mg/L). Meanwhile, hepatocytes in model group were continuously cultured by RPMI-1640 medium containing 50% bovine calf serum while others were cultured by RPMI-1640 medium containing 10% bovine calf serum. After 24 h, the lipid droplets in the cells stained with oil red O were observed under microscope, the intracellular TG levels were determined by automatic biochemical analyzer and the mRNA expression of LXRα in hepatocytes was examined by RT-PCR. RESULTS: Compared to normal control group, Oil red O staining presented numerous orange-red or red lipid droplets in the cytoplasm of human L02 hepatocytes in model group. The content of TG in model group were significantly increased (P<0.01). After treated with PNS for 24 h, the content of TG in PNS treatment groups was significant decreased than that in spontaneous recovery group (P<0.05), especially in low concentration of PNS group (P<0.01). The accumulation of lipid droplets in low concentration of PNS group was decreased significantly. Compared to normal control group, the mRNA expression of LXRα in model group was significantly up-regulated (P<0.01). Compared to spontaneous recovery group, the mRNA expression of LXRα in PNS treatment groups declined in different levels, especially in low concentration group (P<0.05).CONCLUSION: The deposition of lipid in hepatocytes might be related to the high expression of LXRα mRNA. PNS decreases the content of TG in steatotic hepatocytes and promotes the recovery of hepatocyte steatosis by downregulating the mRNA level of LXRα.     

Effects of nitrogen application rates on the leaf qualityof‘Cabernet Gernischet’in desert areas北大核心CSCD

【Objective】As an essential mineral element in plant growth and development, nitrogen has irreplaceable roles in organ construction, nutritive metabolism, biochemical processes as well as fruit yield and quality. The quality and yield of grapes are greatly influenced by the amount of nitrogen applied. In recent years, the industry of China's wine grape has developed rapidly, but there are problems with unreasonable fertilization in production. The Gansu Corridor has the climatic conditions and geographical resources suitable for producing high-quality wine grapes. However, wine grapes are extensively planted on a sandy loam soil with low organic matter. In the actual production, chemical fertilizers are often applied to ensure the normal growth and development of the grapes. At the same time, water-saving agriculture has become the demand for agricultural development in this area. The aim of our study is to investigate the effects of nitrogen application rates on key enzyme activities and related gene expression during nitrogen metabolism, so as to further provide a theoretical reference for the application of nitrogen in wine grape growing in the Gansu Corridor. 【Methods】The experiment was carried out in a 10-year-old‘Cabernet Gernischet’vineyard of the Mo Gao located in Wuwei City from 2014 to 2015. All the grapevines were planted from west to east with simple hedge-shape. The planting spacing was 0.7 m×3.0 m. The area of the plot was about 240 m2, and each plot contained 40 plants. During the test period, the irrigation was carried out according to the“Wuwei Mo Gao Brewing Grape Drip Irrigation Water Distribution Quota”, which formulated by the research team. The irrigation amount in the bud break stage was 675 m3·hm-2, the flowering stage was 900 m3·hm-2, the first berry swell period was 900 m3·hm-2, the secondary shoot growth period was 150 m3·hm-2, and the second berry swell period was 600 m3 · hm- 2, and overwintering water was 1 275 m3 · hm- 2. The total irrigation amount during the whole growth period was 4 500 m3·hm-2. Five different application amounts of nitrogen (0 kg·hm-2, 150 kg·hm-2, 300 kg·hm-2, 450 kg·hm-2 and 600 kg·hm-2, characterized as CK、N1、N2、N3 and N4, respectively) were applied with a completely randomized block. Urea was used as external nitrogen and applied with water. The 750 kg·hm-2 of calcium superphosphate was applied before the first irrigation during the soil excavation. The 825 kg·hm-2 of potassium sulfate was applied in fruit color-changing period. Effects of nitrogen application rates on total nitrogen content, soluble protein content, key enzyme activities including nitrate reductase(NR), glutamine synthetase(GS), glutamate synthase(GOGAT) and glutamate dehydrogenase(GDH) as well as the related gene expression levels in leaves (VvNR1, VvGS1, VvGOGAT1 and VvGDH1) were determined at different developmental stages (5th day before anthesis, 20th day after anthesis, 50th day after anthesis, 80th day after anthesis). Ten to fifteen leaves were collected from each treatment. Fresh leaves were punched out with a punch and 1.0 g was weighed for determination of soluble protein content and enzyme activity assay with 3 replicates. The new leaves without pests and diseases on the top of the current shoots were selected to extract RNA. 2.0 g of grape leaves wrapped in tin foil were placed in a liquid nitrogen tank and stored in arefrigerator at -80℃ for RNA extraction. 【Results】The results showed that nitrogen application significantly increased the net photosynthetic rate in leaves. The treatment of N2 significantly increased leaf area and the total nitrogen content in leaves in comparison with CK 5th day before anthesis, 20th day after anthesis and 80th day after anthesis. The soluble protein content increased by nitrogen application in leaves on 80th day after anthesis. The NR activity in leaves showed an increasing trend with the increase of nitrogen application in the range of 0 to 300 kg on 5th day before anthesis, 20th day after anthesis and 80th day after anthesis. The GS activity in leaves increased significantly by N2 treatment on 5th day before anthesis, 50th day after anthesis and 80th day after anthesis, which were 1.66, 1.25 and 1.34 times more than the control, respectively. The GOGAT activity in leaves increased significantly by N2 treatment on 5th day before anthesis and 80th day after anthesis, 0.53 and 0.42μmol·g-1·min-1, respectively. Compared with CK, N2 and N3 treatments could improve the GDH activity in leaves during the whole growing period. The expression level of VvNR1 in N2 treatment was significantly higher than CK and other nitrogen treatments on 5th day before anthesis, 20th day after anthesis and 80th day after anthesis. VvGS1 was significantly up-regulated by N1 and N2 on 5th day before anthesis, which was up-regulated by 142.33% and 283.47% in comparison with CK, respectively. VvGDH1 was up-regulated during the whole growing period after nitrogen application. With N2 treatment, fruit soluble sugar, the ratio of sugar to acid, tannins, anthocyanin content reached the maximum, the titratable acid content was the lowest, the yield was at a medium level. 【Conclusion】The results suggested that different nitrogen application rates affected the expression of VvNR1, VvGS1, VvGOGAT1 and VvGDH1 genes in leaves, thereby improving leaf nitrogen metabolism. In addition, the nitrogen application with 300kg·hm-2 (N2) among all the treatments significantly promoted the accumulation of nitrogen in leaves during the late growth period. At the same time, it promoted the increase of leaf area and net photosynthetic rate, and improved the fruit quality. © 2019 Journal of Fruit Science     

Accounting for spatial autocorrelation improves the estimation of climate,physical environment and vegetation’s effects on boreal forest’s burn rates

Context

Wildfires play a crucial role in maintaining ecological and societal functions of North American boreal forests. Because of their contagious way of spreading, using statistical methods dealing with spatial autocorrelation has become a major challenge in fire studies analyzing how environmental factors affect their spatial variability.

Objectives

We aimed to demonstrate the performance of a spatially explicit method accounting for spatial autocorrelation in burn rates modelling, and to use this method to determine the relative contribution of climate, physical environment and vegetation to the spatial variability of burn rates between 1972 and 2015.

Methods

Using a 482,000 km² territory located in the coniferous boreal forest of eastern Canada, we built and compared burn rates models with and without accounting for spatial autocorrelation. The relative contribution of climate, physical environment and vegetation to the burn rates variability was identified with variance partitioning.

Results

Accounting for spatial autocorrelation improved the models’ performance by a factor of 1.5. Our method allowed the unadulterated extraction of the contribution of climate, physical environment and vegetation to the spatial variability of burn rates. This contribution was similar for the three groups of factors. The spatial autocorrelation extent was linked to the fire size distribution.

Conclusions

Accounting for spatial autocorrelation can highly improve models and avoids biased results and misinterpretation. Considering climate, physical environment and vegetation altogether is essential, especially when attempting to predict future area burned. In addition to the direct effect of climate, changes in vegetation could have important impacts on future burn rates.