Late-rotation fertilization of Norway spruce stands is a frequently used management tool in Fennoscandia to increase timber yields. Meanwhile, the growing demand for renewable resources has sparked great interest in earlier and repeated fertilizer application but it remains unclear how this affects carbon dioxide (CO₂) fluxes in the understory, especially forest floor respiration (R_ff). This study investigated the effects of forest fertilization on R_ff and net forest floor exchange (NFFE) in young, nitrogen (N) limited Norway spruce stands in southern Sweden. In a short-term dose experiment, R_ff and NFFE were recorded during 2016 after varying doses of N (0,150, 300, or 450 kg ha-1 of N, hereafter N0, N150, N300, N450) were added to circular, 3-m-diameter plots in April. In a second, long-term experiment, two stand-level fertilizer applications with 150 kg ha^-1 of N on each occasion were performed in 2014 and 2016 and R_ff was measured at semi-regular intervals from mid-2013 to the end of 2017. In the dose experiment, fertilization increased R_ff by 23 %, 81 % and 55 % in the N150, N300 and N450 treatments, respectively. Under well-lit conditions, the N300 and N450 treatments significantly enhancedphotosynthetic CO₂ uptake of the forest floor vegetation by 97 % and 66 %, respectively, while the N150 treatment had no significant effect. The results of the long-term experiment indicate an initial stimulation of R_ff, but this effect was transient. Our findings imply that fertilization in young Norway spruce stands, using the N150 dose (the typical dose used in Swedish forestry), may cause a transient burst in R_ff that is far outweighed bynutrient-driven increases in forest floor photosynthesis under favourable light conditions prior to canopy closure.

1. Whether and how the responses of above- (AGB) and below-ground biomass (BGB) and above-ground net primary production (ANPP) to global changes are linked to plant functional traits is unclear.
2. We conducted a global meta-analysis based on 2561 observations from 318 manipulative studies (primarily forest, grassland and cropland monocultures) to examine the effect of plant functional traits (i.e. morphological and chemical traits, mycorrhizal association type and symbiotic nitrogen (N) fixation) of dominant species on the responses of plant biomass production to global change drivers, that is, elevated CO₂ (eCO₂), elevated nutrient (eNutrient), elevated water (eWater), warming and drought.
3. Across all terrestrial ecosystems studied, eCO₂, eNutrient and eWater increased, while drought reduced biomass production. Warming had no overall effect on any of the biomass production metrics. Importantly, the positive effects of eNutrient on BGB were more pronounced for communities dominated by ‘fast’ species (with high specific leaf area and leaf N content). Plant communities dominated by plants with low resource uptake rates by roots exhibited stronger effects of eCO₂ on ANPP and weaker effects of eNutrient on AGB, BGB and ANPP. In communities dominated by arbuscular mycorrhizal fungi-associated plants, eNutrient increased AGB and ANPP, and drought reduced AGB. In contrast, eNutrient and drought increased BGB in communities dominated by ectomycorrhizal fungi-associated plants. eCO₂ increased ANPP in communities dominated by non-N-fixing species but not in communities dominated by N-fixing species.
4. Synthesis. Accounting for functional traits of dominant plants improves the predictability of ecosystem responses to global change, and can guide ecological management practices to safeguard key ecosystem functions in a rapidly changing world.

The state of within-stand variation (WSV) in boreal, coniferous production forests and how it is dealt with in thinning operations is a scarcely researched topic. In the autumn of 2018, we surveyed a series of Norway spruce (Picea abies (L.) Karst) or Scots pine (Pinus sylvestris L.) dominated production stands scheduled for first commercial thinning from below. Here, we evaluate the potential causes of WSV in basal area, how WSV was addressed in the thinning operations, and finally how the stands and subsequent thinning practice conformed with the basal area target specified in the thinning guidelines. WSV in the yield attributes was defined as the dispersion in a stand attribute within a stand and quantified using the Qn scale estimator (a robust measure of dispersion). First, WSV in basal area at the time of first thinning was evaluated as a function of WSV in stem number and WSV in site index. Next, yield attributes before and after thinning were compared using paired ttests, and the future development of WSV in basal area was evaluated using linear mixed-effects models. Finally, the thinning practice was evaluated before and after thinning by modelling the compliance with the basal area target as a function of stem number and dominant height, also using linear mixed-effects models. WSV in basal area appeared to be influenced by WSV in site index and WSV in stem number for Norway spruce, but not for Scots pine. Thinning reduced the WSV in basal area, standing volume, and stem number, while dominant height, quadratic mean diameter and basal area weighted mean height remained unaffected. At first thinning, compliance with the thinning guideline increased with increasing stem density and dominant height. However, moderate to high compliance with the basal area target in the thinning guidelines was only reached for plots with elevated dominant height (>15 m) in combination with high stem number (>2250 N ha-1). Thus, the recommended range in dominant height (12-14 m) for first thinning was generally exceeded, which may be attributed to the generally low stem number at the time of thinning. This study suggests that sub-optimal regeneration efforts and management of young forests can lead to WSV across a wide range of stand attributes, and likely also reductions in yield. Thinning decreased WSV in basal area, standing volume and stem number, however, the plots were heavily thinned to such a degree that it could potentially cause production losses.

Unravelling slow ecosystem migration patterns requires a fundamental understanding of the broad-scale climatic drivers, which are further modulated by fine-scale heterogeneities just outside established ecosystem boundaries. While modern Unoccupied Aerial Vehicle (UAV) remote sensing approaches enable us to monitor local scale ecotone dynamics in unprecedented detail, they are often underutilised as a temporal snapshot of the conditions on site. In this study in the Southern Alps of New Zealand, we demonstrate how the combination of multispectral and thermal data, as well as LiDAR data (2019), supplemented by three decades (1991-2021) of treeline transect data can add great value to field monitoring campaigns by putting seedling regeneration patterns at treeline into a spatially explicit context. Orthorectification and mosaicking of RGB and multispectral imagery produced spatially extensive maps of the subalpine area (similar to 4 ha) with low spatial offset (Craigieburn: 6.14 +/- 4.03 cm; Mt Faust: 5.11 +/- 2.88 cm, mean +/- standard error). The seven multispectral bands enabled a highly detailed delineation of six ground cover classes at treeline. Subalpine shrubs were detected with high accuracy (up to 90%), and a clear identification of the closed forest canopy (Fuscospora cliffortioides, >95%) was achieved. Two thermal imaging flights revealed the effect of existing vegetation classes on ground-level thermal conditions. UAV LiDAR data acquisition at the Craigieburn site allowed us to model vegetation height profiles for similar to 6000 previously classified objects and calculate annual fine-scale variation in the local solar radiation budget (20 cm resolution). At the heart of the proposed framework, an easy-to-use extrapolation procedure was used for the vegetation monitoring datasets with minimal georeferencing effort. The proposed method can satisfy the rapidly increasing demand for high spatiotemporal resolution mapping and shed further light on current treeline recruitment bottlenecks. This low-budget framework can readily be expanded to other ecotones, allowing us to gain further insights into slow ecotone dynamics in a drastically changing climate.

Nutrient limitation of forest growth, especially nitrogen (N) deficiency, is widespread in the boreal region. N fertilisation has thus become a common silvicultural practice in Fennoscandian Norway spruce stands, but to what extent phosphorus (P) is co-limiting productivity and how initial basal area affects the growth response to N addition remains unresolved. To address these questions, two experiments were established in mid-rotation Norway spruce stands in southern Sweden where decades of high atmospheric N deposition have reduced the severity of N-limitation. In a P experiment initiated in 2011, we tested P addition alone (two applications of 200 kg P ha⁻¹) and in a second study also starting in 2011 (NP experiment), a single dose of N was administered alone (200 kg ha⁻¹ in thinned and unthinned stands, hereafter called N and N-unthinned treatments) and in combination with P (N+P = one-time 200 kg N ha⁻¹, two applications of 200 kg P ha⁻¹ in thinned stands). P addition alone increased PAI (periodic annual increment) significantly by 21 % during the first, moister assessment period up to 2014 and by 18 % in the drier 2015–2019 period, resulting in a 10 % increase in final stem volume yield. In the NP experiment, significant PAI increases under favourable meteorological conditions up to 2014 occurred in all fertilisation treatments. The strongest effects were seen in the N-unthinned treatment while no significant additive effect resulted from the joint addition of N and P (N: +20 %, N-unthinned: +38 %, N+P: +23 %). In the drier 2015–2019 period, only the N+P treatment caused significantly greater PAI (+29 %). Final stem volume yield in the NP experiment significantly increased by 10 %, 39 % and 16 % in the N, N-unthinned and N+P plots, respectively. In both experiments, foliar P and thus P/N rose drastically in response to P addition alone or in combination with N. Minor increases in leaf area index (LAI) only occurred in P-containing treatments. Our findings indicate that Norway spruce productivity in southern Sweden is constrained to a similar extent by both N and P. Sustainable nutrient management in Norway spruce growing regions with high N loading (like southern Sweden) should prioritise P over N supply.

An accessible learning resource that develops data analysis skills for natural science students in an efficient style using the R programming language R-ticulate: A Beginner’s Guide to Data Analysis for Natural Scientists is a compact, example-based, and user-friendly statistics textbook without unnecessary frills, but instead filled with engaging, relatable examples, practical tips, online exercises, resources, and references to extensions, all on a level that follows contemporary curricula taught in large parts of the world. The content structure is unique in the sense that statistical skills are introduced at the same time as software (programming) skills in R. This is by far the best way of teaching from the authors’ experience. Readers of this introductory text will find: Explanations of statistical concepts in simple, easy-to-understand language A variety of approaches to problem solving using both base R and tidyverse Boxes dedicated to specific topics and margin text that summarizes key points A clearly outlined schedule organized into 12 chapters corresponding to the 12 semester weeks of most universities While at its core a traditional printed book, R-ticulate: A Beginner’s Guide to Data Analysis for Natural Scientists comes with a wealth of online teaching material, making it an ideal and efficient reference for students who wish to gain a thorough understanding of the subject, as well as for instructors teaching related courses.

Soil respiration rates (R_s) were measured in New Zealand dairy grassland.

Both season and soil type significantly affected R_s.

Soil temperature and soil type dominated overall R_s.

Soil respiration (R_s), the CO₂ release from root respiration and microbial metabolism, affects global soil carbon storage and cycling. Only few studies have looked at R_s in the southern hemisphere, especially regarding the interaction between soil type and environmental factors on R_s in dairy grassland. We investigated the relationship between R_s and soil temperature (T_s), soil water content (SWC), soil type, and other environmental factors based on summer and winter measurements at four sites in New Zealand. Across sites, soil respiration rates ranged from 0.29 to 14.58 with a mean of 5.38 +/- 0.13 (mean +/- standard error) mu mol CO₂ m-2 s-1. Mean summer R s was 86.5% higher than mean winter R_s, largely driven by organic/gley and pumice soils while ultic soils showed very little seasonal temperature sensitivity. Overall mean R_s in organic/gley soils was 108.0% higher than that in ultic soils. The high R_s rate observed in organic/gley was likely due to high soil organic matter content, while low R_s in ultic and pallic soils resulted from high clay content and low hydraulic conductance. Soil temperature drove overall R_s. Our findings indicate that soil type and soil temperature together best explain R_s. This implies that a mere classification of land use type may be insufficient for global C models and should be supplemented with soil type information, at least locally.

Silvicultural techniques aimed at promoting forest biomass production can help meet the growing demand for renewable materials and mitigate climate change. One-time nitrogen (N) addition late in the rotation is a well-established method to stimulate growth in coniferous forests in northern Europe, but the potential gains from earlier and repeated fertiliser application remain uncertain. Here, we tested the impact of repeated fertilisation in juvenile Norway spruce stands across 9 sites covering a wide range of growing conditions over a 700 km stretch from central to southern Sweden. We tested the fertilisation effects using two separate studies: i) an interval trial with a fertilisation frequency of one (F1), two (F2), or three years (F3) performed at plot-level across five sites (2002–2014), and ii) a practice-oriented trial with a two-year fertilisation interval (F2) applied at stand-level and replicated at four sites (2003–2013). The composition of the nutrient mix in each plot was optimised based on foliar nutrient analyses. In the interval trial, all three fertilisation schedules strongly increased periodic annual increment (PAI) (F1: 105 %, F2: 93 %, F3: 79 %) relative to the unfertilised control, resulting in more than a doubling of stem volume yield in the F1 and F2 treatments (120 % and 110 %, respectively) and a significantly smaller but still sizeable yield stimulation of 82 % in the F3 treatment. Nitrogen use efficiency (NUE, stemwood volume increase per unit mass of N added) was similar among fertilisation intervals (on average 130 m³ ha−1 1000 kg N⁻¹), indicating that the extra N provided through yearly fertilisation (F1) is redundant given the similar stemwood yields in the F2 treatment. In the practice-oriented trial, the sole F2 treatment increased PAI by 95 % over the control, translating into a yield stimulation of 114 % and an almost identical NUE to that of the interval trial. NUE greatly exceeded the figures typically observed with traditional late-rotation fertilisation and correlated inversely with baseline site productivity (using site index as a proxy) in the F1 and F2 treatments (the latter pooled across the two trials). Our results clearly indicate that nutrient limitation restricts growth and carbon (C) capture in young Norway spruce plantations in northern Europe to less than half of their potential, highlighting repeated fertilisation at nutrient-poor sites as an effective management tool to support a growing bioeconomy and enhance C sequestration.

Low nutrient availability often limits productivity in northern forests. In a nutrient optimisation trial, we investigated the effects of fertilisation and irrigation on soil moisture, leaf area index (LAI) as well as height and radial growth in 25-year-old stands of pedunculate and sessile oak (Quercus robur L., Q. petraea (Matt.) Liebl.) growing on abandoned farmland in southwestern Sweden. Control (C), fertilisation (F), irrigation (I), and irrigation +fertilisation (IF) treatments were arranged in a randomized complete block design. End of growing season analysis of foliar nutrients guided the quantitative composition of next year’s fertiliser mix. Volumetric soil moisture (VWC) was significantly higher in the I and IF treatments compared to the C and F treated stands of both oak species. We did not observe a fertiliser-related reduction in VWC (except for 2015, when VWC in F- treated Q. robur stands was significantly lower than the control by about 18 %). This is in line with the unaffected LAI estimates (5.3–5.9) suggesting no stimulation of leaf production that could drive increases in transpiration with subsequent soil moisture depletion. There was no treatment ×year interaction for any of the growth-related variables. Treatments had no significant effects on basal area growth, which increased annually by 1.72 and 1.54 m² ha^-1 on average for Q. petraea and Q. robur, respectively. Pre-treatment height differences in Q. petraea stands (7–12 % taller trees in the C and IF plots) persisted throughout the study resulting in significant effects, while no significant differences in height occurred in Q. robur. Periodic annual volume increment varied more strongly following drier periods but there were no significant differences among treatments. Our findings indicate that fertilisation causes no or only minor increases in oak water use, suggesting that nutrient addition in oak stands within this precipitation regime does not require simultaneous irrigation. Most importantly, our data implies that the soil nutrient legacies of past agricultural use suffice to maximise the productivity of oak stands on abandoned farmland typical of the main oak growing region in southwestern Sweden.

Optimal stomatal theory predicts that stomata operate to maximise photosynthesis (A(net)) and minimise transpirational water loss to achieve optimal intrinsic water-use efficiency (iWUE). We tested whether this theory can predict stomatal responses to elevated atmospheric CO2 (eCO(2)), and whether it can capture differences in responsiveness among woody plant functional types (PFTs). We conducted a meta-analysis of tree studies of the effect of eCO(2) on iWUE and its components A(net) and stomatal conductance (g(s)). We compared three PFTs, using the unified stomatal optimisation (USO) model to account for confounding effects of leaf-air vapour pressure difference (D). We expected smaller g(s), but greater A(net), responses to eCO(2) in gymnosperms compared with angiosperm PFTs. We found that iWUE increased in proportion to increasing eCO(2) in all PFTs, and that increases in A(net) had stronger effects than reductions in g(s). The USO model correctly captured stomatal behaviour with eCO(2) across most datasets. The chief difference among PFTs was a lower stomatal slope parameter (g(1)) for the gymnosperm, compared with angiosperm, species. Land surface models can use the USO model to describe stomatal behaviour under changing atmospheric CO2 conditions.