共查询到20条相似文献,搜索用时 15 毫秒
1.
GERALDINE L. TIERNEY TIMOTHY J. FAHEY PETER M. GROFFMAN† JANET P. HARDY‡ ROSS D. FITZHUGH§ CHARLES T. DRISCOLL¶ JOSEPH B. YAVITT 《Global Change Biology》2003,9(5):670-679
Understanding how exogenous and endogenous factors control the distribution, production and mortality of fine roots is fundamental to assessing the implications of global change, yet our knowledge of control over fine root dynamics remains rudimentary. To improve understanding of these processes, the present study developed regression relationships between environmental variables and fine root dynamics within a northern hardwood forest in New Hampshire, USA, which was experimentally manipulated with a snow removal treatment. Fine roots (< 1 mm diameter) were observed using minirhizotrons for 2 years in sugar maple and yellow birch stands and analyzed in relation to temperature, water and nutrient availability. Fine root dynamics at this site fluctuated seasonally, with growth and mortality peaking during warmer months. Monthly fine root production was strongly associated with mean monthly air temperature and neither soil moisture nor nutrient availability added additional predictive power to this relationship. This relationship exhibited a seasonal temperature hysteresis, which was altered by snow removal treatment. These results suggest that both exogenous and endogenous cues may be important in controlling fine root growth in this system. Proportional fine root mortality was directly associated with mean monthly soil temperature, and proportional fine root mortality during the over‐winter interval was strongly related to whether the soil froze. The strong relationship between fine root production and air temperature reported herein contrasts with findings from some hardwood forest sites and indicates that controls on fine root dynamics vary geographically. Future research must more clearly distinguish between endogenous and exogenous control over fine root dynamics in various ecosystems. 相似文献
2.
Effects of mild winter freezing on soil nitrogen and carbon dynamics in a northern hardwood forest 总被引:27,自引:5,他引:27
Peter M. Groffman Charles T. Driscoll Timothy J. Fahey Janet P. Hardy Ross D. Fitzhugh Geraldine L. Tierney 《Biogeochemistry》2001,56(2):191-213
Overwinter and snowmelt processes are thought to be critical to controllersof nitrogen (N) cycling and retention in northern forests. However, therehave been few measurements of basic N cycle processes (e.g.mineralization, nitrification, denitrification) during winter and littleanalysis of the influence of winter climate on growing season N dynamics.In this study, we manipulated snow cover to assess the effects of soilfreezing on in situ rates of N mineralization, nitrification and soilrespiration, denitrification (intact core, C2H2 – based method),microbial biomass C and N content and potential net N mineralization andnitrification in two sugar maple and two yellow birch stands with referenceand snow manipulation treatment plots over a two year period at theHubbard Brook Experimental Forest, New Hampshire, U.S.A. The snowmanipulation treatment, which simulated the late development of snowpackas may occur in a warmer climate, induced mild (temperatures >–5 °C) soil freezing that lasted until snowmelt. The treatmentcaused significant increases in soil nitrate (NO3
–)concentrations in sugar maple stands, but did not affect mineralization,nitrification, denitrification or microbial biomass, and had no significanteffects in yellow birch stands. Annual N mineralization and nitrificationrates varied significantly from year to year. Net mineralization increasedfrom 12.0 g N m–2 y–1 in 1998 to 22 g N m–2 y–1 in 1999 and nitrification increased from 8 g N m–2 y–1 in 1998 to 13 g N m–2 y–1 in 1999.Denitrification rates ranged from 0 to 0.65 g N m–2 y–1. Ourresults suggest that mild soil freezing must increase soil NO3
– levels by physical disruption of the soil ecosystem and not by direct stimulation of mineralization and nitrification. Physical disruption canincrease fine root mortality, reduce plant N uptake and reduce competitionfor inorganic N, allowing soil NO3
– levels to increase evenwith no increase in net mineralization or nitrification. 相似文献
3.
Increased nitrogen leaching following soil freezing is due to decreased root uptake in a northern hardwood forest 总被引:1,自引:0,他引:1
Pamela H. Templer 《Global Change Biology》2014,20(8):2663-2673
The depth and duration of snow pack is declining in the northeastern United States as a result of warming air temperatures. Since snow insulates soil, a decreased snow pack can increase the frequency of soil freezing, which has been shown to have important biogeochemical implications. One of the most notable effects of soil freezing is increased inorganic nitrogen losses from soil during the following growing season. Decreased nitrogen retention is thought to be due to reduced root uptake, but has not yet been measured directly. We conducted a 2‐year snow‐removal experiment at Hubbard Brook Experimental Forest in New Hampshire, USA to determine the effects of soil freezing on root uptake and leaching of inorganic nitrogen simultaneously. Snow removal significantly increased the depth of maximal soil frost by 37.2 and 39.5 cm in the first and second winters, respectively (P < 0.001 in 2008/2009 and 2009/2010). As a consequence of soil freezing, root uptake of ammonium declined significantly during the first and second growing seasons after snow removal (P = 0.023 for 2009 and P = 0.005 for 2010). These observed reductions in root nitrogen uptake coincided with significant increases in soil solution concentrations of ammonium in the Oa horizon (P = 0.001 for 2009 and 2010) and nitrate in the B horizon (P < 0.001 and P = 0.003 for 2009 and 2010, respectively). The excess flux of dissolved inorganic nitrogen from the Oa horizon that was attributable to soil freezing was 7.0 and 2.8 kg N ha?1 in 2009 and 2010, respectively. The excess flux of dissolved inorganic nitrogen from the B horizon was lower, amounting to 1.7 and 0.7 kg N ha?1 in 2009 and 2010, respectively. Results of this study provide direct evidence that soil freezing reduces root nitrogen uptake, demonstrating that the effects of winter climate change on root function has significant consequences for nitrogen retention and loss in forest ecosystems. 相似文献
4.
Evaluating minirhizotron estimates of fine root longevity and production in the forest floor of a temperate broadleaf forest 总被引:11,自引:0,他引:11
The minirhizotron technique (MR) for in situ measurement of fine root dynamics offers the opportunity to obtain accurate and unbiased estimates of root production in perennial vegetation only if MR tubes do not affect the longevity of fine roots. Assuming fine root biomass is near steady-state, fine root production (g m–2 yr–1) can be estimated as the ratio of fine root biomass (g m–2) to median fine root longevity (yr). This study evaluates the critical question of whether MR access tubes affect the longevity of fine roots, by comparing fine root survivorship obtained using MR with those from a non-intrusive in situ screen method in the forest floor horizons of a northern hardwood forest in New Hampshire, USA. Fine root survivorship was measured in 380 root screens during 1993–1997 and in six horizontal minirhizotron tubes during 1996–1997. No statistically significant difference was found between estimates of survivorship of fine roots (<1 mm dia.) at this site from MR versus from in situ screens, suggesting that MR tubes do not substantially affect fine root longevity in the forest floor of this northern hardwood forest and providing greater confidence in measurements of fine root production using the MR technique. Furthermore, the methodology for estimating fine root production from MR longevity data was evaluated by comparison of fine root longevity and production estimates made using single vs. multiple root cohorts, and using root-number, root-length, and root-mass weighted methods. Our results indicate that fine root-length longevity estimates based on multiple root cohorts throughout the year can be used to approximate fine root biomass production. Using this method, we estimated fine root longevity and production in the forest floor at this site to be 314 days (or 0.86 yr) and 303 g m–2 yr–1, respectively. Fine root production in this northern hardwood forest is approximately equivalent to standing biomass and was previously underestimated by root in-growth cores. We conclude that the use of MR to estimate fine root longevity and production as outlined here may result in improved estimates of fine root production in perennial vegetation. 相似文献
5.
Relationships between fine root dynamics and nitrogen availability in Michigan northern hardwood forests 总被引:38,自引:0,他引:38
Minirhizotrons were used to observe fine root (Б mm) production, mortality, and longevity over 2 years in four sugar-maple-dominated northern hardwood forests located along a latitudinal temperature gradient. The sites also differed in N availability, allowing us to assess the relative influences of soil temperature and N availability in controlling fine root lifespans. Root production and mortality occurred throughout the year, with most production occurring in the early portion of the growing season (by mid-July). Mortality was distributed much more evenly throughout the year. For surface fine roots (0-10 cm deep), significant differences in root longevity existed among the sites, with median root lifespans for root cohorts produced in 1994 ranging from 405 to 540 days. Estimates of fine root turnover, based on the average of annual root production and mortality as a proportion of standing crop, ranged from 0.50 to 0.68 year-1 for roots in the upper 30 cm of soil. The patterns across sites in root longevity and turnover did not follow the north to south temperature gradient, but rather corresponded to site differences in N availability, with longer average root lifespans and lower root turnover occurring where N availability was greater. This suggests the possibility that roots are maintained as long as the benefit (nutrients) they provide outweighs the C cost of keeping them alive. Root N concentrations and respiration rates (at a given temperature) were also higher at sites where N availability was greater. It is proposed that greater metabolic activity for roots in nitrogen-rich zones leads to greater carbohydrate allocation to those roots, and that a reduction in root C sink strength when local nutrients are depleted provides a mechanism through which root lifespan is regulated in these forests. 相似文献
6.
Snow depth, soil freezing, and fluxes of carbon dioxide, nitrous oxide and methane in a northern hardwood forest 总被引:14,自引:0,他引:14
PETER M. GROFFMAN JANET P. HARDY† CHARLES T. DRISCOLL‡ TIMOTHY J. FAHEY§ 《Global Change Biology》2006,12(9):1748-1760
Soil–atmosphere fluxes of trace gases (especially nitrous oxide (N2 O)) can be significant during winter and at snowmelt. We investigated the effects of decreases in snow cover on soil freezing and trace gas fluxes at the Hubbard Brook Experimental Forest, a northern hardwood forest in New Hampshire, USA. We manipulated snow depth by shoveling to induce soil freezing, and measured fluxes of N2 O, methane (CH4 ) and carbon dioxide (CO2 ) in field chambers monthly (bi-weekly at snowmelt) in stands dominated by sugar maple or yellow birch. The snow manipulation and measurements were carried out in two winters (1997/1998 and 1998/1999) and measurements continued through 2000. Fluxes of CO2 and CH4 showed a strong seasonal pattern, with low rates in winter, but N2 O fluxes did not show strong seasonal variation. The snow manipulation induced soil freezing, increased N2 O flux and decreased CH4 uptake in both treatment years, especially during winter. Annual N2 O fluxes in sugar maple treatment plots were 207 and 99 mg N m−2 yr−1 in 1998 and 1999 vs. 105 and 42 in reference plots. Tree species had no effect on N2 O or CO2 fluxes, but CH4 uptake was higher in plots dominated by yellow birch than in plots dominated by sugar maple. Our results suggest that winter fluxes of N2 O are important and that winter climate change that decreases snow cover will increase soil:atmosphere N2 O fluxes from northern hardwood forests. 相似文献
7.
Fine root growth phenology,production, and turnover in a northern hardwood forest ecosystem 总被引:19,自引:2,他引:19
A large part of the nutrient flux in deciduous forests is through fine root turnover, yet this process is seldom measured. As part of a nutrient cycling study, fine root dynamics were studied for two years at Huntington Forest in the Adirondack Mountain region of New York, USA. Root growth phenology was characterized using field rhizotrons, three methods were used to estimate fine root production, two methods were used to estimate fine root mortality, and decomposition was estimated using the buried bag technique. During both 1986 and 1987, fine root elongation began in early April, peaked during July and August, and nearly ceased by mid-October. Mean fine root ( 3 mm diameter) biomass in the surface 28-cm was 2.5 t ha–1 and necromass was 2.9 t ha–1. Annual decomposition rates ranged from 17 to 30% beneath the litter and 27 to 52% at a depth of 10 cm. Depending on the method used for estimation, fine root production ranged from 2.0 to 2.9 t ha–1, mortality ranged from 1.8 to 3.7 t ha–1 yr–1, and decomposition was 0.9 t ha–1 yr–1. Thus, turnover ranged from 0.8 to 1.2 yr–1. The nutrients that cycled through fine roots annually were 4.5–6.1 kg Ca, 1.1–1.4 kg Mg, 0.3–0.4 kg K, 1.2–1.7 kg P, 20.3–27.3 kg N, and 1.8–2.4 kg S ha–1. Fine root turnover was less important than leaf litterfall in the cycling of Ca and Mg and was similar to leaf litterfall in the amount of N, P, K and S cycled. 相似文献
8.
9.
Phenology of a northern hardwood forest canopy 总被引:4,自引:0,他引:4
ANDREW D. RICHARDSON AMEY SCHENCK BAILEY† ELLEN G. DENNY‡ C. WAYNE MARTIN† JOHN O'KEEFE§ 《Global Change Biology》2006,12(7):1174-1188
While commonplace in other parts of the world, long‐term and ongoing observations of the phenology of native tree species are rare in North America. We use 14 years of field survey data from the Hubbard Brook Experimental Forest to fit simple models of canopy phenology for three northern hardwood species, sugar maple (Acer saccharum), American beech (Fagus grandifolia), and yellow birch (Betula alleghaniensis). These models are then run with historical meteorological data to investigate potential climate change effects on phenology. Development and senescence are quantified using an index that ranges from 0 (dormant, no leaves) to 4 (full, green canopy). Sugar maple is the first species to leaf out in the spring, whereas American beech is the last species to drop its leaves in the fall. Across an elevational range from 250 to 825 m ASL, the onset of spring is delayed by 2.7±0.4 days for every 100 m increase in elevation, which is in reasonable agreement with Hopkin's law. More than 90% of the variation in spring canopy development, and just slightly less than 90% of the variation in autumn canopy senescence, is accounted for by a logistic model based on accumulated degree‐days. However, degree‐day based models fit to Hubbard Brook data appear to overestimate the rate at which spring development occurs at the more southerly Harvard Forest. Autumn senescence at the Harvard Forest can be predicted with reasonable accuracy in sugar maple but not American beech. Retrospective modeling using five decades (1957–2004) of Hubbard Brook daily mean temperature data suggests significant trends (P≤0.05) towards an earlier spring (e.g. sugar maple, rate of change=0.18 days earlier/yr), consistent with other studies documenting measurable climate change effects on the onset of spring in both North America and Europe. Our results also suggest that green canopy duration has increased by about 10 days (e.g. sugar maple, rate of change=0.21 days longer/yr) over the period of study. 相似文献
10.
Global patterns of root turnover for terrestrial ecosystems 总被引:42,自引:1,他引:42
Root turnover is a critical component of ecosystem nutrient dynamics and carbon sequestration and is also an important sink for plant primary productivity. We tested global controls on root turnover across climatic gradients and for plant functional groups by using a database of 190 published studies. Root turnover rates increased exponentially with mean annual temperature for fine roots of grasslands ( r 2 = 0.48) and forests ( r 2 = 0.17) and for total root biomass in shrublands ( r 2 = 0.55). On the basis of the best-fit exponential model, the Q 10 for root turnover was 1.4 for forest small diameter roots (5 mm or less), 1.6 for grassland fine roots, and 1.9 for shrublands. Surprisingly, after accounting for temperature, there was no such global relationship between precipitation and root turnover. The slowest average turnover rates were observed for entire tree root systems (10% annually), followed by 34% for shrubland total roots, 53% for grassland fine roots, 55% for wetland fine roots, and 56% for forest fine roots. Root turnover decreased from tropical to high-latitude systems for all plant functional groups. To test whether global relationships can be used to predict interannual variability in root turnover, we evaluated 14 yr of published root turnover data from a shortgrass steppe site in northeastern Colorado, USA. At this site there was no correlation between interannual variability in mean annual temperature and root turnover. Rather, turnover was positively correlated with the ratio of growing season precipitation and maximum monthly temperature ( r 2 = 0.61). We conclude that there are global patterns in rates of root turnover between plant groups and across climatic gradients but that these patterns cannot always be used for the successful prediction of the relationship of root turnover to climate change at a particular site. 相似文献
11.
JOSEPH B. YAVITT KYLE E. HARMS MILTON N. GARCIA MATT J. MIRABELLO S. JOSEPH WRIGHT 《Austral ecology》2011,36(4):433-445
The question of how tropical trees cope with infertile soils has been challenging to address, in part, because fine root dynamics must be studied in situ. We used annual fertilization with nitrogen (N as urea, 12.5 g N m?2 year?1), phosphorus (P as superphosphate, 5 g P m?2 year?1) and potassium (K as KCl, 5 g K m?2 year?1) within 38 ha of old‐growth lowland tropical moist forest in Panama and examined fine root dynamics with minirhizotron images. We expected that added P, above all, would (i) decrease fine root biomass but, (ii) have no impact on fine root turnover. Soil in the study area was moderately acidic (pH = 5.28), had moderate concentrations of exchangeable base cations (13.4 cmol kg?1), low concentrations of Bray‐extractable phosphate (PO4 = 2.2 mg kg?1), and modest concentrations of KCl‐extractable nitrate (NO3 = 5.0 mg kg?1) and KCl‐extractable ammonium (NH4 = 15.5 mg kg?1). Added N increased concentrations of KCl‐extractable NO3 and acidified the soil by one pH unit. Added P increased concentrations of Bray‐extractable PO4 and P in the labile fraction. Concentrations of exchangeable K were elevated in K addition plots but reduced by N additions. Fine root dynamics responded to added K rather than added P. After 2 years, added K decreased fine root biomass from 330 to 275 g m?2. The turnover coefficient of fine roots <1 mm diameter ranged from 2.6 to 4.4 per year, and the largest values occurred in plots with added K. This study supported the view that biomass and dynamics of fine roots respond to soil nutrient availability in species‐rich, lowland tropical moist forest. However, K rather than P elicited root responses. Fine roots smaller than 1 mm have a short lifetime (<140 days), and control of fine root production by nutrient availability in tropical forests deserves more study. 相似文献
12.
Snow depth, soil freezing and nitrogen cycling in a northern hardwood forest landscape 总被引:2,自引:0,他引:2
Peter M. Groffman Janet P. Hardy Samuel Fashu-Kanu Charles T. Driscoll Natalie L. Cleavitt Timothy J. Fahey Melany C. Fisk 《Biogeochemistry》2011,102(1-3):223-238
Increases in soil freezing associated with decreases in snow cover have been identified as a significant disturbance to nitrogen (N) cycling in northern hardwood forests. We created a range of soil freezing intensity through snow manipulation experiments along an elevation gradient at the Hubbard Brook Experimental Forest (HBEF) in the White Mountains, NH USA in order to improve understanding of the factors regulating freeze effects on nitrate (NO3 ?) leaching, nitrous oxide (N2O) flux, potential and in situ net N mineralization and nitrification, microbial biomass carbon (C) and N content and respiration, and denitrification. While the snow manipulation treatment produced deep and persistent soil freezing at all sites, effects on hydrologic and gaseous losses of N were less than expected and less than values observed in previous studies at the HBEF. There was no relationship between frost depth, frost heaving and NO3 ? leaching, and a weak relationship between frost depth and winter N2O flux. There was a significant positive relationship between dissolved organic carbon (DOC) and NO3 ? concentrations in treatment plots but not in reference plots, suggesting that the snow manipulation treatment mobilized available C, which may have stimulated retention of N and prevented treatment effects on N losses. While the results support the hypothesis that climate change resulting in less snow and more soil freezing will increase N losses from northern hardwood forests, they also suggest that ecosystem response to soil freezing disturbance is affected by multiple factors that must be reconciled in future research. 相似文献
13.
- 1 A suite of invasive weevils has established in hardwood forests of the North American Great Lakes Region. We quantified patterns of host availability and the capacity of adults to succeed in a system with high host variability both within and between seasons in Michigan, U.S.A.
- 2 We quantified phenological development of foliage on three host species [sugar maple, Acer saccharum Marshall; ironwood, Ostrya virginiana (Mill.) K. Koch; and raspberry, Rubus spp.]. We estimated adult abundance using emergence traps and sweep net sampling over 3 years, and compared field host associations with laboratory choice assays.
- 3 Host plant phenology varied among species, between years, and in their interactions. The four most common weevils, Phyllobius oblongus (L.), Polydrusus sericeus (Schaller), Barypeithes pellucidus (Boheman) and Sciaphilus asperatus (Bonsdorff), emerged in early to mid‐June, in approximately that order. After emergence, each species showed evidence of host preference based on their abundances on foliage. Overall, P. oblongus and B. pellucidus were most prevalent on sugar maple, P. sericeus was most prevalent on ironwood, and S. asperatus was relatively evenly distributed. Laboratory choice tests with P. oblongus and P. sericeus confirmed these preferences.
- 4 These four invasive species comprised over 99% of all 12 845 weevils obtained, suggesting displacement of native species. The optimal sampling methods varied among weevil species.
- 5 These invasive weevils contend with the highly variable conditions of their environment, and also potential phenological asynchrony, via relatively late emergence, even at the cost of lower host quality. Annual variation is greater for numbers of adults than larvae, suggesting that mortality of late instars or pupae is particularly important.
14.
应用微根管法测定细根指标方法评述 总被引:7,自引:0,他引:7
树木细根(直径<2mm)在森林生态系统能量流动和物质循环中起着重要的作用。原有的细根生产周转研究中常采用的土钻法、内生长法、挖掘法、根室法和土柱法等,均不能直接观察到细根的动态变化。微根管法是一种非破坏性、可定点直接观察和研究植物根系的方法,为研究细根的生长、衰老、死亡、分解和再生长的过程提供了有效的工具,尤其适用于细根周转、寿命和分解等方面的研究。但该技术不能直接测定单位面积的细根生物量、细根化学组成及细根周转对土壤碳和养分循环的影响,需要与土钻法结合。本文就运用微根管法对细根生物量、生产、周转和寿命等指标的研究方法进行了评述。 相似文献
15.
The biomass, production and mortality of fine roots (roots with diameter <2.5 mm) were studied in a typical Mediterranean holm oak (Quercus ilex L.) forest in NE Spain using the minirhizotron methodology. A total of 1212 roots were monitored between June of 1994 and March of 1997. Mean annual fine root biomass in the holm oak forest of Prades was 71±8 g m–2 yr–1. Mean annual production for the period analysed was 260+11 g m–2 yr–1. Mortality was similar to production, with a mean value of 253±3 g m–2 yr–1. Seasonal fine root biomass presented a cyclic behaviour, with higher values in autumn and winter and lower in spring and summer. Production was highest in winter, and mortality in spring. In summer, production and mortality values were the lowest for the year. Production values in autumn and spring were very similar. The vertical distribution of fine root biomass decreased with increasing depth except for the top 10–20 cm, where values were lower than immediately below. Production and mortality values were similar between 10 and 50 cm depth. In the 0–10 cm and the 50–60 cm depth intervals, both production and mortality were lower. 相似文献
16.
Effects of soil freezing disturbance on soil solution nitrogen, phosphorus, and carbon chemistry in a northern hardwood ecosystem 总被引:17,自引:4,他引:17
Ross D. Fitzhugh Charles T. Driscoll Peter M. Groffman Geraldine L. Tierney Timothy J. Fahey Janet P. Hardy 《Biogeochemistry》2001,56(2):215-238
Reductions in snow cover undera warmer climate may cause soil freezing eventsto become more common in northern temperateecosystems. In this experiment, snow cover wasmanipulated to simulate the late development ofsnowpack and to induce soil freezing. Thismanipulation was used to examine the effects ofsoil freezing disturbance on soil solutionnitrogen (N), phosphorus (P), and carbon (C)chemistry in four experimental stands (twosugar maple and two yellow birch) at theHubbard Brook Experimental Forest (HBEF) in theWhite Mountains of New Hampshire. Soilfreezing enhanced soil solution Nconcentrations and transport from the forestfloor. Nitrate (NO3
–) was thedominant N species mobilized in the forestfloor of sugar maple stands after soilfreezing, while ammonium (NH4
+) anddissolved organic nitrogen (DON) were thedominant forms of N leaching from the forestfloor of treated yellow birch stands. Rates ofN leaching at stands subjected to soil freezingranged from 490 to 4,600 mol ha–1yr–1, significant in comparison to wet Ndeposition (530 mol ha–1 yr–1) andstream NO3
– export (25 mol ha–1yr–1) in this northern forest ecosystem. Soil solution fluxes of Pi from the forestfloor of sugar maple stands after soil freezingranged from 15 to 32 mol ha–1 yr–1;this elevated mobilization of Pi coincidedwith heightened NO3
– leaching. Elevated leaching of Pi from the forestfloor was coupled with enhanced retention ofPi in the mineral soil Bs horizon. Thequantities of Pi mobilized from the forestfloor were significant relative to theavailable P pool (22 mol ha–1) as well asnet P mineralization rates in the forest floor(180 mol ha–1 yr–1). Increased fineroot mortality was likely an important sourceof mobile N and Pi from the forest floor,but other factors (decreased N and P uptake byroots and increased physical disruption of soilaggregates) may also have contributed to theenhanced leaching of nutrients. Microbialmortality did not contribute to the acceleratedN and P leaching after soil freezing. Resultssuggest that soil freezing events may increaserates of N and P loss, with potential effectson soil N and P availability, ecosystemproductivity, as well as surface wateracidification and eutrophication. 相似文献
17.
Andrew B. Reinmann Jessica R. Susser Eleonora M. C. Demaria Pamela H. Templer 《Global Change Biology》2019,25(2):420-430
Changes in growing season climate are often the foci of research exploring forest response to climate change. By contrast, little is known about tree growth response to projected declines in winter snowpack and increases in soil freezing in seasonally snow‐covered forest ecosystems, despite extensive documentation of the importance of winter climate in mediating ecological processes. We conducted a 5‐year snow‐removal experiment whereby snow was removed for the first 4–5 weeks of winter in a northern hardwood forest at the Hubbard Brook Experimental Forest in New Hampshire, USA. Our results indicate that adverse impacts of reduced snowpack and increased soil freezing on the physiology of Acer saccharum (sugar maple), a dominant species across northern temperate forests, are accompanied by a 40 ± 3% reduction in aboveground woody biomass increment, averaged across the 6 years following the start of the experiment. Further, we find no indication of growth recovery 1 year after cessation of the experiment. Based on these findings, we integrate spatial modeling of snowpack depth with forest inventory data to develop a spatially explicit, regional‐scale assessment of the vulnerability of forest aboveground growth to projected declines in snowpack depth and increased soil frost. These analyses indicate that nearly 65% of sugar maple basal area in the northeastern United States resides in areas that typically experience insulating snowpack. However, under the RCP 4.5 and 8.5 emissions scenarios, we project a 49%–95% reduction in forest area experiencing insulating snowpack by the year 2099 in the northeastern United States, leaving large areas of northern forest vulnerable to these changes in winter climate, particularly along the northern edge of the region. Our study demonstrates that research focusing on growing season climate alone overestimates the stimulatory effect of warming temperatures on tree and forest growth in seasonally snow‐covered forests. 相似文献
18.
Regional scale patterns of fine root lifespan and turnover under current and future climate 总被引:2,自引:0,他引:2
M. Luke McCormack David M. Eissenstat Anantha M. Prasad Erica A. H. Smithwick 《Global Change Biology》2013,19(6):1697-1708
Fine root dynamics control a dominant flux of carbon from plants and into soils and mediate potential uptake and cycling of nutrients and water in terrestrial ecosystems. Understanding of these patterns is needed to accurately describe critical processes like productivity and carbon storage from ecosystem to global scales. However, limited observations of root dynamics make it difficult to define and predict patterns of root dynamics across broad spatial scales. Here, we combine species‐specific estimates of fine root dynamics with a model that predicts current distribution and future suitable habitat of temperate tree species across the eastern United States (US). Estimates of fine root lifespan and turnover are based on empirical observations and relationships with fine root and whole‐plant traits and apply explicitly to the fine root pool that is relatively short‐lived and most active in nutrient and water uptake. Results from the combined model identified patterns of faster root turnover rates in the North Central US and slower turnover rates in the Southeastern US. Portions of Minnesota, Ohio, and Pennsylvania were also predicted to experience >10% increases in root turnover rates given potential shifts in tree species composition under future climate scenarios while root turnover rates in other portions of the eastern US were predicted to decrease. Despite potential regional changes, the average estimates of root lifespan and turnover for the entire study area remained relatively stable between the current and future climate scenarios. Our combined model provides the first empirically based, spatially explicit, and spatially extensive estimates of fine root lifespan and turnover and is a potentially powerful tool allowing researchers to identify reasonable approximations of forest fine root turnover in areas where no direct observations are available. Future efforts should focus on reducing uncertainty in estimates of root dynamics by better understanding how climate and soil factors drive variability in root dynamics of different species. 相似文献
19.
Review of root dynamics in forest ecosystems grouped by climate,climatic forest type and species 总被引:17,自引:0,他引:17
Kristiina A. Vogt Daniel J. Vogt Peter A. Palmiotto Paul Boon Jennifer O'Hara Heidi Asbjornsen 《Plant and Soil》1995,187(2):159-219
Patterns of both above- and belowground biomass and production were evaluated using published information from 200 individual data-sets. Data sets were comprised of the following types of information: organic matter storage in living and dead biomass (e.g. surface organic horizons and soil organic matter accumulations), above- and belowground net primary production (NPP) and biomass, litter transfers, climatic data (i.e. precipitation and temperature), and nutrient storage (N, P, Ca, K) in above- and belowground biomass, soil organic matter and litter transfers. Forests were grouped by climate, foliage life-span, species and soil order. Several climatic and nutrient variables were regressed against fine root biomass or net primary production to determine what variables were most useful in predicting their dynamics. There were no significant or consistent patterns for above- and belowground biomass accumulation or NPP change across the different climatic forest types and by soil order. Similarly, there were no consistent patterns of soil organic matter (SOM) accumulation by climatic forest type but SOM varied significantly by soil order—the chemistry of the soil was more important in determining the amount of organic matter accumulation than climate. Soil orders which were high in aluminum, iron, and clay (e.g. Ultisols, Oxisols) had high total living and dead organic matter accumulations-especially in the cold temperate zone and in the tropics. Climatic variables and nutrient storage pools (i.e. in the forest floor) successfully predicted fine root NPP but not fine root biomass which was better predicted by nutrients in litterfall. The importance of grouping information by species based on their adaptive strategies for water and nutrient-use is suggested by the data. Some species groups did not appear to be sensitive to large changes in either climatic or nutrient variables while for others these variables explained a large proportion of the variation in fine root biomass and/or NPP. 相似文献
20.
Marie Arnaud Stefan Krause Richard J. Norby Thuong Huyen Dang Nezha Acil Nicholas Kettridge Vincent Gauci Sami Ullah 《Global Change Biology》2023,29(12):3256-3270
Mangroves are among the most carbon-dense ecosystems worldwide. Most of the carbon in mangroves is found belowground, and root production might be an important control of carbon accumulation, but has been rarely quantified and understood at the global scale. Here, we determined the global mangrove root production rate and its controls using a systematic review and a recently formalised, spatially explicit mangrove typology framework based on geomorphological settings. We found that global mangrove root production averaged ~770 ± 202 g of dry biomass m−2 year−1 globally, which is much higher than previously reported and close to the root production of the most productive tropical forests. Geomorphological settings exerted marked control over root production together with air temperature and precipitation (r2 ≈ 30%, p < .001). Our review shows that individual global changes (e.g. warming, eutrophication, drought) have antagonist effects on root production, but they have rarely been studied in combination. Based on this newly established root production rate, root-derived carbon might account for most of the total carbon buried in mangroves, and 19 Tg C lost in mangroves each year (e.g. as CO2). Inclusion of root production measurements in understudied geomorphological settings (i.e. deltas), regions (Indonesia, South America and Africa) and soil depth (>40 cm), as well as the creation of a mangrove root trait database will push forward our understanding of the global mangrove carbon cycle for now and the future. Overall, this review presents a comprehensive analysis of root production in mangroves, and highlights the central role of root production in the global mangrove carbon budget. 相似文献