Total Leaf Fall Research Articles

Inter-tree variability of autumn leaf phenology of European beech (Fagus sylvatica) on a site in Ljubljana, Slovenia

Temporal variability of leaf senescence (autumn phenology) was observed in 2020 in 11 European beech (Fagus sylvatica) trees in Tivoli, Rožnik and Šišenski hrib Landscape Park in Ljubljana, Slovenia, and also observed for spring phenology in the same year. General leaf colouring, BBCH94, occurred between 19 and 24 October 2020, with lower inter-individual variability than that of leaf unfolding, BBCH11. The trees had active leaves (time between leaf unfolding and leaf colouring) between 177 and 199 days. In only three trees total leaf fall, BBCH97, occurred before 19 November 2020. Leaf colouring of the tree included in the long-term monitoring program of the Slovenian Environment Agency ARSO occurred on 24 October 2020. This is 7 days later than the 65-year average of the same tree/location and is ascribed to weather conditions. Investigation of tree tissues showed that the width of the last formed tree-ring in the wood varied between 0.39 and 9.61 mm and in the phloem between 0.09 and 0.26 mm, and that the tissues reflect the health condition of the trees.

Soil water dynamics and litter production in eucalypt and native vegetation in southeastern Brazil

High productivity of eucalypt plantations is the result of advances in research that have led to gradual improvements in intensive silvicultural technology. High productivity notwithstanding, eucalypt plantations remain the focus of environmental concerns. Our study aimed to compare the soil water regime, litter fall and nutrients dynamics either in a fragment of native forest or in an adjacent stand of growing eucalypt. We took field measurements during the first three years of eucalypt plantation in a sandy soil in the southeastern region of Brazil. Soil moisture and internal drainage were higher during the early stages of growth of the eucalypt stand, as compared with native vegetation. However, one and a half years after planting, available soil water was similar in both vegetations. Higher water availability under the eucalypt stand during the first year occurs because of silvicultural operations (soil preparation and weed control) and the small size of eucalypt trees; these factors increase water infiltration and decrease transpiration. Total leaf fall, over the study period, was similar for both ecosystems; however, differences were observed in the winter and early spring of 2010. The transfer of nutrients to soil by leaf fall was similar except for N and S, which was higher in native vegetation. Nitrogen concentration in the soil solution was higher in native vegetation, but K was higher under the eucalypt stand, mainly to a depth of up to 0.2 m.

Nutrient transfer by leaf litterfall during a sugar maple decline episode at Lake Clair watershed, Québec, Canada

In a declining sugar maple (SM) stand, we tested the hypothesis that an increasing relative abundance of American beech (AB) and yellow birch (YB) would improve litter quality by providing a higher proportion of litterfall richer in base cations and lower in acidity. From 1989 to 2006, SM leaf fall diminished from 59% (1,718 kg ha−1 year−1) to 36% (915 kg ha−1 year−1) of the total leaf fall biomass. Overall, the increase in AB and YB litterfall compensated for the SM decrease, resulting in constant annual leaf litterfall fluxes (2,803 kg ha−1 year−1) over the period studied. However, because the leaf litter for AB and YB had Ca and Mg concentrations 2–3 times higher than did SM, Ca and Mg concentrations and fluxes in leaf litterfall significantly increased between 1989 and 2006. Leaf litterfall of AB and YB also has a higher base/acid ratio than SM. Consequently, changes in forest composition following SM decline led to a clear improvement in litterfall quality in terms of base cations content and fluxes and acid–base properties.

Elaeagnus angustifolia Elevates Soil Inorganic Nitrogen Pools in Riparian Ecosystems

Elaeagnus angustifolia L., a nonnative N2-fixer, has established within riparian corridors of the interior western United States and is now the fourth most frequently occurring woody riparian plant in this region. We examined whether E. angustifolia alters pools and fluxes of soil inorganic N at eight sites dominated by Populus deltoides ssp. wislizeni along the Rio Grande in New Mexico over 2 years. E. angustifolia contributed a small fraction of total leaf fall ( 2%) of E. angustifolia senesced leaves. Soil inorganic N concentrations and potential rates of nitrification and net N mineralization varied across sites. E. angustifolia leaf fall explained 59% of the variation in soil inorganic N concentrations across years. This relationship suggests that inputs of N-rich leaf litter from E. angustifolia may increase N availability in riparian soils. We detected no relationship between E. angustifolia leaf fall and fluxes of soil inorganic N, whereas others have measured both stimulation and inhibition of soil N cycling by E. angustifolia. Greater abundance of N2-fixing species in riparian forests may augment growth of neighboring plants or increase N export to rivers. Given these possibilities, ecosystem studies and restoration projects should further examine the potential for E. angustifolia to affect N pools and fluxes along western North American rivers.

Litterfall in the hardwood forest of a minor alluvial-floodplain

Within mature deciduous forests, annual development of foliar biomass is a major component of aboveground net primary production and nutrient demand. As litterfall, this same foliage becomes a dominant annual transfer of biomass and nutrients to the detritus pathway. We report litterfall transfers of a mature bottomland hardwood forest in a minor alluvial-floodplain within the middle Coastal Plain physiographic province of central Louisiana, USA. Climate is humid subtropical. Floodplain forests of minor alluvial-streams may account for nearly half the remaining acreage of bottomland forests in the Southeastern USA and differ markedly from those of major alluvial-rivers and deep-water swamps. For a 3-year period, litterfall magnitude, components, leaf species, and timing were monitored by monthly collection of materials from litterfall collectors. Variations in litterfall transfers across 10 study-plots and their relationships to forest parameters are evaluated. Mean transfers of total litterfall, leaf fall, reproductive structures, fine wood, and other litterfall were 816, 512, 130, 98, and 76 g m −2 year −1, respectively. Quercus pagoda Raf., Q. nigra L., and Liquidambar styraciflua L. accounted for an average of 49% of annual leaf fall, with 11 tree species and canopy vines accounting for 94% of total annual leaf fall. A total of 38 species and genera contributed to total leaf fall. Variation in total litterfall and leaf fall transfers across the alluvial bottom were related to size of overstory trees and their species composition. Higher and more consistent mass transfers of reproductive structures were observed than previously reported for upland hardwood stands.

Litter flux in Kuala Selangor Nature Park mangrove forest, Malaysia

The amount of litter production, litter standing crop and export of leaf litter were studied in Kuala Selangor Nature Park mangrove forest, Malaysia. The rates of leaf fall, small branches, bracts, flowers, propagules and total litter varied from 1.63-3.07 g/m2/day, 0.08-0.38 g/m2/day, 0.13-0.39 g/m2/day, 0.01-0.23 g/m2/day, 0.03-2.29 g/m2/day and 2.31-4.46 g/m2/day respectively. Comparatively higher rate of total litter fall was observed during the drier months of July 02, July 03 and August 02; and propagules contributed 31.00 to 52.00% of the total litter fall during the dry season. Relatively higher rate of leaf litter production was observed during February 02 followed by March 03 (intermediate seasons). The rate of total litter production and leaf fall showed significant (F, p<0.05) negative correlations with rainfall and relative humidity while positive correlations were observed with temperature. The amount of small litter standing crop at different seasons varies from 63.45 to 104.59 g/m2 and comparatively higher amount of leaf litter and bract was recorded during the intermediate seasons while relatively higher amount of propagules was observed during the dry season. The export of leaf litter varied from 19.46 to 50.00 % of total leaf fall during the wet and dry months respectively.

The keystone role of leaf-removing crabs in mangrove forests of North Brazil

Principle factors which influence mangrove leaf litter turnover, in particular the role of leaf-removing crabs, were evaluated in a riverine mangrove site near Braganca (Para, North Brazil). Our special interest was focussed on the role of the leaf-removing crab Ucides cordatus. Leaf litter fluxes between the mangrove forest and the adjacent estuary were investigated by estimating the biomass and fate of leaf litter material and propagules. Vegetation is dominated by Rhizophora mangle, with Avicennia germinans trees, both up to 25 m high, found intermittently. During 1997, Rhizophora trees produced around 1.40 g DW m −2 d −1 of leave fall and 0.75 g DW m −2 d −1 of propagules. Leaf decomposition rates on the ground were about 0.06 g DW m −2 d −1 , irrespective of species, habitat or site exposure. This amount accounts for <3% of total leaf fall. Average leaf litter biomass present on the ground was 0.01 g DW m −2 d −1 . When the mangrove forest was flooded (on average 10 days per month) the quantity of leaf litter and propagules washed out with the spring tide was 10 and 17 times greater than during neap tide. Nevertheless, tidal export and decomposition together made up less than 39 percent of annual leaf litter fall. The bulk of the remaining amount is apparently removed by Ucides. Each crab consumed about 1.30 g DW of leaf litter material and propagules per day. Since the average density of these crabs was 1.38 crabs m −2 , it is proposed that Ucides is a keystone species in Bragantinian mangroves.

Litterfall dynamics and ecosystem recovery during forest development

A field study was conducted at the Hubbard Brook Experimental Forest (USA) to quantify changes in the mass, chemistry and timing of litterfall during stand development of the northern hardwood forest and to relate changes to other ecologically meaningful forest dynamics. Leaf fall on three contiguous watersheds, harvested 1, 15 and 66 years ago, was measured with litter traps from 1984 to 1988. Woodfall into the 15-year-old stand was monitored on permanent plots. During the first 17 years of forest development, fallen leaves and wood of Prunus pensylvanica accounted for 32–59% and more than 97%, respectively, of total mass litter inputs. In the older forest, Acer saccharum, Fagus grandifolia, and Betula alleghaniensis contributed 53%, 25%, and 21%, respectively, of the total leaf fall mass of the stand. Changes in the leaf mass of each species during forest development were the result of an increased number of leaves rather than increased mass per leaf. Leaves fell first in the oldest stand and last in the youngest stand. The nitrogen (N) content and non-structural carbohydrates of fallen leaves were highest in the youngest stand, but there was no overall trend in later stages of forest development. In 1985, leaves of all species in all stands had significantly reduced N contents (only 23–80% of N in leaves falling in 1984). In the oldest stand, this difference resulted in leaf fall N of 30.3 kg ha −1 (1984) and only 15.6 kg ha −1 (1985). Leaves of different species varied considerably in organic fractions but, with few exceptions, cellulose and lignin were significantly higher in 1985 than in 1984. The large difference between 1984 and 1985 in organic fractions and N suggests that leaf litter quality may vary greatly from year to year and may partially account for unbalanced nitrogen budgets. Large pulses of wood fell each year into the mid-aged stand (1151–1283 kg ha −1 year −1). This woodfall, high in lignin (28–31%) but low in nitrogen (0.1–0.2%), supplemented leaf fall and yielded total litterfall lignin: nitrogen ratios of 18.9 (1984) and 30.8 (1985). The timing of this deposition coincides with a transition to accretion of forest floor biomass from a protracted decline following disturbance. Apparently, the combined effects of high litterfall and low substrate quality lead to a sustained accumulation of the forest floor until a steady state is reached, about 50 years after disturbance.

Nitrogen and phosphorus cycling in relation to stand age of Ecucalyptus regnans F. Muell

The N and P contents of the litter layer and the return of these nutrients in litterfall were measured in seven stands of Mountain Ash (Eucalyptus regnans) ranging in age from 5 years to about 250 years. Both annual litterfall and nutrient return were correlated with stand basal area and were high compared with other productive eucalypt forests. In contrast, the fall of dead eucalypt leaves was constant with stand age, demonstrating that sites are fully occupied at an early age. Similarly, amounts of N and P in total leaf fall (overstorey plus understorey) were constant with stand age, except for low amounts in the stand aged 40 years where Acacia spp., important fixers of atmospheric N, were not prevalent. The decomposition constant (k) of organic matter in the litter layer decreased with stand age, from 0.31 year-1 at age 5 years to 0.23 year-1 at age 250 years. These constants also applied to N and P, indicating a tight coupling between organic matter decomposition and release of these nutrients from litter. The litter layer released about 30 kg ha-1 of N at age 5 years, and about 70 kg ha-1 at age 80 years. These results are discussed in relation to growth of Mountain Ash following fire, and the subsequent retention and accumulation of N during stand development.

Autumn Leaf Fall and Nutrient Return in an Old-Growth and a Second-Growth Forest in Eastern Kentucky

Autumn leaf fall was sampled in two watersheds, one containing an old-growth stand and the other a 35-yr-old second-growth stand of mixed mesophytic forest in eastern Kentucky Total leaf fall and its composition did not differ between the two watersheds and averaged 291 g/m2 Weighted average nutrient concentrations exhibited spatial variation, which paralleled a previously established soil fertility gradient Total nutrient return by autumn leaf fall was greatest on mid-slope sites of both watersheds, where soil pH and nutrient availability are greatest The combination of bulk nutrient return by leaf fall and of recognized variation in leaf decay rates suggests that the soil fertility gradient within each stand may be tied to internal nutrient cycling characteristics of the vegetation

Calcium, potassium and magnesium nutrition and their interactions in ‘Cox's Orange’ apple trees

Interactions between calcium (Ca), potassium (K) and magnesium (Mg) in apple tree nutrition were investigated in a pot experiment with ‘Cox's Orange’. Trees low in Ca supply were strongly dependent on Mg supply. Without Mg there was a very early and total leaf-fall. This led to a considerable yield response of Mg supply. During Ca deficiency, application of K enlarged the deficiency, resulting in a reduced K effect. Application of K reduced the Ca concentration in the leaves and Mg application depressed it further. This was not the case in the fruits, where K supply alone decreased the Ca concentration, while Mg supply, together with K, to some extent increased it. Spraying three times with MgSO 4·7H 2O, 1% or 2%, confirmed that fruit Ca is reduced by spray-applied Mg.

Chemical Defoliation of Cotton VII. Effectiveness of Adjuvants Under Several Specific Plant and Environmental Conditions1

SynopsisThe use of adjuvants with chemical defoliants increased the amount of leaf fall and rapidity of defoliation under limiting conditions such as wilted, toughened and inactive leaves, immature leaves and bolls, low temperatures, and conditions due to excessive applications of nitrogen. Under conditions considered favorable for defoliation, the use of adjuvants with chemical defoliants hastened leaf fall but no significant increase in total leaf fall was evident. The use of adjuvants with chemical defoliants did not retard defoliation.