Recovery Of Canopy Research Articles

The influence of postfire recovery and environmental conditions on boreal vegetation

AbstractClimate change is increasing the frequency and extent of fires in the boreal biome of North America. These changes can alter the recovery of both canopy and understory vegetation. There is uncertainty about plant and lichen recovery patterns following fire, and how they are mediated by environmental conditions. Here, we aim to address these knowledge gaps by studying patterns of postfire vegetation recovery at the community and individual species level over the first 100+ years following fire. Data from vegetation surveys collected from 581 plots in the Northwest Territories, Canada, ranging from 1 to 275 years postfire, were used to assess the influence of time after fire and local environmental conditions on plant community composition and to model trends in the relative abundance of several common plant and lichen species. Time after fire significantly influenced vegetation community composition and interacted with local environmental conditions, particularly soil moisture. Soil moisture individually (in the absence of interactions) was the most commonly significant variable in plant and lichen recovery models. Patterns of postfire recovery varied greatly among species. Our results provide novel information on plant community recovery after fire and highlight the importance of soil moisture to local vegetation patterns. They will aid northern communities and land managers to anticipate the impacts of increased fire activity on both local vegetation and the wildlife that relies on it.

Short-term recovery of soil and pine tree canopy after late prescribed burning in a semi-arid landscape

Climate change worsening due to global warming and progressive abandonment in rural areas mean that wildfires are increasing in extent and severity terms, and are one of the major disturbances in the Mediterranean Basin. To mitigate these disturbances, preventive management tools need to be used. Fire employment is being implemented, known as prescribed burnings, as forestry actions to change vegetation lines both vertically and horizontally to eliminate forest fuel load continuity. This study aimed to know the ecological effects of late prescribed burning treatments under mixed trees. Prescribed burns were carried out in October 2019 in the municipality of Ayna, Albacete (SE Spain). To assess the short-term (12-month) fire impact on soil, we measured soil respiration with a CO2 flow chamber and analyzed soil physico-chemical properties. We also used minidisc infiltrometers to analyze soil repellency and soil hydraulic conductivity over a 1-year monitoring period. In addition, we evaluated the effects on tree strata by performing chemical nature analyses of fallen needles in Pinus pinaster after prescribed burning. According to our initial hypotheses, the results did not show significant changes in any parameter evaluated during the study period. However, some variables were affected in the first 3 months, needlefall and in microbiological activity, such as variations in soil physico-chemical properties, which can be due to long dry seasons combined with prescribed burning. This study attempts to observe and make known the effects that low-intensity prescribed burning has on soil and needlefall, which are relevant for updating forest management tools.

Regeneration of Metrosideros polymorpha forests in Hawaii after landscape‐level canopy dieback

AbstractQuestions(a) Have Metrosideros polymorpha trees become re‐established in Hawaiian forests previously impacted by canopy dieback in the 1970s? (b) Has canopy dieback expanded since the 1970s? (c) Can spatial patterns from this dieback be correlated with habitat factors to model future dieback in this area?Study SiteAn 83,603 ha study area on the eastern slopes of Mauna Loa and Mauna Kea volcanoes on the island of Hawaii, USA.MethodsWe analyzed very‐high‐resolution imagery to assess status of Metrosideros polymorpha forests across the eastern side of the island of Hawaii. We generated 1,170 virtual vegetation plots with a 100‐m radius; 541 plots in areas mapped in 1977 with trees dead or mostly defoliated (dieback), and 629 plots in adjacent wet forest habitat, previously mapped as non‐dieback condition. In each plot we estimated the frequency of M. polymorpha trees that were dead or mostly defoliated, and the frequency of trees with healthy crowns. These results were combined with habitat data to produce a spatial model depicting probability of canopy dieback within the study area.ResultsSeventy‐nine percent of plots mapped in 1977 in dieback condition recovered their canopy and were now considered in non‐dieback condition. Ninety‐one percent of plots in previous non‐dieback areas were found to still have a healthy M. polymorpha canopy in 2015. A spatial model allowed us to identify areas within the study area with high, medium, and low probability of experiencing this same type of canopy dieback in the future.ConclusionsMost former dieback areas mapped within the study area in 1977 now show recovery of the tree canopy through growth of new cohorts of young M. polymorpha trees. This suggests these forest communities are resilient to this type of canopy loss and tree death so long as other factors do not disrupt the natural regeneration process.

Mid- and long-term effects of wildfire and debris flows on stream ecosystem metabolism

Wildfire is an important and prevalent agent of disturbance in vegetated landscapes across much of the Earth’s surface, including forested watersheds in the arid western USA. Between 1992 and 2003, >40% of the watersheds in the upper reaches of the Boise River watershed in central Idaho burned. The purpose of our study was to investigate the legacy effects of wildfire on stream ecosystems by analyzing the relationship between wildfire and resulting debris flows and their joint effects on stream ecosystem metabolism in 31 streams. The watersheds of ∼½ of these streams burned within the last 11 y, and some of these burned watersheds also experienced large-scale debris flows 1 y postfire. Streams with burned watersheds recovered quickly, and estimates of photosynthetically active radiation, gross primary production, and ecosystem respiration were indistinguishable from those in streams draining unburned watersheds. However, streams that experienced debris flows after their watersheds burned were remarkably different. They exhibited higher production and incident light and lower ecosystem respiration. Debris flows resulted in nearly complete removal of streamside vegetation, slowed recovery of the riparian canopy, and altered stream ecosystem metabolism. Our results suggest a synergistic interaction between wildfire and associated geomorphological processes whereby debris flows delay succession of stream ecosystems, possibly resulting in altered recovery trajectories, communities, and foodweb interactions.

The response of bats (Mammalia: Chiroptera) to an incidental fire on a gallery forest at a Neotropical savanna

Fire is a common and natural event in Cerrado that can influence the composition of trees and mammals and change the entire conditions of the environment. This study was developed in a gallery forest of Distrito Federal - Brazil. Bat samplings were conducted for a total of six nights after a fire that happened on the gallery forest. Three samplings were conducted: one day, three months and seven months after fire. A total of nine mist nets (12 m x 3 m) were opened from 7pm to 1am. Captured bats were measured and identified to species. Shannon index measured the species diversity of bats in the gallery forest over time. A rarefaction curve was made to assess the estimated bat richness in each of the samplings and a chi-square test was used to check whether there have been changes on bat abundances over time. A total of 46 bats from 8 different species and one family were captured. The most abundant species was Sturnira lilium. Species diversity and abundance increased over time and there was a gradual accumulation of species and specimens indicating that the succession and recovery of the forest occurs due to a temporal addition of specimens and species in the assemblage and not as punctual occurrences. Probably, this recovery pattern reflects a gradual increase in the availability of resources and recovery of the forest canopy, progressively offering more shelter and food for the bat assemblage.

Recovery of Vegetation Canopy After Severe Fire in 2000 at the Black Hills National Forest, South Dakota, USA

Abstract: Forest fires often result in varying degrees of canopy loss in forested landscapes. The subsequent trajectory of vegetation canopy recovery is important for ecosystem processes because the canopy controls photosynthesis and evapotranspiration. The loss and recovery of a canopy is often measured by leaf area index (LAI) and other vegetation indices that are related to canopy photosynthetic capacity. In this study we used time series imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor onboard the Terra satellite over the period of 2000–2009 to track the recovery of the vegetation canopy after fire. The Black Hills National Forest, South Dakota, USA experienced an extensive wildfire starting on August 24, 2000 that burned a total area of 33 785 ha, most of which was ponderosa pine forest. The MODIS data show that canopy photosynthetic capacity, as measured by LAI, recovered within 3 years (2001–2003). This recovery was attributed to rapid emergence of understory grass spec...

Chilling damage in a changing climate in coastal landscapes of the subtropical zone: a case study from south Florida

AbstractFreeze events significantly influence landscape structure and community composition along subtropical coastlines. This is particularly true in south Florida, where such disturbances have historically contributed to patch diversity within the mangrove forest, and have played a part in limiting its inland transgression. With projected increases in mean global temperatures, such instances are likely to become much less frequent in the region, contributing to a reduction in heterogeneity within the mangrove forest itself. To understand the process more clearly, we explored the dynamics of a Dwarf mangrove forest following two chilling events that produced freeze‐like symptoms, i.e., leaf browning, desiccation, and mortality, and interpreted the resulting changes within the context of current winter temperatures and projected future scenarios. Structural effects from a 1996 chilling event were dramatic, with mortality and tissue damage concentrated among individuals comprising the Dwarf forest's low canopy. This disturbance promoted understory plant development and provided an opportunity for Laguncularia racemosa to share dominance with Rhizophora mangle. Mortality due to the less severe 2001 event was greatest in the understory, probably because recovery of the protective canopy following the earlier freeze was still incomplete. Stand dynamics were static over the same period in nearby unimpacted sites. The probability of reaching temperatures as low as those recorded at a nearby meteorological station (≤3 °C) under several warming scenarios was simulated by applying 1° incremental temperature increases to a model developed from a 42‐year temperature record. According to the model, the frequency of similar chilling events decreased from once every 1.9 years at present to once every 3.4 and 32.5 years with 1 and 4 °C warming, respectively. The large decrease in the frequency of these events would eliminate an important mechanism that maintains Dwarf forest structure, and promotes compositional diversity.

OsteoMacs maintain the endosteal hematopoietic stem cell niche and participate in mobilization

OsteoMacs are tissue macrophages that reside within bone lining tissues. OsteoMacs enhance osteoblast function in vitro and maintain osteoblast bone forming surface in vivo. Given the endosteum is a preferred niche for hematopoietic stem cells (HSC), we investigated whether OsteoMacs participate in HSC mobilization induced by granulocyte colony-stimulating factor (G-CSF). Immunohistochemistry (IHC) using the F4/80 antibody demonstrated that mobilization induced by G-CSF resulted in a sharp reduction in the number of F4/80+ OsteoMacs within the endosteal niche from days 2–6 post initiation of G-CSF administration. At day 2, clustering of F4/80+ cells in the central marrow and in particular around endothelial sinuses was evident. In contract, localization and maintenance of OsteoMacs within the periosteum was unaffected by G-CSF administration. Flow cytometry demonstrated increased numbers of F4/80+ macrophages in blood from days 1–6, indicating egress of macrophages from bone marrow to blood. Static and dynamic histomorphemtry and IHC for osteocalcin expression demonstrated a concomitant significant reduction in endosteal osteoblast number and function as well as osteoid. Notably, the kinetics of OsteoMac loss strikingly parallels, if not precedes, that of endosteal osteoblasts loss and mobilization of HSC to blood. In contrast, osteoclast numbers were not significantly altered by G-CSF administration and treatment with the bisphosphonate zoledronate increased HSC mobilization in response to G-CSF. F4/80+ macrophages repopulation of bone marrow and endosteal surfaces initiated at day 8, 2 days after cessation of G-CSF administration, and was quickly followed at day 10 by recovery of OsteoMac canopy covering cubiodal osteoblast-like cells. Prior experimentation has indicated that mobilization induced by G-CSF acts through an intermediary G-CSF receptor expressing myeloid population. Finally, we demonstrate a pivotal role of macrophages in maintaining endosteal HSC niches in transgenic MAFIA mice in which macrophages can be specifically deleted in vivo using AP20187. At day 5 following macrophages deletion, we observed a collapse in the number of osteoblasts lining the endosteum and robust mobilization of HSC in peripheral blood and spleen. Given macrophages can express the G-CSF receptor and the observations reported here, we propose that G-CSF induces HSC mobilization through OsteoMac-directed collapse of the endosteal HSC niches.

Slow recovery from disturbance: a 20 year study of Ascophyllum canopy clearances

We describe an experiment where Ascophyllym nodosum was removed from two 1 x 1 m plots in south-western Iceland in August 1985. The plots were studied regularly until 2005. Recovery of the Ascophyllum canopy took 7–8 years. The understorey algae in one of the plots consisted mostly of extensive growth of Cladophora rupestris, which died within a year of Ascophyllum clearance. No Cladophora had reappeared by 2005, although it was healthy and abundant in control plots throughout the study period. Thus even after 20 years the community had not recovered from disturbance.

Estimates of tree canopy loss as a result of Cyclone Monica, in the Magela Creek catchment northern Australia

Abstract Severe tropical Cyclone Monica impacted the coast of northern Australia in April 2006 with estimated maximum wind gusts of 360 km h−1. It rapidly moved inland losing intensity and passed over the town of Jabiru as a category 2 system, with maximum wind gusts recorded at 135 km h−1. The cyclone had a significant impact on the landscapes within the Alligator Rivers Region and significant windthrow of trees occurred. This paper describes the level of impact that category 2 level winds had on tree canopy loss 10 days after cyclone and then again 1 year later. Recovery was assessed using multispectral satellite imagery in sub‐catchments of the Magela Creek catchments. A non‐linear relationship was fitted between a modified vegetation index (derived from Landsat TM5 satellite data) and percentage tree canopy cover (measured from very high resolution QuickBird satellite data). The results of the non‐linear relationship, used to estimate percentage canopy cover, indicate that 10 days after cyclone, there was significant disturbance to tree canopy. However, data 1 year after cyclone show that recovery of canopy across the studied catchments varied between 8% and 19% of the percentage canopy cover that remained after the initial impact of the cyclone. Further analysis in the three sub‐catchments using Geographical Information System showed that proportionally, riparian zones and inundated areas in each of the sub‐catchments suffered greater loss of tree canopy cover compared with upland areas.

Disturbance and reef topography maintain high local diversity in Ecklonia radiata kelp forests

Disturbance of competitive‐dominant plant and algae canopies often lead to increased diversity of the assemblage. Kelp forests, particularly those of temperate Western Australia, are habitats with high alpha diversity. This study investigated the roles of broad‐scale canopy loss and local scale reef topography on structuring the kelp‐dominated macroalgal forests in Western Australia. Eighteen 314 m2 circular areas were cleared of their Ecklonia radiata canopy and eighteen controls were established across three locations. The patterns of macroalgal recolonisation in replicate clearances were observed over a 34 month period. Macroalgal species richness initially increased after canopy removal with a turf of filamentous and foliose macroalgae dominating cleared areas for up to seven months. A dense Sargassum canopy dominated cleared areas from 11 to 22 months. By 34 months, partial recovery of the kelp canopy into cleared areas had occurred. Some cleared areas did not follow this trajectory but remained dominated by turfing, foliose and filamentous algae. As kelp canopies developed, the initial high species diversity declined but still remained elevated relative to undisturbed controls, even after 34 months. More complex reef topography was associated with greater variability in the algal assemblage between replicate quadrats suggesting colonising algae had a greater choice of microhabitats available to them on topographically complex reefs. Shading by canopies of either Sargassum spp. and E. radiata are proposed to highly influence the abundance of algae through competitive exclusion that is relaxed by disturbance of the canopy. Disturbance of the canopy in E. radiata kelp forests created a mosaic of different patch types (turf, Sargassum‐dominated, kelp‐dominated). These patch types were both transient and stable over the 34 months of this study, and are a potential contemporary process that maintains high species diversity in temperate kelp‐dominated reefs.

Survival of juvenile Ecklonia radiata sporophytes after canopy loss

The understorey beneath a canopy of the kelp Ecklonia radiata often contains juvenile sporophytes of the same species. When canopy disturbance occurs, these juvenile sporophytes are exposed to new environmental conditions. If these juvenile sporophytes survive these new conditions, then they become a ready source of kelps to rapidly form a new canopy. This study investigated the potential of pre-existing juvenile sporophytes of E. radiata to survive post-disturbance conditions and contribute to the rapid formation of a new canopy. The potential of canopy recovery by recruitment of kelp from zoospores was also investigated. These processes were studied at different times during the summer and on reefs ranging in topographic complexity from simple, flat reefs to highly complex, rugose reefs. By tagging juvenile sporophytes after the adult kelp canopy was removed and monitoring them through time, it was demonstrated that most juveniles (> 50%) survived the change in conditions after canopy loss, with some juveniles going on to become members of a new canopy. Approximately 6–47% of tagged sporophytes died within 3–4 days after canopy removal possibly due to excessive photoinhibition and photostress as demonstrated by changes in photosynthetic performance (decreased alpha values) of juveniles. The potential contribution of juvenile sporophytes to the rapid formation of a new canopy appears to be dependent on the timing of canopy removal with late summer–autumn canopy loss favouring faster recovery. Topographically complex reefs had less short-term (7 days) survival of juvenile sporophytes than topographically simple reefs; however this difference was not carried through to the long-term (6 months) abundance of adult kelp in experimental clearings, which was greater on topographically complex reefs. Clearly, juvenile sporophytes in arrested development under existing canopies of the small kelp E. radiata are important for the rapid recovery of the kelp canopy once adults are lost through physical disturbance.

Cumulative effects of fire on a tussock pampa grassland

Abstract. In order to test for cumulative effects of fire on Paspalum quadrifarium‐dominated grasslands (‘pajonal’), we analysed the impact of single and repeated fires on the community structure and post‐fire recovery of canopy after a final, simultaneous fire event. Nine plots were defined within a homogeneous pajonal stand, and treatments of low (LF), medium (MF) and high frequency (HF) of fire were defined by the application of one, two or four cold‐season burns, respectively, along a 6‐yr period. Both burned and unburned plots were exposed to grazing by cattle during the summer following the first and the third years of that period. High cattle preference for burned sites conditioned fire temperature and vegetation responses to the following burning events. Cumulative effects between successive burning events were observed for the cover of basal area of the dominant and other sprouting species, the cover and thickness of the litter layer, the seed bank size of the principal recruiter species, and the floristic composition. While light interception by the canopy was positively related to fire frequency during the early growth season, further growth of P. quadrifarium determined a greater light interception in LF than in MF and HF. These patterns of light interception were associated with a faster occupation of the inter‐tussock areas by opportunistic species in plots subjected to frequent fires (HF and MF) than in plots with low fire frequency (LF), and a more lasting regrowth of P. quadrifarium in the LF plot than in the HF ones. High fire frequencies reduced the dominance of P. quadrifarium. Percent of species classified as subordinated graminoids or forbs did not vary among treatments. However, the abundance of different forb species was differentially favoured by contrasting frequencies of fire, describing some coarse relationships between their specific responses and their dispersal strategies.

Cumulative effects of fire on a tussock pampa grassland

Abstract In order to test for cumulative effects of fire on Paspalum quadrifarium-dominated grasslands (‘pajonal’), we analysed the impact of single and repeated fires on the community structure and post-fire recovery of canopy after a final, simultaneous fire event. Nine plots were defined within a homogeneous pajonal stand, and treatments of low (LF), medium (MF) and high frequency (HF) of fire were defined by the application of one, two or four cold-season burns, respectively, along a 6-yr period. Both burned and unburned plots were exposed to grazing by cattle during the summer following the first and the third years of that period. High cattle preference for burned sites conditioned fire temperature and vegetation responses to the following burning events. Cumulative effects between successive burning events were observed for the cover of basal area of the dominant and other sprouting species, the cover and thickness of the litter layer, the seed bank size of the principal recruiter species, and the ...

328 Long-term Impact of Cold Damage on Physiological Performance and Yield Efficiency in Red Raspberry

Two test sites pairing perennially cold-damaged portions of fields vs. controls for a 3rd year were assessed. Winter 1997-1998 was very mild and produced less winter injury than the previous winters. We evaluated continued recovery of the raspberry canopy and cane productivity. In contrast to the last 2 years, the previously cold-damaged plots did not show higher levels of cane dieback, percentage of cane dieback, number of dead or dormant buds per cane, and percentage of dead buds at either site. Very few secondary laterals were produced at either site, which supports previous observations that raspberry compensates for winter injury with increased production of secondary laterals. For the first time, the damaged plots actually produced higher yields mainly through a significantly increased berry number per cane at both sites. Floricane leaves in the damaged plots showed higher photosynthetic rates at the green fruit stage and after harvest at site 2. Cane size was similar across sites, although the previously cold-damaged plants had higher berry numbers per lateral. It seems the newly recovered plants in the previously damaged plots had a renewed vigor, working harder to achieve a higher yield. No differences between treatments was detected in leaf nitrogen for a third year, suggesting this may not be a factor in winter injury here. A high population of weevils was observed at one injured site, suggesting a possible interaction with cold damage.

Diminished greenness of tomato leaves exposed to ozone and post-exposure recovery of greenness.

The response to ozone (O(3)) of greenness, in terms of estimated total chlorophyll concentration (Chl), of leaves at three plant canopy levels was studied in tomato (Lycopersicon esculentum Mill.) over a 10-day period following O(3) exposure. Plants of the cultivars 'New Yorker' and 'Tiny Tim' were grown at 25/15 degrees or 30/15 degrees day/night temperatures in growth chambers and exposed to 0.00, 0.08, 0.16 or 0.24 microl litre(-1) O(3) for 7 h day(-1) for four consecutive days in controlled environment exposure chambers. Measurement of Chl in the top, middle and bottom canopy leaves with a calibrated SPAD-501 leaf greenness meter indicated that the growth temperatures tested did not significantly influence the response of Chl to O(3). Ozone-induced loss of Chl was widespread in the entire foliage canopy, including foliage which did not demonstrate visible injury. In both cultvars the Chl in leaves at all three canopy levels declined as a function of increasing O(3) concentration when measured 2, 4, 6, 8 and 10 days after the exposure period. However, the slopes for leaves in the top and middle canopies decreased with increasing time after exposure. An analysis of this apparent Chl recovery indicated that leaves in the top and middle canopies exposed to 0.16 and 0.24 microl litre(-1) increased in greenness at a rapid rate after the marked initial decline associated with O(3) treatment. The apparent recovery of the top canopy may have reflected the growth of new leaves and their inclusion in the measurements, but this was not the case for the middle canopy for which the same leaves were measured throughout the post-exposure period. Bottom canopy leaves did not demonstrate significant recovery of Chl.

Vegetation Damage Caused by Phytophthora cinnamomi on Disturbed Sites in Temperate Rain-Forest in Western Tasmania

Phytophthora cinnamomi has been isolated directly from 558 diseased plants among 39 species including 1 fern, 4 graminoids and 34 woody dicotyledons, all indigenous to the cool temperate rainforest of Tasmania. Pathogenicity has been proved by greenhouse tests (20 spp.) and by field inoculation at two localities (19 spp.). Of the 142 species in the rainforest flora, 69 were rated for the susceptibility of field populations; 30% were highly susceptible and less than 5% highly resistant. High proportions of susceptible species occurred in Epacridaceae, Eucryphiaceae and Proteaceae. All 93 isolates tested were the common A2 mating type. The fungus was constantly associated with disease at 47 survey localities. Diseased plants were widely but patchily distributed along exposed road and track edges within unburned rainforest and in recently burned rainforest. The fungus was not recovered from samples taken beneath healthy roadside regeneration, beneath undisturbed rainforest or above 900 m elevation. The disease has the characteristics of attack by a recent invader and appears to be dependent upon disturbance which elevates soil temperatures above 15°C, the lower threshold for infection by P. cinnamomi. Post-fire recovery of forest canopy is expected to allow re-establishment from external sources of seed of those susceptible species which are both efficiently dispersed and tolerant of shade. Species lacking such characteristics are at risk of local elimination but no single rainforest species appears to be under threat of extinction from this pathogen.

Ericameria austrotexanaand Associated Range Forage Responses to Herbicides

Canopy cover of false broomweed (Ericameria austrotexanaM.C. Johnston) on the Rio Grande Plains of Texas was initially reduced by 96% by glyphosate [N-(phosphonomethyl)glycine] applied at 2.2 kg/ha in the spring. Acceptable control of this shrub with glyphosate lasted at least 4 yr. Glyphosate severely reduced basal cover of perennial grasses during the year of treatment, but grasses completely recovered within 2 yr after treatment. Standing forage crop increased by an average of 83%, compared to untreated areas, and livestock carrying capacity increased from 1 animal unit (AU)/13 ha to 1 AU/7 ha. Picloram (4-amino-3,5,6-trichloropicolinic acid), paraquat (1,1′-dimethyl-4,4′-bipyridinium ion), and paraquat plus atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] applied in the spring were less effective than glyphosate. Canopy reductions of false broomweed 6 months after applications of 2.2 kg/ha of picloram, paraquat, or paraquat plus atrazine were equivalent to that from 1.1 kg/ha of glyphosate, and control with these herbicides was usually restricted to the season of application. Dicamba (3,6-dichloro-o-anisic acid), 2,4-D-[(2,4-dichlorophenoxy)acetic acid], atrazine, and 2,4-D plus atrazine were not effective when applied in the spring or fall. Time required for recovery of false broomweed canopy apparently varied with amounts of rainfall received after herbicide application.