LUQ LTER DATA SETS DOCUMENTATION FORM

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DATA SET IDENTIFIER: Canopy Trimming Experiment (CTE) Litter decomposition and Connectivity basket data

PROJECT DESCRIPTION: This long-term experiment will increase the frequency of simulated hurricane effects above background levels to once every six years. The experiment will determine effects of repeated disturbance of the forest canopy and increased detrital inputs to the forest floor on germination, growth, survival, nutrient cycling, soil conditions, and trophic structure. Climate change models predict increased frequency and intensity of Caribbean hurricanes (Emmanuel 1987, Goldenberg et al. 2001), and our goal is to evaluate predictions regarding the effects of an increased rate of hurricane disturbance on tabonuco forest (Sanford et al. 1991). The experiment also is designed to decouple the effects of canopy disturbance (e.g. , light levels, temperature, moisture, etc. ) from those of increased detrital inputs on rates of detrital processing and resultant community and ecosystem processes. Manipulations and measurements of detrital processing, SOM, and soil properties associated with SOM will continue for at least three more funding periods (until 2024). In the short-term, we will use faunal manipulations nested within the canopy trimming experiment to measure the strength of interactions between autotrophic and detrital food webs in the context of hurricane-like disturbance. These results will be directed specifically at parameterizing the Trophic Interaction Model. This experiment also will provide a physical and intellectual focal point for the project participants. The Canopy Trimming Experiment has two parts: 1) a forest canopy manipulation with measurements of coupled changes in microclimate, structure, and biota and their associated impacts on ecosystem processes, and 2) specific manipulations of the biota that assess the importance of components of the food web.

CTE Litter Basket Decomposition Experiment: The objective was to determine how green litter deposition and canopy opening associated with a hurricane independently and together affect rates of decomposition of pre-existing litter and green hurricane litter. In addition, changes in litter quality and quantity and changes in microenvironment were hypothesized to bring about changes in abundance of white-rot litter basidiomycete fungi and their activity in translocating nutrients between litter cohorts. Fungal connectivity was determined between litter cohorts that were demarcated with screens. Analysis of nutrient concentrations and content will determine which litter cohorts became nutrient sources and which ones became sinks following canopy opening and/or deposition of green litter. Litter moisture, fungal connectivity to the pre-weighed senesced leaf cohort and leaf mass loss were all slowest in the treatment with canopy trimming and debris removal and fastest in the closed canopy with added debris. Addition of green leaf litter ameliorated the environment in the senesced litter layer below and buffered it from effects of canopy opening, resulting in similar fungal connectivity and mass loss in control and trimmed canopy plus debris plots.

LTER CORE AREAS: (Annotate all that apply) (See online list)

organic matter accumulation

inorganic nutrients

populations

LEF LTER 1 RESEARCH TOPIC: Annotate all that apply (See online list)

Recovery-Nut. Storage

Recovery-Litter Breakdown

We define a data file as a component of a data set. A data set can have only one data file or more. Basically, different data files have different data structures or format.
DATA SET FILES (SUBSETS):
NOTE: The decomposition data for this data set will be published soon - May 8, 2009

Data File No.	Data File Identifier	On-Line Filename	Starting Date	Periodicity of sample	End Period
1	Mass Loss & Fungal Connectivity	CTElitterbasketConnect.txt	July 5, 2005	1-3 month interval	January 22, 2007
2	Mass of Natural Litter Cohorts	CTE_NaturalLitterCohorts.txt	July 5, 2005	1-3 month interval	January 22, 2007

RESEARCH LOCATION: Block A: 30+ m West of western edge of Big Grid, on North and South side of Prieta stream, near Vogt old plots. Block B: 30+ m South of Big Grid, all plots along Oxcart Trail. Block C: 30+ m West of SE corner of Big Grid.

INVESTIGATORS:

SOURCE OF FUNDING (SPONSOR): LTER funding to make the CTE plots, materials & supplies, tech time. USDA Forest Service (FPL, IITF) for scientist’s time.

In addition to obtaining mass and percent moisture of litter cohorts, the extent of fungal connections between litter cohorts was quantified. Fungal connections between partly decomposed and fresh leaf litter have been shown to be important in importation of phosphorus (the most limiting major nutrient in decomposition of tabonuco forest litter) into the freshly fallen leaves in order to rapidly build fungal biomass and associated acceleration of decomposition (Lodge 1993, 1996). The thickest of these fungal colonization & translocation organs (rhizomorphs, cords and hyphal strands) are primarily basidiomycete fungi, which have an almost unique capacity to cause white-rot by breaking down lignin in low-quality litter. A few white-rot basidiomycetes produce finer connections comprised of diffuse wefts of hyphae (e.g., Marasmius leoninus and related species), but the majority may represent ascomycetes and water molds that lack enzyme systems for breaking down lignin. White-rot basidiomycetes were shown in separate experiments to accelerate rates of decomposition of tabonuco leaves (Dacryodes excelsa) by 15% to 20% (Santana et al. 2005; Lodge et al. 2008), so any changes in fungal connectivity by basidiomycete fungi in response to the treatments should be related to nutrient exchanges between litter cohorts and changes in rates of mass loss.

Litterbaskets are used to study decomposition and nutrient cycling questions, and are often a better for understanding interactions between different litter cohorts than are leaf decomposition bags. We know from previous work here and elsewhere that: 1) basidiomycete fungi rapidly colonize freshly fallen litter (within the first 3 weeks of litterfall) from partly decomposed litter on the forest floor using rhizomorphs and cords (Lodge & Asbury 1988); 2) these fungal root-like structures transport nutrients from the old food base in order to build their biomass in the freshly fallen leaves, and are capable of tripling the phosphorus content in a senesced tabonuco leaf as indicated using radioactive phosphorus tracer in microcosm experiments (Lodge 1993; 1996); and 3) basidiomycete colonization accelerates leaf decomposition in the LEF (Lodge et al. 2008). Fungal translocation of nutrients is probably responsible for the increase in total CONTENT of N and P in leaf litter above 100% in El Verde (as in Zou et al.) and elsewhere in the tropics within 3-6 weeks of leaf fall (see Lodge 1993). In contrast, temperate forest floor litter is not usually colonized by basidiomycete fungi from the forest floor until 9-15 months after litterfall. Translocation of phosphorus into tropical litter with low phosphorus concentrations likely contributes to accelerated rates of leaf decomposition associated with basidiomycete colonization in tabonuco forest (Lodge et al. 2008), but the enzymatic capacity of basidiomycete to degrade lignin is a contributing factor (Santana et al. 2005).

Previous research in temperate forests shows a positive effect of increased litter depth on colonization by basidiomycete fungi. Unpublished data of Lodge & Asbury showed that drying of the litter layer reduced or eliminated basdiomycete colonization, while Lodge & Cantrell (1995) showed disappearance of some basidiomycete colonies in canopy gaps on ridges at El Verde after hurricane Hugo, or replacement of drought-sensitive strong nutrient translocators (i.e., Collybia johnstonii) with more drought tolerant species that translocated less P32. There were no previous data on effects of litter depth on basidiomycete fungi from tropical forests. We knew from studies after Hurricane Georges that 1. forest floor mass in secondary forest returned to pre-hurricane levels in about a year (Ostertag, Silver & Scatena?), but we did not know whether this was due to accelerated decomposition or reduced litter inputs after the storm. Thus, it was not really clear what mechanisms were involved in control of forest floor decomposition following hurricane disturbance.

This litterbasket decomposition experiment was designed to mimic as closely as possible post-hurricane conditions in order to follow mass loss and nutrient content of specific litter cohorts. To this end, a layer of SURFACE AIR-DRIED tabonuco leaves was placed between two screens on top of the existing forest floor layer in the litterbaskets (on the ground). In debris-addition plots, green leaves of Dacryodes, Manilkara and Sloanea IN HURRICANE AMOUNTS (as determined in Lodge et al. 1991) were added on top of the senesced litter layer screen after the canopy manipulations were completed in the CTE plots. Additional cohorts of litterfall were demarcated using screens added to remaining baskets when these were harvested ca. quarterly.

So far, we know that 1) canopy opening inhibited fungal connectivity between litter cohorts (mostly basidiomycete fungi, but the highest counts may be from diffuse hyphal connections by ascomycetes and water molds); 2) addition of green litter buffered the layers below from drying, mostly compensating for the effects of canopy opening; 3) fungal connectivity to the weighed layer of senesced tabonuco leaves was positively and significantly correlated with rates of leaf decomposition; 4) litter decomposition rates were higher than in dried leaf litter in a litterbag experiment in the CTE (González et al, unpublished), as in previous unpublished comparisons of dried versus undried litter; 5) but despite this, forest floor mass had not returned to pre-hurricane levels 1.5 years after CTE initiation. The data of Cantrell and Ortíz (lterdb165) on microbial composition in the litter cohorts from these baskets used methods that cannot distinguish basidiomycetes from other fungi. The results, however, suggest that colonization by basidiomycetes colonize accelerates the rate of early leaf decomposition and changes the trajectory of community succession. Nutrient analyses to determine if increases followed by decreases in inorganic nutrient pools, especially phosphorus, are associated with changes in patterns of fungal connectivity between the litter cohorts, and whether cohorts with low connectivity at the beginning have net losses rather than net gains in N & P stores.

DATA SET METHODS: Litter decomposition baskets were used to determine the effect of simulated hurricane (green) leaf litter on decomposition of the underlying litter layers. Open-mesh plastic baskets 35 x 25 cm were modified by cutting out the solid bottom and replacing it with 2mm mesh woven nylon mesh. The experiment was set up between July 1 and 10, 2005. The existing non-woody forest floor was carefully transferred to the bottom of the basket, and a 1mm mesh plastic window screen was placed over the forest floor layer. Because the application of treatments to the CTE plots in the three blocks (B, C, and then A, see Table 1) took a long time, the amount and condition of the forest floor was highly variable in the first week of July 2005 when the basket decomposition experiment was set up. Therefore, a pre-weighed cohort consisting of a near monolayer of weighed, air-dried freshly fallen (senesced) leaves was added immediately above the forest floor screen marker. All baskets received 10 g air-dried freshly fallen leaves of Manilkara bidentata and Dacryodes excelsa in a near mono-layer covering 75%-85% of the forest floor cap screen, followed by an additional cap screen. The mixture of freshly fallen leaves in Block A was 6 g Dacryodes excelsa and 4 g Manilkara bidentata. The mixture of freshly fallen leaves in Blocks B and C was 4 g Dacryodes excelsa and 6 g Manilkara bidentata. The two treatments that received canopy debris (canopy trimming plus debris, and no trimming plus debris) received 100 g fresh weight of green leaves trimmed from the understory in the following proportions: 25 g Dacryodes excelsa, 33 g Sloanea berteriana, and 42 g Manilkara bidentata for all blocks. There were three to four 100 g fresh weight subsamples of green leaves for determination of fresh weight to oven-dried weight ratios, and initial nutrient concentrations of the green leaves. The green leaf layer was covered by a cap screen.

There were five litter decomposition subplots in each plot (see Table 1), and six litter decomposition baskets in each subplot. However, the canopy trimming and debris removal treatment only had baskets in four of the five litter decomposition subplots in blocks B and C because some baskets recycled from a previous experiment fell apart in transit.  One basket per subplot was collected at the following intervals: 7 weeks, 14 weeks, 28 weeks, 40.5 weeks, 53 weeks and 80 weeks. Data for 80 weeks were unreliable as there was much soil contamination from earthworm casts after one year, especially in the canopy removal treatments, and the mass-loss data are for oven-dried weights and not ash-free dry weights. The baskets collected at 80 weeks were originally intended as ‘spares’ to be harvested in the event of a hurricane strike in order to quantify the amount of hurricane debris. At the 14 week, 28 and week harvests, an additional ‘cap’ screen was placed in the remaining baskets to separate litterfall cohorts. Harvested baskets were returned to the station, and the number of hyphal strand connections between litter cohorts were determined. Litter from each cohort were weighed, a 2 g subsample for microbial analyses was removed, and the remainder was oven dried at 60C and reweighed to determine percent moisture and mass. Contents were ground and analyzed for total N and P to determine patterns of nutrient immobilization, mineralization and translocation.

Table 1. Treatments by block and plot number, subplot locations of litter baskets, and dates of canopy trimming applied to appropriate plots (NA is not applicable – trimming not applied).

REFERENCES:

Lodge, D.J.  1993.  Nutrient cycling by fungi in wet tropical forests.  In S. Isaac, J.C. Frankland, R. Watling, A.J.S. Whalley, Eds.  Aspects of Tropical Mycology. BMS Symposium Series 19:37-57. Cambridge Univ. Press.

Lodge, D.J.  Microorganisms. 1996. In  D.P. Regan and R.B. Waide, Eds.  The Food Web of a Tropical Forest. Univ. of Chicago Press. pp. 53-108.

Lodge, D.J. & S. Cantrell.  1995.  Fungal communities in wet tropical forests: variation in time and space.  Canadian Journal of Botany.  (suppl. 1): S1391-S1398.

Lodge DJ, McDowell WH, Macy J, Ward SK, Leisso R, Claudio Campos K, Kühnert K. 2008. Distribution and role of mat-forming saprobic basidiomycetes in a tropical forest. IN: Boddy L; Frankland JC, eds. Ecology of saprobic Basidiomycetes. Amsterdam: Academic Press, Elsevier LTD, 195-208.

Lodge DJ, Scatena FN, Asbury CE, Sánchez MJ.  1991.  Fine litterfall and related nutrient inputs resulting from Hurricane Hugo in Subtropical Wet and Lower Montane Rain Forests of Puerto Rico.  Biotropica 23: 364-372.

Ostertag, R., FN Scatena, WL Silver. 2003. Forest floor decomposition following hurricane litter inputs in several Puerto Rican forest. Ecosystems 6: 261-273.

Santana M, Lodge DJ, Lebow P. 2005. Relationship of Host Recurrence in Fungi to Rates of Tropical Leaf Decomposition. Pedobiologia 49: 549-564.

CROSS-REFERENCES (other data sets related to this one): LTERDBAS#159:  Canopy Trimming Experiment (CTE) Litter Basket Microbial diversity DNA data; LTERDBAS#157: Canopy Trimming Experiment (CTE) litterbag invertebrate counts and weights data; LTERDBAS#160: Canopy Trimming Experiment (CTE) Microbial diversity Fatty Acid data; LTERDBAS#162: Canopy Trimming Experiment (CTE) Litterfall;

SAMPLE LOCATION: Sabana Field Resarch Station, The Module, Mycology; and Woodshop Dry Storage Room.

STORAGE SITES(of data files):electronic copies in LTER Data Manager’s office, Originals and electronic copies at Sabana Field Research Station, Mycology, Module

INVESTIGATOR'S ASSIGNED KEYWORDS: Fungi, basidiomycetes, leaf decomposition, mass loss, white-rot, nutrient translocation, hurricane disturbance, forest floor mass, carbon, phosphorus, nitrogen, litterfall cohorts

LEF LTER OFFICIAL KEYWORDS (See table): CTE blocks, SUBTROPICAL WET, CARBON, NITROGEN, PHOSPHORUS, DISTURBANCE, DECOMPOSITION, HURRICANE, LITTERFALL

PUBLICATIONS:
MEETING ABSTRACTS:
Cantrell, SA, García-Orta LM, Rivera-Figueroa F, Cruz C, González G, Zou X, Pett-Ridge J, Dubinsky E, Lodge DJ, Firestone M. 2006. “Microorganisms. Key players in ecosystem functions”. All-Scientists Long-Term Ecological Research Meeting, 19-23 Sept. 2006, Estes Park, Colorado.

Zimmerman J, Shiels A, Bloch C, Cantrell S. Crowl T, Cruz C, Garcia L, González G, Klawinski P, Lebrón L, Lodge DJ, McDowell W, Melendez-Colom E, Prather C, Ramirez A, Reese E, Richardson B, Richardson M, Rivera F, Schowalter T, Sharpe J, Silver W, Brokaw N.  2006.  “The Canopy Trimming Experiment at LUQ”. All-Scientists Long-Term Ecological Research Meeting, 19-23 Sept. 2006, Estes Park, Colorado.

THESIS: contains mass loss and % moisture data from this data set:
Ortíz-Hernández, M. 2008. Comunidades microbianas presentes en la hojarasca en diferentes estados de descomposición con o sin la abertura del dosel y la adición de detrito. Universidad del Turabo, Masters Thesis.

PEER-REVIEWED JOURNAL PAPER, SUBMITTED: contains %moisture data from this data set:
Richardson, B.A., M.J. Richardson and G. González. Submitted. Response of forest litter invertebrate communities to experimental canopy loss and detrital deposition in a tropical montane forest subject to hurricanes. Submitted to J. Animal Ecology April 2009.

DISSEMINATION:

RESTRICTED ___ UNRESTRICTED _X__

REASONS TO RESTRICT DATA IN THIS DATA SET BEYOND ITS TWO YEAR POLICY PERIOD*:

*WILL HAVE TO BE APPROVED BY AT LEAST ONE LUQ LTER PRINCIPAL INVESTIGATORS: N. Brokaw, J. ZIMMERMAN, A. LUGO

SITES DESCRIPTIONS: Block A: Elevation (340-360); aspect SW-facing; Location 30+ m West of western edge of Big Grid, on North and South side of Prieta stream, near Vogt old plots. Block B: Elevation (450-485); aspect W-SW facing; Location 30+ m South of Big Grid, all plots along Oxcart Trail. Block C: Elevation (435-480 m); aspect West-facing; Location 30+ m West of SE corner of Big Grid.

Geographical positional system (GPS) Coordinates for each location:

Location	Latitute	Longitute
EL VERDE RESEARCH AREA, LEF, MUN. RIO GRANDE	18.3	-65.8

The following table displays the x and y coordinates in Puerto Rico Planar Coordinates:

VARIABLES (ATTRIBUTES):

File Name or # above (all in which the variable appears)	all	all	all	all	1	2	2	all
AbbreviationAbbreviation(as it appears on the data file)	Block	Plot	Treatment applied to plot	Subplot	Date_Initial	Date_Initial	Date_Capped	Date_Final
NAME OF VARIABLE	Block identifier	Plot Identifier	Treatment given to Subplot	Subplot Identifier	Date pre-weighed leaves were placed in baskets	Date lower litter cohort screen was placed in basket	Date litter cohort was capped	Date litter basket was collected
DEFINITION OF VARIABLE	Name to a cluster of 4 similar plots in one of three locations, serving as replicates. No data are missing in the data file.	Name given to a 30m X 30m treatment plot within a Block. No data are missing in the data file.	Name to a cluster of 4 similar plots in one of three locations, serving as replicates. No data are missing in the data file.	Name given to a 4.7m X 4.7m of a plot within a block. No data are missing in the data file.	Date (in mm/dd/yyyy) the pre-weighed senesced (freshly fallen) and green leaves were placed in the baskets and began decomposing. No data are missing in the data file.	Date (in mm/dd/yyyy) the lower screen demarcating a particular litter cohort was placed in the basket. No data are missing in the data file.	The (in mm/dd/yyyy) date litter inputs to a cohort were stopped by placement of a cap screen. or basket was harvested. No data are missing in the data file.	Date when basket was collected from the field, fungal connections where counted and litter weight. Field is left blank when data are missing.
UNIT
PRECISION
RANGE OR LIST OF VALUES	A = West of western edge of Big Grid plot B = South of Big Grid C =  West of SE	1,. . . , 4	Control = no trimming and no detritus addition, No Trim + Debris = No trimming of canopy but detritus from a trim plot deposited in plot, Trim & clear = Canopy trimmed and detritus from trim removed from plot, Trim + Debris = Canopy	1,. . . , 16
DATA TYPE	alphabetic	integer	alphabetic	integer	datetime	datetime	datetime	datetime
MISSING DATA CODES

VARIABLES (ATTRIBUTES):

File Name or # above (all in which the variable appears)	all	all	all	all
AbbreviationAbbreviation(as it appears on the data file)	layer	#fungalConnectoLayerBelow	#fungalConnectoLayerAbove	%Moist_on_aWetWtBasis
NAME OF VARIABLE	Leaf or litter layer	Fungal connectivity to the litter cohort below	Fungal connectivity to the litter cohort above	Percent moisture in final field-wet sample
DEFINITION OF VARIABLE	Weighed, surface-dried leaves placed in the basket, unweighed natural forest floor or natural litterfall leaf cohorts, separated by screens.	Number of fungal rhizomorphs, hyphal strands or cords connecting litter layer to the cohort below, or if diffuse hyphae, then the number of 1x1 mm screen meshes penetrated by hyphae; if both types present these summed. . Field is left blank when data are missing.	Number of fungal rhizomorphs, hyphal strands or cords connecting litter layer to the cohort above, or if diffuse hyphae, then the number of 1x1 mm screen meshes penetrated by hyphae; if both types present these summed. . Field is left blank when data are missing.	percent moisture in field-wet sample calculated by the following formula: 100*[(Final Field Weight – weight of subsample removed for microbial analysis – Dry Weight)/(Final Field Weight – weight of subsample removed for microbial analysis]. . Field is left blank when data are missing.
UNIT
PRECISION
RANGE OR LIST OF VALUES	Floor, Senesced, Green New1, New2, New3,  New4
DATA TYPE	alphanumeric	integer	integer
MISSING DATA CODES

VARIABLES (ATTRIBUTES):

COMPUTATIONAL METHODS:

FOR DATA MANAGER USE ONLY

Rev. date of this form: 28 July 200/ 15 July  2001/June 9, 2003/March 16, 2004/12 April 2005/ 8 November 2005/ 16 January 2006