Status: 

Completed

Title

Wood to Soil 0-10 cm data and Wood to Soil 10-20 cm data to detect the imprint of decaying logs (30-80 cm diameter) from two hurricane cohorts (Hugo, 1989, and Georges, 1998)
Summary

Short name: 

LUQMetadata189

Data set ID: 

189

Abstract: 

Many trees fell during Hurricanes Hugo (1989) and Georges (1998) in Puerto Rico. A debris removal experiment suggested that coarse woody hurricane debris slowed canopy recovery by fueling microbial nitrogen immobilization. We analyzed C, N, microbial biomass C and root length in paired soil samples taken under versus 20-50 cm away from large trunks of two species felled by Hugo and Georges three times during wet and dry seasons during the two years after Georges. Data on soil P and other nutrients have not yet been analyzed. Soil microbial biomass, C and N were higher under than near logs of both age cohorts. Frass from wood boring beetles may induce the early effects. Root length was greater under logs at 0-10 cm depth during the dry season, and away from logs in the wet season, but varied independently of microbial biomass. Thus decaying wood can provide resources exploited by tree roots. Percent soil C and N were significantly higher under than near logs in both the 0-10 and 10-20 cm samples. Microbial biomass C varied significantly among seasons at 0-10 cm depth but differences between positions (under vs away) were only suggestive. Surface soil on the upslope side of the logs had significantly more N and microbial biomass, likely from accumulation of leaf litter above the logs on steep slopes. This study shows that C and N accumulate significantly more in soil under than near decaying logs, even in logs that had only decayed for 7 months, and thus contributes to soil heterogeneity. Tree roots track and exploit resource and nutrient hotspots as they change locations between seasons, so the soil heterogeneity in soil fertility is important for forest productivity.

Dates
Date Range: 
1999-04-02 00:00:00 to 2001-01-11 00:00:00

Publication Date: 

2016-09-07 00:00:00
People

Additional Project roles: 

Name: Grizelle Gonzalez Role: Associated Researcher
Name: Dirk Winter Role: Associated Researcher
Name: Naomi Clum Role: Associated Researcher
Methodology

Methods: 

Sampling Design

Four areas (blocks) were selected for study, each with a pair of logs of the same species that were at least 30 cm diameter, with one felled by Hurricane Hugo and one felled by Hurricane Georges (Figure 1). The two species were Dacryodes excelsa Vahl. (Burseraceae) and Guarea guidonia (L.) Sleumer (Meliaceae); there were two replicate blocks of each tree species. Fallen trees were > 30-80 cm in diameter and at least half of the trunk was in contact with the ground (diameters are given in Table 1). Slopes varied from 20-40% (Table 1). All logs were decayed by white-rot basidiomycete fungi based on the bleached appearance and spongey-fibrous texture, though rates of decay varied among logs (see Table 1 for details). We used the four-class decay system proposed by Torres (1994) as the decay classification used for logs in temperate forests works poorly in the tropics where the bark can be retained on extensively decayed logs. At the time of this study, the youngest logs  (0.6-2 years-old) belonging to the Georges cohort were in decay classes I: no detectable decay, and  II: intact bark, sapwood partially soft, and few invading roots present. The older logs belonging to the Hugo cohort (9.5-11 years-old) were in decay II to class III: bark partially lost, sapwood soft, roots invading.

Soils in the blocks are weathered oxisol clay loams and clays (30-55% clay, 28-35% silt and 18-34% sand) in the Cristal and Coloso series [20], (Table 1). These clays have a high capacity for binding to phosphorus, but the upper horizon has high soil organic matter content and moderately slow permeability. The Coloso clay series has a higher cation exchange capacity than the Cristal clay loams (43 vs 29 CEC · C-1, respectively) [20]. Litter decomposes quickly and humus is usually absent between the forest floor litter and the mineral soil [4], as is typical of mull soils. Leaf litter accumulates on the upslope side of debris dams on slopes > 25% [21], resulting in higher soil carbon above than below permanent debris dams [22].

Location

Figure 1. Section of the El Verde Research Area in the Luquillo Experimental Forest of Puerto Rico where this study was conducted, showing the four blocks, each with a pair of logs belonging to two different hurricane cohorts (Hurricane Hugo in 1989 and Hurricane Georges in 1998). The first letter of the log code refers to the hurricane (G for Georges and H for Hugo) while the number refers to the block. Logs in two of the blocks were Dacryodes excelsa while the logs in the other two blocks were Guarea guidonia. Direction of stream flow in the Quebrada Prieta and Quebrada Sonadora is indicated by arrows. The logs are not shown to scale.

Table 1. Location of study blocks and their soil types in the El Verde Research Area of the Luquillo Experimental Forest.

Location

Block

Latitude, longitude

Soil type

Q. Sonadora watershed

1

18°19'24"N, 65°49'03"W

Cristal clay-clay loam

Q. Prieta watershed in LFDP cells 02.09 & 07.10

2

18°19''30.7"N, 65°48'56.6"W; 18°19'31"N, 65°49'02"W

Cristal clay-clay loam

Q. Sonadora watershed

3

18°19'24"N, 65°49'04"W

Cristal clay-clay loam

Q. Prieta watershed in LFDP cells 10.15 & 10.16

4

18°19'37"N, 65°49'00"W

18°19'27"N, 65°49'00"W

Coloso clay

Soil Sampling

Volumetric soil cores (8 x 8 cm) were extracted to 10 cm depth using a two-part aluminum corer as shown in Figure 2. Soil cores were extracted from under logs by digging an approach trench and driving the rectangular corer in horizontally (Figure 2). Each core from under a log was spatially and temporally paired with a core extracted vertically and located 20-50 cm from the first core and away from the log. These are hence referred to as ‘under’ and ‘away’ positions. On each sample date, one pair of cores was extracted from each log on the uphill side of the hill slope, and a second pair was extracted on the downhill side of the same log (Figure 2).

Figure 2.  A rectangular, 2-part soil corer was driven into the soil horizontally from the end of an approach trench to obtain volumetric soil samples from 0-10 cm depth under logs. Corer halves were offset by 2 cm or was used twice (0-8 and 8-10 cm) to obtain soil to 10 cm depth. Paired samples taken away from the logs were extracted vertically and located 20-50 cm away from the under-log core. Two pairs of cores were extracted on each date, one pair on the uphill side and the other on the downhill side of the log. Paired sample locations were randomly selected on each side of the log except for avoiding previously cored areas and large rocks. Soil samples from the 10-20 cm depth were extracted from the bottom of the first core holes using a punch corer.

Logs Characteristics

Table 2.  Characteristics of logs and that were used in this study. The label is comprised of the first letter of the hurricane that felled the tree, followed by the block number. Tree species were Guarea guidonia (Meliaceae) and Dacryodes excelsa (Burseraceae) but tree species were found to be similar and were not part of the model. Decay class was rated based on description of the logs were selected for study according to the classification of Torres (1994). Decay rate was classified 18-27 years after Hurricane Georges and Hugo, respectively:  slow – retaining some bark, diameter loss less than 5 cm; moderate – no bark remaining, diameter loss more than 5 cm but wood remaining; fast – either in the form of a mound of humus invaded by roots or no visible remains). Slope (%) was measured where the logs were located.

Location

Label

Hurricane

Tree Species

Diam. (cm)

Decay class

Decay rate

Slope

(%)

Q. Sonadora

H.1

Hugo 1989

G. guidonia

35-55

2

Slow

28

Q. Sonadora

G.1

Georges 1998

G. guidonia

38-80

1

Slow

35

Q. Prieta, LFDP cell 02.09

H.2

Hugo 1989

D. excelsa

35-52

3

Fast

35

Q. Prieta, LFDP cell 07.10

G.2

Georges 1998

D. excelsa

30-35

2

Fast

40

Q. Sonadora

H.3

Hugo 1989

D. excelsa

30-43

2

Moderate

20

Q. Sonadora

G.3

Georges 1998

D. excelsa

30-55

1

Slow

40

LFDP cell 10.16

H.4

Hugo 1989

G. guidonia

39-53

3

Fast

25

LFDP cell 10.15

G.4

Georges 1998

G. guidonia

45-70

2

Fast

25

Sampling Times

There were three sampling times: April to early May 1999 (dry season); January 2000 (late wet season) and September 2000 (mid-wet season). These times corresponded to 0.6, 1.4 and 2 years after Hurricane Georges, and 9.5, 10.4 and 11 years after Hurricane Hugo, respectively. Samples in the same block were collected on the same day, and all samples for a particular time were collected within a 12 day period.

Soil Nitrogen and Carbon Content

Soil samples were weighed, hand-sorted to seperate soil, roots and rocks; the roots and rocks were then weighed. A 15-20 g subsample was weighed into an aluminum pan, oven dried at 40° C and re-weighed to determine percent soil moisture. The soil was air dried and stored, then oven dried at 65° C. Total percent soil C and N were determined at the United States Forest Service (USFS) International Institute of Tropical Forestry laboratory using a LECO-2000 CNS analyzer [23] following the procedure of Vitousek and Matson [24]. Two samples of fresh bark beetle frass were also collected from different logs and analyzed for C and N using the CNS analyzer. We were unable to analyze the ammonium and nitrate we had extracted with KCl from fresh soils because of hurricane damage to facilities and infrastructure caused by Hurricane Georges.

Roots

Roots were separated into coarse (> 2 mm diameter) and fine (up to 2 mm diameter) from the 0-10 cm depth core samples, weighed and cut into ca. 1 cm long pieces. The decision to estimate root length was made after the first core (G.1) was processed, so those data are missing. Estimates of root lengths were made from three weighed subsamples per sample using the line-intercept method of Newmann [25]. Total root length was estimated by multiplying the mean root length per g of roots by the total weight of the roots. Analyses were made on total root length (fine plus coarse) as coarse roots were negligible.

Soil Microbial Biomass C

Soil microbial biomass C was estimated using the chloroform fumigation-incubation method [16]. Soil moisture was adjusted if less than 55% of field capacity in two 30-40 g subsamples the day after collection. One of the subsamples from each sample was fumigated with chloroform under vacuum, reinoculated with soil and incubated for 10 days in air-tight jars with NaOH for trapping the CO2 respired; the unfumigated control was also incubated with a CO2 trap. After 10 days, the amount of CO2 trapped in the NaOH solution was determined by titration with HCl using phenylthaline indicator dye. CO2 in the NaOH stock solution was also determined using titration, and the amount subtracted from the total in the incubation traps. Respired CO2 in the controls was subtracted from that in the fumigated samples according to the formula in Jenkins and Powlson [16].

Statistical Analyses

The design was a repeated measures nested randomized complete block. Dependent variables (soil C, soil N, microbial biomass C and total root length at 0-10 cm depth) were analyzed separately using a Repeated Measures Analysis; the 10-20 cm depth was only sampled twice for C and N, so those data were analyzed separately as a repeated measures nested randomized complete block. The independent variables (fixed effects in the models) were hurricane, position (under versus away from logs), hillslope direction (uphill or downhill), and time after Hurricane Georges (0.6, 1.4 and 2 years). Random effects of logs were nested within hurricanes. Block 1 was omitted from the root length analysis because of missing data for log G.1. All statistical analyses were performed using SAS Institute (version 9.3, [26]) software for a generalized linear mixed model using the pseudo-likelihood estimation technique via PROC GLIMMIX. In all analyses either the normal or lognormal distribution and an identity link function best fit the data. For N and roots at 0-10 cm, we had to add the groups=hillslope and groups=position option, respectively to adjust for heterogeneity of variance. In all cases the correlation between the repeated time was best fit by the unstructured covariance structure. Model selection was based on fit statistics using HQIC (see Table 3 in Results). All models used the Identity Link Function, and all possible interactions were included. No differences were found between tree species, so they were treated as replicates in all the analyses.

Additional information: 

REFERENCES :  

  • Jenkinson, D.S.; Powlson, D.S. The effects of biocidal treatments on metabolism in soil – V. A method for measuring soil biomass. Soil Biol. Biochem. 1976, 8, 209–213.
  • Lin, Q.; Brookes, P.C. An evaluation of the substrate-induced respiration method. Soil Biology and Biochemistry 1999, 31, 1969–1983.
  • Brown, S.; Lugo, A.E.; Silander, S.; Liegel, L. Research history and opportunities in the Luquillo Experimental Forest. United States Forest Service, General Technical Report, 1983, SO–44, Washington, DC, USA.
  • Torres, J.A. Wood decomposition of Cyrilla racemiflora in a tropical montane forest. Biotropica 1994, 26, 124–140.
  • Soil Survey Staff. Order 1 Soil survey of the Luquillo Long-Term Ecological Research Grid, Puerto Rico. United States Department of Agriculture, National Resources Conservation Service, Lincoln, NE, USA. 1995.
  • Lodge, D.J.; Asbury, C.E. Basidiomycetes reduce export of organic matter from forest slopes.  Mycologia 1988, 80, 888–890.  
  • Shanley, J.B.; Lodge, D.J.; Krabbenhoft, D.P.; Olson, M.L.; McDowell, W.H. New and old mercury fluxes from mercury amendments to Puerto Rico soil columns. Presented by Shanley at the American Geophysical Union Fall 2008 Meetings; 2008 December 15-19; San Francisco, California. American Geophysical Union. http://adsabs.harvard.edu/abs/2008AGUFM.B13C0457S (accessed August 17, 2009).
  • Tabatabai, M.A.; Bremmer, J.M. Automated instruments for determination of total carbon, nitrogen, and sulfur in soils by combustion techniques. In Soil Analysis, Modern Instruments Techniques; Marcel Dekker, Inc.: New York, NY, USA, 1991; pp. 261–286.
  • Vitousek, P.M.; Matson, P.A. Mechanisms of nitrogen retention in forest ecosystems: A field experiment. Science. 1984, 225, 51–52.
  • Newmann, E.I. A method of estimating the total length of root in a sample. Journal of Applied Ecology. 1966, 3, 139–145.
  • SAS Institute Inc., SAS/STAT® 9.3 User’s Guide. Cary, NC, USA. 2011.

SAMPLE LOCATION :  IITF Chemistry Laboratory. Not stored N/A.

STORAGE SITES (of data files): Currently at Sabana Field Research Station, Mycology. Will be transferred to IITF permanent file storage

Status: 

Completed

Time Period: 

Short-Term