Main Experiment: Seed addition experiment Site A (VIPs) – abiotic predictor variables

Usage Rights

This data is Free within projects.

BEF-China: SP11

Dataset Abstract

While diversity-invasibility relationships have often been addressed in experimental grassland communities, experimental approaches in forests are less common, especially in species-rich subtropical regions. Forest ecosystems feature higher complexity than grassland ecosystems, since they are composed by different vertical layers covering a high level of horizontal heterogeneity.
In the context of the Main Experiment with diversity levels from 1 to 24, we established a seed addition experiment with groups of native and exotic herbaceous species. In this early-successional forest system, seed mixtures for both groups were created with high and low functional diversity, sown into subplots along the tree diversity gradient of and harvested after one vegetation period.

Dataset Design

The seed addition experiment was established on Site A for analyzing the impact of tree diversity on herb layer invasibility and finished with harvest in October 2010. The seed addition experiment was conducted within 32 plots representing the full tree diversity gradient at Site A. These selected 32 plots included the tree diversity levels one (n = 16), two (n = 8), four (n = 4) eight (n = 2), 16 (n =1) and 24 (n = 1). Within the northern five rows of each plot, six subplots (2 m × 2 m) containing four trees, respectively, were randomly selected and established in March 2010. Thus, the seed addition was based on a total of 189 (32 × 6) subplots, each experiencing a neighbourhood tree diversity ranging from one to four (1, 2, 4). Within each subplot, seeds were added to a core area of 1 m² in the centre and surrounded by four target tree individuals, whereas the adjacent area served as a buffer zone The six subplots per plot were assigned to different seed addition treatments. Seed addition was applied by using five different seed mixtures, which were composed by six different species each. The species are annuals, bi-annuals or perennials and represent typical species of ruderal, disturbed sites like clear-cut forest areas.
Two seed mixtures were composed by native species (N) or exotic species (E) only. Within each of the groups of native and exotic species, one seed mixture was composed by functionally dissimilar species (N high and E high) and a second mixture by functionally similar species (N low and E low). A fifth seed mixture was composed by three exotic and three native species (EN) and a sixth subplot per plot received no seed addition and served as an internal control. In April 2010, each seed addition subplot received a total of 2400 seeds per m², i.e. 400 seeds per each species were sown into the subplot’s core area. Measurements of exposition and inclination were conducted in April 2010 for each subplot. Relative light conditions for each subplot were recorded in April and August 2010.

Spatial Extent

Main experiment, Site A, no shrub VIPs
29°08'-29°11'N
117°90'-117°93'E

Temporal Extent

Initial seed addition was performed in April 2010

Taxonomic Extent

The following herb species were used for seed addition: Ageratum conyzoides, Amaranthus spinosus, Bidens frondosa, Chenopodium ambrosioides, Conyza canadensis, Erigeron annuus, Gynura crepidioides, Oenothera biennis, Solidago canadensis, Artemisia lavandulaefolia, Artemisia anomala, Bidens biternata, Chenopodium album, Corchoropsis tomentosa, Lactuca formosana, Rumex japonicus, Siegesbeckia glabrescens, Solanum nigrum

Data Analysis

relative light conditions, inclination, exposition; for details see data group description.

Data columns available in the raw data part of this dataset

PTAG
Research plots on the main experiment have a "p" in front of their IDs and then a 6 digit code: Plots in the main sites A and B are named according to their position in the original spreadsheet, in which they were designed. They consist of 6 digits: _1st digit_: Site (1:A, 2:B), _digit 2and3_: southwards row: as in spreadsheets the rows are named from the top to the bottom; _digit 4 and 5_: westward column: as in the original spreadsheet, but the letters are converted to numbers (A=01, B=02); _6th digit_: indicator, if the plot has been shifted a quarter mu. Example: "p205260": "p" means that this is a plot that is specified. "2" means, that we are at site B. Now the coordinates of the south - west corner: "0526". Since "e" is the fifth letter of the alphabet, this is Plot E26. The last digit "0" means that this plot was not moved by a quarter of a Mu, as some sites in Site A. The 6th digit can also indicate the subplot within the plot. "5", "6", "7", "8" indicate the northwest, northeast, southeast, and southwest quarter plot respectively.
Data group: BEF research plot name
Keywords: VIP plots
Values
p103320
p105340
p105310
p106330
p106210
plot
plot
Data group: Helper
Values
E31
F21
C32
E34
F33
treatment
seed addition treatment; Datagroup description: seed addition treatment for each subplot: C-Control with no seed addition; E-high- seed addition of six exotic species which are functionally dissimilar;E-low- seed addition of six exotic species which are functionally similar;N-high- seed addition of six native species which are functionally dissimilar;N-low- seed addition of six native species which are functionally similar;EN-seed addition of three native and three exotic species
Data group: Treatment
Keywords: VIP plots, Main Experiment, Site A
Values
C
E_low
N_high
E_high
EN
treatment2
seed addition treatment; Datagroup description: category treatment: c-Control with no seed addition: n- seed addition of native species; e- seed addition of exotic species; en- seed addition of exotic and native species
Data group: Treatment
Keywords: VIP plots, Main Experiment, Site A
Values
c
en
e
n
treatment3
seed addition treatment; Datagroup description: category treatment: SA- Plots with ssed addition; NSA- Plots with no seed addition
Data group: Treatment
Keywords: VIP plots, Main Experiment, Site A
Values
NSA
SA
tree_diversity
tree diversity
Data group: Taxonomic biodiversity
Keywords: diversity treatment
Values
1
16
2
4
24
neighbourhood_tree_diversity
tree diversity; Datagroup description: neighbourhood tree diversity of the subplots; for Plots with tree diversity 4-24, the neighbourhood tree diversity is 4;
Data group: Neighbourhood diverstiy
Keywords: competitive neighbourhood, Diversity level
Values
4
2
1
date
date; Datagroup description: Exposition and inclination were measured from 2010-03-01 till 2010-03-20; light conditions in April were measured from 2010-04-25 till 2010-05-05; light conditions in August were measured from 2010-08-17 till 2010-08-26
Data group: Date time information
Keywords: date
Values
2010-04-10
exposition
topography, aspect in which the respective plot is facing, given as a category
Data group: Aspect Categories
Keywords: exposition, topography
Values
NW
N
NE
E
0
inclination
topography; Datagroup description: inclination of each subplot in degree
Unit: degree
Data group: Inclination
Keywords: inclination
Values
14
12
13
11
15
light_april_above
relative light condition (PAR)
Unit: percent
Data group: Solar radiation
Keywords: solar radiation
Values
0.9006857413100023
0.8567829342206904
0.8597523816870446
0.9064040132142421
0.9214413875598086
light_april_ground
relative light condition (PAR); Datagroup description: ground level of each subplot, 5 measuring points were recorded and put in relation to a control value (measured at a height of above 2 m) in April 2010
Unit: percent
Data group: Solar radiation
Keywords: solar radiation
Values
0.3047092469018112
0.23247799856091214
0.2317484051036683
0.27314886552296624
0.12718688421218569
light_august_above
relative light condition (PAR); Datagroup description: at 0.5 m height of each subplot, 5 measuring points were recorded and put in relation to a control value (measured at a height of above 2 m) in August 2010
Unit: percent
Data group: Solar radiation
Keywords: solar radiation
Values
0.08847970832740766
0.07766705373165841
0.034232737881967554
0.08883564693810382
0.033166354833863675
light_august_ground
relative light condition (PAR); Datagroup description: ground level each subplot, 5 measuring points were recorded and put in relation to a control value (measured at a height of above 2 m) in August 2010
Unit: percent
Data group: Solar radiation
Keywords: solar radiation
Values
0.007392476238844953
0.00878055478244735
0.0030185983039282575
0.01274094501718213
0.015639908307434593