DOI: 10.5061/dryad.dncjsxkx4
title: Decline pattern of C. fargesii and seed traits

description: Widespread tree defoliation and mortality rates have increased
 considerably in recent decades. We investigated the decline pattern of
 Castanopsis fargesii and examined the effects on conspecific seedling
 regeneration. This dataset contains the basic characteristics and tree
 vigor level data of 617 C. fargesii individuals (H &gt;1.3m,
 identified in nine plots in a national nature reserve in Chongqing in
 Southwestern China), and the seed traits data of the seeds produced by
 decline adult trees and non-decline adult trees.
description: In September 2013, we established a 0.5 ha (50 m × 100 m) core
 monitoring plot and eight 30 m × 30 m sampling plots that were dominated
 by <i>C. fargesii</i> to monitor the long-term dynamics of
 declining forests on Jinyun Mountain (29°49′N, 106°20′E), a national
 nature reserve in Chongqing in Southwestern China. In September 2013, we
 examined the decline patterns of <i>C. fargesii</i> adult
 trees within the core monitoring plot and the eight sampling plots. Within
 each plot, we tagged and measured diameter-at-breast height (DBH) and tree
 height (H) of all woody trees ≥ 1.3 m tall. For C. <i>fargesii
 </i>adult trees (H ≥ 8 m; DBH ≥ 10 cm) and saplings (1.3 - 8 m) in
 all plots, we determined the vigor levels based on the percentage of crown
 defoliation, using a semi-quantitative scale. Six tree vigor levels were
 defined for this study: L0: dead tree; L1: 81-100% crown defoliation; L2:
 61-80% crown defoliation; L3: 41-60% crown defoliation; L4: 21-40% crown
 defoliation; and L5: 0-20% crown defoliation. We classified L0-L1 as a
 high level of decline, L2-L3 as an intermediate level of decline, and
 L4-L5 as non-decline. In September 2018, we again determined the vigor
 levels of all of the adult trees that we had marked in 2013 to evaluate
 their decline trends. We investigated seed production
 and seed traits of the 30 selected <i>C. fargesii </i>adult
 trees using seed traps. The seed traps were made of a funnel of
 polyethylene cloth (1 mm mesh), with a receiving area of 0.5 m2 (1 m × 0.5
 m) and a height of 1 m above the ground. Considering the terrain, crown
 shape, and vine coverage, we set up two or three seed traps in each
 subplot at a distance of 1.5 m from each adult tree (72 seed traps in
 total, Fig. 1). We fully considered the distance between two selected
 adult trees to ensure that a certain distance (&gt; 3 m) was present
 between the seed traps and the adjacent adult tree canopies. In
 addition,<i> C. fargesii</i> seeds are about 0.5 g, and the
 horizontal dispersal distance is very close by seed rain. Therefore, the
 risk that seeds in the seed traps had come from adjacent adult trees was
 very low. The seed traps were made of a funnel of
 polyethylene cloth (1 mm mesh), with a receiving area of 0.5
 m<sup>2</sup> (1 m × 0.5 m) and a height of 1 m above the
 ground. Considering the terrain, crown shape, and vine coverage, we set up
 two or three seed traps in each subplot at a distance of 1.5 m from each
 adult tree (72 seed traps in total). We fully considered the distance
 between two selected adult trees to ensure that a certain distance
 (&gt; 3 m) was present between the seed traps and the adjacent adult
 tree canopies. In addition, <i>C. fargesii</i> seeds are about
 0.5 g, and the horizontal dispersal distance is very close by seed rain.
 Therefore, the risk that seeds in the seed traps had come from adjacent
 adult trees was very low. We combined the mature seeds
 of each adult tree collected every week. Among the combined seeds, we
 randomly selected 30 intact mature seeds from each of the 11 non-declining
 adult trees and 10 intermediate declining adult trees to measure their
 seed traits, including fresh weight (seed mass), nutritional (starch), and
 defensive (cellulose and tannin) material properties. We did not measure
 the seed traits of high declining adult trees, because the collected seeds
 were too few to sample. Starch content was estimated using the optical
 rotation method following the national standard (NY/T11-1985) for cereals.
 Cellulose content was estimated using the acid and alkali washing method
 following the national standard (NY/T13-1986) for cereals. The tannic acid
 content was determined using the spectrophotometry method following the
 national standard (GB/T15686-2008) for sorghum.